全文获取类型
收费全文 | 316948篇 |
免费 | 2730篇 |
国内免费 | 1243篇 |
专业分类
化学 | 152827篇 |
晶体学 | 4393篇 |
力学 | 16381篇 |
综合类 | 2篇 |
数学 | 57919篇 |
物理学 | 89399篇 |
出版年
2020年 | 1770篇 |
2019年 | 2036篇 |
2018年 | 12535篇 |
2017年 | 12303篇 |
2016年 | 9699篇 |
2015年 | 3391篇 |
2014年 | 4150篇 |
2013年 | 11400篇 |
2012年 | 11634篇 |
2011年 | 19997篇 |
2010年 | 11921篇 |
2009年 | 12252篇 |
2008年 | 15259篇 |
2007年 | 17433篇 |
2006年 | 8543篇 |
2005年 | 9026篇 |
2004年 | 8409篇 |
2003年 | 8062篇 |
2002年 | 7078篇 |
2001年 | 7411篇 |
2000年 | 5601篇 |
1999年 | 4331篇 |
1998年 | 3699篇 |
1997年 | 3687篇 |
1996年 | 3469篇 |
1995年 | 3240篇 |
1994年 | 3016篇 |
1993年 | 3085篇 |
1992年 | 3344篇 |
1991年 | 3389篇 |
1990年 | 3190篇 |
1989年 | 3155篇 |
1988年 | 3217篇 |
1987年 | 3084篇 |
1986年 | 2980篇 |
1985年 | 4031篇 |
1984年 | 4184篇 |
1983年 | 3435篇 |
1982年 | 3789篇 |
1981年 | 3683篇 |
1980年 | 3562篇 |
1979年 | 3596篇 |
1978年 | 3810篇 |
1977年 | 3624篇 |
1976年 | 3829篇 |
1975年 | 3403篇 |
1974年 | 3527篇 |
1973年 | 3841篇 |
1972年 | 2344篇 |
1971年 | 1793篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
R. Tijdeman 《Indagationes Mathematicae》2003,14(1):135-147
Let w = w1 … wn be a word of maximal length n, and with a maximal number of distinct letters for this length, such that w has periods p1, …, pn but not period gcd(p1,…,pr). We provide a fast algorithm to compute n and w. We show that w is uniquely determined apart from isomorphism and that it is a palindrome. Furthermore we give lower and upper bounds for n as explicit functions of p1, …pr. For r = 2 the exact value of n is due to Fine and Wilf. In case the number of distinct letters in the extremal word equals r a formula for n had been given by Castelli, Mignosi and Restivo in case r = 3 and by Justin if r > 3. 相似文献
992.
J. F. R. Archilla J. Cuevas B. Snchez-Rey A. Alvarez 《Physica D: Nonlinear Phenomena》2003,180(3-4):235-255
Whereas there exists a mathematical proof for one-site breathers stability, and an unpublished one for two-site breathers, the methods for determining the stability properties of multibreathers rely on numerical computation of the Floquet multipliers or on the weak nonlinearity approximation leading to discrete nonlinear Schrödinger equations. Here we present a set of multibreather stability theorems (MST) that provides a simple method to determine multibreathers stability in Klein–Gordon systems. These theorems are based in the application of degenerate perturbation theory to Aubry’s band theory. We illustrate them with several examples. 相似文献
993.
Dynamics of Multisection Semiconductor Lasers 总被引:1,自引:0,他引:1
We consider a mathematical model (the so-called traveling-wave system) which describes longitudinal dynamical effects in semiconductor lasers. This model consists of a linear hyperbolic system of PDEs, which is nonlinearly coupled with a slow subsystem of ODEs. We prove that a corresponding initial-boundary value problem is well posed and that it generates a smooth infinite-dimensional dynamical system. Exploiting the particular slow-fast structure, we derive conditions under which there exists a low-dimensional attracting invariant manifold. The flow on this invariant manifold is described by a system of ODEs. Mode approximations of that system are studied by means of bifurcation theory and numerical tools. 相似文献
994.
Our main object in this paper is to discuss some results on rings with left identity in which certain subsets satisfy some functional identities. 相似文献
995.
This paper studies a supply chain consisting of two suppliers and one retailer in a spot market, where the retailer uses the
newsvendor solution as its purchase policy, and suppliers compete for the retailer’s purchase. Since each supplier’s bidding
strategy affects the other’s profit, a game theory approach is used to identify optimal bidding strategies. We prove the existence
and uniqueness of a Nash solution. It is also shown that the competition between the supplier leads to a lower market clearing
price, and as a result, the retailer benefits from it. Finally, we demonstrate the applicability of the obtained results by
deriving optimal bidding strategies for power generator plants in the deregulated California energy market.
Supported in part by RGC (Hong Kong) Competitive Earmarked Research Grants (CUHK4167/04E and CUHK4239/03E), a Distinguished
Young Investigator Grant from the National Natural Sciences Foundation of China, and a grant from Hundred Talents Program
of the Chinese Academy of Sciences. 相似文献
996.
Currently, most combinatorial optimisation problems have to be solved, if the optimum solution is sought, using general techniques
to explore the space of feasible solutions and, more specifically, through exploratory enumerative procedures in trees and
search graphs. We propose Branch and Win, a general formulation for understanding and synthesising the different tree search
procedures that have been presented in the literature of operations research as well as in that of artificial intelligence.
Several general ideas are also presented, whose application allows designing new hybrid search algorithms, in order to implement
the procedure. 相似文献
997.
Arne Schirrmacher 《Physics in Perspective (PIP)》2003,5(1):4-20
David Hilbert (1862-1943) played an important role in establishing quantum physics in Göttingen. I analyze the ways in which his influence was decisive by comparison with Woldemar Voigt (1850-1919). Voigt was the leading Göttingen theoretical physicist before the arrival of Peter Debye (1884-1966), who was appointed to a new professorship in 1914 at Hilbert's instigation. I portray the Göttingen mathematicians, above all Hermann Minkowski (1864-1909) and David Hilbert, as planting the seeds for the blossoming of quantum physics under their student Max Born (1882-1970) in the 1920s. 相似文献
998.
Wolfgang Staubach 《Journal d'Analyse Mathématique》2003,91(1):389-400
In this paper, we present an explicit calculation of the heat kernel, fundamental solution and Schwartz kernel of the resolvent
for the Heisenberg Laplacian using Wiener path integrals and their realizations via the Trotter product formula. This also
gives another derivation of mehler’s formula. 相似文献
999.
V. Klepko S. Ryabov Yu. Kercha L. Bulavin R. Bila V. Slisenko O. Vasilkevich V. Krotenko 《Journal of Molecular Liquids》2005,120(1-3):67-69
Water molecule mobility in ion-containing and nonionic aqueous solutions of β-cyclodextrin was studied by quasielastic neutron scattering (QENS). The total self-diffusion coefficients and their components corresponding to the contributions from collective (Lagrange type) and single-particle (jump diffusion) parts of molecular motions were determined. From the data obtained, one can conclude that the molecular mobility of free water in nonionic aqueous solutions of β-cyclodextrin with guest molecules (2-aminopyridine) proceeds by a single-particle mechanism. The addition of Pb2+ ions into the solution leads to increase in self-diffusion coefficients and growth of a bound water fraction. 相似文献
1000.
A set of invariants describing the limit regimes of braking disk-type wound composite flywheels is suggested. The limit regime is determined by using a linear failure criterion. It is shown that, for generating short-time impulses of very high power, a set of small identical flywheels is more effective than one large flywheel with an equivalent mass. Particular examples illustrating the theory considered are discussed. 相似文献