全文获取类型
收费全文 | 795篇 |
免费 | 50篇 |
国内免费 | 1篇 |
专业分类
林业 | 39篇 |
农学 | 18篇 |
基础科学 | 1篇 |
148篇 | |
综合类 | 100篇 |
农作物 | 47篇 |
水产渔业 | 94篇 |
畜牧兽医 | 300篇 |
园艺 | 17篇 |
植物保护 | 82篇 |
出版年
2023年 | 13篇 |
2022年 | 24篇 |
2021年 | 42篇 |
2020年 | 39篇 |
2019年 | 36篇 |
2018年 | 41篇 |
2017年 | 30篇 |
2016年 | 23篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 41篇 |
2012年 | 46篇 |
2011年 | 45篇 |
2010年 | 31篇 |
2009年 | 25篇 |
2008年 | 34篇 |
2007年 | 31篇 |
2006年 | 31篇 |
2005年 | 26篇 |
2004年 | 22篇 |
2003年 | 22篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1995年 | 6篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 9篇 |
1969年 | 6篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1902年 | 3篇 |
1900年 | 5篇 |
1898年 | 2篇 |
1897年 | 2篇 |
1896年 | 3篇 |
1887年 | 2篇 |
排序方式: 共有846条查询结果,搜索用时 15 毫秒
841.
Santos F Coppede JS Pereira AL Oliveira LP Roberto PG Benedetti RB Zucoloto LB Lucas F Sobreira L Marins M 《Veterinary journal (London, England : 1997)》2009,179(1):145-148
Canine monocytic ehrlichiosis caused by Ehrlichia canis is endemic in many regions of Brazil. Since thrombocytopenia is a common finding in infected dogs, many clinicians tend to use it as an indication for antibiotic treatment. Polymerase chain reaction (PCR) and nested PCR were used to study the presence of E. canis, Anaplasma platys and Babesia spp. in thrombocytopenic and non-thrombocytopenic dogs from Ribeirão Preto, Brazil. Despite the high prevalence of E. canis infection among thrombocytopenic dogs, 46.7% of the thrombocytopenic dogs studied were either infected with Babesia spp. or A. platys or not infected with any of the three pathogens. There was a high incidence (25.4%) of E. canis infection in non-thrombocytopenic dogs. Although infection with E. canis should be considered in thrombocytopenic dogs, the final diagnosis needs to be confirmed by complementary tests such as blood smears and PCR to avoid the unnecessary use of antibiotics. 相似文献
842.
The first larval feeding in Crassostrea gigas, detected by epifluorescence microscope, occurred 24 h after fertilization at 24°C and 30 h at 21°C. The amount of algal cells (Pavlova lutheri and Isochrysis galbana) necessary to have larvae with filled stomachs was estimated to be 800 cells per day at 24°C and 400 cells per day at 21°C. 相似文献
843.
Reinaldo Melillo Filho Rodrigo Takata André Eduardo Heringer Santos Walisson de Souza e Silva Aline Leite Ikeda Lucas Alves Rodrigues José Cláudio Epaminondas dos Santos Ana Lúca Salaro Ronald Kennedy Luz 《Aquaculture Research》2014,45(12):1913-1920
This study evaluated the efficiency of the drainage system during the larviculture of Lophiosilurus alexandri. Moreover, we assessed the best feeding rate after feed training for juvenile production. The study was performed in three phases over 87 days. In phase 1 (40 days), larvae were fed live food and posteriorly submitted to feed training in two drainage systems: water drained on the surface (DS), and water drained into a tank column (DI). In the second phase (30 days), using only the DS system juveniles were fed a formulated diet at feeding rates, 2, 4, 6 and 8% of body wet weight. In the third phase (17 days), the fish from the second phase were fed until apparent satiation. At the first phase, the animals in the DS system exhibited greater survival rates and growth. The best feeding rate for daily weight gain, specific growth rate (SGR) and mean body weights were similar: 5.57, 5.13 and 5.68% respectively. In the third phase, an increased SGR was observed in the treatment groups that received lower feeding rates in the second phase (2 and 4%), which could indicate a possible compensatory growth rate. 相似文献
844.
S. Y. Liu Z. Liu B. D. L. Fitt N. Evans S. J. Foster † Y. J. Huang A. O. Latunde-Dada J. A. Lucas 《Plant pathology》2006,55(3):401-412
Effects of pretreatment of Brassica napus leaves with ascospores of Leptosphaeria biglobosa or chemical defence activators [acibenzolar- S -methyl (ASM) or menadione sodium bisulphite (MSB)] on infection by ascospores of Leptosphaeria maculans (phoma stem canker) and development of disease were studied in controlled-environment (phoma leaf spot) and field (phoma leaf spot and stem canker) experiments. In controlled-environment experiments, pretreatment of oilseed rape leaves (cv. Madrigal) with L. biglobosa , ASM or MSB delayed the appearance of L. maculans phoma leaf spot lesions. These pretreatments also decreased the phoma leaf spot lesion area in both pretreated leaves (local effect) and untreated leaves (systemic effect). In winter oilseed rape field experiments in the 2002/03 and 2003/04 growing seasons, pretreatment with L. biglobosa or ASM in October/November decreased not only the number of phoma leaf spot lesions per leaf caused by L. maculans in autumn/winter, but also the severity of phoma stem canker in the subsequent spring/summer. Effects were greater in 2002/03 (when natural L. maculans ascospore release began in September 2002) than in 2003/04 (when ascospore release began in December following a period of dry weather in August/September 2003). These results suggest that pretreatment with biological or chemical defence activators can induce local and systemic resistance to L. maculans , with both short-term effects on the development of phoma leaf spotting and long-term effects on the development of stem canker 8 months later. 相似文献
845.
Retrospective evaluation of hypersensitivity reactions and anaphylaxis in dogs (2003–2014): 86 cases
846.
Lucas Silva Azevedo Incio Abreu Pestana Marcelo Gomes Almeida Wanderley Rodrigues Bastos Cristina Maria Magalhes Souza 《Ecology of Freshwater Fish》2022,31(1):72-80
Floodplain lakes are ecosystems characterised by annual flood and dry cycles. Fish ecology is influenced by the flood pulse due to the large influx of allochthonous food resources and diversification of habitats during the flood cycle, while during the dry cycle, fishes tend to be confined in reduced habitat. The aim of this study was to evaluate the seasonal variation in trophic niche width and overlap of four species—Mylossoma duriventre, Prochilodus nigricans, Cichla.pleiozona and Serrasalmus rhombeus—in an Amazonian floodplain lake. Stable isotope analyses were used to estimate trophic niche width and overlap during the flood and dry seasons. We hypothesised broader niche width for all species during the flood cycle and a higher degree of overlap between the two piscivorous fishes during the dry cycle. Isotopic niche width was 72% broader for P. nigricans, 61% for S. rhombeus and 54% for C. pleiozona during the dry cycle, which did not support our hypothesis. Core niche width overlaps were not observed between piscivorous species in either flood or dry cycle. The results indicate that seasonal variation in isotopic niche width is specific to feeding habit. Understanding how fish trophic ecology responds to changes in the hydrological regime during the seasons is crucial for sustainable fishery management in a region where many people rely heavily on fish for nutritional and economic purposes. 相似文献