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151.
Genetic algorithms for numerical optimization 总被引:3,自引:0,他引:3
Genetic algorithms (GAs) are stochastic adaptive algorithms whose search method is based on simulation of natural genetic inheritance and Darwinian striving for survival. They can be used to find approximate solutions to numerical optimization problems in cases where finding the exact optimum is prohibitively expensive, or where no algorithm is known. However, such applications can encounter problems that sometimes delay, if not prevent, finding the optimal solutions with desired precision. In this paper we describe applications of GAs to numerical optimization, present three novel ways to handle such problems, and give some experimental results. 相似文献
152.
文章基于面板数据,利用固定效应估计法和随机效应估计法,对我国在1999年至2002年间农业信贷的绩效作出实证研究。研究结果表明,我国农业信贷配置机制应作进一步的调整,以便提高农业信贷的绩效,支持农业发展。 相似文献
153.
The effects of non-normality on type-I and type-II errors in a one-way random model are investigated for moderate departures
from normality. It is found that the probabilities of both errors are more sensitive to the kurtosis of between group effects
than that of within group effects. 相似文献
154.
Incomplete covariate data is a common occurrence in many studies in which the outcome is survival time. With generalized linear models, when the missing covariates are categorical, a useful technique for obtaining parameter estimates is the EM by the method of weights proposed in Ibrahim (1990). In this article, we extend the EM by the method of weights to survival outcomes whose distributions may not fall in the class of generalized linear models. This method requires the estimation of the parameters of the distribution of the covariates. We present a clinical trials example with five covariates, four of which have some missing values. 相似文献
155.
AXEL MUNK 《Scandinavian Journal of Statistics》2002,29(3):501-533
ABSTRACT: We introduce a class of Toeplitz‐band matrices for simple goodness of fit tests for parametric regression models. For a given length r of the band matrix the asymptotic optimal solution is derived. Asymptotic normality of the corresponding test statistic is established under a fixed and random design assumption as well as for linear and non‐linear models, respectively. This allows testing at any parametric assumption as well as the computation of confidence intervals for a quadratic measure of discrepancy between the parametric model and the true signal g;. Furthermore, the connection between testing the parametric goodness of fit and estimating the error variance is highlighted. As a by‐product we obtain a much simpler proof of a result of 34 ) concerning the optimality of an estimator for the variance. Our results unify and generalize recent results by 9 ) and 15 , 16 ) in several directions. Extensions to multivariate predictors and unbounded signals are discussed. A simulation study shows that a simple jacknife correction of the proposed test statistics leads to reasonable finite sample approximations. 相似文献
156.
157.
Aaron Childs 《Statistical Papers》2006,47(2):299-310
In this paper we present analogues of Balakrishnan's (1989) relations that relate the triple and quadruple moments of order
statistics from independent and nonidentically distributed (I.NI.D.) random variables from a symmetric distribution to those
of the folded distribution. We then apply these results, along with the corresponding recurrence relations for the exponential
distribution derived recently by Childs (2003), to study the robustness of the Winsorized variance. 相似文献
158.
采用永久随机数法抽样技术抽到的样本具有很好地样本兼容的性质。本文讨论了采用序贯srswor抽样技术和Poisson抽样技术这两种永久随机数法抽样技术时,多层次调查的实现问题,希望能为多层次调查的实现提供一点启示。 相似文献
159.
证明了右半平面上无限级随机Dirichlet级数的超级几乎必然与其在每条水平直线上的超级相同。 相似文献
160.
John Copas Shinto Eguchi 《Journal of the Royal Statistical Society. Series B, Statistical methodology》2005,67(4):459-513
Summary. Problems of the analysis of data with incomplete observations are all too familiar in statistics. They are doubly difficult if we are also uncertain about the choice of model. We propose a general formulation for the discussion of such problems and develop approximations to the resulting bias of maximum likelihood estimates on the assumption that model departures are small. Loss of efficiency in parameter estimation due to incompleteness in the data has a dual interpretation: the increase in variance when an assumed model is correct; the bias in estimation when the model is incorrect. Examples include non-ignorable missing data, hidden confounders in observational studies and publication bias in meta-analysis. Doubling variances before calculating confidence intervals or test statistics is suggested as a crude way of addressing the possibility of undetectably small departures from the model. The problem of assessing the risk of lung cancer from passive smoking is used as a motivating example. 相似文献