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   2349988篇
  免费   180577篇
  国内免费   7741篇
耳鼻咽喉   31890篇
儿科学   77404篇
妇产科学   66452篇
基础医学   331812篇
口腔科学   65906篇
临床医学   207099篇
内科学   468675篇
皮肤病学   53471篇
神经病学   188979篇
特种医学   94332篇
外国民族医学   617篇
外科学   365024篇
综合类   52514篇
现状与发展   3篇
一般理论   683篇
预防医学   182860篇
眼科学   52500篇
药学   171569篇
  6篇
中国医学   4257篇
肿瘤学   122253篇
  2018年   22798篇
  2016年   20739篇
  2015年   23434篇
  2014年   32654篇
  2013年   49382篇
  2012年   63405篇
  2011年   67965篇
  2010年   41639篇
  2009年   40071篇
  2008年   64520篇
  2007年   69489篇
  2006年   70915篇
  2005年   69110篇
  2004年   66301篇
  2003年   64524篇
  2002年   62315篇
  2001年   108056篇
  2000年   111248篇
  1999年   93735篇
  1998年   27855篇
  1997年   25004篇
  1996年   25849篇
  1995年   25339篇
  1994年   23899篇
  1993年   22262篇
  1992年   77405篇
  1991年   75853篇
  1990年   73871篇
  1989年   70825篇
  1988年   66034篇
  1987年   64740篇
  1986年   61584篇
  1985年   59077篇
  1984年   44723篇
  1983年   38241篇
  1982年   23571篇
  1981年   21062篇
  1980年   19753篇
  1979年   41450篇
  1978年   29679篇
  1977年   25294篇
  1976年   23551篇
  1975年   25325篇
  1974年   29839篇
  1973年   28618篇
  1972年   26823篇
  1971年   24849篇
  1970年   22907篇
  1969年   21851篇
  1968年   20528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.
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   
6.
7.
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   
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