全文获取类型
收费全文 | 6079篇 |
免费 | 775篇 |
国内免费 | 650篇 |
专业分类
化学 | 744篇 |
晶体学 | 18篇 |
力学 | 549篇 |
综合类 | 176篇 |
数学 | 4852篇 |
物理学 | 1165篇 |
出版年
2024年 | 12篇 |
2023年 | 33篇 |
2022年 | 77篇 |
2021年 | 108篇 |
2020年 | 151篇 |
2019年 | 144篇 |
2018年 | 153篇 |
2017年 | 186篇 |
2016年 | 194篇 |
2015年 | 131篇 |
2014年 | 244篇 |
2013年 | 542篇 |
2012年 | 267篇 |
2011年 | 334篇 |
2010年 | 330篇 |
2009年 | 402篇 |
2008年 | 452篇 |
2007年 | 437篇 |
2006年 | 384篇 |
2005年 | 374篇 |
2004年 | 323篇 |
2003年 | 355篇 |
2002年 | 291篇 |
2001年 | 238篇 |
2000年 | 194篇 |
1999年 | 214篇 |
1998年 | 179篇 |
1997年 | 153篇 |
1996年 | 104篇 |
1995年 | 74篇 |
1994年 | 78篇 |
1993年 | 46篇 |
1992年 | 36篇 |
1991年 | 24篇 |
1990年 | 29篇 |
1989年 | 20篇 |
1988年 | 26篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1936年 | 3篇 |
排序方式: 共有7504条查询结果,搜索用时 300 毫秒
41.
A. V. Kel’manov L. V. Mikhailova 《Computational Mathematics and Mathematical Physics》2006,46(1):165-181
The problem of joint a posteriori detection of reference fragments in a quasi-periodic sequence and its partition into segments containing series of recurring fragments from the reference tuple is solved. It is assumed that (i) an ordered reference tuple of sequences to be detected is given, (ii) the number of desired fragments is known, (iii) the index of the sequence term corresponding to the beginning of a fragment is a deterministic (not random) value, and (iv) a sequence distorted by an additive uncorrelated Gaussian noise is available for observation. It is established that the problem consists in testing a set of hypotheses about the mean of a random Gaussian vector. The cardinality of the set grows exponentially as the vector dimension (i.e., the sequence length) increases. An efficient a posteriori algorithm producing a maximum-likelihood optimal solution to the problem is substantiated. Time and space complexity bounds related to the parameters of the problem are derived. The results of numerical simulation are presented. 相似文献
42.
This article studies the inshore-offshore fishery model with impulsive diffusion. The existence and global asymptotic stability of both the trivial periodic solution and the positive periodic solution are obtained. The complexity of this system is also analyzed. Moreover, the optimal harvesting policy are given for the inshore subpopulation, which includes the maximum sustainable yield and the corresponding harvesting effort. 相似文献
43.
Piotr Szopa 《Mathematical Methods in the Applied Sciences》2007,30(3):331-346
In this paper, we prove the existence and uniqueness of a global solution for 2‐D micropolar fluid equation with periodic boundary conditions. Then we restrict ourselves to the autonomous case and show the existence of a global attractor. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
44.
Eckhard Steffen 《Discrete Mathematics》2004,280(1-3):191-214
Cubic bridgeless graphs with chromatic index four are called uncolorable. We introduce parameters measuring the uncolorability of those graphs and relate them to each other. For k=2,3, let ck be the maximum size of a k-colorable subgraph of a cubic graph G=(V,E). We consider r3=|E|−c3 and
. We show that on one side r3 and r2 bound each other, but on the other side that the difference between them can be arbitrarily large. We also compare them to the oddness ω of G, the smallest possible number of odd circuits in a 2-factor of G. We construct cyclically 5-edge connected cubic graphs where r3 and ω are arbitrarily far apart, and show that for each 1c<2 there is a cubic graph such that ωcr3. For k=2,3, let ζk denote the largest fraction of edges that can be k-colored. We give best possible bounds for these parameters, and relate them to each other. 相似文献
45.
Banach空间二阶周期边值问题解的存在性 总被引:2,自引:0,他引:2
利用一些比较结果,讨论了Banach空间中二阶周期边值问题解的存在性,获得了若干解的存在性与唯一性结果。 相似文献
46.
The theory of monotone semiflows has been widely applied to functional differential equations (FDEs). The studies on the theory and applications of monotone semiflows for FDEs are very important and interesting. A brief des-cription of our recent works are as follows.By using general monotone semiflow theory, several results of positively invariant sets, monotone solutions and contracting rectangles of retarded functional differential equations(RFDEs) with infinite delay are gained under the assumption of quasimonotonicity; sufficient conditions for the existence, un-iqueness and global attractivity of periodic solutions are also established by combining the theory of monotone semiflows for neutral functional differential equations(NFDEs) and Krasnoselskii's fixed point theorem. 相似文献
47.
48.
Nguyen Minh Chuong Bui Kien Cuong 《Proceedings of the American Mathematical Society》2004,132(12):3589-3597
A class of Cauchy problems for interesting complicated periodic pseudodifferential equations is considered. By the Galerkin-wavelet method and with weak solutions one can find sufficient conditions to establish convergence estimates of weak Galerkin-wavelet solutions to a Cauchy problem for this class of equations.
50.
Donald W. Barnes 《Transactions of the American Mathematical Society》2003,355(7):2755-2769
The concept of a spectral sequence constructor is generalised to Hopf Galois extensions. The spectral sequence constructions that are given by Guichardet for crossed product algebras are also generalised and shown to provide examples. It is shown that all spectral sequence constructors for Hopf Galois extensions construct the same spectral sequence. 相似文献