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   2305813篇
  免费   173988篇
  国内免费   7501篇
耳鼻咽喉   31031篇
儿科学   70458篇
妇产科学   62444篇
基础医学   322127篇
口腔科学   66219篇
临床医学   204084篇
内科学   460320篇
皮肤病学   52459篇
神经病学   183676篇
特种医学   92900篇
外国民族医学   383篇
外科学   366114篇
综合类   51574篇
现状与发展   4篇
一般理论   761篇
预防医学   172174篇
眼科学   51216篇
药学   169006篇
  8篇
中国医学   4622篇
肿瘤学   125722篇
  2018年   22924篇
  2016年   20899篇
  2015年   23559篇
  2014年   32545篇
  2013年   48814篇
  2012年   61628篇
  2011年   65590篇
  2010年   40627篇
  2009年   39180篇
  2008年   62144篇
  2007年   66278篇
  2006年   67686篇
  2005年   65360篇
  2004年   62727篇
  2003年   60751篇
  2002年   58404篇
  2001年   117021篇
  2000年   120821篇
  1999年   100933篇
  1998年   27544篇
  1997年   24477篇
  1996年   25275篇
  1995年   24762篇
  1994年   23038篇
  1993年   21477篇
  1992年   80680篇
  1991年   78433篇
  1990年   75910篇
  1989年   73077篇
  1988年   67322篇
  1987年   65835篇
  1986年   62005篇
  1985年   59687篇
  1984年   44251篇
  1983年   37539篇
  1982年   21908篇
  1981年   19378篇
  1980年   18220篇
  1979年   39961篇
  1978年   28180篇
  1977年   24018篇
  1976年   21582篇
  1975年   23149篇
  1974年   27520篇
  1973年   26365篇
  1972年   24685篇
  1971年   23016篇
  1970年   21464篇
  1969年   20031篇
  1968年   18564篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
91.
92.
Clinicopathological and electron microscopical findings of eight cases of enzootic nasal adenocarcinoma of sheep, diagnosed solely in one big flock in Slovenia between years 2001 and 2003 are described. All affected sheep were female, their mean age was 4.5 ± 1.5 years and they either belonged to the Istrian pramenka breed (five sheep) or were crossbreeds (three sheep). Tumours that arose from the ethmoid area of the nasal cavity were unilateral in six cases (75%) and bilateral in two cases (25%). All tumours were classified as adenocarcinomas by histopathological examination and they displayed either a combination of tubular and papillary growth or less often solely tubular proliferation. No metastases were detected in regional lymph nodes, brain or other organs. Electron microscopical studies performed on the reprocessed paraffin‐embedded tissues revealed the presence of the virus‐like particles with an average diameter between 70 and 90 nm.  相似文献   
93.
94.
95.
For many parents stopping life-sustaining medical treatment on their dying infant is psychologically impossible. Dostoevsky's insights into human behavior, particularly the fact that individuals do not want the anxiety and guilt associated with responsibility for making difficult decisions, might change the way physicians approach parents for permission to withdraw life-prolonging medical interventions on dying infants.  相似文献   
96.
97.
This prospective clinic-based study evaluated the pretreatment periodontal status of the orthodontic patients seen at the University College Hospital, Ibadan, Nigeria, and assessed the relationship between dental aesthetic index (DAI) scores and periodontal status according to community periodontal index of treatment needs (CPITN) scores. One hundred forty five patients-70 (48.3%) males and 75 (51.7%) females from 6 to 45 years (mean 15.8 +/- 7.5)-were seen. World Health Organization (WHO) guidelines were followed in the examination and reporting of the periodontal status, and DAI scores were assessed based on WHO guidelines. The chi-square test was used to determine the association between the DAI and the CPITN scores. Most patients were in the 6-15 (55.9%) or 16-25 (35.9%) age groups. Based on the WHO preferred cumulative calculations of treatment need (TN), 35.2% of the patients had TN 0, 64.9% had TN 1, 24.9% had TN 2, and only 0.7% had TN 3. The relationship between DAI scores and periodontal treatment needs was not statistically significant (P >.05). Although many patients were yet to attain the WHO goal of no more than 1 sextant affected by bleeding or calculus at the age of 15, over one third had satisfactory periodontal health.  相似文献   
98.
Four clinical trials of porcine islet transplantation have been reported, and there are verbal reports that clinical trials on much larger scales are continuing in centers in China and Russia. The four reported trials are briefly reviewed and, in the light of the present status of experimental islet xenotransplantation, consideration is given to whether such trials are currently justified. The Ethics Committee of the International Xenotransplantation Association has (1) emphasized the need for encouraging studies in non-human primates before clinical trials should be undertaken, (2) mandatory monitoring for the transfer of porcine microorganisms, and (3) careful regulation and oversight by recognized bodies. Other aspects of the topic, such as the need for informed consent, are briefly discussed. We conclude that, at the present time, more data documenting convincing efficacy, focused on clinically applicable immunosuppressive regimens, are needed to justify the initiation of closely monitored clinical trials. A clinical trial may then be justified even though the potential risk to the patients, and possibly for society, will not be zero.  相似文献   
99.
Summary: The mosaic (Atp7a mo-ms ) is an X-linked, lethal mutation in mice. In mosaic mutant males, many clinical features characteristic of defective copper metabolism have been observed and they die at the age of 15 days, exhibiting strongsimilarities to the brindled and macular mutants. About 4% of the mutant males live to sexual maturity and some of them are fertile. In this paper, alterationsin the structure of the kidney from adult mutants are described. Owing to an inherited defect of efflux, copper is accumulated in the kidney of the mutants up to a toxic level and this leads to severe damage of the renal cortex. Pathological changes in the kidney mostly affected the structure of the renal corpuscle and renaltubules.  相似文献   
100.
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