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81.
82.
Acoustic maps are the main diagnostic tools used by authorities for addressing the growing problem of urban acoustic contamination. Geostatistics models phenomena with spatial variation, but restricted to homogeneous prediction regions. The presence of barriers such as buildings introduces discontinuities in prediction areas. In this paper we investigate how to incorporate information of a geographical nature into the process of geostatistical prediction. In addition, we study the use of a Cost-Based distance to quantify the correlation between locations. 相似文献
83.
A novel fullerene-based building block for the synthesis of nanostructured materials has been designed with the aid of electronic structure theory calculations and molecular modeling. The building block consists of four trisaza-bridged C60 fullerene molecules linked to a central cubane (C8) unit. Each C60 unit is located on the vertex of a tetrahedron with edge of 2.2 nm. One possible packing mode of the building blocks to yield the nanostructured material is suggested. 相似文献
84.
Isabel Oitavem 《Mathematical Logic Quarterly》2008,54(3):323-329
This paper gives an implicit characterization of the class of functions computable in polynomial space by deterministic Turing machines – PSPACE. It gives an inductive characterization of PSPACE with no ad‐hoc initial functions and with only one recursion scheme. The main novelty of this characterization is the use of pointers (also called path information) to reach PSPACE. The presence of the pointers in the recursion on notation scheme is the main difference between this characterization of PSPACE and the well‐known Bellantoni‐Cook characterization of the polytime functions – PTIME. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
85.
Quantum mechanical ab initio simulation of the electron screening effect in metal deuteride crystals
A. Huke K. Czerski S. M. Chun A. Biller P. Heide 《The European Physical Journal A - Hadrons and Nuclei》2008,35(2):243-252
In antecedent experiments the electron screening energies of the d+d reactions in metallic environments have been determined
to be enhanced by an order of magnitude in comparison to the case of gaseous deuterium targets. The analytical models describing
averaged material properties have not been able to explain the experimental results so far. Therefore, a first effort has
been undertaken to simulate the dynamics of reacting deuterons in a metallic lattice by means of an ab initio Hartree-Fock calculation of the total electrostatic force between the lattice and the successively approaching deuterons
via path integration. The calculations have been performed for Li and Ta, clearly showing a migration of electrons from host
metallic to the deuterium atoms. However, in order to avoid more of the necessary simplifications in the model the utilization
of a massive parallel supercomputer would be required. 相似文献
86.
87.
Li-Lian Gao Nezih Altay E. Powell Robinson 《Mathematical and Computer Modelling》2008,47(11-12):1254-1263
In the coordinated lot-size problem, a major setup cost is incurred when at least one member of a product family is produced and a minor setup cost for each different item produced. This research consolidates the various modeling and algorithmic approaches reported in the literature for the coordinated replenishment problem with deterministic dynamic demand. For the two most effective approaches, we conducted extensive computational experiments investigating the quality of the lower bound associated with the model’s linear programming relaxation and the computational efficiency of the algorithmic approaches when used to find heuristic and optimal solutions. Our findings indicate the superiority of the plant location type problem formulation over the traditional approach that views the problem as multiple single-item Wagner and Whitin problems that are coupled by major setup costs. Broader implications of the research suggest that other classes of deterministic dynamic demand lot-size problems may also be more effectively modeled and solved by adapting plant location type models and algorithms. 相似文献
88.
Federico Camia 《Random Structures and Algorithms》2008,33(3):377-408
We consider a type of dependent percolation introduced in 2 , where it is shown that certain “enhancements” of independent (Bernoulli) percolation, called essential, make the percolation critical probability strictly smaller. In this study we first prove that, for two‐dimensional enhancements with a natural monotonicity property, being essential is also a necessary condition to shift the critical point. We then show that (some) critical exponents and the scaling limit of crossing probabilities of a two‐dimensional percolation process are unchanged if the process is subjected to a monotonic enhancement that is not essential. This proves a form of universality for all dependent percolation models obtained via a monotonic enhancement (of Bernoulli percolation) that does not shift the critical point. For the case of site percolation on the triangular lattice, we also prove a stronger form of universality by showing that the full scaling limit 12 , 13 is not affected by any monotonic enhancement that does not shift the critical point. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008 相似文献
89.
In this article, we develop a computational method for an algorithmic process first posed by Polyrakis in 1996 in order to check whether a finite collection of linearly independent positive functions in C[a,b] forms a lattice-subspace. Lattice-subspaces are closely related to a cost minimization problem in the theory of finance that ensures the minimum-cost insured portfolio and this connection is further investigated here. Finally, we propose a computational method in order to solve the minimization problem and to calculate the minimum-cost insured portfolio. All of the numerical work is performed using the Matlab high-level language. 相似文献
90.
S. V. Ivanov 《Geometriae Dedicata》2008,131(1):1-26
We study the computational complexity of basic decision problems of 3-dimensional topology, such as to determine whether a
triangulated 3-manifold is irreducible, prime, ∂-irreducible, or homeomorphic to a given 3-manifold M. For example, we prove that the problem to recognize whether a triangulated 3-manifold is homeomorphic to a 3-sphere, or
to a 2-sphere bundle over a circle, or to a real projective 3-space, or to a handlebody of genus g, is decidable in nondeterministic polynomial time (NP) of size of the triangulation. We also show that the problem to determine whether a triangulated orientable 3-manifold is
irreducible (or prime) is in PSPACE and whether it is ∂-irreducible is in coNP. The proofs improve and extend arguments of prior author’s article on the recognition problem for the 3-sphere.
相似文献