全文获取类型
收费全文 | 11708篇 |
免费 | 1109篇 |
国内免费 | 742篇 |
专业分类
电工技术 | 548篇 |
技术理论 | 1篇 |
综合类 | 1601篇 |
化学工业 | 1486篇 |
金属工艺 | 348篇 |
机械仪表 | 885篇 |
建筑科学 | 472篇 |
矿业工程 | 188篇 |
能源动力 | 960篇 |
轻工业 | 582篇 |
水利工程 | 728篇 |
石油天然气 | 777篇 |
武器工业 | 157篇 |
无线电 | 1121篇 |
一般工业技术 | 919篇 |
冶金工业 | 399篇 |
原子能技术 | 181篇 |
自动化技术 | 2206篇 |
出版年
2024年 | 57篇 |
2023年 | 168篇 |
2022年 | 311篇 |
2021年 | 358篇 |
2020年 | 357篇 |
2019年 | 359篇 |
2018年 | 310篇 |
2017年 | 368篇 |
2016年 | 431篇 |
2015年 | 453篇 |
2014年 | 583篇 |
2013年 | 698篇 |
2012年 | 797篇 |
2011年 | 803篇 |
2010年 | 678篇 |
2009年 | 741篇 |
2008年 | 731篇 |
2007年 | 713篇 |
2006年 | 756篇 |
2005年 | 597篇 |
2004年 | 522篇 |
2003年 | 460篇 |
2002年 | 343篇 |
2001年 | 290篇 |
2000年 | 249篇 |
1999年 | 255篇 |
1998年 | 195篇 |
1997年 | 161篇 |
1996年 | 116篇 |
1995年 | 112篇 |
1994年 | 125篇 |
1993年 | 85篇 |
1992年 | 76篇 |
1991年 | 66篇 |
1990年 | 57篇 |
1989年 | 41篇 |
1988年 | 28篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 4篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1964年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Consideration was given to the inventory control by the criterion for minimum of the cumulative mean costs over a sufficiently long planning horizon in conditions of uncertain demand characteristics. Adaptive algorithms to estimate the parameters of the optimal two-level control policies oriented to the supply systems with high level of customer servicing were constructed for the stationary mode of operation. 相似文献
62.
A. N. Zhirabok 《Automation and Remote Control》2008,69(6):1051-1064
Consideration was given to construction of the parity relations for systems described by the nonlinear dynamic models. To solve this problem, a logic-dynamic approach was proposed, and the realizability conditions providing insensitivity to the perturbing actions were given for it. 相似文献
63.
将遗传算法与神经网络相结合,提出一种实数编码、自适应选择、算术交叉、高斯变异、爬山操作的改进遗传BP神经网络RCGNN,利用遗传算法对神经网络权值和阈值进行优化。以时间序列预测的实例进行编程计算表明,用遗传算法进行网络训练,其收敛速度快,最终总误差最小,预测准确率高。对算法中参数进行的相应研究表明,增加爬山操作次数能很好地提高网络训练的速度,同时使误差下降快;爬山操作越多,收敛速度越快,最终误差越小,但计算运行时间也会增加。 相似文献
64.
65.
We give drawings of a complete graphK
n
withO(n
4 log2
g/g) many crossings on an orientable or nonorientable surface of genusg 2. We use these drawings ofK
n
and give a polynomial-time algorithm for drawing any graph withn vertices andm edges withO(m
2 log2
g/g) many crossings on an orientable or nonorientable surface of genusg 2. Moreover, we derive lower bounds on the crossing number of any graph on a surface of genusg 0. The number of crossings in the drawings produced by our algorithm are within a multiplicative factor ofO(log2
g) from the lower bound (and hence from the optimal) for any graph withm 8n andn
2/m g m/64.The research of the third and the fourth authors was partially supported by Grant No. 2/1138/94 of the Slovak Academy of Sciences and by EC Cooperative action IC1000 Algorithms for Future Technologies (Project ALTEC). A preliminary version of this paper was presented at WG93 and published in Lecture Notes in Computer Science, Vol. 790, 1993, pp. 388–396. 相似文献
66.
这里提出了一种基于椭圆曲线公钥密码算法的序列号生成方案,结合签名技术,可以防止敌手代码被篡改或者跳过某些重要代码,因此该方案构成一种安全有效的软件保护方案,最后分析了该方案的安全性,并进行了方案的有效性实验. 相似文献
67.
针对高脉冲重复雷达距离模糊问题,提出一种新的混合滤波解距离模糊方法.通过把脉冲间隔数和脉冲间隔变化量作为目标待估计状态,对离散的脉冲间隔数、间隔变化量和连续的目标状态(位置和速度)进行混合滤波,从而将解距离模糊问题转换为对脉冲间隔数的估计问题.初始时刻,由于距离量测模糊,利用多个高脉冲重复频率(HPRF)采用欧氏距离对混合状态进行初始化.在滤波过程中,为了避免门限选择,首先根据脉冲间隔变化量的有限个离散取值,将六维向量的混合滤波模型等效为有限个五维向量的混合滤波模型;然后对量测分别进行混合滤波;最后通过对各模型得到的新息的2范数进行比较获得混合状态估计,从而实现解距离模糊.混合滤波解距离模糊方法为实现高脉冲重复频率雷达实时解距离模糊提供了一种新的研究思路,仿真结果表明,本文提出的混合滤波方法在只有一个脉冲重复频率获得目标量测时较现有多假设方法收敛速度快,并且可以克服多假设方法在脉冲间隔数变化时发生的解模糊错误. 相似文献
68.
Let γ(G) denote the domination number of a digraph G and let Cm□Cn denote the Cartesian product of Cm and Cn, the directed cycles of length m,n?2. In this paper, we determine the exact values: γ(C2□Cn)=n; γ(C3□Cn)=n if , otherwise, γ(C3□Cn)=n+1; if , otherwise, . 相似文献
69.
Andrew Zemke 《Information Processing Letters》2010,110(22):979-985
A k-ranking of a graph is a labeling of the vertices with positive integers 1,2,…,k so that every path connecting two vertices with the same label contains a vertex of larger label. An optimal ranking is one in which k is minimized. Let Pn be a path with n vertices. A greedy algorithm can be used to successively label each vertex with the smallest possible label that preserves the ranking property. We seek to show that when a greedy algorithm is used to label the vertices successively from left to right, we obtain an optimal ranking. A greedy algorithm of this type was given by Bodlaender et al. in 1998 [1] which generates an optimal k-ranking of Pn. In this paper we investigate two generalizations of rankings. We first consider bounded (k,s)-rankings in which the number of times a label can be used is bounded by a predetermined integer s. We then consider kt-rankings where any path connecting two vertices with the same label contains t vertices with larger labels. We show for both generalizations that when G is a path, the analogous greedy algorithms generate optimal k-rankings. We then proceed to quantify the minimum number of labels that can be used in these rankings. We define the bounded rank number to be the smallest number of labels that can be used in a (k,s)-ranking and show for n?2, where i=⌊log2(s)⌋+1. We define the kt-rank number, to be the smallest number of labels that can be used in a kt-ranking. We present a recursive formula that gives the kt-rank numbers for paths, showing for all an−1<j?an where {an} is defined as follows: a1=1 and an=⌊((t+1)/t)an−1⌋+1. 相似文献
70.
Yao-Tien Chen Author Vitae 《Pattern recognition》2010,43(11):3699-3711
This paper proposes an alternative criterion derived from the Bayesian risk classification error for image segmentation. The proposed model introduces a region-based force determined through the difference of the posterior image densities for the different classes, a term based on the prior probability derived from Kullback-Leibler information number, and a regularity term adopted to avoid the generation of excessively irregular and small segmented regions. Compared with other level set methods, the proposed approach relies on the optimum decision of pixel classification and the estimates of prior probabilities; thus the approach has more reliability in theory and practice. Experiments show that the proposed approach is able to extract the complicated shapes of targets and robust for various types of medical images. Moreover, the algorithm can be easily extendable for multiphase segmentation. 相似文献