首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   28篇
  免费   1篇
管理学   3篇
综合类   1篇
社会学   13篇
统计学   12篇
  2022年   1篇
  2021年   1篇
  2020年   3篇
  2019年   1篇
  2018年   3篇
  2017年   6篇
  2016年   2篇
  2015年   1篇
  2014年   1篇
  2013年   2篇
  2012年   1篇
  2011年   1篇
  2009年   3篇
  2007年   1篇
  1999年   1篇
  1995年   1篇
排序方式: 共有29条查询结果,搜索用时 15 毫秒
21.
Public Organization Review - The aim of this article is to identify whether the commercialization of NGOs has an influence on the crowding out or crowding in effect of volunteer work, and to...  相似文献   
22.
Journal of Nonverbal Behavior - Individuals automatically mimic a wide range of different behaviors, and such mimicking behavior has several social benefits. One of the landmark findings in the...  相似文献   
23.
24.
Let [^(\varveck)]{\widehat{\varvec{\kappa}}} and [^(\varveck)]r{\widehat{\varvec{\kappa}}_r} denote the best linear unbiased estimators of a given vector of parametric functions \varveck = \varvecKb{\varvec{\kappa} = \varvec{K\beta}} in the general linear models M = {\varvecy, \varvecX\varvecb, s2\varvecV}{{\mathcal M} = \{\varvec{y},\, \varvec{X\varvec{\beta}},\, \sigma^2\varvec{V}\}} and Mr = {\varvecy, \varvecX\varvecb | \varvecR \varvecb = \varvecr, s2\varvecV}{{\mathcal M}_r = \{\varvec{y},\, \varvec{X}\varvec{\beta} \mid \varvec{R} \varvec{\beta} = \varvec{r},\, \sigma^2\varvec{V}\}}, respectively. A bound for the Euclidean distance between [^(\varveck)]{\widehat{\varvec{\kappa}}} and [^(\varveck)]r{\widehat{\varvec{\kappa}}_r} is expressed by the spectral distance between the dispersion matrices of the two estimators, and the difference between sums of squared errors evaluated in the model M{{\mathcal M}} and sub-restricted model Mr*{{\mathcal M}_r^*} containing an essential part of the restrictions \varvecR\varvecb = \varvecr{\varvec{R}\varvec{\beta} = \varvec{r}} with respect to estimating \varveck{\varvec{\kappa}}.  相似文献   
25.
At present, urban areas cover almost 3% of the Earth’s terrestrial area, and this proportion is constantly increasing. Although urbanization leads to a decline in biodiversity, at the same time it creates extensive habitats that are exploited by an assemblage of organisms, including birds. The species composition and density of birds nesting in towns and cities are determined by the types of buildings, the structure and maturity of urban greenery, and habitat diversity. In contrast, the habitat traits shaping the community of birds wintering in urban areas are not known. The aim of this work was to assess the influence of habitat structure, food resources and the urban effects (pollution, noise, artificial light) on an assemblage of birds overwintering in an urban area. It was carried out in 2014 and 2015 in the city of Kraków (southern Poland), on 56 randomly chosen sample plots, in which the composition, density and interseasonal similarity of bird assemblage were assessed with line transect method. A total of 64 bird species (mean = 17.7 ± 4.9 SD species/plot) was recorded. The mean density was 89.6 ind./km ±63.3 SD. The most numerous species were Great Tit Parus major, Magpie Pica pica, Blackbird Turdus merula, Blue Tit Cyanistes caeruleus, Rook Corvus frugilegus, Fieldfare Turdus pilaris and House Sparrow Passer domesticus. Noise adversely affected species numbers and density, but artificial light acted positively on the density of birds and their interseasonal stability. The species richness and density of birds were also determined by the number of food sources available (e.g. bird-feeders). In addition, the greater the proportion of open areas, the fewer species were recorded. In contrast, the more urban greenery there was, the greater the density of the entire bird assemblage. Urban infrastructure (buildings, roads, refuse tips) had a positive effect on the interseasonal stabilization of the species composition of wintering birds. The results of this work indicate that the urban effect, i.e. noise and light pollution, apart from purely habitat factors, provide a good explanation for the species richness, density and stability of bird assemblage wintering in urban areas.  相似文献   
26.
27.
The article describes the tradition of self-immolation in Eastern Europe as a form of radical protest during periods of structural crisis. The authors describe cases of self-immolation (Ryszard Siwiec, Jan Palach, Evzen Plocek, Musa Mamut) which took place in the communist period, particularly in the 1960s and 1970s. In the context of Eastern European tradition, they also describe the last case of self-immolation, when Piotr Szcz?sny set himself on fire in Warsaw in October 2017 to protest against the authoritarian rule of the Law and Justice (PiS) party in Poland. After this incident, Piotr Szcz?sny and his memory have become an element of the ‘culture of protest’ in Poland. Quotes from his manifesto began to appear on walls and during anti-government demonstrations. Piotr Szcz?sny has also become a protagonist of protest songs.  相似文献   
28.
This paper proposes new classifiers under the assumption of multivariate normality for multivariate repeated measures data with Kronecker product covariance structures. These classifiers are especially effective when the number of observations is not large enough to estimate the covariance matrices, and thus the traditional classifiers fail. Computational scheme for maximum likelihood estimates of required class parameters are also given. The quality of these new classifiers are examined on some real data.  相似文献   
29.
The approach to preliminary test estimation based on comparing the weighted quadratic risk function of two competing estimators of β under the linear regression model {y,Xβ, σ2 I} is extended to the case when a given vector of parametric functions κ=Kβ is to be estimated under the general Gauss-Markov model.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号