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   277898篇
  免费   13658篇
  国内免费   643篇
耳鼻咽喉   3434篇
儿科学   8545篇
妇产科学   5935篇
基础医学   39306篇
口腔科学   6223篇
临床医学   22834篇
内科学   61110篇
皮肤病学   7054篇
神经病学   25476篇
特种医学   8482篇
外国民族医学   101篇
外科学   34782篇
综合类   1147篇
一般理论   81篇
预防医学   24895篇
眼科学   5303篇
药学   19197篇
  1篇
中国医学   775篇
肿瘤学   17518篇
  2023年   1718篇
  2022年   1817篇
  2021年   5181篇
  2020年   3056篇
  2019年   5293篇
  2018年   9023篇
  2017年   6003篇
  2016年   6141篇
  2015年   6911篇
  2014年   7696篇
  2013年   11709篇
  2012年   19728篇
  2011年   19673篇
  2010年   9825篇
  2009年   7680篇
  2008年   16705篇
  2007年   17554篇
  2006年   16127篇
  2005年   15948篇
  2004年   14725篇
  2003年   13395篇
  2002年   12589篇
  2001年   6383篇
  2000年   6407篇
  1999年   5781篇
  1998年   1186篇
  1997年   955篇
  1996年   905篇
  1995年   817篇
  1992年   3318篇
  1991年   2967篇
  1990年   2833篇
  1989年   2566篇
  1988年   2433篇
  1987年   2267篇
  1986年   2165篇
  1985年   1954篇
  1984年   1464篇
  1983年   1227篇
  1979年   1244篇
  1978年   887篇
  1977年   834篇
  1975年   821篇
  1974年   1037篇
  1973年   1034篇
  1972年   973篇
  1971年   956篇
  1970年   891篇
  1969年   934篇
  1968年   811篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
In the first experiment, 52 sows, each having raised one litter, were randomly assigned to the five following groups: control (nongravid) for pregnancy (CP), 110 d pregnancy (P110), control (nongravid) for lactation (CL), 4-wk lactation with 8 (L8) and with 12 (L12) piglets. In a second experiment, 36 sows, each having raised three litters, were randomly assigned to the following groups: control group (nongravid) fed a low-energy-density, 1% tallow diet (CLED) and two lactating groups, one fed the low-energy-density diet (LLED) and one fed a high-energy-density, 10% tallow diet (LHED). At slaughter, the stomach, small and large intestine and cecum were excised, emptied and freed from fat. Lengths and pre- and post-defatting weights were measured. Portions of tissues were homogenized and analyzed for protein, pepsin, maltase, RNA and DNA. Pregnancy had no effect on the weights of the different components of the gastrointestinal tract. Liver and small intestine weights were larger in lactating sows than in the CL group. Sows nursing 12 piglets had heavier livers than those nursing 8. The fundic mucosa of the latter had higher total pepsin activity and total protein and RNA contents than that of L12 sows. LHED sows had heavier small intestine and lower total pepsin content of the fundic mucosa than LLED sows.  相似文献   
42.
Gallibacterium anatis (previously named Pasteurella haemolytica-like) is considered a normal inhabitant of genital and upper respiratory tracts of healthy chickens, but it is also associated with different pathological conditions. Secreted metalloproteases from field and reference G. anatis cultures were obtained by methanol precipitation and were characterized. Proteins of molecular mass higher than 100 kDa showing proteolytic activity were observed in 10% polyacrylamide gels copolymerized with 1% bovine casein. They were active at alkaline pH, and inhibited by ethylenediamine tetraacetic acid. Their activity was stable at 50 degrees C, but partially inhibited at 60 degrees C, and totally inhibited at higher temperatures. Secreted proteins were able to degrade chicken IgG after 24 h of incubation, and cross-reacted with a polyclonal antibody against purified protease from Actinobacillus pleuropneumoniae. Secreted metalloproteases could play a role in infections caused by G. anatis.  相似文献   
43.
44.

Introduction  

This paper presents the results of a study on the psychometric properties of an authorized Spanish version of the McMaster Family Assessment Device, a self-report measure of family functioning.  相似文献   
45.
46.

Background  

Advances in intensive care medicine have increased survival rates of patients with critical neurological conditions. The focus of prognostication for such patients is therefore shifting from predicting chances of survival to meaningful neurological recovery. This study assessed the variability in long-term outcome predictions among physicians and aimed to identify factors that may account for this variability.  相似文献   
47.
Background Chromium allergy has traditionally been caused by occupational skin contact with cement. In 1983, Danish legislation made the addition of ferrous sulphate compulsory in cement to reduce the water‐soluble chromium content to not more than 2 ppm. An effect from this intervention has previously been demonstrated among Danish construction workers. Objectives To investigate the development of chromium allergy among patients with dermatitis tested between 1985 and 2007 in Denmark. Furthermore, to determine causative exposures in patients with chromium allergy. Patients and methods A retrospective analysis of patch test data was performed (n = 16 228) and charts from patients with chromium allergy were reviewed. Comparisons were made using a χ2 test. Logistic regression analyses were used to test for associations. Results The prevalence of chromium allergy decreased significantly from 3·6% in 1985 to 1% in 1995 (Ptrend < 0·001) but increased to 3·3% in 2007 (Ptrend < 0·001). The frequency of clinically relevant cement exposure decreased significantly among patients with chromium allergy from 12·7% in 1989–1994 to 3·0% (P < 0·01) in 1995–2007, whereas the frequency of relevant leather exposure increased significantly from 24·1% during 1989–1994 to 45·5% during 1995–2007 (P < 0·02). Conclusions Chromium allergy is currently increasing in Denmark due to leather exposure.  相似文献   
48.
49.
50.
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