首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4621篇
  免费   137篇
  国内免费   25篇
管理学   427篇
民族学   11篇
人口学   80篇
丛书文集   91篇
理论方法论   108篇
综合类   773篇
社会学   256篇
统计学   3037篇
  2024年   1篇
  2023年   30篇
  2022年   33篇
  2021年   49篇
  2020年   77篇
  2019年   127篇
  2018年   182篇
  2017年   256篇
  2016年   142篇
  2015年   146篇
  2014年   163篇
  2013年   1017篇
  2012年   342篇
  2011年   197篇
  2010年   174篇
  2009年   193篇
  2008年   196篇
  2007年   191篇
  2006年   173篇
  2005年   173篇
  2004年   140篇
  2003年   131篇
  2002年   91篇
  2001年   93篇
  2000年   83篇
  1999年   62篇
  1998年   57篇
  1997年   44篇
  1996年   24篇
  1995年   20篇
  1994年   30篇
  1993年   18篇
  1992年   21篇
  1991年   14篇
  1990年   13篇
  1989年   10篇
  1988年   13篇
  1987年   8篇
  1986年   6篇
  1985年   8篇
  1984年   7篇
  1983年   10篇
  1982年   8篇
  1981年   1篇
  1980年   2篇
  1979年   2篇
  1978年   3篇
  1977年   1篇
  1976年   1篇
排序方式: 共有4783条查询结果,搜索用时 15 毫秒
61.
本文分析了传统FAGM(1,1)模型建模过程中存在的误差,提出了一种基于Simpson公式改进的FAGM(1,1)模型。首先,基于分数阶累加生成算子和分数阶累减生成算子建立分数阶FAGM(1,1)模型。其次,利用Simpson积分公式对FAGM(1,1)模型的背景值进行改进,建立SFAGM(1,1)模型。进一步,应用遗传算法确定SFAGM(1,1)模型的最优阶数以提高模型的预测精度。最后,以中国人均GDP为例,对比分析GM(1,1)模型、Simpson改进的GM(1,1)模型(SGM(1,1))、FAGM(1,1)模型、SFAGM(1,1)模型的模拟结果,并对"十三五"时期的人均GDP进行预测,其结果表明SFAGM(1,1)模型比GM(1,1)、SGM(1,1)、FAGM(1,1)在人均GDP的预测方面有更高的精度,"十三五"期间人均GDP年平均增长率为10.64%,到2020年达到83146.97元,是2010年人均GDP的2.69倍,以2010年的人均GDP为基准,到2020年将能够实现翻一番的目标。  相似文献   
62.
63.
对45个试验点的资料分析,多抗、丰产、优质、广适小麦新品种绵阳26的主要性状有效穗x1、穗粒数x2和千粒x3、单穗重x4与产量y的回归方程为:y=-614.8425+9.8683x1+7.3223x2+10.5315x3+22.5748x4。经偏回归和偏相关分析,产量构成因素中,千粒重、有效穗对绵阳26产量的贡献和影响最大(b'3=1.7435,b'1=1.5372,R3y.=0.7983,R1y=0.6991)。在现有产量的基础上稳定千粒重,主攻穗数和穗粒数,是发挥绵阳26高产潜力的决定因素。  相似文献   
64.
Several authors have contributed to what can now be considered a rather complete theory for analysis of variance in cases with orthogonal factors. By using this theory on an assumed basic reference population, the orthogonality concept gives a natural definition of independence between factors in the population. By looking upon the treated units in designed experiments as a formal sample from a future population about which we want to make inference, a natural parametrization of expectations and variances connected to such experiments arises. This approach seems to throw light upon several controversial questions in the theory of mixed models. Also, it gives a framework for discussing the choice of conditioning in models  相似文献   
65.
Generalized Leverage and its Applications   总被引:2,自引:0,他引:2  
The generalized leverage of an estimator is defined in regression models as a measure of the importance of individual observations. We derive a simple but powerful result, developing an explicit expression for leverage in a general M -estimation problem, of which the maximum likelihood problems are special cases. A variety of applications are considered, most notably to the exponential family non-linear models. The relationship between leverage and local influence is also discussed. Numerical examples are given to illustrate our results  相似文献   
66.
A Multivariate Model for Repeated Failure Time Measurements   总被引:1,自引:1,他引:0  
A parametric multivariate failure time distribution is derived from a frailty-type model with a particular frailty distribution. It covers as special cases certain distributions which have been used for multivariate survival data in recent years. Some properties of the distribution are derived: its marginal and conditional distributions lie within the parametric family, and association between the component variates can be positive or, to a limited extent, negative. The simple closed form of the survivor function is useful for right-censored data, as occur commonly in survival analysis, and for calculating uniform residuals. Also featured is the distribution of ratios of paired failure times. The model is applied to data from the literature  相似文献   
67.
A common problem in environmental epidemiology is the estimation and mapping of spatial variation in disease risk. In this paper we analyse data from the Walsall District Health Authority, UK, concerning the spatial distributions of cancer cases compared with controls sampled from the population register. We formulate the risk estimation problem as a nonparametric binary regression problem and consider two different methods of estimation. The first uses a standard kernel method with a cross-validation criterion for choosing the associated bandwidth parameter. The second uses the framework of the generalized additive model (GAM) which has the advantage that it can allow for additional explanatory variables, but is computationally more demanding. For the Walsall data, we obtain similar results using either the kernel method with controls stratified by age and sex to match the age–sex distribution of the cases or the GAM method with random controls but incorporating age and sex as additional explanatory variables. For cancers of the lung or stomach, the analysis shows highly statistically significant spatial variation in risk. For the less common cancers of the pancreas, the spatial variation in risk is not statistically significant.  相似文献   
68.
Organizational innovation is essential to economic development. But, the way successful societies have organized new ventures has been remarkably similar in both past and present. The commenda organizations of medieval Italy shared many characteristics with modern startups that are financed by venture capital. Profit share contracts; limited liability and periodic reevaluations are cases in point. Agency contracts in both types of ventures are designed to absorb the high uncertainty inherent to these enterprises through risk sharing. Uncertainty prohibits a unique ex ante ranking order of investment projects and prompts investors to look for hidden human capital. Equity finance is better equipped to even out unexpected losses and gains that are inherent to uncertainty than debt finance.  相似文献   
69.
金融工程中资产收益的连续时间模型评述   总被引:3,自引:2,他引:3  
总结了在过去30年中金融资产收益连续时间模型的发展及主要成果,讨论了迄今连续时间模型参数估计的主要方法,其中特别讨论了MCMC方法;最后指出了现在和未来该领域研究所面临的主要课题。  相似文献   
70.
基于MCMC稳态模拟的贝叶斯经验费率厘定信用模型   总被引:2,自引:2,他引:2  
B黨lmann-Straub model is one of the most famous applications of the Bayesian method for the experience rate making.However,by the traditional B黨lmann-Straub model one cannot get the unbiased posterior estimation of the parameters when there is not sufficient prior information for the structural parameters;What's more,the difficult of computing high dimension numeration limits the application of Bayesian method.This paper introduces the Markov chain Monte Carlo simulaton method based on the Gibbs sampling after analyzing the structure of the B黨lmann-Straub model and sets up the Bayesian credibility model for estimating the predictive risk premium.Also by using the results of the numeration analysis,this paper proves that from this model one can get the posterior distributions of the parameters dynamically and the posterior estimation of the censoring parameters in the situation that exists unknown parameters,as well as improve the precision of the numeration,which can be helpful to find the heterogeneity of the premium.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号