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   1356844篇
  免费   88262篇
  国内免费   1910篇
耳鼻咽喉   19040篇
儿科学   44501篇
妇产科学   38195篇
基础医学   195713篇
口腔科学   36701篇
临床医学   119379篇
内科学   255057篇
皮肤病学   30305篇
神经病学   102321篇
特种医学   53487篇
外国民族医学   242篇
外科学   206608篇
综合类   29054篇
现状与发展   2篇
一般理论   442篇
预防医学   95646篇
眼科学   31048篇
药学   106227篇
  35篇
中国医学   3527篇
肿瘤学   79486篇
  2021年   10554篇
  2019年   10721篇
  2018年   15791篇
  2017年   12069篇
  2016年   13778篇
  2015年   15434篇
  2014年   20748篇
  2013年   30533篇
  2012年   40529篇
  2011年   42330篇
  2010年   25754篇
  2009年   23868篇
  2008年   38988篇
  2007年   41807篇
  2006年   42078篇
  2005年   40120篇
  2004年   38397篇
  2003年   36596篇
  2002年   35148篇
  2001年   70904篇
  2000年   72552篇
  1999年   60267篇
  1998年   15220篇
  1997年   13537篇
  1996年   13390篇
  1995年   12563篇
  1994年   11397篇
  1993年   10846篇
  1992年   44779篇
  1991年   43357篇
  1990年   42684篇
  1989年   41080篇
  1988年   36980篇
  1987年   35967篇
  1986年   33888篇
  1985年   31980篇
  1984年   23288篇
  1983年   19739篇
  1982年   11021篇
  1979年   20918篇
  1978年   14321篇
  1977年   12669篇
  1976年   11117篇
  1975年   12617篇
  1974年   14654篇
  1973年   14309篇
  1972年   13558篇
  1971年   12744篇
  1970年   11806篇
  1969年   11331篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
Much of the connective tissue degradation that takes place in periodontal diseases is mediated by proteolytic enzymes. Previous studies have focused on the action of proteinases released by invading polymorphonuclear neutrophils and macrophages, and bacterial enzymes. In view of recent work establishing that resident connective tissue cells can be induced by cytokines to bring about the destruction of their own matrix, we propose a new hypothesis. In this we envisage that a critical step is the interaction of bacterial antigens with inflammatory cells, resulting in the production of a cytokine, interleukin-1. Our interpretation of in vitro evidence is that the loss of connective tissue attachment and bone matrix resorption in periodontal diseases is mediated by metalloproteinases such as collagenase and stromelysin released by cells of the periodontium. Such proteolytic destruction can be induced by interleukin-1, whose production may not be dependent on a specific microbial flora but may be triggered by a number of organisms. It is now clear that interleukin-1 has multiple actions on both immune and non-immune cells; these include the induction of lymphocyte differentiation and proliferation and the stimulation of bone and cartilage resorption, and prostaglandin and metalloproteinase synthesis by connective tissues. It seems likely that further knowledge about the production and function of this cytokine will have an increasing impact in many diseases that involve resorption, particularly since interleukin-1-like molecules can be produced by cell types other than monocytes/macrophages, including keratinocytes and fibroblasts.  相似文献   
994.
We studied glycoprotein content of human colonic goblet cells, using a library of monoclonal antibodies (MAbs) directed against purified human colonic mucin (HCM). Using indirect immunofluorescence (IIF), we found that 17 of 23 anti-HCM MAbs stained some or all goblet cells of normal human colonic mucosa. We observed a variety of cellular staining patterns, including (a) diffuse (homogeneous) staining of intracellular mucin, (b) speckled (inhomogeneous) staining of mucin droplets, (c) peripheral staining of intracellular droplets, (d) cytoplasmic staining of goblet cells, and (e) apical (luminal) surface staining. Staining patterns were not associated with particular HCM species. In addition to variable patterns of IIF within individual cells, anti-HCM MAbs varied in the proportion of goblet cells stained. Some MAbs stained all goblet cells, while others stained a limited number of goblet cells. Although each goblet cell contained more than one type mucin, HCM species III, and IV and V appeared to exist in mutually exclusive goblet cell populations and it was possible to define at least seven subpopulations of goblet cells in colonic mucosa by their content of various combinations of HCM species. Anti-HCM MAbs stained goblet cells from other sites within the gastrointestinal tract to a varying extent. Anti-HCM MAbs also showed extensive cross-reactivity with rodent, rabbit, and monkey colonic mucosa. However, several anti-HCM MAbs stained only human colonic mucosa. These data show that human colonic mucosa contains discrete subpopulations of goblet cells that produce distinctive combinations of specific mucin glycoprotein species.  相似文献   
995.
996.
997.
The purpose of this study is to show the spectrum of adjacent organ invasion and to make a brief review of hepatic alveolar hydatid disease (AHD), using CT and MR imaging. We retrospectively reviewed CT and MR images of three patients with various adjacent organ invasions surgically and histologically proven to be AHD. Local invasion to right kidney and adrenal, right hemidiaphragm and lung were detected in one patient, right adrenal in another patient and gall bladder, duodenum, gastric wall and pancreas invasion in the other. AHD may rarely extend to the gall bladder, stomach, duodenum, pancreas, right adrenal and kidney, diaphragm, pleura and lung. The extension of the disease outside the liver is usually encountered in patients with large, peripherally located masses in the advanced stage of the disease.  相似文献   
998.
Secondary prevention of coronary events in coronary artery disease (CAD) patients with aspirin is generally accepted because of ease of administration, predictable safety, and proven efficacy. The use of long-term anticoagulant therapy with heparins, vitamin-K antagonists (VKAs), or thrombin inhibitors is, however, more controversial. During the last 40 years, several trials have been conducted in order to evaluate the role of anticoagulant therapy in patients with CAD as a protection against subsequent death and thrombo-embolic complications. The conducted trials are heterogeneous in many ways, concerning comparative medications, patient populations, endpoints and follow-up, which makes a standardized recommendation on the basis of these studies difficult. This review is an overview of the largest and best studies on this topic and discusses the scientific background for a possible use of VKA or an alternative anticoagulant treatment in CAD patients, looking at both the beneficial effects and the risk of bleeding.  相似文献   
999.
1000.
PURPOSE: This study aims to determine the effect of loss of breast cancer metastasis suppressor 1 (BRMS1) protein expression on disease-free survival in breast cancer patients stratified by estrogen receptor (ER), progesterone receptor (PR), or HER2 status, and to determine whether loss of BRMS1 protein expression correlated with genomic copy number changes. EXPERIMENTAL DESIGN: A tissue microarray immunohistochemical analysis was done on tumors of 238 newly diagnosed breast cancer patients who underwent surgery at the Cleveland Clinic between January 1, 1995 and December 31, 1996, and a comparison was made with 5-year clinical follow-up data. Genomic copy number changes were determined by array-based comparative genomic hybridization in 47 breast cancer cases from this population and compared with BRMS1 staining. RESULTS: BRMS1 protein expression was lost in nearly 25% of cases. Patients with tumors that were PR negative (P=0.006) or HER2 positive (P=0.039) and <50 years old at diagnosis (P=0.02) were more likely to be BRMS1 negative. No overall correlation between BRMS1 staining and disease-free survival was observed. A significant correlation, however, was seen between loss of BRMS1 protein expression and reduced disease-free survival when stratified by either loss of ER (P=0.008) or PR (P=0.029) or HER2 overexpression (P=0.026). Overall, there was poor correlation between BRMS1 protein staining and copy number status. CONCLUSIONS: These data suggest a mechanistic relationship between BRMS1 expression, hormone receptor status, and HER2 growth factor. BRMS1 staining could potentially be used in patient stratification in conjunction with other prognostic markers. Further, mechanisms other than genomic deletion account for loss of BRMS1 gene expression in breast tumors.  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