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831.
粗糙集是一种在信息系统中处理粗糙性和颗粒性的数据挖掘工具.本文从集值映射的角度研究并推广粗糙模型,使其能解决在论域和分类信息变化下对集合的近似问题.最后,讨论了集值映射下的粗糙集的性质. 相似文献
832.
With the help of continued fractions, we plan to list all the elements of the set Q△ = {aX2 + bXY + cY2 : a,b, c ∈Z, b2 - 4ac = △ with 0 ≤ b 〈 √△}of quasi-reduced quadratic forms of fundamental discriminant △. As a matter of fact, we show that for each reduced quadratic form f = aX2 + bXY + cY2 = (a, b, c) of discriminant △〉0(and of sign σ(f) equal to the sign of a), the quadratic forms associated with f and defined by {〈a+bu+cu2,b+2cu.c〉},with 1≤σ(f)u≤b/2|c| (whenever they exist), 〈c,-b-2cu,a+bu+cu2〉 with b/2|c|≤σ(f)u≤[w(f)]=[b+√△/2|c|], are all different from one another and build a set I(f) whose cardinality is #I(f)={1+[ω(f)],when(2c)|b,[ω(f)],when (2c)|b. If f and g are two different reduced quadratic forms, we show that I(f) ∩ I(g) = Ф. Our main result is that the set Q△ is given by the disjoint union of all I(f) with f running through the set of reduced quadratic forms of discriminant △〉0. This allows us to deduce a formula for #(Q△) involving sums of partial quotients of certain continued fractions. 相似文献
833.
Meesoon Ha 《Central European Journal of Physics》2009,7(3):575-583
We investigate the critical behavior of one-dimensional (1D) stochastic flow with competing nonlocal and local hopping events,
in context of the totally asymmetric simple exclusion process (TASEP) with a defect site in a 1D closed chain. The defect
site can effectively generate various boundary conditions, controlling the total number of particles in the system. Both open
and periodic-like setups exhibit dynamic instability transitions from a populated finite density phase to an empty road (ER)
phase as the nonlocal hopping rate increases. In the stationary populated phase, strong clustering promoted by nonlocal skids
drives such transitions and determines their scaling properties. By static and dynamic simulations, we locate such transition
points, and discuss their nature and scaling properties. In the open TASEP variant, we numerically establish that the instability
transition into the ER phase is second order in the regime where the entry point reservoir controls the current, while it
is first order in the regime where the bulk controls the current. Since it is well known that such transitions are absent
in the periodic TASEP variant, we compare our results in the open setup with those in the periodic-like setup, and discuss
the issue of the ensemble equivalence. Finally, the same discussion is extended to the symmetric cases.
相似文献
834.
For square, semipositive matrices A (Ax>0 for some x>0), two (nonnegative) equilibrants e(A) and E(A) are defined. Our primary goal is to develop theory from which each may be calculated. To this end, the collection of semipositive matrices is partitioned into three subclasses for each equilibrant, and a connection to those matrices that are scalable to doubly stochastic matrices is made. In the process a certain matrix/vector equation that is related to scalability of a matrix to one with line sums 1 is derived and discussed. 相似文献
835.
A molecular structural mechanics model for the numerical simulation of phonon dispersion relations of graphene is developed by relating the C-C bond molecular potential energy to the strain energy of the equivalent beam-truss space frame. With the stiffness matrix known and further based on the periodic structure characteristics, the Bloch theorem is introduced to develop the dispersion relation of graphene sheet. Being different from the existing structural mechanics model, interactions between the fourth-nearest neighbor atoms are further simulated with beam elements to compensate the reduced stretching stiffness, where as a result not only the dispersion relations in the low frequency field are accurately achieved, but results in the high frequency field are also reasonably obtained. This work is expected to provide new opportunities for the dynamic properties analysis of graphene and future application in the engineering sector. 相似文献
836.
837.
Generalized divisors on Gorenstein schemes 总被引:6,自引:0,他引:6
Robin Hartshorne 《K-Theory》1994,8(3):287-339
We develop a theory of generalized divisors on a Gorenstein scheme whereby any closed subscheme of pure codimension one without embedded points can be regarded as an effective divisor. Most of the usual theory of linear equivalence, associated sheaf, etc., carries over to this more general setting. The definition uses reflexive sheaves, so we first review the theory of reflexive modules. As an application, we give new definitions of liaison and biliaison for subschemes of
n
, which simplify the foundations of the theory of liaison. We also compute explicitly the set of generalized divisor classes on some reducible and singular schemes. 相似文献
838.
This paper studies the heat-release oscillation response of premixed flames to oscillations in reactant stream fuel/air ratio. Prior analyses have studied this problem in the linear regime and have shown that heat release dynamics are controlled by the superposition of three processes: flame speed, heat of reaction, and flame surface area oscillations. Each contribution has somewhat different dynamics, leading to complex frequency and mean fuel/air ratio dependencies. The present work extends these analyses to include stretch and non quasi-steady effects on the linear flame dynamics, as well as analysis of nonlinearities in flame response characteristics. Because the flame response is controlled by a superposition of multiple processes, each with a highly nonlinear dependence upon fuel/air ratio, the results are quite rich and the key nonlinearity mechanism varies with mean fuel/air ratio, frequency, and amplitude of excitation. In the quasi-steady framework, two key mechanisms leading to heat-release saturation have been identified. The first of these is the flame-kinematic mechanism, previously studied in the context of premixed flame response to flow oscillations and recently highlighted by Birbaud et al. (Combustion and Flame 154 (2008), 356–367). This mechanism arises due to fluctuations in flame position associated with the oscillations in flame speed. The second mechanism is due to the intrinsically nonlinear dependence of flame speed and mixture heat of reaction upon fuel/air ratio oscillations. This second mechanism is particularly dominant at perturbation amplitudes that cause the instantaneous stoichiometry to oscillate between lean and rich values, thereby causing non-monotonic variation of local flame speed and heat of reaction with equivalence ratio. 相似文献
839.
Vera V. Kartak 《Journal of Nonlinear Mathematical Physics》2013,20(4):110-129
The first part of this work is a review of the point classification of second order ODEs done by Ruslan Sharipov. His works were published in 1997-1998 in the Electronic Archive at LANL. The second part is an application of this classification to Painlevé equations. In particular, it allows us to solve the equivalence problem for Painlevé equations in an algorithmic form. 相似文献
840.
Mei Yin 《Physica A》2013
We aim at an explicit characterization of the renormalized Hamiltonian after decimation transformation of a one-dimensional Ising-type Hamiltonian with a nearest-neighbor interaction and a magnetic field term. To facilitate a deeper understanding of the decimation effect, we translate the renormalization flow on the Ising Hamiltonian into a flow on the associated Markov chains through the Markov–Gibbs equivalence. Two different methods are used to verify the well-known conjecture that the eigenvalues of the linearization of this renormalization transformation about the fixed point bear important information about all six of the critical exponents. This illustrates the universality property of the renormalization group map in this case. 相似文献