全文获取类型
收费全文 | 425篇 |
免费 | 56篇 |
国内免费 | 7篇 |
专业分类
林业 | 110篇 |
农学 | 3篇 |
基础科学 | 2篇 |
11篇 | |
综合类 | 48篇 |
农作物 | 5篇 |
水产渔业 | 43篇 |
畜牧兽医 | 233篇 |
园艺 | 12篇 |
植物保护 | 21篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 6篇 |
2021年 | 34篇 |
2020年 | 20篇 |
2019年 | 27篇 |
2018年 | 35篇 |
2017年 | 38篇 |
2016年 | 32篇 |
2015年 | 14篇 |
2014年 | 37篇 |
2013年 | 36篇 |
2012年 | 33篇 |
2011年 | 14篇 |
2010年 | 20篇 |
2009年 | 19篇 |
2008年 | 15篇 |
2007年 | 18篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1995年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有488条查询结果,搜索用时 31 毫秒
51.
The attachment of the piscine gill parasite, Ergasilus mirabilis Oldewage & van As, 1987 is described by means of scanning electron microscopy and light microscopy. A variety of sensory structures occur on and around the host contact surface of the parasite and proliferation of gill tissue occurs at the site of attachment. It would appear that this proliferation of host tissue results from the feeding behaviour of the parasite rather than the actual attachment thereof. 相似文献
52.
Justin Neu Stephen Demarais Andrew W. Ezell Samuel K. Riffell T. Bently Wigley 《Journal of Sustainable Forestry》2013,32(2):152-172
Information regarding how site preparation techniques affect residual woody structure is lacking for the southern United States in spite of the importance of such structure for many wildlife species. Therefore, we documented retained structure in young loblolly pine (Pinus taeda L.) plantations established using four common site preparation regimes: mechanical only, chemical only, chemical + mechanical, or chemical + prescribed burning. Herbicides reduced live tree density and increased snag density relative to mechanical methods. Prescribed burning reduced density of coarse woody debris (CWD) along with density and volume of piled CWD relative to chemical and mechanical methods. Our results provide a baseline for further studies of wildlife and retained structure in southern pine forests. 相似文献
53.
54.
55.
56.
野生动物及其产品在世界范围内广泛交易,由此引发的偷猎一直是物种保护的主要威胁。现有的干预措施和执法不能完全规避由此造成的物种濒危和灭绝,有专家提出人工繁育可以减轻野生种群压力。基于本文研究发现,只有符合以下条件和标准,野生动物人工养殖才能有益于物种保护:1)合法产品成为替代品且消费者对野生动物没有偏好;2)满足大部分需求且需求不会增加;3)合法产品更具成本效益,以打击黑市价格;4)野生动物养殖不依赖野生种群进行补给;5)没有非法产品混入合法商业贸易。很多野生动物难以满足以上全部条件和标准,因此人工养殖和贸易可能对物种保护产生相反效果。然而,对于某些能够全面满足以上条件的物种,人工繁育可视为种群保护的有力工具。对于这些物种,未来的研究应侧重于合法产品对市场动态的影响、有效执法以及能够区分人工繁殖和野生捕获物种的取证等方面。 相似文献
57.
Loewenstein L McLachlan-Troup T Hartley M English A 《Australian veterinary journal》2008,86(6):242-245
Objective To survey free-living platypuses for evidence of Leptospira interrogans .
Methods A serological study of Leptospira antibodies was carried out on 21 platypuses captured between May and October 2001 in the Wollondilly River 200 km south of Sydney, New South Wales.
Results Positive reactions, all to the L Hardjo serovar, were seen in 14 (66%) of the captured animals, with adult males showing a higher prevalence of antibodies than adult females. Several individual platypuses showed a high titre of L Hardjo antibodies, and some animals demonstrated cross-reactions to the serovars L Medanensis and L Kremastos.
Conclusion The serological findings demonstrate that these animals are constantly exposed to infection with Leptospira in their environment, but it is not known if platypuses suffer from clinical leptospirosis or if they mount an immune response, but are unaffected by the bacteria. The prevalence of Leptospira infection among the platypus population could not be precisely estimated because of the unknown number of individuals inhabiting the Wollondilly River inside the survey property. Domestic livestock, mostly cattle, may be the major source of Leptospira infection. The effects of this disease on population dynamics and on reproduction in wild platypuses are not well understood. The role of other wildlife in the transmission and maintenance of Leptospira in the environment is unknown. 相似文献
Methods A serological study of Leptospira antibodies was carried out on 21 platypuses captured between May and October 2001 in the Wollondilly River 200 km south of Sydney, New South Wales.
Results Positive reactions, all to the L Hardjo serovar, were seen in 14 (66%) of the captured animals, with adult males showing a higher prevalence of antibodies than adult females. Several individual platypuses showed a high titre of L Hardjo antibodies, and some animals demonstrated cross-reactions to the serovars L Medanensis and L Kremastos.
Conclusion The serological findings demonstrate that these animals are constantly exposed to infection with Leptospira in their environment, but it is not known if platypuses suffer from clinical leptospirosis or if they mount an immune response, but are unaffected by the bacteria. The prevalence of Leptospira infection among the platypus population could not be precisely estimated because of the unknown number of individuals inhabiting the Wollondilly River inside the survey property. Domestic livestock, mostly cattle, may be the major source of Leptospira infection. The effects of this disease on population dynamics and on reproduction in wild platypuses are not well understood. The role of other wildlife in the transmission and maintenance of Leptospira in the environment is unknown. 相似文献
58.
59.
60.
María Ortuo Maria S. Latrofa María A. Iborra Pedro Prez‐Cutillas Luis J. Bernal Jos Risueo Clara Muoz Ana Bernal Pedro F. Snchez‐Lopez Manuel Segovia Giada Annoscia Carla Maia Sofia Cortes Lenea Campino Domenico Otranto Eduardo Berriatua 《Zoonoses and public health》2019,66(8):961-973
Leishmania infantum causes human and canine leishmaniosis. The parasite, transmitted by phlebotomine sand flies, infects species other than dogs and people, including wildlife, although their role as reservoirs of infection remains unknown for most species. Molecular typing of parasites to investigate genetic variability and evolutionary proximity can help understand transmission cycles and designing control strategies. We investigated Leishmania DNA variability in kinetoplast (kDNA) and internal transcribed spacer 2 (ITS2) sequences in asymptomatically infected wildlife (n = 58) and symptomatically and asymptomatically infected humans (n = 38) and dogs (n = 15) from south‐east Spain, using single nucleotide polymorphisms (SNPs) and in silico restriction fragment length polymorphism (RFLP) analyses. All ITS2 sequences (n = 76) displayed a 99%–100% nucleotide identity with a L. infantum reference sequence, except one with a 98% identity to a reference Leishmania panamensis sequence, from an Ecuadorian patient. No heterogeneity was recorded in the 73 L. infantum ITS2 sequences except for one SNP in a human parasite sequence. In contrast, kDNA analysis of 44 L. infantum sequences revealed 11 SNP genotypes (nucleotide variability up to 4.3%) and four RFLP genotypes including B, F and newly described S and T genotypes. Genotype frequency was significantly greater in symptomatic compared to asymptomatic individuals. Both methods similarly grouped parasites as predominantly or exclusively found in humans, in dogs, in wildlife or in all three of them. Accordingly, the phylogenetic analysis of kDNA sequences revealed three main clusters, two as a paraphyletic human parasites clade and a third including dogs, people and wildlife parasites. Results suggest that Leishmania infantum genetics is complex even in small geographical areas and that, probably, several independent transmission cycles take place simultaneously including some connecting animals and humans. Investigating these transmission networks may be useful in understanding the transmission dynamics, infection risk and therefore in planning L. infantum control strategies. 相似文献