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   5640篇
  免费   465篇
  国内免费   16篇
耳鼻咽喉   38篇
儿科学   160篇
妇产科学   258篇
基础医学   793篇
口腔科学   80篇
临床医学   896篇
内科学   878篇
皮肤病学   104篇
神经病学   413篇
特种医学   93篇
外科学   508篇
综合类   122篇
一般理论   10篇
预防医学   781篇
眼科学   39篇
药学   520篇
中国医学   4篇
肿瘤学   424篇
  2023年   22篇
  2022年   39篇
  2021年   93篇
  2020年   60篇
  2019年   104篇
  2018年   122篇
  2017年   97篇
  2016年   133篇
  2015年   134篇
  2014年   173篇
  2013年   278篇
  2012年   415篇
  2011年   430篇
  2010年   264篇
  2009年   213篇
  2008年   395篇
  2007年   382篇
  2006年   359篇
  2005年   359篇
  2004年   337篇
  2003年   288篇
  2002年   280篇
  2001年   101篇
  2000年   66篇
  1999年   74篇
  1998年   56篇
  1997年   50篇
  1996年   51篇
  1995年   58篇
  1994年   29篇
  1993年   40篇
  1992年   44篇
  1991年   35篇
  1990年   27篇
  1989年   24篇
  1988年   22篇
  1987年   39篇
  1986年   30篇
  1985年   39篇
  1984年   30篇
  1983年   21篇
  1981年   21篇
  1979年   25篇
  1978年   16篇
  1974年   15篇
  1973年   13篇
  1972年   22篇
  1971年   20篇
  1970年   17篇
  1967年   13篇
排序方式: 共有6121条查询结果,搜索用时 31 毫秒
51.
Alcohol use disorders in persons with co-occurring psychiatric disorders are associated with high rates of psy-chosocial instability and poorer treatment outcomes. Thus, assessment of alcohol use and abuse should become an integral part of psychiatric care. Because setf-report-based measures are frequently used, issues of reliability and validity in this population should be critically examined. The purpose of this article is to review and critique the existing empirical literature that has evaluated the psychometric integrity of self- report-based measures in psychiatric settings, and to outline a research agenda that promises to enhance the accuracy of alcohol assessment by persons receiving psychiatric treatment.  相似文献   
52.
The prophylactic and therapeutic effects of gold sodium thiomalate, cyclosporin A, cyclophosphamide, and placebo on collagen-induced arthritis (CIA) were evaluated in DA rats. Prophylactic treatment with cyclosporin A and cyclophosphamide suppressed the arthritis incidence, clinical inflammation, destructive bone changes, and development of anti-collagen antibody in DA rats subsequently injected with porcine type-II collagen. Therapeutic treatment with cyclosporin A and cyclophosphamide had a definite suppression on established CIA when started 21 days after the initial collagen injection, but the suppression was less marked than that of prophylactic treatment. Gold had no impact on CIA in DA rats when administered either prophylactically or therapeutically.  相似文献   
53.
Phenotypic characterization of regulatory CD4+CD25+ T cells in rats   总被引:8,自引:0,他引:8  
CD25 has become widely used as a marker for a subset of regulatory CD4(+) T cells present in the thymus and periphery of mice, rats and humans. However, CD25 is also expressed on conventionally activated T cells that are not regulatory and not all peripheral regulatory T cells express CD25. The identification of a stable and unique marker for regulatory T cells would therefore be valuable. This study provides a detailed account of the phenotype of CD4(+)CD25(+) regulatory T cells in rats. In the thymus, CD4(+)CD8(-)CD25(+) cells were found to have a more mature phenotype than the corresponding CD4(+)CD8(-)CD25(-) cells with respect to expression of Thy1 (CD90), CD53 and CD44, suggesting that CD25 expression, and perhaps commitment to regulatory function, might be a late event in thymocyte development. CD4(+)CD25(+) cells in both the thymus and periphery were found to have enriched and heterogeneous expression of activation markers such as OX40 (CD134) and OX48 (an antibody determined in this study to be specific for CD86). CD4(+)CD25(+) T cells were also found to have enriched expression of CD80, at both the mRNA and protein level. However, functional studies in vitro and in vivo showed that neither OX40 or CD86 were useful markers for the further subdivision of regulatory T cells. Our studies indicate that, at present, CD25 remains the most useful marker to enrich for regulatory CD4(+) T cells in rats and no further subdivision of the regulatory component of CD4(+)CD25(-)CD45RC(low) T cells has yet been achieved.  相似文献   
54.
Genetic linkage analysis has been instrumental in mapping thegene for X-linked agammaglobulinemia (XLA) to the proximal longarm of the human X chromosome, to Xq22. Due to the relativerarity of this disease the localization of the gene within Xq22has remained imprecise. We have investigated twenty-nine familiesaffected by XLA and have found no recombinants with the DXS178locus in over 30 informative meioses. DXS178 is now the mostreliable and informative locus for use in pre-natal diagnosisand carrier detection of XLA. In addition, we have identifiednew closely linked proximal and distal flanking markers forXLA, DXS442 and DXS101, respectively. These loci are separatedby 2cM, considerably reducing the extent of DNA within whichthe XLA locus can be contained. This will open up the way formore directed positional cloning efforts for the isolation ofthe XLA gene.  相似文献   
55.
The ligand for the T cell antigen CD2 is CD48 in rodents, but CD58 in humans. The extracelluar parts of these three antigens are structurally related in that all contain two immunoglobulin superfamily (IgSF) domains. There have been reports of alternative ligands for CD2 in the human, but not so far in rodents. We describe the analysis of ligands for rat CD2 and CD48 using fluorescent beads capable of displaying a high ligand density and detecting low-affinity interactions like that of CD2 with CD48 (Kd = 60 ? 90 μM). Monovalent chimeric proteins containing the two IgSF domains of rat CD48 or CD2 and domains 3 and 4 of rat CD4 (CD4d3+4) were anchored to fluorescent covaspheresTM via a CD4 monoclonal antibody (mAb) with the CD48 or CD2 domains available for ligand binding. Multivalent CD48-CD4d3 + 4 covaspheresTM gave strong specific binding to rat CD2 expressed on the surface of transfected Jurkat cells. CD48-CD4d3+4 was compared with CD48-IgG and CD48-IgM as tools for detecting binding at the cell surface. Soluble divalent CD48-IgG and decavalent CD48-IgM bound to soluble CD2 with a Koff of around 10?3 s?1 as determined using a BIAcoreTM biosensor. However, binding to cells by CD48-IgG and CD48-IgM was only detectable when they were immobilized on covaspheresTM and represented no increase in sensitivity over CD48-CD4 covaspheresTM when tested for binding to cells expressing high and low levels of CD2. CD48-CD4d3 + 4 covaspheresTM only bound to rat cells expressing CD2. In the reverse orientation, binding of CD2-CD4d3 + 4 covaspheresTM was dependent on expression of CD48. Pre-incubation of cells with CD2 or CD48 mAb abolished all binding of CD48-CD4d3 + 4 or CD2-CD4d3 + 4, respectively. The data provide no evidence for an alternative ligand for rat CD2 or CD48.  相似文献   
56.
Familial XY gonadal dysgenesis   总被引:2,自引:0,他引:2  
  相似文献   
57.
In this article Susan Mallett and Neil Barclay discuss the molecular and functional features of a new superfamily of membrane proteins defined by the presence of cysteine-rich motifs originally identified in the low-affinity nerve growth factor receptor. This superfamily includes two lymphocyte proteins of unknown function and two receptors for tumor necrosis factor.  相似文献   
58.
59.
The nuclear-encoded Krebs cycle enzymes, fumarate hydratase (FH) and succinate dehydrogenase (SDHB, -C and -D), act as tumour suppressors. Germline mutations in FH predispose individuals to leiomyomas and renal cell cancer (HLRCC), whereas mutations in SDH cause paragangliomas and phaeochromocytomas (HPGL). In this study, we have shown that FH-deficient cells and tumours accumulate fumarate and, to a lesser extent, succinate. SDH-deficient tumours principally accumulate succinate. In situ analyses showed that these tumours also have over-expression of hypoxia-inducible factor 1alpha (HIF1alpha), activation of HIF1alphatargets (such as vascular endothelial growth factor) and high microvessel density. We found no evidence of increased reactive oxygen species in our cells. Our data provide in vivo evidence to support the hypothesis that increased succinate and/or fumarate causes stabilization of HIF1alpha a plausible mechanism, inhibition of HIF prolyl hydroxylases, has previously been suggested by in vitro studies. The basic mechanism of tumorigenesis in HPGL and HLRCC is likely to be pseudo-hypoxic drive, just as it is in von Hippel-Lindau syndrome.  相似文献   
60.
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