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   4763篇
  免费   372篇
  国内免费   1篇
  5136篇
  2023年   25篇
  2022年   64篇
  2021年   119篇
  2020年   51篇
  2019年   73篇
  2018年   96篇
  2017年   85篇
  2016年   147篇
  2015年   260篇
  2014年   243篇
  2013年   329篇
  2012年   417篇
  2011年   395篇
  2010年   248篇
  2009年   194篇
  2008年   306篇
  2007年   299篇
  2006年   263篇
  2005年   258篇
  2004年   243篇
  2003年   219篇
  2002年   237篇
  2001年   44篇
  2000年   35篇
  1999年   47篇
  1998年   52篇
  1997年   45篇
  1996年   19篇
  1995年   35篇
  1994年   31篇
  1993年   34篇
  1992年   25篇
  1991年   14篇
  1990年   16篇
  1989年   18篇
  1988年   10篇
  1987年   6篇
  1986年   8篇
  1985年   15篇
  1984年   10篇
  1983年   7篇
  1982年   17篇
  1981年   10篇
  1980年   7篇
  1979年   6篇
  1978年   5篇
  1976年   10篇
  1973年   4篇
  1972年   4篇
  1969年   5篇
排序方式: 共有5136条查询结果,搜索用时 8 毫秒
61.
The UBAP1 subunit of ESCRT-I interacts with ubiquitin via a SOUBA domain   总被引:1,自引:0,他引:1  
Highlights? ESCRT-I subunit UBAP1 is essential for degradation of antiviral protein tetherin ? UBAP1 has a domain consisting of a solenoid of overlapping UBAs (SOUBA) ? Each of the three UBAs in the SOUBA binds monoubiquitin  相似文献   
62.
We investigated the molecular relationships between lipid peroxidation and mitochondrial DNA (mtDNA) single strand breaks (ssb) in isolated rat hepatocytes and mitochondria exposed to tert-butylhydroperoxide (TBH). Our results show that mtDNA ssb induced by TBH are independent of lipid peroxidation and dependent on the presence of iron and of hydroxyl free radicals. These data contribute to the definition of the mechanisms whereby mtDNA ssb are induced and provide possible molecular targets for the prevention of this kind of damage in vivo.  相似文献   
63.
Protons at the gate: DEG/ENaC ion channels help us feel and remember   总被引:13,自引:0,他引:13  
Bianchi L  Driscoll M 《Neuron》2002,34(3):337-340
The DEG/ENaC ion channel family contributes to channels of striking functional diversity. Neuronally expressed family members include the C. elegans degenerins that mediate touch and are thought to be mechanically gated, and the mammalian ASICs, which are gated by protons. ASICs affect a range of sensory functions that includes perception of gentle touch, harsh touch, heat, sour taste, and pain. Family member ASIC1 is now implicated in long-term potentiation, suggesting that minute fluxes in synaptic pH may activate ASICs to enhance learning.  相似文献   
64.
65.
We investigated the neuropharmacological effects of the methanolic extract from Lactuca capensis Thunb. leaves (100 and 200 mg/kg) for 21 days on memory impairment in an Alzheimer's disease (AD) rat model produced by direct intraventricular delivery of amyloid‐β1‐42 (Aβ1‐42). Behavioural assays such as Y‐maze and radial arm maze test were used for assessing memory performance. Aβ1‐42 decreased cognitive performance in the behavioural tests which were ameliorated by pre‐treatment with the methanolic extract. Acetylcholinesterase activity and oxidant–antioxidant balance in the rat hippocampus were abnormally altered by Aβ1‐42 treatment while these deficits were recovered by pre‐treatment with the methanolic extract. In addition, rats were given Aβ1‐42 exhibited in the hippocampus decreased brain‐derived neurotrophic factor (BDNF) mRNA copy number and increased IL‐1β mRNA copy number which was reversed by the methanolic extract administration. These findings suggest that the methanolic extract could be a potent neuropharmacological agent against dementia via modulating cholinergic activity, increasing of BDNF levels and promoting antioxidant action in the rat hippocampus.  相似文献   
66.
67.
68.
Ascorbic acid immediately dissolves Euphausia superba chitosan upon mixing and forms chitosan ascorbate; during the 6-h period after dissolution in water at pH 5–7, ascorbate is oxidized to dehydroascorbate which undergoes Schiff reaction with the amino groups of chitosan, thus yielding a viscous solution of a polymeric ketimine. The latter is characterized by infrared spectrometry, circular dichroism spectropolarimetry, viscometry and alkalimetry. When brought into contact with transition metal ions, the chitosan ascorbate ketimine yields insoluble metal chelates. Upon reduction with sodium cyanoborohydride, the water-insoluble N-[2-(1,2-dihydroxyethyl)tetrahydrofuryl] chitosan (NDTC) is obtained, which shows enhanced capacity for uranium, up to 800 mg U/g from solutions at pH 4·5.  相似文献   
69.
Sleep and Biological Rhythms - The aim of the present work was to validate the reduced version of the Morningness-Eveningness Questionnaire (MEQr) using circadian motor activity as external...  相似文献   
70.
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