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   1338981篇
  免费   112583篇
  国内免费   6371篇
耳鼻咽喉   16710篇
儿科学   43011篇
妇产科学   36559篇
基础医学   183672篇
口腔科学   36280篇
临床医学   120828篇
内科学   278546篇
皮肤病学   31887篇
神经病学   110543篇
特种医学   55543篇
外国民族医学   274篇
外科学   210368篇
综合类   31540篇
现状与发展   2篇
一般理论   416篇
预防医学   106779篇
眼科学   28089篇
药学   93796篇
  5篇
中国医学   2228篇
肿瘤学   70859篇
  2018年   13379篇
  2017年   10638篇
  2016年   12799篇
  2015年   14304篇
  2014年   19955篇
  2013年   29750篇
  2012年   36264篇
  2011年   38914篇
  2010年   24392篇
  2009年   23927篇
  2008年   36398篇
  2007年   38823篇
  2006年   39929篇
  2005年   38537篇
  2004年   36756篇
  2003年   35837篇
  2002年   33854篇
  2001年   66061篇
  2000年   67932篇
  1999年   56597篇
  1998年   16729篇
  1997年   15021篇
  1996年   16017篇
  1995年   16236篇
  1994年   15101篇
  1993年   14156篇
  1992年   47106篇
  1991年   45751篇
  1990年   43978篇
  1989年   41823篇
  1988年   38767篇
  1987年   38088篇
  1986年   35867篇
  1985年   34642篇
  1984年   26363篇
  1983年   22110篇
  1982年   13849篇
  1981年   12453篇
  1980年   11721篇
  1979年   23549篇
  1978年   17077篇
  1977年   14386篇
  1976年   13184篇
  1975年   13725篇
  1974年   16096篇
  1973年   15404篇
  1972年   14176篇
  1971年   13040篇
  1970年   11887篇
  1969年   11107篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Fetal B lymphocytes in mice and humans use a limited number of the available VH gene segments. Mouse fetal B cells primarily utilize 3' VH elements, suggesting that the localization of these elements determines their rearrangement frequency. The previously reported non-random usage of human VH genes has been more difficult to explain. In this study the authors analysed the expression of the most proximal 3' human VH element (VH6) using a monoclonal antibody (JE-6). VH6 expression was assessed in various B cell differentiation stages from fetal liver, bone marrow and spleen at 12–20 weeks of gestation. The authors demonstrate that the level of VH6 expression does not exceed a stochastic usage frequency. This suggests that the localization of VH6 does not significantly promote its expression during human fetal life, and that other factors must affect the usage of VH genes during human fetal development.  相似文献   
112.
113.
A case-control study of squamous cell carcinoma of the upper aerodigestive tract conducted in Heidelberg and Giessen (FRG) provided information on occupational factors in 200 patients and 800 controls (adjusted to sex, age and area of living; 4:1 matched design). The number of subjects exposed to wood dusts, organic chemicals, coal products or to cement was significantly elevated in the tumour group. An increased risk for head and neck cancer was observed after exposition to wood dust (RR = 2,2), organic compounds (RR = 2,4), coal products (RR = 2,7) and especially to cement (RR = 4,4). The cancer risk due to cement exposition showed a positive correlation to the duration of exposition and remained significantly elevated after adjustment for alcohol and tobacco consumption.  相似文献   
114.
Facial reanimation after acoustic neuroma excision is currently accomplished using a variety of surgical techniques. A multi-institutional survey of patient perceptions of facial reanimation success was accomplished by mailing a questionnaire to 809 randomly selected members of the Acoustic Neuroma Association. Four hundred sixty patients who underwent 296 reanimation procedures responded. Facial to hypoglossal nerve anastomosis, tarsorrhaphy, and upper eyelid implants were most frequently performed. The patient's estimations of initial deficit, spontaneous recovery, and overall satisfaction with the reanimation procedures are discussed.  相似文献   
115.
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   
116.
117.
118.
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   
119.
The medical world would seem to be one of increasing technology and shrinking financial resources. New tests and therapies constantly appear on the market. Most have been examined for efficacy and side effects. The real question is: where does the new test or therapy fit in with all previous products? Decision analysis is a mathematical tool adapted to assess the relative cost-effectiveness of complex diagnostic and therapeutic strategies.  相似文献   
120.
Herpes zoster probably occurs more often than generally thought. Since it produces a radicular distribution of pain, it should be included in the differential diagnosis of radiculopathy. A case is presented in which evaluating the radicular low back pain before the characteristic rash appears was misleading. Careful history-taking concerning the exact nature of the pain and sensory changes is needed to differentiate between zoster and radiculopathy, if no rash is evident.  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