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EGTA—EDTA直接滴定法测定水泥中的氧化镁 总被引：1，自引：0，他引：1
根据水泥的化学组成,利用ＥＧＴＡ与Ｃａ＾２＋、Ｍｇ＾２＋配位能力相差较大的特性提出了ＥＧＴＡ作为Ｃａ＾２＋的掩蔽剂,ＥＤＴＡ直接滴定镁的方法并讨论了Ｆｅ＾３＋、Ａｌ＾３＋、Ｔｉ＾４＋、Ｍｕ＾２＋等离子的干扰及消除。 相似文献
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氨基酸清除活性氧自由基作用的研究 总被引：22，自引：0，他引：22
分别采用Ｘ－ＸＯＤ－Ｌｕｍｉｎｏｌ的Ｏ２＾－产生模型和Ｖｃ－Ｃｕ＾２＋－Ｈ２Ｏ２－酵母多糖的ＯＨ产生体系，以还原型谷胱甙肽（ＧＳＨ）作为参照，用化学发光法研究了１９在酸对活性氧自由基的清除能力，证实了氨基酸普遍具有生物抗氧化活性，其抗Ｏ２＾－的有效浓度范围在１０＾－２￣１０＾－４ｍｏｌ／Ｌ，比ＧＳＨ高出二个数量级。 相似文献
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有关DEA有效性用于预测的探讨 总被引：3，自引：5，他引：3
有关ＤＥＡ有效性用于预测的探讨吴文江（武汉工业大学北京研究生部１０００２４）１引言对有多输入与多输出的问题，文献［１］提出了一种用数据包络分析（ＤＥＡ）进行预测的方法，本文提供了用ＤＥＡ有效性（Ｃ２ＧＩ２）进行预测的另一种较简单的方法。在单输入与单输... 相似文献
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同步辐射对直肠癌组织微量元素测定的意义探讨 总被引：2，自引：0，他引：2
采用同步辐射荧光分析光谱法（ＳＲＸＦＳ）对９例直肠癌及癌旁移行粘膜和正常粘膜中微量元素的含量进行分析，结果显示，癌组织中Ｃｕ、Ｚｎ、Ｍｎ三种微量元素相对含量分别为３８１９９．１６、１５５５７．０４和２０９．８６，显著低于正常粘膜组织（Ｐ＜０．０５，或Ｐ＜０．００１）；而宏量元素Ｃｌ含量为３４３８．１６，显著高于正常粘膜（Ｐ＜０．０５）。癌旁移行粘膜中Ｃｕ、Ｚｎ、Ｍｎ、Ｃｌ、Ｔｉ、Ｓｅ元素含量介于癌组织和正常粘膜之间，作者认为，微量元素Ｃｕ、Ｚｎ、Ｍｎ可能是直肠癌的相关性元素，癌旁移行粘膜多种元素含量变化趋势，提示癌旁移行粘膜可能是一类潜在性交界性瘤变。 相似文献
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对非完整力学系统存在守恒量的数目进行了研究，研究表明，若力系统具有ｎ个广义坐标且受有ｇ个非完整约束，则此系统存在（２ｎ－ｇ）个函数独立的守恒量。文未讨论了Ａｐｐｅｌｌ０Ｈａｍｅｌ模型，并给出了它的一个新的守恒量。 相似文献
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睾丸间质细胞胰岛素样生长因子－Ⅰ基因表达的调控 总被引：1，自引：0，他引：1
评估了联岛素样生长因子－Ⅰ（ＩＧＦ－Ｉ）ｍＲＮＡ在大鼠睾丸Ｌｅｙｄｉｇ细胞中的基因表达。用１５％～６０％Ｐｅｒｃｏｌｌ液密度梯度离心，可将原始的间质细胞分成不同的３条带。ＩＧＦＩ．ｍＲＮＡ主要位于Ｌｅｙｄｉｇ细胞丰富组分（带３），带１和带２组分仅含少量ＩＧＦ－ＩｍＲＮＡ．Ｌｅｙｄｉｇ细胞ｍＲＮＡ具有碱基从０．８～７．５ｋｂ的多种型，在２５～５５日龄大鼠中均存在ＩＧＦ－ＩｍＲＮＡ。用Ｋｌｉｎｅｆｅｌｔｅｒ等方法高度纯化Ｌｅｙｅｉｇ细胞，发现大多数ＩＧＦ－ＩｍＲＮＡ位于这些Ｌｅｙｄｉｇ细胞，而在整个睾丸组织或其它间质细胞检测不到ＩＧＦ－ＩｍＲＮＡ。大鼠应用生长激素（ＧＨ）后，Ｌｅｙｄｉｇ细胞中ＩＧＦ－ＩｍＲＮＡ增加２倍以上，提示Ｌｅｙｄｉｇ细胞中的ＩＧＦ－ＩｍＲＮＡ亦依赖ＧＨ．Ｌｅｙｄｉｇ细胞产生的间质ＩＧＦ－Ｉ在睾丸中可能具有自分泌和旁分泌作用。 相似文献
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巨磁电阻（ＧＭＲ）效应的应用,是一个从科学发现向应用快速转化的最新例子。ＧＭＲ效应是１９８８年由德国Ｇｒｕｎｂｅｒｇ和法国Ｆｅｒｔ两位科学家的研究组发现的。研究对象是多层薄膜结构：Ｆｅ／Ｃｒ／Ｆｅ三层结构或［Ｆｅ／Ｃｒ］ｎ超晶格（ｎ为周期数）。用分子束外延（ＭＢＥ）方法制备。在外磁场作用下,这种多层结构薄膜的电阻值变化率可达５０％以上,故称为巨磁电阻效应。一年多后,ＩＢＭ公司的Ｐａｒｋｉｎ／小组用磁控溅射法代替昂贵的分子束外延方法制备多层膜,意外发现铁磁层之间的磁矩取向度随中介非磁性层厚度呈振荡… 相似文献
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为了探讨专科病房对急性脑梗塞,脑出血的内科治疗新法,我们筛选了脑神经生长素（简称ＣＮＧ）治疗脑梗塞患者１６例,均经本院头颅ＣＴ扫描确诊３２例脑梗塞病人,并设立治疗组（ｎ＝１６）采用ＣＮＧ治疗。对照组（ｎ＝１６）采用脑活素与胞二磷胆碱治疗。治疗时间为２周。观察结果显示：ＣＮＧ治疗脑梗塞与脑出血,明显优于对照组（Ｐ〈０．０５）,并对Ｒｂｃ,ＨＧＢ,ＰＬＴ有调节作用,对机体影响负作用小,值得临床科室推广 相似文献
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城市规模分布的δ^n规律——Davis二倍数规律的理论推广,分形性质和实 … 总被引：3，自引：0，他引：3
将Ｄａｖｉｓ关于城市规模分布的二倍数规律推广到任意指数规律,证明了从２＾ｎ规律中推导出来的三参数Ｚｉｐｆ模型Ｐ（ｒ）＝Ｃ（ｒ－ａ）＾ｄｘ的幂指数ｄｚ具有分形维数（Ｄ）性质,且有Ｄ＝１／ｄｚ＝ｌｏδ／ｌｇ２。最后以河南省城市体系为实例验证了作者发展的理论。 相似文献
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Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
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A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
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Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
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《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
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《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
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Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
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Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
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Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
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Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
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Leah A. Lievrouw 《The Information Society》1998,14(2):83-96
The main premise of this article is that in information societies generally, and in virtual social contexts particularly, a distinctive style of interaction to facilitate the communication of difference, heterotopic communication , has emerged. It rests on two cultural foundations: an ideological belief in the positive, socially integrating power of communication, and a prevailing ethic of instrumental rationality, subjective individualism, and strategically practiced self-interest. The former is demonstrated by the use of simulation and spectacle as sources of information; exhibitionism/voyeurism as a communicative style; and the awareness of surveillance. The latter is seen in the competitive use of knowledge as a commodity; a surface globalism masking deep parochialism; lateral as well as vertical information inequity; and the use of public versus private as strategies for engagement rather than as spaces. Those who engage in heterotopic communication resort to their 'own devices' both in the sense of personal agendas, strategies, interests, and interpretations, and in the form of the telecommunication tools that help realize them. These personal and technological devices allow individuals with the right educational and technical resources to avoid exposure to disagreement, difference, or other information that does not serve their direct purposes or reflect their particular views of the world; yet they also help convey the appearance of openness, availability, and cooperation. This style of interaction is used strategically in combination with information and communication technologies to gain social or economic advantages, but it may encourage social separatism and parochialism, inhibit the negotiation of disputes, and emphasize competing interests. 相似文献