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   1474340篇
  免费   118030篇
  国内免费   3489篇
耳鼻咽喉   18837篇
儿科学   48401篇
妇产科学   42120篇
基础医学   209486篇
口腔科学   39194篇
临床医学   133043篇
内科学   297423篇
皮肤病学   34241篇
神经病学   122973篇
特种医学   55847篇
外国民族医学   465篇
外科学   219114篇
综合类   33601篇
现状与发展   3篇
一般理论   558篇
预防医学   116035篇
眼科学   32786篇
药学   103036篇
  2篇
中国医学   3421篇
肿瘤学   85273篇
  2021年   12005篇
  2019年   12819篇
  2018年   18008篇
  2017年   13739篇
  2016年   15446篇
  2015年   17339篇
  2014年   24567篇
  2013年   36221篇
  2012年   49824篇
  2011年   52478篇
  2010年   30776篇
  2009年   29339篇
  2008年   48493篇
  2007年   51453篇
  2006年   51904篇
  2005年   50170篇
  2004年   47843篇
  2003年   45439篇
  2002年   43846篇
  2001年   73604篇
  2000年   75012篇
  1999年   62227篇
  1998年   17804篇
  1997年   16110篇
  1996年   16176篇
  1995年   15341篇
  1994年   13844篇
  1993年   13006篇
  1992年   46242篇
  1991年   43841篇
  1990年   41785篇
  1989年   39840篇
  1988年   36496篇
  1987年   35610篇
  1986年   33138篇
  1985年   31582篇
  1984年   24172篇
  1983年   20360篇
  1982年   12586篇
  1981年   11143篇
  1979年   20904篇
  1978年   14804篇
  1977年   12285篇
  1976年   11507篇
  1975年   11728篇
  1974年   14126篇
  1973年   13658篇
  1972年   12732篇
  1971年   11569篇
  1970年   10984篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
101.
102.
Background : The clinical course of chronic hepatitis B is variable. Patients with hepatic decompensation, bridging necrosis or an alpha-fetoprotein level greater than 100 ng/mL during an exacerbation of hepatitis have a high risk of developing cirrhosis. This study was conducted to evaluate the effect of colchicine in the prevention of cirrhosis in such patients.
Methods : Patients with risk factor(s) were randomized to receive either colchicine 5 mg/week or no specific treatment, the end point being development of cirrhosis.
Results : After a follow up period of 4 years, the treatment group had a marked reduction in exacerbations of acute hepatitis (32% vs. 63%/patient/year, P <0.005). Seven out of 38 patients in the treatment group and 10 out of 27 patients in the control group developed cirrhosis. The calculated cumulative incidence of cirrhosis by the end of first, second, third and fourth years in the treatment group was 8.7, 18.6, 32 and 32%, respectively. The corresponding figures in the control group were 30, 35.5, 46.3 and 73.2%, respectively, with a P -value of 0.057.
Conclusions : The results suggest that colchicine may prevent cirrhosis in chronic hepatitis B patients with risk factor(s), possibly by suppressing exacerbations of hepatitis through an anti-inflammatory effect.  相似文献   
103.
104.
105.
106.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.  相似文献   
107.
108.
One of our patients had trouble maintaining therapeutic and safe levels of theophylline, even though we were careful in planning and monitoring her drug regimen. This case report shows how we were able to use principles of pharmacokinetics to distinguish among plausible explanations for her experience. We discovered that she was not taking the drug consistently as prescribed and that supervised administration resolved apparent contradictions between doses and serum levels. We believe that physicians can use the same information and methods that we used to get better and safer results from theophylline therapy.  相似文献   
109.
A rotating contact lens holder for the three-mirror Goldmann lens permits circular examination of the fundus or chamber angle without having to change the position of the fingers on the edge of the lens. The contact lens holder consists of an outer polygonal ring hold by the thumber and index finger. An inner rotating ring holds the contact lens. Continuous rotation of the contact lens is performed with the free middle Finger. This device permits circular examination of the retina without interruption of fixation. The instrument improves not only the speed but also the reliability of the examination.  相似文献   
110.
Six patients who injured their wrists had radiographs documenting a dorsal, 5- to 10-mm oblong fragment of bone immediately proximal to the base of the fourth and/or fifth metacarpal bones. The fragment was seen on the pronation oblique and/or lateral projections, but not on the posteroanterior projection. The radiographic appearance of the fragment was remarkably similar in all cases. In the one patient in which it was performed, pluridirectional tomography demonstrated that the fragment originated from the dorsal surface of the hamate. Five of the six patients also had associated posterior dislocation of the fourth and/or fifth metacarpals. We conclude that this fragment represents a coronal fracture through the body of the hamate resulting from posterior dislocation or subluxation of the fourth and/or fifth metacarpal.  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