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   1807694篇
  免费   141059篇
  国内免费   28914篇
耳鼻咽喉   20619篇
儿科学   52435篇
妇产科学   44100篇
基础医学   236156篇
口腔科学   42957篇
临床医学   175833篇
内科学   352861篇
皮肤病学   35371篇
神经病学   142594篇
特种医学   75419篇
外国民族医学   487篇
外科学   267940篇
综合类   82559篇
现状与发展   78篇
一般理论   432篇
预防医学   142116篇
眼科学   40023篇
药学   133782篇
  339篇
中国医学   20096篇
肿瘤学   111470篇
  2022年   16364篇
  2021年   24711篇
  2020年   17158篇
  2019年   19684篇
  2018年   43953篇
  2017年   35795篇
  2016年   39335篇
  2015年   29049篇
  2014年   37950篇
  2013年   45180篇
  2012年   64409篇
  2011年   82876篇
  2010年   56811篇
  2009年   46202篇
  2008年   70625篇
  2007年   75164篇
  2006年   56756篇
  2005年   56611篇
  2004年   49974篇
  2003年   49108篇
  2002年   44220篇
  2001年   72827篇
  2000年   75675篇
  1999年   64982篇
  1998年   22143篇
  1997年   20542篇
  1996年   20282篇
  1995年   20140篇
  1994年   18304篇
  1993年   16232篇
  1992年   49631篇
  1991年   47931篇
  1990年   45962篇
  1989年   43518篇
  1988年   40196篇
  1987年   39299篇
  1986年   36829篇
  1985年   35434篇
  1984年   26810篇
  1983年   22428篇
  1982年   14079篇
  1979年   23740篇
  1978年   17140篇
  1977年   14453篇
  1976年   13239篇
  1975年   13779篇
  1974年   16196篇
  1973年   15473篇
  1972年   14244篇
  1971年   13080篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
131.
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   
132.
133.
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   
134.
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   
135.
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   
136.
137.
138.
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   
139.
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   
140.
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