全文获取类型
收费全文 | 236篇 |
免费 | 31篇 |
专业分类
林业 | 21篇 |
农学 | 3篇 |
基础科学 | 1篇 |
42篇 | |
综合类 | 6篇 |
农作物 | 25篇 |
水产渔业 | 13篇 |
畜牧兽医 | 109篇 |
园艺 | 2篇 |
植物保护 | 45篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 12篇 |
2012年 | 15篇 |
2011年 | 22篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 11篇 |
2007年 | 11篇 |
2006年 | 14篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 1篇 |
排序方式: 共有267条查询结果,搜索用时 31 毫秒
261.
Ana Laura Tomas Daniela Eliana Sganga Agustina Marciano Laura Susana Lpez Greco 《Aquaculture Nutrition》2020,26(4):1198-1210
In aquarium industry trade markets, Neocaridina davidi, the “red cherry” shrimp, is one of the most attractive ornamental shrimps due to the striking reddish coloration of females. Five commercial diets formulated for ornamental species were evaluated over a 90‐day period in N. davidi males and females, based on survival, biochemical composition, body weight, carotenoid content and body coloration. Furthermore, histological and histochemical analyses of the male reproductive system were performed to evaluate the spermatophore quality. In all treatments, survival was >80%, and protein content was similar in both female and male shrimps. Lipid content was higher in females and males fed on a diet having the highest lipid level. Carotenoid content was higher and body coloration was brighter in females and males fed on a diet containing the highest carotenoid level. Histological and histochemical analyses of the spermatophore structure and composition showed no differences among diets, suggesting that the five commercial diets are adequate for satisfactory growth and spermatophore quality of N. davidi. The diverse sources and quantities of carotenoids in the highest carotenoid level diet render it more suitable for colour enhancement of this species. 相似文献
262.
Ingebrigt Uglem Kilian Toledo‐Guedes Pablo Sanchez‐Jerez Eva Marita Ulvan Tor Evensen Bjrn Steinar Sther 《Aquaculture Research》2020,51(4):1720-1730
Salmon farms attract large amounts of wild fish, which prey on uneaten feed pellets. The modified diet of the wild fish aggregating at salmon farms may reduce the flesh quality of the fish, influencing the local fisheries. We compared the quality of saithe (Pollachius virens) captured near (farm associated—FA) or more than 5 km away (un‐associated—UA) from salmon farms in Norway. The fish were captured during summer, autumn and spring using two commercial fishing methods (jigging and bottom nets). Overall, the fillet quality of FA saithe was good, although it was clearly reduced for almost 10% of the catch. Moreover, the quality of the FA saithe was significantly reduced compared with UA saithe, but the differences were small. Our results also showed that fish caught with jigging had better quality than fish caught with nets, and that fish that died in the nets were of lower quality than fish that were alive after hauling. There was no clear variation among seasons in fillet quality. Although no major and overall differences in quality were found between FA and UA saithe, reduced quality for even a modest proportion of the fish may influence the value of the total catch. 相似文献
263.
Grazieli Maboni E. Jane Kelly Chad S. Clancy Eliana De Luca Thomas J. Baldwin Arnaud J. Van Wettere Albert J. Kane Summer Peterson V. Gus Warr Dona A. Bastian Susan Sanchez 《Journal of veterinary diagnostic investigation》2022,34(1):167
A mortality event among recently captured feral donkeys (Equus asinus) occurred in south-central Utah in 2016. The deaths were sporadic, and clinical signs were indicative of respiratory disease, likely associated with an infectious etiology. Ten of 13 donkeys autopsied had moderate-to-severe interstitial fibrosing pneumonia, and one had pyogranulomatous pneumonia. Consensus PCRs directed toward the DNA polymerase and DNA packaging terminase subunit 1 for herpesviruses were performed followed by sequencing of the PCR amplicons and phylogenetic analysis. Asinine herpesvirus 4 (AsHV4) and 5 (AsHV5) were consistently identified in lung tissues of affected donkeys. No other herpesviruses were identified, and herpesviral DNA was not detected in lung tissues of 2 donkeys without evidence of respiratory disease. The detection of asinine gammaherpesviruses may have been associated with the lesions described. AsHV4 and AsHV5 have been reported in previous studies as novel gammaherpesviruses based on sequences obtained from donkeys with interstitial pneumonia and marked syncytial cell formation. Our findings suggest that the association of asinine gammaherpesviruses with respiratory conditions in equids deserves further attention. 相似文献
264.
265.
Malathion resistance of a field-collected population of Rhizopertha dominica (Coleoptera: Bostrichidae) from Mexico was evaluated and the resistance mechanisms were characterized both in vivo and in vitro. The Mexican population showed a resistance level of 50-fold at LC50 as compared with that of a susceptible laboratory population. Malathion bioassays with the synergists triphenyl phosphate, piperonyl butoxide and diethyl maleate suggested that esterases were likely to contribute to the resistance whereas cytochrome P450 monooxygenases and glutathione S-transferases were not. In-vitro assays of esterases indicated that the general esterase activity was 1·3-fold higher in the Mexican population than in the susceptible population. However, the phosphotriesterase activity in the resistant population was 3·7-fold higher than in the susceptible population. Significantly higher phosphotriesterase activity in the resistant population was further indicated by 3·4-fold increase of Vmax in enzyme kinetics and higher frequency of individuals with high phosphotriesterase activity in this population. All these findings suggested that phosphotriesterases play a role in malathion resistance in the Mexican population of lesser grain borer. © 1998 SCI 相似文献
266.
Ceres Duarte Guedes Cabral de Almeida Tarlei Arriel Botrel Rod J. Smith 《Irrigation Science》2009,27(3):209-214
The microtube is a simple and cheap emitter that was widely used throughout the world in the early days of drip irrigation.
Its length can be adjusted according to the pressure distribution along the lateral line and the discharge from the microtube
can be adjusted by its length. This not only counters the pressure loss due to pipe friction but also makes it suitable for
undulating and hilly conditions, where pressure in the lateral line varies considerably according to the differences in elevation.
This is the major problem facing the designer, i.e., emitter flow changes as the acting pressure head changes. In this study,
a novel micro-sprinkler system is proposed that uses microtube as the emitter and where the length of the microtube can be
varied in response to pressure changes along the lateral to give uniformity of emitter discharges. The objective of this work
is to develop and validate empirical and semi-theoretical equations for the emitter hydraulics. Laboratory testing of two
microtube emitters of different diameter over a range of pressures and discharges was used in the development of the equations
relating pressure and discharge, and pressure and length for these emitters. The equations proposed will be used in the design
of the micro-sprinkler system, to determine the length of microtube required to give the nominal discharge for any given pressure.
The semi-theoretical approach underlined the importance of accurate measurements of the microtube diameter and the uncertainty
in the estimation of the friction factor for these tubes. 相似文献
267.
Francisco Gerson Araújo Mrcia Cristina Costa de Azevedo Gustavo Henrique Soares Guedes Wagner Uehara 《Ecology of Freshwater Fish》2022,31(1):45-59
Increases in temperatures over the last century, more intensively after the eighties, were recorded in several databases for the south-eastern Brazil. These increases are likely to change fish communities in aquatic systems by decreasing abundances, biomass and sizes of some species more sensitive to climate change. Reservoirs may be particularly susceptible to the effects of climate change, as they isolate previously connected areas limiting fish dispersal and migration, as well as increasing water temperature and thermal stratification. We assessed temporal changes in the abundance and biomass of the ichthyofauna in an isolate reservoir (inflowing waters from small tributaries in a highland region) aiming to associate changes with climate effects over three decades (1990, 2000, 2010). Two abundant native species, a loricariid Loricariichthys castaneus (Castelnau, 1855) and a cichlid Geophagus brasiliensis (Quoy & Gaimard, 1824), were selected to assess eventual response to climate changes in their geographical distribution in the Southeast Atlantic Hydrographic Region, considering different carbon emission scenarios using ecological niche models. A decrease in the densities and biomass of the ichthyofauna and of the two selected species were observed in both summer and winter over the three decades, coinciding with increases in temperatures. These decreases were correlated with increases in positive anomalies of temperature, which may be an indicator of climatic changes, although with low explanation of the data variation. The mean size of L. castaneus decreased between the nineties and 2010, whereas no significant trend was found for the size of G. brasiliensis. Our predictions of new area for future adequacy indicated a loss in the distribution area for both species (mainly for G. brasiliensis), considering the most pessimistic scenario for 2050 and 2070, possibly due to climatic changes. Both hydroelectric dams and global warming pose threats to freshwater fish diversity, and both will interact. Changes observed in the fish assemblage over the last decades were essential for an assessment of the consequences of global warming in this type of reservoir combining larger scale studies with future projections. 相似文献