全文获取类型
收费全文 | 6499篇 |
免费 | 444篇 |
国内免费 | 656篇 |
专业分类
化学 | 865篇 |
晶体学 | 6篇 |
力学 | 358篇 |
综合类 | 171篇 |
数学 | 5714篇 |
物理学 | 485篇 |
出版年
2024年 | 7篇 |
2023年 | 65篇 |
2022年 | 92篇 |
2021年 | 139篇 |
2020年 | 134篇 |
2019年 | 157篇 |
2018年 | 161篇 |
2017年 | 170篇 |
2016年 | 185篇 |
2015年 | 139篇 |
2014年 | 276篇 |
2013年 | 442篇 |
2012年 | 287篇 |
2011年 | 348篇 |
2010年 | 322篇 |
2009年 | 422篇 |
2008年 | 419篇 |
2007年 | 404篇 |
2006年 | 398篇 |
2005年 | 326篇 |
2004年 | 288篇 |
2003年 | 346篇 |
2002年 | 283篇 |
2001年 | 252篇 |
2000年 | 222篇 |
1999年 | 213篇 |
1998年 | 215篇 |
1997年 | 187篇 |
1996年 | 116篇 |
1995年 | 97篇 |
1994年 | 82篇 |
1993年 | 64篇 |
1992年 | 45篇 |
1991年 | 36篇 |
1990年 | 25篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 32篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 26篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有7599条查询结果,搜索用时 15 毫秒
41.
Alexander P. Schuster 《Proceedings of the American Mathematical Society》1997,125(6):1717-1725
Properties of the unions of sampling and interpolation sets for Bergman spaces are discussed in conjunction with the examples given by Seip (1993). Their relationship to the classical interpolation sequences is explored. In addition, the role played by canonical divisors in the study of these sets is examined and an example of a sampling set is constructed in the disk.
42.
本文给出了一个判定最大无关组的充要性定理及其证明.同时对用矩阵的行变换求最大无关组这一问题进行了点滴分析并介绍了一个解齐次线性方程组的简便方法。 相似文献
43.
Browder-Petryshyn 型的严格伪压缩映射的粘滞迭代逼近方法 总被引:1,自引:0,他引:1
主要研究Browder-Petryshyn型的严格伪压缩映射的粘滞迭代逼近过程,证明了Browder-Petryshyn型的严格伪压缩映射的不动点集F(T)是闭凸集.在q-一致光滑且一致凸的Banach空间中,对于严格伪压缩映射T,利用徐洪坤在2004年引进的粘滞迭代得到的序列弱收敛于T的某个不动点.同时证明了Hilbert空间中Browder-Petryshyn型的严格伪压缩映射的相应迭代序列强收敛到T的某个不动点,其结果推广与改进了徐洪坤2004年的相应结果. 相似文献
44.
Alex Hellsten 《Archive for Mathematical Logic》2006,45(6):705-714
We extract some properties of Mahlo’s operation and show that some other very natural operations share these properties. The weakly compact sets form a similar hierarchy as the stationary sets. The height of this hierarchy is a large cardinal property connected to saturation properties of the weakly compact ideal. 相似文献
45.
Dmitry I. Belov Ronald D. Armstrong 《Computational Optimization and Applications》2006,33(2-3):319-332
This paper introduces a novel approach for extracting the maximum number of non-overlapping test forms from a large collection
of overlapping test sections assembled from a given item bank. The approach involves solving maximum set packing problems
(MSPs). A branch-and-bound MSP algorithm is developed along with techniques adapted from constraint programming to estimate
lower and upper bounds on the optimal MSP solution. The algorithm is general and can be applied in other applications including
combinatorial auctions. The results of computer simulations and experiments with an operational item bank are presented.
An erratum to this article is available at . 相似文献
46.
Brian Lucena 《Discrete Applied Mathematics》2007,155(8):1055-1065
One consequence of the graph minor theorem is that for every k there exists a finite obstruction set Obs(TW?k). However, relatively little is known about these sets, and very few general obstructions are known. The ones that are known are the cliques, and graphs which are formed by removing a few edges from a clique. This paper gives several general constructions of minimal forbidden minors which are sparse in the sense that the ratio of the treewidth to the number of vertices n does not approach 1 as n approaches infinity. We accomplish this by a novel combination of using brambles to provide lower bounds and achievable sets to demonstrate upper bounds. Additionally, we determine the exact treewidth of other basic graph constructions which are not minimal forbidden minors. 相似文献
47.
Many recent algorithmic approaches involve the construction of a differential equation model for computational purposes, typically
by introducing an artificial time variable. The actual computational model involves a discretization of the now time-dependent differential system, usually
employing forward Euler. The resulting dynamics of such an algorithm is then a discrete dynamics, and it is expected to be
“close enough” to the dynamics of the continuous system (which is typically easier to analyze) provided that small – hence
many – time steps, or iterations, are taken. Indeed, recent papers in inverse problems and image processing routinely report
results requiring thousands of iterations to converge. This makes one wonder if and how the computational modeling process
can be improved to better reflect the actual properties sought.
In this article we elaborate on several problem instances that illustrate the above observations. Algorithms may often lend
themselves to a dual interpretation, in terms of a simply discretized differential equation with artificial time and in terms
of a simple optimization algorithm; such a dual interpretation can be advantageous. We show how a broader computational modeling
approach may possibly lead to algorithms with improved efficiency.
AMS subject classification (2000) 65L05, 65M32, 65N21, 65N22, 65D18 相似文献
48.
基础房价的相关指标及其走势一直是大众关心的热门话题.本文通过对上海基础房价相关指标的分析,建立了市场房价走势的两个数学模型.模型一:在相关性分析的基础上利用主成分分析消除指标间的共线性,再用回归拟合房价模型并进行预测;模型二:在相关性分析的基础上利用核估计方法预测出房价.继呵对2005年下半年的房价走势进行了预测,得出的结果与实际情况相吻合. 相似文献
49.
In this paper, nonconvex multiobjective optimization problems are studied. New characterizations of a properly efficient solution in the sense of Geoffrion's are established in terms of the stability of one scalar optimization problem and the existence of an exact penalty function of a scalar constrained program, respectively. One of the characterizations is applied to derive necessary conditions for a properly efficient control-parameter pair of a nonconvex multiobjective discrete optimal control problem with linear constraints. 相似文献
50.
对覆盖广义Rough集中的隶属关系、隶属函数进行了定义,并利用隶属函数定义了集合的Rough包含与Rough相等,得到一些与Pawlak的Rough集不同的性质。 相似文献