全文获取类型
收费全文 | 5719篇 |
免费 | 916篇 |
国内免费 | 536篇 |
专业分类
化学 | 698篇 |
晶体学 | 101篇 |
力学 | 531篇 |
综合类 | 88篇 |
数学 | 2886篇 |
物理学 | 2867篇 |
出版年
2024年 | 7篇 |
2023年 | 55篇 |
2022年 | 116篇 |
2021年 | 110篇 |
2020年 | 148篇 |
2019年 | 147篇 |
2018年 | 137篇 |
2017年 | 140篇 |
2016年 | 163篇 |
2015年 | 145篇 |
2014年 | 273篇 |
2013年 | 432篇 |
2012年 | 275篇 |
2011年 | 281篇 |
2010年 | 273篇 |
2009年 | 344篇 |
2008年 | 353篇 |
2007年 | 387篇 |
2006年 | 351篇 |
2005年 | 340篇 |
2004年 | 282篇 |
2003年 | 265篇 |
2002年 | 317篇 |
2001年 | 238篇 |
2000年 | 230篇 |
1999年 | 223篇 |
1998年 | 191篇 |
1997年 | 160篇 |
1996年 | 107篇 |
1995年 | 84篇 |
1994年 | 86篇 |
1993年 | 50篇 |
1992年 | 52篇 |
1991年 | 44篇 |
1990年 | 35篇 |
1989年 | 32篇 |
1988年 | 39篇 |
1987年 | 35篇 |
1986年 | 33篇 |
1985年 | 38篇 |
1984年 | 21篇 |
1983年 | 10篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1979年 | 14篇 |
1978年 | 16篇 |
1977年 | 13篇 |
1976年 | 17篇 |
1972年 | 4篇 |
排序方式: 共有7171条查询结果,搜索用时 15 毫秒
61.
62.
李邦河 《应用泛函分析学报》2006,8(4):295-303
证明了傅立叶超函数和扩充傅立叶超函数可用爱米特热方程的解来表示,且用以表示的解有很良好的性质. 相似文献
63.
本文研究了两类重要微分不等式有界解的性质。引入了赋范线性空间(f,‖‖M),利用比较定理和黎卡提方程解的性质,给出了有界解的上界估计式,推广和改进了文[1,2]中的有关结果. 相似文献
64.
The decision problem for positively quantified formulae in the theory of linearly ordered Heyting algebras is known, as a special case of work of Kreisel, to be solvable; a simple solution is here presented, inspired by related ideas in Gödel-Dummett logic. 相似文献
65.
得到εdx/dt=A(t)x的扰动系统具有指数型二分性一个充分条件,作为应用得到其扰动系统概周期解及有界解的存在性,推广了[1,2,3]的结果。 相似文献
66.
Ronald H. Nickel Igor Mikolic-Torreira Jon W. Tolle 《Computational Optimization and Applications》2006,35(1):109-126
Deployed US Navy aircraft carriers must stock a large number of spare parts to support the various types of aircraft embarked
on the ship. The sparing policy determines the spares that will be stocked on the ship to keep the embarked aircraft ready
to fly. Given a fleet of ten or more aircraft carriers and a cost of approximately 50 million dollars per carrier plus the
cost of spares maintained in warehouses in the United States, the sparing problem constitutes a significant portion of the
Navy’s resources. The objective of this work is to find a minimum-cost sparing policy that meets the readiness requirements
of the embarked aircraft. This is a very large, nonlinear, integer optimization problem. The cost function is piecewise linear
and convex while the constraint mapping is highly nonlinear. The distinguishing characteristics of this problem from an optimization
viewpoint are that a large number of decision variables are required to be integer and that the nonlinear constraint functions
are essentially “black box” functions; that is, they are very difficult (and expensive) to evaluate and their derivatives
are not available. Moreover, they are not convex. Integer programming problems with a large number of variables are difficult
to solve in general and most successful approaches to solving nonlinear integer problems have involved linear approximation
and relaxation techniques that, because of the complexity of the constraint functions, are inappropriate for attacking this
problem. We instead employ a pattern search method to each iteration of an interior point-type algorithm to solve the relaxed
version of the problem. From the solution found by the pattern search on each interior point iteration, we begin another pattern
search on the integer lattice to find a good integer solution. The best integer solution found across all interations is returned
as the optimal solution. The pattern searches are distributed across a local area network of non-dedicated, heterogeneous
computers in an office environment, thus, drastically reducing the time required to find the solution. 相似文献
67.
C. Zălinescu 《Mathematical Methods of Operations Research》1991,35(4):291-298
In this paper there is stated a result on sets in ordered linear spaces which can be used to show that some properties of the sets are inherited by their convex hulls under suitable conditions. As applications one gives a characterization of weakly efficient points and a duality result for nonconvex vector optimization problems. 相似文献
68.
Oscar Valero 《Proceedings Mathematical Sciences》2006,116(2):175-191
Given a normed cone (X, p) and a subconeY, we construct and study the quotient normed cone (X/Y,p) generated byY. In particular we characterize the bicompleteness of (X/Y, ‖·‖
p
,p) in terms of the bicompleteness of (X, p), and prove that the dual quotient cone ((X/Y)*, || · ‖·‖p,p) can be identified as a distinguished subcone of the dual cone (X
*, || · ||p, u). Furthermore, some parts of the theory are presented in the general setting of the spaceCL(X, Y) of all continuous linear mappings from a normed cone (X, p) to a normed cone (Y, q), extending several well-known results related to open continuous linear mappings between normed linear spaces. 相似文献
69.
Cardy's formula for some dependent percolation models 总被引:2,自引:0,他引:2
F. Camia C. M. Newman V. Sidoravicius 《Bulletin of the Brazilian Mathematical Society》2002,33(2):147-156
We prove Cardy's formula for rectangular crossing probabilities in dependent site percolation models that arise from a deterministic cellular automaton with a random initial state. The cellular automaton
corresponds to the zero-temperature case of Domany's stochastic Ising ferromagnet on the hexagonal lattice (with alternating
updates of two sublattices) [7]; it may also be realized on the triangular lattice 𝕋 with flips when a site disagrees with
six, five and sometimes four of its six neighbors.
Received: 24 December 2001 相似文献
70.
采用第一性原理计算模拟了不同组分的MgxZn1-xO半导体混晶的晶格常数、总能、结构,以及禁带宽度的变化。计算结果显示,随着Mg组分的增加,晶格常数逐渐减小,晶体逐渐偏离纤锌矿结构。对各种不同的Mg原子排列情况进行比较认为,MgxZn1-xO的结构随组分x的增大,发生从纤锌矿到岩盐矿的结构相变的可能性高于发生相分离。另一方面,禁带宽度随组分增大主要由价带顶的移动所致。进一步分析Mg原子各种电子态对价带的影响表明,Mg对价带顶附近能带的贡献依次来自p、d、s态电子。随着组分x的增加,p态电子在价带顶附近的密度明显提高,说明sp轨道杂化不但对晶体的几何结构产生影响,而且对其电子结构也起重要作用。 相似文献