全文获取类型
收费全文 | 5996篇 |
免费 | 289篇 |
国内免费 | 5篇 |
专业分类
林业 | 437篇 |
农学 | 234篇 |
基础科学 | 43篇 |
1233篇 | |
综合类 | 911篇 |
农作物 | 245篇 |
水产渔业 | 380篇 |
畜牧兽医 | 2205篇 |
园艺 | 187篇 |
植物保护 | 415篇 |
出版年
2023年 | 33篇 |
2022年 | 52篇 |
2021年 | 87篇 |
2020年 | 139篇 |
2019年 | 130篇 |
2018年 | 141篇 |
2017年 | 127篇 |
2016年 | 138篇 |
2015年 | 123篇 |
2014年 | 139篇 |
2013年 | 281篇 |
2012年 | 320篇 |
2011年 | 398篇 |
2010年 | 231篇 |
2009年 | 178篇 |
2008年 | 324篇 |
2007年 | 346篇 |
2006年 | 324篇 |
2005年 | 316篇 |
2004年 | 301篇 |
2003年 | 296篇 |
2002年 | 278篇 |
2001年 | 84篇 |
2000年 | 81篇 |
1999年 | 98篇 |
1998年 | 65篇 |
1997年 | 62篇 |
1996年 | 55篇 |
1995年 | 52篇 |
1994年 | 54篇 |
1993年 | 54篇 |
1992年 | 49篇 |
1991年 | 53篇 |
1990年 | 55篇 |
1989年 | 46篇 |
1988年 | 43篇 |
1987年 | 44篇 |
1986年 | 56篇 |
1985年 | 36篇 |
1984年 | 45篇 |
1983年 | 38篇 |
1982年 | 40篇 |
1981年 | 28篇 |
1980年 | 21篇 |
1979年 | 25篇 |
1978年 | 34篇 |
1977年 | 32篇 |
1975年 | 30篇 |
1973年 | 33篇 |
1972年 | 21篇 |
排序方式: 共有6290条查询结果,搜索用时 712 毫秒
951.
Thomas H. Galley Frederico M. Batista Richard Braithwaite Jon King Andy R. Beaumont 《Aquaculture International》2010,18(3):315-325
The blue mussel Mytilus
edulis is a commercially important species whose fishery and culture generally relies on natural spat collection. Hatchery-production
could provide an alternative source of seed, enabling reliable expansion of the industry. Mussel spawning and larval rearing
trials were carried out to optimise elements of hatchery production. Culturing fertilised eggs at low density (20–200 eggs cm−2) rather than high density (400–720 eggs cm−2) significantly improved the quality of first veliger larvae and differences in this improvement were evident between the
eggs from different females (maternal effects). Veliger larval growth at 17 or 21°C was significantly faster than growth at
14°C. Feeding veliger larvae an identical total ration either daily or at 2–3 day intervals did not significantly affect their
growth. Different microalgal diets (1: Isochrysis sp. (clone T-ISO), 2: Chaetoceros
calcitrans forma pumilus, 3: C. muelleri, 4: mixed Isochrysis sp. (clone T-ISO) and C. calcitrans f. pumilus, and 5: mixed Isochrysis sp. (clone T-ISO) and C. muelleri) were tested on veliger larval growth and mixed diets outperformed single-species diets. 相似文献
952.
Peter S. Ross Sarah Z. Dungan Samuel K. Hung Thomas A. Jefferson Christina Macfarquhar William F. Perrin Kimberly N. Riehl Elisabeth Slooten John Tsai John Y. Wang Bradley N. White Bernd Würsig Shih Chu Yang Randall R. Reeves 《水产资源保护:海洋与淡水生态系统》2010,20(6):685-694
- 1. Numbering no more than 100 individuals and facing many threats, the geographically isolated Eastern Taiwan Strait population of Indo‐Pacific humpback dolphins (Sousa chinensis) is in peril. The estuarine and coastal waters of central‐western Taiwan have historically provided prime habitat for these dolphins, but environmental conditions today bear little resemblance to what they were in the past.
- 2. The humpback dolphins must share their habitat with thousands of fishing vessels and numerous factories built upon thousands of hectares of reclaimed land.
- 3. They are exposed to chemicals and sewage released from adjacent terrestrial activities. Noise and disturbance associated with construction, vessel traffic and military activities are features of everyday life for these animals.
- 4. Measures to slow the pace of habitat deterioration and reduce the many risks to the dolphins are urgently needed. As one practical step in this direction, this paper describes the habitat needs of these small cetaceans so that decision makers will be better equipped to define ‘priority habitat’ and implement much needed protection measures under the terms of local legislation.
- 5. The preferred habitat of these dolphins in Taiwan consists of shallow (<30 m), near‐shore marine waters with regular freshwater inputs.
- 6. For such a small, isolated and threatened population, ‘priority habitat’ should not be limited to areas of particularly intensive dolphin use or high dolphin density, but rather it should encompass the entire area where the animals have been observed (their current ‘habitat’), as well as additional coastal areas with similar bio‐physical features (‘suitable habitat’). Such a precautionary approach is warranted because the loss of only a few individuals could have serious population‐level consequences.
- 7. While conventional socio‐economic analysis might suggest that implementing protection measures over an area stretching ~350 km north–south along Taiwan's west coast and ~3 km out to sea would be too ‘costly’, the loss of this charismatic species from Taiwan's waters would send a troubling message regarding our collective ability to reconcile human activities with environmental sustainability. Copyright © 2010 John Wiley & Sons, Ltd.
953.
Thomas M. Detmer Kyle J. Broadway Joseph J. Parkos Matthew J. Diana David H. Wahl 《Fisheries Management and Ecology》2020,27(5):540-543
Tournament fishing has risen in popularity over the last half a century. As such, social and financial incentives combined with technological advancements are expected to drive changes in angler's capacity to exploit tournament‐eligible fish stocks, as has been observed in commercial fisheries. The aim of this study was to quantify temporal trends in angler efficiency and their ability to exploit a given fish stock relative to effort in largemouth bass fishing tournaments. A collective analysis across seven Illinois reservoirs comparing change through time in angler catch rates and relative population abundances indicated that angler efficiency has generally improved through time. For the decade from 2005 to 2015, a greater than threefold increase in the efficiency of anglers to exploit a static population of largemouth bass was estimated. Anglers have become more efficient at exploiting populations, which is likely to influence management decisions in the future, particularly in harvest‐orientated fisheries and those reliant upon fishery‐dependent surveys. 相似文献
954.
Maj Wetjen Thomas Schmidt Anne Schrimpf Ralf Schulz 《Fisheries Management and Ecology》2020,27(2):170-184
The genetic structure of the gadiform fish species, burbot Lota lota L., was investigated across Germany to derive management options for facilitating the preservation of genetic diversity. Sequence analysis of the mitochondrial control region (n = 244) and microsatellite analysis (n = 861) of specimens from 20 sites revealed genetic structuring between major river basins, and particularly between lake and river habitats. The admixture zone between the Eurasian and West European phylogenetic clades in Lake Constance was confirmed and expanded to include the drainage basins of the rivers Rhine and Schlei/Trave. Haplotype distribution and private haplotypes in single river basins indicated population differentiation and imply that German burbot constituted an important part of the entire species' diversity. The derived genetic structuring has implications for future stocking programmes and the preservation of the adaptive potential of burbot, a guiding species for oligotrophic lakes in Europe. 相似文献
955.
Alexander G. Kramer Boris Gomelsky Jeffrey L. Warner Noel D. Novelo Brandylyn L. Thomas 《Aquaculture Research》2020,51(7):2824-2830
The purpose of this study was to investigate reproductive ability of backcross triploid koi (Cyprinus carpio L.) × goldfish (Carassius auratus L.) hybrids. These triploids have been obtained by crossing of F1 hybrid females producing diploid eggs with males of parental species. Triploid hybrid females, when crossed with goldfish or koi males, produced mostly aneuploid fish with ploidy range from approximately 2.2n–3.2n with a mean value 2.5n; some fish in crosses of triploid females with koi males were tetraploid (4.0n). Since analysed fish had in their genomes one haploid set from parental males, the data indicate that triploid hybrid females mostly produced aneuploid eggs with ploidy range from approximately 1.2n–2.2n and a mean ploidy around 1.5n while some eggs were triploid. Triploid hybrid males were completely sterile and have not released any sperm after hormonal injection. Despite their low viability, some aneuploid fish obtained from triploid hybrid females were raised in indoor recirculating systems until the age of 2 years and their reproductive ability has been evaluated. One aneuploid female with ploidy 2.1n produced larvae with ploidy range from 2.9n to 3.4n with a mean ploidy of 3.1n when crossed with a koi male; about 60% of obtained larvae had ploidy from 3.0n to 3.2n. These data indicate that this female produced mostly eggs with unreduced ploidy level. 相似文献
956.
Jie Ma Timothy J. Bruce Ponnerassery S. Sudheesh Christopher Knupp Thomas P. Loch Mohamed Faisal Kenneth D. Cain 《Journal of fish diseases》2019,42(1):75-84
Bacterial coldwater disease, caused by Flavobacterium psychrophilum, remains one of the most significant bacterial diseases of salmonids worldwide. A previously developed and reported live‐attenuated immersion vaccine (F. psychrophilum; B.17‐ILM) has been shown to confer significant protection to salmonids. To further characterize this vaccine, a series of experiments were carried out to determine the cross‐protective efficacy of this B.17‐ILM vaccine against 9 F. psychrophilum isolates (representing seven sequence types/three clonal complexes as determined by multilocus sequence typing) in comparison with a wild‐type virulent strain, CSF‐259‐93. To assess protection, 28‐day experimental challenges of rainbow trout (Oncorhynchus mykiss) fry were conducted following immersion vaccinations with the B.17‐ILM vaccine. F. psychrophilum strains used in challenge trials were isolated from several fish species across the globe; however, all were found to be virulent in rainbow trout. The B.17‐ILM vaccine provided significant protection against all strains, with relative percent survival values ranging from 51% to 72%. All vaccinated fish developed an adaptive immune response (as measured by F. psychrophilum‐specific antibodies) that increased out to the time of challenge (8 weeks postimmunization). Previous studies have confirmed that antibody plays an important role in protection against F. psychrophilum challenge; therefore, specific antibodies to the B.17‐ILM vaccine strain appear to contribute to the cross‐protection observed to heterologous strain. The ability of such antibodies to bind to similar antigenic regions for all strains was confirmed by western blot analyses. Results presented here support the practical application of this live‐attenuated vaccine, and suggest that it will be efficacious even in aquaculture operations affected by diverse strains of F. psychrophilum. 相似文献
957.
Jessica J. Buss Kathryn H. Wiltshire Thomas A. A. Prowse James O. Harris Marty R. Deveney 《Journal of fish diseases》2019,42(1):63-74
Bonamia spp. parasites threaten flat oyster (Ostrea spp.) farming worldwide. Understanding test performance is important for designing surveillance and interpreting diagnostic results. Following a pilot survey which found low Bonamia sp. intensity in farmed Ostrea angasi, we tested further oysters (n = 100–150) from each of three farms for Bonamia sp. using heart smear, histology and qPCR. We used a Bayesian Latent Class Model to assess diagnostic sensitivity (DSe) and specificity (DSp) of these tests individually or in combination, and to assess prevalence. Histology was the best individual test (DSe 0.76, DSp 0.93) compared to quantitative polymerase chain reaction (qPCR) (DSe 0.69, DSp 0.93) and heart smear (DSe 0.61, DSp 0.60). Histology combined with qPCR and defining a positive from either test as an infected case maximized test performance (DSe 0.91, DSp 0.88). Prevalence was higher at two farms in a high‐density oyster growing region than at a farm cultivating oysters at lower density. Parasite intensities were lower than in New Zealand and European studies, and this is probably contributed to differences in the performance of test when compared to other studies. Understanding diagnostic test performance in different populations can support the development of improved Bonamia surveillance programs. 相似文献
958.
959.
960.
Annie J Krueger Kathryn Hanford Thomas J Weissling Ana M Vlez Troy D Anderson 《Journal of insect science (Online)》2021,21(2)
Insecticide exposure has been identified as a contributing stressor to the decline in the North American monarch butterfly Danaus plexippus L. (Lepidoptera: Nymphalidae) population. Monarch toxicity data are currently limited and available data focuses on lethal endpoints. This study examined the 72-h toxicity of two pyrethroid insecticides, bifenthrin and β-cyfluthrin, and their effects on growth and diet consumption. The toxicity of bifenthrin to caterpillars was lower than β-cyfluthrin after 72 h. Survival was the most sensitive endpoint for bifenthrin, but diet consumption and caterpillar growth were significantly reduced at sublethal levels of β-cyfluthrin. Using AgDRIFT spray drift assessment, the aerial application of bifenthrin or β-cyfluthrin is predicted to pose the greatest risk to fifth-instar caterpillars, with lethal insecticide deposition up to 28 m for bifenthrin and up to 23 m for β-cyfluthrin from treated edges of fields. Low boom ground applications are predicted to reduce distances of lethal insecticide exposure to 2 m from the treated field edge for bifenthrin and β-cyfluthrin. Growth and survival of fifth-instar monarch caterpillars developing within the margins of a treated field may be significantly impacted following foliar applications of bifenthrin or β-cyfluthrin. These findings provide evidence that pyrethroid insecticides commonly used for soybean pest control are a potential risk to monarch caterpillars in agricultural landscapes. 相似文献