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   171篇
  免费   6篇
林业   9篇
农学   4篇
  24篇
综合类   25篇
农作物   8篇
水产渔业   10篇
畜牧兽医   87篇
园艺   1篇
植物保护   9篇
  2023年   2篇
  2022年   1篇
  2021年   5篇
  2020年   5篇
  2019年   7篇
  2018年   2篇
  2017年   8篇
  2016年   3篇
  2015年   1篇
  2014年   6篇
  2013年   13篇
  2012年   14篇
  2011年   13篇
  2010年   10篇
  2009年   6篇
  2008年   4篇
  2007年   11篇
  2006年   10篇
  2005年   7篇
  2004年   8篇
  2003年   9篇
  2002年   4篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1996年   4篇
  1994年   2篇
  1993年   1篇
  1992年   4篇
  1991年   1篇
  1981年   1篇
  1978年   2篇
  1977年   2篇
  1971年   1篇
  1969年   1篇
  1967年   2篇
  1959年   1篇
  1957年   1篇
排序方式: 共有177条查询结果,搜索用时 15 毫秒
101.
102.
Ubiquitin-positive, tau- and alpha-synuclein-negative inclusions are hallmarks of frontotemporal lobar degeneration with ubiquitin-positive inclusions and amyotrophic lateral sclerosis. Although the identity of the ubiquitinated protein specific to either disorder was unknown, we showed that TDP-43 is the major disease protein in both disorders. Pathologic TDP-43 was hyper-phosphorylated, ubiquitinated, and cleaved to generate C-terminal fragments and was recovered only from affected central nervous system regions, including hippocampus, neocortex, and spinal cord. TDP-43 represents the common pathologic substrate linking these neurodegenerative disorders.  相似文献   
103.
In this article, advances in the application of medical media to education, clinical care, and research are explored and illustrated with examples, and their future potential is discussed. Impact is framed in terms of the Sloan Consortium's five pillars of quality education: access; student and faculty satisfaction; learning effectiveness; and cost effectiveness. (Hiltz SR, Zhang Y, Turoff M. Studies of effectiveness of learning networks. In Bourne J, Moore J, ed. Elements of Quality Online Education. Needham, MA: Sloan-Consortium, 2002:15-45). The alternatives for converting analog media (text, photos, graphics, sound, video, animations, radiographs) to digital media and direct digital capture are covered, as are options for storing, manipulating, retrieving, and sharing digital collections. Diagnostic imaging is given particular attention, clarifying the difference between computerized radiography and digital radiography and explaining the accepted standard (DICOM) and the advantages of Web PACS. Some novel research applications of medical media are presented.  相似文献   
104.
105.
This report describes 2 cases of spontaneous aortic dissecting hematoma in young Border Collie and Border Collie crossbred dogs. Histology was performed in one of the cases involving an unusual splitting of the elastin present within the wall of the aorta, consistent with elastin dysplasia as described in Marfan syndrome in humans. The first case involved a young purebred Border Collie that died suddenly and the second case involved a Border Collie crossbred dog that died after a 1-month history of seizures. Gross lesions included pericardial tamponade with dissection of the ascending aorta in the former case and thoracic cavity hemorrhage, mediastinal hematoma, and aortic dissection in the latter. Histologic lesions in the case of the Border Collie crossbred dog included a dissecting hematoma of the ascending aorta with elastin dysplasia and right axillary arterial intimal proliferation.  相似文献   
106.
The reproductive periodicities of the patellid limpets Cellana capensis and Patella concolor were determined from changes in macro-and microscopic appearance of the gonads over a 14-month period. Both species appear to have protracted breeding periods with several peaks in spawning activity. Problems encountered with the application of standard sampling and analytical methods to species with such cycles are discussed.  相似文献   
107.
The risk of avian influenza outbreaks in poultry is partially dependent on the probability of contact between domestic poultry and wild birds shedding avian influenza (AI) virus. The major objective of this study was to document wild bird activity on poultry farms to determine which wild bird species should be targeted for AI surveillance in Canada. We collected data in 2 major poultry producing regions of Canada, southwestern Ontario and the Fraser Valley of British Columbia, on the relative abundance of various wild bird species found on poultry farms and on how these species utilized habitat around poultry farms. We reviewed the published literature to determine what was known about AI pathobiology in the species we observed. From these results we created a list of 10 wild bird species that are a priority for further study. These species are the European starling, barn swallow, rock dove, American crow, northwestern crow, American robin, dark-eyed junco, song sparrow, horned lark, and common grackle. Abundance of these and other species varied between provinces and seasons.  相似文献   
108.
Splicing of mammalian precursor transfer RNA (tRNA) molecules involves two enzymatic steps. First, intron removal by the tRNA splicing endonuclease generates separate 5' and 3' exons. In animals, the second step predominantly entails direct exon ligation by an elusive RNA ligase. Using activity-guided purification of tRNA ligase from HeLa cell extracts, we identified HSPC117, a member of the UPF0027 (RtcB) family, as the essential subunit of a tRNA ligase complex. RNA interference-mediated depletion of HSPC117 inhibited maturation of intron-containing pre-tRNA both in vitro and in living cells. The high sequence conservation of HSPC117/RtcB proteins is suggestive of RNA ligase roles of this protein family in various organisms.  相似文献   
109.
Soluble oligomers are common to most amyloids and may represent the primary toxic species of amyloids, like the Abeta peptide in Alzheimer's disease (AD). Here we show that all of the soluble oligomers tested display a common conformation-dependent structure that is unique to soluble oligomers regardless of sequence. The in vitro toxicity of soluble oligomers is inhibited by oligomer-specific antibody. Soluble oligomers have a unique distribution in human AD brain that is distinct from fibrillar amyloid. These results indicate that different types of soluble amyloid oligomers have a common structure and suggest they share a common mechanism of toxicity.  相似文献   
110.
In an increasingly globalized food economy, local agri-food initiatives are promoted as more sustainable alternatives, both for small-scale producers and ecologically conscious consumers. However, revitalizing local agri-food communities in rural agro-industrial regions is particularly challenging. This case study examines Grant and Chelan Counties, two industrial farming regions in rural Central Washington State, distant from the urban fringe. Farmers in these counties have tried diversifying large-scale processing into organics and marketing niche and organic produce at popular farmers markets in Seattle about 200 miles away. Such strategies invoke the question, “How are ‘local’ agri-food networks socially and geographically defined?” The meaning of what constitutes “local” and/or “sustainable” systems merits consideration in the linking of these rural counties with distant urban farmers markets. Employing historical, in-depth interview and survey research, we analyze production and consumption networks and the non-market systems that residents in these counties access for self-provisioning and food security.  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