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   2622706篇
  免费   187500篇
  国内免费   7691篇
耳鼻咽喉   34701篇
儿科学   85941篇
妇产科学   72237篇
基础医学   368459篇
口腔科学   70494篇
临床医学   237970篇
内科学   522691篇
皮肤病学   63370篇
神经病学   216714篇
特种医学   101373篇
外国民族医学   737篇
外科学   392879篇
综合类   50759篇
现状与发展   5篇
一般理论   1037篇
预防医学   198128篇
眼科学   57398篇
药学   190132篇
  8篇
中国医学   5389篇
肿瘤学   147475篇
  2021年   21207篇
  2019年   21617篇
  2018年   30420篇
  2017年   23336篇
  2016年   27108篇
  2015年   30561篇
  2014年   41833篇
  2013年   62094篇
  2012年   82864篇
  2011年   87118篇
  2010年   52486篇
  2009年   50459篇
  2008年   81033篇
  2007年   85901篇
  2006年   87494篇
  2005年   83573篇
  2004年   80404篇
  2003年   77602篇
  2002年   74759篇
  2001年   128737篇
  2000年   131654篇
  1999年   110839篇
  1998年   31583篇
  1997年   28173篇
  1996年   28396篇
  1995年   27552篇
  1994年   25215篇
  1993年   23572篇
  1992年   85371篇
  1991年   81760篇
  1990年   78954篇
  1989年   76222篇
  1988年   69622篇
  1987年   68137篇
  1986年   63701篇
  1985年   60667篇
  1984年   45071篇
  1983年   38080篇
  1982年   22576篇
  1981年   20098篇
  1979年   39079篇
  1978年   27540篇
  1977年   23345篇
  1976年   21579篇
  1975年   22899篇
  1974年   26895篇
  1973年   25455篇
  1972年   23839篇
  1971年   22047篇
  1970年   20259篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Results of an examination of 39 patients are described and critically assessed. An analysis of the resolving power of the method of ultrasonic angiography in pathological formations of major vessels of the neck is given.  相似文献   
992.
993.
994.
995.
Nonorganic failure-to-thrive is a medical-psychological disorder reflecting lack of growth in an infant without apparent physical causes. Children who fail to thrive as infants are at high risk for developmental delays, personality problems, abuse, and death. This article focuses on environmental failure-to-thrive, describing the behavioral characteristics of the nonthriving infant and the family milieu. Aspects of early environments of NOFT infants are profiled, specific intervention strategies are discussed, and recommendations regarding the promotion of intense, consistent multi-disciplinary intervention strategies are advanced.  相似文献   
996.
The behavioural and physiological consequences of social status and reciprocal fighting in resident-intruder dyads of Long Evans male rats were evaluated. Before a chronic cohabitation of 10 days, residents and intruders were individually housed for one month to increase their aggressiveness. Control animals included isolates, i.e., animals kept individually housed throughout the experiment and pair-housed rats, i.e., pairs of rats housed together from their rats in the laboratory. In 19 out of 20 dyads, a clear dominance relationship developed with an advantage to the resident in 68% of the cases. Dominants showed more exploratory activity than subordinates in a open-field test at the end of the cohabitation period; subordinates groomed longer than animals from other experimental groups. Dominants had lower pain thresholds than individually and pair-housed animals. Both dominants and subordinates had higher tyrosine hydroxylase enzymatic activities in the left adrenal than isolated and pair-housed rats. Subordinates lost body weight and had higher plasma corticosteroid concentrations than animals from the other experimental groups. In addition, they had smaller thymus glands and reduced spleen lymphocyte responses to mitogenic stimulation in vitro, in comparison to dominant animals. These results show that subordination in the dyadic resident-intruder paradigm leads to a complex syndrome of behavioural and physiological changes, some of which may be modulated by the intensity of aggressive interactions.  相似文献   
997.
998.
999.
Immunocytochemical methods have been used to examine the localisation of 3 neurofilament proteins and the calcium binding protein, calbindin D28k, in whole mount preparations of the submucous plexus in the Wistar rat. Neurofilament-M (160 kDA protein) was present in 40% of the submucosal neurons, staining fine filaments in the soma and the axonal processes. Calbindin D28k was present in 40% of the submucosal neurons staining both the soma and nerves within the plexus. The neurofilament proteins and calbindin D28k were never observed within the same neurons. Neurofilament-M was co-localised with substance P and calcitonin gene-related peptide but not somatostatin or the other neuropeptides investigated. Calbindib D28k was co-localised with vasoactive intestinal polypeptide and neuropeptide Y. Galanin- and somatostatin-immunoreactive neurons did not contain either the neurofilament proteins or calbindin D28k. The results demonstrate the presence of subsets of submucosal neurons that can be distinguished by the presence of neurofilament-M or calbinsin D28k.  相似文献   
1000.
We studied functional and immunohistochemical characteristics of cultured rat microglia. Unstimulated microglia did not proliferate. Microglia stimulated with LCM (L929 conditioned medium: colony stimulating factor-1) had proliferative activity and increased acid phosphatase activity. LPS (lipopolysaccharide) and IFN gamma (interferon-gamma) but did not affect proliferative activity. Immunohistochemically, RCA-1 lectin and GS-1 lectin, which react to beta-D-galactose and alpha-D-galactose respectively, strongly reacted to the cytoplasm and membrane of unstimulated microglia. After stimulation with LCM, microglia elongated processes and decreased response to these lectins. On the other hand, microglia stimulated with LCM showed increased reactivity to monoclonal antibody of vimentin. Microglia stimulated with LPS had round shape and had response to these lectins and vimentin. Microglia stimulated with IFN gamma had adhesive activity and weakly stained with these lectins but not with vimentin. ED-1 (monoclonal antibody of rat monocytes/macrophages) reacted to unstimulated and stimulated microglia. In flow cytometry, unstimulated microglia expressed OX-18 (MHC class I) and W3/25 (CD4) antigen. After stimulation with IFN gamma, microglia were induced to express these antigens. CD4 antigen is a marker of helper/inducer T cells and thought to be a receptor of HIV. The results that microglia had CD4 antigen which was further induced with IFN gamma are important to investigate infection of the CNS with HIV. OX-6 (Ia) antigen was induced with IFN gamma. This indicates that the microglia plays a central role in the CNS immune reaction. These characteristics of cultured rat microglia provide useful informations to investigate the pathogenesis of the CNS disorders.  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