全文获取类型
收费全文 | 335篇 |
免费 | 24篇 |
专业分类
林业 | 20篇 |
农学 | 3篇 |
25篇 | |
综合类 | 66篇 |
农作物 | 10篇 |
水产渔业 | 35篇 |
畜牧兽医 | 190篇 |
植物保护 | 10篇 |
出版年
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 18篇 |
2012年 | 11篇 |
2011年 | 6篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 13篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 16篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 18篇 |
1988年 | 26篇 |
1987年 | 20篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1975年 | 6篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1967年 | 2篇 |
1958年 | 1篇 |
1907年 | 4篇 |
1903年 | 1篇 |
1902年 | 1篇 |
排序方式: 共有359条查询结果,搜索用时 31 毫秒
351.
W Booth 《Science (New York, N.Y.)》1989,244(4903):418-419
352.
353.
354.
NIH scientists agonize over technology transfer 总被引:1,自引:0,他引:1
W Booth 《Science (New York, N.Y.)》1989,243(4887):20-21
355.
356.
Wang W Black SS Edwards MD Miller S Morrison EL Bartlett W Dong C Naismith JH Booth IR 《Science (New York, N.Y.)》2008,321(5893):1179-1183
How ion channels are gated to regulate ion flux in and out of cells is the subject of intense interest. The Escherichia coli mechanosensitive channel, MscS, opens to allow rapid ion efflux, relieving the turgor pressure that would otherwise destroy the cell. We present a 3.45 angstrom-resolution structure for the MscS channel in an open conformation. This structure has a pore diameter of approximately 13 angstroms created by substantial rotational rearrangement of the three transmembrane helices. The structure suggests a molecular mechanism that underlies MscS gating and its decay of conductivity during prolonged activation. Support for this mechanism is provided by single-channel analysis of mutants with altered gating characteristics. 相似文献
357.
This study examines the use of age-structured maximum likelihood and Bayesian approaches for stock assessment of the Namibian monkfish, Lophius vomerinus, resource with questionable data, in which time series are short, abundance indices are variable, and research data conflict with commercial data. Bayesian approaches with both noninformative and informative priors are investigated to determine if they enhance estimation stability. Three data scenarios are assessed: commercial and research survey data, research survey data only, and commercial data only. Both statistical approaches show that resource abundance has decreased with exploitable biomass estimated at approximately 44% of pristine levels. The maximum likelihood and the Bayesian approach with noninformative priors result in similar estimates. As the abundance data contained little information pertaining to possible density dependence within the stock–recruit relationship, only a Bayesian approach with informative priors reduces uncertainty in the steepness parameter h. Estimated management quantities are sensitive both to the set of data sources and whether prior information was informative or not. The strengths of the Bayesian approach include the integration of prior information with uncertain data, the exploration of data conflicts, and the ability to show the uncertainty in estimates of management parameters. Its weakness is that estimation stability is dependent on the choice of priors, which alters some posterior distributions of management quantities. 相似文献
358.
Retrospective analysis of the radiographs of horses with carpal valgus, presented to the Iowa State University Veterinary Teaching Hospital from 1987-1996, were used to compare 2 methods of geometric analysis for finding the total angle of deviation. The pivot point angle method and the individual joint angle method were found to be comparable for determining the total angle of deviation. The individual joint angle method was used to analyse individual carpal joint angles and physis angle in joints with carpal valgus, as well as the changes that occurred in response to surgical correction. Multiple joint involvement was common with carpal valgus; and surgical manipulation caused a change in angle at all joints. Use of the individual joint angle method for evaluating carpal valgus may aid the surgeon in making a more accurate prognosis. 相似文献
359.
L. van Dijk A. Hayton D. C. J. Main A. Booth A. King D. C. Barrett H. J. Buller K. K. Reyher 《Zoonoses and public health》2017,64(6):476-484
Pressures for more responsible use of anti‐microbial (AM) medicines in food animals are likely to increase from policymakers and the food industry, including retailers. To address this challenge, participatory approaches to welfare interventions and disease prevention may also be necessary alongside more conventional regulatory measures. This article describes the process of enabling groups of dairy producers to use a participatory policy making approach to develop an AM stewardship policy. The policy includes measures agreed to by all producers for more responsible use of AMs, whilst maintaining or improving dairy herd health and welfare. This process provided a unique opportunity for collaboration and dialogue between producers, veterinarians, industry and researchers. Its participatory nature encouraged comprehensive learning for all involved. This integration of science with producers’ knowledge and experience led to credible and practical recommendations designed to deliver real and lasting change in AM use. The multidisciplinary nature of this research marks a significant contribution to embedding social science skills and approaches into the veterinary sphere. As an initial step in creating better understanding of how participatory approaches with farmers can be applied in a UK context and more widely, this work serves as a pilot for promoting more responsible use of veterinary medicines in other livestock species. 相似文献