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   1342258篇
  免费   112999篇
  国内免费   6367篇
耳鼻咽喉   16744篇
儿科学   43101篇
妇产科学   36598篇
基础医学   184134篇
口腔科学   36397篇
临床医学   121308篇
内科学   279285篇
皮肤病学   31923篇
神经病学   110914篇
特种医学   55629篇
外国民族医学   274篇
外科学   210877篇
综合类   31617篇
现状与发展   2篇
一般理论   416篇
预防医学   106959篇
眼科学   28130篇
药学   93949篇
  5篇
中国医学   2231篇
肿瘤学   71131篇
  2018年   13446篇
  2017年   10693篇
  2016年   12869篇
  2015年   14372篇
  2014年   20046篇
  2013年   29869篇
  2012年   36458篇
  2011年   39110篇
  2010年   24493篇
  2009年   23998篇
  2008年   36568篇
  2007年   38981篇
  2006年   40077篇
  2005年   38650篇
  2004年   36912篇
  2003年   36005篇
  2002年   33991篇
  2001年   66175篇
  2000年   68030篇
  1999年   56710篇
  1998年   16775篇
  1997年   15061篇
  1996年   16042篇
  1995年   16273篇
  1994年   15126篇
  1993年   14180篇
  1992年   47169篇
  1991年   45808篇
  1990年   44040篇
  1989年   41891篇
  1988年   38825篇
  1987年   38137篇
  1986年   35913篇
  1985年   34697篇
  1984年   26403篇
  1983年   22149篇
  1982年   13874篇
  1981年   12481篇
  1980年   11739篇
  1979年   23581篇
  1978年   17102篇
  1977年   14409篇
  1976年   13195篇
  1975年   13739篇
  1974年   16113篇
  1973年   15433篇
  1972年   14193篇
  1971年   13051篇
  1970年   11895篇
  1969年   11126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