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   100247篇
  免费   6222篇
  国内免费   769篇
耳鼻咽喉   1139篇
儿科学   3016篇
妇产科学   2507篇
基础医学   13581篇
口腔科学   2284篇
临床医学   8176篇
内科学   22073篇
皮肤病学   2159篇
神经病学   9488篇
特种医学   3772篇
外国民族医学   23篇
外科学   13738篇
综合类   1657篇
一般理论   49篇
预防医学   5896篇
眼科学   1565篇
药学   8057篇
  3篇
中国医学   526篇
肿瘤学   7529篇
  2023年   494篇
  2022年   1120篇
  2021年   2026篇
  2020年   1312篇
  2019年   1810篇
  2018年   2225篇
  2017年   1698篇
  2016年   1807篇
  2015年   2111篇
  2014年   2747篇
  2013年   4005篇
  2012年   5391篇
  2011年   5581篇
  2010年   3575篇
  2009年   3118篇
  2008年   4822篇
  2007年   4965篇
  2006年   4707篇
  2005年   4453篇
  2004年   4745篇
  2003年   4548篇
  2002年   4553篇
  2001年   3721篇
  2000年   3658篇
  1999年   2963篇
  1998年   1142篇
  1997年   895篇
  1996年   822篇
  1995年   794篇
  1994年   683篇
  1993年   667篇
  1992年   1777篇
  1991年   1751篇
  1990年   1487篇
  1989年   1435篇
  1988年   1317篇
  1987年   1178篇
  1986年   1169篇
  1985年   1035篇
  1984年   761篇
  1983年   693篇
  1982年   444篇
  1981年   383篇
  1979年   564篇
  1978年   416篇
  1975年   427篇
  1974年   480篇
  1973年   463篇
  1972年   422篇
  1971年   392篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Chronic obstructive pulmonary disease (COPD) is characterised by a local pulmonary inflammatory response to respiratory pollutants and by systemic inflammation. Tumour necrosis factor (TNF)-alpha has been implicated in systemic effects of COPD and operates by binding the p55 (R1) and p75 (R2) TNF-alpha receptors. To investigate the contribution of each TNF-alpha receptor in the pathogenesis of COPD, the present study examined the effects of chronic air or cigarette smoke (CS) exposure in TNF-alpha R1 knockout (KO) mice, TNF-alpha R2 KO mice and wild type (WT) mice. CS was found to significantly increase the protein levels of soluble TNF-alpha R1 (by four-fold) and TNF-alpha R2 (by 10-fold) in the bronchoalveolar lavage of WT mice. After 3 months, CS induced a prominent pulmonary inflammatory cell influx in WT and TNF-alpha R1 KO mice. In TNF-alpha R2 KO mice, CS-induced pulmonary inflammation was clearly attenuated. After 6 months, no emphysema was observed in CS-exposed TNF-alpha R2 KO mice in contrast to WT and TNF-alpha R1 KO mice. CS-exposed WT and TNF-alpha R1 KO mice failed to gain weight, whereas the body mass of TNF-alpha R2 KO mice was not affected. These current findings suggest that both tumour necrosis factor-alpha receptors contribute to the pathogenesis of chronic obstructive pulmonary disease, but tumour necrosis factor-alpha receptor-2 is the most active receptor in the development of inflammation, emphysema and systemic weight loss in this murine model of chronic obstructive pulmonary disease.  相似文献   
4.
5.
Cyanoacrylate-based glues have been reported as producing dermatitis and bronchial asthma. The paper describes the case of a patient occupationally exposed to Loctite 406, who developed irritation of the skin and mucosae of the face and late bronchial asthma. Preventive measures for subjects exposed to cyanoacrylic instant glues are discussed.  相似文献   
6.
The response of single detergent treated bovine retinal pigment epithelial cells in culture to ATP was measured with an image analyser. The most pronounced contraction was produced by 1.0 mM ATP with most change taking place in the first 10 min. At 1 h the area had decreased by about 33%, perimeter 22% and maximum length 25%. By way of comparison rabbit skin fibroblasts had a decreased area of approximately 40%, perimeter 25% and maximum length 22%. Bovine aortic smooth muscle cells on the other hand decreased in area by 55%, perimeter 40% and maximum length 36%. It is hoped that this assay may be used to evaluate drugs which could counteract contractile events in proliferative vitreoretinopathy.  相似文献   
7.
Rat brain hippocampal slices were incubated with or without the convulsant 4-aminopyridine (4-AP). From these slices a crude mitochondrial/synaptosomal membrane fraction was prepared and analyzed for endogenous protein phosphorylation. 4-AP (10(-5) M) stimulated the phosphorylation of a 50 kDa protein by 86%. The phosphorylation of this 50 kDa protein is Ca2+/calmodulin-dependent and we suggest that this protein is the lower molecular weight subunit of Ca2+/calmodulin-dependent protein kinase II (CaMK II).  相似文献   
8.
Female rats consistently show a pattern of differences in defensive behaviors compared to males which parallel the effects of exposure to a nonpainful threat stimulus (cat or cat odor) in the same tests and measures. These indications of greater defensiveness for females are particularly common in situations involving potential, as opposed to actual and present, threat, a factor which probably also reflects ceiling or floor effects in situations involving very intense defensiveness. In addition, pharmacological studies indicate sex differences in the effects of selective serotonin (5-HT) receptor agonists and antagonists on defensive responding. These findings indicate that sex effects must be considered in studies of the pharmacological control of defensive behaviors, and suggest that responsivity to sex effects may be an additional criterion for the suitability of animal models of anxiety.  相似文献   
9.
Is interleukin 2 a neuromodulator in the brain?   总被引:5,自引:0,他引:5  
A bidirectional flow of information exists between the CNS and the neuroendocrine and immune systems, representing an important homeostatic mechanism in the body. Lymphokines and other products of immunocompetent cells seem to play a crucial role in this communication and seem to exert powerful effects on neurones in the brain. In this article, Giuseppe Nisticò and Giovambattista De Sarro describe the central effects following interleukin 2 (IL-2) microinfusion into several areas of the rat brain. The locus coeruleus seems to be the main site in the brain through which IL-2 exerts soporific effects. In addition, the possible transducing mechanisms coupling IL-2 receptor stimulation and the electroencephalogram (EEG) spectrum power responses elicited from the locus coeruleus seem to involve stimulation of specific receptors coupled to adenylate cyclase through a Gi protein.  相似文献   
10.
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