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   174941篇
  免费   970篇
耳鼻咽喉   1128篇
儿科学   6623篇
妇产科学   3024篇
基础医学   16446篇
口腔科学   1531篇
临床医学   12356篇
内科学   30659篇
皮肤病学   659篇
神经病学   16369篇
特种医学   8907篇
外科学   28685篇
综合类   2325篇
预防医学   18069篇
眼科学   2722篇
药学   9457篇
中国医学   623篇
肿瘤学   16328篇
  2019年   17篇
  2018年   21930篇
  2017年   17364篇
  2016年   19503篇
  2015年   891篇
  2014年   771篇
  2013年   737篇
  2012年   6915篇
  2011年   20943篇
  2010年   18778篇
  2009年   11473篇
  2008年   19449篇
  2007年   21632篇
  2006年   482篇
  2005年   2113篇
  2004年   3316篇
  2003年   4296篇
  2002年   2450篇
  2001年   294篇
  2000年   420篇
  1999年   175篇
  1998年   199篇
  1997年   205篇
  1996年   97篇
  1995年   100篇
  1994年   93篇
  1993年   59篇
  1992年   46篇
  1991年   90篇
  1990年   131篇
  1989年   85篇
  1988年   57篇
  1987年   51篇
  1986年   31篇
  1985年   43篇
  1984年   29篇
  1983年   25篇
  1982年   28篇
  1980年   40篇
  1974年   24篇
  1970年   23篇
  1969年   22篇
  1968年   21篇
  1939年   21篇
  1938年   60篇
  1937年   25篇
  1935年   22篇
  1934年   30篇
  1932年   56篇
  1930年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Strabismus is a pathology that affects approximately 4 % of the population, causing aesthetic problems reversible at any age and irreversible sensory alterations that modify the vision mechanism. The Hirschberg test is one type of examination for detecting this pathology. Computer-aided detection/diagnosis is being used with relative success to aid health professionals. Nevertheless, the routine use of high-tech devices for aiding ophthalmological diagnosis and therapy is not a reality within the subspecialty of strabismus. Thus, this work presents a methodology to aid in diagnosis of syndromic strabismus through digital imaging. Two hundred images belonging to 40 patients previously diagnosed by an specialist were tested. The method was demonstrated to be 88 % accurate in esotropias identification (ET), 100 % for exotropias (XT), 80.33 % for hypertropias (HT), and 83.33 % for hypotropias (HoT). The overall average error was 5.6Δ and 3.83Δ for horizontal and vertical deviations, respectively, against the measures presented by the specialist.  相似文献   
992.
993.
The etiology of system lupus erythematosus (SLE) still remains unclear, and vitamin D is associated with immune response. Although a few studies are conducted to investigate the association between polymorphism in vitamin D receptor (VDR) genes and SLE risk, their results are conflicting. Following the guideline of PRISMA, we conducted a systematic search and meta-analysis of the BsmI polymorphism rs1544410 and the risk of SLE. The pooled odds ratios (OR) and its 95 % confidential interval (CI) were calculated by using Stata Version 10 with dominant and recessive model and allele analyses. Nine studies were included in our meta-analysis with a total of 1247 SLE cases and 1687 controls. No significant association was found in both models in the overall population. Only Bb?+?BB genotypes showed a significantly elevated SLE risk in Asian subgroup with an OR of 3.26 (95 % CI?=?1.30–8.17) while no significance was observed in Caucasian population. Notably, B allele significantly increased the SLE risk among Asian population with an OR of 2.29 (95 % CI?=?1.14–4.61). No positive findings were reported in Caucasian population and in the overall analysis. In Asian population, Bb?+?BB genotype and B allele can significantly increase the SLE risk.  相似文献   
994.

Background

As treatment for chronic hepatitis C (HCV) virus has evolved to all-oral, interferon-free directly acting antiviral (DAA) therapy, the impact of these improvements on patient adherence has not been described.

Methods

Medication adherence was measured in 60 HCV, genotype-1, treatment-naïve participants enrolled in a phase 2a clinical trial at the National Institutes of Health and community clinics. Participants received either ledipasvir/sofosbuvir (LDV/SOF) (90 mg/400 mg) (one pill) daily for 12 weeks, LDV/SOF + GS-9451 (80 mg/day) (two pills) daily for 6 weeks, or LDV/SOF + GS-9669 (500 mg twice daily; three pills, two in the morning, one in the evening) for 6 weeks. Adherence was measured using medication event monitoring system (MEMS) caps, pill counts and patient report.

Results

Overall adherence to DAAs was high. Adherence declined over the course of the 12-week treatment (p = 0.04). While controlled psychiatric disease or symptoms of depression did not influence adherence, recent drug use was a risk factor for non-adherence to 12-week (p = 0.01), but not 6-week regimens. Adherence as measured by MEMS was lower than by patient report.

Conclusions

Adherence to short courses of DAA therapy with 1–3 pills a day was excellent in an urban population with multiple risk factors for non-adherence.
  相似文献   
995.
Abstract Currently available anticoagulants are effective in reducing the recurrence rate of venous thromboembolism (VTE). However, anticoagulant treatment is associated with an increased risk for bleeding complications. Thus, anticoagulation has to be discontinued when benefit of treatment no longer clearly outweigh its risks. The duration of anticoagulant treatment is currently framed based on the estimated individual risk for recurrent VTE. The incidence of recurrent VTE can be estimated through a two-step decision algorithm. Firstly, the features of the patient (gender), of the initial event (proximal or distal deep vein thrombosis or pulmonary embolism), and the associated conditions (cancer, surgery, etc) provide essential information on the risk for recurrence after anticoagulant treatment discontinuation. Secondly, at time of anticoagulant treatment discontinuation, d-dimer levels and residual thrombosis have been indicated as predictors of recurrent VTE. Current evidence suggests that the risk of recurrence after stopping therapy is largely determined by whether the acute episode of VTE has been effectively treated and by the patient’s intrinsic risk of having a new episode of VTE. All patients with acute VTE should receive oral anticoagulant treatment for three months. At the end of this treatment period, physicians should decide for withdrawal or indefinite anticoagulation. Based on intrinsic patient’s risk for recurrent VTE and for bleeding complications and on patient preference, selected patients could be allocated to indefinite treatment with VKA with scheduled periodic re-assessment of the benefit from extending anticoagulation. Alternative strategies for secondary prevention of VTE to be used after conventional anticoagulation are currently under evaluation. Cancer patients should receive low molecular-weight heparin over warfarin in the long-term treatment of VTE. These patients should be considered for extended anticoagulation at least until resolution of underlying disease. Abbreviated abstract The risk for recurrent venous thromboembolism can be estimated through a two-step algorithm. Firstly, the features of the patient (gender), of the initial event (proximal or distal deep vein thrombosis or pulmonary embolism), and the associated conditions (cancer, surgery, etc) are essential to estimate the risk for recurrence after anticoagulant treatment discontinuation. Secondly, a correlation has been shown between d-dimer levels and residual thrombosis at time of anticoagulant treatment discontinuation and the risk of recurrence. Currently available anticoagulants are effective in reducing the incidence of recurrent venous thromboembolism, but they are associated with an increased risk for bleeding complications. All patients with acute venous thromboembolism should receive oral anticoagulant treatment for three months. At the end of this treatment period physicians should decide for definitive withdrawal or indefinite anticoagulation with scheduled periodic re-assessment of the benefit from extending anticoagulation.  相似文献   
996.
Background  Evidence-based medicine (EBM) is widely taught in residency, but evidence for effectiveness of EBM teaching on changing residents’ behavior is limited. Objective  To investigate the impact of an EBM curriculum on residents’ use of evidence-based resources in a simulated clinical experience. Design/Participants  Fifty medicine residents randomized to an EBM teaching or control group. Measurements  A validated test of EBM knowledge (Fresno test) was administered before and after intervention. Post intervention, residents twice completed a Web-based, multiple-choice instrument (15 items) comprised of clinical vignettes, first without then with access to electronic resources. Use of electronic resources was tracked using ProxyPlus software. Within group pre–post differences and between group post-test differences were examined. Results  There was more improvement in EBM knowledge (100-point scale) for the intervention group compared to the control group (mean score increase 22 vs. 12, p = 0.012). In the simulated clinical experience, the most commonly accessed resources were Ovid (71% of residents accessed) and InfoPOEMs (62%) for the EBM group and UptoDate (67%) and MDConsult (58%) for the control group. Residents in the EBM group were more likely to use evidence-based resources than the control group. Performance on clinical vignettes was similar between the groups both at baseline (p = 0.19) and with access to information resources (p = 0.89). Conclusions  EBM teaching improved EBM knowledge and increased use of evidence-based resources by residents, but did not improve performance on Web-based clinical vignettes. Future studies will need to examine impact of EBM teaching on clinical outcomes.  相似文献   
997.
Stroke is a rare but severe event after acute coronary syndrome. Relations between both arterial territories are still discussed but prevalence of asymptomatic carotid stenosis potentially implicated in the mechanism of stroke is under-investigated. This study aimed to determine the prevalence of asymptomatic carotid stenosis in that population and review the value of screening in a view to potential surgical correction or other preventive therapies. Systematic carotid Doppler ultrasound screening was implemented on 152 consecutive patients admitted to the intensive care unit due to acute coronary syndrome. Fifty-two percent of patients had at least one carotid artery stenosis determined using the NASCET method. Forty-three percent had at least one carotid stenosis <30%, 6% had mild (30–60%) stenosis, and 2.6% had high-grade (>60%) stenosis. Existence of carotid stenosis was associated with age, diabetes mellitus, hypertension, and with the extent of the coronary atherosclerosis (left main artery stenosis). In multivariate analysis, age and diabetes were independently associated with existence of a carotid stenosis. When ultrasound screening was restricted to patients identified by multivariate analysis, the prevalence of carotid stenosis potentially requiring surgical treatment rose to 4.6%. The frequency of asymptomatic carotid atherosclerosis was high in this population but lesions were mild. While the small number of high-grade lesions indicates that systematic screening is not to be recommended, screening of patients aged >65 years or with diabetes, or both, with a view to surgery may be envisaged, since the role of mild stenosis in the occurrence of stroke remains debatable.  相似文献   
998.

Background/Purpose

Carcinoma of the distal bile duct is associated with poor prognosis. Surgical resection remains the only potentially curative treatment. We conducted a retrospective study to identify prognostic factors determining longterm survival.

Methods

From 1990 to 2006, 95 patients with distal and/or middle bile duct carcinoma had resections. Fifty-four patients underwent pylorus-preserving pancreaticoduodenectomy (57%) and 41 patients underwent standard Kausch-Whipple pancreaticoduodenectomy (43%). Nine patients underwent pancreaticoduodenectomy including portal vein resection (9%).

Results

Overall 1-, 3-, and 5-year survival rates were 60%, 36%, and 29%, respectively. Five-year survival after R0 resection was 34%, and after R1 resection it was 0%. Four patients died during their hospital stay (4%). Multivariate analysis showed negative resection margins (P = 0.040), lymphatic vessel invasion (P = 0.036), and portal vein infiltration (P = 0.027) as strong predictors for survival, whereas the location of the tumor (distal bile duct vs middle bile duct) and lymph node status were not identified as independent prognostic factors.

Conclusions

Five-year survival depends strongly on negative resection margins, independent of nodal status. Portal vein resections in patients with portal vein involvement fail to ameliorate long-term survival. Primary tumor site — middle bile duct or distal bile duct — did not determine prognosis.
  相似文献   
999.

Background

Statins have become standard of care in the prevention and treatment of atherosclerotic cardiovascular disease. The objective of this study was to examine the trends in statin use among Australians aged ≥?65 years for the period 2007–2016.

Methods

Data from the Pharmaceutical Benefits Scheme covering a 10% random sample of the Australian population were analysed. The 1-year prevalence and incidence of statin use were determined for each year, as were the percentage of statin dispensations according to statin type or intensity and the percentage of new users prescribed each statin type or intensity. To describe relative changes, age-sex adjusted rate ratios (RRs) and 95% confidence intervals (CIs) were determined via Poisson regression modelling using 2007 as the reference year.

Results

The 1-year prevalence of statin use increased consistently each year from 34.2% in 2007 to 44.1% in 2016 (RR 1.29, 95% CI 1.28–1.31). The 1-year incidence was 68.5 per 1000 in 2007 and 59.0 per 1000 in 2016 (RR 0.87, 95% CI 0.84–0.90). Women were 18% (age-adjusted rate ratio [aRR] 0.82, 95% CI 0.79–0.83) less likely than men to initiate statins across all years. The incidence of statin use was also highest among individuals aged 65–74 years, who were about 15% (sex-adjusted rate ratio [sRR] 1.15, 95% CI 1.13–1.16) and 45% (sRR 1.45, 95% CI 1.44–1.47) more likely to initiate statins than those aged 75–84 and ≥ 85 years, respectively. Atorvastatin was the most commonly dispensed statin across all years. The proportion of new users dispensed high-intensity statins increased year-on-year from 23.6% in 2007 to 30.5% in 2016 (RR 1.26, 95% CI 1.21–1.31).

Conclusion

The proportion of older adults in Australia using statins has increased over the last decade, although the incidence has declined. Atorvastatin is the most commonly dispensed statin and the use of high intensity statin has increased.
  相似文献   
1000.

Purpose of Review

The development of food allergies is increasingly being recognized as a post-solid organ transplant complication. In this article, we review the spectrum of post-transplant food allergy development and the proposed mechanisms for de novo food allergies and the clinical significance they pose.

Recent Findings

The development of new food allergies is disproportionately associated with pediatric liver transplants, where it occurs in up to 38% of select populations. The mechanism of food allergy development is not completely understood; however, it is likely promoted by unbalanced immune suppression.

Summary

De novo food allergy development is a common complication of solid organ transplants with the highest risk occurring in pediatric liver transplant recipients. There are likely multiple mechanisms for food allergy development including passive transfer of membrane-bound IgE and lymphocytes from donor to recipient, as well as loss of food tolerance and active development of new food allergies. The optimal management of food allergies following organ transplants has not been well researched but may include changing the immune suppression regimen if the food allergy does not resolve without intervention.
  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