全文获取类型
收费全文 | 96832篇 |
免费 | 2182篇 |
国内免费 | 426篇 |
专业分类
化学 | 47485篇 |
晶体学 | 1201篇 |
力学 | 4209篇 |
综合类 | 13篇 |
数学 | 11138篇 |
物理学 | 35394篇 |
出版年
2022年 | 725篇 |
2021年 | 787篇 |
2020年 | 910篇 |
2019年 | 779篇 |
2018年 | 1065篇 |
2017年 | 983篇 |
2016年 | 1921篇 |
2015年 | 1410篇 |
2014年 | 1864篇 |
2013年 | 4339篇 |
2012年 | 4028篇 |
2011年 | 4865篇 |
2010年 | 3330篇 |
2009年 | 3204篇 |
2008年 | 4464篇 |
2007年 | 4212篇 |
2006年 | 4013篇 |
2005年 | 3571篇 |
2004年 | 3191篇 |
2003年 | 2739篇 |
2002年 | 2513篇 |
2001年 | 3803篇 |
2000年 | 2814篇 |
1999年 | 2015篇 |
1998年 | 1489篇 |
1997年 | 1452篇 |
1996年 | 1371篇 |
1995年 | 1234篇 |
1994年 | 1177篇 |
1993年 | 1116篇 |
1992年 | 1494篇 |
1991年 | 1319篇 |
1990年 | 1236篇 |
1989年 | 1092篇 |
1988年 | 1049篇 |
1987年 | 1130篇 |
1986年 | 964篇 |
1985年 | 1371篇 |
1984年 | 1305篇 |
1983年 | 958篇 |
1982年 | 979篇 |
1981年 | 951篇 |
1980年 | 910篇 |
1979年 | 1017篇 |
1978年 | 1038篇 |
1977年 | 1049篇 |
1976年 | 939篇 |
1975年 | 835篇 |
1974年 | 862篇 |
1973年 | 737篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
171.
172.
173.
Selecting, modifying or creating appropriate problems for mathematics class has become an activity of increaing importance in the professional development of German mathematics teachers. But rather than asking in general: “What is a good problem?” there should be a stronger emphasis on considering the specific goal of a problem, e.g.: “What are the ingredients that make a problem appropriate for initiating a learning process” or “What are the characteristics that make a problem appropriate for its use in a central test?” We propose a guiding scheme for teachers that turns out to be especially helpful, since the newly introduced orientation on outcome standards a) leads to a critical predominance of test items and b) expects teachers to design adequate problems for specific learning processes (e.g. problem solving, reasoning and modelling activities). 相似文献
174.
Y. A. Coutinho J. A. Martins Simões C. M. Porto 《Zeitschrift fur Physik C Particles and Fields》1997,73(4):705-709
In this paper we investigate the effects of heavy Majorana neutrinos in the reaction e + e ? → W + W ?. We consider neutrino masses in the 1–10 TeV region. We show that at LEP II and NLC energies it is possible to use this processes to verify indirect evidence of heavy neutral particles with mixing angles of the order sin2 α = 0.01. We discuss the unitarity restrictions that can be obtained for vector singlet and fermion-mirror-fermion models. 相似文献
175.
In this article we have studied the nonlinear interaction between ellipticity and dissipation in a set of model equations (1.1) and established the relation between this interaction and chaos. In addition to theoretical investigations, extensive numerical simulations with these equations have been made, and different routes to chaos have been found. The numerical studies have revealed the chaotic nature of the solutions. 相似文献
176.
A. Hoffknecht O. Uwira A. Frank S. Schennach W. Spies M. Wagner S. Schippers A. Müller R. Becker M. Kleinod N. Angert P.H. Mokler 《Hyperfine Interactions》1998,114(1-4):257-261
The origin of the widely observed enhancement of rates for electron-ion recombination at very low energies is still unknown.
We investigated the recombination of Au25+ with free electrons in a merged-beams experiment at the UNILAC accelerator of the GSI in Darmstadt. At E
rel= 0 eV we found an enormous enhancement factor of 365 compared to the theory of radiative recombination. An increase of the
electron density by a factor of 10 had not much influence on the measured rate coefficient.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
177.
178.
S. Pumplün 《manuscripta mathematica》1998,97(1):93-108
For a Brauer–Severi variety X over a field k of characteristic not two, every symmetric bilinear space over X up to Witt equivalence is defined over k.
Received: 2 February 1998 相似文献
179.
High resolution finite difference schemes for solving the nonlinear model Boltzmann equations are presented for the computations of rarefied gas flows. The discrete ordinate method is first applied to remove the velocity space dependency of the distribution function which renders the model Boltzmann equation in phase space to a set of hyperbolic conservation laws with source terms in physical space. Then a high order essentially nonoscillatory method due to Harten et al. (J. Comput. Phys. 71, 231, 1987) is adapted and extended to solve them. Explicit methods using operator splitting and implicit methods using the lower-upper factorization are described to treat multidimensional problems. The methods are tested for both steady and unsteady rarefied gas flows to illustrate its potential use. The computed results using model Boltzmann equations are found to compare well both with those using the direct simulation Monte Carlo results in the transitional regime flows and those with the continuum Navier-Stokes calculations in near continuum regime flows. 相似文献
180.
C. A. Lütken 《Journal of statistical physics》1995,78(1-2):441-451
Charge transport in two dimensions provides an ideal laboratory for investigating parameter space geometries. The Onsager relations for anisotropic transport in a parity-violating external field endow these spaces with a highly nontrivial complex (and Kähler) structure, which can be given a simple geometrical interpretation. A large class of Coulomb gases exhibiting this structure have a generalized Kramers-Wannier symmetry (complexfield duality) which is contained in the modular group. Knowledge of this symmetry and the degrees of freedom encoded in the Coulomb gas appear to be sufficient to determine the global phase diagram and the renormalization group fixed-point structure, including the critical exponents. This accounts for all the scaling behavior observed so far in the quantum Hall system. 相似文献