全文获取类型
收费全文 | 823篇 |
免费 | 64篇 |
专业分类
林业 | 28篇 |
农学 | 14篇 |
基础科学 | 2篇 |
88篇 | |
综合类 | 94篇 |
农作物 | 28篇 |
水产渔业 | 32篇 |
畜牧兽医 | 546篇 |
园艺 | 31篇 |
植物保护 | 24篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 20篇 |
2020年 | 28篇 |
2019年 | 43篇 |
2018年 | 27篇 |
2017年 | 32篇 |
2016年 | 29篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 37篇 |
2012年 | 68篇 |
2011年 | 77篇 |
2010年 | 42篇 |
2009年 | 25篇 |
2008年 | 67篇 |
2007年 | 54篇 |
2006年 | 46篇 |
2005年 | 30篇 |
2004年 | 43篇 |
2003年 | 39篇 |
2002年 | 39篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 9篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1974年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有887条查询结果,搜索用时 321 毫秒
91.
92.
93.
Foley J Hurley K Pesavento PA Poland A Pedersen NC 《Journal of Feline Medicine and Surgery》2006,8(1):55-61
Virulent systemic feline calicivirus (VS-FCV) is a novel, emerging pathogen with mortality up to 67% even in previously healthy adult cats; VS-FCV has resulted in at least six epidemics since 1998. Affected cats have systemic vascular compromise and hemorrhagic-fever like signs in part due to viral invasion of epithelium and endothelium, coupled with host cytokine responses. Affected skin tissues had, on average, 3.8 elevated cytokines compared with control tissue, with prominent upregulation in IL-10, TNF-alpha, and MIP-1alpha. Sequencing of most of the genomes of two VS-FCV strains documented patterns of virus relatedness and implicated changes in the capsid gene in the emerging phenotype, possibly through initiation of immune mechanisms manifest in the cytokine changes. Understanding the features contributing to the emergence of this disease is critical for management and prevention of this and similar outbreaks attributable to RNA viruses in animals and humans. 相似文献
94.
Grimberg A Baur H Bochsler P Bühler F Burnett DS Hays CC Heber VS Jurewicz AJ Wieler R 《Science (New York, N.Y.)》2006,314(5802):1133-1135
Lunar soils have been thought to contain two solar noble gas components with distinct isotopic composition. One has been identified as implanted solar wind, the other as higher-energy solar particles. The latter was puzzling because its relative amounts were much too large compared with present-day fluxes, suggesting periodic, very high solar activity in the past. Here we show that the depth-dependent isotopic composition of neon in a metallic glass exposed on NASA's Genesis mission agrees with the expected depth profile for solar wind neon with uniform isotopic composition. Our results strongly indicate that no extra high-energy component is required and that the solar neon isotope composition of lunar samples can be explained as implantation-fractionated solar wind. 相似文献
95.
Lord LK Wittum TE Ferketich AK Funk JA Rajala-Schultz P Kauffman RM 《Journal of the American Veterinary Medical Association》2006,229(1):48-54
OBJECTIVE: To examine changes between 1996 and 2004 in regard to numbers of animals handled, medical care provided, expenses, numbers of employees, and agency policies for animal care and control agencies in Ohio. DESIGN: Cross-sectional survey. SAMPLE POPULATION: 223 animal care and control agencies. PROCEDURES: A questionnaire was mailed to animal care and control agencies in Ohio to collect information for 2004; results were compared with published results of a similar survey. RESULTS: 165 of the 223 (74%) agencies responded. Estimated total number of animals handled in 2004 was 315,519, which represented a decrease of 7% compared with 1996. However, although number of dogs taken in decreased 17%, number of cats taken in increased 20%. Between 1996 and 2004, the euthanasia rate decreased from 65.3% to 56.8%, and the adoption rate increased from 24.5% to 33.6%. Number of dogs euthanatized decreased 39%, but number of cats euthanatized increased 14%. The proportion of agencies with a spay-neuter policy increased from 56% to 71%, and the proportion that maintained an association with a veterinarian increased from 39% to 80%. For dogs handled by county dog warden agencies, the odds of euthanasia were higher if the agency did not have a spay-neuter policy (odds ratio, 1.36). CONCLUSIONS: Results suggest that the status of dogs handled by animal care and control agencies in Ohio improved between 1996 and 2004, but that the status of cats deteriorated. 相似文献
96.
Bacterial canker caused by Clavibacter michiganensis subsp. michiganensis is known to cause significant economic losses to tomato production worldwide. Biological control has been proposed as an alternative to current chemical containment methods, which are often inefficient and may leave adverse effects on the environment. However, only little headway has so far been made in developing biocontrol strategies against C. michiganensis subsp. michiganensis. To address this knowledge gap, we investigated the antagonistic capacity of PCA, produced by Pseudomonas sp. LBUM223, and DAPG and HCN, both produced by Pseudomonas sp. LBUM300, on C. michiganensis subsp. michiganensis under in vitro and in planta conditions. Nonsynthesizing isogenic mutants of the producer strains were also developed to further dissect the role of each individual metabolite on C. michiganensis subsp. michiganensis biological control. Novel specific quantitative polymerase chain reaction TaqMan assays allowed quantification of C. michiganensis subsp. michiganensis in tomato plants and rhizospheric soil. Pseudomonas spp. LBUM223 and LBUM300 significantly repressed C. michiganensis subsp. michiganensis growth in vitro, while their respective nonproducing mutants showed less or no significant antagonistic activity. In planta, only Pseudomonas sp. LBUM300 was capable of significantly reducing disease development and C. michiganensis subsp. michiganensis rhizospheric population, suggesting that the production of both DAPG and HCN was involved. In summary, simultaneous DAPG/HCN production by Pseudomonas sp. LBUM300 shows great potential for controlling bacterial canker of tomato. 相似文献
97.
98.
Amy Zader 《Agriculture and Human Values》2012,29(1):53-63
This paper seeks to clarify and strengthen the ways that cultural economy is used as an analytical tool and methodological
approach to studying agro-food systems. The theoretical concept of cultural economy has received much attention in economic
and cultural geography over the past decade. However, use of the term remains arguably vague and ambiguous. This paper argues
that cultural economy is most constructive when regarded as a new epistemological approach to society and the economy. A focus
on the ways that food is known as “quality” represents the material and symbolic practices that contribute to a new way of
thinking about the economy. This point is illustrated in a case study of japonica rice grown in northeast China. A unique
combination of social, economic, political, historical, and geographical factors come together in this region to produce rice
that is generally identified within China today as “quality” rice. Situating northeast japonica rice in a greater context
of a “politics of quality” in Chinese society, this case emphasizes the value of cultural economy to understand agro-food
systems. 相似文献
99.
100.