全文获取类型
收费全文 | 15482篇 |
免费 | 678篇 |
国内免费 | 7篇 |
学科分类
数理化 | 16167篇 |
出版年
2023年 | 124篇 |
2022年 | 84篇 |
2021年 | 157篇 |
2020年 | 232篇 |
2019年 | 251篇 |
2018年 | 226篇 |
2017年 | 235篇 |
2016年 | 535篇 |
2015年 | 477篇 |
2014年 | 526篇 |
2013年 | 996篇 |
2012年 | 1205篇 |
2011年 | 1292篇 |
2010年 | 696篇 |
2009年 | 541篇 |
2008年 | 1116篇 |
2007年 | 1109篇 |
2006年 | 993篇 |
2005年 | 942篇 |
2004年 | 779篇 |
2003年 | 623篇 |
2002年 | 547篇 |
2001年 | 202篇 |
2000年 | 199篇 |
1999年 | 124篇 |
1998年 | 99篇 |
1997年 | 97篇 |
1996年 | 139篇 |
1995年 | 98篇 |
1994年 | 75篇 |
1993年 | 103篇 |
1992年 | 85篇 |
1991年 | 62篇 |
1990年 | 57篇 |
1989年 | 46篇 |
1988年 | 50篇 |
1987年 | 45篇 |
1986年 | 63篇 |
1985年 | 91篇 |
1984年 | 75篇 |
1983年 | 43篇 |
1982年 | 72篇 |
1981年 | 75篇 |
1980年 | 71篇 |
1979年 | 57篇 |
1978年 | 55篇 |
1977年 | 41篇 |
1976年 | 50篇 |
1975年 | 30篇 |
1974年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
H.D. Fonseca Filho R. Prioli M.P. Pires A.S. Lopes P.L. Souza F.A. Ponce 《Applied Physics A: Materials Science & Processing》2007,89(4):945-949
Atomic-force nanolithography was used to control the nucleation sites of InAs nanostructures on InP substrates. Indentations
with a wide range of dimensions were produced on InP. InAs nanostructures were selectively grown by metal organic vapor phase
epitaxy. It is shown that the number of active nucleation sites depends on the normal force applied during nanoindentation.
Crystalline defects introduced by nanoindentation are shown to be nucleation sites for these nanostructures. The presence
of screw dislocations within the grown nanostructures further supports this observation.
PACS 81.07.-b; 68.37.Ps; 81.16.Nd 相似文献
42.
Riccardo Rosso André M. Sonnet Epifanio G. Virga 《Continuum Mechanics and Thermodynamics》2002,14(1):127-136
kinks created in a biological membrane by the interaction with a movable bead. We arrive at the evolution equations for both the
bead and the membrane, whence we conclude that the force exerted on the bead by a fixed membrane points in the direction along
which the curvature of the membrane is more concentrated. This is the first step towards understanding the basic mechanism
behind the dynamics of protein aggregation which takes place on biological membranes.
Received November 6, 2001 / Published online February 4, 2002 相似文献
43.
44.
45.
In this Note we first introduce the concept of pullback asymptotic compactness. Next, we establish a result ensuring the existence of a pullback attractor for a non-autonomous dynamical system under the general assumptions of pullback asymptotic compactness and the existence of a pullback absorbing family of sets. Finally, we prove the existence of a pullback attractor for a non-autonomous 2D Navier–Stokes model in an unbounded domain, a case in which the theory of uniform attractors does not work since the non-autonomous term is quite general. To cite this article: T. Caraballo et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
46.
Eu3+ in ca. 10 wt% europium-exchanged Y-zeolite is partially reduced by treatment in hydrogen at 600°C to Eu2+. The reduction of Eu3+ is more readily achieved in Y-zeolite than in europium(III) oxide. The discrepancy in the extent of reduction as revealed by151Eu Mössbauer spectroscopy and near edge X-ray absorption fine structure (XANES) is associated with any difference in the recoil free fractions of Eu2+ and Eu3+ which may exist at 298 K and the enhanced sensitivity of the XANES to changes in the europium oxidation state. 相似文献
47.
A classical Fermi accelerator model (FAM) is known to show chaotic behavior. The FAM is defined by a free particle bouncing elastically from two rigid walls, one fixed and the other oscillating periodically in time. The central aim of this paper is to connect the quantum and the classical solutions to the FAM in the semiclassical limit. This goal is accomplished using a finite inverted parametric oscillator (FIPO), confined to a box withfixed walls, as an alternative representation of the FAM. In the FIPO representation, an explicit correspondence between classical and quantum limits is accomplished using a Husimi representation of the quasienergy eigenfunctions. 相似文献
48.
Theoretical models for Monte Carlo simulation of radiative processes, i.e. bremsstrahlung and characteristic x-ray emission, are presented. Possible strategies for simulating electron transport are briefly described. For mechanisms involving energy loss and angular deflections, difficulties for strict implementation of accurate numerical differential cross sections still remain due to the strong correlations between these variables. Practical solutions for the case of inelastic collisions and bremsstrahlung emission are described. Comparisons of simulation results with experimental data for several problems of interest in electron probe microanalysis are presented. 相似文献
49.
Alain-Yves LeRoux Marie-Noëlle LeRoux Jean-André Marti 《Comptes Rendus Mathematique》2004,339(4):313-316
The source waves are some particular solutions to genuinely non linear hyperbolic systems with a source term, whose propagation velocity is a constant determined by the roots of this source term. We propose a system of 2 equations on a 2 dimension space, which model the velocity field of the atmosphere near the ground. The source term is made of three parts: a given pressure gradient, a friction or aspiration effect and the Coriolis force. In the case where these parameters are constant, we build a solution which is a constant outside a circular crown. The internal circle represents the eye's wall of the hurricane and corresponds to a share shock wave. The external circle is a set generating the bifurcation which actually models the hurricane. To cite this article: A.-Y. LeRoux et al., C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
50.
Francisco Jesús Castro-Jiménez José Marı́a Ucha-Enrı́quez 《Comptes Rendus Mathematique》2004,338(6):461-466
We prove a duality theorem for some logarithmic -modules associated with a class of divisors. We also give some results for the locally quasi-homogeneous case. To cite this article: F.J. Castro-Jiménez, J.M. Ucha-Enr??quez, C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献