全文获取类型
收费全文 | 130587篇 |
免费 | 377篇 |
国内免费 | 352篇 |
专业分类
化学 | 49513篇 |
晶体学 | 1759篇 |
力学 | 9050篇 |
综合类 | 17篇 |
数学 | 28955篇 |
物理学 | 42022篇 |
出版年
2019年 | 403篇 |
2018年 | 9977篇 |
2017年 | 10901篇 |
2016年 | 4996篇 |
2015年 | 1249篇 |
2014年 | 664篇 |
2013年 | 955篇 |
2012年 | 5396篇 |
2011年 | 14329篇 |
2010年 | 8426篇 |
2009年 | 8566篇 |
2008年 | 12232篇 |
2007年 | 16125篇 |
2006年 | 819篇 |
2005年 | 7846篇 |
2004年 | 4218篇 |
2003年 | 4265篇 |
2002年 | 2172篇 |
2001年 | 731篇 |
2000年 | 761篇 |
1999年 | 362篇 |
1996年 | 461篇 |
1995年 | 407篇 |
1994年 | 384篇 |
1993年 | 400篇 |
1992年 | 371篇 |
1991年 | 409篇 |
1990年 | 426篇 |
1989年 | 421篇 |
1988年 | 365篇 |
1987年 | 404篇 |
1986年 | 371篇 |
1985年 | 456篇 |
1984年 | 509篇 |
1983年 | 430篇 |
1982年 | 456篇 |
1981年 | 407篇 |
1980年 | 419篇 |
1979年 | 521篇 |
1978年 | 549篇 |
1977年 | 455篇 |
1976年 | 578篇 |
1975年 | 501篇 |
1974年 | 501篇 |
1973年 | 572篇 |
1972年 | 470篇 |
1971年 | 404篇 |
1970年 | 415篇 |
1969年 | 405篇 |
1968年 | 379篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We prove an existence theorem and establish the property of stochastic stability for processes determined by the Poisson stochastic differential equations with delay. 相似文献
992.
H. Leutwyler 《Czechoslovak Journal of Physics》2002,52(2):B9-B27
The lectures review some of the basic concepts relevant for an understanding of the low energy properties of the strong interactions: chiral symmetry, spontaneous symmetry breakdown, Goldstone bosons, quark condensate. The effective field theory used to analyze the low energy structure is briefly sketched. As an illustration, I discuss the implications of the recent data on the decay K→ππeν for the magnitude of the quark condensate. 相似文献
993.
Risk analysis tools have been used to help manage various projects. This paper describes a case study in which an extension to the stochastic project network model was developed for a risk analysis of an oil platform installation, quantifying the possible impact of the weather on the project's schedule. Examination of the weather data suggested the use of a Markov weather model combined with a separate residence time distribution for key states. The weather model was incorporated into the stochastic project network allowing the interactions of the various project uncertainties to be examined. While the weather introduced a significant additional risk to the project, analysis of management's options indicated that much of the risk might be avoided. In particular, the analysis quantified the benefits of scheduling the project start to take advantage of the seasonal variations and hiring heavy duty equipment to operate in more arduous conditions. 相似文献
994.
E. V. Zakharov S. N. Levchenko Yu. Ya. Kharlanov 《Computational Mathematics and Modeling》1997,8(3):282-287
The article considers the mathematical model of a lens antenna in the shape of a homogeneous dielectric torus excited by an
axial magnetic dipole. The boundary-value problem for an elliptical differential equation is posed and reduced by the fundamental
solution method to an integral equation of 2nd kind over the torus section. A numerical algorithm is proposed, and the numerical
results are compared with experimental findings.
Translated from Obratnye Zadachi Estestvoznaniya, Published by Moscow University, Moscow, 1997, pp. 109–115. 相似文献
995.
R. P. Sundarraj P. S. Sundararaghavan Dale R. Fox 《The Journal of the Operational Research Society》1994,45(5):549-558
Several production and flexible manufacturing systems can naturally be modelled using queueing networks. In this paper, we consider the problem of acquiring servers for the nodes of an open queueing network, so as to optimize the steady-state mean virtual system parameters subject to a budget constraint. A partial enumeration scheme and a heuristic method have been proposed to solve this problem. Empirical results based on randomly generated test problems are used to identify a class of problems for which the heuristic performs well. 相似文献
996.
Summary. The reconstruction index of all semiregular permutation groups is determined. We show that this index satisfies 3 £ r(G, W) £ 5 3 \leq \rho(G, \Omega) \leq 5 and we classify the groups in each case. 相似文献
997.
Lorraine R. Gardiner Ralph E. Steuer 《The Journal of the Operational Research Society》1994,45(12):1456-1466
It has previously been shown that nine of the most prominent procedures of interactive multiple objective programming can be considered as special cases of a common procedure called the unified algorithm. In this paper, we show how four additional procedures can be similarly included in the unified approach. Also, the paper presents a procedure-switching matrix that depicts the possibilities for switching from one procedure to another, one iteration to the next, in the unified algorithm if so directed by a user. 相似文献
998.
We show that if a polynomial filled Julia set has empty interior, then it is computable. 相似文献
999.
Given an integer n ≥ 2, let λ(n) := (log n)/(log γ(n)), where γ(n) = Π
p|n p, stand for the index of composition of n, with λ(1) = 1. We study the distribution function of (λ(n) – 1) log n as n runs through particular sets of integers, such as the shifted primes, the values of a given irreducible cubic polynomial
and the shifted powerful numbers.
Research supported in part by a grant from NSERC.
Research supported by the Applied Number Theory Research Group of the Hungarian Academy of Science and by a grant from OTKA.
Professor M.V. Subbarao passed away on February 15, 2006.
Received: 3 March 2006 Revised: 28 October 2006 相似文献
1000.
A. Kavokin 《Applied Physics A: Materials Science & Processing》2007,89(2):241-246
An overview is given of the current research trends in the physics of exciton-polaritons in microcavities. Potential applications
of the Bose–Einstein condensation and superfluidity of exciton-polaritons are discussed. The perspectives for the realization
of polariton lasers, polariton spin transistors and polarization modulators are presented.
PACS 78.67.-n; 71.36.+c; 42.55.Sa; 42.25.Kb 相似文献