全文获取类型
收费全文 | 2370篇 |
免费 | 230篇 |
国内免费 | 106篇 |
专业分类
化学 | 147篇 |
力学 | 24篇 |
综合类 | 49篇 |
数学 | 1158篇 |
物理学 | 230篇 |
无线电 | 1098篇 |
出版年
2024年 | 3篇 |
2023年 | 23篇 |
2022年 | 64篇 |
2021年 | 52篇 |
2020年 | 70篇 |
2019年 | 70篇 |
2018年 | 51篇 |
2017年 | 84篇 |
2016年 | 82篇 |
2015年 | 69篇 |
2014年 | 145篇 |
2013年 | 196篇 |
2012年 | 146篇 |
2011年 | 140篇 |
2010年 | 137篇 |
2009年 | 138篇 |
2008年 | 176篇 |
2007年 | 182篇 |
2006年 | 137篇 |
2005年 | 100篇 |
2004年 | 105篇 |
2003年 | 90篇 |
2002年 | 74篇 |
2001年 | 68篇 |
2000年 | 49篇 |
1999年 | 48篇 |
1998年 | 45篇 |
1997年 | 21篇 |
1996年 | 31篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有2706条查询结果,搜索用时 20 毫秒
101.
《Discrete Mathematics》2023,346(1):113188
In this addendum we give a short and easy negative answer to the two questions raised in the original article. 相似文献
102.
9%-16.3% compared to other ALOHA-based tag anti-collision algorithms when the number of tags is 1 000. 相似文献
103.
The effect of a market factor on information flow between stocks using the minimal spanning tree 总被引:1,自引:0,他引:1
We empirically investigated the effects of market factors on the information flow created from N(N−1)/2 linkage relationships among stocks. We also examined the possibility of employing the minimal spanning tree (MST) method, which is capable of reducing the number of links to N−1. We determined that market factors carry important information value regarding information flow among stocks. Moreover, the information flow among stocks showed time-varying properties according to the changes in market status. In particular, we noted that the information flow increased dramatically during periods of market crises. Finally, we confirmed, via the MST method, that the information flow among stocks could be assessed effectively with the reduced linkage relationships among all links among stocks from the perspective of the overall market. 相似文献
104.
105.
针对股票软件中历史数据的特点.深入分析了B+树存储和线性表存储两种数据存储方案.这两种方案均能达到股票软件的应用要求,最后进一步从性能和资源耗费上对这两种方案进行了对比分析,指出了它们各自的优点与不足,对其他类似的设计具有很好的借鉴意义. 相似文献
106.
通过决策树算法建立了老年性痴呆病型病因判断模型。文中详细研究了决策树算法C5.0及其修正方法,之后通过对太原市1500例数据的分析借助决策树C5.0算法构建了老年性痴呆的判断模型,并对其进行了修正,得到具有实际指导意义的判别模型。 相似文献
107.
We consider Schrödinger operators on radial metric trees and prove Lieb–Thirring and Cwikel–Lieb–Rozenblum inequalities for their negative eigenvalues. The validity of these inequalities depends on the volume growth of the tree. We show that the bounds are valid in the endpoint case and reflect the correct order in the weak or strong coupling limit. 相似文献
108.
Adrien Joseph 《Random Structures and Algorithms》2011,39(2):247-274
We provide information about the asymptotic regimes for a homogeneous fragmentation of a finite set. We establish a phase transition for the asymptotic behavior of the shattering times, defined as the first instants when all the blocks of the partition process have cardinality less than a fixed integer. Our results may be applied to the study of certain random split trees. © 2010 Wiley Periodicals, Inc. Random Struct. Alg., 39, 247‐274, 2011 相似文献
109.
Based on the property analysis of interferential multispectral images, a novel compression algorithm of partial set partitioning in hierarchical trees (SPIHT) with classified weighted rate-distortion optimization is presented.After wavelet decomposition, partial SPIHT is applied to each zero tree independently by adaptively selecting one of three coding modes according to the probability of the significant coefficients in each bitplane.Meanwhile the interferential multispectral image is partitioned into two kinds of regions in terms of luminous intensity, and the rate-distortion slopes of zero trees are then lifted with classified weights according to their distortion contribution to the constructed spectrum.Finally a global ratedistortion optimization truncation is performed.Compared with the conventional methods, the proposed algorithm not only improves the performance in spatial domain but also reduces the distortion in spectral domain. 相似文献
110.
Joonmo Kim Mihaela Cardei Ionut Cardei Xiaohua Jia 《Journal of Global Optimization》2002,24(4):437-448
In this paper, we present the design of a Polynomial Time Approximation Scheme (PTAS) for the Grade of Service Steiner Minimum Tree (GOSST) problem, which is known to be NP-Complete. Previous research has focused on geometric analyses and different approximation algorithms have been designed. We propose a PTAS that provides a polynomial time, near-optimal solution with performance ratio 1+. The GOSST problem has some important applications. In network design, a fundamental issue for the physical construction of a network structure is the interconnection of many communication sites with the best choice of the connecting lines and the best allocation of the transmission capacities over these lines. Good solutions should provide paths with enough communication capacities between any two sites, with the least network construction costs. Also, the GOSST problem has applications in transportation, for road constructions and some potential uses in CAD in terms of interconnecting the elements on a plane to provide enough flux between any two elements. 相似文献