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   18317篇
  免费   1001篇
  国内免费   99篇
耳鼻咽喉   130篇
儿科学   333篇
妇产科学   453篇
基础医学   3002篇
口腔科学   384篇
临床医学   1512篇
内科学   3265篇
皮肤病学   711篇
神经病学   1985篇
特种医学   1267篇
外科学   2319篇
综合类   80篇
一般理论   6篇
预防医学   738篇
眼科学   309篇
药学   1725篇
中国医学   24篇
肿瘤学   1174篇
  2023年   63篇
  2022年   131篇
  2021年   208篇
  2020年   192篇
  2019年   232篇
  2018年   250篇
  2017年   245篇
  2016年   322篇
  2015年   413篇
  2014年   494篇
  2013年   638篇
  2012年   971篇
  2011年   1126篇
  2010年   693篇
  2009年   700篇
  2008年   1136篇
  2007年   1205篇
  2006年   1166篇
  2005年   1150篇
  2004年   1140篇
  2003年   1184篇
  2002年   1152篇
  2001年   257篇
  2000年   180篇
  1999年   265篇
  1998年   308篇
  1997年   259篇
  1996年   231篇
  1995年   199篇
  1994年   181篇
  1993年   181篇
  1992年   131篇
  1991年   114篇
  1990年   107篇
  1989年   107篇
  1988年   123篇
  1987年   106篇
  1986年   79篇
  1985年   93篇
  1984年   102篇
  1983年   90篇
  1982年   96篇
  1981年   99篇
  1980年   105篇
  1979年   60篇
  1978年   59篇
  1977年   79篇
  1976年   62篇
  1975年   60篇
  1974年   72篇
排序方式: 共有10000条查询结果,搜索用时 30 毫秒
11.
A number of novel pyridazinomorphinans have been synthesized by the inverse electron demand Diels-Alder reaction of various 3,6-disubstituted 1,2,4,5-tetrazines with enamines derived from dihydrocodeinone and with codeinone. Reduction of some of the pyridazinomorphinans did not furnish the expected pyrroloepoxymorphinans; in all cases investigated reductive cleavage of the epoxybridge was observed to yield dihydropyridazino- or pyrrolomorphinans. The structures of all new compounds were assigned by the spectral data, that of the cycloadduct of codeinone was additionally verified by X-ray crystallography. Compounds 5a, 8, 11a , and 16 have been evaluated for their affinity at μ and κ opioid receptors in radioligand binding assays. Their ability to inhibit [3H]DAMGO binding at μ and [3H]U 69.593 binding at κ receptors, respectively as compared to codeine has been found to be lower.  相似文献   
12.
13.
Biliary obstruction and multiple hepatic abscesses occurred in a patient after ligation of a segmental branch of the right hepatic duct. The patient was successfully managed by transhepatic biliary drainage and balloon dilatation of an internal fistula that developed between the ligated duct and a Roux limb of jejunum. Internal biliary fistulas may be dilated using interventioanl radiologic techniques to permit nonobstructed bile flow. Implications for the nonsurgical treatment' of biliary strictures are discussed.  相似文献   
14.
Asymmetric Electrophilic α-Amidoalkylation, 4): Generation and Trapping Reactions of Chiral N- Acylpyrrolidiniumions The pyrrole derivatives 1 , 6 , and 10 react in the presence of TiCl4 with the silyl enol ether 3 to form α-substituted pyrrolidine amides steroselectively. 6 and 10 (after HCl-addition = > 11 ) react even at ?78°C, the reaction of 10 exceeds that of 6 in yield and stereoselectivity.  相似文献   
15.
16.
17.
18.
19.
The combined effects of the oligoamine RE 1492 with the NO-donor RE 2047 or ASA, ticlopidine, pentoxifylline and BM 14515 were determined in vitro (Born-test and in vivo (rat thrombosis model). The effects in vitro were supra additive but over independent. In vivo all combinations showed over additive and over independent inhibition of thrombus formation. The best results were obtained with a combination of 10 mg/kg RE 1492C and 10 mg/kg RE 2047. It inhibited thrombus formation in arterioles (A) by 79 % and 36 % in venoles (V). The combined effect of RE 1492C and pentoxifylline 10 mg/kg each was 62% (A) or 32% (V), respectively.  相似文献   
20.
BACKGROUND: Basal cell carcinoma shows a wide spectrum of clinical and histologic appearances. A distinct tumor variant with follicular infundibulocystic differentiation is recognized, and there are only a few reports on its clinical presentation and management. OBJECTIVE: To report a case of multiple infundibulocystic basal cell carcinomas with a unique unilateral presentation. METHODS: A clinical history was obtained. Photographs were taken, and punch biopsies were performed. RESULTS: An 83-year-old Caucasian female presented with multiple unilateral, asymptomatic, skin-colored, dome-shaped papules around the right mouth for 11 years without apparent change. Punch biopsies revealed findings typical of infundibulocystic basal cell carcinoma. CONCLUSIONS: A patient with clinically indolent multiple unilateral infundibulocystic basal cell carcinomas is described. Given the location of these multiple lesions, standard treatment modalities for basal cell carcinomas would have significant cosmetic and functional implications. A management approach with clinical follow-up and surgical intervention only for changing lesions is discussed.  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