全文获取类型
| 收费全文 | 11861篇 |
| 免费 | 39篇 |
专业分类
| 管理学 | 1732篇 |
| 民族学 | 53篇 |
| 人才学 | 1篇 |
| 人口学 | 1192篇 |
| 丛书文集 | 60篇 |
| 教育普及 | 1篇 |
| 理论方法论 | 989篇 |
| 现状及发展 | 1篇 |
| 综合类 | 137篇 |
| 社会学 | 5466篇 |
| 统计学 | 2268篇 |
出版年
| 2023年 | 96篇 |
| 2021年 | 67篇 |
| 2020年 | 198篇 |
| 2019年 | 250篇 |
| 2018年 | 268篇 |
| 2017年 | 365篇 |
| 2016年 | 304篇 |
| 2015年 | 190篇 |
| 2014年 | 253篇 |
| 2013年 | 1968篇 |
| 2012年 | 402篇 |
| 2011年 | 328篇 |
| 2010年 | 269篇 |
| 2009年 | 258篇 |
| 2008年 | 289篇 |
| 2007年 | 273篇 |
| 2006年 | 255篇 |
| 2005年 | 259篇 |
| 2004年 | 252篇 |
| 2003年 | 215篇 |
| 2002年 | 245篇 |
| 2001年 | 287篇 |
| 2000年 | 291篇 |
| 1999年 | 272篇 |
| 1998年 | 184篇 |
| 1997年 | 180篇 |
| 1996年 | 165篇 |
| 1995年 | 165篇 |
| 1994年 | 134篇 |
| 1993年 | 152篇 |
| 1992年 | 169篇 |
| 1991年 | 150篇 |
| 1990年 | 157篇 |
| 1989年 | 182篇 |
| 1988年 | 155篇 |
| 1987年 | 138篇 |
| 1986年 | 152篇 |
| 1985年 | 174篇 |
| 1984年 | 169篇 |
| 1983年 | 159篇 |
| 1982年 | 124篇 |
| 1981年 | 107篇 |
| 1980年 | 103篇 |
| 1979年 | 140篇 |
| 1978年 | 88篇 |
| 1977年 | 87篇 |
| 1976年 | 87篇 |
| 1975年 | 80篇 |
| 1974年 | 80篇 |
| 1973年 | 73篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
211.
In life-testing and survival analysis, sometimes the components are arranged in series or parallel system and the number of components is initially unknown. Thus, the number of components, say Z, is considered as random with an appropriate probability mass function. In this paper, we model the survival data with baseline distribution as Weibull and the distribution of Z as generalized Poisson, giving rise to four parameters in the model: increasing, decreasing, bathtub and upside bathtub failure rates. Two examples are provided and the maximum-likelihood estimation of the parameters is studied. Rao's score test is developed to compare the results with the exponential Poisson model studied by Kus [17] and the exponential-generalized Poisson distribution with baseline distribution as exponential and the distribution of Z as generalized Poisson. Simulation studies are carried out to examine the performance of the estimates. 相似文献
212.
Jelani Wiltshire Fred W. Huffer William C. Parker 《Journal of applied statistics》2014,41(9):2028-2043
Van Valen's Red Queen hypothesis states that within a homogeneous taxonomic group the age is statistically independent of the rate of extinction. The case of the Red Queen hypothesis being addressed here is when the homogeneous taxonomic group is a group of similar species. Since Van Valen's work, various statistical approaches have been used to address the relationship between taxon age and the rate of extinction. We propose a general class of test statistics that can be used to test for the effect of age on the rate of extinction. These test statistics allow for a varying background rate of extinction and attempt to remove the effects of other covariates when assessing the effect of age on extinction. No model is assumed for the covariate effects. Instead we control for covariate effects by pairing or grouping together similar species. Simulations are used to compare the power of the statistics. We apply the test statistics to data on Foram extinctions and find that age has a positive effect on the rate of extinction. A derivation of the null distribution of one of the test statistics is provided in the supplementary material. 相似文献
213.
Outliers are commonly observed in psychosocial research, generally resulting in biased estimates when comparing group differences using popular mean-based models such as the analysis of variance model. Rank-based methods such as the popular Mann–Whitney–Wilcoxon (MWW) rank sum test are more effective to address such outliers. However, available methods for inference are limited to cross-sectional data and cannot be applied to longitudinal studies under missing data. In this paper, we propose a generalized MWW test for comparing multiple groups with covariates within a longitudinal data setting, by utilizing the functional response models. Inference is based on a class of U-statistics-based weighted generalized estimating equations, providing consistent and asymptotically normal estimates not only under complete but missing data as well. The proposed approach is illustrated with both real and simulated study data. 相似文献
214.
Joinpoint regression model identifies significant changes in the trends of the incidence, mortality, and survival of a specific disease in a given population. The purpose of the present study is to develop an age-stratified Bayesian joinpoint regression model to describe mortality trend assuming that the observed counts are probabilistically characterized by the Poisson distribution. The proposed model is based on Bayesian model selection criteria with the smallest number of joinpoints that are sufficient to explain the Annual Percentage Change. The prior probability distributions are chosen in such a way that they are automatically derived from the model index contained in the model space. The proposed model and methodology estimates the age-adjusted mortality rates in different epidemiological studies to compare the trends by accounting the confounding effects of age. In developing the subject methods, we use the cancer mortality counts of adult lung and bronchus cancer, and brain and other Central Nervous System cancer patients obtained from the Surveillance Epidemiology and End Results data base of the National Cancer Institute. 相似文献
215.
In this paper, we show that a hypergeometric random variable can be represented as a sum of independent Bernoulli random variables that are, except in degenerate cases, not identically distributed. In the proof, we use the factorial moment generating function. An asymptotic result on the probabilities of the Bernoulli random variables in the sum is also presented. Numerical examples are used to illustrate the results. 相似文献
216.
In this article, the authors first obtain the exact distribution of the logarithm of the product of independent generalized Gamma r.v.’s (random variables) in the form of a Generalized Integer Gamma distribution of infinite depth, where all the rate and shape parameters are well identified. Then, by a routine transformation, simple and manageable expressions for the exact distribution of the product of independent generalized Gamma r.v.’s are derived. The method used also enables us to obtain quite easily very accurate, manageable and simple near-exact distributions in the form of Generalized Near-Integer Gamma distributions. Numerical studies are carried out to assess the precision of different approximations to the exact distribution and they show the high accuracy of the approximations provided by the near-exact distributions. As particular cases of the exact distributions obtained we have the distribution of the product of independent Gamma, Weibull, Frechet, Maxwell-Boltzman, Half-Normal, Rayleigh, and Exponential distributions, as well as the exact distribution of the generalized variance, the exact distribution of discriminants or Vandermonde determinants and the exact distribution of any linear combination of generalized Gumbel distributions, as well as yet the distribution of the product of any power of the absolute value of independent Normal r.v.’s. 相似文献
217.
218.
Raul O. Chao Kenneth C. Lichtendahl Yael Grushka‐Cockayne 《Production and Operations Management》2014,23(8):1286-1298
Many large organizations use a stage‐gate process to manage new product development projects. In a typical stage‐gate process project managers learn about potential ideas from research and exert effort in development while senior executives make intervening go/no‐go decisions. This decentralized decision making results in an agency problem because the idea quality in early stages is unknown to the executive and the project manager must exert unobservable development effort in later stages. In light of these challenges, how should the firm structure incentives to ensure that project managers reveal relevant information and invest the appropriate effort to create value? In this study, we develop a model of adverse selection in research and moral hazard in development with a go/no‐go decision at the intervening gate. Our results show that the principal's uncertainty regarding early‐stage idea quality—a term we refer to as idea risk—alters the effect of late‐stage development risk. The presence of idea risk can alter the incentives offered to the agent and may lead the principal to reject projects that otherwise seem favorable in terms of positive net present value. A simulation of early‐stage ideas, found through search on a complex landscape, shows that the firm can mitigate the negative effects of idea risk by encouraging breadth of search and high tolerance for failure. 相似文献
219.
This paper provides a contemporary and comprehensive review of work in the marketing channel field that is based on French and Raven's power‐base theory. It traces the development of theoretic, conceptual and methodological orthodoxies from the 1970s. Mirroring the movement towards the relationship marketing paradigm, the paper considers the theory's empirical contribution to knowledge of power, conflict, trust and commitment in marketing channels. Limitations relating to inconsistency of treatment, contradictory findings and the simplification of complex phenomena are identified. Nevertheless, current work extends power‐base theory to other cultures, other styles of research and to the area of supply chains. The review raises questions about the value of contribution made using this theory and notes the surprising absence within the channels literature of the broader, current debate about power. To illustrate, the paper shows how Clegg's (1989. Frameworks of Power. London: Sage) circuits of power framework, if applied to channel contexts, could address forms of power that are invisible, anonymous and not necessarily negative. Applications and methods are discussed, opening a space wherein a broadened understanding of power is integrated within a focus upon cooperative channels. 相似文献
220.
Samuel Bowles Glenn C. Loury Rajiv Sethi 《Journal of the European Economic Association》2014,12(1):129-152
We explore the combined effect of segregation in social networks, peer effects, and the relative size of a historically disadvantaged group on the incentives to invest in market‐rewarded skills and the dynamics of inequality between social groups. We identify conditions under which group inequality will persist in the absence of differences in ability, credit constraints, or labor market discrimination. Under these conditions, group inequality may be amplified even if initial group differences are negligible. Increases in social integration may destabilize an unequal state and make group equality possible, but the distributional and human capital effects of this depend on the demographic composition of the population. When the size of the initially disadvantaged group is sufficiently small, integration can lower the long‐run costs of human capital investment in both groups and result in an increase the aggregate skill share. In contrast, when the initially disadvantaged group is large, integration can induce a fall in the aggregate skill share as the costs of human capital investment rise in both groups. We consider applications to concrete cases and policy implications. 相似文献