全文获取类型
收费全文 | 143篇 |
免费 | 16篇 |
专业分类
林业 | 6篇 |
农学 | 1篇 |
19篇 | |
综合类 | 26篇 |
农作物 | 8篇 |
水产渔业 | 27篇 |
畜牧兽医 | 63篇 |
园艺 | 6篇 |
植物保护 | 3篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 10篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 17篇 |
2007年 | 14篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 1篇 |
2002年 | 12篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有159条查询结果,搜索用时 31 毫秒
81.
A'Hearn MF Belton MJ Delamere WA Feaga LM Hampton D Kissel J Klaasen KP McFadden LA Meech KJ Melosh HJ Schultz PH Sunshine JM Thomas PC Veverka J Wellnitz DD Yeomans DK Besse S Bodewits D Bowling TJ Carcich BT Collins SM Farnham TL Groussin O Hermalyn B Kelley MS Kelley MS Li JY Lindler DJ Lisse CM McLaughlin SA Merlin F Protopapa S Richardson JE Williams JL 《Science (New York, N.Y.)》2011,332(6036):1396-1400
Understanding how comets work--what drives their activity--is crucial to the use of comets in studying the early solar system. EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus, taking both images and spectra. Unlike large, relatively inactive nuclei, this nucleus is outgassing primarily because of CO(2), which drags chunks of ice out of the nucleus. It also shows substantial differences in the relative abundance of volatiles from various parts of the nucleus. 相似文献
82.
Clustering by passing messages between data points 总被引:9,自引:0,他引:9
83.
Munn DH Sharma MD Lee JR Jhaver KG Johnson TS Keskin DB Marshall B Chandler P Antonia SJ Burgess R Slingluff CL Mellor AL 《Science (New York, N.Y.)》2002,297(5588):1867-1870
Antigen-presenting cells (APCs) can induce tolerance or immunity. We describe a subset of human APCs that express indoleamine 2,3-dioxygenase (IDO) and inhibit T cell proliferation in vitro. IDO-positive APCs constituted a discrete subset identified by coexpression of the cell-surface markers CD123 and CCR6. In the dendritic cell (DC) lineage, IDO-mediated suppressor activity was present in fully mature as well as immature CD123+ DCs. IDO+ DCs could also be readily detected in vivo, which suggests that these cells may represent a regulatory subset of APCs in humans. 相似文献
84.
The structure of haplotype blocks in the human genome 总被引:1,自引:0,他引:1
Gabriel SB Schaffner SF Nguyen H Moore JM Roy J Blumenstiel B Higgins J DeFelice M Lochner A Faggart M Liu-Cordero SN Rotimi C Adeyemo A Cooper R Ward R Lander ES Daly MJ Altshuler D 《Science (New York, N.Y.)》2002,296(5576):2225-2229
Haplotype-based methods offer a powerful approach to disease gene mapping, based on the association between causal mutations and the ancestral haplotypes on which they arose. As part of The SNP Consortium Allele Frequency Projects, we characterized haplotype patterns across 51 autosomal regions (spanning 13 megabases of the human genome) in samples from Africa, Europe, and Asia. We show that the human genome can be parsed objectively into haplotype blocks: sizable regions over which there is little evidence for historical recombination and within which only a few common haplotypes are observed. The boundaries of blocks and specific haplotypes they contain are highly correlated across populations. We demonstrate that such haplotype frameworks provide substantial statistical power in association studies of common genetic variation across each region. Our results provide a foundation for the construction of a haplotype map of the human genome, facilitating comprehensive genetic association studies of human disease. 相似文献
85.
Enhancing conservation of Australian freshwater ecosystems: identification of freshwater flagship fishes and relevant target audiences 下载免费PDF全文
Brendan C Ebner David L Morgan Adam Kerezsy Scott Hardie Stephen J Beatty Jamie E Seymour James A Donaldson Simon Linke Stirling Peverell David Roberts Thomas Espinoza Nadine Marshall Frederieke J Kroon Damien W Burrows Ryan R J McAllister 《Fish and Fisheries》2016,17(4):1134-1151
Flagship species, especially mammals and birds, are commonly used to increase awareness of conservation issues in marine and terrestrial ecosystems. However, flagship species oriented programs are often ad hoc with initiatives scarce in the freshwater context. Here, we aim to identify potential flagship candidates that would appeal to a broad cross section of society at a continental scale where freshwater ecosystems are under threat from human impacts. We identified 19 species from a list of 299 Australian freshwater fishes on the basis of body size, trophic guild and threatened species status assuming these characteristics of flagship species are transferable from previous work on terrestrial flagship species. We considered the potential of species to be of international appeal but focused mostly on eight relevant interest groups within Australia. This followed the rationale that public engagement with conservation issues in freshwater systems might be more effective if the link between fish species and the decisions people make were better understood, and we acknowledge the diverging interests of stakeholders. This scoping work contributes towards addressing the challenges of connecting societies to the principles of sharing water resources with ecosystems, and represents the first continental‐scale assessment of its kind. 相似文献
86.
87.
88.
Mitochondrial DNA short tandem repeats unveil hidden population structuring and migration routes of an endangered marine turtle 下载免费PDF全文
Yaron Tikochinski Phil Bradshaw Angela Mastrogiacomo Annette Broderick Alon Daya Andreas Demetropoulos Simon Demetropoulos Nicolas‐George Eliades Wayne Fuller Brendan Godley Yakup Kaska Yaniv Levy Robin Snape Lucy Wright Carlos Carreras 《水产资源保护:海洋与淡水生态系统》2018,28(4):788-797
89.
Ecosystem services: Classification for valuation 总被引:4,自引:0,他引:4
This letter is in response to an article by Ken Wallace titled “Classifications of ecosystem services: problems and solutions” (Biological Conservation 139, 2007). This letter discusses the points we see as problematic with Wallace’s framework and sets out our conceptualization of linking ecosystem services with human welfare. In this letter we suggest that utilizing the terms intermediate services, final services and benefits should go a long way to clearing up much of the ambiguity in ecosystem services typologies, especially for economic valuation purposes. As Wallace points out, clearly defining and organizing the concept of ecosystem services is not just a semantic decision, but it is integral to operationalizing something that can clearly illuminate tradeoffs in natural resource management. 相似文献
90.