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   2602篇
  免费   40篇
管理学   417篇
民族学   21篇
人才学   1篇
人口学   213篇
丛书文集   23篇
理论方法论   219篇
综合类   24篇
社会学   1372篇
统计学   352篇
  2021年   13篇
  2020年   26篇
  2019年   30篇
  2018年   52篇
  2017年   66篇
  2016年   55篇
  2015年   34篇
  2014年   53篇
  2013年   487篇
  2012年   60篇
  2011年   88篇
  2010年   68篇
  2009年   61篇
  2008年   64篇
  2007年   87篇
  2006年   56篇
  2005年   68篇
  2004年   61篇
  2003年   63篇
  2002年   56篇
  2001年   44篇
  2000年   43篇
  1999年   39篇
  1998年   50篇
  1997年   55篇
  1996年   49篇
  1995年   51篇
  1994年   39篇
  1993年   48篇
  1992年   46篇
  1991年   45篇
  1990年   41篇
  1989年   31篇
  1988年   30篇
  1987年   35篇
  1986年   26篇
  1985年   32篇
  1984年   32篇
  1983年   39篇
  1982年   33篇
  1981年   30篇
  1980年   29篇
  1979年   26篇
  1978年   34篇
  1977年   17篇
  1976年   25篇
  1975年   20篇
  1974年   25篇
  1973年   10篇
  1971年   11篇
排序方式: 共有2642条查询结果,搜索用时 60 毫秒
61.
62.
63.
A set of Fortran-77 subroutines is described which compute a nonparametric density estimator expressed as a Fourier series. In addition, a subroutine is given for the estimation of a cumulative distribution. Performance measures are given based on samples from a Weibull distribution. Due to small size and modest space demands, these subroutines are easily implemented on most small computers.  相似文献   
64.
We describe novel, analytical, data-analysis, and Monte-Carlo-simulation studies of strongly heteroscedastic data of both small and wide range.Many different types of heteroscedasticity and fixed or variable weighting are incorporated through error-variance models.Attention is given to parameter bias determinations, evaluations of their significances, and to new ways to correct for bias.The error-variance models allow for both additive and independent power-law errors, and the power exponent is shown to be able to be well determined for typical physicalsciences data by the rapidly-converging, general-purpose, extended-least-squares program we use.The fitting and error-variance models are applied to both low-and high-heteroscedasticity situations, including single-response data from radioactive decay.Monte-Carlo simulations of data with similar parameters are used to evaluate the analytical models developed and the various minimization methods em-ployed, such as extended and generalized least squares.Logarithmic and inversion transformations are investigated in detail, and it is shown analytically and by simulations that exponential data with constant percentage errors can be logarithmically transformed to allow a simple parameter-bias-removal procedure.A more-general bias-reduction approach combining direct and inversion fitting is also developed.Distributions of fitting-model and error-variance-model parameters are shown to be typically non-normal, thus invalidating the usual estimates of parameter bias and precision.Errors in conventional confidence-interval estimates are quantified by comparison with accurate simulation results.  相似文献   
65.
This paper provides a fortran algorithm that can be used to compute the cdf of the product of two normal distribution random variables. We also give references that provide mathematical properties, tables, and applications of this distribution  相似文献   
66.
A stepwise variable selection procedure for multinomial discrimination is presented and discussed. Based upon the work of Kullback and Hills, stopping rules are proposed and illustrated for a set of data on communication buyer behavior.  相似文献   
67.
The quadratic discriminant function is commonly used for the two group classification problem when the covariance matrices in the two populations are substantially unequal. This procedure is optimal when both populations are multivariate normal with known means and covariance matrices. This study examined the robustness of the QDF to non-normality. Sampling experiments were conducted to estimate expected actual error rates for the QDF when sampling from a variety of non-normal distributions. Results indicated that the QDF was robust to non-normality except when the distributions were highly skewed, in which case relatively large deviations from optimal were observed. In all cases studied the average probabilities of misclassification were relatively stable while the individual population error rates exhibited considerable variability.  相似文献   
68.
Environmental variables have an important effect on the reliability of many products such as coatings and polymeric composites. Long-term prediction of the performance or service life of such products must take into account the probabilistic/stochastic nature of the outdoor weather. In this article, we propose a time series modeling procedure to model the time series data of daily accumulated degradation. Daily accumulated degradation is the total amount of degradation accrued within one day and can be obtained by using a degradation rate model for the product and the weather data. The fitted model of the time series can then be used to estimate the future distribution of cumulative degradation over a period of time, and to compute reliability measures such as the probability of failure. The modeling technique and estimation method are illustrated using the degradation of a solar reflector material. We also provide a method to construct approximate confidence intervals for the probability of failure.  相似文献   
69.
70.
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