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   2385061篇
  免费   183895篇
  国内免费   10347篇
耳鼻咽喉   32066篇
儿科学   77858篇
妇产科学   66945篇
基础医学   336043篇
口腔科学   66482篇
临床医学   211578篇
内科学   474237篇
皮肤病学   53782篇
神经病学   191053篇
特种医学   95541篇
外国民族医学   640篇
外科学   368707篇
综合类   58193篇
现状与发展   15篇
一般理论   685篇
预防医学   184908篇
眼科学   53340篇
药学   175265篇
  21篇
中国医学   6124篇
肿瘤学   125820篇
  2018年   24012篇
  2016年   21800篇
  2015年   25104篇
  2014年   34606篇
  2013年   51065篇
  2012年   66098篇
  2011年   70791篇
  2010年   43367篇
  2009年   41448篇
  2008年   66434篇
  2007年   71412篇
  2006年   72668篇
  2005年   70960篇
  2004年   67541篇
  2003年   65712篇
  2002年   63278篇
  2001年   108744篇
  2000年   112055篇
  1999年   94614篇
  1998年   28441篇
  1997年   25640篇
  1996年   26325篇
  1995年   25787篇
  1994年   24309篇
  1993年   22534篇
  1992年   77651篇
  1991年   76107篇
  1990年   74084篇
  1989年   71025篇
  1988年   66192篇
  1987年   64884篇
  1986年   61702篇
  1985年   59153篇
  1984年   44783篇
  1983年   38293篇
  1982年   23591篇
  1981年   21091篇
  1980年   19765篇
  1979年   41467篇
  1978年   29689篇
  1977年   25305篇
  1976年   23564篇
  1975年   25326篇
  1974年   29827篇
  1973年   28614篇
  1972年   26817篇
  1971年   24848篇
  1970年   22906篇
  1969年   21851篇
  1968年   20527篇
排序方式: 共有10000条查询结果,搜索用时 0 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