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   3735442篇
  免费   312298篇
  国内免费   13820篇
耳鼻咽喉   51126篇
儿科学   119502篇
妇产科学   98087篇
基础医学   584053篇
口腔科学   103002篇
临床医学   335416篇
内科学   665765篇
皮肤病学   95617篇
神经病学   319491篇
特种医学   149102篇
外国民族医学   535篇
外科学   574448篇
综合类   114069篇
现状与发展   23篇
一般理论   2453篇
预防医学   313510篇
眼科学   86139篇
药学   261118篇
  22篇
中国医学   10177篇
肿瘤学   177905篇
  2021年   55411篇
  2020年   35303篇
  2019年   58362篇
  2018年   72028篇
  2017年   54913篇
  2016年   60707篇
  2015年   74593篇
  2014年   108976篇
  2013年   174285篇
  2012年   99939篇
  2011年   100632篇
  2010年   118650篇
  2009年   122723篇
  2008年   87934篇
  2007年   91329篇
  2006年   101988篇
  2005年   97011篇
  2004年   99457篇
  2003年   89707篇
  2002年   79485篇
  2001年   120925篇
  2000年   115201篇
  1999年   111766篇
  1998年   67108篇
  1997年   64635篇
  1996年   62638篇
  1995年   58251篇
  1994年   52414篇
  1993年   48935篇
  1992年   82962篇
  1991年   79437篇
  1990年   75971篇
  1989年   74642篇
  1988年   69468篇
  1987年   68154篇
  1986年   64944篇
  1985年   64835篇
  1984年   56605篇
  1983年   51305篇
  1982年   44780篇
  1981年   41946篇
  1980年   39531篇
  1979年   48973篇
  1978年   40966篇
  1977年   36783篇
  1976年   34092篇
  1975年   32846篇
  1974年   35545篇
  1973年   34200篇
  1972年   31695篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
In the present study, we examined the effect of CsA on the in vitro production of Ig and on the in vitro production of molecules known to have B-cell growth and differentiation activities, such as IL-6 and sCD23. For the purpose of this study, we developed an experimental In vitro system closely resembling an In vivo model of ongoing B-cell activation. Pre-activated B cells proliferated and produced IgM optimally when they were re-cultured in the presence of IL-2/IL-6. CsA down-regulated the IL-2/IL-6-induced proliferative responses of pre activated B cells by at least 50%., but it up-regulated IgM production in the same experiments. This up regulating effect was not cytokine-related since it was also seen when cells were re-cultured in the absence of any cytokines. Optimal release of sCD23 was observed when SAC-pre-activated B cells were re cultured in the presence of IL-4 or IL-4 plus IL-2 and CsA up-regulated significantly the release of this molecule in these cultures. Finally, CsA was shown to inhibit PHA-induced cell proliferation of PBMC and to up-rcgulate IL-6 production in the same cultures. We conclude that CsA can amplify in vitro both the production of Ig and the release of sCD23 by pre activated B cells. This finding, in combination with the CsA-induced up-regulation of lectin-induced IL-6 production, may have clinical implications in disease states with an ongoing immune activation, where prolonged administration of CsA might be anticipated.  相似文献   
992.
993.
Summary Squamous cell carcinoma of the head and neck is a disease predominantly of males and is due to a variety of known environmental irritants, notably cigarette smoke. Dietary, viral and immunological factors may also be relevant. Head and neck squamous cancers express epidermal growth factor receptors and some show weak levels of oestrogen receptor activity, but a reliable serum marker of tumour burden remains to be identified. The prognosis is found to be less favourable in females, in those with advanced T stage, in association with multiple node involvement, especially where extracapsular spread is present and where the T4/T8 ratio is elevated. Administration of heterologous blood during therapy may also have an adverse effect on prognosis. Interested clinicians must remember that most cases are preventable. Correspondence to: A.G.D. Maran  相似文献   
994.
Data on 232 members of a single pedigree, descended from two pairs of original parents, were made available to the participants of Genetic Analysis Workshop 8 (GAW8). In addition to information concerning age and sex, measurements for 10 quantitative traits and genotypes at 22 polymorphic marker loci were also provided for a subset of 193 of these family members. © 1993 Wiley-Liss, Inc.  相似文献   
995.
Abstract: This study reports on an analysis of the lead concentrations in 123 venous blood samples collected from Perth children aged between two months and 17 years attending Princess Margaret Hospital. The overall geometric mean was 6.9 μg lead per 100 ml whole blood, with 95 per cent of results lying between 3.2 and 14.8 μg/100 ml. Among children under five years of age, those aged between 18 months and two years had the highest geometric mean blood lead (11.1 μg/100 ml). There were no consistent associations between geometric mean blood lead and area of residence, age group or sex. In this sample of Perth children, the mean blood lead concentration was lower than those reported in other studies. Less than 0.1 per cent of children of the age range studied would have been expected to have lead levels exceeding the NHMRC ‘level of concern’ (25 μg/100 ml) current at the time of the study. However, the recent adoption of goal of less than 10 μg/100 ml could mean that lead levels in up to 21 per cent of Perth children would now be regarded as excessive.  相似文献   
996.
997.
We have presented a rare case of primary involvement of the anterior mediastinum by osteogenic sarcoma in which CT was useful in demonstrating calcium within the mass, and in distinguishing the mass from surrounding bony structures. Although rare, extraosseous osteogenic sarcoma should be included in the differential diagnosis of a calcified anterior mediastinal mass.  相似文献   
998.
999.
The present authors investigated the excretion, distribution and pharmacokinetics of the novel potential antirheumatic agent flobufen and its active metabolite after p.o. and i.v. doses of 2, 10 and 50 mg/kg administered to rats. The drug is resorbed well from the digestive tract and mostly it is metabolized to the principal metabolite M, which is only slowly excreted from the organism mainly by renal clearance. Within the whole dose range the kinetics of the drug is linear. Binding of flobufen and M to proteins is high (95-99%). The highest concentrations of radioactive metabolites (mostly M) were found in the plasma, liver, lungs, kidneys, connective tissue and inflammatory foci. The penetration of metabolites through the placenta and excretion in human milk are relatively important.  相似文献   
1000.
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