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   16713篇
  免费   1204篇
  国内免费   45篇
耳鼻咽喉   112篇
儿科学   402篇
妇产科学   276篇
基础医学   2190篇
口腔科学   619篇
临床医学   1658篇
内科学   3287篇
皮肤病学   203篇
神经病学   1606篇
特种医学   620篇
外科学   2166篇
综合类   150篇
一般理论   35篇
预防医学   1944篇
眼科学   279篇
药学   1227篇
中国医学   38篇
肿瘤学   1150篇
  2024年   22篇
  2023年   168篇
  2022年   267篇
  2021年   576篇
  2020年   356篇
  2019年   491篇
  2018年   557篇
  2017年   439篇
  2016年   453篇
  2015年   544篇
  2014年   669篇
  2013年   916篇
  2012年   1357篇
  2011年   1374篇
  2010年   842篇
  2009年   681篇
  2008年   1160篇
  2007年   1109篇
  2006年   1035篇
  2005年   1006篇
  2004年   923篇
  2003年   835篇
  2002年   679篇
  2001年   175篇
  2000年   115篇
  1999年   133篇
  1998年   141篇
  1997年   106篇
  1996年   84篇
  1995年   65篇
  1994年   66篇
  1993年   54篇
  1992年   57篇
  1991年   48篇
  1990年   48篇
  1989年   41篇
  1988年   34篇
  1987年   24篇
  1986年   33篇
  1985年   22篇
  1984年   38篇
  1983年   27篇
  1982年   24篇
  1981年   23篇
  1980年   15篇
  1979年   19篇
  1978年   19篇
  1976年   11篇
  1974年   11篇
  1973年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Mucosal vaccination via the respiratory tract can elicit protective immunity in animal infection models, but the underlying mechanisms are still poorly understood. We show that a single intranasal application of the replication-deficient modified vaccinia virus Ankara, which is widely used as a recombinant vaccination vector, results in prominent induction of bronchus-associated lymphoid tissue (BALT). Although initial peribronchiolar infiltrations, characterized by the presence of dendritic cells (DCs) and few lymphocytes, can be found 4 d after virus application, organized lymphoid structures with segregated B and T cell zones are first observed at day 8. After intratracheal application, in vitro–differentiated, antigen-loaded DCs rapidly migrate into preformed BALT and efficiently activate antigen-specific T cells, as revealed by two-photon microscopy. Furthermore, the lung-specific depletion of DCs in mice that express the diphtheria toxin receptor under the control of the CD11c promoter interferes with BALT maintenance. Collectively, these data identify BALT as tertiary lymphoid structures supporting the efficient priming of T cell responses directed against unrelated airborne antigens while crucially requiring DCs for its sustained presence.Bronchus-associated lymphoid tissue (BALT) is part of the mucosal immune system of the lung and is characterized by the aggregation of lymphoid cells at the bifurcations of the upper bronchioles (Bienenstock and Befus, 1984). Like other lymphoid follicles, BALT is composed of B cells surrounded by a parafollicular region of T cells (Sminia et al., 1989). Recirculating lymphocytes are believed to enter BALT via high endothelial venules and leave these structures by efferent lymphatics (Lührmann et al., 2002/2003; Xu et al., 2003). Although BALT is largely absent in normal mice, it spontaneously forms in mice deficient for the chemokine receptor CCR7 (Kocks et al., 2007). In humans, it is neither found at birth nor in healthy adults but transiently arises during childhood and adolescence (Tschernig and Pabst, 2000). In both humans and mice, pulmonary infection and inflammation can induce BALT (Moyron-Quiroz et al., 2004). Data derived from splenectomized lymphotoxin-α–deficient mice, which lack all secondary lymphoid organs but do develop BALT, suggest that BALT can serve as induction sites for adaptive immune responses to pathogens with lung tropism (Moyron-Quiroz et al., 2004). However, mechanisms that control the development and maintenance of BALT are largely unknown.Modified vaccinia virus Ankara (MVA) is a highly attenuated orthopoxvirus that lost its capacity to replicate in mammalian cells (Meyer et al., 1991). Recently, MVA was proposed to represent a useful agent for mucosal vaccination via the respiratory route in a nonhuman primate model (Corbett et al., 2008). In mice, MVA delivered via the intranasal (i.n.) route has been shown to induce long-lasting and protective antibody and T cell immune responses (Gherardi and Esteban, 2005; Kastenmuller et al., 2009). However, little is known about the immunological events after respiratory MVA infection.The present report demonstrates that a single i.n. application of the replication-deficient MVA is sufficient to induce the long-lasting presence of BALT and that the lung-specific depletion of DCs interferes with BALT maintenance. Ex vivo imaging of antigen-specific T cell–DC interactions within BALT by two-photon microscopy indicates that, independent of the specific antigenic challenge inducing its formation, BALT can function as a general priming site for T cell responses directed against antigens that reach the lower respiratory tract.  相似文献   
82.
83.
The global emergence of Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) multilocus sequence type ST258 is widely recognized. Less is known about the molecular and epidemiological details of non-ST258 K. pneumoniae in the setting of an outbreak mediated by an endemic plasmid. We describe the interplay of blaKPC plasmids and K. pneumoniae strains and their relationship to the location of acquisition in a U.S. health care institution. Whole-genome sequencing (WGS) analysis was applied to KPC-Kp clinical isolates collected from a single institution over 5 years following the introduction of blaKPC in August 2007, as well as two plasmid transformants. KPC-Kp from 37 patients yielded 16 distinct sequence types (STs). Two novel conjugative blaKPC plasmids (pKPC_UVA01 and pKPC_UVA02), carried by the hospital index case, accounted for the presence of blaKPC in 21/37 (57%) subsequent cases. Thirteen (35%) isolates represented an emergent lineage, ST941, which contained pKPC_UVA01 in 5/13 (38%) and pKPC_UVA02 in 6/13 (46%) cases. Seven (19%) isolates were the epidemic KPC-Kp strain, ST258, mostly imported from elsewhere and not carrying pKPC_UVA01 or pKPC_UVA02. Using WGS-based analysis of clinical isolates and plasmid transformants, we demonstrate the unexpected dispersal of blaKPC to many non-ST258 lineages in a hospital through spread of at least two novel blaKPC plasmids. In contrast, ST258 KPC-Kp was imported into the institution on numerous occasions, with other blaKPC plasmid vectors and without sustained transmission. Instead, a newly recognized KPC-Kp strain, ST941, became associated with both novel blaKPC plasmids and spread locally, making it a future candidate for clinical persistence and dissemination.  相似文献   
84.
85.
While the detrimental role of non-regulatory T cells in ischemic stroke is meanwhile unequivocally recognized, there are controversies about the properties of regulatory T cells (Treg). The aim of this study was to elucidate the role of Treg by applying superagonistic anti-CD28 antibody expansion of Treg. Stroke outcome, thrombus formation, and brain-infiltrating cells were determined on day 1 after transient middle cerebral artery occlusion. Antibody-mediated expansion of Treg enhanced stroke size and worsened functional outcome. Mechanistically, Treg increased thrombus formation in the cerebral microvasculature. These findings confirm that Treg promote thrombo-inflammatory lesion growth during the acute stage of ischemic stroke.  相似文献   
86.
87.
88.
89.
90.
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