全文获取类型
收费全文 | 2207篇 |
免费 | 72篇 |
国内免费 | 17篇 |
专业分类
化学 | 1374篇 |
晶体学 | 20篇 |
力学 | 60篇 |
数学 | 340篇 |
物理学 | 502篇 |
出版年
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 31篇 |
2020年 | 31篇 |
2019年 | 32篇 |
2018年 | 33篇 |
2017年 | 21篇 |
2016年 | 61篇 |
2015年 | 68篇 |
2014年 | 61篇 |
2013年 | 108篇 |
2012年 | 149篇 |
2011年 | 149篇 |
2010年 | 93篇 |
2009年 | 70篇 |
2008年 | 101篇 |
2007年 | 121篇 |
2006年 | 107篇 |
2005年 | 77篇 |
2004年 | 69篇 |
2003年 | 58篇 |
2002年 | 57篇 |
2001年 | 25篇 |
2000年 | 35篇 |
1999年 | 21篇 |
1998年 | 17篇 |
1997年 | 28篇 |
1996年 | 30篇 |
1995年 | 20篇 |
1994年 | 28篇 |
1993年 | 30篇 |
1992年 | 31篇 |
1991年 | 16篇 |
1990年 | 26篇 |
1989年 | 20篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1985年 | 16篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 24篇 |
1981年 | 17篇 |
1980年 | 20篇 |
1979年 | 21篇 |
1978年 | 13篇 |
1977年 | 23篇 |
1976年 | 15篇 |
1975年 | 18篇 |
1974年 | 18篇 |
1973年 | 20篇 |
排序方式: 共有2296条查询结果,搜索用时 171 毫秒
1.
2.
BIT Numerical Mathematics - In this article we address the problem of minimizing a strictly convex quadratic function using a novel iterative method. The new algorithm is based on the well-known... 相似文献
3.
A set of exact conditions is compiled for the purpose of developing and testing approximations for the exchange-correlation energy as a functional of the electron density. Special emphasis is placed upon recently developed density-scaling relationships. Commonly used generalized gradient approximations are compared against several of these conditions. A direct tabular comparison of these functionals (not of calculated properties) with one another is also made. © 1994 John Wiley & Sons, Inc. 相似文献
4.
5.
Jayanth R. Banavar Oscar Gonzalez John H. Maddocks Amos Maritan 《Journal of statistical physics》2003,110(1-2):35-50
Physical strands or sheets that can be modelled as curves or surfaces embedded in three dimensions are ubiquitous in nature, and are of fundamental importance in mathematics, physics, biology, and engineering. Often the physical interpretation dictates that self-avoidance should be enforced in the continuum model, i.e., finite energy configurations should not self-intersect. Current continuum models with self-avoidance frequently employ pairwise repulsive potentials, which are of necessity singular. Moreover the potentials do not have an intrinsic length scale appropriate for modelling the finite thickness of the physical systems. Here we develop a framework for modelling self-avoiding strands and sheets which avoids singularities, and which provides a way to introduce a thickness length scale. In our approach pairwise interaction potentials are replaced by many-body potentials involving three or more points, and the radii of certain associated circles or spheres. Self-interaction energies based on these many-body potentials can be used to describe the statistical mechanics of self-interacting strands and sheets of finite thickness. 相似文献
6.
We study the expected delay in cyclic polling models with general ‘branching-type’ service disciplines. For this class of
models, which contains models with exhaustive and gated service as special cases, we obtain closed-form expressions for the
expected delay under standard heavy-traffic scalings. We identify a single parameter associated with the service discipline
at each queue, which we call the ‘exhaustiveness’. We show that the scaled expected delay figures depend on the service policies
at the queues only through the exhaustiveness of each of the service disciplines. This implies that the influence of different
service disciplines, but with the same exhaustiveness, on the expected delays at the queues becomes the same when the system
reaches saturation. This observation leads to a new classification of the service disciplines. In addition, we show monotonicity
of the scaled expected delays with respect to the exhaustiveness of the service disciplines. This induces a complete ordering
in terms of efficiency of the service disciplines. The results also lead to new rules for optimization of the system performance
with respect to the service disciplines at the queues. Further, the exact asymptotic results suggest simple expected waiting-time
approximations for polling models in heavy traffic. Numerical experiments show that the accuracy of the approximations is
excellent for practical heavy-traffic scenarios.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
Let G be a finite group. A complete Sylow product of G is a product of Sylow subgroups of G, one for each prime divisor of |G|. We shall call G a Sylow factorizable group if it is equal to at least one of its complete Sylow products. We prove that if G is a Sylow factorizable group then the
intersection of all complete Sylow products of G is equal to the solvable radical of G. We generalize the concepts and the result to Sylow products which involve an arbitrary subset of the prime divisors of |G|.
Received: 26 January 2005 相似文献
8.
Models, describing relativistic particles, where Lagrangian densities depend linearly on both the curvature and the torsion of the trajectories, are revisited in D=3 space forms. The moduli spaces of trajectories are completely and explicitly determined using the Lancret program. The moduli subspaces of closed solitons in the three sphere are also determined. 相似文献
9.
Adam B. Levy 《Mathematical Programming》2007,110(3):615-639
Numerical methods for solving constrained optimization problems need to incorporate the constraints in a manner that satisfies
essentially competing interests; the incorporation needs to be simple enough that the solution method is tractable, yet complex
enough to ensure the validity of the ultimate solution. We introduce a framework for constraint incorporation that identifies
a minimal acceptable level of complexity and defines two basic types of constraint incorporation which (with combinations)
cover nearly all popular numerical methods for constrained optimization, including trust region methods, penalty methods,
barrier methods, penalty-multiplier methods, and sequential quadratic programming methods. The broad application of our framework
relies on addition and chain rules for constraint incorporation which we develop here. 相似文献
10.