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   14523篇
  免费   1324篇
  国内免费   50篇
耳鼻咽喉   118篇
儿科学   558篇
妇产科学   276篇
基础医学   1791篇
口腔科学   326篇
临床医学   1608篇
内科学   2781篇
皮肤病学   188篇
神经病学   1359篇
特种医学   781篇
外科学   2025篇
综合类   367篇
一般理论   18篇
预防医学   1389篇
眼科学   375篇
药学   1066篇
  1篇
中国医学   10篇
肿瘤学   860篇
  2022年   134篇
  2021年   237篇
  2020年   153篇
  2019年   253篇
  2018年   310篇
  2017年   227篇
  2016年   252篇
  2015年   311篇
  2014年   389篇
  2013年   554篇
  2012年   813篇
  2011年   804篇
  2010年   481篇
  2009年   411篇
  2008年   712篇
  2007年   736篇
  2006年   718篇
  2005年   681篇
  2004年   701篇
  2003年   590篇
  2002年   604篇
  2001年   372篇
  2000年   346篇
  1999年   334篇
  1998年   241篇
  1997年   209篇
  1996年   194篇
  1995年   147篇
  1994年   155篇
  1993年   173篇
  1992年   288篇
  1991年   265篇
  1990年   215篇
  1989年   235篇
  1988年   219篇
  1987年   206篇
  1986年   189篇
  1985年   172篇
  1984年   128篇
  1983年   109篇
  1982年   94篇
  1981年   93篇
  1980年   107篇
  1979年   88篇
  1978年   94篇
  1977年   87篇
  1976年   96篇
  1974年   75篇
  1973年   94篇
  1972年   86篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
Members of the Poxviridae family are particularly adept at avoiding the host immune system, encoding a plethora of immunomodulatory proteins that subvert host defense. With their large genome, poxviruses are also useful for studying the effect of exogenous genes on virus-host interactions and immune responses. The insertion of the Th2 cytokine interleukin-4 (IL-4) into several poxviruses significantly increases the efficiency of the recombinant virus as a pathogen by directly inhibiting the development of Th1 immunity, which is crucial for viral clearance. In an age in which the fear of genetically modified weaponized pathogens exists, the understanding of how to make viruses more pathogenic further blurs the distinction between fundamental academic research and bioweapons development. Here, the extent of immune evasion by IL-4-expressing poxviruses will be explored, as will the consequences of this increased pathogenicity on protective immune responses.  相似文献   
132.
Norepinephrine triggers release of glial ATP to increase postsynaptic efficacy   总被引:10,自引:0,他引:10  
Glial cells actively participate in synaptic transmission. They clear molecules from the synaptic cleft, receive signals from neurons and, in turn, release molecules that can modulate signaling between neuronal elements. Whether glial-derived transmitters can contribute to enduring changes in postsynaptic efficacy, however, remains to be established. In rat hypothalamic paraventricular nucleus, we demonstrate an increase in the amplitude of miniature excitatory postsynaptic currents in response to norepinephrine that requires the release of ATP from glial cells. The increase in quantal efficacy, which likely results from an insertion of AMPA receptors, is secondary to the activation of P2X(7) receptors, an increase in postsynaptic calcium and the activation of phosphatidylinositol 3-kinase. The gliotransmitter ATP, therefore, contributes directly to the regulation of postsynaptic efficacy at glutamatergic synapses in the CNS.  相似文献   
133.
134.
Summary The histological grades of prostatic carcinoma, as defined by Gleason, were correlated with three methods of morphometry in 254 step-sectioned prostates obtained at autopsy. The variables studied were 1) the number of tumours in each prostate; 2) bilaterality and 3) tumour volume. Each characteristic yielded a statistically significant correlation with histological grade. The strongest correlations were obtained using tumour volume. These autopsy studied help to explain the inconsistent results obtained from morphometric analyses of surgical material, and lend support to the Gleason system as a means of predicting tumour behavior.Supported in part by research contracts PH 64-10, NCI-72-3213, N01-CP-53521; Grant R01-CA-33644; and the Grant-in-Aid for Cancer Research (33) from the Ministry of Health and Welfare  相似文献   
135.
136.
137.
Like fetal fibroblasts and amniotic fluid cells, cultured chorionic villus cells can also be HLA typed with selected typing sera after preincubation with gamma interferon to promote better antigen expression. A modified procedure now in use would also allow any of these cell types to be tested for the presence or absence of all known HLA A,B,C, and DR antigens with standard preplated typing trays. This procedure was used to confirm that an on-going pregnancy had resulted from the successful in vitro fertilization and implantation of an anonymous donor's ovum and could also be of major use in rape or artificial insemination cases when the identity of the possible father(s) is not known.  相似文献   
138.
We used the short-circuit current (I(sc)) and patch-clamp techniques to investigate the effects of methoxsalen (MTX) on the electrogenic Cl- secretion of the mouse jejunum. MTX stimulated a sustained increase in Isc that was dose dependent. Bumetanide inhibited MTX-stimulated Isc in a dose-dependent manner consistent with activation of Cl- secretion. MTX failed to stimulate I(sc) following maximal activation of the cAMP pathway by forskolin, but did increase Isc after a submaximal dose of forskolin. Glibenclamide, a blocker of the cystic fibrosis transmembrane conductance regulator (CFTR), reduced the MTX-stimulated increase of Isc by 59 +/- 6%. The cAMP-dependent K+ channel blocker 293B did not alter the MTX-activated I(sc); however, clotrimazole, an intermediate Ca2(+)-activated K+ channel (IK(Ca)) blocker, reduced the MTX-stimulated I(sc). MTX did not alter Na(+)-glucose cotransport across the mouse jejunum. In cell-attached membrane patches, MTX increased the open probability of the basolateral IK(Ca) channel of isolated crypts. These data suggest that the CFTR and IK(Ca) channels participate in the MTX-activated, sustained Cl- secretory response of the mouse jejunum.  相似文献   
139.
Experiencing adverse life events during childhood may increase vulnerability to physical illnesses and psychological disorders during adulthood. We developed an Early Life Events Questionnaire (ELEQ) with 12 scales and administered it to 92 relatively healthy elderly individuals (29 men and 63 women). A canonical-correlation analysis of the 12 ELEQ scales and physical and psychological symptoms revealed a significant canonical correlation. The results indicate that those who grew up in a family with a harsh climate and whose affiliation needs were not met tended to have more psychological and physical symptoms in old age. Regression analysis revealed that, in men, early life events accounted for 42% of the variance in physical symptoms and 39% in psychological symptoms. No significant relationship, however, was found between ELEQ scales and health outcomes in women. These results suggest that women may be less vulnerable than men to the adverse health consequences of childhood deprivation and other misfortunes.This work was supported by Award SA 325 from the Medical Research Service of the Department of Veterans Affairs.  相似文献   
140.
Verticillium dahliae is an important soil-borne fungal pathogen that causes vascular wilt diseases in a large variety of important crop plants. Due to its persistence in the soil, control of Verticillium wilt relies heavily on soil fumigation. The global ban on methyl bromide, a highly effective soil fumigant, poses an urgent need to develop alternative control measures against Verticillium wilt; and these might be more forthcoming with a better understanding of the molecular and cellular mechanisms that underpin the pathogenicity of V. dahliae. In this study, we assessed the role in growth, development, and pathogenicity of VMK1, a gene encoding a mitogen-activated protein (MAP) kinase (hence, Verticillium MAP Kinase 1). Disruption of VMK1 via Agrobacterium tumefaciens-mediated transformation, in two V. dahliae isolates, one from lettuce and the other from tomato, resulted in severely reduced virulence in diverse host plants, suggesting that VMK1 is essential for pathogenicity and that the MAP kinase-mediated signaling pathway has a conserved role in fungal pathogenicity. The vmk1 mutants also exhibited reduced conidiation and microsclerotia formation, suggesting that the gene is important for multiple cellular processes. P.R. and R.G.B. equally contributed to the work  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