全文获取类型
收费全文 | 11021篇 |
免费 | 308篇 |
国内免费 | 229篇 |
专业分类
管理学 | 1154篇 |
民族学 | 40篇 |
人才学 | 3篇 |
人口学 | 66篇 |
丛书文集 | 1009篇 |
理论方法论 | 319篇 |
综合类 | 7586篇 |
社会学 | 471篇 |
统计学 | 910篇 |
出版年
2024年 | 32篇 |
2023年 | 130篇 |
2022年 | 160篇 |
2021年 | 158篇 |
2020年 | 227篇 |
2019年 | 222篇 |
2018年 | 222篇 |
2017年 | 254篇 |
2016年 | 284篇 |
2015年 | 325篇 |
2014年 | 616篇 |
2013年 | 711篇 |
2012年 | 645篇 |
2011年 | 679篇 |
2010年 | 555篇 |
2009年 | 564篇 |
2008年 | 628篇 |
2007年 | 695篇 |
2006年 | 761篇 |
2005年 | 673篇 |
2004年 | 681篇 |
2003年 | 683篇 |
2002年 | 514篇 |
2001年 | 464篇 |
2000年 | 264篇 |
1999年 | 107篇 |
1998年 | 63篇 |
1997年 | 35篇 |
1996年 | 42篇 |
1995年 | 30篇 |
1994年 | 16篇 |
1993年 | 28篇 |
1992年 | 19篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
881.
Inference for a Simple Step-Stress Model with Type-I Censoring and Lognormally Distributed Lifetimes
Accelerated life-testing (ALT) is a very useful technique for examining the reliability of highly reliable products. It allows the experimenter to obtain failure data more quickly at increased stress levels than under normal operating conditions. A step-stress model is one special class of ALT, and in this article we consider a simple step-stress model under the cumulative exposure model with lognormally distributed lifetimes in the presence of Type-I censoring. We then discuss inferential methods for the unknown parameters of the model by the maximum likelihood estimation method. Some numerical methods, such as the Newton–Raphson and quasi-Newton methods, are discussed for solving the corresponding non-linear likelihood equations. Next, we discuss the construction of confidence intervals for the unknown parameters based on (i) the asymptotic normality of the maximum likelihood estimators (MLEs), and (ii) parametric bootstrap resampling technique. A Monte Carlo simulation study is carried out to examine the performance of these methods of inference. Finally, a numerical example is presented in order to illustrate all the methods of inference developed here. 相似文献
882.
Jeffrey D. Hart 《统计学通讯:理论与方法》2013,42(12):2943-2945
P. Ghosh (1981) has claimed that the convolution of two symmetric multimodal distributions is symmetric and unimodal. A simple counterexample to this claim is constructed by considering the convolution f?f, where f is an appropriate mixture of two normal densities. 相似文献
883.
Rober Haining 《统计学通讯:理论与方法》2013,42(2):573-597
The paper examines alternative estimators for the mean of a spatial process where observations are not independent. Properties of the sample mean and its standard error are contrasted with those of maximum likelihood estimators derived for three spatial models. The information loss caused by spatial dependency in the data is examined. The distribution theory for the estimators is reviewed and the paper concludes with an empirical example illustrating the properties of the estimators and the practical benefits of the maximum likelihood procedure. 相似文献
884.
S. Dahel 《统计学通讯:理论与方法》2013,42(3):601-606
885.
Luiz Antonio de Freitas 《统计学通讯:模拟与计算》2013,42(1):8-23
In this article, we consider the standard cure rate model proposed by Boag (1949) and Berkson and Gage (1952). We present a new definition of informative censoring similar to Lawless (1982) and the corresponding likelihood function. Under informative censoring, we obtain the Fisher information matrix of the exponential standard cure rate model. We verify, with simulated data, the impact caused by informative censoring in the coverage probabilities and in the lengths of asymptotic confidence intervals of the parameters of interest. An example with real data is analyzed. 相似文献
886.
Consider the general linear model Y = Xβ + ? , where E[??'] = σ2I and rank of X is less than or equal to the number of columns of X. It is well known that the linear parametric function λ'β is estimable if and only if λ' is in the row space of X. This paper characterizes all orthogonal matrices P such that the row space of XP is equal to the row space of X, i.e. the estimability of λ'β is invariant under P. An additional property of these matrices is the invariance of the spectrum of the information matrix X'X. An application of the results is also given. 相似文献
887.
The Azzalini [A. Azzalini, A class of distributions which includes the normal ones, Scandi. J. Statist. 12 (1985), pp. 171–178.] skew normal model can be viewed as one involving normal components subject to a single linear constraint. As a natural extension of this model, we discuss skewed models involving multiple linear and nonlinear constraints and possibly non-normal components. Particular attention is devoted to a distribution called the extended two-piece normal (ETN) distribution. This model is a two-constraint extension of the two-piece normal model introduced by Kim [H.J. Kim, On a class of two-piece skew normal distributions, Statistics 39(6) (2005), pp. 537–553.]. Likelihood inference for the ETN distribution is developed and illustrated using two data sets. 相似文献
888.
For the first time, a new five-parameter distribution, called the beta generalized gamma distribution, is introduced and studied. It contains at least 25 special sub-models such as the beta gamma, beta Weibull, beta exponential, generalized gamma (GG), Weibull and gamma distributions and thus could be a better model for analysing positive skewed data. The new density function can be expressed as a linear combination of GG densities. We derive explicit expressions for moments, generating function and other statistical measures. The elements of the expected information matrix are provided. The usefulness of the new model is illustrated by means of a real data set. 相似文献
889.
本文着重论述了信息化时代重视国家和地区创新的意义,指明了创新是一个复杂过程,需要运用复杂性理论,强调了学习与知识共享、改变思维方式和建立良好文化氛围对创新的重要性。 相似文献
890.
辉煌的成就和切肤的创痛是20世纪以来人类社会发展的真实写照。基于对传统社会经济发展模式及其历程的反思,人类的惯性思维范式随着关于社会的科学知识的累积与更新发生了转变,人类开始重新思考自然客体的价值所在,日益关注自然客体生态价值的保护。应自然客体价值拓展而转型的环境资源法律制度强调尊重自然生态规律,要求变革资源利用方式,扩大对自然资本的投资,并通过建立适当的利益引导机制,保护和改善生态环境,实现自然资源的持续利用。 相似文献