全文获取类型
收费全文 | 2250篇 |
免费 | 69篇 |
国内免费 | 106篇 |
专业分类
化学 | 478篇 |
晶体学 | 6篇 |
力学 | 127篇 |
综合类 | 24篇 |
数学 | 904篇 |
物理学 | 886篇 |
出版年
2024年 | 2篇 |
2023年 | 55篇 |
2022年 | 22篇 |
2021年 | 33篇 |
2020年 | 34篇 |
2019年 | 35篇 |
2018年 | 43篇 |
2017年 | 55篇 |
2016年 | 63篇 |
2015年 | 58篇 |
2014年 | 71篇 |
2013年 | 211篇 |
2012年 | 90篇 |
2011年 | 91篇 |
2010年 | 85篇 |
2009年 | 142篇 |
2008年 | 105篇 |
2007年 | 132篇 |
2006年 | 127篇 |
2005年 | 82篇 |
2004年 | 77篇 |
2003年 | 67篇 |
2002年 | 78篇 |
2001年 | 74篇 |
2000年 | 64篇 |
1999年 | 88篇 |
1998年 | 53篇 |
1997年 | 61篇 |
1996年 | 43篇 |
1995年 | 50篇 |
1994年 | 29篇 |
1993年 | 37篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 16篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 13篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2425条查询结果,搜索用时 262 毫秒
1.
M. Gorkunov M. Lapine E. Shamonina K.H. Ringhofer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):263-269
Effective magnetic properties of a composite meta-material consisting of periodically arranged circular conductive elements
are studied theoretically. A general expression for the effective bulk permeability is obtained with mutual effects and lattice
ordering being taken into account. The resonance frequency of the permeability is found to be strongly dependent on the size
and shape of the unit cell. Frequency dispersion of the permeability is studied with special attention paid to the frequency
range, where negative values of the permeability are possible. Corresponding recommendations for optimisation of the meta-materials
with negative permeability are made. The results are confirmed by numerical simulations of the finite structure behaviour
in an external magnetic field.
Received 19 April 2002 Published online 31 July 2002 相似文献
2.
3.
文贤章 《高校应用数学学报(A辑)》2002,17(3):291-302
利用最大值原理结合上、下解的方法,讨论了一类具有扩散的竞争-捕食的Lotka-Volterra系统静态解的存在性与持续生存。 相似文献
4.
在国家863CIMS目标产品CAPPFramework系统的基础上,研究了面向对象的信息建模技术、信息模型驱动的所见即所得工艺设计技术、工作流技术.并在此基础上进行集成化、智能化计算机辅助工艺设计(CAPP)的应用与开发,实现了工艺设计的自动化,基本达到了在信息集成基础上的工艺设计与工艺信息管理一体化的目的,对企业的CAPP实施具有一定的参考价值. 相似文献
5.
S. Carl 《Journal of Differential Equations》2004,199(1):77-95
In this paper we consider systems of quasilinear elliptic variational inequalities, and prove the existence of minimal and maximal (in the set theoretical sense) solutions within some ordered interval of an appropriately defined pair of sub- and supersolutions. We show that the notion of sub- and supersolutions of variational inequalities introduced here is consistent with the usual notion of sub-supersolutions for (variational) equations. For weakly coupled quasimonotone systems of variational inequalities the existence of smallest and greatest solutions is proved. 相似文献
6.
L.-H. Tang P. Smilauer D.D. Vvedensky 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):409-412
Two types of mechanisms are proposed for mound coarsening during unstable epitaxial growth: stochastic, due to deposition
noise, and deterministic, due to mass currents driven by surface energy differences. Both yield the relation H=(RWL)2 between the typical mound height W, mound size L, and the film thickness H. An analysis of simulations and experimental data shows that the parameter R saturates to a value which discriminates sharply between stochastic () and deterministic () coarsening. We derive a scaling relation between the coarsening exponent 1/z and the mound-height exponent which, for a saturated mound slope, yields .
Received: 11 November 1997 / Revised in final form: 28 November 1997 /
Accepted: 28 November 1997 相似文献
7.
Bing Yong HSIE 《数学学报(英文版)》2006,22(2):507-514
This paper gives a p-adic analogue of the Mackey theory, which relates representations of a group of type G - H × t A to systems of imprimitivity. 相似文献
8.
M. Gutowski I. Dabkowska J. Rak S. Xu J.M. Nilles D. Radisic K.H. Bowen Jr 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):431-439
The photoelectron spectra (PES) of anions of uracil-glycine and uracil-phenylalanine complexes reveal broad features with
maxima at 1.8 and 2.0 eV. The results of ab initio density functional B3LYP and second order M?ller-Plesset theory calculations indicate that the excess electron occupies a
π* orbital localized on uracil. The excess electron attachment to the complex can induce a barrier-free proton transfer (BFPT)
from the carboxylic group of glycine to the O8 atom of uracil. As a result, the four most stable structures of the anion of
uracil-glycine complex can be characterized as the neutral radical of hydrogenated uracil solvated by the anion of deprotonated
glycine. The similarity between the PES spectra for the uracil complexes with glycine and phenylalanine suggests that the
BFPT is also operative in the case of the latter anionic species. The BFPT to the O8 atom of uracil may be related to the
damage of nucleic acid bases by low energy electrons because the O8 atom is involved in a hydrogen bond with adenine in the
standard Watson-Crick pairing scheme.
Received 6 April 2002 Published online 13 September 2002 相似文献
9.
10.
X. Yang 《Applied Surface Science》2006,252(10):3647-3657
The room-temperature adsorption and thermally induced processes of propionic acid and pyruvic acid on Ni(1 0 0) have been investigated by electron energy loss spectroscopy (EELS). Computational vibrational analysis of the optimized bidentate structures for acid-Ni model complexes (involving the organic acid and a Ni atom) has been performed by using the two-layer ONIOM method with the Density Functional Theory and used to interpret the vibrational EELS data. Dehydrogenation of the hydroxyl group is found to result in bonding of the carboxylate group in the propionate and pyruvate adspecies to either a single Ni surface atom in a bidentate configuration or two neighbouring Ni atoms in a bridge configuration. Given the similarities in the total energies and related vibrational frequencies obtained by the calculations in the case of pyruvate adspecies, it is difficult to differentiate the alternate adsorption structure, in which the keto O and hydroxyl O atoms are bonded to a Ni atom in a five-member chelate ring configuration. Furthermore, temperature-dependent EELS studies show that both the propionate and pyruvate adspecies could decompose upon annealing to above 400 K and further dissociate to CO adspecies above 550 K and to C and/or O above 600 K. 相似文献