全文获取类型
收费全文 | 874篇 |
免费 | 9篇 |
国内免费 | 9篇 |
专业分类
化学 | 424篇 |
晶体学 | 7篇 |
力学 | 25篇 |
数学 | 115篇 |
物理学 | 321篇 |
出版年
2020年 | 12篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2014年 | 10篇 |
2013年 | 43篇 |
2012年 | 40篇 |
2011年 | 32篇 |
2010年 | 21篇 |
2009年 | 19篇 |
2008年 | 19篇 |
2007年 | 37篇 |
2006年 | 21篇 |
2005年 | 18篇 |
2004年 | 21篇 |
2003年 | 13篇 |
2002年 | 21篇 |
2001年 | 13篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 15篇 |
1994年 | 21篇 |
1993年 | 24篇 |
1992年 | 25篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 18篇 |
1976年 | 14篇 |
1975年 | 16篇 |
1974年 | 14篇 |
1973年 | 19篇 |
1972年 | 7篇 |
1971年 | 7篇 |
1969年 | 8篇 |
1968年 | 6篇 |
排序方式: 共有892条查询结果,搜索用时 46 毫秒
1.
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
2.
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
3.
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
4.
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
5.
6.
Alick KT Law Deepak Gupta Shawn Levy Douglas C Wallace Robert J McKeon Charles R Buck 《BMC neuroscience》2004,5(1):1
Background
The adenine nucleotide translocator 1 (Ant1) is an inner mitochondrial membrane protein involved with energy mobilization during oxidative phosphorylation. We recently showed that rodent Ant1 is upregulated by transforming growth factor-beta (TGF-β) in reactive astrocytes following CNS injury. In the present study, we describe the molecular mechanisms by which TGF-β1 regulates Ant1 gene expression in cultured primary rodent astrocytes. 相似文献7.
Brick DH Widgoff M Beilliere P Lutz P Narjoux JL Gelfand N Alyea ED Bloomer M Bober J Busza W Cole B Frank TA Fuess TA Grodzins L Hafen ES Haridas P Huang D Huang HZ Hulsizer R Kistiakowsky V Ledoux RJ Milstene C Noguchi S Oh SH Pless IA Steadman S Stoughton TB Suchorebrow V Tether S Trepagnier PC Wadsworth BF Wu Y Yamamoto RK Cohn HO Calligarich E Castoldi C Dolfini R Introzzi G Ratti S Badiak M DiMarco R Jacques PF Kalelkar M Plano RJ Stamer PE Brucker EB Koller EL Alexander G Grunhaus J 《Physical review D: Particles and fields》1990,41(3):765-773
8.
General Information
Preparation of papers 相似文献9.
10.
The influence of poly(vinyl alcohol) (PVA), a steric stabilizer, and sodium dodecyl sulfate (SDS), an electrostatic stabilizer, on the stability of styrene dispersion polymerized systems was studied. It was shown that in stabilization by PVA there was pronounced bridging of the submicron emulsion particles to 10-μ dispersion particles and that the emulsion particles could not be washed off. In SDS stabilization, on the other hand, the emulsion formed was easily washed off because bridging with SDS does not occur. The surface tension of the aqueous phase measured during polymerization showed different characteristics for stable and unstable systems. 相似文献