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   3429篇
  免费   221篇
  国内免费   230篇
  2023年   2篇
  2021年   10篇
  2020年   2篇
  2019年   14篇
  2018年   13篇
  2017年   11篇
  2016年   12篇
  2015年   11篇
  2014年   32篇
  2013年   27篇
  2012年   481篇
  2011年   455篇
  2010年   68篇
  2009年   40篇
  2008年   381篇
  2007年   376篇
  2006年   322篇
  2005年   332篇
  2004年   311篇
  2003年   209篇
  2002年   167篇
  2001年   160篇
  2000年   162篇
  1999年   83篇
  1998年   25篇
  1997年   17篇
  1996年   22篇
  1995年   16篇
  1994年   10篇
  1993年   17篇
  1992年   6篇
  1991年   3篇
  1989年   4篇
  1988年   3篇
  1987年   3篇
  1986年   3篇
  1982年   2篇
  1980年   2篇
  1959年   2篇
  1958年   4篇
  1957年   2篇
  1956年   7篇
  1955年   6篇
  1954年   10篇
  1953年   8篇
  1952年   5篇
  1951年   3篇
  1950年   4篇
  1949年   2篇
  1948年   3篇
排序方式: 共有3880条查询结果,搜索用时 143 毫秒
51.
小鼠基因组研究进展李善如1,2王冬平1陈永福2(1.军事医学科学院实验动物中心,北京100071)(2.中国农业大学生物学院,北京100094)TheDevelopmentofMouseGenomeResearchLIShanru1,2WANGDon...  相似文献   
52.
Li DD  Feng ZH  Zhang WQ  Hong JS 《生理学报》1998,50(4):385-391
一次皮下注射惊厥剂量(7.5mg/kg)的红藻氨酸(kainic acid,KA)诱发Fisher344大鼠出现急性癫痫发作,7d后即可形成癫痫敏感大鼠,继用Gel shift、Super-shift和Westem blot方法测定大鼠海马内AP-1 DNA结合活性及其组成成分。Gel shift结合显示,癫痫敏感大鼠海马内AP-1 DNA结合活性的基础水平较对照组为高;Super-shift实研  相似文献   
53.
本文根据系统学原理,提出了建立新类元的依据;并据此从分类和系统发育上论证了近金线属AnchicyclocheilusLietLan独立成属的可能性,认为应将近金线属归于金线属;修订了金线属SinocyclocheilusFang的鉴别特征。  相似文献   
54.
腐马素是由串珠镰刀菌产生的真菌毒素,其中腐马素B1可引发马脑白质软化症等疾病。本文用高效液相色谱法从串珠镰刀菌玉米培养物中分离出了腐马素B1并通过紫外光谱和快原子轰击质谱进行了鉴定。  相似文献   
55.
56.
57.
58.
59.
Alzheimer’s disease (AD), which is characterized by progressive cognitive impairment, is the most common neurodegenerative disease. Here, we investigated the preventive effect of a phosphodiesterase III inhibitor, cilostazol against cognitive decline in AD mouse model. In vitro studies using N2a cells stably expressing human amyloid precursor protein Swedish mutation (N2aSwe) showed that cilostazol decreased the amyloid β (Aβ) levels in the conditioned medium and cell lysates. Cilostazol attenuated the expression of ApoE, which is responsible for Aβ aggregation, in N2aSwe. Intracerebroventricular injection of Aβ25–35 in C57BL/6J mice resulted in increased immunoreactivity of Aβ and p-Tau, and microglia activation in the brain. Oral administration of cilostazol for 2 weeks before Aβ administration and once a day for 4 weeks post-surgery almost completely prevented the Aβ-induced increases of Aβ and p-Tau immunoreactivity, as well as CD11b immunoreactivity. However, post-treatment with cilostazol 4 weeks after Aβ administration, when Aβ was already accumulated, did not prevent the Aβ-induced neuropathological responses. Furthermore, cilostazol did not affect the neprilysin and insulin degrading enzymes involved in the degradation of the Aβ peptide, but decreased ApoE levels in Aβ-injected brain. In addition, cilostazol significantly improved spatial learning and memory in Aβ-injected mice. The findings suggest that a phosphodiesterase III inhibitor, cilostazol significantly decreased Aβ accumulation and improved memory impairment induced by Aβ25–35. The beneficial effects of cilostazol might be explained by the reduction of Aβ accumulation and tau phosphorylation, not through an increase in Aβ degradation but via a significant decrease in ApoE-mediated Aβ aggregation. Cilostazol may be the basis of a novel strategy for the therapy of AD.  相似文献   
60.
The cell surface heparan sulfate proteoglycan, syndecan-2, is crucial for the tumorigenic activity of colon cancer cells. However, the role played by the cytoplasmic domain of the protein remains unclear. Using colon cancer cells transfected with various syndecan-2-encoding genes with deletions in the cytoplasmic domain, it was shown that syndecan-2-induced migration activity requires the EFYA sequence of the C-terminal region; deletion of these residues abolished the rise in cell migration seen when the wild-type gene was transfected and syndecan-2 interaction with syntenin-1, suggesting that syntenin-1 functioned as a cytosolic signal effector downstream from syndecan-2. Colon cancer cells transfected with the syntenin-1 gene showed increased migratory activity, whereas migration was decreased in cells in which syntenin-1 was knock-down using small inhibitory RNA. In addition, syntenin-1 expression potentiated colon cancer cell migration induced by syndecan-2, and syndecan-2-mediated cell migration was reduced when syntenin-1 expression diminished. However, syntenin-1-mediated migration enhancement was not noted in colon cancer cells transfected with a gene encoding a syndecan-2 mutant lacking the cytoplasmic domain. Furthermore, in line with the increase in cell migration, syntenin-1 mediated Rac activation stimulated by syndecan-2. Together, the data suggest that the cytoplasmic domain of syndecan-2 regulates colon cancer cell migration via interaction with syntenin-1.  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