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221.
The general mean-semivariance portfolio optimization problem seeks to determine the efficient frontier by solving a parametric non-quadratic programming problem. In this paper it is shown how to transform this problem into a general mean-variance optimization problem, hence the Critical Line Algorithm is applicable. This paper also discusses how to implement the critical line algorithm to save storage and reduce execution time. 相似文献
222.
利用完备格L上的无限分配t-模T,研究了T-型矩阵方程A TX TB=C的解,得到该方程有解的一个等价条件。同时,在有解时给出求该方程整个解集的一个算法。 相似文献
223.
Let G be an affine algebraic group acting on an affine variety X. We present an algorithm for computing generators of the invariant ring KG[X] in the case where G is reductive. Furthermore, we address the case where G is connected and unipotent, so the invariant ring need not be finitely generated. For this case, we develop an algorithm which computes KG[X] in terms of a so-called colon-operation. From this, generators of KG[X] can be obtained in finite time if it is finitely generated. Under the additional hypothesis that K[X] is factorial, we present an algorithm that finds a quasi-affine variety whose coordinate ring is KG[X]. Along the way, we develop some techniques for dealing with nonfinitely generated algebras. In particular, we introduce the finite generation ideal. 相似文献
224.
The positron emission particle tracking (PEPT) technique has been widely used in science and engineering to obtain detailed information on the motion and flow fields of fluids or granular materials in multiphase systems, for example, fluids in rock cracks, chemical reactors and food processors; dynamic behaviour of granular materials in chemical reactors, granulators, mixers, dryers, rotating kilns and ball mills. The information obtained by the PEPT technique can be used to optimise the design, operational conditions for a wide range of industrial process systems, and to evaluate modelling work. The technique is based on tracking radioactively labelled particles (up to three particles) by detecting the pairs of back-to-back 511 ke V -γ-rays arising from annihilation of emitted positrons. It therefore involves a positron camera, location algorithms for calculating the tracer location and speed, and tracer labelling techniques. This paper will review the particle tracking technique from tracking algorithm, tracer labelling to their application. 相似文献
225.
Madjid Allili Tomasz Kaczynski 《Transactions of the American Mathematical Society》2000,352(5):2261-2281
This paper is devoted to giving the theoretical background for an algorithm for computing homomorphisms induced by maps in homology. The principal idea is to insert the graph of a given continuous map into a graph of a multi-valued representable map . The multi-valued representable maps have well developed continuity properties and admit a finite coding that permits treating them by combinatorial methods. We provide the construction of the homomorphism induced by such that . The presented construction does not require subsequent barycentric subdivisions and simplicial approximations of . The main motivation for this paper comes from the project of computing the Conley Index for discrete dynamical systems.
226.
A revised version of Dodge's split-velocity method for numerical calculation of compressible duct flow has been developed. The revision incorporates balancing of mass flow rates on each marching step in order to maintain front-to-back continuity during the calculation. The (chequerboard) zebra algorithm is applied to solution of the three-dimensional continuity equation in conservative form. A second-order A-stable linear multistep method is employed in effecting a marching solution of the parabolized momentum equations. A chequerboard iteration is ued to solve the resulting implicit non-linear systems of finite-difference equations which govern stepwise transition. Qualitive agreement with analytical predictions and experimental results has been obtained for some flows with well-known solutions. 相似文献
227.
We present an efficient simplicial algorithm for computing a zero of a point-to-set mapping that is formed by piecing together
smooth functions. Such mappings arise in nonlinear programming and economic equilibrium problems. Our algorithm, under suitable
regularity conditions on the problem, generates a sequence converging at least Q-superlinearly to a zero of the mapping. Asymptotically,
it operates in a space of reduced dimension, analogous to an active set strategy in the optimization setting, but it switches
active sets automatically. Results of computational experiments are given.
Research of this author was supported by a Fellowship from the Rockeffeller Foundation.
Research of this author was partially supported by a fellowhip from the John Simon Guggenheim Memorial Foundation and by National
Science Foundation Grant ECS-7921279. 相似文献
228.
Dimitri P. Bertsekas 《Mathematical Programming》1983,27(1):107-120
We present an algorithmic model for distributed computation of fixed points whereby several processors participate simultaneously
in the calculations while exchanging information via communication links. We place essentially no assumptions on the ordering
of computation and communication between processors thereby allowing for completely uncoordinated execution. We provide a
general convergence theorem for algorithms of this type, and demonstrate its applicability to several classes of problems
including the calculation of fixed points of contraction and monotone mappings arising in linear and nonlinear systems of
equations, optimization problems, shortest path problems, and dynamic programming.
This research was contacted at the M.I.T. Laboratory for Information and Decision Systems with partial support provided by
the Defense Advanced Research Projects Agency under Grant No. ONR-N00014-75-C-1183. 相似文献
229.
We investigate an ellipsoid algorithm for nonlinear programming. After describing the basic steps of the algorithm, we discuss
its computer implementation and present a method for measuring computational efficiency. The computational results obtained
from experimenting with the algorithm are discussed and the algorithm's performance is compared with that of a widely used
commercial code.
This research was supported in part by The National Science Foundation, Grant No. MCS78-02096. 相似文献
230.