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   2096549篇
  免费   154164篇
  国内免费   5283篇
耳鼻咽喉   28103篇
儿科学   63046篇
妇产科学   55450篇
基础医学   304138篇
口腔科学   60433篇
临床医学   195364篇
内科学   405716篇
皮肤病学   42308篇
神经病学   169973篇
特种医学   78697篇
外国民族医学   432篇
外科学   311875篇
综合类   43787篇
现状与发展   2篇
一般理论   668篇
预防医学   163986篇
眼科学   46849篇
药学   158482篇
  9篇
中国医学   4933篇
肿瘤学   121745篇
  2019年   16110篇
  2018年   23016篇
  2017年   17543篇
  2016年   19214篇
  2015年   21935篇
  2014年   30025篇
  2013年   45854篇
  2012年   62857篇
  2011年   66351篇
  2010年   38861篇
  2009年   36240篇
  2008年   62306篇
  2007年   65563篇
  2006年   66415篇
  2005年   63973篇
  2004年   61351篇
  2003年   58577篇
  2002年   56983篇
  2001年   104469篇
  2000年   107883篇
  1999年   90245篇
  1998年   23432篇
  1997年   21042篇
  1996年   20881篇
  1995年   19670篇
  1994年   18326篇
  1993年   17067篇
  1992年   70495篇
  1991年   68438篇
  1990年   66283篇
  1989年   63732篇
  1988年   58696篇
  1987年   57158篇
  1986年   53997篇
  1985年   51655篇
  1984年   37992篇
  1983年   32259篇
  1982年   18200篇
  1979年   34227篇
  1978年   23683篇
  1977年   19783篇
  1976年   18495篇
  1975年   19519篇
  1974年   23815篇
  1973年   22889篇
  1972年   21434篇
  1971年   20183篇
  1970年   18924篇
  1969年   17492篇
  1968年   16356篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The in vitro ability of bacterial purified antigenic fractions to interfere with the immune system has been investigated on human mononuclear cells from peripheral blood. Exposure of purified monocytes to the drug at concentrations from 1 to 1000 micrograms/ml, for different periods from 0 to 18 h, significantly increased cell-mediated cytotoxicity against TU5 target cells. Moreover, monocytes exposed for 1 to 18 h to drug concentrations from 0.1 to 1000 micrograms/ml released significant amounts of tumor necrosis factor alpha in a dose-dependent manner in the culture supernatants. The drug was also tested on natural killer (NK) cell activity; mononuclear cells exposed to antigenic fractions for different periods showed a significant increase of NK cytotoxic activity against K562 target cells after 3 and 6, but not 0 and 18 h. Active concentrations were from 1 to 100 micrograms/ml, higher and lower doses being ineffective. Bacterial purified antigenic fractions thus have some ability to interfere in vitro with mechanisms of cytolysis mediated by cells and soluble factors.  相似文献   
992.
Four tricyclic antidepressants, amitriptyline, imipramine, desipramine and iprindole have been shown to partially protect mouse brain monoamine oxidase in-vivo from the irreversible enzyme inhibition produced by subsequent injection of phenelzine. Levels of protection were similar when the enzyme was assayed with selective substrates (5-hydroxytryptamine and phenethylamine) for both the A and B forms of the enzyme. Although other explanations cannot at this stage be ruled out, these observations are consistent with the tricyclic antidepressants acting as reversible inhibitors of brain monoamine oxidase in-vivo.  相似文献   
993.
994.
995.
Addison's disease is rarely caused by metastatic cancer. We report a unique case of hypoadrenalism owing to metastatic transitional cell carcinoma of the bladder. The relevant literature is reviewed.  相似文献   
996.
997.
We undertook a prospective study using arthroscopy to determine the intraarticular derangement caused by initial anterior shoulder dislocations. Of our 32 patients, 15 (47%) had a grade I, grade II, or grade III Hill-Sachs lesion. The patients were 29 men and 3 women whose ages ranged from 15 to 28 years (mean 22 years). All of the patients studied were United States military personnel or members of their families. None of the patients had had prior injuries of the affected shoulder, and all underwent arthroscopy within 72 h of injury. Few reports describe a Hill-Sachs lesion in a patient following a single anterior dislocation. Early reports of this lesion were based on indirect (radiographic) evidence. Our arthroscopic findings indicate that the incidence of this lesion after one anterior dislocation is higher than previously thought.  相似文献   
998.
The percentage uptake of [123I]metaiodobenzylguanidine (MIBG) by tumors of the paraganglion system is compared with the number of neurosecretory granules (assessed by both light and electron microscopy) in the subsequently resected tumors in six patients. Iodine-123 MIBG was injected intravenously; the tumor uptake of [123I]MIBG varied between 0.001% and 0.14% of the injected dose per gram of tumor tissue at 22 hr. The number of neurosecretory granules in tissue sections was scored on a scale of I-III. A direct proportional correlation was found between the percentage uptake of [123I]MIBG by the tumor and the number of neurosecretory granules in the tissue sections but not with plasma or urinary catecholamines. This technique for imaging reflects the storage status of the tumor better than plasma and urinary catecholamine measurements.  相似文献   
999.
Up to now two abnormal nephrographic patterns have been described as a result of arterial hypotension as an adverse response to urographic contrast material. We would like to describe a third pattern.  相似文献   
1000.
(E)-5-(2-Bromovinyl)-2'-deoxyuridine (1; BrVUdR) inhibits the replication of herpes simplex virus type 1 (HSV-1) and of varicella-zoster virus (VZV) in vitro at concentrations of 0.01 to 0.23 mumol/l, whereas herpes simplex virus type 2 (HSV-2) is influenced only at 5.5 to 27 mumol/l. In comparison to some classical and newly developed antiherpetics, i. e. 5-iodo-2'-desoxyuridine (2; idoxuridine, IDU), 9-beta-D-arabinofuranosyladenine (4; vidarabine Ara-A), 9-(2-hydroxyethoxymethyl) guanine (5; acyclovir, ACV) and 2'-fluoro-5-iodo-1-beta-D-aracytosine (6;FIAC) the following order of decreasing activity was found:1 greater than 6 greater than 5 greater than 2 greater than 4 (against HSV-1) and 6 greater than 2 greater than 5 greater than 1 greater than 4 (against HSV-2). The high selectivity of the antiviral effect of BrVUdR towards HSV-1 and TZV is based on the fact, that proliferation of different mammalian cell lines is inhibited by 50% only at concentrations as high as 90 to 170 mumol/l, resulting in a therapeutical index of 1000 to 10,000. Successful treatment of an HSV-1 encephalitis in mice as well as an HSV-1 keratitis of rabbits confirmed the efficiency of 1 in experimental animal infections. No toxic side effects in both local and systemic applications were observed. Promising data from cell culture and animal experiments recommend 1 as a potential candidate for the local and systemic treatment of HSV-1 and VZV infections in man.  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