全文获取类型
收费全文 | 1484篇 |
免费 | 86篇 |
国内免费 | 32篇 |
专业分类
化学 | 66篇 |
晶体学 | 1篇 |
力学 | 137篇 |
综合类 | 11篇 |
数学 | 1229篇 |
物理学 | 158篇 |
出版年
2023年 | 16篇 |
2022年 | 16篇 |
2021年 | 24篇 |
2020年 | 23篇 |
2019年 | 23篇 |
2018年 | 21篇 |
2017年 | 31篇 |
2016年 | 30篇 |
2015年 | 36篇 |
2014年 | 62篇 |
2013年 | 99篇 |
2012年 | 82篇 |
2011年 | 51篇 |
2010年 | 50篇 |
2009年 | 76篇 |
2008年 | 83篇 |
2007年 | 98篇 |
2006年 | 87篇 |
2005年 | 58篇 |
2004年 | 57篇 |
2003年 | 52篇 |
2002年 | 52篇 |
2001年 | 46篇 |
2000年 | 34篇 |
1999年 | 47篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 25篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1973年 | 1篇 |
排序方式: 共有1602条查询结果,搜索用时 15 毫秒
181.
In this paper we shall address this problem: Is quantum gravity constraints algebra closed and what are the quantum Einstein’s
equations. We shall investigate this problem in the de-Broglie-Bohm quantum theory framework. It is shown that the constraint
algebra is weakly closed and the quantum Einstein’s equations are derived. 相似文献
182.
This paper considers the number of inner iterations required per outeriteration for the algorithm proposed by Conn et al.[9]. We show that asymptotically, under suitable reasonable assumptions, a single inner iteration suffices. 相似文献
183.
M. Gerdts 《Journal of Optimization Theory and Applications》2006,130(2):231-251
Necessary conditions are derived for optimal control problems subject to index-2 differential-algebraic equations, pure state constraints, and mixed control-state constraints. Differential-algebraic equations are composite systems of differential equations and algebraic equations, which arise frequently in practical applications. The structure of the optimal control problem under consideration is exploited and special emphasis is laid on the representation of the Lagrange multipliers resulting from the necessary conditions for infinite optimization problems.The author thanks the referees for careful reading and helpful suggestions and comments. 相似文献
184.
A. Shapiro 《Journal of Optimization Theory and Applications》2006,128(1):221-243
In this paper, we discuss here-and-now type stochastic programs with equilibrium constraints. We give a general formulation
of such problems and study their basic properties such as measurability and continuity of the corresponding integrand functions.
We discuss also the consistency and rate of convergence of sample average approximations of such stochastic problems 相似文献
185.
This paper deals with a production plant in which two different products can be produced. The plant consists of three subsystemsS
i
. Before or after a phase of separate processing in subsystemsS
1 andS
2, the two products have to be processed in subsystemS
3. Each of these subsystems has a limited capacity.In the first part, we assume empty stocks at the beginning; at a fixed timeT in the future, certain quantitiesX
i of the two products have to be delivered to the customers. Facing linear holding costs, convex production costs, and stringent capacity constraints, the problem is to decide when to produce which product at what rate.It is shown that the optimal solution consists of up to six different regimes and that the time paths of the production rates need not be monotonic. These results, which can be obtained analytically, are also illustrated in several numerical examples.Finally, the case is considered where the terminal demand at timeT is replaced by a continuous and seasonally fluctuating demand rate. It is demonstrated that the optimal production rates show an interesting and nontrivial behavior. In particular, it may happen that, on intervals where the demand for the one product increases, the optimal production rate decreases. This is also demonstrated by computer plots in some numerical examples.The first author gratefully acknowledges support from the Austrian Science Foundation under Grant S3204 and the second author from Stiftung Volkswagenwerk. An earlier version of this paper was presented at the DGOR-NSOR Joint Conference, Eindhoven, Holland, September 23–25, 1987. 相似文献
186.
We present an introductory review of recent work on the control of open queueing networks. We assume that customers of different types arrive at a network and pass through the system via one of several possible routes; the set of routes available to a customer depends on its type. A route through the network is an ordered set of service stations: a customer queues for service at each station on its route and then leaves the system. The two methods of control we consider are the routing of customers through the network, and the sequencing of service at the stations, and our aim is to minimize the number of customers in the system. We concentrate especially on the insights which can be obtained from heavy traffic analysis, and in particular from Harrison's Brownian network models. Our main conclusion is that in many respects dynamic routingsimplifies the behaviour of networks, and that under good control policies it may well be possible to model the aggregate behaviour of a network quite straightforwardly.Supported by SERC grant GR/F 94194. 相似文献
187.
We present theory and algorithms for the equality constrained indefinite least squares problem, which requires minimization of an indefinite quadratic form subject to a linear equality constraint. A generalized hyperbolic QR factorization is introduced and used in the derivation of perturbation bounds and to construct a numerical method. An alternative method is obtained by employing a generalized QR factorization in combination with a Cholesky factorization. Rounding error analysis is given to show that both methods have satisfactory numerical stability properties and numerical experiments are given for illustration. This work builds on recent work on the unconstrained indefinite least squares problem by Chandrasekaran, Gu, and Sayed and by the present authors. 相似文献
188.
Jane J. Ye 《Journal of Mathematical Analysis and Applications》2005,307(1):350-369
In this paper we consider a mathematical program with equilibrium constraints (MPEC) formulated as a mathematical program with complementarity constraints. Various stationary conditions for MPECs exist in literature due to different reformulations. We give a simple proof to the M-stationary condition and show that it is sufficient for global or local optimality under some MPEC generalized convexity assumptions. Moreover, we propose new constraint qualifications for M-stationary conditions to hold. These new constraint qualifications include piecewise MFCQ, piecewise Slater condition, MPEC weak reverse convex constraint qualification, MPEC Arrow-Hurwicz-Uzawa constraint qualification, MPEC Zangwill constraint qualification, MPEC Kuhn-Tucker constraint qualification, and MPEC Abadie constraint qualification. 相似文献
189.
Oleg P. Burdakov José Mario Martínez Elvio A. Pilotta 《Annals of Operations Research》2002,117(1-4):51-70
A new algorithm for solving smooth large-scale minimization problems with bound constraints is introduced. The way of dealing with active constraints is similar to the one used in some recently introduced quadratic solvers. A limited-memory multipoint symmetric secant method for approximating the Hessian is presented. Positive-definiteness of the Hessian approximation is not enforced. A combination of trust-region and conjugate-gradient approaches is used to explore useful information. Global convergence is proved for a general model algorithm. Results of numerical experiments are presented. 相似文献
190.
Y. Y. Fan R. E. Kalaba H. H. Natsuyama F. E. Udwadia 《Journal of Optimization Theory and Applications》2005,127(3):475-484
The Gauss principle of least constraint is derived from a new point of view. Then, an extended principle of least constraint
is derived to cover the case of nonideal constraints. Finally, a version of the principle for general underdetermined systems
is adumbrated. Throughout, the notion of generalized inverses of matices plays a prominent role. 相似文献