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   93163篇
  免费   5764篇
  国内免费   723篇
耳鼻咽喉   1080篇
儿科学   2825篇
妇产科学   2282篇
基础医学   12548篇
口腔科学   2116篇
临床医学   7498篇
内科学   20325篇
皮肤病学   1945篇
神经病学   8620篇
特种医学   3635篇
外国民族医学   23篇
外科学   13074篇
综合类   1641篇
一般理论   47篇
预防医学   5367篇
眼科学   1471篇
药学   7598篇
  3篇
中国医学   510篇
肿瘤学   7042篇
  2023年   381篇
  2022年   932篇
  2021年   1684篇
  2020年   1101篇
  2019年   1558篇
  2018年   1940篇
  2017年   1491篇
  2016年   1547篇
  2015年   1813篇
  2014年   2391篇
  2013年   3536篇
  2012年   4695篇
  2011年   4878篇
  2010年   3194篇
  2009年   2788篇
  2008年   4331篇
  2007年   4527篇
  2006年   4326篇
  2005年   4117篇
  2004年   4459篇
  2003年   4317篇
  2002年   4374篇
  2001年   3705篇
  2000年   3664篇
  1999年   2960篇
  1998年   1115篇
  1997年   874篇
  1996年   801篇
  1995年   776篇
  1994年   683篇
  1993年   664篇
  1992年   1773篇
  1991年   1748篇
  1990年   1486篇
  1989年   1437篇
  1988年   1315篇
  1987年   1174篇
  1986年   1162篇
  1985年   1029篇
  1984年   760篇
  1983年   690篇
  1982年   444篇
  1981年   380篇
  1979年   564篇
  1978年   414篇
  1975年   427篇
  1974年   479篇
  1973年   462篇
  1972年   423篇
  1971年   392篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Five 3'-fluorinated ribonucleosides were prepared and evaluated for their inhibitory properties against different viruses. The synthesis of these compounds was achieved by treatment of 2',5'-di-O-tritylated nucleoside analogues possessing a xylo-configuration with diethylaminosulfur trifluoride, followed by deprotection. 3'-Fluoro-3'-deoxyadenosine was active against a broad range of viruses, encompassing both DNA viruses [pox (vaccinia)], single-stranded (+) RNA viruses [picorna (polio, Coxsackie B), toga (sindbis, Semliki Forest)] and double-stranded RNA viruses (reo). In its antiviral activity spectrum 3'-fluoro-3'-deoxyadenosine clearly differed from those adenosine analogues that are known as inhibitors of S-adenosylhomocysteine hydrolase. 3'-Fluoro-3'-deoxyadenosine also proved effective in vivo, in inhibiting tail lesion formation in mice inoculated intravenously with vaccinia virus.  相似文献   
42.
Clinical and biological data were evaluated using Desu univariate analyses or Cox multivariate analyses in a series of 1,777 chronic lymphocytic leukemia (CLL) patients from an Italian Cooperative Group. In univariate analyses, age and sex of patients, presence of bone marrow (BM; greater than or equal to 50%), and peripheral blood (PB; greater than or equal to 60,000/microL) lymphocytosis, anemia (hemoglobin [Hb] less than 11 g/dL), thrombocytopenia (less than 100,000/microL), direct Coombs' test positivity, hepatomegaly, splenomegaly, and extent of lymph node involvement were shown to be of significant prognostic value. Multivariate analyses, through a stepwise procedure, showed that the most important prognostic variables are Hb, hepatomegaly, lymph node involvement, PB lymphocytosis, and age and sex of patients. Further covariates would produce an improvement having a nonsignificant P value. Based on the results of multivariate analyses, a four-step staging using the significant variables of the Cox model is proposed.  相似文献   
43.
Follicular fluids from eight patients with one ovary and from ten patients with two ovaries were investigated for bioactive inhibin, total renin, oestradiol (E2) and progesterone (P4) concentrations. Four follicular fluids were pooled per patient before assessment. All women had been stimulated similarly using a protocol including a GnRH agonist, HMG and HCG. Renin levels were significantly lower and P4 significantly higher in pools of follicular fluid from patients with one ovary, whereas inhibin and E2 concentrations were similar in both patient groups. A significant negative correlation was found in the pools of follicular fluid between inhibin and E2 in both groups. These results suggest a role for inhibin and renin in the paracrine and autocrine control of stimulated follicular development.  相似文献   
44.
45.
46.
47.
Following the outbreak of poliomyelitis in Gazankulu in 1982, the immunisation services in Gazankulu were thoroughly examined. As a result of this, a comprehensive immunisation policy for Gazankulu was accepted in November 1986. The broad aim of the policy is to provide effective immunisation to all Gazankulu residents against tuberculosis, diphtheria, pertussis, tetanus, poliomyelitis and measles. A specific objective is that by the end of 1987, 85% of under-5s should have been vaccinated against these six diseases and by the end of 1990 this percentage should be 97%. The detailed strategies to reach these objectives are highlighted. Within the framework of the objectives, the policy allows different areas to formulate individual strategies. Programme monitoring and community involvement are two crucial aspects of the policy and these are discussed in detail. The early successes and difficulities in implementing this policy are discussed.  相似文献   
48.
Information regarding breast feeding practices of 600 children below 3 years of age attending hospital OPDs and private clinics during 1984-85 were collected. 51.3% received breast milk within 24 hrs. of birth, mean duration of breast feeding being 6 months. 68% of Infants had been given prelacteal feeds. 34% children were exclusively breast fed till 1 month. Insufficient milk was an important reason for discontinuation before 6 months.  相似文献   
49.
50.
The main objective of this study was to examine the psychosocial stress model developed by Taylor and Aspinwall with emotional exhaustion as the outcome variable. Respondents, 409 men and 346 women, who had a paid job for at least 20 hours per week, completed questionnaires concerning demographic variables, personality, temperament, work pressure, workload, perceived social support, appraisal, coping, and emotional exhaustion. Structural equation analyses provided only partial support for the validity of the model. First, on theoretical and statistical grounds, one more path linking external resources to social support was added. Second, contrary to expectations, coping styles did not predict emotional exhaustion. To conclude, when coping is measured retrospectively, it does not add to our understanding of emotional exhaustion. It is suggested that future studies should be longitudinal and include objective measures of stressors and psychosocial health outcomes in addition to self‐reports. Copyright © 2007 John Wiley & Sons, Ltd.  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