全文获取类型
收费全文 | 3358篇 |
免费 | 113篇 |
国内免费 | 9篇 |
出版年
2021年 | 43篇 |
2019年 | 89篇 |
2018年 | 53篇 |
2017年 | 83篇 |
2016年 | 82篇 |
2015年 | 68篇 |
2014年 | 83篇 |
2013年 | 719篇 |
2012年 | 36篇 |
2011年 | 33篇 |
2010年 | 49篇 |
2009年 | 57篇 |
2008年 | 65篇 |
2007年 | 72篇 |
2006年 | 47篇 |
2005年 | 50篇 |
2004年 | 60篇 |
2003年 | 46篇 |
2002年 | 64篇 |
2001年 | 40篇 |
2000年 | 38篇 |
1999年 | 48篇 |
1998年 | 56篇 |
1997年 | 54篇 |
1996年 | 67篇 |
1995年 | 47篇 |
1994年 | 61篇 |
1993年 | 68篇 |
1992年 | 61篇 |
1991年 | 40篇 |
1986年 | 73篇 |
1985年 | 66篇 |
1984年 | 36篇 |
1983年 | 42篇 |
1982年 | 44篇 |
1981年 | 45篇 |
1980年 | 51篇 |
1979年 | 45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 |
排序方式: 共有3480条查询结果,搜索用时 265 毫秒
981.
982.
T.C. Edwin Cheng Qing Ding Mikhail Y. Kovalyov Aleksander Bachman Adam Janiak 《海军后勤学研究》2003,50(6):531-554
We study the problems of scheduling a set of nonpreemptive jobs on a single or multiple machines without idle times where the processing time of a job is a piecewise linear nonincreasing function of its start time. The objectives are the minimization of makespan and minimization of total job completion time. The single machine problems are proved to be NP‐hard, and some properties of their optimal solutions are established. A pseudopolynomial time algorithm is constructed for makespan minimization. Several heuristics are derived for both total completion time and makespan minimization. Computational experiments are conducted to evaluate their efficiency. NP‐hardness proofs and polynomial time algorithms are presented for some special cases of the parallel machine problems. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 531–554, 2003 相似文献
983.
984.
G. Levitin 《海军后勤学研究》2003,50(4):322-344
Weighted voting classifiers considered in this paper consist of N units each providing individual classification decisions. The entire system output is based on tallying the weighted votes for each decision and choosing the one which has total support weight exceeding a certain threshold. Each individual unit may abstain from voting. The entire system may also abstain from voting if no decision support weight exceeds the threshold. Existing methods of evaluating the reliability of weighted voting systems can be applied to limited special cases of these systems and impose some restrictions on their parameters. In this paper a universal generating function method is suggested which allows the reliability of weighted voting classifiers to be exactly evaluated without imposing constraints on unit weights. Based on this method, the classifier reliability is determined as a function of a threshold factor, and a procedure is suggested for finding the threshold which minimizes the cost of damage caused by classifier failures (misclassification and abstention may have different price.) Dynamic and static threshold voting rules are considered and compared. A method of analyzing the influence of units' availability on the entire classifier reliability is suggested, and illustrative examples are presented. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 322–344, 2003. 相似文献
985.
研究了一种基于高阶累积量和神经网络的干扰识别算法。该方法把卫星通信中常见的各种干扰信号的归一化高阶累积量作为分类特征参数,应用神经网络对特征参数进行分类训练,将接收干扰信号的归一化高阶累积量输入已训练的神经网络进行干扰类型的识别。试验结果表明:该算法在低干信比的情况下具有较高的识别准确率。 相似文献
986.
推导得到了宽带 MIMO-OFDM 信道模型。在空间相关情况下推导了非盲信道估计的 Bayesian CRB及 Bayesian MMSE。利用 Bayesian CRB 准则对发送的训练序列进行了功率分配,而后利用一种线性规划的方法对带有保护带宽 MIMO-OFDM 训练符号进行子载波功率分配,并利用发端酉矩阵进行最优相位设计。 相似文献
987.
In this article, we introduce the capacitated warehouse location model with risk pooling (CLMRP), which captures the interdependence between capacity issues and the inventory management at the warehouses. The CLMRP models a logistics system in which a single plant ships one type of product to a set of retailers, each with an uncertain demand. Warehouses serve as the direct intermediary between the plant and the retailers for the shipment of the product and also retain safety stock to provide appropriate service levels to the retailers. The CLMRP minimizes the sum of the fixed facility location, transportation, and inventory carrying costs. The model simultaneously determines warehouse locations, shipment sizes from the plant to the warehouses, the working inventory, and safety stock levels at the warehouses and the assignment of retailers to the warehouses. The costs at each warehouse exhibit initially economies of scale and then an exponential increase due to the capacity limitations. We show that this problem can be formulated as a nonlinear integer program in which the objective function is neither concave nor convex. A Lagrangian relaxation solution algorithm is proposed. The Lagrangian subproblem is also a nonlinear integer program. An efficient algorithm is developed for the linear relaxation of this subproblem. The Lagrangian relaxation algorithm provides near‐optimal solutions with reasonable computational requirements for large problem instances. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008 相似文献
988.
Stephen D. Wrage 《Defense & Security Analysis》2003,19(2):101-109
989.
990.
自美国2002初年公布《核态势评估》,表示要削减战略核武器数量,要建立新三位一体的核威慑力量始,美国即尝试对核武器综合体进行改造。美国国家核安全局2008年10月正式公布核武器综合体转型计划。转型计划提出削减核武器综合体规模,建立新的科学与工业设施,某些重要设施采取分离式布局,防止恐怖主义袭击。核武器综合体转型将为美国建立更加灵活、快速反应的核威慑力量,同时也动摇了不扩散核武器机制。 相似文献