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51.
In risk assessment, the moment‐independent sensitivity analysis (SA) technique for reducing the model uncertainty has attracted a great deal of attention from analysts and practitioners. It aims at measuring the relative importance of an individual input, or a set of inputs, in determining the uncertainty of model output by looking at the entire distribution range of model output. In this article, along the lines of Plischke et al., we point out that the original moment‐independent SA index (also called delta index) can also be interpreted as the dependence measure between model output and input variables, and introduce another moment‐independent SA index (called extended delta index) based on copula. Then, nonparametric methods for estimating the delta and extended delta indices are proposed. Both methods need only a set of samples to compute all the indices; thus, they conquer the problem of the “curse of dimensionality.” At last, an analytical test example, a risk assessment model, and the levelE model are employed for comparing the delta and the extended delta indices and testing the two calculation methods. Results show that the delta and the extended delta indices produce the same importance ranking in these three test examples. It is also shown that these two proposed calculation methods dramatically reduce the computational burden. 相似文献
52.
张迎辉 《石家庄铁道学院学报(社会科学版)》2012,(2):68-72
在工程防沙设计中,阻沙率和输沙强度均是确定防护类型及其宽度的重要指标。从工程实际出发,结合典型地形特征,运用实测的阻沙率指标,优化沙漠公路高大沙丘段防沙体系的设计,用理论指导实践的同时,并在实践施工中加以较好地运用,从实践效果上,以阻沙率这一风沙物理指标为依据,确定高大沙丘段的防沙设计参数,是符合实际和可行的方法。 相似文献
53.
《Journal of Statistical Computation and Simulation》2012,82(5):671-679
This paper provides a saddlepoint approximation to the distribution of the sample version of Kendall's τ, which is a measure of association between two samples. The saddlepoint approximation is compared with the Edgeworth and the normal approximations, and with the bootstrap resampling distribution. A numerical study shows that with small sample sizes the saddlepoint approximation outperforms both the normal and the Edgeworth approximations. This paper gives also an analytical comparison between approximated and exact cumulants of the sample Kendall's τ when the two samples are independent. 相似文献
54.
Xiang Zhang 《Journal of nonparametric statistics》2014,26(2):321-340
Multivariate density estimation plays an important role in investigating the mechanism of high-dimensional data. This article describes a nonparametric Bayesian approach to the estimation of multivariate densities. A general procedure is proposed for constructing Feller priors for multivariate densities and their theoretical properties as nonparametric priors are established. A blocked Gibbs sampling algorithm is devised to sample from the posterior of the multivariate density. A simulation study is conducted to evaluate the performance of the procedure. 相似文献
55.
以广州荔湾区“六普”资料为根据,就人口高密度分布与社区建设的关系进行梳理与探讨。荔湾区“六普”数据显示,城区人口密度过高,成为影响社区生活的主要因素,给居民生命安全、公共生活质量与日常生活便利性带来负面效应。科学化与人性化人口密度干预是治理高密度人口问题的理性策略,如“跳出”社区视野,在城市“一盘棋”中均衡人口布局,在社区建设中,通过社区更新改造,增强人口承载能力,通过建构便利舒适人居环境,提升社区生活质量。 相似文献
56.
《Journal of Statistical Computation and Simulation》2012,82(11):1317-1329
This contribution deals with the Monte Carlo simulation of generalized Gaussian random variables. Such a parametric family of distributions has been proposed in many applications in science to describe physical phenomena and in engineering, and it seems to be also useful in modelling economic and financial data. For values of the shape parameter α within a certain range, the distribution presents heavy tails. In particular, the cases α=1/3 and α=1/2 are considered. For such values of the shape parameter, different simulation methods are assessed. 相似文献
57.
《Journal of Statistical Computation and Simulation》2012,82(4):833-849
Bayesian analysis often requires the researcher to employ Markov Chain Monte Carlo (MCMC) techniques to draw samples from a posterior distribution which in turn is used to make inferences. Currently, several approaches to determine convergence of the chain as well as sensitivities of the resulting inferences have been developed. This work develops a Hellinger distance approach to MCMC diagnostics. An approximation to the Hellinger distance between two distributions f and g based on sampling is introduced. This approximation is studied via simulation to determine the accuracy. A criterion for using this Hellinger distance for determining chain convergence is proposed as well as a criterion for sensitivity studies. These criteria are illustrated using a dataset concerning the Anguilla australis, an eel native to New Zealand. 相似文献
58.
《Journal of Statistical Computation and Simulation》2012,82(9):1155-1167
The two parametric distribution functions appearing in the extreme-value theory – the generalized extreme-value distribution and the generalized Pareto distribution – have log-concave densities if the extreme-value index γ∈[?1, 0]. Replacing the order statistics in tail-index estimators by their corresponding quantiles from the distribution function that is based on the estimated log-concave density ? f n leads to novel smooth quantile and tail-index estimators. These new estimators aim at estimating the tail index especially in small samples. Acting as a smoother of the empirical distribution function, the log-concave distribution function estimator reduces estimation variability to a much greater extent than it introduces bias. As a consequence, Monte Carlo simulations demonstrate that the smoothed version of the estimators are well superior to their non-smoothed counterparts, in terms of mean-squared error. 相似文献
59.
认识储层岩石中含油饱和度及饱和度分布,对驱替机理的深入研究是非常重要的。为了搞清储层岩石在驱替过程中的饱和度分布情况,应用工业CT技术,提出了一种储层含油岩芯被驱替后的饱和度分布的CT密度差测量方法。在岩样的同一断面,分别对干岩样、饱和岩样及在驱替后的岩样进行CT扫描,重建相应的断层图象,测量所建图象的灰度值,计算出相应的密度值,用密度差法计算出饱和度及其分布值。在γ射线工业CT机“CD-300BG”上对某油田岩样进行了实际测量,获得的结果说明,采用CT密度差法测量饱和度分布是有效的。该方法与常规驱替法相比较,具有快速、精度高、无损岩样和能模拟地层状态测量等特点,是油田开发、油藏描述和地层评价的一种新的有效方法。 相似文献
60.
Extensive research has shown individual religiosity to have an impact upon U.S. protest participation. But very little work has examined the role of religious density in a community on the likelihood of protest mobilization. Our research links the religious density across 62 counties in New York State to various protest mobilization issues during the period of 1960–1995. In this research, we develop a theory of socially organized sentiments to examine religious influences on overall protest event mobilizations in local communities, a specific example of a more general theory that can link community structure to multiple forms of civic engagement. The impact of various religious traditions is assessed by using measures for the density of religious population per congregation of three religious traditions—Mainline Protestantism, Evangelical Protestantism and Catholicism. The analysis also assesses the likelihood of mobilization concerning four specific issues—African-American civil rights, gender, anti-nuclear/peace, and anti-poverty movements. 相似文献