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1.
Eileen Trzcinski 《Journal of Family and Economic Issues》2002,23(4):339-359
This study was undertaken to determine how middle school children assess the effects of welfare reform on their daily lives. The study consisted of thirty interviews with children and their mothers recruited from a middle school in a large, metropolitan area. From the children's perspective, multiple jobs and evening/night hours interfered with the child-parent relationship. Other consequences included grades going down and not getting to school on time. All the children stated that mothers should work, but most children felt mothers should only work when their children are in school. Welfare and poverty were issues about which children were teased at school. 相似文献
2.
黄雄发 《中国矿业大学学报(社会科学版)》2007,9(4):119-121
二元对立现象广泛存在于文学作品之中,二元对立原则也成为一种重要的文学分析方法。运用此原则研究体现二元对立内涵的文学作品,有助于更全面,深入地发掘作品的内涵和艺术精髓。 相似文献
3.
A growing literature examines the empirical relationship between the joint reproductive preferences of marital partners and reproductive outcomes in Africa. Less explored is how spousal power in decision making may be influenced by lineage type. Using pooled data from Ghana, we investigate how lineage affects gendered reproductive decision outcomes and find some evidence that matrilineal women are more able than nonmatrilineal women to translate their reproductive preferences into action consistent with their goals. 相似文献
4.
Longitudinal data often contain missing observations, and it is in general difficult to justify particular missing data mechanisms, whether random or not, that may be hard to distinguish. The authors describe a likelihood‐based approach to estimating both the mean response and association parameters for longitudinal binary data with drop‐outs. They specify marginal and dependence structures as regression models which link the responses to the covariates. They illustrate their approach using a data set from the Waterloo Smoking Prevention Project They also report the results of simulation studies carried out to assess the performance of their technique under various circumstances. 相似文献
5.
Donald B. Rubin 《Scandinavian Journal of Statistics》2004,31(2):161-170
Abstract. The use of the concept of ‘direct’ versus ‘indirect’ causal effects is common, not only in statistics but also in many areas of social and economic sciences. The related terms of ‘biomarkers’ and ‘surrogates’ are common in pharmacological and biomedical sciences. Sometimes this concept is represented by graphical displays of various kinds. The view here is that there is a great deal of imprecise discussion surrounding this topic and, moreover, that the most straightforward way to clarify the situation is by using potential outcomes to define causal effects. In particular, I suggest that the use of principal stratification is key to understanding the meaning of direct and indirect causal effects. A current study of anthrax vaccine will be used to illustrate ideas. 相似文献
6.
Chris J. Lloyd 《Australian & New Zealand Journal of Statistics》2002,44(1):75-86
This paper presents a method of estimating a receiver operating characteristic (ROC) curve when the underlying diagnostic variable X is continuous and fully observed. The new method is based on modelling the probability of response given X , rather than the distribution of X given response. The method offers advantages in modelling flexibility and computational simplicity. The resulting ROC curve estimates are semi-parametric and can, in principle, take an infinite variety of shapes. Moreover, model selection can be based on standard methods within the binomial regression framework. Statistical accuracy of the curve estimate is provided by a simply implemented bootstrap approach. 相似文献
7.
The authors consider the optimal design of sampling schedules for binary sequence data. They propose an approach which allows a variety of goals to be reflected in the utility function by including deterministic sampling cost, a term related to prediction, and if relevant, a term related to learning about a treatment effect To this end, they use a nonparametric probability model relying on a minimal number of assumptions. They show how their assumption of partial exchangeability for the binary sequence of data allows the sampling distribution to be written as a mixture of homogeneous Markov chains of order k. The implementation follows the approach of Quintana & Müller (2004), which uses a Dirichlet process prior for the mixture. 相似文献
8.
The benchmark dose (BMD) is an exposure level that would induce a small risk increase (BMR level) above the background. The BMD approach to deriving a reference dose for risk assessment of noncancer effects is advantageous in that the estimate of BMD is not restricted to experimental doses and utilizes most available dose-response information. To quantify statistical uncertainty of a BMD estimate, we often calculate and report its lower confidence limit (i.e., BMDL), and may even consider it as a more conservative alternative to BMD itself. Computation of BMDL may involve normal confidence limits to BMD in conjunction with the delta method. Therefore, factors, such as small sample size and nonlinearity in model parameters, can affect the performance of the delta method BMDL, and alternative methods are useful. In this article, we propose a bootstrap method to estimate BMDL utilizing a scheme that consists of a resampling of residuals after model fitting and a one-step formula for parameter estimation. We illustrate the method with clustered binary data from developmental toxicity experiments. Our analysis shows that with moderately elevated dose-response data, the distribution of BMD estimator tends to be left-skewed and bootstrap BMDL s are smaller than the delta method BMDL s on average, hence quantifying risk more conservatively. Statistically, the bootstrap BMDL quantifies the uncertainty of the true BMD more honestly than the delta method BMDL as its coverage probability is closer to the nominal level than that of delta method BMDL. We find that BMD and BMDL estimates are generally insensitive to model choices provided that the models fit the data comparably well near the region of BMD. Our analysis also suggests that, in the presence of a significant and moderately strong dose-response relationship, the developmental toxicity experiments under the standard protocol support dose-response assessment at 5% BMR for BMD and 95% confidence level for BMDL. 相似文献
9.
基于二相编码雷达对大压缩比信号的要求,提出了一种比直接算法平均提高效率0.5P(P 为序列长度)的快速数字优化方法。作为这种快速算法的实际应用,还对 P=255的二相编码脉冲压缩信号进行了优化。 相似文献
10.
从收支项目看秦汉二元财政的源流 总被引:1,自引:0,他引:1
汉代财政分为国家财政和帝室财政,由大司农和少府分掌,为大家所熟知。但对二元财政的来源却少有辨析,一般承袭郑玄关于大司农是太府继承的说法。实际上少府和太府在收支项目上都比较接近,有着明显的继承关系,而大司农则是由负责主持策命诸侯及保管爵禄文书的内史演变而来。在国家职能转轨过程中,内史发展成为管理国家财政及畿内地区事务的机构,最后进一步分离出专门管理国家财政的治粟内史。二元财政体制的设计来源于收支对应的原始财政平衡思想。 相似文献