全文获取类型
收费全文 | 1197篇 |
免费 | 109篇 |
国内免费 | 143篇 |
专业分类
化学 | 200篇 |
晶体学 | 3篇 |
力学 | 43篇 |
综合类 | 25篇 |
数学 | 446篇 |
物理学 | 196篇 |
无线电 | 536篇 |
出版年
2024年 | 1篇 |
2023年 | 11篇 |
2022年 | 13篇 |
2021年 | 6篇 |
2020年 | 18篇 |
2019年 | 31篇 |
2018年 | 24篇 |
2017年 | 24篇 |
2016年 | 28篇 |
2015年 | 27篇 |
2014年 | 49篇 |
2013年 | 86篇 |
2012年 | 53篇 |
2011年 | 53篇 |
2010年 | 65篇 |
2009年 | 55篇 |
2008年 | 100篇 |
2007年 | 100篇 |
2006年 | 84篇 |
2005年 | 95篇 |
2004年 | 77篇 |
2003年 | 75篇 |
2002年 | 71篇 |
2001年 | 49篇 |
2000年 | 40篇 |
1999年 | 43篇 |
1998年 | 42篇 |
1997年 | 27篇 |
1996年 | 11篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有1449条查询结果,搜索用时 15 毫秒
101.
M. K. Bos. 《Mathematics of Computation》2003,72(244):2001-2012
In this paper, an algorithm for computing the principal character for affine Lie algebras is discussed and presented. The principal characters discovered using this program are given and/or proven. Results include level 2 and 3 character formulas in and the sole existence of the Rogers-Ramanujan products in , , , , , , . 相似文献
102.
We obtain upper bounds for mixed exponential sums of the type
where pm is a prime power with m⩾ 2 and X is a multiplicative character (mod pm). If X is primitive or p⫮(a, b) then we obtain |S(χ,f,p
m)| ⩽2np
2/3 m. If X is of conductor p and p⫮( a, b) then we get the stronger bound |S(χ,f,p
m)|⩽np
m/2.
This paper is dedicated to Prof. Wang Yuan on the occasion of his 70th birthday. 相似文献
103.
Generalized Steiner systems GS(2, 4, v, g) were first introduced by Etzion and were used to construct optimal constant weight codes over an alphabet of size g + 1 with minimum Hamming distance 5, in which each codeword has length v and weight 4. Etzion conjectured that the necessary conditions v 1 (mod 3) and v ; 7 are also sufficient for the existence of a GS(2,4,v,2). Except for the example of a GS(2,4,10,2) and some recursive constructions given by Etzion, nothing else is known about this conjecture. In this paper, Weil's theorem on character sum estimates is used to show that the conjecture is true for any prime power v 7 (mod 12) except v = 7, for which there does not exist a GS(2,4,7,2). 相似文献
104.
In [2] E. Dobrowolski and K.S. Williams considered a problem of obtaining estimates for the sum
n=a+1
a+N
f(n),for a certain class of functions f. One specific application of their result is a new method for estimating character sums. In particular, they obtain a form of the Pólya-Vinogradov inequality with the constant 1/(2 log 2). In this note we improve their estimates and obtain, in particular, a form of the Pólya-Vinogradov inequality with the constant 1/(3 log 3). A nice feature of our estimate is that it is obtained by a very simple argument. 相似文献
105.
Mark L. Lewis 《Algebras and Representation Theory》2001,4(5):469-489
Let G be a solvable group with five character degrees. We show that the derived length of G is at most 5. This verifies that the Taketa inequality, dl(G)|cd(G)|, is valid for solvable groups with at most five character degrees. 相似文献
106.
NOTES ON GLAISHER'S CONGRUENCES 总被引:1,自引:0,他引:1
HONG Shaofang 《数学年刊B辑(英文版)》2000,21(1):33-38
Let p be an odd prime and let n≥1,k≥0 and r be integers,denote by Bk the kth Bernoulli number,It is proved that(i) If r≥1 is odd and suppose 1≥r+4,then ∑j=1^p-1 1/(np+j)^r=-(2n+1)r(r+1)/2(r+2)Bp-r-2p^2(mod p^3).(ii)If r≥2 is even and suppose p≥r+3, then p-1∑j=1 1/(np+j)^r=r/r+1Bv-r-1p(mod P^2).(iii) p-1∑j=1 1/(np+j)p-2=-(2n+1)p(mod P^2).This result generalizes the Glaisher‘s congruence. As a corollary, a generalization of the Wolsten-holme‘s theorem is obtained. 相似文献
107.
This paper discusses the role played by perturbed Dolbeault operators in relating the coherent sheaf and elliptic operator perspectives on the homology of projective varieties. Among the consequences are index formulas for perturbed Dolbeault operators.
108.
We investigate certain finite subgroups of , where is a finite nilpotent group. Such a group gives rise to a -module; we study the characters of these modules to limit the structure of . We also exhibit some exotic subgroups .
109.
110.
Jyh-Horng Wen Gwo-Ruey Lee Wen-Hui Kuan Cheng-Ying Yang 《Wireless Personal Communications》2007,43(4):1323-1331
Previously, the timing estimation in OFDM system employs cyclic prefix has been presented with the assumption of independent
identified distributed OFDM symbol. The information used to find the symbol synchronization depends on the length of cyclic
prefix. Actually, the data in the BPSK-OFDM modulated symbol, transferred by inverse fast Fourier transform, is with a complex
symmetry character. With this character, more information from the whole OFDM symbol could be provided for the symbol timing.
In this paper, the proposed algorithm uses the autocorrelation of the received signal to obtain the symbol timing. The simulation
of Beek’s algorithm and the proposed scheme are presented. The performances of these algorithms are evaluated based on the
missing symbol probability and the estimator mean square error. The simulation results show that the proposed algorithm is
suitable to achieve a better symbol synchronization. 相似文献