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   1048282篇
  免费   70199篇
  国内免费   4190篇
耳鼻咽喉   14213篇
儿科学   30629篇
妇产科学   26567篇
基础医学   159124篇
口腔科学   30674篇
临床医学   91480篇
内科学   203181篇
皮肤病学   24261篇
神经病学   74286篇
特种医学   38483篇
外国民族医学   157篇
外科学   158247篇
综合类   24016篇
现状与发展   4篇
一般理论   224篇
预防医学   67495篇
眼科学   25147篇
药学   82317篇
  4篇
中国医学   4597篇
肿瘤学   67565篇
  2021年   8500篇
  2019年   8327篇
  2018年   12314篇
  2017年   9463篇
  2016年   10526篇
  2015年   12011篇
  2014年   16330篇
  2013年   23051篇
  2012年   31100篇
  2011年   32247篇
  2010年   19097篇
  2009年   17943篇
  2008年   29316篇
  2007年   31549篇
  2006年   31563篇
  2005年   29281篇
  2004年   28226篇
  2003年   26817篇
  2002年   25958篇
  2001年   59470篇
  2000年   60548篇
  1999年   49903篇
  1998年   12424篇
  1997年   10364篇
  1996年   10229篇
  1995年   9617篇
  1994年   8757篇
  1993年   8051篇
  1992年   36432篇
  1991年   35438篇
  1990年   34278篇
  1989年   33857篇
  1988年   30639篇
  1987年   29658篇
  1986年   27928篇
  1985年   26050篇
  1984年   18618篇
  1983年   15615篇
  1982年   8308篇
  1979年   16338篇
  1978年   11130篇
  1977年   9497篇
  1976年   8601篇
  1975年   9655篇
  1974年   11299篇
  1973年   10773篇
  1972年   10233篇
  1971年   9674篇
  1970年   9220篇
  1969年   8639篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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   
102.
103.
104.
Digestive Diseases and Sciences - To determine whether the presence of portal vein thrombosis (PVT) where venous flow within the liver may be altered may delay the diagnosis of HCC and be...  相似文献   
105.
106.
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   
107.
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   
108.
109.
ABSTRACT

Purpose

To investigate the effect of 1% tropicamide on anterior chamber aqueous flare (ACAF) measurements acquired with laser flare meter in patients with pseudoexfoliation.  相似文献   
110.
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   
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