全文获取类型
收费全文 | 6258篇 |
免费 | 572篇 |
国内免费 | 597篇 |
专业分类
化学 | 3832篇 |
晶体学 | 36篇 |
力学 | 207篇 |
综合类 | 72篇 |
数学 | 2163篇 |
物理学 | 1117篇 |
出版年
2024年 | 7篇 |
2023年 | 43篇 |
2022年 | 64篇 |
2021年 | 94篇 |
2020年 | 156篇 |
2019年 | 160篇 |
2018年 | 164篇 |
2017年 | 215篇 |
2016年 | 181篇 |
2015年 | 199篇 |
2014年 | 279篇 |
2013年 | 952篇 |
2012年 | 266篇 |
2011年 | 297篇 |
2010年 | 254篇 |
2009年 | 315篇 |
2008年 | 337篇 |
2007年 | 352篇 |
2006年 | 343篇 |
2005年 | 287篇 |
2004年 | 272篇 |
2003年 | 250篇 |
2002年 | 850篇 |
2001年 | 175篇 |
2000年 | 181篇 |
1999年 | 115篇 |
1998年 | 140篇 |
1997年 | 76篇 |
1996年 | 86篇 |
1995年 | 74篇 |
1994年 | 58篇 |
1993年 | 36篇 |
1992年 | 28篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1968年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有7427条查询结果,搜索用时 15 毫秒
51.
Nathan Bloomfield 《代数通讯》2013,41(2):765-775
To each commutative ring R we can associate a zero divisor graph whose vertices are the zero divisors of R and such that two vertices are adjacent if their product is zero. Detecting isomorphisms among zero divisor graphs can be reduced to the problem of computing the classes of R under a suitable semigroup congruence. Presently, we introduce a strategy for computing this quotient for local rings using knowledge about a generating set for the maximal ideal. As an example, we then compute Γ(R) for several classes of rings; with the results in [4] these classes include all local rings of order p 4 and p 5 for prime p. 相似文献
52.
Let K be an infinite field of characteristic different from 2, and G a group. Under suitable restrictions upon G, we classify the groups such that the symmetric units of KG satisfy the solvability identity (x 1, x 2,…, x 2 n ) o = 1, for some n. 相似文献
53.
54.
We first consider the group inverses of the block matrices ( A 0 B C ) over a weakly finite ring. Then we study the sufficient and necessary conditions for the existence and the representations of the group inverses of the block matrices ( A C B D ) over a ring with unity 1 under the following conditions respectively: (i) B = C, D = 0, B# and (BπA) # both exist; (ii) B is invertible and m = n; (iii) A# and (D - CA#B)# both exist, C = CAA# , where A and D are m × m and n × n matrices, respectively. 相似文献
56.
Collins Okon Edet Francisco Cleiton E. Lima Carlos Alberto S. Almeida Norshamsuri Ali Muhammad Asjad 《Entropy (Basel, Switzerland)》2022,24(8)
We investigate quantum information by a theoretical measurement approach of an Aharanov–Bohm (AB) ring with Yukawa interaction in curved space with disclination. We obtained the so-called Shannon entropy through the eigenfunctions of the system. The quantum states considered come from Schrödinger theory with the AB field in the background of curved space. With this entropy, we can explore the quantum information at the position space and reciprocal space. Furthermore, we discussed how the magnetic field, the AB flux, and the topological defect influence the quantum states and the information entropy. 相似文献
57.
无挠左(右)Artin环是拟Frobenius环乌成伟(吉林工学院基础部,长春130012)关键词内积,左(右)内零化子,自内射环.分类号AMS(1991)16D50/CCLO153.3设R为有1的左(右)Artin环,如果对于任一整数洲与r∈R,m... 相似文献
58.
Einar Steingrímsson 《Journal of Algebraic Combinatorics》2001,14(1):73-84
Let G be a simple graph on d vertices. We define a monomial ideal K in the Stanley-Reisner ring A of the order complex of the Boolean algebra on d atoms. The monomials in K are in one-to-one correspondence with the proper colorings of G. In particular, the Hilbert polynomial of K equals the chromatic polynomial of G.The ideal K is generated by square-free monomials, so A/K is the Stanley-Reisner ring of a simplicial complex C. The h-vector of C is a certain transformation of the tail
T(n) = n
d – (n) of the chromatic polynomial of G. The combinatorial structure of the complex C is described explicitly and it is shown that the Euler characteristic of C equals the number of acyclic orientations of G. 相似文献
59.
In this paper using elliptical resonant ring we proposed a channel drop filter based on photonic crystal structures suitable for optical communication applications. The drop efficiency and the quality factor of our proposed filter is 100% and 647. We also investigated the optical properties of different configurations of the proposed photonic crystal ring resonator such as vertical ring, dual ring and triple ring structures. According to the results different configurations show different optical properties, so for vertical, double and triple ring configurations the quality factor will be 387, 865 and 1559, respectively. 相似文献
60.
V. N. Paimushin V. A. Ivanov S. N. Bobrov T. V. Polyakova 《Mechanics of Composite Materials》2000,36(3):185-192
The solution of the stability problem of a circular sandwich ring under uniform external pressure is given in a refined statement.
The need to determinate the precritical stresses in load-bearing layers in the refined statement with regard to the transverse
compression of the core is established, which is the basis for the detection of the mixed flexural buckling forms (BFs) with
more than two half-waves along the circumferential coordinate (n>2). It is found that sandwich structures with a determining
parameter of transverse compression corresponding to the limit of transition from the mixed BFs to synphasic ones are the
most efficient from the weight viewpoint.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 317–328, May–June, 2000. 相似文献