全文获取类型
收费全文 | 1398559篇 |
免费 | 99459篇 |
国内免费 | 3233篇 |
专业分类
耳鼻咽喉 | 20405篇 |
儿科学 | 41680篇 |
妇产科学 | 40075篇 |
基础医学 | 194236篇 |
口腔科学 | 47370篇 |
临床医学 | 118465篇 |
内科学 | 275397篇 |
皮肤病学 | 31018篇 |
神经病学 | 110792篇 |
特种医学 | 55414篇 |
外国民族医学 | 437篇 |
外科学 | 217349篇 |
综合类 | 31983篇 |
现状与发展 | 7篇 |
一般理论 | 533篇 |
预防医学 | 96804篇 |
眼科学 | 33010篇 |
药学 | 103963篇 |
4篇 | |
中国医学 | 3117篇 |
肿瘤学 | 79192篇 |
出版年
2018年 | 13071篇 |
2016年 | 11796篇 |
2015年 | 13316篇 |
2014年 | 18704篇 |
2013年 | 28204篇 |
2012年 | 36589篇 |
2011年 | 38771篇 |
2010年 | 23168篇 |
2009年 | 22698篇 |
2008年 | 37376篇 |
2007年 | 40604篇 |
2006年 | 41018篇 |
2005年 | 39839篇 |
2004年 | 38634篇 |
2003年 | 37315篇 |
2002年 | 36767篇 |
2001年 | 64409篇 |
2000年 | 65997篇 |
1999年 | 56172篇 |
1998年 | 15515篇 |
1997年 | 14165篇 |
1996年 | 13549篇 |
1995年 | 12803篇 |
1994年 | 12026篇 |
1992年 | 43334篇 |
1991年 | 41781篇 |
1990年 | 40998篇 |
1989年 | 39971篇 |
1988年 | 37371篇 |
1987年 | 36790篇 |
1986年 | 35229篇 |
1985年 | 33512篇 |
1984年 | 25248篇 |
1983年 | 21431篇 |
1982年 | 13173篇 |
1981年 | 11983篇 |
1979年 | 24187篇 |
1978年 | 17340篇 |
1977年 | 15124篇 |
1976年 | 13616篇 |
1975年 | 15520篇 |
1974年 | 18306篇 |
1973年 | 17747篇 |
1972年 | 16971篇 |
1971年 | 15808篇 |
1970年 | 15025篇 |
1969年 | 14433篇 |
1968年 | 13529篇 |
1967年 | 12096篇 |
1966年 | 11340篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.
Timo Jaakkola Harto Hakonen Anna Kankaanpää Laura Joensuu Janne Kulmala Jouni Kallio Anthony Watt Tuija H. Tammelin 《Journal of Science and Medicine in Sport》2019,22(1):85-90
Objectives
This study aimed to investigate cross-lagged associations of leaping skill and throwing–catching skills with objectively measured moderate-to-vigorous physical activity (MVPA) and sedentary time (ST) during school transition from upper primary (Grade 6) to lower secondary school (Grade 7).Design
This study is a one-year prospective follow-up study within Finnish school settings. Students’ MVPA, ST, leaping skill and throwing–catching skills were measured at Grade 6 and subsequently at Grade 7.Methods
A sample of 336 students (163 girls, 173 boys; M age = 12.0 years, SD = 0.4 at Grade 6 participated in the study. Students’ MVPA and ST were measured objectively by hip-worn accelerometers. Leaping skill was measured by 5-leaps test. Throwing and catching skills were measured by throwing–catching combination test. Cross-lagged structural equation modeling was conducted to evaluate the associations between MVPA, ST, leaping skill, and throwing–catching skills at Grade 6 and Grade 7.Results
Results demonstrated three significant cross-lagged associations among girls: (1) leaping skill measured at Grade 6 was negatively associated with ST at Grade 7; (2) objectively measured MVPA at Grade 6 associated positively with leaping skill at Grade 7; and (3) throwing–catching skills measured at Grade 6 associated positively with leaping skill measured at Grade 7. There were no statistically significant cross-lagged associations between the study variables for the sample of boys.Conclusions
The results of this study indicated that supporting opportunities for girls’ engagement in both MVPA and leaping skill development activities during their primary school education is strongly recommended. 相似文献22.
Peyman Sardari Nia Jean H.T. Daemen Jos G. Maessen 《The Journal of thoracic and cardiovascular surgery》2019,157(4):1567-1574
Objectives
The aim of this study was to develop a high-fidelity minimally invasive mitral valve surgery (MIMVS) simulator.Methods
The process of industrial serial design was applied based on pre-set requirements, acquired by interviewing experienced mitral surgeons. A thoracic torso with endoscopic and robotic access and disposable silicone mitral valve apparatus with a feedback system was developed. The feedback system was based on 4 cameras around the silicone valve and an edge detection algorithm to calculate suture depth and width. Validity of simulator measurements was assessed by comparing simulator-generated values with measurements done manually on 3-dimensional reconstructed micro-computed tomography scan of the same sutures. Independent surgeons tested the simulator between 2014 and 2018, whereupon an evaluation was done through a questionnaire.Results
The feedback system was able to provide width and depth measurements, which were subsequently scored by comparison to pre-set target values. Depth did not significantly differ between simulator and micro-computed tomography scan measurements (P = .139). Width differed significantly (P = .001), whereupon a significant regression equation was found (P < .0001) to calibrate the simulator. After calibration, no significant difference was found (P = .865). In total, 99 surgeons tested the simulator and more than agreed with the statements that the simulator is a good method for training MIMVS, and that the mitral valve and suture placement looked and felt realistic.Conclusions
We successfully developed a high-fidelity MIMVS simulator for endoscopic and robotic approaches. The simulator provides a platform to train skills in an objective and reproducible manner. Future studies are needed to provide evidence for its application in training surgeons. 相似文献23.
Mae Lynn Reyes-Rodríguez Hunna J. Watson Concepción Barrio Donald H. Baucom Yormeri Silva Kiara L. Luna-Reyes 《Eating disorders》2019,27(2):205-229
ABSTRACTLatinos are less likely to seek health care for eating disorders and more likely to drop out of treatment than members of other ethnic groups, highlighting existing challenges to engagement in traditional mental health care. This study explored the role of family in the treatment of adult Latinas with eating disorders through content analysis of family sessions adjunctive to cognitive behavioral therapy. This study yielded insight into the experiences of 10 Latinas with eating disorders (M age = 39.90 years) and 10 relatives (M age = 39.50) from the Promoviendo una Alimentación Saludable trial who were randomly selected to receive six family enhancement sessions. Data from 53 sessions were analyzed using a qualitative content analysis approach. Family intervention might serve as a valuable adjunct to conventional treatment by positively influencing social, family, and emotional support for Latinas with eating disorders. 相似文献
24.
S. Fatahi M. Pezeshki S.M. Mousavi A. Teymouri J. Rahmani H. Kord Varkaneh E. Ghaedi 《Nutrition, metabolism, and cardiovascular diseases : NMCD》2019,29(5):432-439
Background and aim
Given the contradictory results of previous randomized controlled trials (RCTs), we performed a systematic review and meta-analysis to quantify and summarize the effects of folic acid supplementation on C-reactive protein (CRP).Methods and results
We performed a systematic search of all available RCTs conducted up to October 2018 in the following databases: PubMed, Scopus, and Cochrane. RCTs that investigated the effect of folate on CRP were included in the present study. Data were combined with the use of generic inverse-variance random-effects models. Statistical heterogeneity between studies was evaluated using Cochran's Q-test. Ten RCTs (1179 subjects) were included in the present meta-analysis. Pooled analysis results showed that folate supplementation significantly lowered the serum CRP level (weighted mean difference (WMD): ?0.685 mg/l, 95% CI: ?1.053, ?0.318, p < 0.001). However, heterogeneity was significant (I2 = 96.7%, p = 0.000). Stratified analyses indicated that sex, intervention period, and type of study population were sources of heterogeneity. Following analysis, results revealed that the greatest impact was observed in women (WMD: ?0.967 mg/l, 95% CI: ?1.101, ?0.833, p = 0.000), patients with type 2 diabetes mellitus (WMD: ?1.764 mg/l, 95% CI: ?2.002, ?1.526, p = 0.000), and intervention period less than 12 weeks (WMD: ?0.742 mg/l, 95% CI: ?0.834, ?0.650, p = 0.000).Conclusion
This meta-analysis suggested that folic acid supplementation could significantly lower the serum CRP level. Folic acid leads to greater CRP lowering effect in women, patients with T2DM, and those with less than 12-week intervention. 相似文献25.
26.
27.
R. Pop A. Hasiu P.H. Mangin F. Severac D. Mihoc D. Nistoran M. Manisor M. Simu S. Chibbaro R. Gheoca V. Quenardelle O. Rouyer V. Wolff R. Beaujeux 《AJNR. American journal of neuroradiology》2021,42(5):921
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
28.
Yuanjian Fang Hui Shi Reng Ren Lei Huang Takeshi Okada Cameron Lenahan Marcin Gamdzyk Zachary D. Travis Qin Lu Lihui Tang Yi Huang Keren Zhou Jiping Tang Jianmin Zhang John H. Zhang 《Neurotherapeutics》2020,17(4):1954
Brain edema is a vital contributor to early brain injury after subarachnoid hemorrhage (SAH), which is responsible for prolonged hospitalization and poor outcomes. Pharmacological therapeutic targets on edema formation have been the focus of research for decades. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to participate in neural development and brain injury. Here, we used PACAP knockout CRISPR to demonstrate that endogenous PACAP plays an endogenous neuroprotective role against brain edema formation after SAH in rats. The exogenous PACAP treatment provided both short- and long-term neurological benefits by preserving the function of the blood–brain barrier and glymphatic system after SAH. Pretreatment of inhibitors of PACAP receptors showed that the PACAP-involved anti-edema effect and neuroprotection after SAH was facilitated by the selective PACAP receptor (PAC1). Further administration of adenylyl cyclase (AC) inhibitor and sulfonylurea receptor 1 (SUR1) CRISPR activator suggested that the AC–cyclic adenosine monophosphate (cAMP)–protein kinase A (PKA) axis participated in PACAP signaling after SAH, which inhibited the expression of edema-related proteins, SUR1 and aquaporin-4 (AQP4), through SUR1 phosphorylation. Thus, PACAP may serve as a potential clinical treatment to alleviate brain edema in patients with SAH.Electronic supplementary materialThe online version of this article (10.1007/s13311-020-00925-3) contains supplementary material, which is available to authorized users.Key Words: Subarachnoid hemorrhage, brain edema, pituitary adenylate cyclase-activating polypeptide, blood–brain barrier, glymphatic system 相似文献
29.
Claudia Deckers Maarten J Steyvers Gerjon Hannink H W Bart Schreuder Jacky W J de Rooy Ingrid C M Van Der Geest 《Acta orthopaedica》2020,91(4):471
Background and purpose — Adequate staging of chondroid tumors at diagnosis is important as it determines both treatment and outcome. This systematic review provides an overview of MRI criteria used to differentiate between atypical cartilaginous tumors (ACT) and high-grade chondrosarcoma (HGCS).Patients and methods — For this systematic review PubMed and Embase were searched, from inception of the databases to July 12, 2018. All original articles describing MRI characteristics of pathologically proven primary central chondrosarcoma and ACT were included. A quality appraisal of the included papers was performed. Data on MRI characteristics and histological grade were extracted by 2 reviewers. Meta-analysis was performed if possible. The study is registered with PROSPERO, CRD42018067959.Results — Our search identified 2,132 unique records, of which 14 studies were included. 239 ACT and 140 HGCS were identified. The quality assessment showed great variability in consensus criteria used for both pathologic and radiologic diagnosis. Due to substantial heterogeneity we refrained from pooling the results in a meta-analysis and reported non-statistical syntheses. Loss of entrapped fatty marrow, cortical breakthrough, and extraosseous soft tissue expansion appeared to be present more often in HGCS compared with ACT.Interpretation — This systematic review provides an overview of MRI characteristics used to differentiate between ACT and HGCS. Future studies are needed to develop and assess more reliable imaging methods and/or features to differentiate ACT from HGCS.The incidence of chondrosarcoma of bone appears to have been increasing during the last decade and is now reported to be the most common primary malignant bone tumor in several countries (Thorkildsen et al. 2018, van Praag et al. 2018). Conventional chondrosarcoma is the most common subtype of chondrosarcoma. Other subtypes of chondrosarcoma (e.g., juxtacortical, mesenchymal, or secondary chondrosarcoma) are rare and show different radiologic appearance and clinical behavior (Bindiganavile et al. 2015).Conventional chondrosarcoma is classified into the histological grades 1 (currently known as atypical cartilaginous tumor [ACT]), 2, and 3. The metastatic potential, and therefore the disease-specific survival, correlates with the histological grade (Fletcher et al. 2013, Laitinen et al. 2018, Thorkildsen et al. 2018). ACTs rarely metastasize and are therefore reclassified as an intermediate type of tumor, not a malignancy (Fletcher et al. 2013). Due to the increase in patients undergoing MRI examinations for joint-related complaints, the incidental detection of ACT has increased substantially (van Praag et al. 2018).With the increasing incidence of ACT, clear radiologic criteria to differentiate ACT from high-grade chondrosarcoma (i.e., grades 2 and 3) become more and more important. Adequate staging of chondroid tumors at diagnosis is important as it determines both treatment and prognosis. High-grade chondrosarcomas behave aggressively. Between 10% and 30% of grade 2 and about 70% of grade 3 chondrosarcomas metastasize (Evans et al. 1977). Hence, high-grade chondrosarcoma (HGCS) requires wide en bloc resection with free surgical margins. In contrast, ACTs are intermediate tumors and can be treated either with intralesional curettage and local adjuvant or nonoperatively with regular follow-up when located in the long bones (Deckers et al. 2016).Due to the heterogenous composition of chondroid tumors, diagnostic biopsy is unreliable in assessing the genuine histological grade and malignant potential of chondrosarcomas (Laitinen et al. 2018). Therefore, physicians need to rely on imaging and clinical findings (e.g., pain is more common in HGCS) to differentiate ACT from HGCS. Imaging evaluation of cartilaginous and other bone tumors is generally based on multimodal assessment including at least conventional radiography and MRI (Nascimento et al. 2014).During the most recent decades research has focused mainly on differentiating enchondroma from chondrosarcoma (Choi et al. 2013, Douis et al. 2014, Crim et al. 2015, Lisson et al. 2018). New insights have shown that both enchondroma and ACT located in the long bones can be observed without treatment (Deckers et al. 2016, Sampath Kumar et al. 2016, Chung et al. 2018). These insights make the differentiation between ACT and HGCS clinically relevant. Currently, literature on differentiating ACT from HGCS is sparse and clear radiologic criteria are lacking. Therefore, we performed a systematic review to provide an overview of MRI characteristics used to date to differentiate between ACT and HGCS. 相似文献
30.
Samantha E. Martens Ineke H. A. P. Wolfhagen Jill R. D. Whittingham Diana H. J. M Dolmans 《Medical teacher》2020,42(5):529-535
AbstractIntroduction: 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