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   1024篇
  免费   100篇
  国内免费   3篇
耳鼻咽喉   1篇
儿科学   31篇
妇产科学   20篇
基础医学   159篇
口腔科学   3篇
临床医学   125篇
内科学   228篇
皮肤病学   6篇
神经病学   74篇
特种医学   17篇
外科学   147篇
综合类   8篇
一般理论   2篇
预防医学   179篇
眼科学   10篇
药学   62篇
中国医学   1篇
肿瘤学   54篇
  2023年   10篇
  2022年   22篇
  2021年   39篇
  2020年   27篇
  2019年   35篇
  2018年   38篇
  2017年   22篇
  2016年   30篇
  2015年   40篇
  2014年   40篇
  2013年   57篇
  2012年   79篇
  2011年   100篇
  2010年   40篇
  2009年   32篇
  2008年   57篇
  2007年   74篇
  2006年   61篇
  2005年   64篇
  2004年   47篇
  2003年   67篇
  2002年   45篇
  2001年   10篇
  2000年   4篇
  1999年   7篇
  1998年   11篇
  1997年   10篇
  1996年   7篇
  1995年   12篇
  1994年   4篇
  1993年   4篇
  1992年   5篇
  1991年   2篇
  1990年   2篇
  1989年   2篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1984年   3篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1974年   3篇
  1972年   1篇
  1971年   1篇
  1965年   1篇
排序方式: 共有1127条查询结果,搜索用时 15 毫秒
1.
This article reports findings from a longitudinal survey of very elderly people living at home in London. The research aimed to identify social, psychological and physical characteristics associated with positive ageing and successful survival in the community in later life and its converse—negative ageing—as well as the associated policy implications. Associations with psychiatric morbidity, measured using the General Health Questionnaire, among sample members without cognitive impairment between the baseline interviews in 1987 and at follow-up, two and a half years later in 1990, are reported. Twenty-five per cent of survivors scored over the threshold of the GHQ in 1987 and 30% scored over the threshold in 1990. Half of those with a score over the threshold in 1990 also scored over the threshold in 1987. Hierarchical regression (using residualized change analysis) was used to estimate the effects of the independent variables on changes in psychiatric morbidity. The most significant predictor of psychiatric morbidity (GHQ score) in 1990 was baseline GHQ score, followed by health and functional status scores. Health and functional status were also the strongest predictors of baseline (1987) GHQ scores. The uniqueness of the study lies in the collection of follow-up data on a sample of very elderly people, given that most surveys are corss-sectional and contain too few people aged 85+ to merit separate analysis. It contributes to the small body of literature on outcome of depression. The lack of consistent associations with recovery from psychiatric morbidity in the literature enhances the importance of studies aiming to identify factors associated with different outcomes.  相似文献   
2.
The biliary excretion of radioactivity after intravenous [3H]25-hydroxyvitamin D3 was studied in nine patients with T-tube bile drainage. The mean +/- SD 24-hr radioactivity excretion in T-tube bile expressed as a percentage of the administered dose was 6.7 +/- 2.9%; after correction for incomplete bile collection, the value obtained was 16.0 +/- 11.1%. Chloroform solubility of biliary radioactivity increased from 27.4 +/- 8.9% to 72.9 +/- 10.1% following incubation with beta-glucuronidase. High-performance liquid chromatographic analysis of chloroform extracts of bile revealed that most of the eluted radioactivity was more polar than [3H]25-hydroxyvitamin D3. No free [3H]25-hydroxyvitamin D3 was demonstrated. Thus in man, most of the biliary radioactivity excreted following [3H]25-hydroxyvitamin D3 is in the form of water-soluble compounds, mainly glucuronides. However, our results suggest that glucuronides of metabolites other than 25-OHD3 are predominantly formed.  相似文献   
3.
We have developed a transient expression system for the protist Physarum polycephalum based on firefly luciferase. We demonstrate the utility of this system for comparing the activities of different promoters in Physarum amoebae, and also for detecting genetic elements that affect the level of gene expression. This system is likely to facilitate improvements in the stable transformation of this organism.  相似文献   
4.
5.
6.
7.
8.
9.
10.
Neutrophils are the body’s primary defenders against invading pathogens. These cells migrate to loci of infection where they engulf micro-organisms and subject them to an array of reactive oxygen species and antimicrobial proteins to effect killing. Spent neutrophils subsequently undergo apoptosis and are cleared by macrophages, thereby resolving the inflammatory episode. Neutrophils contain high concentrations of vitamin C (ascorbate) and this is thought to be essential for their function. This may be one mechanism whereby vitamin C enhances immune function. The aim of our study was to assess the effect of dietary supplementation with vitamin C-rich SunGold kiwifruit on four important functions of neutrophils: chemotaxis, oxidant generation, extracellular trap formation, and apoptosis. Fourteen young men (aged 18–30 years) with suboptimal plasma vitamin C status (<50 μmol/L) were supplemented for four weeks with two SunGold kiwifruit/day. Plasma vitamin C status was monitored weekly and neutrophil vitamin C levels were assessed at baseline and post-intervention. Neutrophil function assays were carried out on cells isolated at baseline and post-intervention. Plasma vitamin C levels increased to >70 μmol/L (p < 0.001) within one week of supplementation and there was a significant increase in neutrophil vitamin C status following four weeks’ intervention (p = 0.016). We observed a significant 20% increase in neutrophil chemotaxis post-intervention (p = 0.041) and also a comparable increase in oxidant generation (p = 0.031). Supplementation did not affect neutrophil extracellular trap formation or spontaneous apoptosis. Our data indicate that supplementation with vitamin C-rich kiwifruit is associated with improvement of important neutrophil functions, which would be expected to translate into enhanced immunity.  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