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   1336379篇
  免费   100279篇
  国内免费   4272篇
耳鼻咽喉   16802篇
儿科学   43618篇
妇产科学   36378篇
基础医学   197974篇
口腔科学   35923篇
临床医学   129743篇
内科学   258267篇
皮肤病学   26421篇
神经病学   112008篇
特种医学   48199篇
外国民族医学   366篇
外科学   184153篇
综合类   28793篇
现状与发展   1篇
一般理论   463篇
预防医学   114492篇
眼科学   28986篇
药学   98915篇
  6篇
中国医学   3167篇
肿瘤学   76255篇
  2021年   10964篇
  2019年   11681篇
  2018年   16360篇
  2017年   12317篇
  2016年   13272篇
  2015年   15232篇
  2014年   20831篇
  2013年   32109篇
  2012年   44289篇
  2011年   46944篇
  2010年   27091篇
  2009年   24945篇
  2008年   42770篇
  2007年   45095篇
  2006年   45214篇
  2005年   43624篇
  2004年   41599篇
  2003年   39538篇
  2002年   38343篇
  2001年   60866篇
  2000年   62547篇
  1999年   52293篇
  1998年   14586篇
  1997年   13288篇
  1996年   13120篇
  1995年   12464篇
  1994年   11630篇
  1993年   10923篇
  1992年   41585篇
  1991年   40774篇
  1990年   39473篇
  1989年   37363篇
  1988年   34596篇
  1987年   33707篇
  1986年   32165篇
  1985年   30664篇
  1984年   23050篇
  1983年   19600篇
  1982年   11756篇
  1979年   20809篇
  1978年   14821篇
  1977年   12073篇
  1976年   11877篇
  1975年   12117篇
  1974年   14807篇
  1973年   14479篇
  1972年   13363篇
  1971年   12427篇
  1970年   11488篇
  1969年   10418篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
The ability of 12 new thiazole derivatives to influence the muscle contractility mediated by purine P2X receptors has been studied in vitro using isolated tissues of rats and guinea pigs. Most of the synthesized compounds did not cause significant effects, but two compounds exhibited pronounced antagonism with respect to P2X-mediated contractility response. These compounds offer a good starting point for the synthesis of new effective antagonists of P2 receptors. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 6, pp. 22 – 25, June, 2005.  相似文献   
995.
BACKGROUND: Graft-vs.-host disease (GVHD) is the major cause of morbidity and mortality in patients undergoing allogeneic Bone Marrow Transplantation (BMT). The aim of our study was to identify the most relevant histological features for diagnosis of chronic Graft-vs.-Host Disease (cGVHD) in oral mucosa and minor salivary glands of 25 patients, as well as to evaluate the immunophenotype of the inflammatory cells. METHODS: Sixteen patients that were submitted to allogeneic BMT but did not present cGVHD were selected as a control group. The sections were studied on H & E and CD68, CD45, CD4, CD8, CD20 staining. RESULTS: The most frequent histologic findings in oral mucosa at the day of diagnosis of cGVHD were: hydropic degeneration of the basal layer of the epithelium, apoptotic bodies, lymphocytic infiltration, and focal or total cleavage between the epithelial and connective tissue. In the labial salivary glands (LSG), lymphocytic infiltration, acinar loss and fibrosis were the main alterations. Cytotoxic CD8-T cells and macrophages were predominant both in the epithelium and connective tissue, as well as in minor salivary glands. CONCLUSIONS: Histological features were useful in the diagnosis of oral cGVHD. It is suggested that CD8-T cells and macrophages play important role in the pathogenesis of the disease.  相似文献   
996.
This study evaluates the glycine potentiation of anticonvulsant drugs in subcutaneous pentylenetetrazol seizures in rats. Administered alone, glycine (30 or 40 mM/kg, PO) induced no anticonvulsant effect or neurological deficit. Coadministered with anticonvulsants, glycine significantly enhanced the anticonvulsant potency of diazepam and sodium valproate without affecting the neurological deficit induced by the anticonvulsants. Glycine did not significantly alter the anticonvulsant activity of ethosuximide or phenobarbital. These findings indicate a possible glycine-sensitive component in the mechanism of action of diazepam and sodium divalproate in subcutaneous pentylenetetrazol seizures. With the possible exception of sodium valproate, the present study provides little support for a glycine and gamma-aminobutyric acid (GABA) interaction as a mechanism of anticonvulsant activity in SC PTZ seizures. Further studies are required to determine the role of strychnine-sensitive and strychnine-insensitive glycine receptors in this experimental model of absence epilepsy.  相似文献   
997.
998.
999.
Human calcium absorption from whole-wheat products   总被引:1,自引:0,他引:1  
Fractional calcium absorption from wheat products and the influence of co-ingested wheat products on calcium absorption from milk were measured in a series of randomized crossover studies in healthy adult women. The wheat had been intrinsically labeled with 45Ca during growth. In the first study, fractional calcium absorption from leavened whole-wheat bread averaged 0.817 +/- 0.124. By comparison, absorption from milk, ingested at a comparable load in the same women, averaged only 0.589 +/- 0.111. When labeled bread was co-ingested with milk, at the same aggregate load as for bread alone, bread calcium absorption fell to 0.748 +/- 0.103 (P less than 0.05). In a second study, calcium absorption from an extruded cereal prepared from intrinsically labeled wheat bran was compared with milk. Calcium absorption from the cereal (0.223 +/- 0.046) was significantly less than from milk (0.375 +/- 0.072) (P less than 0.001). When the two were co-fed at the same total load, milk calcium absorption fell to 0.258 +/- 0.055 (P less than 0.001). In a third study, the effect of phytate hydrolysis through yeast fermentation and of Maillard browning on calcium absorption was investigated using leavened bread and underbaked and overbaked cookies, each made with intrinsically labeled wheat flour. Calcium absorption from cookies was not affected by the extent of browning and averaged 0.652 +/- 0.087. However, calcium absorption from bread in these same women averaged 0.703 +/- 0.108. This was significantly more than from the cookies (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
1000.
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