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   2440268篇
  免费   196203篇
  国内免费   8236篇
耳鼻咽喉   32050篇
儿科学   80229篇
妇产科学   68351篇
基础医学   340555篇
口腔科学   66781篇
临床医学   221321篇
内科学   490948篇
皮肤病学   57877篇
神经病学   202255篇
特种医学   96197篇
外国民族医学   710篇
外科学   370846篇
综合类   58180篇
现状与发展   4篇
一般理论   848篇
预防医学   195845篇
眼科学   54132篇
药学   171263篇
  6篇
中国医学   5014篇
肿瘤学   131295篇
  2018年   26596篇
  2017年   20585篇
  2016年   23930篇
  2015年   26771篇
  2014年   37733篇
  2013年   56433篇
  2012年   72764篇
  2011年   77917篇
  2010年   47300篇
  2009年   45589篇
  2008年   72355篇
  2007年   76789篇
  2006年   77980篇
  2005年   75726篇
  2004年   72342篇
  2003年   69539篇
  2002年   66596篇
  2001年   118732篇
  2000年   121735篇
  1999年   101367篇
  1998年   29935篇
  1997年   26949篇
  1996年   27688篇
  1995年   27088篇
  1994年   24925篇
  1993年   23446篇
  1992年   80342篇
  1991年   77543篇
  1990年   74470篇
  1989年   70978篇
  1988年   65528篇
  1987年   64197篇
  1986年   60330篇
  1985年   57976篇
  1984年   44230篇
  1983年   37384篇
  1982年   23163篇
  1981年   20715篇
  1980年   19293篇
  1979年   39608篇
  1978年   28381篇
  1977年   23764篇
  1976年   22052篇
  1975年   22836篇
  1974年   27145篇
  1973年   26117篇
  1972年   24378篇
  1971年   22336篇
  1970年   20857篇
  1969年   19404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.
7.
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   
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