全文获取类型
收费全文 | 67907篇 |
免费 | 2112篇 |
国内免费 | 174篇 |
专业分类
化学 | 43553篇 |
晶体学 | 386篇 |
力学 | 1880篇 |
综合类 | 4篇 |
数学 | 10990篇 |
物理学 | 13380篇 |
出版年
2023年 | 490篇 |
2022年 | 653篇 |
2021年 | 920篇 |
2020年 | 975篇 |
2019年 | 992篇 |
2018年 | 1304篇 |
2017年 | 1117篇 |
2016年 | 2133篇 |
2015年 | 1878篇 |
2014年 | 1961篇 |
2013年 | 3946篇 |
2012年 | 4449篇 |
2011年 | 4709篇 |
2010年 | 2893篇 |
2009年 | 2516篇 |
2008年 | 4075篇 |
2007年 | 4033篇 |
2006年 | 3631篇 |
2005年 | 3454篇 |
2004年 | 2915篇 |
2003年 | 2393篇 |
2002年 | 2096篇 |
2001年 | 1314篇 |
2000年 | 1123篇 |
1999年 | 836篇 |
1998年 | 650篇 |
1997年 | 615篇 |
1996年 | 749篇 |
1995年 | 515篇 |
1994年 | 565篇 |
1993年 | 551篇 |
1992年 | 567篇 |
1991年 | 481篇 |
1990年 | 456篇 |
1989年 | 419篇 |
1988年 | 357篇 |
1987年 | 361篇 |
1986年 | 324篇 |
1985年 | 506篇 |
1984年 | 476篇 |
1983年 | 324篇 |
1982年 | 432篇 |
1981年 | 390篇 |
1980年 | 363篇 |
1979年 | 327篇 |
1978年 | 304篇 |
1976年 | 314篇 |
1975年 | 279篇 |
1974年 | 273篇 |
1973年 | 286篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Sauer, Shelah, Vapnik and Chervonenkis proved that if a set system on n vertices contains many sets, then the set system has full trace on a large set. Although the restriction on the size of the
groundset cannot be lifted, Frankl and Pach found a trace structure that is guaranteed to occur in uniform set systems even
if we do not bound the size of the groundset. In this note we shall give three sequences of structures such that every set
system consisting of sufficiently many sets contains at least one of these structures with many sets. 相似文献
12.
In this Note, we present a result concerning the non existence of linear monotone schema with fixed stencil on regular meshes for some linear parabolic equation in two dimensions. The parabolic equations of interest arise from non isotropic diffusion modelling. A corollary is that no linear monotone 9 points-schemes can be designed for the one-dimensional heat equation emerged in the plane with an arbitrary direction of diffusion. Some applications of this result are provided: for the Fokker–Planck–Lorentz model for electrons in the context of plasma physics; all linear monotone scheme for the one-dimensional hyperbolic heat equation treated as a two-dimensional problem are not consistent in the diffusion limit for an arbitrary direction of propagation. We also examine the case of the Landau equation. To cite this article: C. Buet, S. Cordier, C. R. Acad. Sci. Paris, Ser. I 340 (2005). 相似文献
13.
We prove that the generalized random walks associated to a root system R in and a nonnegative multiplicity function k defined on R, converge in distribution (if suitably normalized) to a Markov process with càdlàg trajectories and infinitesimal generator a differential-difference operator on which generalizes the usual Laplacian. To cite this article: L. Gallardo, L. Godefroy, C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献
14.
The aim of this paper is to study I-fuzzy topologies (fuzzy topologies in
ostak's sense) derived from decreasing families of I-topologies (fuzzy topologies in Chang's sense), defined on a set X. 相似文献
15.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
16.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C
1 transformation. 相似文献
17.
Régine Barthelmé 《Comptes Rendus Mathematique》2005,341(11):689-694
This Note introduces a new integral form of the charge and current deposition scheme given in 1992 by Villasenor and Buneman, which permits the conservation of charge in PIC codes. This integral form extends directly to higher order spline shape factors, whose use produces less numerical noise. We thus get a discrete charge conserving method for high order shape factors. This method extends easily to nonuniform Cartesian grids for first order shape factors. To cite this article: R. Barthelmé, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献
18.
C Guéret N Jussien O Lhomme C Pavageau C Prins 《The Journal of the Operational Research Society》2003,54(5):458-465
In this paper, we describe an aircraft loading problem submitted by the French military agency (DGA) as part of a more general military airlift planning problem. It can be viewed as a kind of bi-dimensional bin-packing problem, with heterogeneous bins and several additional constraints. We introduce two-phase methods for solving this NP-hard problem. The first phase consists in building good initial solutions, thanks to two fast algorithms: a list-based heuristic and a loading pattern generation method. Both algorithms call a constraint-based subroutine, able to determine quickly if the items already loaded can be reshuffled to accommodate a new object. The second phase improves these preliminary solutions using local search techniques. Results obtained on real data sets are presented. 相似文献
19.
Let K be ? or an imaginary quadratic number field, and q ∈ K an integer with ¦q¦ > 1. We give a quantitative version of Σn≥1 an/(qn ? 1) ? K for non-zero periodic sequences (an) in K of period length ≤ 2. As a corollary, we get a quantitative version of the linear independence over K of 1, the q-harmonic series, and a q-analogue of log 2. A similar result on 1, the q-harmonic series, and a q-analogue of ζ(2) is also proved. Mathematics Subject Classification (2000): 11J72, 11J82 相似文献
20.
Various physical systems of dispersive waves admit solutions in the form of generalized solitary waves. Such waves result from the resonance between a long localized wave and short periodic oscillations. Many estimates (rigorous and numerical) have been given for the amplitude of the ripples in the tail of the generalized solitary wave when its central part has a sech2 shape. This Note provides estimates (not yet rigorous) for the ripple amplitude when the central part is flat and wide. To cite this article: C. Fochesato, F. Dias, C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献