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31.
We demonstrate the existence and uniqueness of optimal observation schedules for discrete observation of the simple death process. Optimality is framed in the sense of observing the process at times that maximise the Fisher information for the death rate. We examine the relationship of our designs with those obtained by other authors for the simple birth process. A number of interesting properties are uncovered. Practical considerations in the application of these designs in an experimental setting are investigated, and we examine the performance of some approximately optimal designs that are usually simpler to implement. We will show that our optimal designs are highly robust to mis-specification of the death rate. 相似文献
32.
P. W. West 《统计学通讯:模拟与计算》2017,46(6):4951-4965
Simulations of forest inventory in several populations compared simple random with “quick probability proportional to size” (QPPS) sampling. The latter may be applied in the absence of a list sampling frame and/or prior measurement of the auxiliary variable. The correlation between the auxiliary and target variables required to render QPPS sampling more efficient than simple random sampling varied over the range 0.3–0.6 and was lower when sampling from populations that were skewed to the right. Two possible analytical estimators of the standard error of the estimate of the mean for QPPS sampling were found to be less reliable than bootstrapping. 相似文献
33.
针对区域海洋产业结构相近的问题,对区域海洋战略性主导产业的选择进行了研究,界定了海洋战略性主导产业的概念与范围,分析了其演变规律,并以天津滨海新区为例,运用层次分析一熵值组合赋权法对其海洋战略性主导产业进行了选择,最终确定了以海水综合利用为核心,海洋化工和石油天然气协同发展的海洋战略性主导产业循环经济产业链,旨在推动滨海新区海洋产业结构优化和产业层次的提升,促进天津海洋经济的发展,为同类型区域海洋产业的发展提供借鉴。 相似文献
34.
利用大数据进行抽样,很多情况下抽样框的构造比较困难,使得抽取的样本属于非概率样本,难以将传统的抽样推断理论应用到非概率样本中,如何解决非概率抽样的统计推断问题,是大数据背景下抽样调查面临的严重挑战。本文提出了解决非概率抽样统计推断问题的基本思路:一是抽样方法,可以考虑基于样本匹配的样本选择、链接跟踪抽样方法等,使得到的非概率样本近似于概率样本,从而可采用概率样本的统计推断理论;二是权数的构造与调整,可以考虑基于伪设计、模型和倾向得分等方法得到类似于概率样本的基础权数;三是估计,可以考虑基于伪设计、模型和贝叶斯的混合概率估计。最后,以基于样本匹配的样本选择为例探讨了具体解决方法。 相似文献
35.
36.
The estimation of the means of the bivariate normal distribution, based on a sample obtained using a modification of the moving
extreme ranked set sampling technique (MERSS) is considered. The modification involves using a concomitant random variable.
Nonparametric-type methods as well as the maximum likelihood estimation are considered. The estimators obtained are compared
to their counterparts based on simple random sampling (SRS). It appears that the suggested estimators are more efficient.
Also, MERSS with concomitant variable is easier to use in practice than the usual ranked set sampling (RSS) with concomitant
variable. The issue of robustness of the procedure is addressed. Real trees data set is used for illustration. 相似文献
37.
刘歆计量理论管窥 总被引:1,自引:0,他引:1
关增建 《郑州大学学报(哲学社会科学版)》2003,36(2):125-130
刘歆在协助王莽改革度量衡的过程中,提出了系统的计量理论。其理论涉及到数在计量中的作用、音律本性及其与计量的关系、度量衡基准的选择依据以及度量衡标准器的设计等内客。其理论的核心部分被后人广泛接受,成为传统计量发展的圭臬,而该理论本身也成了中国古代传统计量理论形成的标志。 相似文献
38.
The main problem in applying the mean-variance portfolio selection consists of the fact that the first
two moments of the asset returns are unknown. In practice the optimal portfolio weights have to be estimated.
This is usually done by replacing the moments by the classical unbiased sample estimators. We provide a comparison
of the exact and the asymptotic distributions of the estimated portfolio weights as well as a sensitivity
analysis to shifts in the moments of the asset returns. Furthermore we consider several types of shrinkage
estimators for the moments. The corresponding estimators of the portfolio weights are compared with each
other and with the portfolio weights based on the sample estimators of the moments. We show how the uncertainty
about the portfolio weights can be introduced into the performance measurement of trading strategies. The
methodology explains the bad out-of-sample performance of the classical Markowitz procedures. 相似文献
39.
S. K. Sahu T. M. F. Smith 《Journal of the Royal Statistical Society. Series A, (Statistics in Society)》2006,169(2):235-253
Summary. The problem motivating the paper is the determination of sample size in clinical trials under normal likelihoods and at the substantive testing stage of a financial audit where normality is not an appropriate assumption. A combination of analytical and simulation-based techniques within the Bayesian framework is proposed. The framework accommodates two different prior distributions: one is the general purpose fitting prior distribution that is used in Bayesian analysis and the other is the expert subjective prior distribution, the sampling prior which is believed to generate the parameter values which in turn generate the data. We obtain many theoretical results and one key result is that typical non-informative prior distributions lead to very small sample sizes. In contrast, a very informative prior distribution may either lead to a very small or a very large sample size depending on the location of the centre of the prior distribution and the hypothesized value of the parameter. The methods that are developed are quite general and can be applied to other sample size determination problems. Some numerical illustrations which bring out many other aspects of the optimum sample size are given. 相似文献
40.