首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2882850篇
  免费   218580篇
  国内免费   5457篇
耳鼻咽喉   38870篇
儿科学   95073篇
妇产科学   79959篇
基础医学   409185篇
口腔科学   85622篇
临床医学   258690篇
内科学   557491篇
皮肤病学   63673篇
神经病学   228471篇
特种医学   111953篇
外国民族医学   698篇
外科学   436979篇
综合类   70052篇
现状与发展   6篇
一般理论   1010篇
预防医学   220030篇
眼科学   68223篇
药学   214668篇
  9篇
中国医学   6365篇
肿瘤学   159860篇
  2018年   30246篇
  2017年   23291篇
  2016年   25696篇
  2015年   29433篇
  2014年   40860篇
  2013年   60996篇
  2012年   83648篇
  2011年   88185篇
  2010年   52254篇
  2009年   49141篇
  2008年   82979篇
  2007年   87949篇
  2006年   88848篇
  2005年   85607篇
  2004年   83540篇
  2003年   79775篇
  2002年   77415篇
  2001年   140781篇
  2000年   144839篇
  1999年   121238篇
  1998年   32797篇
  1997年   29207篇
  1996年   29152篇
  1995年   28149篇
  1994年   26200篇
  1993年   24377篇
  1992年   96071篇
  1991年   93325篇
  1990年   90482篇
  1989年   87281篇
  1988年   80413篇
  1987年   78833篇
  1986年   74910篇
  1985年   71888篇
  1984年   53274篇
  1983年   45753篇
  1982年   26353篇
  1981年   23577篇
  1979年   49371篇
  1978年   34044篇
  1977年   28940篇
  1976年   27159篇
  1975年   28756篇
  1974年   35076篇
  1973年   33714篇
  1972年   31139篇
  1971年   29217篇
  1970年   27013篇
  1969年   25303篇
  1968年   23303篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
BACKGROUND AND PURPOSE:Postprocedural dual-antiplatelet therapy is frequently withheld after emergent carotid stent placement during stroke thrombectomy. We aimed to assess whether antiplatelet regimen variations increase the risk of stent thrombosis beyond postprocedural day 1.MATERIALS AND METHODS:Retrospective review was undertaken of all consecutive thrombectomies for acute stroke with tandem lesions in the anterior circulation performed in a single comprehensive stroke center between January 9, 2011 and March 30, 2020. Patients were included if carotid stent patency was confirmed at day 1 postprocedure. The group of patients with continuous dual-antiplatelet therapy from day 1 was compared with the group of patients with absent/discontinued dual-antiplatelet therapy.RESULTS:Of a total of 109 tandem lesion thrombectomies, 96 patients had patent carotid stents at the end of the procedure. The early postprocedural stent thrombosis rate during the first 24 hours was 14/96 (14.5%). Of 82 patients with patent stents at day 1, in 28 (34.1%), dual-antiplatelet therapy was either not initiated at day 1 or was discontinued thereafter. After exclusion of cases without further controls of stent patency, there was no significant difference in the rate of subacute/late stent thrombosis between the 2 groups: 1/50 (2%) in patients with continuous dual-antiplatelet therapy versus 0/22 (0%) in patients with absent/discontinued dual-antiplatelet therapy (P = 1.000). In total, we observed 88 patient days without any antiplatelet treatment and 471 patient days with single antiplatelet treatment.CONCLUSIONS:Discontinuation of dual-antiplatelet therapy was not associated with an increased risk of stent thrombosis beyond postprocedural day 1. Further studies are warranted to better assess the additional benefit and optimal duration of dual-antiplatelet therapy after tandem lesion stroke thrombectomy.

In around 15% of endovascular procedures for anterior circulation stroke,1 there is a tight stenosis or occlusion of the cervical carotid artery in addition to the intracranial artery occlusion. The optimal endovascular management of tandem lesions has yet to be defined; however, there is mounting evidence2,3 that emergent stent placement in the carotid artery associated with at least 1 antiplatelet agent could lead to better recanalization rates and improved clinical outcomes. A more definitive answer should be provided by the Thrombectomy In TANdem lesions (TITAN) randomized multicenter trial,4 designed to assess the safety and efficacy of emergent internal carotid artery stent placement in tandem lesion thrombectomy. This study recently enrolled the first patient in early 2020.In patients undergoing emergent carotid stent placement, there is no consensus regarding the optimal periprocedural antiplatelet therapy. Many groups5,6 chose to avoid dual-antiplatelet therapy (DAPT) during the first 24 hours in an attempt to reduce the risk of hemorrhagic transformation. Conversely, less aggressive antiplatelet regimens might increase the risk of carotid stent thrombosis.Stent thrombosis was recently identified as a predictor of unfavorable clinical outcome.7,8 To date, available data regarding stent patency rates remain scarce. Most case series of endovascular management for tandem lesions5,9-11 do not report postprocedural stent patency, while some publications12-15 offer partial data for a subgroup of patients for whom carotid imaging controls were available. Reported rates of stent thrombosis ranged between 1.2% and 22.0%.6-8,12-14,16,17To date, no study has attempted to differentiate between early (first 24 hours) and subacute/late postprocedural stent thrombosis. During the first 24 hours, protection against stent thrombosis is conferred by antiplatelet agents administered during the procedure (periprocedural antiplatelets). Beyond 24 hours, the recommended antiplatelet regimen is DAPT for 4–12 weeks,9,17 but in reality, antiplatelets are often tailored in view of neurological and extra-neurological hemorrhagic events. It is currently unknown whether discontinuation of DAPT is associated with an increased risk of late stent thrombosis.Thus, we aimed to describe the variations in the postprocedural antiplatelet regimen in a large consecutive cohort of tandem lesion thrombectomies with emergent carotid artery stent placement and to assess whether discontinuation of DAPT was associated with an increased risk of carotid stent thrombosis.  相似文献   
62.
BACKGROUND AND PURPOSE:Transradial access for neurointerventional procedures has been proved a safer and more comfortable alternative to femoral artery access. We present our experience with transradial (distal radial/anatomic snuffbox and radial artery) access for treatment of intracranial aneurysms using all 3 FDA-approved flow diverters.MATERIALS AND METHODS:This was a high-volume, dual-center, retrospective analysis of each institution’s data base between June 2018 and June 2020 and a collection of all patients treated with flow diversion via transradial access. Patient demographic information and procedural and radiographic data were obtained.RESULTS:Seventy-four patients were identified (64 female patients) with a mean age of 57.5 years with a total of 86 aneurysms. Most aneurysms were located in the anterior circulation (93%) and within the intracranial ICA (67.4%). The mean aneurysm size was 5.5 mm. Flow diverters placed included the Pipeline Embolization Device (Flex) (PED, n = 65), the Surpass Streamline Flow Diverter (n = 8), and the Flow-Redirection Endoluminal Device (FRED, n = 1). Transradial access was successful in all cases, but femoral crossover was required in 3 cases (4.1%) due to tortuous anatomy and inadequate support of the catheters in 2 cases and an inability to navigate to the target vessel in a patient with an aberrant right subclavian artery. All 71 other interventions were successfully performed via the transradial approach (95.9%). No access site complications were encountered. Asymptomatic radial artery occlusion was encountered in 1 case (3.7%).CONCLUSIONS:Flow diverters can be successfully placed via the transradial approach with high technical success, low access site complications, and a low femoral crossover rate.

The transradial access (TRA), including distal radial artery (dRA) access in the anatomic snuffbox and radial artery (RA) access at the palmar surface of the wrist, is being increasingly used as primary vascular access for neurointerventional procedures. In prior years, large randomized trials in the field of interventional cardiology and more recent articles in neurointerventional surgery have shown higher patient preference for the TRA, cost reduction, as well as lower morbidity and mortality compared with the traditional transfemoral access (TFA).1-11 Reduction in access site complications has been a particular advantage of wrist over femoral access and is an important consideration for vascular access choice in the treatment of intracranial aneurysms using flow diversion. Patients undergoing flow diversion are required to take dual-antiplatelet agents and receive heparin during the procedure, all of which increase the risk of bleeding from the access site.12 Also, flow diverters (FDs) may require large-bore catheter assemblies for delivery and deployment, which may increase the risk of radial artery occlusion, access site bleeding, or vascular injury.13,14To date, only a limited number of case reports and case series have described the safety and feasibility of TRA for the treatment of intracranial aneurysms using flow diverters.15-22Recently, a large, retrospective multicenter study reported the safety of TRA for flow diversion, showing a lower access site (P = .039) and overall complication rate (P = .035).12 This study, however, did not cover catheter systems, patient functional outcome, and aneurysm occlusion. Here, we report our experience with TRA (dRA [anatomic snuffbox] and RA) for the treatment of intracranial aneurysms using all 3 FDA-approved flow diverters, including technical feasibility, procedural safety, patient outcome, and aneurysm occlusion on follow-up. Additionally, we reviewed the current literature on use of flow diverters via TRA.  相似文献   
63.
BACKGROUND AND PURPOSE:The coronavirus disease 2019 (COVID-19) pandemic has led to decreases in neuroimaging volume. Our aim was to quantify the change in acute or subacute ischemic strokes detected on CT or MR imaging during the pandemic using natural language processing of radiology reports.MATERIALS AND METHODS:We retrospectively analyzed 32,555 radiology reports from brain CTs and MRIs from a comprehensive stroke center, performed from March 1 to April 30 each year from 2017 to 2020, involving 20,414 unique patients. To detect acute or subacute ischemic stroke in free-text reports, we trained a random forest natural language processing classifier using 1987 randomly sampled radiology reports with manual annotation. Natural language processing classifier generalizability was evaluated using 1974 imaging reports from an external dataset.RESULTS:The natural language processing classifier achieved a 5-fold cross-validation classification accuracy of 0.97 and an F1 score of 0.74, with a slight underestimation (−5%) of actual numbers of acute or subacute ischemic strokes in cross-validation. Importantly, cross-validation performance stratified by year was similar. Applying the classifier to the complete study cohort, we found an estimated 24% decrease in patients with acute or subacute ischemic strokes reported on CT or MR imaging from March to April 2020 compared with the average from those months in 2017–2019. Among patients with stroke-related order indications, the estimated proportion who underwent neuroimaging with acute or subacute ischemic stroke detection significantly increased from 16% during 2017–2019 to 21% in 2020 (P = .01). The natural language processing classifier performed worse on external data.CONCLUSIONS:Acute or subacute ischemic stroke cases detected by neuroimaging decreased during the COVID-19 pandemic, though a higher proportion of studies ordered for stroke were positive for acute or subacute ischemic strokes. Natural language processing approaches can help automatically track acute or subacute ischemic stroke numbers for epidemiologic studies, though local classifier training is important due to radiologist reporting style differences.

There is much concern regarding the impact of the coronavirus disease 2019 (COVID-19) pandemic on the quality of stroke care, including issues with hospital capacity, clinical resource re-allocation, and the safety of patients and clinicians.1,2 Previous reports have shown that there have been substantial decreases in stroke neuroimaging volume during the pandemic.3,4 In addition, acute ischemic infarcts have been found on neuroimaging studies in many hospitalized patients with COVID-19, though the causal relationship is unclear.5,6 Studies like these and other epidemiologic analyses usually rely on the creation of manually curated databases, in which identification of cases can be time-consuming and difficult to update in real-time. One way to facilitate such research is to use natural language processing (NLP), which has shown utility for automated analysis of radiology report data.7 NLP algorithms have been developed previously for the classification of neuroradiology reports for the presence of ischemic stroke findings and acute ischemic stroke subtypes.8,9 Thus, NLP has the potential to facilitate COVID-19 research.In this study, we developed an NLP machine learning model that classifies radiology reports for the presence or absence of acute or subacute ischemic stroke (ASIS), as opposed to chronic stroke. We used this model to quantify the change in ASIS detected on all CT or MR imaging studies performed at a large comprehensive stroke center during the COVID-19 pandemic in the United States. We also evaluated NLP model generalizability and different training strategies using a sample of radiology reports from a second stroke center.  相似文献   
64.

Background

Children have a statutory right to a smoke-free environment, and tobacco control advocates are now considering regulation of smoking behavior in the private sphere. The Norwegian Institute of Public Health has investigated the support for a ban on smoking in cars with children compared to other possible extensions of the tobacco act among the Norwegian public.

Material and methods

A nationwide representative survey (CAWI) of 5543 participants was conducted in 2014–2015. Respondents were asked to consider several possible new tobacco control measures, through selfreported ranking on 5-point scales for each measure. Multiple logistic regression models were applied to control for confounders (i.a. smoking behavior) for the tendency to state full support.

Results

A majority (78 % of all respondents, 61.8% of daily smokers) supported a proposal prohibiting smoking in cars when children are present. This proposal received substantially more support than bans on private balconies, in parks and at public transport stops and work entrances. Full support for the latter proposals varied between 39.9% and 58.1% (between 2.7% and 16.8% among smokers). Differences by smoking status were maintained after multiple controls.

Interpretation

The strong endorsement of the proposal (also provided by the majority of current smokers) suggests high legitimacy and compliance, which means that an implementation could be introduced without serious enforcement problems.  相似文献   
65.

Background

In November 2017, the World Health Organization received initial reports of suspected diphtheria cases in camps established for displaced Rohingyas in Cox’s Bazar district, Bangladesh. By January 11, 2018, over 4,000 suspected cases of diphtheria and 30 deaths were reported. The Bangladesh government and partners implemented a diphtheria vaccination campaign in December 2017. Outbreak response staff reported anecdotal evidence of vaccine hesitancy. Our assessment aimed to understand vaccination barriers and opportunities to enhance vaccine demand among displaced Rohingyas in Bangladesh.

Methods

In January 2018, we conducted a qualitative assessment consisting of nine focus group discussions and 15 key informant interviews with displaced Rohingyas in three camps. Participants included mothers and fathers with under five-year-old children, community volunteers, majhis (camp leaders), Islamic religious leaders, traditional and spiritual healers, and teachers. We recruited participants using purposive sampling, and analyzed the data thematically.

Results

Across focus groups and in-depth interviews, trusted information sources cited by participants included religious leaders, elders, village doctors, pharmacists, majhis, and mothers trained by non-governmental organizations to educate caregivers. Treatment of diphtheria and measles was usually sought from multiple sources including traditional and spiritual healers, village doctors, pharmacies, and health clinics. Major barriers to vaccination included: various beliefs about vaccination causing people to become Christian; concerns about multiple vaccines being received on the same day; worries about vaccination side effects; and, lack of sensitivity to cultural gender norms at the vaccination sites.

Conclusion

Although vaccination was understood as an important intervention to prevent childhood diseases, participants reported numerous barriers to vaccination. Strengthening vaccine demand and acceptance among displaced Rohingyas can be enhanced by improving vaccination delivery practices and engaging trusted leaders to address religious and cultural barriers using community-based channels.  相似文献   
66.
Abstract

Purpose: We examined underlying psychosocial processes of a behavioral treatment for urinary incontinence (UI) of prostate cancer survivors.

Design: Secondary analysis of data collected from a clinical trial.

Sample: Two hundred forty-four prostate cancer survivors who participated in a clinical trial of behavioral intervention to UI as intervention or control subjects.

Methods: The participants had a 3-month behavioral intervention or usual care and were followed up for an additional 3?months. They were assessed at baseline, 3, and 6?months. Latent growth curve models were performed to examine trajectories of each study variable and relationships among the variables.

Findings: Increasing self-efficacy and social support were significantly and independently associated with more reduction of urinary leakage frequency over time.

Implications for psychosocial oncology: Providing problem-solving skills and social support, including peer support, are essential for empowering patients to reduce UI.  相似文献   
67.
ABSTRACT

Schnitzler syndrome is a rare, auto inflammatory condition known to manifest with bone pain, urticarial rash, fevers, relapsing arthralgia, and fatigue. In this case report, we describe a patient who was diagnosed with Schnitzler Syndrome that had initially presented with a unilateral pressure-type headache with a sensation of a ‘dagger’ stabbing into the back of the eye. He also had an associated ipsilateral redness of the conjunctiva, eyelid swelling, subtle optic disc elevations bilaterally and facial flushing - but with no visual acuity, pupillary, or lacrimatory changes. Anterior segment, fundoscopy, intraocular pressures and extraocular muscle movements were otherwise normal.  相似文献   
68.
Abstract

Introduction: Student-staff partnerships as a concept to improve medical education have received a growing amount of attention. Such partnerships are collaborations in which students and teachers seek to improve education by each adding their unique contribution to decision-making and implementation processes. Although previous research has demonstrated that students are favourable to this concept, teachers remain hesitant. The present study investigated teachers’ conceptions of student-staff partnerships and of the prerequisites that are necessary to render such partnerships successful and enhance educational quality.

Method: We conducted semi-structured interviews with 14 course coordinators who lead course design teams and also teach in 4 bachelor health programmes, using Bovill and Bulley’s levels of student participation as sensitising concepts during data analysis.

Results: The results pointed to three different conceptions of student-staff partnerships existing among teachers: Teachers teach and students study; teachers teach and value students’ feedback; and teachers and students co-create. The prerequisites for effective co-creation teachers identified were: Teachers must be open to involve students and create dialogues; students must be motivated and have good communication skills; the organisation must be supportive; and teachers should have the final say.

Conclusion: We conclude that teachers’ conceptions are consistent with Bovill and Bulley’s levels of student participation. Under certain conditions, teachers are willing to co-create and reach the highest levels of student participation.  相似文献   
69.
Background:Criteria for diagnosis and compensation of occupational musculoskeletal diseases varies widely between countries as demonstrated by the large differences between countries with comparable economics and social systems (for example, within the European Union). Several countries have a list of occupational diseases and sometimes these lists include diagnostic and attribution criteria, but these criteria are usually not very specific, and they may also be very different.Objectives:The aim of this paper is to explicitly define what are the information needed for an evidence-based diagnosis and attribution of an occupational musculoskeletal disease.Methods:Based on the general framework of evidence-based medicine, a review is presented of the information required to define: - when a musculoskeletal disease is present, according to the best available techniques; - how to define a relevant exposure to biomechanical risk factors, according to the best available techniques.Results:Criteria are presented to combine information regarding the diagnosis of a musculoskeletal disease and exposure to biomechanical risk factors for an evidence-based attribution of the disease to the occupational exposure. The criteria use a probabilistic model that combine epidemiologic and medical findings, workplace exposure assessment, and non-occupational factors evaluation.Discussion:The use of the proposed criteria may improve the process of diagnosis and attribution of an occupational musculoskeletal disease. In addition, it makes possible to associate a probability rank to the attribution and, ultimately, it may improve the overall quality of the decisional process of the occupational physician.Key words: Criteria, occupational disease, musculoskeletal system  相似文献   
70.
ABSTRACT

Language and executive functioning are major impairments in many neurodevelopmental disorders, but little is known about the relations between these constructs, particularly using parent-report. Thus, the current research sought to examine relations between executive function and language in two groups – Down syndrome (DS; n=41; Mage = 11.2) and autism spectrum disorder (ASD; n=91; Mage = 7.7). Results were as follows: in DS, executive function predicted pragmatic, but not structural language after covarying for age, sex, and social functioning; in ASD, executive function predicted both. Findings highlight the interrelatedness of language and executive functioning and may have implications for intervention development.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号