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   15234篇
  免费   1443篇
  国内免费   2篇
  16679篇
  2023年   50篇
  2022年   148篇
  2021年   294篇
  2020年   148篇
  2019年   223篇
  2018年   281篇
  2017年   238篇
  2016年   499篇
  2015年   782篇
  2014年   828篇
  2013年   1006篇
  2012年   1269篇
  2011年   1131篇
  2010年   738篇
  2009年   722篇
  2008年   906篇
  2007年   931篇
  2006年   860篇
  2005年   846篇
  2004年   790篇
  2003年   789篇
  2002年   740篇
  2001年   141篇
  2000年   87篇
  1999年   157篇
  1998年   195篇
  1997年   142篇
  1996年   118篇
  1995年   125篇
  1994年   114篇
  1993年   111篇
  1992年   100篇
  1991年   81篇
  1990年   78篇
  1989年   65篇
  1988年   65篇
  1987年   50篇
  1986年   63篇
  1985年   68篇
  1984年   83篇
  1983年   46篇
  1982年   76篇
  1981年   56篇
  1980年   62篇
  1979年   41篇
  1977年   34篇
  1976年   23篇
  1974年   30篇
  1972年   22篇
  1971年   22篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
11.
12.
13.
To cope with changes in the environment, organisms not only show behavioural but also phenotypic adjustments. This is well established for the digestive tract. Here we present a first case of birds adjusting their flight machinery in response to predation risk. In an indoor experiment, ruddy turnstones Arenaria interpres were subjected to an unpredictable daily appearance of either a raptor or a small gull (as a control). Ruddy turnstones experiencing threat induced by a flying raptor model, longer than after similar passage by the gull model, refrained from feeding after this disturbance. Pectoral muscle mass, but not lean mass, responded in a course of a few days to changes in the perceived threat of predation. Pectoral muscle mass increased after raptor scares. Taking the small increases in body mass into account, pectoral muscle mass was 3.6% higher than aerodynamically predicted for constant flight performance. This demonstrates that perceived risk factors may directly affect organ size.  相似文献   
14.
Book Review     
International Journal of Primatology -  相似文献   
15.
An antigen making a major contribution to the immune response to Drosophila melanogaster chromatin resides primarily on a nonhistone charge-class family of proteins of Mr 74,000. Immunofluorescence detects this antigen at interbands, puffs and diffuse bands of D. melanogaster salivary chromosomes isolated without exposure to acid fixatives, and on nucleoplasmic ribonucleoprotein droplets. In the electron microscope, gold labelling reveals the binding of monoclonal antibodies specific for the antigen at chromosomal loci generally bearing putative ribonucleoprotein (RNP) particles. However, the locus 3C 11–12 is remarkable in that it bears putative RNP particles but is virtually unlabelled, suggesting protein specificity at different active loci.  相似文献   
16.
17.
18.
An automated follow-up register for the detection of iatrogenic thyroid disease has been established as a joint venture between the general practitioners in the north-east of Scotland and the thyroid clinic of Aberdeen General Hospitals.The data-processing operations in the system are handled by an International Computers Limited 4/50 computer. Patients are followed up at predetermined intervals and the system has been designed to process, screen, and store clinical and biochemical follow-up data and report results to the patients, general practitioners, and the hospital records department.  相似文献   
19.
Purine Ribonucleosidase g from Aspergillus foetidus   总被引:1,自引:0,他引:1  
Nucleosidase g was prepared by growing Aspergillus foetidus on bran, and was purified by passage through a diethylaminoethyl-Sephadex column. The enzyme acted on the purine ribosides (except xanthosine) and on their 5'-phosphates. Action on the latter was a good means for preparing ribose-5-phosphate.  相似文献   
20.
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