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71.
Spatial and temporal feed distribution in sea cages are important factors for the farmer, fish and environment due to the strong relation to growth, feed loss, pollution and welfare. This study presents a set of experimentally derived diffusion parameters and settling rates obtained in still water from four sizes and three densities of extruded fish feed pellets commonly used in aquaculture. It was found that pellet size is positively correlated with increased diffusion and that pellet density plays a less important role. Both the size and density of pellets had a significant impact on the settling rate. Results are compared to values obtained during feed production as well as other relevant studies. The findings suggest that parameters related to hydrodynamic behaviour of groups of feed pellets may vary across different pellet types. The results may be applied to refine and parameterize pellet motion in sea cage feeding models, improving estimates of fish behaviour, growth and feed loss. 相似文献
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73.
Many fish rearing infrastructures are already equipped with human-operated camera systems for fish behavior monitoring, e.g. for stopping the feeding system when the fish is satiated or for monitoring of fish behavior abnormalities caused by poor water quality or diseases. The novel infrared reflection (IREF) system for indoor 3D tracking of fish demonstrated in the current study allows for automation of fish behavior monitoring, reducing the system running costs by eliminating the need for continuous human monitoring and increasing the behavioral analysis accuracy by excluding the human subjectivity factor.The operating principle of this system is based on the effect of strong absorption of near infrared (NIR) range light by water, thus allowing estimation of fish distance based on the corresponding fish object brightness on the camera image. The use of NIR illuminator as a part of the IREF system allows fish behavior monitoring in the dark so as not to affect fish circadian rhythm. A system evaluation under aquaculture facility conditions with Atlantic salmon (Salmo salar) using flow-through water in tanks, showed the mean depth estimation error was equal to 5.3 ± 4.0 (SD) cm. The physiological variations among conspecific individual fish introduced the mean depth estimation error of 1.6 ± 1.3 (SD) cm. The advantages of the IREF system over well-known stereo vision systems are lower hardware cost and less computationally intensive 3D coordinates estimation algorithm, while the disadvantage is lower accuracy that is nevertheless acceptable for most applications of aquaculture fish monitoring. 相似文献
74.
The agricultural world today is dominated by a few domesticated mammal species, that is, animals modified from their wild ancestors through selective breeding in captivity for traits beneficial to human usages. As a result, a clear dichotomy exists between wild (from hunting) and domesticated mammals (produced in farms) used for human consumption. Similar to agriculture, aquaculture is often viewed as the only solution that can provide more fish products given that harvesting wild stocks have reached an upper limit. Aquaculture is considerably younger than agriculture relying on natural sources to farm numerous species. To better describe the diverse strategies for fish production, we propose a new classification comprising five levels of ‘domestication’ with 1 being the least to 5 being the most domesticated. Our classification places 70% of the 250 farmed finfish species recorded in the 2009 FAO database into levels 1, 2 and 3 representing a transitory form of fish production dependent on the availability of the wild resource. In contrast, only a few species, or more accurately populations, can be considered truly domesticated, similar to cattle or sheep. Based on this classification, two scenarios for the future of aquaculture are discussed: either the industry focuses on few truly domesticated species, similar to the path taken by agriculture, but avoiding its negative impacts or aquaculture proceeds with inter‐specific diversification by focusing primarily on the domestication of native species. 相似文献
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Robin K. King Stephen A. Smith Merle D. Pierson Gregory D. Boardman Charles W. Coale Jr. 《Journal Of Applied Aquaculture》2013,25(2):79-92
ABSTRACT Pathogenic microorganisms may be incorporated into biofilms found in aquaculture systems, causing recurring exposure to potential disease agents. Aerobic plate counts, the presence of Enterobacteriaceae, and the presence of Escherichia coli, modified to express a green fluorescent protein (GFP E. coli), was used to evaluate the effectiveness of various sanitizers in decreasing bacterial incorporation into newly generated biofilms in recirculating aquaculture systems. Disks of Buna-N rubber, polyvinyl chloride (PVC), chlorinated PVC, glass, fiberglass, and stainless steel were placed in aquariums stocked with Nile tilapia, Oreochromis niloticus. The effectiveness of water, an alkaline cleanser, sodium hypochlorite, a quaternary ammonium compound, or peracetic acid as a sanitizer was evaluated on each substrate by enumerating total plate counts, GFP E. coli, and Enterobacteriaceae. Sodium hypochlorite and peracetic acid were the most effective sanitizers, with an overall percentage reduction of GFP E. coli of approximately 2 logs10. The quaternary ammonium compound was moderately effective, 1 log10, against the target organisms. Water demonstrated a 2 log10 reduction of the total plate count, suggesting that some mechanical cleaning was achieved. The type of material used as substrate for the biofilm had no significant (P?>?0.05) effect on the effectiveness of the sanitizers. 相似文献
77.
Frank A. Chapman Lury N. García Victor J. Atencio Robin J. Muñoz Alfonso Silva Héctor Flores 《Journal Of Applied Aquaculture》2013,25(2):179-186
The ability of marine goliath grouper to survive in waters of low salinity was investigated by collecting juvenile individuals from the wild in full-strength seawater and either transferring them directly to fresh water or acclimating them over a 96-h period to fresh water. Juvenile goliath grouper (n = 49; mean 23.4 cm SL; SD 4.1; mean 339.1 g; SD 89.3) tolerated transfers from seawater (30 ppt) to freshwater (<1 ppt), and survived thereafter for a period of 28 d in strictly fresh water, with no observed adverse effects. However, the salinity tolerance was influenced by rate of exposure, as no deaths were observed when the fish were given a gradual decrease in salinity, but 60% of the individuals died when transferred abruptly from seawater into fresh water. 相似文献
78.
Aoi Sugimoto Maria Lourdes San Diego-McGlone Francisco Paciencia Shielameh P. Milan Elizabeth T. Tomas Carolina C. Ramírez 《Journal Of Applied Aquaculture》2013,25(4):298-313
ABSTRACTThis study examined if, and how, comanagement is effective in controlling aquaculture industry in the municipalities of Anda and Bolinao in the province of Pangasinan, in the Philippines, the locations of two major production areas of milkfish (Chanos chanos) in the country. Institutional and community analyses conducted in these study sites revealed a unique hierarchy of resource users, as well as unique social and economic problems in aquaculture, distinct from those of capture fishery. It was also indicated that comanagement is seen as a solution for essential practices to be enforced practically and sustainably for the management of this industry. To improve aquaculture governance, it is desired that the comanagement scheme shall include not only the governments and fishers but also business operators who often have large capital and a high degree of power. 相似文献
79.
Giannis Karagiannis Stelios D. Katranidis Vangelis Tzouvelekas 《Aquaculture Economics & Management (Blackwell Science)》2013,17(3-4):191-207
Abstract A stochastic Cobb‐Douglas production frontier is used to provide estimates of output‐oriented technical efficiency, input‐oriented technical efficiency, input allocative efficiency and cost efficiency for a sample of seabass and seabream farms in Greece. Mean output‐oriented technical efficiency is estimated at 78.5%, input‐oriented technical efficiency at 73.6%, input allocative efficiency at 79.2%, and cost efficiency at 58.2%. Considering the sources of efficiency differentials among fish farms, it is evidence from the empirical results that large farms tend to achieve higher (technical and allocative) efficiency scores; specialization in either seabass or seabream affects positively technical and cost, but not allocative, efficiency; and utilization of skilled labor seems to have a positive impact only on technical efficiency. 相似文献
80.