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   1345258篇
  免费   113359篇
  国内免费   6831篇
耳鼻咽喉   16746篇
儿科学   43062篇
妇产科学   36657篇
基础医学   184273篇
口腔科学   36416篇
临床医学   121527篇
内科学   279577篇
皮肤病学   31948篇
神经病学   110744篇
特种医学   55760篇
外国民族医学   275篇
外科学   211214篇
综合类   32912篇
现状与发展   3篇
一般理论   415篇
预防医学   107229篇
眼科学   28215篇
药学   94479篇
  20篇
中国医学   2661篇
肿瘤学   71315篇
  2018年   13615篇
  2017年   10912篇
  2016年   13029篇
  2015年   14617篇
  2014年   20357篇
  2013年   30131篇
  2012年   36742篇
  2011年   39448篇
  2010年   24735篇
  2009年   24310篇
  2008年   36775篇
  2007年   39177篇
  2006年   40235篇
  2005年   38796篇
  2004年   36941篇
  2003年   36061篇
  2002年   34007篇
  2001年   66177篇
  2000年   68006篇
  1999年   56682篇
  1998年   16781篇
  1997年   15067篇
  1996年   16045篇
  1995年   16270篇
  1994年   15130篇
  1993年   14165篇
  1992年   47121篇
  1991年   45767篇
  1990年   43996篇
  1989年   41839篇
  1988年   38765篇
  1987年   38098篇
  1986年   35870篇
  1985年   34644篇
  1984年   26362篇
  1983年   22113篇
  1982年   13848篇
  1981年   12449篇
  1980年   11718篇
  1979年   23546篇
  1978年   17073篇
  1977年   14387篇
  1976年   13182篇
  1975年   13722篇
  1974年   16094篇
  1973年   15396篇
  1972年   14173篇
  1971年   13036篇
  1970年   11880篇
  1969年   11102篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
In this paper we present a coupled Finite Element Method – Boundary Element Method (FEM-BEM) approach for the solution of the free-boundary axi-symmetric plasma equilibrium problem. The proposed method, obtained from an improvement of the Hagenow-Lackner coupling method, allows to efficiently model the equilibrium problem in unbounded domains by discretizing only the plasma region; the external conductors can be modelled either as 2D or 3D models, according to the problem of interest. The paper explores different iterative methods for the solution of the nonlinear Grad-Shafranov equation, such as Picard, Newton-Raphson and Newton-Krylov, in order to provide a robust and reliable tool, able to handle large-scale problems (e.g. high resolution equilibria). This method has been implemented in the FRIDA code (FRee-boundary Integro-Differential Axisimmetric – https://github. om/matteobonotto/ FRIDA), together with a suitable Adaptive Integration Technique (AIT) for the computation of the source term. FRIDA has been successfully tested and validated against experimental data from RFX-mod device, and numerical equilibria of an ITER-like device.  相似文献   
15.
16.
Maternal and Child Health Journal - Early life exposures can have an impact on a child’s developmental trajectory and children born late preterm (34–36 weeks gestational age)...  相似文献   
17.
18.
19.

Objectives

Expedient extubation after cardiac surgery has been associated with improved outcomes, leading to postoperative extubation frequently during overnight hours. However, recent evidence in a mixed medical-surgical intensive care unit population demonstrated worse outcomes with overnight extubation. This study investigated the impact of overnight extubation in a statewide, multicenter Society of Thoracic Surgeons database.

Methods

Records from 39,812 patients undergoing coronary artery bypass grafting or valve operations (2008-2016) and extubated within 24 hours were stratified according to extubation time between 06:00 and 18:00 (day) or between 18:00 and 6:00 (overnight). Outcomes including reintubation, mortality, and composite morbidity-mortality were evaluated using hierarchical regression models adjusted for Society of Thoracic Surgeons predictive risk scores. To further analyze extubation during the night, a subanalysis stratified patients into 3 groups: 06:00 to 18:00, 18:00 to 24:00, and 24:00 to 06:00.

Results

A total of 20,758 patients were extubated overnight (52.1%) and were slightly older (median age 66 vs 65 years, P < .001) with a longer duration of ventilation (4 vs 7 hours, P < .001). Day and overnight extubation were associated with equivalent operative mortality (1.7% vs 1.7%, P = .880), reintubation (3.7% vs 3.4%, P = .141), and composite morbidity-mortality (8.2% vs 8.0%, P = .314). After risk adjustment, overnight extubation was not associated with any difference in reintubation, mortality, or composite morbidity-mortality. On subanalysis, those extubated between 24:00 and 06:00 exhibited increased composite morbidity-mortality (odds ratio, 1.18; P = .001) but no difference in reintubation or mortality.

Conclusions

Extubation overnight was not associated with increased mortality or reintubation. These results suggest that in the appropriate clinical setting, it is safe to routinely extubate cardiac surgery patients overnight.  相似文献   
20.
Metabolism describes the series of chemical reactions that are concerned with the provision of energy to biological systems. They may be divided into reactions involved in energy yield (catabolism: demand exceeds supply), and energy storage (anabolism: supply exceeds demand). Regulation of these pathways is critical for homeostasis, and derangements in metabolism are seen in a wide variety of pathological processes. Understanding metabolism is key to the treatment of many diseases, notably diabetes, as well as underpinning clinical nutritional support.  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