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   50131篇
  免费   3237篇
  国内免费   160篇
耳鼻咽喉   657篇
儿科学   1427篇
妇产科学   862篇
基础医学   5968篇
口腔科学   805篇
临床医学   5108篇
内科学   10862篇
皮肤病学   863篇
神经病学   4652篇
特种医学   2006篇
外国民族医学   1篇
外科学   8815篇
综合类   477篇
一般理论   48篇
预防医学   3137篇
眼科学   821篇
药学   3055篇
中国医学   45篇
肿瘤学   3919篇
  2023年   249篇
  2022年   416篇
  2021年   1087篇
  2020年   629篇
  2019年   1110篇
  2018年   1313篇
  2017年   958篇
  2016年   996篇
  2015年   1178篇
  2014年   1829篇
  2013年   2335篇
  2012年   3767篇
  2011年   3913篇
  2010年   2204篇
  2009年   1880篇
  2008年   3428篇
  2007年   3613篇
  2006年   3582篇
  2005年   3487篇
  2004年   3350篇
  2003年   3116篇
  2002年   2878篇
  2001年   399篇
  2000年   298篇
  1999年   423篇
  1998年   571篇
  1997年   466篇
  1996年   353篇
  1995年   348篇
  1994年   332篇
  1993年   271篇
  1992年   217篇
  1991年   208篇
  1990年   181篇
  1989年   165篇
  1988年   166篇
  1987年   147篇
  1986年   139篇
  1985年   145篇
  1984年   184篇
  1983年   182篇
  1982年   203篇
  1981年   179篇
  1980年   125篇
  1979年   91篇
  1978年   79篇
  1977年   73篇
  1976年   44篇
  1975年   33篇
  1974年   44篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
1.
2.
3.
Secondary tricuspid regurgitation (TR) caused by right ventricular enlargement in the setting of left heart disease/pulmonary hypertension has been well described. In contrast, that associated with right atrial enlargement—atrial functional TR (AF‐TR)—remains largely underappreciated. AF‐TR most often occurs in the setting of lone atrial fibrillation, although it is also seen in its absence (idiopathic AF‐TR). Several recent studies have found that the prevalence, hemodynamic significance, and prognosis of AF‐TR are not inconsequential, suggesting increased physician awareness of this novel clinical entity is warranted. This article discusses the pathogenesis, echocardiographic findings, and treatment of this underappreciated cause of secondary TR.  相似文献   
4.
5.

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   
6.
A comparative study involving bimetallic nickel catalysts designed from disubstituted N,N,N′,N′‐tetra(diphenylphosphanylmethyl)benzene diamine bridging ligands is reported. Catalyst behavior is explored in the Kumada catalyst‐transfer polymerization (KCTP) using poly(3‐hexylthiophene) (P3HT) as the model system. The success of a controlled polymerization is monitored by analyzing monomer conversion, degree of polymerization, end‐group identity, and molecular weight distribution. The characterization of P3HT obtained from KCTP initiated with the bimetallic catalysts shows chain‐growth behavior; however, the presence of Br/Br end‐groups and broader molecular weight distribution reveals a reduced controlled polymerization compared to the commonly employed Ni(dppp)Cl2. The observed increase in intermolecular chain transfer and termination processes in KCTP initiation with the bimetallic catalysts can be attributed to a weaker Ni(0)‐π‐aryl complex interaction, which is caused by increased steric crowding of the coordination sphere.  相似文献   
7.
8.
9.
10.
In the USA, the Black Church is among the most important institutions in the Black community, offering numerous spiritual, social and health benefits. Yet, the presence of homonegativity in many Black Churches may mitigate those effects for gay Black youth. This research examines the role of the Church in the lives of gay and bisexual Black youth to understand how they reconcile any tension between their religious and sexual identities. Through interviews with pastors of Black churches (n = 21) and young Black men who have sex with men (n = 30), we explored homonegativity and young men’s experiences within the Black Church. Findings reveal that despite the prevalence of homonegativity within Black churches, religious involvement remains important for young men and many remain involved in non-affirming churches. The importance of the Church for young men stems from their significant involvement as youth and the integration of religion, family and community. Young men may not be able to leave their religious homes as readily as other gay youth given the cultural relevance of the Church. As a result, young men made attempts to conceal their sexuality in church to avoid shame and gossip and find opportunities to balance their sexuality and religiosity.  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