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   15067篇
  免费   1030篇
  国内免费   22篇
耳鼻咽喉   92篇
儿科学   502篇
妇产科学   390篇
基础医学   1868篇
口腔科学   100篇
临床医学   2210篇
内科学   2821篇
皮肤病学   217篇
神经病学   1356篇
特种医学   391篇
外国民族医学   1篇
外科学   1372篇
综合类   204篇
一般理论   16篇
预防医学   2049篇
眼科学   180篇
药学   1011篇
中国医学   16篇
肿瘤学   1323篇
  2024年   15篇
  2023年   100篇
  2022年   167篇
  2021年   344篇
  2020年   228篇
  2019年   390篇
  2018年   421篇
  2017年   319篇
  2016年   339篇
  2015年   403篇
  2014年   522篇
  2013年   792篇
  2012年   1195篇
  2011年   1174篇
  2010年   635篇
  2009年   606篇
  2008年   945篇
  2007年   1104篇
  2006年   1030篇
  2005年   1026篇
  2004年   903篇
  2003年   880篇
  2002年   751篇
  2001年   103篇
  2000年   63篇
  1999年   119篇
  1998年   171篇
  1997年   126篇
  1996年   116篇
  1995年   122篇
  1994年   108篇
  1993年   100篇
  1992年   59篇
  1991年   43篇
  1990年   43篇
  1989年   46篇
  1988年   50篇
  1987年   42篇
  1986年   36篇
  1985年   36篇
  1984年   47篇
  1983年   38篇
  1982年   50篇
  1981年   49篇
  1980年   39篇
  1979年   27篇
  1978年   25篇
  1977年   18篇
  1976年   24篇
  1975年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.

Background  

The efficacy of academic detailing in changing physicians' knowledge and practice has been the subject of many primary research publications and systematic reviews. However, there is little written about the features of academic detailing that physicians find valuable or that affect their use of it. The goal of our project was to explore family physicians' (FPs) perceptions of academic detailing and the factors that affect their use of it.  相似文献   
63.
Mice rendered deficient for interleukin (IL) 6 by gene targeting were evaluated for their response to T cell–dependent antigens. Antigen-specific immunoglobulin (Ig)M levels were unaffected whereas all IgG isotypes showed varying degrees of alteration. Germinal center reactions occurred but remained physically smaller in comparison to those in the wild-type mice. This concurred with the observations that molecules involved in initial signaling events leading to germinal center formation were not altered (e.g., B7.2, CD40 and tumor necrosis factor R1). T cell priming was not impaired nor was a gross imbalance of T helper cell (Th) 1 versus Th2 cytokines observed. However, B7.1 molecules, absent from wild-type counterparts, were detected on germinal center B cells isolated from the deficient mice suggesting a modification of costimulatory signaling. A second alteration involved impaired de novo synthesis of C3 both in serum and germinal center cells from IL-6–deficient mice. Indeed, C3 provided an essential stimulatory signal for wild-type germinal center cells as both monoclonal antibodies that interrupted C3-CD21 interactions and sheep anti–mouse C3 antibodies caused a significant decrease in antigen-specific antibody production. In addition, germinal center cells isolated from C3–deficient mice produced a similar defect in isotype production. Low density cells with dendritic morphology were the local source of IL-6 and not the germinal center lymphocytes. Adding IL-6 in vitro to IL-6–deficient germinal center cells stimulated cell cycle progression and increased levels of antibody production. These findings reveal that the germinal center produces and uses molecules of the innate immune system, evolutionarily pirating them in order to optimally generate high affinity antibody responses.  相似文献   
64.
65.
66.
67.
68.
The Proceedings of the Round Table Conference will be published as volume 19, in the series Update in Intensive Care and Emergency Medicine (Springer Verlag) in January, 1995.  相似文献   
69.
70.
We have previously demonstrated an estradiol-regulated 24 kDa (24K) protein in human breast cancer tissue culture cells and human tumor biopsies. The presence of 24K correlates well with the presence of steroid hormone receptors. In order to further study the hormonal regulation of the 24K protein and gene, we have isolated cDNA clones corresponding to the 24K mRNA.Poly(A)+ RNA isolated from the MCF-7 human breast cancer cell line was translated in a cell-free translation system containing [35S]-methionine. The translation products were immunoprecipitated with a 24K monoclonal antibody, and thein vitro synthesis of 24K protein was confirmed by sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis. The same poly(A)+ RNA was used to construct an oligo(dT)-primed cDNA library in thegt11 expression vector system. The library was screened with a highly specific polyclonal antibody raised against 24K protein purified by immunoaffinity chromatography. Four recombinant clones reacting with the antibody by virtue of antigen expression were isolated and three were used in hybridization-selected translation. Three clones were able to hybridize specifically to a messenger RNA (mRNA) that yielded a Mr 24,000 protein when translatedin vitro and analyzed by SDS/polyacrylamide gel electrophoresis. This protein was also immunoprecipitable by the 24K monoclonal antibody. MCF-7 mRNA size fractionated by formaldehyde-agarose gel electrophoresis was transferred to nitrocellulose paper and hybridized to a nick-translated 24K cDNA clone. A single band of hybridization corresponding to a mRNA size of approximately 0.9–1.0 kilobase (kb) was observed. Using this same technique, 24K cDNA was hybridized to mRNA extracted from MCF-7 cells that had been treated for varying periods with either estradiol, nafoxidine, or tamoxifen. The 24K mRNA was elevated by the addition of estradiol, and clearly diminished by nafoxidine and tamoxifen.These results demonstrate that we have isolated cDNA clones for the study of the hormonal regulation of the 24K gene in breast cancer cells, and have shown that the mRNA is regulated by estradiol.  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