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   163篇
  免费   7篇
管理学   31篇
民族学   2篇
人口学   12篇
丛书文集   1篇
理论方法论   16篇
综合类   4篇
社会学   73篇
统计学   31篇
  2023年   1篇
  2022年   1篇
  2021年   4篇
  2020年   8篇
  2019年   12篇
  2018年   14篇
  2017年   10篇
  2016年   10篇
  2015年   7篇
  2014年   4篇
  2013年   25篇
  2012年   2篇
  2011年   5篇
  2010年   3篇
  2009年   6篇
  2008年   7篇
  2007年   2篇
  2006年   6篇
  2005年   2篇
  2004年   5篇
  2003年   1篇
  2002年   2篇
  2001年   4篇
  1999年   4篇
  1998年   1篇
  1995年   2篇
  1992年   1篇
  1990年   1篇
  1987年   2篇
  1986年   2篇
  1985年   3篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1967年   1篇
排序方式: 共有170条查询结果,搜索用时 15 毫秒
101.
An incidence in a graph G is a pair (ve) where v is a vertex of G and e is an edge of G incident to v. Two incidences (ve) and (uf) are adjacent if at least one of the following holds: \((a) v = u, (b) e = f\), or \((c) vu \in \{e,f\}\). An incidence coloring of G is a coloring of its incidences assigning distinct colors to adjacent incidences. In this note we prove that every subquartic graph admits an incidence coloring with at most seven colors.  相似文献   
102.
This paper proposes a new model for square contingency tables. The proposed model tests the equality of local odds ratios between the one side of the main diagonal and corresponding other side and it represents the non-symmetric structure of the square contingency table. The proposed model is compared with twenty-five models introduced for analysing the square contingency tables for both symmetric and non-symmetric structures. The results show that the proposed model provides best fit performance than other existing models for square contingency tables.  相似文献   
103.
Previous research has demonstrated that children who grow up in foster family care – along with other child welfare recipients – manage less well in adulthood compared to those children who do not. Given this challenge, this integrative literature review locates the critical factors that either positively or negatively affect a child’s development in foster family care. The articles were analysed using theory-driven content classification in relation to Bronfenbrenner’s bioecological framework on child development. The results of the review suggest that there is a wide range of factors that could impact on a child’s development in foster family care. Child­related factors such as the child’s age, gender, behavioural or mental health problems, etc. were mentioned most often in the data. Micro­environmental factors are also essential to a child’s development. Linkages taking place between two or more of the child’s circumstances, such as the relationship between the child’s birth and foster families and between the foster family and the social worker, were also identified as being influential. Service usage and political and legislative factors, as well as attitudes towards children in care, were also indicated to be strongly influential. It is suggested that the factors identified in this review should be carefully considered as important aspects of care for fostered children and care documentation.  相似文献   
104.
We analyze markets in which the price of a traded commodity is such that the supply and the demand are unequal. Under standard assumptions, the agents then have single peaked preferences on their consumption or production choices. For such markets, we propose a class of Uniform trade rules each of which determines the volume of trade as the median of total demand, total supply, and an exogenous constant. Then these rules allocate this volume “uniformly” on either side of the market. We evaluate these “trade rules” on the basis of some standard axioms in the literature. We show that they uniquely satisfy Pareto optimality, strategy proofness, no-envy, and an informational simplicity axiom that we introduce. We also analyze the implications of anonymity, renegotiation proofness, and voluntary trade on this domain.  相似文献   
105.
Abstract The economic experiences and economic anxiety of rural and urban residents of the Czech and Slovak Republics during the postcommunist reforms are compared and related to their support for the reforms. The analysis is based on five national surveys, 1992–1996, collected by the Sociology Institute of the now Czech Academy of Sciences. Net of controls, both Czech and Slovak rural respondents report more economic strain and unemployment, a difference that persists over the surveys. These experiences account for rural residents' greater economic anxiety, their fear of economic development and unemployment, which also persists over the surveys. These experiences and anxiety explain, in turn, their lower level of support for the reforms, and endorsement of a return to socialism and strong-hand government. Rural and urban respondents of the two countries have experienced the world differently since 1990, and this is expressed in their economic anxiety and political preferences.  相似文献   
106.
Urban areas are probably the most fragmented environments with respect to the presence of semi-natural habitats and shape of these habitats may be significantly affected by urbanization. Patch perimeter in landscape or habitat studies is much less popular to study than patch area. The studied sites were situated in the industrial city of Pardubice, which is one of the ten largest cities in the Czech Republic with nearly 100,000 inhabitants. In total, 40 grasslands were studied within a circular area of 314 km2. Butterflies and beetles with diurnal activity were studied during timed survey walks. A Simultaneous autoregressive model was used for test of the effect of biodiversity-area and biodiversity-perimeter relationships and for exclusion of potential bias caused by spatial autocorrelation. The models including patch perimeter performed better than those using patch area in explaining species richness, abundance and diversity of investigated organisms and were less influenced by spatial autocorrelation. The main conclusion and recommendation of the present study is that researchers should pay more attention to the possible influence of the patch perimeter as a potential predictor or co-predictor for landscape and habitat studies – especially in urban areas, where the negative effects of fragmentation might be much higher than in rural or more natural landscapes. Performing preliminary tests on comparisons between area and perimeter is highly recommended.  相似文献   
107.
This article explores the relationship between the child protection systems and the Nordic welfare state in Denmark, Finland and Norway. Despite an ideological focus on prevention and provision of a fair amount of universal services and in-home child protection services for families and children, there is, nevertheless, a relatively high number of children in the child protection system, even children placed out of their home. The outcome of child protection seems to be relatively poor. One of the problems in the present child protection systems is related to questionable service provision within the system. Other problems are about the normative foundation for the system, for example, family orientation and the least intrusive principle. Such principles are closely related to the logic of universal services, and may as such ignore the diversity of needs, rights, risks and ages of children needing protection and related services. Consequently, many principles of the present child protection systems are – and will remain – challenged by a child-centric orientation, in which valuing children's needs, rights and voice in situ are central.  相似文献   
108.
This paper exploits the discrete jump in alcohol consumption at the minimum legal drinking age (MLDA) in the USA and uses a regression discontinuity design to investigate the relationship between drinking and risky sexual behaviors among young adults. Using confidential data from the National Longitudinal Survey of Youth (1997 Cohort), we document that young adults tend to drink up to 2.1 days more once they are granted legal access to alcohol at age 21. Although the discrete jump in alcohol consumption at the MLDA is associated with an increase in the probability of having sex by up to 7.8 percentage points, it does not have a significant impact on the probability of engaging in risky sexual behaviors among young adults. We also document that the effect of the MLDA on the probability of using several different birth control methods is not significant for those who had sex in the past 4 weeks. These results are robust under alternative specifications and imply that although the MLDA law is quite effective in reducing alcohol consumption among young adults, spillover effects of this law on risky sexual behaviors are relatively limited.  相似文献   
109.
In this paper, we extend the focused information criterion (FIC) to copula models. Copulas are often used for applications where the joint tail behavior of the variables is of particular interest, and selecting a copula that captures this well is then essential. Traditional model selection methods such as the Akaike information criterion (AIC) and the Bayesian information criterion (BIC) aim at finding the overall best‐fitting model, which is not necessarily the one best suited for the application at hand. The FIC, on the other hand, evaluates and ranks candidate models based on the precision of their point estimates of a context‐given focus parameter. This could be any quantity of particular interest, for example, the mean, a correlation, conditional probabilities, or measures of tail dependence. We derive FIC formulae for the maximum likelihood estimator, the two‐stage maximum likelihood estimator, and the so‐called pseudo‐maximum‐likelihood (PML) estimator combined with parametric margins. Furthermore, we confirm the validity of the AIC formula for the PML estimator combined with parametric margins. To study the numerical behavior of FIC, we have carried out a simulation study, and we have also analyzed a multivariate data set pertaining to abalones. The results from the study show that the FIC successfully ranks candidate models in terms of their performance, defined as how well they estimate the focus parameter. In terms of estimation precision, FIC clearly outperforms AIC, especially when the focus parameter relates to only a specific part of the model, such as the conditional upper‐tail probability.  相似文献   
110.
Speech rhythm is considered one of the first windows into the native language, and the taxonomy of rhythm classes is commonly used to explain early language discrimination. Relying on formal rhythm classification is problematic for two reasons. First, it is not known to which extent infants’ sensitivity to language variation is attributable to rhythm alone, and second, it is not known how infants discriminate languages not classified in any of the putative rhythm classes. Employing a central-fixation preference paradigm with natural stimuli, this study tested whether infants differentially attend to native versus nonnative varieties that differ only in temporal rhythm cues, and both of which are rhythmically unclassified. An analysis of total looking time did not detect any rhythm preferences at any age. First-look duration, arguably more closely reflecting infants’ underlying perceptual sensitivities, indicated age-specific preferences for native versus non-native rhythm: 4-month-olds seemed to prefer the native-, and 6-month-olds the non-native language-variety. These findings suggest that infants indeed acquire native rhythm cues rather early, by the 4th month, supporting the theory that rhythm can bootstrap further language development. Our data on infants’ processing of rhythmically unclassified languages suggest that formal rhythm classification does not determine infants’ ability to discriminate language varieties.  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