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61.
Histomorphological studies of the perinatal pig: comparison of five mortality groups with unaffected pigs 总被引:1,自引:0,他引:1
The results of a histological examination of organs obtained from 5 clinically and morphologically identified and described mortality groups of pigs dying during the perinatal period (0–60 h of age) were compared with the results obtained from the same examination of unaffected, apparently normal pigs (0.4–60 h of age). The histomorphological pictures were judged blind according to a scale of 1 to 4, where 1 = none or insignificant, and 4 = a high degree of a specific organ characteristic. The results for each organ characteristic were analysed statistically. 相似文献
62.
K.Noel Masihi Hans Werner Werner Lange 《Comparative immunology, microbiology and infectious diseases》1984,7(2):125-130
Studies were carried out to determine the fate of virulent Toxoplasma gondii challenge in immune animals. Toxoplasma strains isolated from human, swine, rabbit and cat hosts were used for the primary immunization of mice. Brains were removed at various intervals after the challenge and subinoculated into normal mice. Prior immunization with one of the nine toxoplasma strains enabled the mice either to eliminate or harbour the challenge organisms without loss of virulence. The outcome of challenge infection was dependent on the parasite strain used for the immunization and the time interval between challenge and subinoculation. Mice immunized with strain KSU isolated from a cat eliminated repeatedly administered challenge from 80% of animals. Strain S 162 isolated from a swine eliminated similar challenge from only 20% of animals. The results indicate that the extent of protection against virulent T. gondii can vary widely and is related to the immunogenicity of the original immunizing strain. 相似文献
63.
本测定表明了叶中铁锰含量的增加或减少与土壤测定相一致。沙培和水培进一步证明了水溶性铁含量增高是致使根系衰弱和死亡的主要因素,也是抑制对锰吸收的主要因子;在通气差的条件下尤为严重。土壤含水率高,是卵菌纲(Oomycctcs)中兼性寄生菌对杉木根系侵柒的主要条件,由此加速了杉木的死亡。 相似文献
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66.
梨小食心虫是北方果树最严重的食心虫之一,为了探索和利用其天敌昆虫资源,选择山西省太谷地区具有代表性的2类样地,对其天敌资源进行了调查。研究发现,该地区的2种优势寄生性天敌种为舞毒蛾黑瘤姬蜂和亮黑伊乐寄蝇,该2种天敌室内羽化的高峰期多分布在0:00—13:00时段。在果树自然放养的A地,2种天敌并存,但以亮黑伊乐寄蝇为优势种。在人工管理频繁的B地,舞毒蛾黑瘤姬蜂为优势天敌种,亮黑伊乐寄蝇极少发生,并且天敌推迟发生。调查还发现,在梨小食心虫种群的盛发期,其数量变化和2种天敌的发生呈负相关,7月份后,2种天敌可对梨小食心虫形成明显的控制作用。 相似文献
67.
As kindergarten class decorate enhancement, to the requirement of the electrical design more and more is also high. This paper is based on the present of the more common kindergarten, respectively from the design and high voltage electricity design two aspects and so on many small point to electrical design in this paper. 相似文献
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69.
Peter B. Best 《African Zoology》2013,48(2):177-179
The catch per unit effort of Oreochromis mossambicus, Clarias gariepinus and Cyprinus carpio at different localities at Hartbeespoort Dam was investigated. Catches of the three species were between three and ten times higher on the southern shore of the lake than on the northern shore. The gradient of each locality was found to be the most important variable determining catch. Gill-net catches of O. mossambicus from littoral and limnetic stations indicated equal abundance of the species in these two habitats. The implications of the results for improved predictions of fish yield from lakes, and for management are discussed. 相似文献
70.
The diet of 745 Oreochromis mossambicus (Peters) of less than 0,5 up to 2000 g wet mass, in Hartbeespoort Dam, was determined from stomach content analysis. Samples of fish were selected to cover a whole annual cycle. Small fish fed initially on zoobenthos and zooplankton, but fish with a mass of over 4 g fed increasingly on Microcystis aeruginosa Kutzing and detritus until these food items formed the dominant food source in O. mossambicus over 8 g. Some cannibalism was encountered in fish up to 64 g in the summer months. The ratio of intestinal length to total length of fish ranged from 0,58 in the smaller fish to 11,02 in larger fish and this indicated that there was an ontogenetic adaptation from a carnivorous to a phytoplanktivorous/detritivorous diet. Feeding in juvenile fish studied over 24 h was found to be most intense in the early morning and late afternoon but remained high throughout daylight hours decreasing considerably at night. The daily ingestion rate of food in O. mossambicus in Hartbeespoort Dam was estimated at 453 mg/g of fish. This comprised 45% M. aeruginosa and 55% detritus. It was apparent that of this matter ingested only a small percentage would be assimilated. Oreochromis mossambicus shows feeding and breeding preadaptations which enable it to successfully exploit a lacustrine environment. These adaptations enable it to maintain a large population in Hartbeespoort Dam despite frequent winter mortalities caused by water temperatures below their tolerance limits. 相似文献