全文获取类型
收费全文 | 5126篇 |
免费 | 320篇 |
国内免费 | 666篇 |
专业分类
化学 | 168篇 |
晶体学 | 1篇 |
力学 | 159篇 |
综合类 | 76篇 |
数学 | 5152篇 |
物理学 | 556篇 |
出版年
2024年 | 4篇 |
2023年 | 62篇 |
2022年 | 49篇 |
2021年 | 62篇 |
2020年 | 104篇 |
2019年 | 139篇 |
2018年 | 154篇 |
2017年 | 149篇 |
2016年 | 151篇 |
2015年 | 130篇 |
2014年 | 230篇 |
2013年 | 514篇 |
2012年 | 161篇 |
2011年 | 253篇 |
2010年 | 208篇 |
2009年 | 340篇 |
2008年 | 423篇 |
2007年 | 346篇 |
2006年 | 310篇 |
2005年 | 295篇 |
2004年 | 235篇 |
2003年 | 263篇 |
2002年 | 252篇 |
2001年 | 174篇 |
2000年 | 165篇 |
1999年 | 165篇 |
1998年 | 161篇 |
1997年 | 154篇 |
1996年 | 79篇 |
1995年 | 59篇 |
1994年 | 51篇 |
1993年 | 31篇 |
1992年 | 15篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1970年 | 2篇 |
排序方式: 共有6112条查询结果,搜索用时 0 毫秒
31.
In [3] it was shown that a (real) signed measure on a cyclic coarse-grained quantum logic can be extended, as a signed measure,
over the entire power algebra. Later ([9]) this result was re-proved (and further improved on) and, moreover, the non-negative
measures were shown to allow for extensions as non-negative measures. In both cases the proof technique used was the technique
of linear algebra. In this paper we further generalize the results cited by extending group-valued measures on cyclic coarse-grained
quantum logics (or non-negative group-valued measures for lattice-ordered groups). Obviously, the proof technique is entirely
different from that of the preceding papers. In addition, we provide a new combinatorial argument for describing all atoms
of cyclic coarse-grained quantum logics. 相似文献
32.
Il Bong Jung Alan Lambert Jan Stochel 《Proceedings of the American Mathematical Society》2004,132(8):2291-2302
The concept of backward extension for subnormal weighted shifts is generalized to arbitrary subnormal operators. Several differences and similarities in these contexts are explored, with emphasis on the structure of the underlying measures.
33.
A. E. Mironov 《Functional Analysis and Its Applications》2005,39(3):240-243
We construct commuting rank 2 formally self-adjoint ordinary differential operators corresponding to a curve of genus 2. 相似文献
34.
M. I. Gil' 《Proceedings of the American Mathematical Society》2003,131(12):3737-3746
A linear operator in a separable Hilbert space is called a quasinormal one if it is a sum of a normal operator and a compact one. In the paper, bounds for the spectrum of quasinormal operators are established. In addition, the lower estimate for the spectral radius is derived. Under some restrictions, that estimate improves the well-known results. Applications to integral operators and matrices are discussed. Our results are new even in the finite-dimensional case.
35.
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
36.
In this paper we give necessary and sufficient conditions for the existence of a C>
0-semigroup in L
1(I) (I real interval) generated by a second-order differential operator when suitable boundary conditions at the endpoints are imposed. 相似文献
37.
用A的不变子空间作参数,给出了算子方程AX=XAX的全部解。当A是单射或稠值域时,或者当A是正规算子时,给出了算子方程AX=XA=XAX的全部解。我们还给出正规算子X是算子方程AX=XZ=XAX的解的充分必要条件。 相似文献
38.
39.
M.K. Gupta Vijay Gupta Manoj Kumar 《Journal of Mathematical Analysis and Applications》2007,330(2):799-816
In the present paper we introduce a new family of linear positive operators and study some direct and inverse results in simultaneous approximation. 相似文献
40.
Mohamed El-Gebeily Donal O'Regan 《Journal of Mathematical Analysis and Applications》2007,334(1):140-156
Existence theory is developed for the equation ?(u)=F(u), where ? is a formally self-adjoint singular second-order differential expression and F is nonlinear. The problem is treated in a Hilbert space and we do not require the operators induced by ? to have completely continuous resolvents. Nonlinear boundary conditions are allowed. Also, F is assumed to be weakly continuous and monotone at one point. Boundary behavior of functions associated with the domains of definitions of the operators associated with ? in the singular case is investigated. A special class of self-adjoint operators associated with ? is obtained. 相似文献