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数字参考服务:发展与思考 总被引：100，自引：2，他引：98
数字参考服务是网络环境下参考服务发展的一种新形式。本文探讨了数字参考服务的深刻内涵,阐述了它的起源、服务模式、工作机制、应用领域以及最新发展趋势。在此基础上,根据我国数字参考服务发展的现状,提出了我国图书馆开展数字参考服务应考虑的主要问题。 相似文献
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The objectives of this study were to assess the potential of two photosynthetic bacteria （PSB）, Rhodopseudomonas palustris HZ0301 and Rhodobacter sphaeroides HZ0302, as probiotics in aquaculture. The viability of HZ0301 and HZ0302 in simulated gastric transit conditions （pH 2.0, pH 3.0 and pH 4.0 gastric juices） and in simulated small intestinal transit conditions （pH 8.0, with or without 0.3% bile salts） was tested. The effects of HZ0301 and HZ0302 on the viability and permeability of intestinal epithelial cell in primary culture of tilapias, Oreochrornis nilotica, were also detected. All the treatments were deter- mined with three replicates. The simulated gastric transit tolerance of HZ0301 and HZ0302 strains was pH-dependent and correspondingly showed lower viability at pH 2.0 after 180 min compared with pH 3.0 and pH 4.0. Both HZ0301 and HZ0302 were tolerant to simulated small intestine transit with or without bile salts in our research. Moreover, there was no significant difference （P〉0.05） among three treatments including the control and the groups treated with HZ0301 or HZ0302 both in intestinal epithelial cell viability and membrane permeability, showing no cell damage. In summary, this study demonstrated that HZ0301 and HZ0302 had high capacity of upper gastrointestinal transit tolerance and were relatively safe for intestinal epithelial cells of tilapias. 相似文献
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In order to overcome the defects of chemical hydrolysis approach to prepare glucosamine, an enzymatic hydrolysis method was developed. 相似文献5.
May 18, 2001 was memorable for Kunqu Opera, for on that day, the United Nations officially declared that Kunqu Opera, an age-old Chinese theatrical art, is a World Cultural Heritage. It was also a memorable day for Mr. Huang Yuan (1906-2003), who put the ancient opera back on a rejuvenation journey in 1955.Kunqu Opera germinated before China's Ming Dynasty (1368-1644). A sister play to Beijing Opera, Kunqu is distinctive for its poetic and refined dialogues and there are rarely warrior roles or acrobatic performances. Popular mainly in an area in Jiangsu and Zhejiang Provinces for a long time, Kunqu Opera was also highly appreciated by the royal or wealthy families. In 1955, after decades of wars in China, Kunqu Opera needed some boosting to get back to its popularity again. It was at this time that Huang Yuan came to work in Zhejiang from Shanghai. One evening, Huang Yuan watched a Kunqu Opera play in Hangzhou staged by Guofeng Kunqu Opera 相似文献
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信息用户研究是信息管理学研究领域中的重要组成部分。现从讨论热点．时代特征和研究趋势3方面对信息用户研究进行分析与探讨。 相似文献
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Objective： Study blood vessel injury and gene expression indicating vascular endothelial cell apoptosis induced by mannitol with and without administration of anti-oxidative vitamins. Methods： Healthy rabbits were randomly divided into four groups. Mannitol was injected into the vein of the rabbit ear in each animal. Pre-treatment prior to mannitol injection was per- formed with normal saline （group B）, vitamin C （group C） and vitamin E （group D）. Blood vessel injury was assessed under electron and light microscopy. In a second experiment, cell culture specimen of human umbilical vein endothelial cells were treated with mannitol. Pre-treatment was done with normal saline （sample B）, vitamin C （sample C） and vitamin E （sample D）. Total RNA was extracted with the original single step procedure, followed by hybridisation and analysis of gene expression. Results： In the animal experiment, serious blood vessel injury was seen in group A and group B. Group D showed light injury only, and normal tissue without pathological changes was seen in group C. Of all 330 apoptosis-related genes analysed in human cell culture specimen, no significant difference was seen after pre-treatment with normal saline, compared with the gene chip without pre-treatment. On the gene chip pre-treated with vitamin C, 45 apoptosis genes were down-regulated and 34 anti-apoptosis genes were up-regulated. Pre-treatment with vitamin E resulted in the down-regulation of 3 apoptosis genes. Conclusion： Vitamin C can protect vascular endothelial cells from mannitol-induced injury. 相似文献
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美国著名组织行为学大师和领导力大师保罗·赫塞在经典著作《组织行为学》一书中全面阐述了著名的情境领导模式,并且首次提出"执行力就是领导力"的命题。保罗·赫塞认为,领导力不是一种操纵,领导力更多的是对一个人行为的影响,从而使得领导机构和整个组织取得利益。"一个好校长就是一所好学校",校长在学校发展中的重要性可见一斑,自然也对其领导力提出了很高的要求。其实,在学校的发展进程中校长的领导力无所不在, 相似文献