全文获取类型
收费全文 | 25849篇 |
免费 | 2805篇 |
国内免费 | 1627篇 |
专业分类
化学 | 7136篇 |
晶体学 | 179篇 |
力学 | 1404篇 |
综合类 | 207篇 |
数学 | 7696篇 |
物理学 | 13659篇 |
出版年
2024年 | 29篇 |
2023年 | 172篇 |
2022年 | 374篇 |
2021年 | 392篇 |
2020年 | 489篇 |
2019年 | 439篇 |
2018年 | 461篇 |
2017年 | 580篇 |
2016年 | 652篇 |
2015年 | 549篇 |
2014年 | 874篇 |
2013年 | 1730篇 |
2012年 | 1289篇 |
2011年 | 1497篇 |
2010年 | 1345篇 |
2009年 | 3741篇 |
2008年 | 3109篇 |
2007年 | 1773篇 |
2006年 | 1311篇 |
2005年 | 1145篇 |
2004年 | 1114篇 |
2003年 | 876篇 |
2002年 | 770篇 |
2001年 | 640篇 |
2000年 | 610篇 |
1999年 | 507篇 |
1998年 | 548篇 |
1997年 | 475篇 |
1996年 | 303篇 |
1995年 | 427篇 |
1994年 | 367篇 |
1993年 | 295篇 |
1992年 | 342篇 |
1991年 | 299篇 |
1990年 | 156篇 |
1989年 | 163篇 |
1988年 | 103篇 |
1987年 | 54篇 |
1986年 | 61篇 |
1985年 | 44篇 |
1984年 | 30篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Piotr Biler 《Reports on Mathematical Physics》2003,52(2):205-225
We study asymptotic properties of solutions to an extension to arbitrary dimensions of the astrophysical model proposed by Chavanis et al. to explain phenomena of gravitational collapse in clouds of self-gravitating particles. In particular, we show that in the two-dimensional case the solutions can be continued to global ones, while in three space dimensions large data of negative energy blow up in a finite time. Relations between isothermal, Streater's energy-transport and the present models are also studied. 相似文献
42.
首先通过集代数得到了Stone代数的表示定理,然后证明了每一个Stone代数均嵌入到某个集合X上的一个Stone映射类S中. 相似文献
43.
We consider toy cosmological models in which a classical, homogeneous, spinor field provides a dominant or sub-dominant contribution to the energy-momentum tensor of a flat Friedmann-Robertson-Walker universe. We find that, if such a field were to exist, appropriate choices of the spinor self-interaction would generate a rich variety of behaviors, quite different from their widely studied scalar field counterparts. We first discuss solutions that incorporate a stage of cosmic inflation and estimate the primordial spectrum of density perturbations seeded during such a stage. Inflation driven by a spinor field turns out to be unappealing as it leads to a blue spectrum of perturbations and requires considerable fine-tuning of parameters. We next find that, for simple, quartic spinor self-interactions, non-singular cyclic cosmologies exist with reasonable parameter choices. These solutions might eventually be incorporated into a successful past- and future-eternal cosmological model free of singularities. In an Appendix, we discuss the classical treatment of spinors and argue that certain quantum systems might be approximated in terms of such fields. 相似文献
44.
Gerhard Starke 《Numerische Mathematik》1997,78(1):103-117
Summary. The convergence rate of Krylov subspace methods for the solution of nonsymmetric systems of linear equations, such as GMRES
or FOM, is studied. Bounds on the convergence rate are presented which are based on the smallest real part of the field of
values of the coefficient matrix and of its inverse. Estimates for these quantities are available during the iteration from
the underlying Arnoldi process. It is shown how these bounds can be used to study the convergence properties, in particular,
the dependence on the mesh-size and on the size of the skew-symmetric part, for preconditioners for finite element discretizations
of nonsymmetric elliptic boundary value problems. This is illustrated for the hierarchical basis and multilevel preconditioners
which constitute popular preconditioning strategies for such problems.
Received May 3, 1996 相似文献
45.
46.
Electric fields of the anions, cations and neutral forms of 2-aminopurine and 6-thioguanine have been mapped. Certain important
features of the maps are similar to those found earlier in the neutral and ionic forms of adenine and guanine. The computed
electric field patterns satisfactorily explain reactive sites and biological activity of the molecules. 相似文献
47.
We derive and analyse four algorithms for computing the current induced on a thin straight wire by a transient electric field.
They all involve solving the thin wire electric field integral equations (EFIEs) and consist of a very accurate differential
equations solver together with various schemes to approximate the vector potential integral equation. We carry out a rigorous
numerical stability analysis of each of these methods. This has not previously been done for solution schemes for the thin
wire EFIEs. Each scheme is shown to be stable and convergent provided the radius of the wire is small enough for the thin
wire equations to be a valid model. 相似文献
48.
用于留数算术中的数值/留数/数值的转换 总被引:1,自引:0,他引:1
介绍用光学方法完成留数算术中的数值/留数/数值的转换,并附有实验结果。 相似文献
49.
Lei Liu 《Journal of Mathematical Analysis and Applications》2007,328(2):1484-1486
In this note, we generalize the inequality about the trace of positive semidefinite matrix trk(AB)?k(trA)k(trB) to Hilbert space, and obtain a relevant inequality about positive trace class operator. 相似文献
50.
Wei-yi SU~ 《中国科学A辑(英文版)》2007,50(7):1005-1014
The Lipschitz class Lipαon a local field K is defined in this note,and the equivalent relationship between the Lipschitz class Lipαand the Holder type space C~α(K)is proved.Then,those important characteristics on the Euclidean space R~n and the local field K are compared,so that one may interpret the essential differences between the analyses on R~n and K.Finally,the Cantor type fractal functionθ(x)is showed in the Lipschitz class Lip(m,K),m<(ln 2/ln 3). 相似文献