全文获取类型
收费全文 | 280篇 |
免费 | 18篇 |
国内免费 | 5篇 |
专业分类
林业 | 24篇 |
农学 | 13篇 |
51篇 | |
综合类 | 38篇 |
农作物 | 27篇 |
水产渔业 | 34篇 |
畜牧兽医 | 96篇 |
园艺 | 4篇 |
植物保护 | 16篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 4篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 17篇 |
2010年 | 12篇 |
2009年 | 12篇 |
2008年 | 18篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 7篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
1970年 | 4篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有303条查询结果,搜索用时 15 毫秒
71.
Selenium is essential for normal mammalian development. Being a component of antioxidant enzyme, glutathione peroxidase, it plays a major role in protecting the cells from free radical damage. The level of glutathione peroxidase was directly related to the amount of selenium present in various tissues and organs. A decrease in selenium leads to various pathological changes in humans as well as in various laboratory animals. The aim of the present study was to understand whether there is an increase in the level of selenium in different brain regions of rat pups whose mothers were supplemented with selenium, either 2 or 4 mg/l of their drinking water throughout the period of their pregnancy. There was a significant increase in the level of selenium in the cerebellum, cortex and hypothalamic and hippocampal tissues of selenium supplemented mothers as compared with those of non-supplemented mothers. The brain stem of these animals did not show any significant difference in the level of selenium. Furthermore, the differences in the level of selenium between the rat pups of 2 mg/l selenium supplemented mothers and 4 mg/l selenium supplemented mothers were not statistically significant. These studies suggest that supplementation of selenium to mothers during the period of their pregnancy can selectively increase the level of this trace element in different brain regions. Further studies are necessary to understand the significance of selective accumulation of selenium in specific brain regions on brain development and function. 相似文献
72.
Deletion of the M063 gene from myxoma virus produces a virus that is unable to replicate in rabbit cells in vitro or in live rabbits but can be propagated in non-rabbit cell lines. A targeted M063 deletion mutant was constructed in the attenuated Uriarra strain of myxoma virus and the ability of this virus to act as a safe, non-transmissible vaccine against myxomatosis was tested in outbred laboratory rabbits. Immunization with the M063 deletion vaccine provided good short-term protection against lethal challenge with virulent myxoma virus. Long-term protection was similar to reported results with heterologous live virus, with some rabbits protected but others succumbing to challenge. Replication-deficient poxvirus vaccines, like the Modified Vaccinia Virus Ankara (MVA) in man and the myxoma virus vaccine described here in rabbits, are very attractive from a safety perspective. Seasonal boosting would be predicted to provide long-term protection. Targeted host-range gene deletions could have potential for rapid development of poxvirus vaccines in general. 相似文献
73.
74.
75.
76.
77.
Panciera RJ Mathew JS Cummings CA Duffy JC Ewing SA Kocan AA 《Veterinary pathology》2001,38(4):422-426
American canine hepatozoonosis is caused by Hepatozoon americanum, a recently described species of apicomplexan protozoan parasite. An immunohistochemical procedure using a polyclonal antibody to sporozoites of H. americanum clearly identified asexual stages of H. americanum in canine striated muscle. The method also detects hepatozoa present in naturally infected coyotes and raccoons and reacts with certain other apicomplexans. Use of this immunohistochemical procedure confirms the canine intermediate host-parasite relationships that were presumptively established using conventional histopathologic methods. 相似文献
78.
This study examines the technical efficiency (TE) of aquaculture farms in Hawaii. Policy makers and industry participants interested in assessing the economic outlook of aquaculture production not only have to assess measures of profitability and financial health, but also measures of production efficiency. We estimate the TE of the state's aquafarms with a data envelopment analysis (DEA) model. Using data from the US Census of Agriculture, we examine TE measures of the population of Hawaii's aquafarms across different types of farms and over time. The results show that only 12% of the farms in 2007 may be classified as efficient, with a steady decline in efficiency over time. We find TE was related to the size of farm, full‐time farms were significantly more efficient than part‐time farms and that the average excess real inputs for land and labor have slightly fallen over time. The sub‐sector analysis revealed a strong variation of TE across different type of farms. With few farms operating on the frontier, the findings of this study suggest that the majority of the farms could improve their TE. 相似文献
79.
Biofilm formation is one of the factors responsible for antibiotic resistance. The involvement of biofilm formation in bacterial mastitis is well known. Milk composition varies during the lactation period and certain pathogens are producing more number of mastitis cases during particular periods of lactation. The present study elucidates the effects of different milk components on biofilm formation and the persistence of infection. The Plackett Burman screening design has been chosen for assessing the significance. Biofilm production of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were assessed by crystal violet assay. Dipotassium hydrogen phosphate had a significant effect on biofilm formation by S. aureus (MTCC 1430) whereas it was pH in the case of biofilm formation by P. aeruginosa (NCIM 5029). Other independent factors were found to be insignificant. 相似文献