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Miranda Lee Pao 《Information processing & management》1985,21(4):305-320
Instead of the commonly accepted inverse square law, Lotka's original formulation was based on a more general inverse power law: xn·y = c. The exponent and the constant must be estimated from the given set of author productivity data. A step-by-step outline is presented for testing the applicability of Lotka's law. Steps include the computation of the values of the exponent and the constant based on Lotka's method, and the test for significance of the observed frequency distribution against the estimated theoretical distribution derived from Lotka's formula. 相似文献
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We characterized yield-relevant characters and their variations over genotypes and environments (locations and years) by examining two rice varieties (9746 and Jinfeng) with high yield potential.9746 and Jinfeng were planted in two locations of Shanghai,China,during 2005 and 2006.The results show that there was a large variation in grain yield between locations and years.The realization of high yield potential for the two types of rice was closely related to the improved sink size,such as more panicles per square meter or grains per panicle.Stem and leaf biomasses were mainly accumulated from tillering stage to heading stage,and showed slow decline during grain filling.Meanwhile,some photosynthetic characters including net photosynthesis rate (Pn),leaf area index (LAI),specific leaf area (SLA),fluorescence parameter (maximum quantum yield of PSII,Fv/Fm),chlorophyll content (expressed as SPAD value),as well as nutrient (N,P,K) uptake were also measured to determine their variations over genotypes and environments and their relationships with grain yield.Although there were significant differences between years or locations for most measurements,SLA at tillering and heading stages,Fv/Fm and LAI at heading stage,stem biomass at heading and maturity stages,and leaf nitrogen concentration at tillering and heading stages remained little changed,indicating their pos-sible applications as selectable characters in breeding programs.It was also found that stem nitrogen accumulation at tillering stage is one of the most important and stable traits for high yield formation. 相似文献
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解析iSchools联盟发展现状与特色 总被引：1，自引：0，他引：1
从iSchools成员的分布、系所名称、博士班学程的特色,剖析iSchools成员的属性,以期能从中观察iSchools对资讯领域产生的影响。研究结果显示,目前iSchools 38个成员以美国为主,遍及欧、亚、澳各地,形成全球资讯学院联盟,有助于学术交流与合作。再者,其中有12个成员(占31.6%)来自ALA认可的学校,比例颇高,且其系所名称多单独使用资讯或资讯研究一词,传统的图书馆学系所在此已显式微。至于系所名称的表现,iSchools偏重资讯领域,有65.8%的系所名称以资讯一词起始、97.4%的系所名称涵盖资讯一词,显见资讯在此群组的主导性。最后,在人才培植方面,iSchools锁定资讯领域的高级学术、研究人才、企业界的高阶主管为目标,普设博士班学程,跨学科的课程以资讯为主体,强调科技应用。 相似文献
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Ishien Li Esther Onaga Pao‐Sheng Shen Hua‐Huei Chiou 《International Journal of Science Education》2013,35(9):1175-1185
Based on data collected from 211 elementary school children in central Taiwan over four years, the role of temperament in science achievement was examined with multivariate analysis of covariance (MANCOVA) with repeated measures design. The results revealed that the students’ science achievement is stable over time. The task orientation characteristics (i.e., distractibility, hyperactivity, and persistence) identified by previous research as important in mathematics and reading achievement are not consistent with the findings of this study that although the impacts of distractibility and persistence are significant, the simple effect of activity level on science achievement was not significant. However, the interaction effect of activity level and persistence is significant. Further break down analyses conducted to pursuit the interaction effect revealed that: (1) persistence has a consistent significant positive effects on all children over the years, except for the ones with high activity level (the upper 25th percentile); and (2) activity level has significant negative effects on high persistence (the upper 25th percentile) children only, and the interaction effect of activity level increases over time—the older the child the more significant the influence. Also, the tendency of approach/withdraw has significant impact on science achievement The educational implications of the findings include: (1) teachers of high activity students with high persistence may need to consider the match between children’s interests and contents of instruction; (2) a good match between children’s individual differences in distractibility, persistence, and approach need to be considered in contents, expectations, and interactions of the instruction. 相似文献
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周跑 《湖南广播电视大学学报》2009,(3):17-19
本文对广播电视大学题库及考试系统进行分析和设计,该系统由题库管理系统、考试系统和学生在线模拟考试系统组成,采用遗传算法作为组卷策略,能提供方便快捷的无纸化考试及信息服务。 相似文献
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美国律师协会自1921年制定了法律图书馆评估标准后就一直鲜有改革。随着电子与网络技术改变了信息环境,传统的评估标准已经不能科学地评价法律图书馆的质量。ABA顺应时代的变化。对法律图书馆的评估标准做了适当的改革,由最初的只承认藏书量转而同时承认电子信息渠道。 相似文献
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