全文获取类型
收费全文 | 480篇 |
免费 | 43篇 |
专业分类
林业 | 29篇 |
农学 | 18篇 |
83篇 | |
综合类 | 14篇 |
农作物 | 29篇 |
水产渔业 | 69篇 |
畜牧兽医 | 225篇 |
园艺 | 9篇 |
植物保护 | 47篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 20篇 |
2021年 | 25篇 |
2020年 | 37篇 |
2019年 | 33篇 |
2018年 | 30篇 |
2017年 | 28篇 |
2016年 | 27篇 |
2015年 | 21篇 |
2014年 | 24篇 |
2013年 | 28篇 |
2012年 | 34篇 |
2011年 | 37篇 |
2010年 | 16篇 |
2009年 | 17篇 |
2008年 | 23篇 |
2007年 | 18篇 |
2006年 | 12篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 14篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有523条查询结果,搜索用时 15 毫秒
521.
Cortez Lucas Aguilar Marques Júnior José Peluco Rafael Gonçalves Siqueira Diego Silva Siansi Frederico Luiz Barbosa Ronny Sobreira Furlani Carlos Eduardo Angeli Camargo Lívia Arantes Silva Laércio Santos Gomes Romário Pimenta 《Precision Agriculture》2020,21(6):1351-1365
Precision Agriculture - Knowledge of the spatial variability of compaction would minimize the movement of soil and optimize the operation and economic viability of sugarcane activities. The present... 相似文献
522.
Ana Patrícia Souza De Lima Andréa Carla Lira Dos Santos Hozana Leite Dantas Manoel Adrião Gomes Filho Rodrigo Maggioni Maria Raquel Moura Coimbra 《Aquaculture Research》2008,39(13):1461-1466
Loss of genetic variability can be detrimental to a population's survival traits and fitness. These effects are likely to be maximized in shrimp closed broodstock rearing systems where post‐larvae are often produced from crosses of breeders collected from an associated grow‐out farm after mass selection. Longtime broodstock management in closed systems is also expected to lead to reduction in or even complete eradication of genetic variability. The present work aimed at monitoring the genetic variability of a Litopenaeus vannamei hatchery in the state of Pernambuco (Brazil), during three successive replacements, using microsatellite markers. No significant genetic diversity losses have been observed through the values of mean heterozygosity (Ho=0.460 and He=0.660 in the first sample; Ho=0.420 and He=0.620 in the second sample; and Ho=0.600 and He=0.660 in the third sample). However, some alleles appear to have been lost after three replacements. The diversity level was considered to be high and is comparable to those reported for wild populations, suggesting that the original imported founder stock of Brazilian L. vannamei is likely to have had a high genetic diversity, possibly due to multiple origins. 相似文献
523.
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