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   3524534篇
  免费   267068篇
  国内免费   6883篇
耳鼻咽喉   49755篇
儿科学   112248篇
妇产科学   94746篇
基础医学   496118篇
口腔科学   103175篇
临床医学   321263篇
内科学   681933篇
皮肤病学   74925篇
神经病学   286579篇
特种医学   136663篇
外国民族医学   1084篇
外科学   531484篇
综合类   84093篇
现状与发展   5篇
一般理论   1417篇
预防医学   278909篇
眼科学   84249篇
药学   262668篇
  11篇
中国医学   7517篇
肿瘤学   189643篇
  2018年   37674篇
  2017年   28796篇
  2016年   31848篇
  2015年   36062篇
  2014年   51264篇
  2013年   77098篇
  2012年   105027篇
  2011年   110989篇
  2010年   65732篇
  2009年   62081篇
  2008年   104365篇
  2007年   111133篇
  2006年   112073篇
  2005年   108746篇
  2004年   104719篇
  2003年   100475篇
  2002年   98260篇
  2001年   166823篇
  2000年   172070篇
  1999年   144854篇
  1998年   41168篇
  1997年   36710篇
  1996年   36389篇
  1995年   35194篇
  1994年   32860篇
  1993年   30465篇
  1992年   114871篇
  1991年   111206篇
  1990年   107297篇
  1989年   103639篇
  1988年   95713篇
  1987年   94018篇
  1986年   88874篇
  1985年   84782篇
  1984年   63829篇
  1983年   54397篇
  1982年   32227篇
  1981年   28776篇
  1979年   58811篇
  1978年   41075篇
  1977年   34905篇
  1976年   32663篇
  1975年   34483篇
  1974年   42442篇
  1973年   40491篇
  1972年   37912篇
  1971年   35008篇
  1970年   32881篇
  1969年   30595篇
  1968年   28093篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
Continual loading and articulation cycles undergone by metallic (e.g., titanium) alloy arthroplasty prostheses lead to liberation of a large number of metallic debris particulates, which have long been implicated as a primary cause of periprosthetic osteolysis and postarthroplasty aseptic implant loosening. Long-term stability of total joint replacement prostheses relies on proper integration between implant biomaterial and osseous tissue, and factors that interfere with this integration are likely to cause osteolysis. Because multipotent mesenchymal stem cells (MSCs) located adjacent to the implant have an osteoprogenitor function and are critical contributors to osseous tissue integrity, when their functions or activities are compromised, osteolysis will most likely occur. To date, it is not certain or sufficiently confirmed whether MSCs endocytose titanium particles, and if so, whether particulate endocytosis has any effect on cellular responses to wear debris. This study seeks to clarify the phenomenon of titanium endocytosis by human MSCs (hMSCs), and investigates the influence of endocytosis on their activities. hMSCs incubated with commercially pure titanium particles exhibited internalized particles, as observed by scanning electron microscopy and confocal laser scanning microscopy, with time-dependent reduction in the number of extracellular particles. Particulate endocytosis was associated with reduced rates of cellular proliferation and cell-substrate adhesion, suppressed osteogenic differentiation, and increased rate of apoptosis. These cellular effects of exposure to titanium particles were reduced when endocytosis was inhibited by treatment with cytochalasin D, and no significant effect was seen when hMSCs were treated only with conditioned medium obtained from particulate-treated cells. These findings strongly suggest that the biological responses of hMSCs to wear debris are triggered primarily by the direct endocytosis of titanium particulates, and not mediated by secreted soluble factors. In this manner, therapeutical approaches that suppress particle endocytosis could reduce the bioreactivity of hMSCs to particulates, and enhance long-term orthopedic implant prognosis by minimizing wear-debris periprosthethic osteolysis.  相似文献   
84.
85.
86.
87.
88.
89.
90.
Pre-eclamptic toxaemia (PET) may be associated with both endothelial dysfunction (ED) and sleep-disordered breathing (SDB). It was hypothesised that females with PET would demonstrate both SDB and ED, and that a correlation between these two would suggest a potential causative association. A total of 17 females with PET and 25 matched females with uncomplicated pregnancy were studied. They underwent a nocturnal ambulatory sleep study (using Watch_PAT100) and noninvasive evaluation of endothelial function utilising the reactive hyperaemia test (using Endo_PAT 2000). A higher ratio of post- to pre-occlusion pulse-wave amplitude (endothelial function index (EFI)) indicated better endothelial function. Females with PET had a significantly higher respiratory disturbance index (RDI) and lower EFI than controls (18.4+/-8.4 versus 8.3+/-1.3.h(-1), and 1.5+/-0.1 versus 1.8+/-0.1, respectively). Blood pressure significantly correlated with RDI and with EFI. EFI tended to correlate with RDI. In conclusion, these results suggest that both sleep-disordered breathing and endothelial dysfunction are more likely to occur in females with pre-eclamptic toxaemia than in females with uncomplicated pregnancies. The current authors speculate that respiratory disturbances contribute to the functional abnormality of the blood vessels seen in females with pre-eclamptic toxaemia, although causality cannot be determined based on this study.  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