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   714579篇
  免费   50830篇
  国内免费   1311篇
耳鼻咽喉   9293篇
儿科学   23620篇
妇产科学   17856篇
基础医学   111735篇
口腔科学   20146篇
临床医学   64986篇
内科学   135867篇
皮肤病学   16402篇
神经病学   50689篇
特种医学   25951篇
外国民族医学   76篇
外科学   105537篇
综合类   14890篇
现状与发展   2篇
一般理论   176篇
预防医学   52866篇
眼科学   16414篇
药学   54512篇
  4篇
中国医学   2358篇
肿瘤学   43340篇
  2021年   6027篇
  2019年   5993篇
  2018年   8468篇
  2017年   6484篇
  2016年   7232篇
  2015年   7933篇
  2014年   10776篇
  2013年   16059篇
  2012年   21394篇
  2011年   22344篇
  2010年   13190篇
  2009年   12276篇
  2008年   20507篇
  2007年   21971篇
  2006年   22344篇
  2005年   20834篇
  2004年   20299篇
  2003年   19220篇
  2002年   18712篇
  2001年   36388篇
  2000年   36937篇
  1999年   30455篇
  1998年   7930篇
  1997年   6702篇
  1996年   7010篇
  1995年   6661篇
  1994年   6118篇
  1992年   23004篇
  1991年   22964篇
  1990年   22353篇
  1989年   22110篇
  1988年   20063篇
  1987年   19444篇
  1986年   18497篇
  1985年   17337篇
  1984年   12717篇
  1983年   10768篇
  1982年   5941篇
  1979年   11540篇
  1978年   8139篇
  1977年   6841篇
  1976年   6610篇
  1975年   7282篇
  1974年   8513篇
  1973年   8147篇
  1972年   7667篇
  1971年   7139篇
  1970年   6880篇
  1969年   6309篇
  1968年   5784篇
排序方式: 共有10000条查询结果,搜索用时 199 毫秒
131.
132.
133.
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   
134.
135.
136.
Pharmaceutical Chemistry Journal - N-Substituted 4-aryl-2-hydroxy-4-oxobut-2-enoic acid hydrazides and their complexes with Ni(II), Mn(II), Co(II), Cu(II), and Zn(II) were prepared. Their...  相似文献   
137.
Congenital heart disease is a rare but important finding in adults who experience sudden death. Examination of the congenitally malformed heart has historically been considered esoteric and best left to those with expertise. The Cardiac Risk in the Young cardiovascular pathology laboratory based at St George's University of London has now received over 6,000 cases. Of these, 21 congenitally malformed hearts were retained for research and educational purposes. Hearts were assessed using sequential segmental analysis, and causes of death were adjudicated based on thorough macroscopic examination and histology. Congenital malformations that were encountered included atrial septal defects, ventricular septal defects, tetralogy of Fallot, and transposition of the great arteries in both its regular and congenitally corrected variants. Findings also included hearts with mirror-imaged and isomeric atrial appendages. Direct causes of death included myocardial fibrosis, pulmonary hypertension, and hemorrhage. A small but notable proportion did not reveal a substrate for arrhythmia, raising the question of whether the terminal event was due to the congenital heart disease itself, or an underlying channelopathy. Here, we demonstrate the value of simple sequential segmental analysis in describing and categorizing the cases, with the concept of the “morphological method” serving to identify the distinguishing features of the cardiac components. Clin. Anat. 33:394–404, 2020. © 2019 Wiley Periodicals, Inc.  相似文献   
138.
ObjectivesCocaine is the second most frequently used illicit drug worldwide (after cannabis), and cocaine use disorder (CUD)-related deaths increased globally by 80% from 1990 to 2013. There is yet to be a regulatory-approved treatment. Emerging preclinical evidence indicates that deep brain stimulation (DBS) of the nucleus accumbens may be a therapeutic option. Prior to expanding the costly investigation of DBS for treatment of CUD, it is important to ensure societal cost-effectiveness.AimsWe conducted a threshold and cost-effectiveness analysis to determine the success rate at which DBS would be equivalent to contingency management (CM), recently identified as the most efficacious therapy for treatments of CUDs.Materials and MethodsQuality of life, efficacy, and safety parameters for CM were obtained from previous literature. Costs were calculated from a societal perspective. Our model predicted the utility benefit based on quality-adjusted life-years (QALYs) and incremental-cost-effectiveness ratio resulting from two treatments on a one-, two-, and five-year timeline.ResultsOn a one-year timeline, DBS would need to impart a success rate (ie, cocaine free) of 70% for it to yield the same utility benefit (0.492 QALYs per year) as CM. At no success rate would DBS be more cost-effective (incremental-cost-effectiveness ratio <$50,000) than CM during the first year. Nevertheless, as DBS costs are front loaded, DBS would need to achieve success rates of 74% and 51% for its cost-effectiveness to exceed that of CM over a two- and five-year period, respectively.ConclusionsWe find DBS would not be cost-effective in the short term (one year) but may be cost-effective in longer timelines. Since DBS holds promise to potentially be a cost-effective treatment for CUDs, future randomized controlled trials should be performed to assess its efficacy.  相似文献   
139.
140.
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