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   1814篇
  免费   116篇
  国内免费   17篇
耳鼻咽喉   11篇
儿科学   45篇
妇产科学   51篇
基础医学   369篇
口腔科学   35篇
临床医学   107篇
内科学   344篇
皮肤病学   43篇
神经病学   108篇
特种医学   51篇
外科学   348篇
综合类   23篇
预防医学   142篇
眼科学   27篇
药学   95篇
中国医学   5篇
肿瘤学   143篇
  2023年   10篇
  2022年   12篇
  2021年   23篇
  2020年   22篇
  2019年   44篇
  2018年   44篇
  2017年   27篇
  2016年   35篇
  2015年   41篇
  2014年   57篇
  2013年   66篇
  2012年   114篇
  2011年   107篇
  2010年   77篇
  2009年   59篇
  2008年   83篇
  2007年   81篇
  2006年   75篇
  2005年   91篇
  2004年   85篇
  2003年   79篇
  2002年   74篇
  2001年   71篇
  2000年   41篇
  1999年   45篇
  1998年   15篇
  1997年   12篇
  1996年   9篇
  1995年   8篇
  1994年   9篇
  1992年   25篇
  1991年   33篇
  1990年   28篇
  1989年   28篇
  1988年   31篇
  1987年   33篇
  1986年   25篇
  1985年   16篇
  1984年   23篇
  1983年   19篇
  1979年   16篇
  1978年   22篇
  1977年   10篇
  1976年   8篇
  1975年   8篇
  1974年   12篇
  1972年   10篇
  1971年   12篇
  1969年   8篇
  1968年   13篇
排序方式: 共有1947条查询结果,搜索用时 15 毫秒
11.
The lifespan of antigen-bearing dendritic cells (DCs) is determined by signals from pathogens and T cells. These signals regulate DC survival by modulating expression of Bcl-2 family proteins. Toll-like receptors and T cell costimulatory molecules both trigger a DC survival pathway that is dependent on Bcl-x(L). However, Toll-like receptors uniquely increase expression of Bim and trigger cell death by a pathway that is blocked by Bcl-2. This pathway serves as a molecular 'timer' that sets the lifespan of DCs and regulates the magnitude of T cell responses in vivo. Thus, signals derived from the innate and acquired immune systems control DC lifespan and immunogenicity by distinct molecular mechanisms.  相似文献   
12.
13.
14.
A newly isolated lectin, Amaranthus caudatus agglutinin (also called amaranthin or ACA), which binds to the Thomsen-Friedenreich antigen (T-antigen) and its sialylated variants, was used as a histochemical probe for proliferating cells in sections of human colonic tissues. Binding inhibition studies revealed that ACA binds to different sites on histological sections when compared to peanut agglutinin, which also recognizes the T-antigen. ACA bound selectively to the cells at the base of the colonic crypt [46 +/- 4% (SEM) of glands] which is the zone of proliferation in this tissue and preferentially labeled cytoplasmic and apical membrane glycoconjugates. Only 7 +/- 2% of the upper portions of the colonic crypts were labeled (P less than 0.001 compared to the base), and this was largely a result of extensive labeling in 2 of 23 samples studies. A marked increase in histochemical labeling by ACA was seen in adenomatous polyps and adenocarcinomas of the colon, in which 82 +/- 7 and 97 +/- 2% of the glandular units were labeled, respectively. Transitional mucosa and connective tissue adjacent to cancers were also labeled by ACA. Neuraminidase studies indicated that removal of sialic acid residues enhanced binding by peanut agglutinin, but not ACA, to glycoconjugates in cancer specimens. Specimens of colonic tissue from patients with familial adenomatous polyposis (FAP) were examined with ACA; 83 +/- 7% of adenomatous glands and 60 +/- 7% of glands in flat, normal-appearing tissue were labeled. Colonic tissues from persons at 50% risk for hereditary nonpolyposis colorectal cancer (HNPCC), FAP, and normal colons were studied and given "weighted average" labelling scores that ranged from 0-400 to accommodate variable intensity and distribution of labeling. Normal colons had a weighted average score of 65 +/- 33; FAP tissues had a score of 224 +/- 76 (P less than 0.001 compared to normal colon) and HNPCC tissues had a score of 74 +/- 70 (P less than 0.05 compared to normal colon). A group of five HNPCC cases had scores of 203 +/- 43 (P less than 0.001 compared to normal colon). ACA labels glycoconjugates in the proliferative region of normal human colonic epithelium and neoplastic lesions of the colon. The results of FAP and HNPCC tissues suggest that it may be useful for identifying foci of abnormal proliferation in familial colorectal cancer syndromes.  相似文献   
15.
16.
17.
Cardiac transplantation is indicated for patients with end-stage cardiomyopathy secondary to cardiac sarcoidosis. Although rare, recurrent disease has been reported in two cases. The current report presents a case of recurrent cardiac sarcoidosis in a patient 45 months postorthotopic heart transplantation and 40 months following reactivation of latent Mycobacterium tuberculosis infection. The patient was the first to have recurrent disease following an infection that has been proposed to be involved in its pathogenesis. The patient’s interval between transplant and recurrence is the longest reported to date.  相似文献   
18.
Digestive Diseases and Sciences - Patients with SARS-CoV-2 who present with gastrointestinal symptoms have a milder clinical course than those who do not. Risk factors for severe COVID-19 disease...  相似文献   
19.
Summary Parallel studies were performed using microfluorimetric DNA determination and X-ray microanalysis on the same thyroid biopsy material to compare the intranuclear DNA and monovalent electrolyte contents (Na+, K+, Cl). Samples were taken from apparently healthy, adenomatous, and cancerous parts of human thyroid glands removed surgically. The time interval was less than 1 min. The tissues were classified by the pathologist into four main classes: 1) Normal thyroid tissue; 2) benign adenomas; 3) differentiated (follicular and papillary) carcinomas; and 4) anaplastic cancers. The results revealed that the level of aneuploidization showed an increase parallel with the malignancy of the studied tumor. At the same time, a similar tendency was found in the average values of the intranuclear Na+:K+ ratios. The results obtained in this way confirm the possibility that the electric properties of the cell membrane, that is the sustained membrane depolarization, may have a role in the regulation of DNA synthesis and in mitogenesis. These results may offer new diagnostic and/or therapeutic possibilities.  相似文献   
20.
Journal of Autism and Developmental Disorders - The original version of this article unfortunately contained a mistake in Table 6. The column headings was repeated in the first column along with...  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