全文获取类型
收费全文 | 1225篇 |
免费 | 166篇 |
国内免费 | 55篇 |
专业分类
化学 | 107篇 |
力学 | 66篇 |
综合类 | 39篇 |
数学 | 766篇 |
物理学 | 468篇 |
出版年
2024年 | 2篇 |
2023年 | 28篇 |
2022年 | 40篇 |
2021年 | 46篇 |
2020年 | 62篇 |
2019年 | 43篇 |
2018年 | 44篇 |
2017年 | 48篇 |
2016年 | 53篇 |
2015年 | 27篇 |
2014年 | 67篇 |
2013年 | 96篇 |
2012年 | 43篇 |
2011年 | 58篇 |
2010年 | 43篇 |
2009年 | 80篇 |
2008年 | 90篇 |
2007年 | 82篇 |
2006年 | 80篇 |
2005年 | 62篇 |
2004年 | 66篇 |
2003年 | 33篇 |
2002年 | 38篇 |
2001年 | 46篇 |
2000年 | 26篇 |
1999年 | 37篇 |
1998年 | 25篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1971年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有1446条查询结果,搜索用时 203 毫秒
81.
This paper is devoted to constructing an authentication code with arbitration using subspaces of vector spaces over finite fields.Moreover,if we choose the encoding rules of the transmitter and the decoding rules of the receiver according to a uniform probability distribution,then some parameters and the probabilities of successful attacks are computed. 相似文献
82.
Mikhail Elyashberg Kirill Blinov Yegor Smurnyy Tatiana Churanova Antony Williams 《Magnetic resonance in chemistry : MRC》2010,48(3):219-229
The accuracy of 13C chemical shift prediction by both DFT GIAO quantum‐mechanical (QM) and empirical methods was compared using 205 structures for which experimental and QM‐calculated chemical shifts were published in the literature. For these structures, 13C chemical shifts were calculated using HOSE code and neural network (NN) algorithms developed within our laboratory. In total, 2531 chemical shifts were analyzed and statistically processed. It has been shown that, in general, QM methods are capable of providing similar but inferior accuracy to the empirical approaches, but quite frequently they give larger mean average error values. For the structural set examined in this work, the following mean absolute errors (MAEs) were found: MAE(HOSE) = 1.58 ppm, MAE(NN) = 1.91 ppm and MAE(QM) = 3.29 ppm. A strategy of combined application of both the empirical and DFT GIAO approaches is suggested. The strategy could provide a synergistic effect if the advantages intrinsic to each method are exploited. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
83.
The problem of finding dominators in a directed graph has many important applications, notably in global optimization of computer code. Although linear and near-linear-time algorithms exist, they use sophisticated data structures. We develop an algorithm for finding dominators that uses only a “static tree” disjoint set data structure in addition to simple lists and maps. The algorithm runs in near-linear or linear time, depending on the implementation of the disjoint set data structure. We give several versions of the algorithm, including one that computes loop nesting information (needed in many kinds of global code optimization) and that can be made self-certifying, so that the correctness of the computed dominators is very easy to verify. 相似文献
84.
85.
86.
针对量子系统的联合消相干模型,可以找到一些不受消相干错误影响的系统状态,这种状态被称为相干保持态,所有相干保持态构成的空间就称为无消相干子空间(decoherencefreesubspace,缩写为DFS).利用DFS的特性可以实现自动容错的量子避错码.首先提出一种DFS的定义,并且以定理的形式证明其他DFS的定义都是等价的.然后给出了DFS的存在性定理.最后利用群论的方法设计一种构造DFS的简单方法
关键词:
相干保持态
无消相干子空间
量子避错码
容错量子计算 相似文献
87.
88.
本文从符号学的角度来分析城市家具的设计,是对设计如何满足现代社会发展需求的探索,从功能到符号,从符号到设计,设计不再是绘画的附属,而是建立符号系统的过程. 相似文献
89.
整表代数是群代数的推广,它的理想是群代数码的推广.本文给出了整表代数的单边理想是自正交理想的必要充分条件. 相似文献
90.
Hans Georg Schaathun 《Designs, Codes and Cryptography》2004,31(1):27-42
A greedy 1-subcode is a one-dimensional subcode of minimum (support) weight. A greedy r-subcode is an r-dimensional subcode with minimum support weight under the constraint that it contain a greedy (r - 1)-subcode. The r-th greedy weight e
r is the support weight of a greedy r-subcode. The greedy weights are related to the weight hierarchy. We use recent results on the weight hierarchy of product codes to develop a lower bound on the greedy weights of product codes. 相似文献