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131.
In this paper we examine the small sample distribution of the likelihood ratio test in the random effects model which is often recommended for meta-analyses. We find that this distribution depends strongly on the true value of the heterogeneity parameter (between-study variance) of the model, and that the correct p-value may be quite different from its large sample approximation. We recommend that the dependence of the heterogeneity parameter be examined for the data at hand and suggest a (simulation) method for this. Our setup allows for explanatory variables on the study level (meta-regression) and we discuss other possible applications, too. Two data sets are analyzed and two simulation studies are performed for illustration. 相似文献
132.
Paul A. Ruud 《Econometric Reviews》1984,3(2):211-242
This survey of recent developments in testing for misspecification of econometric models reviews procedures based on a method due to Hausman. Particular attention is given to alternative forms of the test, its relationship to classical test procedures, and its role in pre-test estimation. 相似文献
133.
天线罩覆盖的波束近轴场 总被引:2,自引:0,他引:2
本文根据复射线法对通过介质天线罩的高斯波束场进行近轴近似分析。实空间的轴向复射线追综大大简化了计算过程,而复相位差、反射-传输系数和曲面扩散系数的进一步校正则提供了相当精确的结果。所得数字结果表明,在波束的近轴区域内为获得同样的计算精度,近轴近似法所需要的计算机时间远小于复射线追综法的时间。 相似文献
134.
We consider the calculation of power functions in classical multivariate analysis. In this context, power can be expressed
in terms of tail probabilities of certain noncentral distributions. The necessary noncentral distribution theory was developed
between the 1940s and 1970s by a number of authors. However, tractable methods for calculating the relevant probabilities
have been lacking. In this paper we present simple yet extremely accurate saddlepoint approximations to power functions associated
with the following classical test statistics: the likelihood ratio statistic for testing the general linear hypothesis in
MANOVA; the likelihood ratio statistic for testing block independence; and Bartlett's modified likelihood ratio statistic
for testing equality of covariance matrices. 相似文献
135.
宣培才 《绍兴文理学院学报》1992,(6)
本文推广了的结果,主要研究了一类Ismail-May算子线性组合的同时逼近问题,在一致通近意义下,给出了逼近的正定理、逆定理及非最优逼近阶的特征刻划. 相似文献
136.
Kallappa M. Koti 《Pharmaceutical statistics》2003,2(2):133-144
Using a Yamaguchi‐type generalized gamma failure‐time mixture model, we analyse the data from a study of autologous and allogeneic bone marrow transplantation in the treatment of high‐risk refractory acute lymphoblastic leukaemia, focusing on the time to recurrence of disease. We develop maximum likelihood techniques for the joint estimation of the surviving fractions and the survivor functions. This includes an approximation to the derivative of the survivor function with respect to the shape parameter. We obtain the maximum likelihood estimates of the model parameters. We also compute the variance‐covariance matrix of the parameter estimators. The extended family of generalized gamma failure‐time mixture models is flexible enough to include many commonly used failure‐time distributions as special cases. Yet these models are not used in practice because of computational difficulties. We claim that we have overcome this problem. The proposed approximation to the derivative of the survivor function with respect to the shape parameter can be used in any statistical package. We also address the issue of lack of identifiability. We point out that there can be a substantial advantage to using the gamma failure‐time mixture models over nonparametric methods. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
137.
Let X 1, X 2,…, X n be independent exponential random variables with X i having failure rate λ i for i = 1,…, n. Denote by D i:n = X i:n ? X i?1:n the ith spacing of the order statistics X 1:n ≤ X 2:n ≤ ··· ≤ X n:n , i = 1,…, n, where X 0:n ≡ 0. It is shown that if λ n+1 ≤ [≥] λ k for k = 1,…, n then D n:n ≤ lr D n+1:n+1 and D 1:n ≤ lr D 2:n+1 [D 2:n+1 ≤ lr D 2:n ], and that if λ i + λ j ≥ λ k for all distinct i,j, and k then D n?1:n ≤ lr D n:n and D n:n+1 ≤ lr D n:n , where ≤ lr denotes the likelihood ratio order. We also prove that D 1:n ≤ lr D 2:n for n ≥ 2 and D 2:3 ≤ lr D 3:3 for all λ i 's. 相似文献
138.
In this article, we consider the product-limit quantile estimator of an unknown quantile function under a censored dependent model. This is a parallel problem to the estimation of the unknown distribution function by the product-limit estimator under the same model. Simultaneous strong Gaussian approximations of the product-limit process and product-limit quantile process are constructed with rate O[(log n)?λ] for some λ > 0. The strong Gaussian approximation of the product-limit process is then applied to derive the laws of the iterated logarithm for product-limit process. 相似文献
139.
The exponential distribution is one of the most used type of distribution because of its importance in many lifetime applications and its properties. So is its bivariate form. Simply used, there can be limitations specially for the heterogeneous type population. Its mixture form adds a lot of characters and desirable properties. We propose a mixture of bivariate exponential distribution, study properties of the associated parameters and predict the elements of the mixture. We include the presence of covariate information through a linear relationship, capturing the now famous idea by Marshall and Olkin. 相似文献
140.
In this article, we consider two independent zero-inflated power series distributions and provide likelihood ratio test for equality of inflation parameters of the same. As an illustration, testing equality of inflation parameters of two zero inflated Poisson distributions is provided. Further, simulation study to investigate power of likelihood ratio tests has been carried out. 相似文献