全文获取类型
收费全文 | 29947篇 |
免费 | 4821篇 |
国内免费 | 3485篇 |
学科分类
数理化 | 38253篇 |
出版年
2024年 | 82篇 |
2023年 | 673篇 |
2022年 | 763篇 |
2021年 | 1016篇 |
2020年 | 1206篇 |
2019年 | 1180篇 |
2018年 | 994篇 |
2017年 | 946篇 |
2016年 | 1409篇 |
2015年 | 1382篇 |
2014年 | 1603篇 |
2013年 | 2113篇 |
2012年 | 2621篇 |
2011年 | 2776篇 |
2010年 | 1882篇 |
2009年 | 1676篇 |
2008年 | 1977篇 |
2007年 | 1849篇 |
2006年 | 1654篇 |
2005年 | 1401篇 |
2004年 | 1082篇 |
2003年 | 897篇 |
2002年 | 869篇 |
2001年 | 637篇 |
2000年 | 610篇 |
1999年 | 714篇 |
1998年 | 532篇 |
1997年 | 494篇 |
1996年 | 447篇 |
1995年 | 425篇 |
1994年 | 401篇 |
1993年 | 350篇 |
1992年 | 278篇 |
1991年 | 282篇 |
1990年 | 252篇 |
1989年 | 166篇 |
1988年 | 128篇 |
1987年 | 125篇 |
1986年 | 79篇 |
1985年 | 75篇 |
1984年 | 63篇 |
1983年 | 38篇 |
1982年 | 36篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Let T be a bounded linear operator on Hilbert space H, M an invariant subspace of T. If there exists another invariant subspace N of T such that H = M + N and M ∩ N = 0, then M is said to be a completely reduced subspace of T. If T has a nontrivial completely reduced subspace, then T is said to be completely reducible; otherwise T is said to be completely irreducible. In the present paper we briefly sum up works on completely irreducible operators that
have been done by the Functional Analysis Seminar of Jilin University in the past ten years and more.
The paper contains four sections. In section 1 the background of completely irreducible operators is given in detail. Section
2 shows which operator in some well-known classes of operators, for example, weighted shifts, Toeplitz operators, etc., is
completely irreducible. In section 3 it is proved that every bounded linear operator on the Hilbert space can be approximated
by the finite direct sum of completely irreducible operators. It is clear that a completely irreducible operator is a rather
suitable analogue of Jordan blocks in L(H), the set of all bounded linear operators on Hilbert space H. In section 4 several questions concerning completely irreducible operators are discussed and it is shown that some properties
of completely irreducible operators are different from properties of unicellular operators.
__________
Translated from Acta Sci. Nat. Univ. Jilin, 1992, (4): 20–29 相似文献
53.
Propagation of the Hermite–Gaussian beams through misaligned optical system with a circular aperture
By means of expanding a hard-edged aperture into a finite sum of complex Gaussian functions, the approximate analytical formula of one kind of higher-order Gaussian beams called the Hermite–Gaussian beams (HGBs) passing through circular apertured and misaligned optical system is obtained in this paper. The result provides more convenience for studying its propagation than the usual way by using diffraction integral directly. Some numerical simulations are also given for illustrating the propagation properties of the HGBs through the circular apertured optical systems. 相似文献
54.
55.
56.
利用变分法证明平面调和函数的外问题的确切形式;在此基础上,建立外问题的具有间接变量的等价边界积分方程;传统的外问题及边界积分方程不具有普遍适用性,本文对此进行了详细的讨论. 相似文献
57.
Equilibrium Problems with Applications to Eigenvalue Problems 总被引:5,自引:0,他引:5
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given. 相似文献
58.
根据Co P非晶态合金结构的短程有序和结构中可能存在P -P相互作用的实验事实 ,选择了单磷原子簇模型ConP(n =1~ 5 )和双磷原子簇模型ConP2 (n =1~ 4 ) ,用密度泛函理论方法对其进行计算 .结果表明 ,在单磷Co2 P( 2 ) 、Co3 P( 1) 及Co4P( 2 ) 模型体系中 ,Co原子供给P原子电子 ,与电负性规则一致 ,同时Co和P之间具较强化学作用 ,可以形成稳定的原子簇 ;而在双磷和单磷原子簇Co5P( 1) 模型体系中 ,形成的原子簇不稳定 ,采用单磷Co2 P( 2 ) 、Co3 P( 1) 及Co4P( 2 ) 模型能较好地反映Co P非晶态合金的结构特点 . 相似文献
59.
We consider a useful modification of the inexact implicit method with a variable parameter in Wang et al. J Optim Theory 111:
431–443 (2001) for generalized mixed monotone variational inequalities. One of the contributions of the proposed method in
this paper is that the restrictions imposed on the variable parameter are weaker than the ones in Wang et al. J Optim Theory
111: 431–443 (2001). Another contribution is that we establish a sufficient and necessary condition for the convergence of
the proposed method to a solution of the general mixed monotone variational inequality. 相似文献
60.