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131.
132.
J.Miller McPherson 《Social science research》1976,5(2):95-105
This paper attempts to show that the “Theory Trimming” technique makes little contribution to theory in sociology. A brief history of the technique is given, and several key assertions of its proponents are abstracted. These assertions are shown to be highly questionable. The general alternative to Theory Trimming is shown, and the relationship between Theory Trimming and more general orientations to research is discussed. 相似文献
133.
Robert M. Groves 《Social science research》1978,7(3):257-271
Concurrently administered personal and telephone surveys are compared to measure differences between the modes for identical questions. Speed of questioning is found to be greater in telephone interviews than personal interviews. The faster pace of telephone interviews is linked to shorter answers to open-ended items on the telephone. The tendency to reduce such responses is disproportionately exhibited by younger, affluent respondents who tend to provide detailed responses in personal interviews. 相似文献
134.
Research on sex differences in occupational attainment suggests that working men and working women attain essentially the same mean level of occupational attainment and do so through quite similar processes. A possible explanation for these similarities is that the sample of working women contains an overrepresentation of successful women, since women who can afford not to work will stay out of the labor force unless they find a job commensurate with their education. This we define as a censoring problem. By extending a technique developed by Heckman, we can estimate the structural parameters for all women, regardless of current employment status. This procedure allows us to assess the impact of the censoring problem on women's occupational attainment equations. 相似文献
135.
Rein Taagepera 《Social science research》1978,7(2):180-196
Area changes of about 30 best known empires and states are compiled and tabulated. Superimposed and juxtaposed graphs (size versus time) help to visualize the relative size and location in time of these empires. Size-time integral, maximum stable size, adulthood date, and duration are defined operationally and are listed for 20 empires. A criterion is given for distinctness of successive empires. The size-time integral is a direct measure of an empire's impact on history insofar as that impact depends on sheer size and duration. The integral is largest for the Chinese Hsia-Shang, Egyptian New, Old, and Middle, Assyrian New, and Hittite empires. A world-wide territorial concentration index is tabulated. It increases during the period considered from 0.08 to 1.4% of the world dry land area. 相似文献
136.
通过对有丝分裂中期及减数分裂终变期染色体数目统计,形态、行为的观察,发现莱麦草染色体呈现广泛的变异:有丝分裂中期株内染色体数目在2n=11──56内变化,含有本物种染色体数目2n=28的细胞仅占统计数的27.8%。减数分裂终变期出现36%具非整倍性的花粉母细胞,染色体数除数目变异外还有结构变异如Robertson易位等。本文对该种进行了染色体组分析,确认其为同源四倍体。同时对该物种株内产生混倍性的原因,在物种进化上的意义进行了探讨。 相似文献
137.
Nils Chr Stenseth Ottar N. Bj?rnstad Takashi Saitoh 《Researches on Population Ecology》1998,40(1):85-95
We interpret gradients in population dynamics of the gray-sided vole from the southwestern part of the island of Hokkaido
to its northeastern part within the framework of a phenomenological model involving the relative length of summer and winter.
In Hokkaido, as in other northern regions, both spring and fall is considered as short transition periods between the two
main seasons — summer (the primary breeding season) and winter (the non-reproductive or secondary breeding season). We show
that the geographic transition in dynamics may be understood as the combined consequence of different patterns of density-dependence
during summer and winter, and geographically varying season lengths. Differences are shown to exist between summer and winter
with respect to strength of density-dependence. Direct density-dependence, in particular, is stronger during winter than during
summer. A model is presented to show how relative lengths of seasons can induce both stable and periodically fluctuating population
dynamics. The results are compared and contrasted with what is otherwise known about the gradient in rodent dynamics in Fennoscandia. 相似文献
138.
《本草纲目》中的不少“本草”是从西方的伊斯兰诸国传入中国的,伊斯兰民族的医学典籍中的例举及其诠释足可证明这个事实。 相似文献
139.
李猛 《南京工业大学学报(社会科学版)》2006,5(3):69-73
运用企业自主创新能力的评价指标体系,对南京市自主创新能力水平进行纵向和横向比较,可以比较好地把握其自主创新能力的现状。通过对南京市近四年自主创新能力指标的纵向比较,不难发现除了自主创新环境之外,南京市的自主创新资源、自主创新活动以及自主创新产出能力均有较大幅度的增长;通过将南京市与三大科技竞争力较强的城市自主创新能力指标进行横向比较,指出了南京市在自主创新能力上存在的突出问题。一是工业增加值率过低,二是研发经费过低。并在此基础上提出一系列对策和建议。对于提高南京自主创新能力水平,无疑具有重大的理论意义和现实意义。 相似文献
140.