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   155987篇
  免费   31602篇
  国内免费   2393篇
耳鼻咽喉   5262篇
儿科学   5534篇
妇产科学   2591篇
基础医学   3826篇
口腔科学   1580篇
临床医学   27176篇
内科学   48095篇
皮肤病学   7672篇
神经病学   15093篇
特种医学   6620篇
外国民族医学   1篇
外科学   42034篇
综合类   279篇
现状与发展   72篇
一般理论   8篇
预防医学   7420篇
眼科学   3458篇
药学   1293篇
中国医学   10篇
肿瘤学   11958篇
  2024年   687篇
  2023年   4811篇
  2022年   1212篇
  2021年   3124篇
  2020年   6096篇
  2019年   2217篇
  2018年   7445篇
  2017年   7390篇
  2016年   8499篇
  2015年   8517篇
  2014年   15622篇
  2013年   15773篇
  2012年   5695篇
  2011年   5683篇
  2010年   10491篇
  2009年   14352篇
  2008年   5957篇
  2007年   4209篇
  2006年   6684篇
  2005年   3968篇
  2004年   3190篇
  2003年   2169篇
  2002年   2258篇
  2001年   3984篇
  2000年   3212篇
  1999年   3365篇
  1998年   3723篇
  1997年   3514篇
  1996年   3401篇
  1995年   3255篇
  1994年   1989篇
  1993年   1598篇
  1992年   1475篇
  1991年   1502篇
  1990年   1190篇
  1989年   1268篇
  1988年   1080篇
  1987年   927篇
  1986年   962篇
  1985年   798篇
  1984年   623篇
  1983年   587篇
  1982年   557篇
  1981年   437篇
  1980年   409篇
  1979年   386篇
  1978年   371篇
  1977年   447篇
  1975年   346篇
  1972年   353篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
This paper reports the proceedings of the discussion panel assigned to look at clinical aspects of quality in emergency medicine. One of the seven stated objectives of the Academic Emergency Medicine consensus conference on quality in emergency medicine was to educate emergency physicians regarding quality measures and quality improvement as essential aspects of the practice of emergency medicine. Another topic of interest was a discussion of the value of information technology in facilitating quality care in the clinical practice of emergency medicine. It is important to note that this is not intended to be a comprehensive review of this extensive topic, but instead is designed to report the discussion that occurred at this session of the consensus conference.  相似文献   
42.
43.
This study evaluates the potential for endothelial seeding of a collagen-impregnated Dacron graft with or without surface modifiers (fibronectin, heparin) to attach and retain these cells during flow. Human umbilical endothelial cells were harvested, cultured, labeled with Indium111-oxine and seeded onto 30 mm X 4 mm diameter grafts. Six graft surfaces were studied: 1) a collagen-impregnated Dacron graft, HemashieldR (C); 2) C + fibronectin (C + F); 3) C + heparin (C + H); 4) C + F + H; 5) HytrelR + F (Hyt + F); and 6) Hyt + F + H. Radioactive loss determined the percentage attachment and then percentage retention of labeled inoculum after a one-hour in vitro perfusion. Scanning electron and light microscopy demonstrated the endothelium on the graft surface following perfusion. Fibronectin-coated grafts had a significantly higher percentage attachment than those without fibronectin (ANOVA, P less than 0.05). However, the percentage retention following perfusion was similar for all Dacron grafts and statistically inferior to the HytrelR grafts studied (ANOVA, P less than 0.05). SEM evaluation of the C + F + H graft surface was qualitatively the most impressive Dacron surface for seeding, yet was inferior to the HytrelR graft. We conclude that fibronectin benefits the initial attachment of endothelium to collagen-coated Dacron rivaling the HytrelR surface. Fibronectin does not improve percentage retention of the HemashieldR surface during perfusion, therefore, some of its initial benefit is lost.  相似文献   
44.
Objective: The study goal was to compare the laser spot size created using reflective and refractive micromanipulators with a CO2 laser and to determine the sensitivity of spot size to laser power. Study Design and Setting: A CO2 laser and operating microscope (400-mm focal length) was coupled to either a reflective (Cassegrain-like) or refractive micromanipulator. Laser spot size was determined by measuring the region of ablation created by laser irradiation of wood (dry tongue depressors), exposed photographic film, and agar gel using optical micrometry. Laser power varied from 0.5 to 20 W with pulse durations of 0.1 and 0.5 second. Results: The reflective micromanipulator demonstrated overall smaller spot sizes for a given laser power and lower incremental change in spot size with increasing power. The reflective design demonstrated less sensitivity to increases in laser power. Conclusions: Micromanipulator optical design can result in significant differences in laser spot size. The reflective device used in this study demonstrated less sensitivity to increasing laser power. (Otolaryngol Head Neck Surg 2002;126:593-597.)  相似文献   
45.
46.
Although lesions of the pterygopalatine space are uncommon, there are instances in which this relatively inaccessible region must be entered for biopsy or excision of masses. Traditional open approaches to the pterygopalatine space, involving external or intraoral incisions, provide limited visualization and carry associated morbidities. The evolution and advancement of endoscopic sinus surgical technique in recent years has led to its application to anatomic areas outside the strict limits of the sinonasal cavities. Such minimally invasive approaches are safe, effective, and spare unnecessary discomfort to the patient. This article describes the authors' method for performing an endoscopic approach to the pterygopalatine space.  相似文献   
47.
48.
49.
50.
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