全文获取类型
收费全文 | 3083篇 |
免费 | 74篇 |
国内免费 | 1篇 |
出版年
2021年 | 37篇 |
2019年 | 89篇 |
2018年 | 51篇 |
2017年 | 80篇 |
2016年 | 78篇 |
2015年 | 67篇 |
2014年 | 72篇 |
2013年 | 713篇 |
2012年 | 46篇 |
2011年 | 48篇 |
2010年 | 55篇 |
2009年 | 47篇 |
2008年 | 68篇 |
2007年 | 60篇 |
2006年 | 45篇 |
2005年 | 43篇 |
2004年 | 56篇 |
2003年 | 42篇 |
2002年 | 57篇 |
2001年 | 34篇 |
2000年 | 31篇 |
1999年 | 41篇 |
1998年 | 47篇 |
1997年 | 49篇 |
1993年 | 25篇 |
1991年 | 34篇 |
1990年 | 24篇 |
1989年 | 31篇 |
1988年 | 22篇 |
1986年 | 70篇 |
1985年 | 64篇 |
1984年 | 36篇 |
1983年 | 42篇 |
1982年 | 43篇 |
1981年 | 45篇 |
1980年 | 51篇 |
1979年 | 46篇 |
1978年 | 49篇 |
1977年 | 45篇 |
1976年 | 45篇 |
1975年 | 46篇 |
1974年 | 52篇 |
1973年 | 50篇 |
1972年 | 52篇 |
1971年 | 43篇 |
1970年 | 40篇 |
1969年 | 40篇 |
1968年 | 34篇 |
1967年 | 33篇 |
1966年 | 27篇 |
排序方式: 共有3158条查询结果,搜索用时 328 毫秒
51.
52.
53.
54.
55.
56.
57.
Kyung Y. Jo 《海军后勤学研究》1984,31(2):265-274
In this article we consider a continuous-time Markov decision process with a denumerable state space and nonzero terminal rewards. We first establish the necessary and sufficient optimality condition without any restriction on the cost functions. The necessary condition is derived through the Pontryagin maximum principle and the sufficient condition, by the inherent structure of the problem. We introduce a dynamic programming approximation algorithm for the finite-horizon problem. As the time between discrete points decreases, the optimal policy of the discretized problem converges to that of the continuous-time problem in the sense of weak convergence. For the infinite-horizon problem, a successive approximation method is introduced as an alternative to a policy iteration method. 相似文献
58.
Multicollinearity and nonnormal errors are problems often encountered in the application of linear regression. Estimators are proposed for dealing with the simultaneous occurrence of both multicollinearity and nonnormality. These estimators are developed by combining biased estimation techniques with certain robust criteria. An iteratively reweighted least-squares procedure is used to compute the estimates. The performance of the combined estimators is studied empirically through Monte Carlo experiments structured according to factorial designs. With respect to a mean-squared-error criterion, the combined estimators are superior to ordinary least-squares, pure biased estimators, and pure robust estimators when multicollinearity and nonnormality are present. The loss in efficiency for the combined estimators relative to least squares is small when these problems do not occur. Some guidelines for the use of these combined estimators are given. 相似文献
59.
Multiechelon repairable-item provisioning systems are considered under a time-varying environment. Such conditions could arise, for example, in a military context where a shift from peacetime operation to wartime operation takes place; or, in a civilian setting where a public transit system decides to increase its hours of operation or frequency of service. Exact Markovian models, incorporating a finite population of repairable components and limited repair capacity (nonample service), are treated, with transient solutions obtained using the randomization technique. The exact models are compared with the approximate Dyna-METRIC model which assumes an infinite population of components and ample repair capacity. 相似文献
60.
Let X denote a random vector with a spherically symmetric distribution. The density of U = X'X, called a “generalized chi-square,” is derived for the noncentral case, when μ = E(X) ≠ 0. Explicit series representations are found in certain special cases including the “generalized spherical gamma,” the “generalized” Laplace and the Pearson type VII distributions. A simple geometrical representation of U is shown to be useful in generating random U variates. Expressions for moments and characteristic functions are also given. These densities occur in offset hitting probabilities. 相似文献