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   1271篇
  免费   58篇
  国内免费   1篇
林业   81篇
农学   14篇
基础科学   5篇
  143篇
综合类   383篇
农作物   38篇
水产渔业   78篇
畜牧兽医   475篇
园艺   37篇
植物保护   76篇
  2023年   11篇
  2022年   7篇
  2021年   35篇
  2020年   31篇
  2019年   36篇
  2018年   26篇
  2017年   31篇
  2016年   25篇
  2015年   25篇
  2014年   26篇
  2013年   37篇
  2012年   76篇
  2011年   82篇
  2010年   46篇
  2009年   37篇
  2008年   81篇
  2007年   78篇
  2006年   91篇
  2005年   81篇
  2004年   62篇
  2003年   52篇
  2002年   54篇
  2001年   17篇
  2000年   12篇
  1999年   11篇
  1998年   14篇
  1997年   9篇
  1995年   5篇
  1993年   6篇
  1992年   9篇
  1991年   4篇
  1990年   12篇
  1989年   13篇
  1988年   6篇
  1987年   7篇
  1986年   6篇
  1985年   7篇
  1984年   9篇
  1983年   8篇
  1981年   4篇
  1980年   8篇
  1979年   12篇
  1978年   8篇
  1976年   4篇
  1975年   9篇
  1974年   10篇
  1973年   12篇
  1971年   6篇
  1967年   7篇
  1966年   6篇
排序方式: 共有1330条查询结果,搜索用时 31 毫秒
71.
72.
73.
74.
75.
Major epidemic outbreaks of viral hepatitis in underdeveloped countries result from a type of non-A, non-B hepatitis distinct from the parenterally transmitted form. The viral agent responsible for this form of epidemic, or enterically transmitted non-A, non-B hepatitis (ET-NANBH), has been serially transmitted in cynomolgus macaques (cynos) and has resulted in typical elevation in liver enzymes and the detection of characteristic virus-like particles (VLPs) in both feces and bile. Infectious bile was used for the construction of recombinant complementary DNA libraries. One clone, ET1.1, was exogenous to uninfected human and cyno genomic liver DNA, as well as to genomic DNA from infected cyno liver. ET1.1 did however, hybridize to an approximately 7.6-kilobase RNA species present only in infected cyno liver. The translated nucleic acid sequence of a portion of ET1.1 had a consensus amino acid motif consistent with an RNA-directed RNA polymerase; this enzyme is present in all positive strand RNA viruses. Furthermore, ET1.1 specifically identified similar sequences in complementary DNA prepared from infected human fecal samples collected from five geographically distinct ET-NANBH outbreaks. Therefore, ET1.1 represents a portion of the genome of the principal viral agent, to be named hepatitis E virus, which is responsible for epidemic outbreaks of ET-NANBH.  相似文献   
76.
Further results from the Venus orbiter radiometric temperature experiment (VORTEX) on the Pioneer orbiter are presented. These are used to characterize the three-dimensional temperature field, the cloud structure, and the dynamics of the 60-to 130-kilometer altitude region of the Venus atmosphere. One of the new discoveries is a "dipole" structure at high latitudes, with two hot spots rotating around the pole, surrounded by banks of cold cloud.  相似文献   
77.
Quantitative analysis of culture using millions of digitized books   总被引:1,自引:0,他引:1  
We constructed a corpus of digitized texts containing about 4% of all books ever printed. Analysis of this corpus enables us to investigate cultural trends quantitatively. We survey the vast terrain of 'culturomics,' focusing on linguistic and cultural phenomena that were reflected in the English language between 1800 and 2000. We show how this approach can provide insights about fields as diverse as lexicography, the evolution of grammar, collective memory, the adoption of technology, the pursuit of fame, censorship, and historical epidemiology. Culturomics extends the boundaries of rigorous quantitative inquiry to a wide array of new phenomena spanning the social sciences and the humanities.  相似文献   
78.
The sirtuins are members of the histone deacetylase family of proteins that participate in a variety of cellular functions and play a role in aging. We identified a potent inhibitor of sirtuin 2 (SIRT2) and found that inhibition of SIRT2 rescued alpha-synuclein toxicity and modified inclusion morphology in a cellular model of Parkinson's disease. Genetic inhibition of SIRT2 via small interfering RNA similarly rescued alpha-synuclein toxicity. Furthermore, the inhibitors protected against dopaminergic cell death both in vitro and in a Drosophila model of Parkinson's disease. The results suggest a link between neurodegeneration and aging.  相似文献   
79.
Reversal of neurological defects in a mouse model of Rett syndrome   总被引:2,自引:0,他引:2  
Guy J  Gan J  Selfridge J  Cobb S  Bird A 《Science (New York, N.Y.)》2007,315(5815):1143-1147
Rett syndrome is an autism spectrum disorder caused by mosaic expression of mutant copies of the X-linked MECP2 gene in neurons. However, neurons do not die, which suggests that this is not a neurodegenerative disorder. An important question for future therapeutic approaches to this and related disorders concerns phenotypic reversibility. Can viable but defective neurons be repaired, or is the damage done during development without normal MeCP2 irrevocable? Using a mouse model, we demonstrate robust phenotypic reversal, as activation of MeCP2 expression leads to striking loss of advanced neurological symptoms in both immature and mature adult animals.  相似文献   
80.
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