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   1508129篇
  免费   108039篇
  国内免费   2071篇
耳鼻咽喉   19944篇
儿科学   49608篇
妇产科学   43415篇
基础医学   225284篇
口腔科学   41061篇
临床医学   137581篇
内科学   292528篇
皮肤病学   32529篇
神经病学   119452篇
特种医学   56527篇
外国民族医学   302篇
外科学   217593篇
综合类   32302篇
现状与发展   4篇
一般理论   713篇
预防医学   121317篇
眼科学   33918篇
药学   109854篇
  34篇
中国医学   2703篇
肿瘤学   81570篇
  2019年   12087篇
  2018年   16892篇
  2017年   12777篇
  2016年   14214篇
  2015年   16365篇
  2014年   22310篇
  2013年   34117篇
  2012年   45312篇
  2011年   47635篇
  2010年   28443篇
  2009年   27041篇
  2008年   44766篇
  2007年   48077篇
  2006年   47528篇
  2005年   46291篇
  2004年   44499篇
  2003年   42479篇
  2002年   41017篇
  2001年   66236篇
  2000年   67594篇
  1999年   56945篇
  1998年   15923篇
  1997年   14465篇
  1996年   14719篇
  1995年   13896篇
  1994年   12976篇
  1993年   12142篇
  1992年   44761篇
  1991年   44326篇
  1990年   42988篇
  1989年   41697篇
  1988年   38544篇
  1987年   37629篇
  1986年   35927篇
  1985年   34034篇
  1984年   25772篇
  1983年   22481篇
  1982年   13340篇
  1979年   24534篇
  1978年   17942篇
  1977年   15013篇
  1976年   13896篇
  1975年   15116篇
  1974年   18370篇
  1973年   18147篇
  1972年   17099篇
  1971年   16014篇
  1970年   15169篇
  1969年   14184篇
  1968年   13374篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
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