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   2254篇
  免费   167篇
  国内免费   7篇
耳鼻咽喉   58篇
儿科学   80篇
妇产科学   20篇
基础医学   360篇
口腔科学   206篇
临床医学   183篇
内科学   321篇
皮肤病学   61篇
神经病学   127篇
特种医学   215篇
外科学   268篇
综合类   67篇
预防医学   152篇
眼科学   27篇
药学   156篇
中国医学   3篇
肿瘤学   124篇
  2022年   18篇
  2021年   24篇
  2020年   25篇
  2019年   30篇
  2018年   38篇
  2017年   35篇
  2016年   50篇
  2015年   48篇
  2014年   39篇
  2013年   71篇
  2012年   101篇
  2011年   94篇
  2010年   58篇
  2009年   56篇
  2008年   81篇
  2007年   75篇
  2006年   99篇
  2005年   89篇
  2004年   65篇
  2003年   68篇
  2002年   83篇
  2001年   68篇
  2000年   73篇
  1999年   62篇
  1998年   53篇
  1997年   46篇
  1996年   49篇
  1995年   39篇
  1994年   22篇
  1993年   23篇
  1992年   39篇
  1991年   48篇
  1990年   45篇
  1989年   49篇
  1988年   45篇
  1987年   52篇
  1986年   61篇
  1985年   47篇
  1984年   41篇
  1983年   30篇
  1982年   20篇
  1981年   16篇
  1980年   17篇
  1979年   25篇
  1978年   20篇
  1977年   16篇
  1976年   21篇
  1975年   19篇
  1973年   17篇
  1972年   16篇
排序方式: 共有2428条查询结果,搜索用时 15 毫秒
1.
2.
3.
Ganoderma sinensis has been used widely in Oriental countries for the prevention and treatment of various diseases including cancer. Previous studies have shown that the lipid extract from Ganoderma exhibits direct cytotoxicity against tumor cells. Here, it is reported that the lipid extract from germinating G. sinensis spores, at lower concentrations that have no direct tumoricidal activity, induce potent antitumor immune responses in human monocytes/macrophages. Upon stimulation with the lipid extract, monocytes/macrophages exhibited markedly increased production of proinflammatory cytokines and surface expression of costimulatory molecules. Conditioned medium from stimulated cells effectively suppressed the growth of tumor cells. Apparently, the lipid extract triggered macrophage activation via a mechanism different from that associated with LPS. Moreover, it was observed that the lipid extract could partially re‐establish the antitumor activity of the immunosuppressive tumor‐associated macrophages. These results indicated that in addition to its direct tumoricidal activity, the lipid extract from G. sinensis spores could exert antitumor activity by stimulating the activation of human monocytes/macrophages. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
4.
The purpose of this study is to show the spectrum of adjacent organ invasion and to make a brief review of hepatic alveolar hydatid disease (AHD), using CT and MR imaging. We retrospectively reviewed CT and MR images of three patients with various adjacent organ invasions surgically and histologically proven to be AHD. Local invasion to right kidney and adrenal, right hemidiaphragm and lung were detected in one patient, right adrenal in another patient and gall bladder, duodenum, gastric wall and pancreas invasion in the other. AHD may rarely extend to the gall bladder, stomach, duodenum, pancreas, right adrenal and kidney, diaphragm, pleura and lung. The extension of the disease outside the liver is usually encountered in patients with large, peripherally located masses in the advanced stage of the disease.  相似文献   
5.
6.
The effects of intracerebroventricularly (i.c.v.) administered gamma-glutamylcysteine (gamma-GC) and glutathione (GSH) monoethyl ester, subcutaneously (s.c.) injected L-2-oxo-4-thiazolidinecarboxylic acid (OTC) and intraperitoneally (i.p.) administered cysteine on the concentration of GSH in rat brain were investigated. The brain content of GSH, cysteine and gamma-GC was determined by HPLC with electrochemical detection (gold/mercury electrode) using N-acetylcysteine as internal standard. A dose-dependent increase in the GSH concentration (145-170% of controls) was found in the substantia nigra (SN) and in the rest of the brain stem after injection of gamma-GC, whereas no significant alterations in GSH were observed in the striatum and in the cerebral cortex. High levels of gamma-GC could be detected in the brain tissue after the administration, and the concentration of cysteine did also increase markedly after gamma-GC injection in all brain regions assessed. I.c.v. administration of L-buthionine sulfoximine (L-BSO) reduced the brain concentration of GSH by 50-70% within 24 hr. Injection of gamma-GC 24 hr after L-BSO resulted in an increase in GSH up to control values within 1-3 hr in the SN and the rest of the brain stem, whereas only a slight increase in GSH was observed in the striatum and the cerebral cortex. The concentration of GSH in the striatum and SN did not change after i.p. injection of cysteine, but a slight increase in the GSH concentration in the limbic region was observed. GSH monoethyl ester (i.c.v.) and OTC (s.c.) did not produce any significant increase in the GSH concentration in the brain. When the GSH concentration had been reduced by administration of L-BSO (i.c.v.; 24 hr) subsequent injection of GSH monoethyl ester led to a slight increase in the striatal and limbic GSH levels. These data show that, of the drugs studied, gamma-GC was the most effective in increasing brain GSH. It could thus serve as a valuable tool in future studies regarding metabolism and function of GSH in the brain. The observed difference in the effects of gamma-GC in different brain regions indicate that the brain tissue is not homogeneous with regard to GSH synthesizing capacity.  相似文献   
7.
A synthetic peptide corresponding to the second extracellular loop of the beta 1-adrenergic receptor was used as an antigen for antibody production in three rabbits. Antibodies of high titers were obtained in all rabbits. Only one rabbit yielded antibodies which decreased radioligand binding on the receptor in a similar way to that described for autoantibodies in patients with dilated cardiomyopathy. These antibodies recognized the receptor protein in immunoblots. Epitope mapping indicated that the N-terminal sequence of the loop used as antigen was the target of the major antigen fraction. Incubation of antibodies with C6 glioma cell membranes or inner membranes of E. coli, which express the human beta 1-adrenergic receptor, resulted in a decrease in number of radioligand binding sites. This decrease was dependent on the concentration of antibody and of Mg++ ions. It was not affected by the GTP analog GppNHp or the beta 1 subtype-specific antagonist metoprolol. The agonist, isoproterenol, also induced a decrease but the effects of antibody and agonist were not additive. These results suggest that the antibodies induce a Mg(++)-dependent, 'active', labile conformation of the receptor, independent from coupling to the GTP regulatory protein, but similar to that induced by the agonist isoproterenol. This interpretation was corroborated by the beta 1-adrenergic receptor agonist-like effect of the antibodies on cardiomyocytes in culture.  相似文献   
8.
Abstract Several statistical models that have been suggested in the periodontal literature for describing longitudinal attachment level changes, such as the gradual loss, single-burst, multiple-burst, and random walk models as well as other models introduced in this paper are compared by their power to predict future attachment loss. The data used in this analysis is from 1061 sites of 8 subjects, with moderate to severe periodontal disease, monitored monthly for about a year. This study found that none of the suggested models could significantly outperform the naive mean predictor, which predicts the future attachment level from the past mean. It was also found that no single model, such as the burst, gradual, or random walk, together with measurement error can fully explain the variation in the data. These results indicate that in the course of one year, the attachment level change may not follow the same model. Consequently, a model that fits well to past data cannot be accurately extended to the future.  相似文献   
9.
Using an in vitro system, the growth characteristics and enzyme histochemical properties of 3 odontogenic keratocysts and 3 dentigerous cysts were studied. It was found that the epithelial cells of the keratocysts hut not of the dentigerous cysts grew in vitro. Furthermore, the epithelial-like cells of the keratocysts showed the same activities of acid phosphatase and NADH-diaphorase in vitro as earlier described in vivo. These enzymatic activities were increased in epithelial-like cells close to proliferating fibroblast-like cells, indicating a close relationship between these two cell types. The results are discussed in the light of the known clinical behaviour of the keratocysts and certain conclusions are also drawn concerning the suggested neo plastic potential of the keratocysts.  相似文献   
10.
Deprivation of form vision by the fitting of translucent occluders suppressed the diurnal cycling of enkephalinergic amacrine cells (the ENSLI amacrine cells), in the chicken. Daily periods of normal vision or enforcing temporal contrast using strobe lighting appeared to restore normal functioning of the ENSLI cells. These results suggest that the ENSLI cells are involved in retinal circuits that assess the quality of the visual image and control eye growth.  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