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   201891篇
  免费   7337篇
  国内免费   2358篇
耳鼻咽喉   1933篇
儿科学   6934篇
妇产科学   3167篇
基础医学   22037篇
口腔科学   5610篇
临床医学   14589篇
内科学   36521篇
皮肤病学   3333篇
神经病学   12809篇
特种医学   4493篇
外国民族医学   4篇
外科学   29052篇
综合类   13565篇
现状与发展   5篇
一般理论   6篇
预防医学   15467篇
眼科学   3767篇
药学   20488篇
  33篇
中国医学   10255篇
肿瘤学   7518篇
  2023年   1359篇
  2022年   1721篇
  2021年   3790篇
  2020年   2611篇
  2019年   14077篇
  2018年   13760篇
  2017年   6868篇
  2016年   2312篇
  2015年   2184篇
  2014年   5275篇
  2013年   7090篇
  2012年   4871篇
  2011年   5031篇
  2010年   4099篇
  2009年   3999篇
  2008年   4729篇
  2007年   5884篇
  2006年   5923篇
  2005年   5524篇
  2004年   4405篇
  2003年   4419篇
  2002年   4041篇
  2001年   3981篇
  2000年   4011篇
  1999年   3604篇
  1998年   3489篇
  1997年   2879篇
  1996年   2616篇
  1995年   2986篇
  1994年   2758篇
  1993年   2170篇
  1992年   1759篇
  1991年   1732篇
  1990年   1445篇
  1989年   1168篇
  1988年   1197篇
  1987年   1123篇
  1985年   5503篇
  1984年   7365篇
  1983年   5880篇
  1982年   6313篇
  1981年   5764篇
  1980年   4956篇
  1979年   4989篇
  1978年   4089篇
  1977年   3072篇
  1976年   3540篇
  1975年   2747篇
  1974年   2526篇
  1973年   2235篇
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
101.
A high-order, well-balanced, positivity-preserving quasi-Lagrange moving mesh DG method is presented for the shallow water equations with non-flat bottom topography. The well-balance property is crucial to the ability of a scheme to simulate perturbation waves over the lake-at-rest steady state such as waves on a lake or tsunami waves in the deep ocean. The method combines a quasi-Lagrange moving mesh DG method, a hydrostatic reconstruction technique, and a change of unknown variables. The strategies in the use of slope limiting, positivity-preservation limiting, and change of variables to ensure the well-balance and positivity-preserving properties are discussed. Compared to rezoning-type methods, the current method treats mesh movement continuously in time and has the advantages that it does not need to interpolate flow variables from the old mesh to the new one and places no constraint for the choice of a update scheme for the bottom topography on the new mesh. A selection of one- and two-dimensional examples are presented to demonstrate the well-balance property, positivity preservation, and high-order accuracy of the method and its ability to adapt the mesh according to features in the flow and bottom topography.  相似文献   
102.
103.
104.
Syphilis is a sexually transmitted disease caused by Treponema pallidum. Syphilitic aortitis might coexist in a dysfunctional aortic valve, but the etiology remains unclear, because microbiological diagnosis is difficult. A 62-year-old man with low-grade fever was diagnosed with aortitis and infective endocarditis, due to Treponema pallidum infection, using polymerase chain reaction analysis. This case suggests that syphilis might cause infective endocarditis.  相似文献   
105.
艾灸作为中医学最古老的疗法之一,作用多样,应用广泛,疗效显著。随着科技的发展,人们对灸法的认识逐渐深入,其中艾烟的相关研究也硕果累累,其安全性广受关注。通过对艾烟作用和安全性评价研究中取得的成果进行归纳分析,以期为艾灸临床安全应用提供指导。  相似文献   
106.
107.
108.

Background

Pump speed optimization in patients implanted with a ventricular assist device represents a major challenge during the follow-up period. We present our findings on whether combined invasive hemodynamic ramp tests and cardiopulmonary exercise testing (CPX) can help optimize patient management.

Methods

Eighteen patients implanted with a HeartMate 3 (HM3) device underwent ramp tests with right heart catheterization (including central venous pressure [CVP], pulmonary artery pressure, pulmonary capillary wedge pressure [PCWP], and blood pressure) and echocardiography. Data were recorded at up to 4 speed settings. Speed changes were in steps of 200 revolutions/min (rpm). Evaluation of functional capacity by CPX was conducted according to the modified Bruce protocol.

Results

Only 30% of patients had normal PCWPs at their original rpm settings. In going from lowest to highest speeds, cardiac output improved by 0.25 ± 0.35 L/min/step (total change, 1.28 ± 0.3 L/min), and PCWP decreased by 1.9 ± 0.73 mm Hg/step (total change, 6 ± 1.6 mm Hg). CVP and systolic blood pressure did not change significantly with rpm. The rpm assessment was adjusted based on test results to achieve CVPs and PCWPs as close to normal limits as possible, which was feasible in all patients. On CPX, all patients demonstrated good performance (peak VO2, 16.8 ± 3.5 mL/kg/min).

Conclusion

Hemodynamic ramp testing provides an objective means of optimizing rpm, and has the potential to provide good exercise tolerance.  相似文献   
109.
110.
BackgroundAlthough there are robust data about the pathophysiology and prognostic implications of left ventricular (LV) systolic dysfunction in patients with acquired heart disease, similar prognostic data about LV systolic dysfunction are sparse in the tetralogy of Fallot (TOF) population. The purpose of this study was to perform a meta-analysis of all studies that assessed the relationship between LV ejection fraction (LVEF) and cardiovascular adverse events (CAEs) defined as death, aborted sudden death, or sustained ventricular tachycardia.MethodsWe used random-effects models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs).ResultsOf the 1,809 citations, 7 studies with 2,854 patients (age 28 ± 4 years) were included. During 5.6 ± 3.4 years' follow-up, there were 82 deaths, 17 aborted sudden cardiac deaths, and 56 sustained ventricular tachycardia events. Overall, CAEs occurred in 5.1% (144 patients). As a continuous variable, LVEF was a predictor of CAE (HR 1.29, 95% CI, 1.09-1.53, P = 0.001) per 5% decrease in LVEF. Similarly, LVEF < 40% was also a predictor of CAE (HR 3.22, 95% CI, 2.16-4.80, P < 0.001).ConclusionsLV systolic dysfunction was an independent predictor of CAE, and we observed a 30% increase in the risk of CAE for every 5% decrease in LVEF, and a 3-fold increase in the risk of CAE in patients with LVEF <40% compared with other patients. These findings underscore the importance of incorporating LV systolic function in clinical risk stratification of patients with TOF and the need to explore new treatment options to address this problem.  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