全文获取类型
收费全文 | 838篇 |
免费 | 44篇 |
国内免费 | 3篇 |
专业分类
林业 | 47篇 |
农学 | 23篇 |
基础科学 | 2篇 |
157篇 | |
综合类 | 59篇 |
农作物 | 43篇 |
水产渔业 | 55篇 |
畜牧兽医 | 442篇 |
园艺 | 19篇 |
植物保护 | 38篇 |
出版年
2024年 | 1篇 |
2023年 | 14篇 |
2022年 | 15篇 |
2021年 | 40篇 |
2020年 | 36篇 |
2019年 | 33篇 |
2018年 | 36篇 |
2017年 | 28篇 |
2016年 | 15篇 |
2015年 | 28篇 |
2014年 | 37篇 |
2013年 | 58篇 |
2012年 | 62篇 |
2011年 | 73篇 |
2010年 | 39篇 |
2009年 | 49篇 |
2008年 | 50篇 |
2007年 | 62篇 |
2006年 | 53篇 |
2005年 | 31篇 |
2004年 | 33篇 |
2003年 | 24篇 |
2002年 | 27篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 9篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1985年 | 1篇 |
1976年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有885条查询结果,搜索用时 0 毫秒
881.
Sebastin Muoz‐Leal lvaro A. Faccini‐Martínez Jairo Prez‐Torres Sandra M. Chala‐Quintero Maria T. Herrera‐Sepúlveda Claudia Cuervo Marcelo B. Labruna 《Zoonoses and public health》2021,68(1):12-18
Bats have been implicated as reservoirs of relapsing fever group spirochaetes since the beginning of the last century. Recently, bat‐associated spirochaetes have been reported as human pathogens. In 1968, a spirochaete was detected in blood of the bat Natalus tumidirostris captured inside the Macaregua cave, Colombia. Data on this microorganism were never published again. The aim of this study was to evaluate the presence of Borrelia DNA in blood from bats of Macaregua cave. We performed molecular analyses using a genus‐specific real‐time PCR targeting the 16S rRNA to detect DNA of Borrelia in blood samples from 46 bats captured in the Macaregua cave. Positive samples were submitted to a battery of PCRs aiming to amply Borrelia 16S rRNA, flaB, glpQ, p66, ospC, clpA, clpX, nifS, pepX, pyrG, recG, rplB and uvrA genes. Seventeen samples were positive for Borrelia after real‐time PCR. With the exception of flaB gene, attempts to amplify further loci were unsuccessful. Nucleotide and amino acid divergences of four flaB haplotypes characterized from blood of Carollia perspicillata showed Borrelia burgdorferi sensu lato (Bbsl) as the most closely related group. A phylogenetic tree including 74 sequences of the genus confirmed this trend, since Borrelia genotypes detected in bats from Macaregua formed a monophyletic group basally positioned to Bbsl. Our results suggest that Borrelia genotypes characterized from bats roosting in the Macaregua cave might constitute a new taxon within the genus. This is the first molecular characterization of a Borrelia sp. in Colombia. 相似文献
882.
Bruna B. Przybulinski Rodrigo G. Garcia Maria Fernanda de C. Burbarelli Claudia M. Komiyama Deivid Kelly Barbosa Fabiana R. Caldara Felipe C. Serpa Vivian A. R. de Castilho Érika Rosendo de Sena Gandra 《Animal Science Journal》2021,92(1):e13539
The objective is to evaluate different bedding materials, including dehydrated grass, on performance and carcass yield and verify the physicochemical and microbiological characteristics of materials. The completely randomized experiment comprised 1,080 chicks in a 3 × 2 factorial design with three levels of dehydrated grass (0%, 25%, and 50%) and two bedding materials (rice husks and shavings). Total microorganism count and physicochemical characteristics, surface temperature of birds, and performance of birds were analyzed up to 42 days of age, when birds were slaughtered, and carcass yield was evaluated. The inclusion of grass showed a higher microbiological count after 1 day, stabilizing with materials after 28 days. The inclusion of 50% of dehydrated grass resulted in a higher surface bed temperature at 42 days. Inclusions above 25% of grass have a lower density and a greater water retention capacity, pH, moisture, and total nitrogen, in addition to a lower FDA in its structure. The highest ammonia emissions occurred with the inclusion of 25% of grass. The inclusion of dehydrated grass did not affect performance and carcass yield, favoring feed conversion at the initial stages. The inclusion of grass can replace up to 25% of shavings without harming physicochemical parameters of materials and birds' performance. 相似文献
883.
Ribeiro Claudia Mello Soares Isabela Ribeiro Mendes Rodrigo Guerrero de Santis Bastos Paula Andrea Katagiri Satie Zavilenski Renato Bacarin de Abreu Hudson Felipe Porto Afreixo Vera 《Tropical animal health and production》2019,51(7):1783-1800
Tropical Animal Health and Production - Neospora caninum is one of the main infectious agents that cause reproductive disorders in cattle. However, knowledge about the prevalence and causal factors... 相似文献
884.
Migena Gjoni Gündemir Tomasz Szara Constantin Spataru Ismail Demircioglu Bernard Turek Georgios Petrovas Mihaela Claudia Spataru 《Anatomia, histologia, embryologia》2023,52(2):190-196
The anatomy of the sternum in birds varies according to their habitats and type of locomotion. In particular, the carina sterni manifest different shape variations. In this study, the shape of the carina sterni was investigated by means of geometric morphometrics. Birds of different types of locomotion were used in the study: flying, swimming, and terrestrial. Ducks and chickens show a wider variety of shapes. Pigeons are the species with the least differences. The margo cranialis carinae in a turkey is the flattest compared to other species. In chickens, the apex carinae is more caudally than the base of the carina sterni. The margo cranialis of the carina sterni in ducks is concave. The differences in centroid size and shape differences between species collectively are statistically significant (p < 0.0001). The most distinct shape contrast is between the duck and turkey (p: 0.0003). Form differences between the ducks and geese as well as between the chicken and turkey are statistically insignificant. There is less variation in the shape of the carina sterni among avian species representing the same type of locomotion. Although there are many comparative morphological and morphometric studies of birds, shape analysis studies revealing the interspecific differences and similarities of the sternum are very limited. Morphology of the carina sterni can be useful in taxonomic investigations. 相似文献
885.
Lydia X. Gan Claudia L. Y. Tan Amirrudin B. Ahmad Yixiong Cai Darren C. J. Yeo 《水产资源保护:海洋与淡水生态系统》2023,33(1):89-101
- Commodity-driven forest conversion represents one of the most severe threats to freshwater biodiversity in Southeast Asia, notably causing population declines and the extinction of freshwater fish species.
- Although a variety of freshwater taxa are likely to be adversely affected by forest conversion, little is known about the impact on ecologically and economically important invertebrates such as decapod crustaceans.
- This study evaluated the impact of forest conversion and land-use change on freshwater Macrobrachium shrimp species, using species richness, abundance, and environmental data collected from 20 streams across southern Peninsular Malaysia. Streams were located in three types of landscape: forest; oil palm plantation; and mixed land use, comprising young secondary forest, small-scale plantations, patches of open and sparsely vegetated areas, and agricultural fields and clearings.
- Generalized linear models showed that even incomplete change from forest habitats to mixed land use and oil palm plantation resulted in significantly lower Macrobrachium native species richness and higher non-native species abundance. Native species richness was positively correlated with canopy cover, leaf litter, substrate size, and dissolved oxygen, and was negatively correlated with water temperature and conductivity. Native species richness was also negatively correlated with non-native species abundance, with non-native species abundance increasing along the human disturbance gradient.
- These results highlight the need for riparian habitat protection to conserve native Macrobrachium and limit the spread of non-native species. A management priority should be to maintain or restore optimum instream habitat conditions for shrimps, which would also benefit fish and other benthic macroinvertebrates. Suitable riparian management requires substantial support and funding from multiple stakeholders, but it can be aligned with other catchment-based strategies to optimize the use of limited resources available for freshwater biodiversity conservation.