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   5892514篇
  免费   436453篇
  国内免费   17820篇
耳鼻咽喉   85504篇
儿科学   186259篇
妇产科学   159126篇
基础医学   855501篇
口腔科学   171945篇
临床医学   545138篇
内科学   1074686篇
皮肤病学   134897篇
神经病学   488507篇
特种医学   229739篇
外国民族医学   1781篇
外科学   877139篇
综合类   167019篇
现状与发展   25篇
一般理论   3197篇
预防医学   491774篇
眼科学   142874篇
药学   426758篇
  29篇
中国医学   15173篇
肿瘤学   289716篇
  2021年   57814篇
  2019年   60169篇
  2018年   78641篇
  2017年   60501篇
  2016年   67556篇
  2015年   79053篇
  2014年   114046篇
  2013年   180221篇
  2012年   166783篇
  2011年   178972篇
  2010年   138751篇
  2009年   136396篇
  2008年   164125篇
  2007年   178158篇
  2006年   183614篇
  2005年   177808篇
  2004年   177876篇
  2003年   167485篇
  2002年   156823篇
  2001年   237050篇
  2000年   236420篇
  1999年   209085篇
  1998年   81660篇
  1997年   74727篇
  1996年   72270篇
  1995年   67954篇
  1994年   62004篇
  1993年   57187篇
  1992年   158168篇
  1991年   152757篇
  1990年   147582篇
  1989年   143360篇
  1988年   132978篇
  1987年   130676篇
  1986年   124376篇
  1985年   120732篇
  1984年   95447篇
  1983年   83288篇
  1982年   58026篇
  1981年   53272篇
  1979年   87396篇
  1978年   65961篇
  1977年   57586篇
  1976年   53658篇
  1975年   55996篇
  1974年   65193篇
  1973年   62726篇
  1972年   59353篇
  1971年   55066篇
  1970年   51766篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
ABSTRACT

Forest workers, including loggers, foresters, and wildland firefighters, are regularly exposed to some of the most fatal occupational environments in the United States. These hazardous work environments may become even more complex and dynamic when subject to bark beetle outbreaks that have resulted in significant tree mortality. The impacts of tree death from bark beetles are significant, with the cumulative 17-year (2000–2016) footprint for bark beetle caused tree mortality estimated at 54 million acres. However, how workers think about and act in these environments is understudied. This study, therefore, approaches the issue of beetle kill and forest worker safety by examining the perspectives or workers themselves. Its contribution is to leverage ethnographic research to provide insights that can generate new research questions, better inform outreach, and ultimately improve worker safety outcomes. The resulting insights show that beetle kill was understood by workers as a hazard that increased the complexity and dynamism of the work environment, making situational awareness both more necessary and more difficult to maintain. While much research about situational awareness focuses on hazardous situations, it is suggested that building adequate situational awareness should also include broader considerations of organizational communication, as well as training and experience considered over the course of entire careers.  相似文献   
103.
Objective: The objective of this study was to gain greater insight into individuals’ quality of life (QOL) definitions, appraisals, and adaptations following spinal cord injury (SCI).

Design: A mixed-methods design, applying the Schwartz and Sprangers response shift (RS) model. RS is a cognitive process wherein, in response to a change in health status, individuals change internal standards, values, or conceptualization of QOL

Setting: Community-dwelling participants who receive medical treatment at a major Midwestern medical system and nearby Veterans’ Affairs hospital.

Participants: A purposive sample of participants with SCI (N?=?40) completed semi-structured interviews and accompanying quantitative measures.

Interventions: Not applicable.

Outcome Measures: Qualitative data were analyzed using content analysis to identify themes. Analysis of variance were performed to detect differences based on themes and QOL, well-being, and demographic and injury characteristics.

Results: Four RS themes were identified, capturing the range of participant perceptions of QOL. The themes ranged from complete RS, indicating active engagement in maintaining QOL, to awareness and comparisons redefining QOL, to a relative lack of RS. Average QOL ratings differed as a function of response shift themes. PROMIS Global Health, Anxiety, and Depression also differed as a function of RS themes.

Conclusion: The RS model contextualizes differences in QOL definitions, appraisals, and adaptations in a way standardized QOL measures alone do not.  相似文献   

104.
105.
106.
107.
108.
109.
ABSTRACT

Purpose

New instrument-based techniques for anterior chamber (AC) cell counting can offer automation and objectivity above clinician assessment. This review aims to identify such instruments and its correlation with clinician estimates.  相似文献   
110.
Abstract

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos.  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