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   1431242篇
  免费   92023篇
  国内免费   2992篇
耳鼻咽喉   21123篇
儿科学   44211篇
妇产科学   41587篇
基础医学   199175篇
口腔科学   42164篇
临床医学   119103篇
内科学   278871篇
皮肤病学   32933篇
神经病学   113312篇
特种医学   57503篇
外国民族医学   466篇
外科学   222181篇
综合类   32449篇
现状与发展   6篇
一般理论   460篇
预防医学   96710篇
眼科学   34135篇
药学   106187篇
  23篇
中国医学   3273篇
肿瘤学   80385篇
  2018年   12513篇
  2015年   12860篇
  2014年   17960篇
  2013年   27112篇
  2012年   35542篇
  2011年   37395篇
  2010年   22284篇
  2009年   21718篇
  2008年   36138篇
  2007年   39427篇
  2006年   40093篇
  2005年   38964篇
  2004年   37907篇
  2003年   36727篇
  2002年   36183篇
  2001年   68491篇
  2000年   70065篇
  1999年   59323篇
  1998年   15840篇
  1997年   14588篇
  1996年   13901篇
  1995年   13073篇
  1994年   12225篇
  1993年   11454篇
  1992年   45409篇
  1991年   43853篇
  1990年   43104篇
  1989年   41945篇
  1988年   39137篇
  1987年   38538篇
  1986年   36978篇
  1985年   35050篇
  1984年   26268篇
  1983年   22231篇
  1982年   13341篇
  1981年   12226篇
  1979年   25233篇
  1978年   18045篇
  1977年   15661篇
  1976年   14077篇
  1975年   16139篇
  1974年   18946篇
  1973年   18459篇
  1972年   17608篇
  1971年   16480篇
  1970年   15589篇
  1969年   14968篇
  1968年   14056篇
  1967年   12534篇
  1966年   11701篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Objectives:To assess low dose altepase outcome and safety in comparison with a standard-dose regimen for acute ischemic stroke treatment in Egyptian patients.Materials:An observational prospective cohort non-randomized single blinded study was carried out during the period from November 2017 to December 2018. Eighty Egyptian acute ischemic stroke patients, all eligible for intravenous alteplase, were subdivided into 2 groups (40 patients in each group). Patients were thrombolysed at a dose of 0.6 mg/kg in the first group and 0.9 mg/kg in the second group. Both groups were compared in regard to safety and outcome. Safety was expressed by the rate of symptomatic intracranial hemorrhage (SICH) and 3 months mortality, while outcome was expressed by favorable outcomes at three months (modified Rankin Scale [mRS] of 0 to 2).Results:In the first group, 69.2% (n=27) achieved favorable outcomes at 90 days compared with 64.1% (n=25) in the second group (p=0.631). Ninety-day mortality was 5% (n=2) in the first group versus 2.5% (n=1) in the second group (p=0.556). Symptomatic intracranial hemorrhage was noted in 3 patients in the second group and zero patients in the first group (p=0.077).Conclusion:Low-dose alteplase could be a practical alternative for Egyptian populations with acute ischemic stroke especially in 3 to 4.5 hours window.

Cerebrovascular stroke is the second death and the seventh disability leading cause worldwide.1 Tissue-type plasminogen activator (tPA) alteplase was the first medication approved by the Food and Drug Administration (FDA) for the acute ischemic stroke (AIS) treatment on June 1996, within 3 hours of stroke onset with a recommended dose of 0.9 mg/kg (maximum 90mg).2 In 2008, the safety of using alteplase within 3 to 4.5 hours of stroke onset was approved by the Safe Implementation of Treatments in Stroke International Stroke Thrombolysis Registry (SITS -ISTR)3 and the European Cooperative Acute Stroke Study (ECASS III).4 However, thrombolytic therapy use has not been widely adopted, especially in developing countries. The restricted time window (3 to 4.5 hours), intracerebral hemorrhage (ICH) risk and the drug high cost are major obstacles preventing its broad application.5 Coagulation and fibrinolysis responses differ among different races, which increase symptomatic intracerebral hemorrhage (SICH) risk with standard-dose alteplase6 in Asian populations, many Asian neurologists considered alteplase low dose to be a better alternative for ischemic stroke treatment. Many studies had been conducted in order to prove the efficacy and safety of Alteplase low dose.7-9 One of these studies was the Japan Alteplase Clinical Trial (J-ACT) conducted by Yamaguchi et al10 According to this study, using a 0.6 mg/kg dose of intravenous recombinant tissue plasminogen activator (rtPA) in Japanese patients was safe and effective. Despite the relatively stroke high rate among Egyptian populations, 963/100,000 inhabitants, only less than 1% of stroke patients receive intravenous thrombolysis. A major reason for this is the drug cost.11,12 Low-dose regimens (0.6 mg/kg) use will lower the economic burden of thrombolytic therapy in the community and will greatly promote the implementation of this therapy in Egypt. Our study aim was to assess the outcome and safety of alteplase low dose in comparison to the standard-dose regimen in AIS treatment in Egypt.  相似文献   
12.
AimsSelf-expanding metal stents provide rapid improvement of dysphagia in oesophageal cancer but are associated with complications. The aim of the present study was to test the effectiveness of an alternative treatment of combining biodegradable stents with radiotherapy.Materials and methodsA Simon two-stage single-arm prospective phase II trial design was used to determine the efficacy of biodegradable stents plus radiotherapy in patients with dysphagia caused by oesophagus cancer who were unsuitable for radical treatment. Fourteen patients were recruited and data from 12 were included in the final analyses.ResultsFive of 12 patients met the primary end point: one stent-related patient death; four further interventions for dysphagia within 16 weeks of stenting (41.7%, 95% confidence interval 15.2–72.3%). The median time to a 10-point deterioration of quality of life was 2.7 weeks. Nine patients died within 52 weeks of registration. The median time to death from any cause was 15.0 weeks (95% confidence interval 9.6–not reached).ConclusionThe high re-intervention observed, which met the pre-defined early stopping criteria, meant that the suggested alternative treatment was not sufficiently effective to be considered for a larger scale trial design. Further work is needed to define the place of biodegradable stents in the management of malignant oesophageal strictures.  相似文献   
13.
14.

Objective

The frailty index has been linked to adverse outcomes after surgical procedures. In this study, we evaluated the association between frailty index and outcomes after elective lower extremity bypass (LEB) for lower extremity ischemia.

Methods

The American College of Surgeons National Surgical Quality Improvement Program data set (2005-2012) was used to identify patients who underwent elective LEB using diagnostic and procedure Current Procedural Terminology codes. Modified frailty index (mFI) scores, derived from the Canadian Study of Health and Aging, were categorized into three groups: low, medium, and high. Association of mFI with 30-day postoperative death (POD), myocardial infarction (MI), cardiopulmonary events (CPEs), deep tissue surgical site infection (SSI), and graft failure (GF) was evaluated. Both univariate and multivariable regression analyses—adjusted for age, sex, American Society of Anesthesiologists class, body mass index, and creatinine levels—were used to assess the effect of frailty on each outcome.

Results

Of 12,677 patients (mean age, 67.7 ± 11.1 years) identified who underwent elective LEB, POD occurred in 265 (2.1% overall). Postoperative MI, SSI, CPEs, and GF occurred in 1.6%, 2.5%, 3.1%, and 4.3%, respectively. The mean mFI of the entire sample was 0.3 ± 0.1. Adjusted odds ratio for development of any morbidity in the group with the highest mFI was 1.36 (95% confidence interval, 1.08-1.72; P = .010) compared with the low frailty group. Patients with higher mFI were more likely to develop MI and CPEs but not SSI or GF. Univariate and multivariable analyses showed a significantly increased risk of POD among those in the highest mFI tertile. Female sex and age, increased American Society of Anesthesiologists class and creatinine levels, and decreased body mass index independently predicted increased mortality. The addition of categorical mFI improved models with these variables.

Conclusions

Higher mFI is independently associated with higher mortality and morbidity. Preoperative mFI assessment may be considered an additional screening tool for risk stratification among patients undergoing LEB.  相似文献   
15.

Background and aims

There is controversy on the potentially benign nature of metabolically healthy obesity (MHO), i.e., obese persons with few or no metabolic abnormalities. So far, associations between MHO and coronary artery calcification (CAC), a measure of subclinical atherosclerosis, have mainly been studied cross-sectionally in Asian populations. We assessed cross-sectional and longitudinal MHO CAC associations in a Caucasian population.

Methods and results

In the Heinz Nixdorf Recall Study, a population-based cohort study in Germany, CAC was assessed by electron-beam tomography at baseline and at 5-year follow-up. For cross-sectional and longitudinal analyses, we included 1585 participants free of coronary heart disease at baseline, with CAC measurements at baseline and at follow-up, and with either normal weight (BMI 18.5–24.9 kg/m2) or obesity (BMI ≥30.0 kg/m2) at baseline. We used four definitions of MHO. In our main analysis, we defined obese persons as metabolically healthy if they met ≤1 of the NCEP ATP III criteria for the definition of the metabolic syndrome – waist circumference was not taken into account because of collinearity with BMI.Persons with MHO had a higher prevalence of CAC than metabolically healthy normal weight (MHNW) persons (prevalence ratio = 1.59 (95% confidence interval 1.38–1.84) for the main analysis). Persons with MHO had slightly larger odds of CAC progression than persons with MHNW (odds ratios ranged from 1.17 (0.69–1.99) to 1.48 (1.02–2.13) depending on MHO definition and statistical approach).

Conclusion

Our analyses on MHO CAC associations add to the evidence that MHO is not a purely benign health condition.  相似文献   
16.
17.

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   
18.

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   
19.

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   
20.

Introduction

There are limited randomized data comparing radical cystectomy (RC) with bladder-sparing tri-modality therapy (TMT) in the treatment of muscle-invasive bladder cancer (MIBC). Both strategies are thought to have similar survival outcomes with different morbidity profiles. We compare the effectiveness of TMT and RC using decision-analytic modeling and the endpoint of quality-adjusted life years (QALYs).

Patients and Methods

Using a Markov model, we simulated the lifetime outcomes after TMT versus RC ± neoadjuvant chemotherapy for 67-year-old patients with clinical stage T2-T4aN0M0 MIBC. Model probabilities and utilities were extracted from the literature. The incremental effectiveness was reported in QALYs and sensitivity analyses were performed.

Results

For all patients with MIBC, although the model showed identical survival, TMT was the most effective strategy with an incremental gain of 0.59 QALYs over RC (7.83 vs. 7.24 QALYs, respectively). When limiting the model to favorable, contemporary cohorts in both the TMT and RC strategies, TMT remained more effective with an incremental gain of 1.61 QALYs (9.37 vs. 7.76 QALYs, respectively). One-way sensitivity analyses demonstrated the model was sensitive to the quality of life parameters (ie, the utilities) for RC and TMT. When testing the 95% confidence interval of the RC utility parameter the model demonstrated an incremental gain with TMT from ?0.54 to 4.23 QALYs. Probabilistic sensitivity analysis demonstrated that TMT was more effective than RC for 63% of model iterations.

Conclusions

This modeling study found that treatment of MIBC with organ-sparing TMT in appropriately-selected patients may result in a gain of QALYs relative to RC.  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