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   2559407篇
  免费   195376篇
  国内免费   4173篇
耳鼻咽喉   36296篇
儿科学   85352篇
妇产科学   73948篇
基础医学   368468篇
口腔科学   74565篇
临床医学   223568篇
内科学   495905篇
皮肤病学   54622篇
神经病学   204064篇
特种医学   100927篇
外国民族医学   793篇
外科学   390742篇
综合类   59817篇
现状与发展   4篇
一般理论   807篇
预防医学   195692篇
眼科学   59641篇
药学   193920篇
  4篇
中国医学   4782篇
肿瘤学   135039篇
  2018年   23868篇
  2015年   23920篇
  2014年   32988篇
  2013年   50326篇
  2012年   68581篇
  2011年   73009篇
  2010年   43057篇
  2009年   40896篇
  2008年   70138篇
  2007年   74912篇
  2006年   76180篇
  2005年   74273篇
  2004年   72498篇
  2003年   69684篇
  2002年   68522篇
  2001年   115750篇
  2000年   119257篇
  1999年   101304篇
  1998年   28515篇
  1997年   25756篇
  1996年   25852篇
  1995年   24864篇
  1994年   23414篇
  1993年   21984篇
  1992年   83434篇
  1991年   81588篇
  1990年   80225篇
  1989年   77733篇
  1988年   72347篇
  1987年   71382篇
  1986年   67942篇
  1985年   65285篇
  1984年   49002篇
  1983年   42576篇
  1982年   25123篇
  1981年   22319篇
  1980年   21040篇
  1979年   46977篇
  1978年   32868篇
  1977年   27995篇
  1976年   26476篇
  1975年   28416篇
  1974年   34205篇
  1973年   33009篇
  1972年   30917篇
  1971年   28875篇
  1970年   26762篇
  1969年   25306篇
  1968年   23449篇
  1967年   21018篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.

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   
2.
3.
4.
5.
6.
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.  相似文献   
7.
8.
9.
10.
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