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   743篇
  免费   43篇
  国内免费   37篇
耳鼻咽喉   3篇
儿科学   52篇
妇产科学   8篇
基础医学   63篇
口腔科学   17篇
临床医学   92篇
内科学   163篇
皮肤病学   7篇
神经病学   17篇
特种医学   162篇
外科学   36篇
综合类   12篇
预防医学   20篇
眼科学   92篇
药学   44篇
肿瘤学   35篇
  2024年   2篇
  2022年   3篇
  2021年   6篇
  2020年   6篇
  2019年   7篇
  2018年   15篇
  2017年   7篇
  2016年   6篇
  2015年   8篇
  2014年   15篇
  2013年   18篇
  2012年   15篇
  2011年   22篇
  2010年   44篇
  2009年   40篇
  2008年   22篇
  2007年   39篇
  2006年   19篇
  2005年   19篇
  2004年   15篇
  2003年   10篇
  2002年   10篇
  2001年   21篇
  2000年   9篇
  1999年   11篇
  1998年   48篇
  1997年   46篇
  1996年   45篇
  1995年   40篇
  1994年   42篇
  1993年   26篇
  1992年   3篇
  1991年   12篇
  1990年   12篇
  1989年   28篇
  1988年   23篇
  1987年   12篇
  1986年   15篇
  1985年   9篇
  1984年   7篇
  1983年   6篇
  1982年   10篇
  1981年   8篇
  1980年   10篇
  1979年   5篇
  1978年   6篇
  1977年   10篇
  1976年   6篇
  1975年   3篇
  1969年   1篇
排序方式: 共有823条查询结果,搜索用时 93 毫秒
101.
102.
Predictive value of normal sperm morphology: a structured literature review   总被引:12,自引:0,他引:12  
The aim of the study was to conduct a structured review of theliterature published on the use of normal sperm morphology,as an indicator of male fertility potential in the in-vitrofertilization (IVF) situation, and to establish the universalpredictive value of this semen parameter. Published literaturein which normal sperm morphology was used to predict fertilizationand pregnancy, during the period 1978-1996, was reviewed. Atotal of 216 articles were identified by the sourcing methodology,but only 49 provided data that could be tabulated and analysed.Of these, only 18 provided sufficient data for statistical analysis.Fifteen studies used the strict criteria to evaluate sperm morphology,two used World Health Organization (WHO) guidelines and oneused both the strict criteria and the WHO guidelines. All thestudies (n=10) using the 5 and 14% normal sperm morphology thresholds(strict criteria) produced positive predictive values for IVFsuccess. In the prediction of pregnancy, 82% (9/11) and 75%(6/8) of the studies produced positive predictive values whenusing the 5% and 14% thresholds respectively. Aggregating thedata produced around the 5% normal sperm morphology threshold(strict criteria), the overall fertilization rates were 59.3%(1979/3337; per oocyte) for the 4% group and 77.6% (10345/13327;per oocyte) for the >4% group, and the overall pregnancyrates were 15.2% (60/395; per cycle) and 26.0% (355/1368; percycle) respectively. The no-transfer rates across the 5% thresholdwere 24.0% (86/359; per cycle) in the 4% group compared to 7.4%(80/1088; per cycle) in the >4% group. The inclusion of anaccurately evaluated normal sperm morphology count as an integralpart of the standard semen analysis makes this analysis stillthe most cost-effective means of evaluating the male factor.  相似文献   
103.
Forty conventional radiographs with examples of mild interstitial infiltrates and subtle pneumothoraces and 40 normal studies of the chest were selected and digitized, with pixel sizes of 1.0, 0.5, 0.2, and 0.1 mm. Observer performance tests were carried out using receiver operating characteristic analysis. Conventional radiographs and digitized images were compared. The results indicate that, in such cases, diagnostic accuracy increases significantly as the pixel size is reduced, at least to the 0.1-mm level. We conclude that, for digital systems using screen-film or similar image receptors, use of a pixel size substantially larger than 0.1 mm may result in some loss of diagnostic accuracy.  相似文献   
104.
105.
Background: Spherophakia is an uncommon diagnosis. This is the first case report of spherophakia evaluated by ultrasound biomicroscopy.
Methods: Ultrasound biomicroscopy is a new diagnostic technique developed by one of the authors and provides images with microscopic resolution of the anterior segment. A patient with spherophakia was evaluated by ultrasound biomicroscopy (Zeiss-Humphrey, 50MHz) before and after YAG laser iridotomy.
Results: Ultrasound biomicroscopic assessment revealed a shallow anterior chamber, a very steep anterior lens curvature, iridolenticular contact, elongated zonules, and an increased distance between the lens equator and the ciliary processes. Angle closure glaucoma was due to a pupil block mechanism. The pupil block was relieved by YAG laser iridotomy.
Conclusions: Ultrasound biomicroscopy is a useful technique to confirm the diagnosis of spherophakia. The pupil block in spherophakia is relieved by YAG laser iridotomy.  相似文献   
106.
107.
108.
109.
中药升麻的化学成分   总被引:14,自引:0,他引:14  
李从军  陈迪华  肖培根 《药学学报》1993,28(10):777-781
从中药兴安升麻[Cimicifuga dahurica(Turcz.)Maxim.]的干燥根茎中分得五个化合物,其中四个为三萜木糖甙:升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅰ),25-O-乙酰升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅱ),12-羟基升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅲ),升麻醇-3-O-β-D-吡喃木糖基(3→1)-β-D-吡喃木糖甙(23R,24S)(Ⅳ),另一个为异阿魏酸(Ⅴ)。Ⅲ和Ⅳ为新化合物,通过光谱(IR,MS,1H及13C NMR)解析确定了它们的结构,分别命名为升麻甙A(cimiside A)和升麻甙B(cimiside B)。  相似文献   
110.
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