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   1274789篇
  免费   94257篇
  国内免费   1984篇
耳鼻咽喉   18205篇
儿科学   42295篇
妇产科学   37889篇
基础医学   186975篇
口腔科学   35377篇
临床医学   108045篇
内科学   251178篇
皮肤病学   26518篇
神经病学   99188篇
特种医学   50026篇
外国民族医学   366篇
外科学   197587篇
综合类   26504篇
现状与发展   1篇
一般理论   301篇
预防医学   92446篇
眼科学   29026篇
药学   97809篇
  1篇
中国医学   2505篇
肿瘤学   68788篇
  2018年   11840篇
  2015年   11644篇
  2014年   16034篇
  2013年   24400篇
  2012年   33614篇
  2011年   36016篇
  2010年   21257篇
  2009年   20058篇
  2008年   35058篇
  2007年   38018篇
  2006年   38571篇
  2005年   37859篇
  2004年   36465篇
  2003年   35430篇
  2002年   34971篇
  2001年   58115篇
  2000年   59606篇
  1999年   50706篇
  1998年   14244篇
  1997年   12818篇
  1996年   13082篇
  1995年   12354篇
  1994年   11767篇
  1993年   10864篇
  1992年   40991篇
  1991年   40373篇
  1990年   39895篇
  1989年   38713篇
  1988年   36116篇
  1987年   35353篇
  1986年   33732篇
  1985年   32139篇
  1984年   23924篇
  1983年   20824篇
  1982年   12379篇
  1981年   10928篇
  1980年   10206篇
  1979年   22626篇
  1978年   15835篇
  1977年   13684篇
  1976年   12933篇
  1975年   14167篇
  1974年   16663篇
  1973年   16044篇
  1972年   15308篇
  1971年   14223篇
  1970年   13204篇
  1969年   12721篇
  1968年   11970篇
  1967年   10458篇
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
51.
Delayed contrast enhancement after injection of a gadolinium-chelate (Gd-chelate) is a reference imaging method to detect myocardial tissue changes. Its localization within the thickness of the myocardial wall allows differentiating various pathological processes such as myocardial infarction (MI), inflammatory myocarditis, and cardiomyopathies. The aim of the study was first to characterize benign myocarditis using quantitative delayed-enhancement imaging and then to investigate whether the measure of the extracellular volume fraction (ECV) can be used to discriminate between MI and myocarditis.In 6 patients with acute benign myocarditis (32.2 ± 13.8 year-old, subepicardial late gadolinium enhancement [LGE]) and 18 patients with MI (52.3 ± 10.9 year-old, subendocardial/transmural LGE), myocardial T1 was determined using the Modified Look-Locker Imaging (MOLLI) sequence at 3 Tesla before and after Gd-chelate injection. T1 values were compared in LGE and normal regions of the myocardium. The myocardial T1 values were normalized to the T1 of blood, and the ECV was calculated from T1 values of myocardium and blood pre- and post-Gd injection.In both myocarditis and MI, the T1 was lower in LGE regions than in normal regions of the left ventricle. T1 of LGE areas was significantly higher in myocarditis than in MI (446.8 ± 45.8 vs 360.5 ± 66.9 ms, P = 0.003) and ECV was lower in myocarditis than in MI (34.5 ± 3.3 vs 53.8 ± 13.0 %, P = 0.004).Both inflammatory process and chronic fibrosis induce LGE (subepicardial in myocarditis and subendocardial in MI). The present study demonstrates that the determination of T1 and ECV is able to differentiate the 2 histological patterns.Further investigation will indicate whether the severity of ECV changes might help refine the predictive risk of LGE in myocarditis.  相似文献   
52.
53.
54.
The aim of the present study was to evaluate the antimicrobial activity of two synbiotic combinations, Lactobacillus fermentum with short-chain fructooligosaccharides (FOS-LF) and Bifidobacterium longum with isomaltooligosaccharides (IMO-BL), against enterohaemorrhagic Escherichia coli O157:H7 and enteropathogenic E. coli O86. Antimicrobial activity was determined (1) by co-culturing the synbiotics and pathogens in batch cultures, and (2) with the three-stage continuous culture system (gut model), inoculated with faecal slurry from an elderly donor. In the co-culture experiments, IMO-BL was significantly inhibitory to both E. coli strains, while FOS-LF was slightly inhibitory or not inhibitory. Factors other than acid production appeared to play a role in the inhibition. In the gut models, both synbiotics effectively inhibited E. coli O157 in the first vessel, but not in vessels 2 and 3. E. coli O86 was not significantly inhibited.  相似文献   
55.
56.
57.

Background

Arterial vascular anomalies in patients undergoing kidney transplantation (KT) are correlated with a higher incidence of early surgical complications, potentially causing graft loss. Arterial reconstruction allows patients to overcome these surgical challenges, thus minimizing the risk of poor outcomes. The aim of the present study is to retrospectively investigate the safety and effectiveness of the multiple arterial reconstruction technique with a Teflon patch in case of an unavailable aortic patch: to do so, surgical complications, graft function, and patient survival were evaluated.

Methods

During the period January 2009 to August 2016, 202 adult deceased-donor KTs were performed at our center. Group A (n = 27; reconstruction of multiple arteries) and Group B (n = 175; control group) were compared.

Results

No differences were observed between the 2 groups in terms of early postoperative course, with no vascular complication observed in Group A. No vascular patch infections were reported, nor longer cold ischemia time rates. Similarly, long-term survival rates were similar between the 2 groups.

Conclusions

The Teflon-patch arterial reconstruction technique appears to be safe and effective, with an acceptable balance of benefits and potential risks of using a prosthetic material. Studies based on larger series are needed to further validate this approach.  相似文献   
58.
59.
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