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   13856篇
  免费   648篇
  国内免费   42篇
耳鼻咽喉   142篇
儿科学   960篇
妇产科学   439篇
基础医学   1396篇
口腔科学   246篇
临床医学   813篇
内科学   2760篇
皮肤病学   326篇
神经病学   705篇
特种医学   363篇
外科学   2676篇
综合类   361篇
一般理论   2篇
预防医学   558篇
眼科学   824篇
药学   900篇
  1篇
中国医学   56篇
肿瘤学   1018篇
  2023年   98篇
  2022年   253篇
  2021年   468篇
  2020年   230篇
  2019年   315篇
  2018年   414篇
  2017年   295篇
  2016年   393篇
  2015年   382篇
  2014年   565篇
  2013年   708篇
  2012年   1028篇
  2011年   1044篇
  2010年   603篇
  2009年   491篇
  2008年   803篇
  2007年   851篇
  2006年   792篇
  2005年   661篇
  2004年   586篇
  2003年   501篇
  2002年   410篇
  2001年   253篇
  2000年   249篇
  1999年   221篇
  1998年   110篇
  1997年   82篇
  1996年   62篇
  1995年   57篇
  1994年   47篇
  1993年   47篇
  1992年   98篇
  1991年   101篇
  1990年   83篇
  1989年   76篇
  1988年   74篇
  1987年   79篇
  1986年   81篇
  1985年   109篇
  1984年   56篇
  1983年   57篇
  1982年   41篇
  1979年   80篇
  1978年   45篇
  1977年   47篇
  1976年   39篇
  1975年   35篇
  1974年   42篇
  1973年   48篇
  1972年   46篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
The L4 filtration membrane was used at our laboratory on 30 semen specimens (19 from suspected subfertile patients and 11 from fertile donors) to assess changes in semen quality after routine sperm washing and swim up versus filtration through the L4 membrane. Of these 30 samples 17 (11 suspected subfertile patients and 6 fertile donors) were chosen to evaluate differences in sperm fertilizing ability between the 2 sperm preparation methods. Liquified specimens were analyzed on a Cell Soft semen analyzer. Semen specimens were divided equally, and 1 aliquot was processed by sperm washing and the swim up technique and the other by filtration. In all subjects the results of semen analysis and the hamster-egg penetration test showed significant improvement in sperm quality and fertilizing ability after filtration through the L4 membrane. Sperm motility was 58% after the swim up technique compared to 79% after filtration (p less than 0.0001) and velocity was 47 mu. per second after the swim up method compared to 52 mu. per second after filtration (p less than 0.048). Penetration rate and penetration index also showed a significant increase after filtration over values for the swim up method. Our results demonstrate that sperm filtration through the L4 membrane provides results superior to those of the traditional swim up technique. Due to significant savings in time associated with its use the L4 membrane can be used during sperm processing for intrauterine insemination and in vitro fertilization procedures.  相似文献   
32.
33.
34.
35.
36.
Fenfluramine, an amphetamine derivative used in the treatment of obesity, has been evaluated in vivo in the bone marrow cells of Swiss albino mice using two cytogenetic endpoints for assessing its genotoxic and clastogenic potentials. Concentrations of 0.75, 1.5, 3.0, and 5.0 mg/kg b.w. were administered orally for the study of sister chromatid exchange frequencies and chromosome aberrations (CA). SCE frequencies showed a positive dose response; 1.5 mg/kg being the minimum effective concentration. Fen caused a prolongation of cell cycle at all concentrations. Except for the minimum therapeutic dose (0.75 mg), all other doses (1.5, 3.0, and 5.0 mg) showed a significant increase in the percentage of damaged cells over that of the vehicle control. The degree of clastogenicity was directly proportional to the dosage used and inversely related with the duration of treatment. A gradual reduction of the clastogenic potential was observed after 12 and 24 hr of exposure, indicating that the maximum effect occurs at the middle or late synthetic phase of the cell cycle. This study, probably the first detailed screening of the drug for its genotoxicity, shows that Fen is moderately clastogenic and a DNA damaging agent in vivo.  相似文献   
37.
Recently, we and others showed that the components of green tea may be useful cancer chemopreventive agents. It has been suggested that (-)-epigallocatechin-3-gallate (EGCG), the major constituent in green tea, may possess antitumor-promoting and/or anticarcinogenic effects in rodent tumor bioassay systems. During the chemical analysis of various green tea products, we found a traditionally preserved preparation of green tea used by tribes in the Himalayan region of Sikkim, India that was rich in EGCG. EGCG was isolated from this tea product, and its inhibitory effects were evaluated against the binding of topically applied 3H-labeled polycyclic aromatic hydrocarbons (PAHs) to epidermal DNA and 12-O-tetradecanoylphorbol-13-acetate (TPA) caused induction of epidermal ornithine decarboxylase (ODC) activity in Sencar mice, the short-term markers of tumor initiation and tumor promotion, respectively. Preapplication of EGCG resulted in significant inhibition (p less than 0.05) in the binding of [3H]PAH to epidermal DNA. Similarly, the topical application of EGCG resulted in significant inhibition (p less than 0.005) in TPA-caused induction of epidermal ODC activity. In further studies, we assessed the anti-skin tumor-initiating effect of EGCG in Sencar mice in an initiation-promotion protocol. The application of EGCG before challenge with 7,12-dimethylbenz[a]anthracene as tumor initiator resulted in significant reduction both in percentage of mice with tumors and number of tumors per mouse compared with a non-EGCG-pretreated group of animals. The results of the present study suggest that the green tea preparation from Sikkim may be a good source for the isolation of EGCG and that this compound may have significant potential as a cancer chemopreventive agent.  相似文献   
38.
39.
Sturge-Weber syndrome is a rare neurocutaneous disorder characterized by a facial nevus flammeus and extensive angiomatous changes involving the leptomeninges, the dura, and vessels of the gray and white matter. Oculodermal melanocytosis is characterized by hyperpigmentation of the facial skin in the distribution of the ophthalmic, maxillary, and occasionally mandibular division of the trigeminal nerve.  相似文献   
40.
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