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   2965篇
  免费   307篇
  国内免费   7篇
耳鼻咽喉   10篇
儿科学   119篇
妇产科学   67篇
基础医学   395篇
口腔科学   22篇
临床医学   298篇
内科学   545篇
皮肤病学   24篇
神经病学   371篇
特种医学   63篇
外科学   343篇
综合类   98篇
一般理论   2篇
预防医学   405篇
眼科学   104篇
药学   229篇
中国医学   6篇
肿瘤学   178篇
  2022年   21篇
  2021年   54篇
  2020年   30篇
  2019年   45篇
  2018年   60篇
  2017年   35篇
  2016年   35篇
  2015年   44篇
  2014年   70篇
  2013年   103篇
  2012年   137篇
  2011年   155篇
  2010年   88篇
  2009年   78篇
  2008年   120篇
  2007年   132篇
  2006年   125篇
  2005年   123篇
  2004年   109篇
  2003年   123篇
  2002年   88篇
  2001年   111篇
  2000年   100篇
  1999年   94篇
  1998年   46篇
  1997年   40篇
  1996年   45篇
  1995年   45篇
  1994年   30篇
  1993年   33篇
  1992年   56篇
  1991年   58篇
  1990年   60篇
  1989年   63篇
  1988年   54篇
  1987年   40篇
  1986年   36篇
  1985年   60篇
  1984年   53篇
  1983年   37篇
  1982年   30篇
  1981年   32篇
  1980年   29篇
  1978年   25篇
  1977年   28篇
  1976年   23篇
  1975年   22篇
  1974年   27篇
  1971年   21篇
  1970年   21篇
排序方式: 共有3279条查询结果,搜索用时 15 毫秒
1.
2.
The presence of accessory channels between the liver and extrahepatic bile ducts has long been recognised by anatomists and the division of such ducts may be a cause of bile leakage following cholecystectomy. However, visualisation of accessory bile ducts at operation is difficult as they are often small and sometimes less than 1 mm in diameter. Cholangiography has been used to help in the identification of accessory ducts in 50 patients included in a prospective trial. X-rays were taken after dissection of the gall bladder from its bed and extravasation of contrast was seen on five occasions (10%) suggesting leakage from divided accessory ducts. The identification of damage to accessory bile ducts in 10% of patients suggests that this may occur more frequently than previously supposed.  相似文献   
3.
Abstract: Native chemical ligation has proven to be a powerful method for the synthesis of small proteins and the semisynthesis of larger ones. The essential synthetic intermediates, which are C‐terminal peptide thioesters, cannot survive the repetitive piperidine deprotection steps of Nα‐9‐fluorenylmethoxycarbonyl (Fmoc) chemistry. Therefore, peptide scientists who prefer to not use Nαt‐butyloxycarbonyl (Boc) chemistry need to adopt more esoteric strategies and tactics in order to integrate ligation approaches with Fmoc chemistry. In the present work, side‐chain and backbone anchoring strategies have been used to prepare the required suitably (partially) protected and/or activated peptide intermediates spanning the length of bovine pancreatic trypsin inhibitor (BPTI). Three separate strategies for managing the critical N‐terminal cysteine residue have been developed: (i) incorporation of Nα‐9‐fluorenylmethoxycarbonyl‐S‐(N‐methyl‐N‐phenylcarbamoyl)sulfenylcysteine [Fmoc‐Cys(Snm)‐OH], allowing creation of an otherwise fully protected resin‐bound intermediate with N‐terminal free Cys; (ii) incorporation of Nα‐9‐fluorenylmethoxycarbonyl‐S‐triphenylmethylcysteine [Fmoc‐Cys(Trt)‐OH], generating a stable Fmoc‐Cys(H)‐peptide upon acidolytic cleavage; and (iii) incorporation of Nαt‐butyloxycarbonyl‐S‐fluorenylmethylcysteine [Boc‐Cys(Fm)‐OH], generating a stable H‐Cys(Fm)‐peptide upon cleavage. In separate stages of these strategies, thioesters are established at the C‐termini by selective deprotection and coupling steps carried out while peptides remain bound to the supports. Pilot native chemical ligations were pursued directly on‐resin, as well as in solution after cleavage/purification.  相似文献   
4.
5.
Wasting protein-energy malnutrition (PEM) was induced in male C57BL/6J mice fed a low-protein diet ad libitum from 23 to 37 d of age. In comparison with a complete diet, the low-protein formulation reduced delayed hypersensitivity to sheep red blood cells (SRBCs) assessed on day 14 of feeding by measuring increased footpad thickness (mean +/- SD: 4 +/- 4% vs 22 +/- 8%, P less than 0.01), after immunization on day 9, and after challenge with SRBCs on day 13. By contrast, the low-protein diet did not affect the anti-SRBC hemagglutinin titer (8.3 +/- 2.2 vs 9.1 +/- 1.1, P greater than 0.30) despite profound reduction in numbers of splenic plasma cells secreting IgM-class anti-SRBCs (7.3 +/- 3.1 vs 49.9 +/- 23.8 x 10(-3), P less than 0.001), after immunization on day 9 and assessment on day 14. Thus, direct experimental evidence, previously altogether lacking, is provided in support of the concept, central to nutritional immunology, that acquired cell-mediated immunity is less resistant than is systemic humoral immunity to the depressive influence of pre-adolescent, wasting PEM.  相似文献   
6.
7.
8.
9.
Eighty patients who had undergone jejunoileal bypass for morbid obesity were examined by ultrasound at their routine follow-up visits to the clinic. Ultrasonographic evidence of intestinal intussusception was found in 15 patients (19%). Two of these patients were asymptomatic. Ultrasonographic findings were confirmed by operation in 6 patients (5 with intussusception, 1 negative).  相似文献   
10.
As the NHS adopts an information management approach to coordinated handling of total information resources, methods of systems analysis and design require assessment to ensure that they are appropriate. Mandatory use of Structured Systems Analysis and Design Methodology (SSADM) may be encouraging a damagingly narrow view of information systems. Research is described in which an holistic view of information systems is applied, allowing the needs of information users to play a stronger role in determining how information will be supplied to them. The techniques may also assist the training activities associated with implementing new systems.  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