全文获取类型
收费全文 | 11990篇 |
免费 | 1185篇 |
国内免费 | 939篇 |
专业分类
化学 | 2203篇 |
晶体学 | 28篇 |
力学 | 878篇 |
综合类 | 295篇 |
数学 | 7769篇 |
物理学 | 2941篇 |
出版年
2024年 | 27篇 |
2023年 | 124篇 |
2022年 | 189篇 |
2021年 | 251篇 |
2020年 | 316篇 |
2019年 | 332篇 |
2018年 | 323篇 |
2017年 | 349篇 |
2016年 | 453篇 |
2015年 | 301篇 |
2014年 | 557篇 |
2013年 | 1029篇 |
2012年 | 489篇 |
2011年 | 686篇 |
2010年 | 639篇 |
2009年 | 709篇 |
2008年 | 742篇 |
2007年 | 781篇 |
2006年 | 690篇 |
2005年 | 651篇 |
2004年 | 557篇 |
2003年 | 545篇 |
2002年 | 516篇 |
2001年 | 398篇 |
2000年 | 380篇 |
1999年 | 330篇 |
1998年 | 309篇 |
1997年 | 241篇 |
1996年 | 202篇 |
1995年 | 160篇 |
1994年 | 119篇 |
1993年 | 109篇 |
1992年 | 93篇 |
1991年 | 84篇 |
1990年 | 47篇 |
1989年 | 55篇 |
1988年 | 40篇 |
1987年 | 26篇 |
1986年 | 35篇 |
1985年 | 39篇 |
1984年 | 31篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 22篇 |
1980年 | 16篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1977年 | 16篇 |
1976年 | 9篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
A note on the spectrum of an upper triangular operator matrix 总被引:1,自引:0,他引:1
Mohamed Barraa Mohamed Boumazgour 《Proceedings of the American Mathematical Society》2003,131(10):3083-3088
Let be a upper triangular operator matrix acting on the Banach space . We investigate the set of the operators for which , where denotes the spectrum.
82.
Let S
d denote the symmetric group on d letters. In 1979 Mullineux conjectured a combinatorial algorithm for calculating the effect of tensoring with an irreducible S
d-module with the one dimensional sign module when the ground field has positive characteristic. Kleshchev proved the Mullineux conjecture in 1996. In the present article we provide a new proof of the Mullineux conjecture which is entirely independent of Kleshchev's approach. Applying the representation theory of the supergroup GL(m | n) and the supergroup analogue of Schur-Weyl Duality it becomes straightforward to calculate the combinatorial effect of tensoring with the sign representation and, hence, to verify Mullineux's conjecture. Similar techniques also allow us to classify the irreducible polynomial representations of GL(m | n) of degree d for arbitrary m, n, and d. 相似文献
83.
We determine the distribution of quadruple systems among the orbits of 4‐element subsets under the action of PSL(2,q) on the projective line when q ≡ 1 (mod 4). © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 339–351, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10043 相似文献
84.
For symmetric spaces of noncompact type we prove an analogue of Hardy’s theorem which characterizes the heat kernel in terms
of its order of magnitude and that of its Fourier transform. 相似文献
85.
We study the symmetric positive semidefinite solution of the matrix equation AX
1
A
T
+ BX
2
B
T
= C, where A is a given real m×n matrix, B is a given real m×p matrix, and C is a given real m×m matric, with m, n, p positive integers; and the bisymmetric positive semidefinite solution of the matrix equation D
T
XD = C, where D is a given real n×m matrix, C is a given real m×m matrix, with m, n positive integers. By making use of the generalized singular value decomposition, we derive general analytic formulae, and
present necessary and sufficient conditions for guaranteeing the existence of these solutions.
Received December 17, 1999, Revised January 10, 2001, Accepted March 5, 2001 相似文献
86.
Yu Chen 《Advances in Computational Mathematics》2002,16(2-3):175-190
The state-of-the-art, large-scale numerical simulations of the scattering problem for the Helmholtz equation in two dimensions rely on iterative solvers for the Lippmann–Schwinger integral equation, with an optimal CPU time O(m
3 log(m)) for an m-by-m wavelength problem. We present a method to solve the same problem directly, as opposed to iteratively, with the obvious advantage in efficiency for multiple right-hand sides corresponding to distinct incident waves. Analytically, this direct method is a hierarchical, recursive scheme consisting of the so-called splitting and merging processes. Algebraically, it amounts to a recursive matrix decomposition, for a cost of O(m
3), of the discretized Lippmann–Schwinger operator. With this matrix decomposition, each back substitution requires only O(m
2 log(m)); therefore, a scattering problem with m incident waves can be solved, altogether, in O(m
3 log(m)) flops. 相似文献
87.
本文对 Jordan标准形定理给出了一种使用初等变换的证明 ,直观意义明显、易于理解 ,可用于线性代数教学 . 相似文献
88.
Masafumi Akahira 《Annals of the Institute of Statistical Mathematics》1996,48(2):365-380
Under suitable regularity conditions, it is shown that a third order asymptotically efficient estimator is fourth order asymptotically efficient in some class of estimators in the sense that the estimator has the most concentration probability in any symmetric interval around the true parameter up to the fourth order in the class. This is a resolution of the conjecture by Ghosh (1994, Higher Order Asymptotics, Institute of Mathematical Statistics, Hayward, California). It is also shown that the bias-adjusted maximum likelihood estimator is fourth order asymptotically efficient in the class. 相似文献
89.
Teruhiro Shirakura 《Annals of the Institute of Statistical Mathematics》1986,38(1):145-159
Summary For a given fractional 2
m
factorial (2
m
-FF) designT, the constitution of a block plan to divideT intok (2
r−1<k≦2
r
) blocks withr block factors each at two levels is proposed and investigated. The well-known three norms of the confounding matrix are used
as measures for determining a “good” block plan. Some theorems concerning the constitution of a block plan are derived for
a 2
m
-FF design of odd or even resolution. Two norms which may be preferred over the other norm are slightly modified. For each
value ofN assemblies with 11≦N≦26, optimum block plans fork=2 blocks with block sizes [N/2] andN−[N/2] minimizing the two norms are presented forA-optimal balanced 24-FF designs of resolutionV given by Srivastava and Chopra (Technometrics,13, 257–269). 相似文献
90.
Yingxin Jiang 《Fiber and Integrated Optics》2013,32(3):192-200
Abstract Through the modified transfer matrix method, the transmission properties of a one-dimensional coupled-resonator optical waveguide structure composed of metal layers and non-linear material layers is studied. Given proper incident frequency and structure parameters, an optical tri-stability has been achieved. The effect of loss has been considered. 相似文献