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   113410篇
  免费   4942篇
  国内免费   653篇
耳鼻咽喉   1818篇
儿科学   6380篇
妇产科学   2547篇
基础医学   10945篇
口腔科学   4046篇
临床医学   7774篇
内科学   25837篇
皮肤病学   3326篇
神经病学   7483篇
特种医学   5275篇
外科学   24168篇
综合类   1935篇
预防医学   5920篇
眼科学   2246篇
药学   5430篇
  2篇
中国医学   725篇
肿瘤学   3148篇
  2023年   3458篇
  2022年   4121篇
  2021年   5717篇
  2020年   4315篇
  2019年   11579篇
  2018年   8731篇
  2017年   4258篇
  2016年   1346篇
  2015年   1933篇
  2014年   2579篇
  2013年   1272篇
  2012年   802篇
  2011年   4229篇
  2010年   1206篇
  2009年   1619篇
  2008年   1710篇
  2007年   1211篇
  2006年   1000篇
  2005年   1529篇
  2004年   1590篇
  2003年   1081篇
  2002年   1645篇
  2001年   1968篇
  2000年   3010篇
  1999年   3354篇
  1998年   3134篇
  1997年   2150篇
  1996年   1461篇
  1995年   1003篇
  1994年   1062篇
  1993年   729篇
  1992年   829篇
  1991年   642篇
  1990年   670篇
  1989年   446篇
  1988年   498篇
  1987年   313篇
  1985年   3072篇
  1984年   4305篇
  1983年   3102篇
  1982年   3022篇
  1981年   2813篇
  1980年   2435篇
  1979年   2248篇
  1978年   1914篇
  1977年   1733篇
  1976年   1851篇
  1975年   1439篇
  1974年   1269篇
  1973年   1204篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
中药蜈蚣对小鼠胚胎发育的影响   总被引:2,自引:0,他引:2  
孕鼠161只随机分组,在孕期第7-11天给实验组分别以500mg/(kg.d)(蜈蚣1组)及1000mg/(kg.d)(蜈蚣2组)的中药蜈蚣煎剂灌胃,至孕期18天记录各组孕鼠和胎鼠的发育情况。结果表明:蜈蚣1,2两组致畸作用明显,死胎,吸收胎比例升高;蜈蚣2组胎鼠和孕鼠的体重均下降,堕胎作用显著,与对照组比较,差异均有非常显著意义(P<0.01)。  相似文献   
992.
In the original version of this article, the title was incorrect. Please find the correct title given here. The publisher deeply regrets this error. The original article to which this Erratum refers was published in Human Mutation 22:179–180 Human Mutation(2003) 22(2) 179–180  相似文献   
993.
The organization of chains of oligopeptidoglycan in the saccular wall is of critical importance in the study of the mechanism and physiology of prokaryotic wall growth. The electron microphotographs of De Pedro et al, present new findings and can be used to negate or at least raise questions about the previously accepted conclusion that the glycan chains are oriented transversely to the axis of rod-shaped Escherichia coli. This suggests caution in assuming that the glycan chains in the murein structure are parallel to each other and are perpendicular to the axis of the cell.These results should reopen the question of not only the orientation of the peptidoglycan chains, but the possibility of variability in orientation. Three classes of hypotheses about wall growth are reconsidered and problems with them are presented. The new results from De Pedro's laboratory and the experimental glycan chain length distribution argue against proposed systematic models. These include models that postulate belts or hoops stretched around the circumference of the cell and mechanisms that insert new chains of the length of presumptive “docking” strands in the stress-bearing wall. They are consistent, however, with the surface stress theory that proposes that random enzyme action together with physical forces are involved in the elongation of the rod-shaped Gram-negative wall.  相似文献   
994.
The human immunodeficiency virus (HIV) induces neuronal death, presumably by apoptosis. This effect may be triggered by the glycoprotein 120 (HIVgp120) released by HIV when infecting a cell, and mediated by tumor necrosis factor alpha (TNF), a pro-inflammatory cytokine. Both molecules, HIVgp120 and TNF, increase sleep when administered acutely in the brain. On the other hand, sleep deprivation increases the levels of several growth factors. In this context, we challenged rats with HIVgp120 or TNF simultaneously with sleep deprivation. Our results indicate that both HIVgp120 and TNF increase neuronal death in the rat cerebral cortex, but not hippocampus, and that this effect is completely prevented by total deprivation of sleep. These results suggest that acute total deprivation of sleep protects against the HIVgp120 and TNF deleterious effects.  相似文献   
995.
CT快速图像重建算法研究   总被引:4,自引:0,他引:4  
快速图像重建算法一直是图像重建中的关键问题和衡量CT系统的重要指标之一。本文以扇形束结构为例,分析了各种快速重建算法的特点,并从算法结构、实现技巧及代码优化等方面论述了快速图像重建的方法.这些方法可有效地提高图像重建的速度。  相似文献   
996.
Atopy — a T helper 2 cell driven hypersensitivity to innocuous antigens (allergens) which causes most cases of asthma — is of complex genetic and environmental origins. There is compelling epidemiological evidence for a rise in atopic disease in ‘westernised’ communities. The changing pattern of microbial exposure in early childhood is suggested to be the principal candidate mechanism for this rise.  相似文献   
997.
Clostridium difficile infection (CDI) remains a major public health issue, and fecal microbiota transplantation (FMT) has become one of the standard therapies for recurrent or refractory CDI. When compared to medical therapies, such as metronidazole or vancomycin, FMT has a high rate of treatment response with acceptable safety and efficiency. Following promulgation of the amendments in September 2018 in Taiwan, FMT has been indicated for recurrent or refractory CDI. The Taiwan Microbiota Consortium contributed to the Taiwan FMT Expert Consensus, which established basic norms and stipulated essential principles, including the indications for transplantation, eligible locations and personnel, donor screening policies, fecal sample handling, and post-FMT follow-up. However, establishing an eligible FMT team in a qualified hospital remains a clinical challenge, and the requirement for facilities and well-screened donors impedes the implementation of FMT. In this review, we aim to provide domestic FMT teams with explicit instructions to facilitate realization and increase the practice of FMT. Based on the Taiwan FMT Expert Consensus and current regulations, we performed a literature review and integrated the experiences of Taiwanese multidisciplinary experts into this article. The content intends to offer clinicians up-to-date evidence and highlight the essential points of FMT.  相似文献   
998.
999.
A complex of rabbit IgG antibody with horseradish peroxidase covalently linked to Sepharose 4B was used as an insoluble immune complex for studying the binding of complement factor C1q protein A from Staphylococcus aureus, and its IgG-binding fragments AB and B, to rabbit IgG. It was shown that protein A (mol. wt approx. 42,000) and fragments AB and B (mol. wts approx. 14,000 and 7000, respectively) inhibited the binding of C1q to insoluble immune complex at 4 degrees C. However, at 37 degrees C fragment B did not inhibit this binding. On the other hand, C1q, when bound to an insoluble immune complex, almost completely blocked the binding of protein A and fragment B at both temps. The higher affinity of C1q for its CH2-binding site than of fragment B for its CH2-binding site may explain the displacement of the latter from the CH2 domain. The mutual inhibition of the binding of C1q and protein A (and its smaller fragments) indicates that the binding sites for C1q and protein A are closely located in the CH2 domain.  相似文献   
1000.
Twenty-four synovial sarcomas were examined for the presence of keratin proteins by an indirect immunoperoxidase method with paraffin-embedded tissues. Keratin proteins were identified in 16 of 24 cases (67 per cent). Both the pseudoglandular and spindle cell areas of all eight of the biphasic synovial sarcomas and the spindle cells of eight of the 16 monophasic synovial sarcomas contained keratin proteins. In spindle cell areas, staining was observed in single cells and small cords and clusters of cells in the absence of cleft formation or other evidence of a pseudoglandular component. The predominant cytologic staining pattern in all cases was peripheral, with localization of staining to the cell membrane or adjacent areas, but diffuse and focal cytoplasmic staining patterns were also observed. No staining for keratin proteins was seen in 101 control cases, including 52 sarcomas of various types. Carcinoembryonic antigen was also identified in four of the 24 synovial sarcomas by an indirect immunoperoxidase technique. The identification of keratin proteins may be helpful in the pathologic diagnosis of synovial sarcoma, particularly the spindle cell monophasic variant.  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