全文获取类型
收费全文 | 8499篇 |
免费 | 676篇 |
国内免费 | 266篇 |
专业分类
化学 | 2072篇 |
晶体学 | 19篇 |
力学 | 3605篇 |
综合类 | 120篇 |
数学 | 954篇 |
物理学 | 2671篇 |
出版年
2023年 | 51篇 |
2022年 | 90篇 |
2021年 | 177篇 |
2020年 | 200篇 |
2019年 | 188篇 |
2018年 | 134篇 |
2017年 | 215篇 |
2016年 | 424篇 |
2015年 | 367篇 |
2014年 | 320篇 |
2013年 | 485篇 |
2012年 | 344篇 |
2011年 | 482篇 |
2010年 | 302篇 |
2009年 | 447篇 |
2008年 | 455篇 |
2007年 | 504篇 |
2006年 | 456篇 |
2005年 | 474篇 |
2004年 | 446篇 |
2003年 | 430篇 |
2002年 | 337篇 |
2001年 | 216篇 |
2000年 | 234篇 |
1999年 | 185篇 |
1998年 | 236篇 |
1997年 | 166篇 |
1996年 | 122篇 |
1995年 | 158篇 |
1994年 | 121篇 |
1993年 | 106篇 |
1992年 | 73篇 |
1991年 | 58篇 |
1990年 | 42篇 |
1989年 | 60篇 |
1988年 | 49篇 |
1987年 | 38篇 |
1986年 | 37篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1973年 | 10篇 |
1972年 | 8篇 |
1971年 | 14篇 |
排序方式: 共有9441条查询结果,搜索用时 328 毫秒
41.
The steady-state two-phase flow non-linear equation is considered in the case when one of phases has low effective permeability in some periodic set, while on the complementary set it is high; the second phase has no contrast of permeabilities in different zones. A homogenization procedure gives the homogenized model with macroscopic effective permeability of the second phase depending on the gradient and on the second order derivatives of the macroscopic pressure of the first phase. This effect cannot be obtained by classical (one small parameter) homogenization. To cite this article: G.P. Panasenko, G. Virnovsky, C. R. Mecanique 331 (2003). 相似文献
42.
在利用Harris两参数公式研究Bohr-Mottelson转动谱公式参数之间的关系的基础上,改用Harris三参数公式,并由此提出了Bohr-Mottelson转动谱公式参数之间的新关系式,进而用I(I+1)四参数展开式计算了A~60,80,130,140,150,190区超形变偶偶核的基带和锕系和稀土区正常形变核基带,讨论了参数之间的关系,发现新关系式与实验较好地符合. 相似文献
43.
A. Vukics H. Ritsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):585-599
We present a framework for efficiently performing Monte Carlo
wave-function simulations in cavity QED with moving particles. It
relies heavily on the object-oriented programming paradigm as realised
in C++, and is extensible and applicable for simulating open
interacting qua
ntum dynamics in general. The user is provided with a
number of “elements”, e.g. pumped moving particles, pumped lossy
cavity modes, and various interactions to compose complex interacting
systems, which contain several particles moving in electromagnetic
fields of various configurations, and perform wave-function
simulations on such systems. A number of tools are provided to
facilitate the implementation of new elements. 相似文献
44.
Thiw work is concerned with the formulation of constituent interactions and corresponding balance relations in classical mixture theory as based on a model for the (classical) constituent structure of such a mixture. 相似文献
45.
Protein Conformation of a Lattice Model Using Tabu Search 总被引:1,自引:0,他引:1
We apply tabu search techniques to the problem of determining the optimal configuration of a chain of protein sequences on a cubic lattice. The problem under study is difficult to solve because of the large number of possible conformations and enormous amount of computations required. Tabu search is an iterative heuristic procedure which has been shown to be a remarkably effective method for solving combinatorial optimization problems. In this paper, an algorithm is designed for the cubic lattice model using tabu search. The algorithm has been tested on a chain of 27 monomers. Computational results show that our method outperforms previously reported approaches for the same model. 相似文献
46.
J. Schulte 《Journal of statistical physics》1993,70(5-6):1343-1347
The thermodynamic stability of4He4–13 at 3.2 K is investigated with the classical Monte Carlo method, with the semiclassical path-integral Monte Carlo (PIMC) method, and with the semiclassical all-order many-body method. In the all-order many-body simulation the dipole-dipole approximation including short-range correction is used. The resulting stability plots are discussed and related to recent TOF experiments by Stephens and King. It is found that with classical Monte Carlo of course the characteristics of the measured mass spectrum cannot be resolved. With PIMC, switching on more and more quantum mechanics. by raising the number of virtual time steps results in more structure in the stability plot, but this did not lead to sufficient agreement with the TOF experiment. Only the all-order many-body method resolved the characteristic structures of the measured mass spectrum, including magic numbers. The result shows the influence of quantum statistics and quantum mechanics on the stability of small neutral helium clusters. 相似文献
47.
Heat transfer in lattice BGK modeled fluid 总被引:1,自引:0,他引:1
The thermal lattice BGK model is a recently suggested numerical tool aiming at solving problems of thermohydrodynamics. The quality of the lattice BGK simulation is checked in this paper by calculating temperature profiles in the Couette flow under different Eckert and Mach numbers. A revised lower order model is proposed to improve the accuracy and the higher order model is proved to be advantageous in this respect, especially in the flow regime with a higher Mach number. 相似文献
48.
T. Charitat B. Fourcade 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):333-336
An o-ring takes spontaneously the shape of a chair when strong enough torsion is applied in its tangent plane. This state
is metastable, since work has to be done on the o-ring to return to the circular shape. We show that this metastable state
exists in a Hamiltonian where curvature and torsion are coupled via an intrinsic curvature term. If the o-ring is constrained to be planar (2d case), this metastable state displays a kink-anti-kink
pair. This state is metastable if the ratio is less than , where C and A are the torsion and the bending elastic constants [#!landau!#]. In three dimensions, our variational approach shows that
. This model can be generalized to the case where the bend is induced by a concentration field which follows the variations
of the curvature.
Received: 27 August 1997 / Revised: 23 October 1997 / Accepted: 12 November 1997 相似文献
49.
Marco Marletta 《Advances in Computational Mathematics》1994,2(2):155-184
This paper discusses the numerical solution of eigenvalue problems for Hamiltonian systems of ordinary differential equations.
Two new codes are presented which incorporate the algorithms described here; to the best of the author’s knowledge, these
are the first codes capable of solving numerically such general eigenvalue problems. One of these implements a new new method
of solving a differential equation whose solution is a unitary matrix. Both codes are fully documented and are written inPfort-verifiedFortran 77, and will be available in netlib/aicm/sl11f and netlib/aicm/sl12f. 相似文献
50.
Some properties of the bilevel programming problem 总被引:8,自引:0,他引:8
J. F. Bard 《Journal of Optimization Theory and Applications》1991,68(2):371-378
The purpose of this paper is to elaborate on the difficulties accompanying the development of efficient algorithms for solving the bilevel programming problem (BLPP). We begin with a pair of examples showing that, even under the best of circumstances, solutions may not exist. This is followed by a proof that the BLPP is NP-hard.This work was partially supported by a grant from the Advanced Research Program of the Texas Higher Education Coordinating Board. 相似文献