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   1079篇
  免费   122篇
  国内免费   3篇
林业   99篇
农学   42篇
基础科学   12篇
  226篇
综合类   106篇
农作物   45篇
水产渔业   44篇
畜牧兽医   544篇
园艺   13篇
植物保护   73篇
  2023年   5篇
  2022年   7篇
  2021年   13篇
  2020年   17篇
  2019年   17篇
  2018年   29篇
  2017年   18篇
  2016年   26篇
  2015年   30篇
  2014年   44篇
  2013年   57篇
  2012年   59篇
  2011年   94篇
  2010年   50篇
  2009年   41篇
  2008年   73篇
  2007年   70篇
  2006年   69篇
  2005年   61篇
  2004年   64篇
  2003年   65篇
  2002年   66篇
  2001年   19篇
  2000年   19篇
  1999年   13篇
  1998年   11篇
  1997年   12篇
  1996年   3篇
  1995年   3篇
  1994年   7篇
  1993年   8篇
  1992年   12篇
  1991年   4篇
  1990年   6篇
  1989年   17篇
  1987年   5篇
  1986年   6篇
  1985年   6篇
  1984年   7篇
  1983年   3篇
  1982年   5篇
  1981年   3篇
  1980年   8篇
  1979年   4篇
  1977年   8篇
  1975年   3篇
  1974年   3篇
  1971年   5篇
  1970年   6篇
  1968年   4篇
排序方式: 共有1204条查询结果,搜索用时 15 毫秒
91.
Deformation on nearby faults induced by the 1999 Hector Mine earthquake   总被引:3,自引:0,他引:3  
Interferometric Synthetic Aperture Radar observations of surface deformation due to the 1999 Hector Mine earthquake reveal motion on several nearby faults of the eastern California shear zone. We document both vertical and horizontal displacements of several millimeters to several centimeters across kilometer-wide zones centered on pre-existing faults. Portions of some faults experienced retrograde (that is, opposite to their long-term geologic slip) motion during or shortly after the earthquake. The observed deformation likely represents elastic response of compliant fault zones to the permanent co-seismic stress changes. The induced fault displacements imply decreases in the effective shear modulus within the kilometer-wide fault zones, indicating that the latter are mechanically distinct from the ambient crustal rocks.  相似文献   
92.
The transmembrane protein LAT (linker for activation of T cells) couples the T cell receptor (TCR) to downstream signaling effectors. Mice homozygous for a mutation of a single LAT tyrosine residue showed impeded T cell development. However, later they accumulated polyclonal helper T (TH) cells that chronically produced type 2 cytokines in large amounts. This exaggerated TH2 differentiation caused tissue eosinophilia and massive maturation of plasma cells secreting to immunoglobulins of the E and G1 isotypes. This paradoxical phenotype establishes an unanticipated inhibitory function for LAT that is critical for the differentiation and homeostasis of TH cells.  相似文献   
93.
The hydrosilylation reaction enables the production of silicon polymers. Platinum-carbene complexes are reported that catalyze the hydrosilylation reaction of alkenes with remarkable efficiency and exquisite selectivity and avoid the formation of platinum colloids. By-products, typically encountered with previous catalytic systems, are suppressed with these platinum derivatives.  相似文献   
94.
95.
96.
97.
Challenges of modeling ocean basin ecosystems   总被引:1,自引:0,他引:1  
With increasing pressure for a more ecological approach to marine fisheries and environmental management, there is a growing need to understand and predict changes in marine ecosystems. Biogeochemical and physical oceanographic models are well developed, but extending these further up the food web to include zooplankton and fish is a major challenge. The difficulty arises because organisms at higher trophic levels are longer lived, with important variability in abundance and distribution at basin and decadal scales. Those organisms at higher trophic levels also have complex life histories compared to microbes, further complicating their coupling to lower trophic levels and the physical system. We discuss a strategy that builds on recent advances in modeling and observations and suggest a way forward that includes approaches to coupling across trophic levels and the inclusion of uncertainty.  相似文献   
98.
Regulation in vitro of metallothionein gene binding factors   总被引:19,自引:0,他引:19  
  相似文献   
99.
A physical map of the 1-gigabase bread wheat chromosome 3B   总被引:2,自引:0,他引:2  
As the staple food for 35% of the world's population, wheat is one of the most important crop species. To date, sequence-based tools to accelerate wheat improvement are lacking. As part of the international effort to sequence the 17-billion-base-pair hexaploid bread wheat genome (2n = 6x = 42 chromosomes), we constructed a bacterial artificial chromosome (BAC)-based integrated physical map of the largest chromosome, 3B, that alone is 995 megabases. A chromosome-specific BAC library was used to assemble 82% of the chromosome into 1036 contigs that were anchored with 1443 molecular markers, providing a major resource for genetic and genomic studies. This physical map establishes a template for the remaining wheat chromosomes and demonstrates the feasibility of constructing physical maps in large, complex, polyploid genomes with a chromosome-based approach.  相似文献   
100.
Small nuclear RNAs (snRNAs) are essential factors in messenger RNA splicing. By means of homozygosity mapping and deep sequencing, we show that a gene encoding U4atac snRNA, a component of the minor U12-dependent spliceosome, is mutated in individuals with microcephalic osteodysplastic primordial dwarfism type I (MOPD I), a severe developmental disorder characterized by extreme intrauterine growth retardation and multiple organ abnormalities. Functional assays showed that mutations (30G>A, 51G>A, 55G>A, and 111G>A) associated with MOPD I cause defective U12-dependent splicing. Endogenous U12-dependent but not U2-dependent introns were found to be poorly spliced in MOPD I patient fibroblast cells. The introduction of wild-type U4atac snRNA into MOPD I cells enhanced U12-dependent splicing. These results illustrate the critical role of minor intron splicing in human development.  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