全文获取类型
收费全文 | 64480篇 |
免费 | 2782篇 |
国内免费 | 1454篇 |
专业分类
化学 | 43461篇 |
晶体学 | 360篇 |
力学 | 1892篇 |
综合类 | 10篇 |
数学 | 10047篇 |
物理学 | 12946篇 |
出版年
2023年 | 464篇 |
2022年 | 371篇 |
2021年 | 898篇 |
2020年 | 930篇 |
2019年 | 948篇 |
2018年 | 1246篇 |
2017年 | 1045篇 |
2016年 | 2055篇 |
2015年 | 1856篇 |
2014年 | 1948篇 |
2013年 | 4139篇 |
2012年 | 4649篇 |
2011年 | 4773篇 |
2010年 | 2839篇 |
2009年 | 2725篇 |
2008年 | 3875篇 |
2007年 | 3862篇 |
2006年 | 3358篇 |
2005年 | 3350篇 |
2004年 | 3295篇 |
2003年 | 2556篇 |
2002年 | 2269篇 |
2001年 | 1264篇 |
2000年 | 1054篇 |
1999年 | 769篇 |
1998年 | 620篇 |
1997年 | 552篇 |
1996年 | 631篇 |
1995年 | 453篇 |
1994年 | 461篇 |
1993年 | 484篇 |
1992年 | 499篇 |
1991年 | 410篇 |
1990年 | 401篇 |
1989年 | 373篇 |
1988年 | 320篇 |
1987年 | 308篇 |
1986年 | 284篇 |
1985年 | 479篇 |
1984年 | 450篇 |
1983年 | 308篇 |
1982年 | 397篇 |
1981年 | 384篇 |
1980年 | 348篇 |
1979年 | 321篇 |
1978年 | 302篇 |
1977年 | 260篇 |
1976年 | 310篇 |
1975年 | 273篇 |
1974年 | 284篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
G. Montero L. Gonzlez E. Flrez M. D. García A. Surez 《Numerical Linear Algebra with Applications》2002,9(3):239-247
Parallel preconditioners are presented for the solution of general linear systems of equations. The computation of these preconditioners is achieved by orthogonal projections related to the Frobenius inner product. So, minM∈??∥AM?I∥ F and matrix M0∈?? corresponding to this minimum (?? being any vectorial subspace of ??n(?)) are explicitly computed using accumulative formulae in order to reduce computational cost when subspace ?? is extended to another one containing it. Every step, the computation is carried out taking advantage of the previous one, what considerably reduces the amount of work. These general results are illustrated with the subspace of matrices M such that AM is symmetric. The main application is developed for the subspace of matrices with a given sparsity pattern which may be constructed iteratively by augmenting the set of non‐zero entries in each column. Finally, the effectiveness of the sparse preconditioners is illustrated with some numerical experiments. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
72.
NaY zeolite samples loaded with sodium metal by vapor phase deposition have been investigated using129Xe NMR spectroscopy. At low sodium concentration, the129Xe NMR spectrum showed three resonance lines which clearly indicate the existence of distinct domains in the zeolite sample. Such an observation suggests that the diffusion of the xenon atoms into each domain only occurs with respect to the NMR time scale (2.9 ms). As the sodium concentration increases, observation of a single broad line indicate a macroscopic homogenization of the system. The shift of this line is explained in part due to a paramagnetic interaction between the xenon atoms and the unpaired electrons of particles containing an odd number of sodium atoms. The linewidth is due to the distribution of the local magnetic fields partially averaged by the rapid motion of the xenon atoms and to the statistical distribution of the sodium particles in the supercage cavities. The paramagnetic interaction vanishes with the oxidation of the sample leading to a narrowing and a shift of the line to higher magnetic fields. 相似文献
73.
We study spectral properties of discrete Schrödinger operators with potentials obtained via dimerization of a class of aperiodic sequences. It is shown that both the nature of the autocorrelation measure of a regular sequence and the presence of generic (full probability) singular continuous spectrum in the hull of primitive and palindromic (four block substitution) potentials are robust under dimerization. Generic results also hold for circle potentials. We illustrate these results with numerical studies of the quantum mean square displacement as a function of time. The numerical techniques provide a very fast algorithm for the time evolution of wave packets. 相似文献
74.
75.
76.
77.
78.
Marí a J. Martí n Dragan Vukotic 《Proceedings of the American Mathematical Society》2006,134(6):1701-1705
We show that every composition operator which is an isometry of the Dirichlet space is induced by a univalent full map of the disk into itself that fixes the origin. This is an analogue of the Hardy space result for inner functions due to Nordgren. The proof relies on the Stone-Weierstrass theorem and the Riesz representation theorem.
79.
80.
This paper attempts to develop a theory of sufficiency in the setting of non-commutative algebras parallel to the ideas in
classical mathematical statistics. Sufficiency of a coarse-graining means that all information is extracted about the mutual
relation of a given family of states. In the paper sufficient coarse-grainings are characterized in several equivalent ways
and the non-commutative analogue of the factorization theorem is obtained. As an application we discuss exponential families.
Our factorization theorem also implies two further important results, previously known only in finite Hilbert space dimension,
but proved here in generality: the Koashi-Imoto theorem on maps leaving a family of states invariant, and the characterization
of the general form of states in the equality case of strong subadditivity.
Supported by the EU Research Training Network Quantum Probability with Applications to Physics, Information Theory and Biology
and Center of Excellence SAS Physics of Information I/2/2005.
Supported by the Hungarian grant OTKA T032662 相似文献