全文获取类型
收费全文 | 4631篇 |
免费 | 227篇 |
国内免费 | 444篇 |
专业分类
化学 | 2082篇 |
晶体学 | 12篇 |
力学 | 38篇 |
综合类 | 20篇 |
数学 | 2737篇 |
物理学 | 413篇 |
出版年
2024年 | 4篇 |
2023年 | 61篇 |
2022年 | 102篇 |
2021年 | 98篇 |
2020年 | 141篇 |
2019年 | 141篇 |
2018年 | 139篇 |
2017年 | 142篇 |
2016年 | 105篇 |
2015年 | 118篇 |
2014年 | 166篇 |
2013年 | 625篇 |
2012年 | 139篇 |
2011年 | 180篇 |
2010年 | 144篇 |
2009年 | 228篇 |
2008年 | 272篇 |
2007年 | 279篇 |
2006年 | 257篇 |
2005年 | 247篇 |
2004年 | 231篇 |
2003年 | 218篇 |
2002年 | 197篇 |
2001年 | 156篇 |
2000年 | 151篇 |
1999年 | 121篇 |
1998年 | 126篇 |
1997年 | 129篇 |
1996年 | 77篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 37篇 |
1992年 | 38篇 |
1991年 | 18篇 |
1990年 | 11篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有5302条查询结果,搜索用时 15 毫秒
111.
Volker Runde 《Transactions of the American Mathematical Society》2006,358(1):391-402
Let be a locally compact group, and let denote the space of weakly almost periodic functions on . We show that, if is a -group, but not compact, then the dual Banach algebra does not have a normal, virtual diagonal. Consequently, whenever is an amenable, non-compact -group, is an example of a Connes-amenable, dual Banach algebra without a normal, virtual diagonal. On the other hand, there are amenable, non-compact, locally compact groups such that does have a normal, virtual diagonal.
112.
Marcel Herzog 《Journal of Combinatorial Theory, Series A》2008,115(7):1235-1245
Given integers k,l?2, where either l is odd or k is even, we denote by n=n(k,l) the largest integer such that each element of An is a product of k cycles of length l. For an odd l, k is the diameter of the undirected Cayley graph Cay(An,Cl), where Cl is the set of all l-cycles in An. We prove that if k?2 and l?9 is odd and divisible by 3, then . This extends earlier results by Bertram [E. Bertram, Even permutations as a product of two conjugate cycles, J. Combin. Theory 12 (1972) 368-380] and Bertram and Herzog [E. Bertram, M. Herzog, Powers of cycle-classes in symmetric groups, J. Combin. Theory Ser. A 94 (2001) 87-99]. 相似文献
113.
Chen-bo Zhu 《Proceedings of the American Mathematical Society》1998,126(10):3125-3130
Let be the reductive dual pair . We show that if is a representation of (respectively ) obtained from duality correspondence with some representation of (respectively ), then its Gelfand-Kirillov dimension is less than or equal to
(respectively ).
(respectively ).
114.
We study those functions that can be written as a finite sum of periodic integer valued functions. On ℤ we give three different
characterizations of these functions. For this we prove that the existence of a real valued periodic decomposition of a ℤ
→ ℤ function implies the existence of an integer valued periodic decomposition with the same periods. This result depends
on the representation of the greatest common divisor of certain polynomials with integer coefficients as a linear combination
of the given polynomials where the coefficients also belong to ℤ[x]. We give an example of an ℤ → {0, 1} function that has a bounded real valued periodic decomposition but does not have a
bounded integer valued periodic decomposition with the same periods. It follows that the class of bounded ℤ → ℤ functions
has the decomposition property as opposed to the class of bounded ℝ → ℤ functions. If the periods are pairwise commensurable
or not prescribed, then we get more general results.
Supported by OTKA grants T 43623 and K 61908. 相似文献
115.
Moufang sets were introduced by Jacques Tits in order to understand isotropic linear algebraic groups of relative rank one, but the notion is more general. We describe a new class of Moufang sets, arising from so‐called mixed groups of type in characteristic 2, obtained as the fixed point set under a suitable involution. 相似文献
116.
117.
Let X denote the restricted Lie superalgebras of Cartan type W, S, H, or K over a field of characteristic p > 3, and 𝔄 the corresponding underlying superalgebra of X. Employing the invariance of the filtration of X we construct an isomorphism of Aut X to Aut(𝔄:X), the admissible automorphism group of the associative super-commutative superalgebra 𝔄. Moreover, it is proved that the group isomorphism above maps the standard normal series of Aut X to the one of Aut(𝔄:X), and also maps the homogeneous automorphism group of X to the admissible homogeneous automorphism group of 𝔄. 相似文献
118.
119.
V. I. Zabolotskii M. V. Sharafan N. V. Shel’deshov 《Russian Journal of Electrochemistry》2008,44(10):1127-1134
Polarization properties of electromembrane systems (EMS) consisting of a heterogeneous membrane, either the MK-41 phosphonic acid membrane or the MK-40 sulfonic acid membrane, and dilute sodium chloride solutions are investigated with the rotating membrane disk method. For the MK-41/0.01 M NaCl and MK-41/0.001 M NaCl EMS, effective ion transport numbers and partial current-voltage curves (CVC) are measured for sodium and hydrogen ions, and limiting-current densities and the diffusion-layer thickness are calculated as functions of the rotation rate of the membrane disk. With the theory of the overlimiting state of EMS, internal parameters of the systems under investigation—the diffusion-layer thickness, the space-charge distribution, and electric-field strengths in the diffusion layer and in the membrane—are calculated from experimentally obtained CVC and the dependence of effective transport numbers on current density. The catalytic influence of ionogenic groups on the dissociation rate of water is analyzed quantitatively. Partial CVC for H+ ions are calculated for the space-charge region in MK-40 and MK-41 membranes. Analogous CVC for bipolar membranes containing sulfonic acid and phosphonic acid groups are compared. The dissociation mechanism of water is the same in all EMS and is independent of the membrane type and the nature of the functional groups. 相似文献
120.
Lidija Fras Zemljič Zdenka Peršin Per Stenius Karin Stana Kleinschek 《Cellulose (London, England)》2008,15(5):681-690
The influence of peroxide bleaching and slack-mercerization on the amount of acidic groups in regenerated fibres (viscose,
modal and lyocell) were studied. Conductometric titration was used to determine the total content of acidic carboxylic groups.
Polyelectrolyte titration was used for surface and total charge determination, and to obtain information about the charge
distribution and accessibilities of charged groups. Changes in fibre crystallinity to pre-treatment processes were characterized
using iodine sorption (Schwertassek method) and correlated to treatments and the amount of carboxylic groups. For all three
types of fibres the amount of accessible carboxyl groups was lowered by an increase in the degree of crystallinity. Bleaching
with hydrogen peroxide causes some oxidative cellulose damage and, therefore, a larger amount of carboxyl groups (presumably
formed at the end of cellulose chains). Slack-mercerization did not significantly change the total amount of acidic groups
in the fibres, but their accessibility to cationic polyelectrolytes, in particular to polymers with high molecular weight
was substantially lowered.
Lidija Fras Zemljič, Zdenka Peršin, and Karin Stana Kleinschek are the members of the European Polysaccharide Network of Excellence
(EPNOE). 相似文献