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   2163954篇
  免费   162845篇
  国内免费   4358篇
耳鼻咽喉   29406篇
儿科学   66367篇
妇产科学   59148篇
基础医学   306704篇
口腔科学   61757篇
临床医学   192024篇
内科学   427993篇
皮肤病学   48716篇
神经病学   174644篇
特种医学   83309篇
外国民族医学   537篇
外科学   333869篇
综合类   46915篇
现状与发展   4篇
一般理论   698篇
预防医学   160852篇
眼科学   49445篇
药学   158315篇
  4篇
中国医学   4849篇
肿瘤学   125601篇
  2019年   16118篇
  2018年   23186篇
  2017年   17839篇
  2016年   20006篇
  2015年   22570篇
  2014年   31474篇
  2013年   46969篇
  2012年   63738篇
  2011年   67216篇
  2010年   39653篇
  2009年   38055篇
  2008年   63513篇
  2007年   67002篇
  2006年   68083篇
  2005年   65936篇
  2004年   63216篇
  2003年   60596篇
  2002年   58908篇
  2001年   114474篇
  2000年   117411篇
  1999年   97519篇
  1998年   25632篇
  1997年   22919篇
  1996年   23051篇
  1995年   21805篇
  1994年   19876篇
  1993年   18574篇
  1992年   74076篇
  1991年   70856篇
  1990年   68162篇
  1989年   65713篇
  1988年   60168篇
  1987年   58723篇
  1986年   54690篇
  1985年   52411篇
  1984年   38783篇
  1983年   32750篇
  1982年   18764篇
  1981年   16499篇
  1979年   34201篇
  1978年   23603篇
  1977年   19900篇
  1976年   18112篇
  1975年   19087篇
  1974年   23146篇
  1973年   22139篇
  1972年   20839篇
  1971年   19282篇
  1970年   18371篇
  1969年   17123篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.

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   
3.
4.
5.
6.
Sinus venosus atrial septal defect (SV‐ASD) usually coexists with partial anomalous pulmonary vein connection (PAPVC). It is a difficult diagnosis in transthoracic echocardiography (TTE) due to eccentric position of defects. We present a rare case of atypical anatomical variation in PAPVC, which was never described before. Two right pulmonary veins drained into superior vena cava, which overrode SV‐ASD and interatrial septum, a third pulmonary vein into the right atrium. Complete diagnosis could not be set after TTE, nor transesophageal echocardiography, whereas angio‐CT was finally conclusive. This diagnostic approach allowed the surgical planning.  相似文献   
7.
8.
9.
10.
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   
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