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841.
R. R. Gadyl'shin 《Mathematical Notes》1997,61(4):409-416
The eigenvalue problem for the Laplace operator with the Neumann boundary conditions in a domain that has a thin spike of
finite length is considered for the case in which the limit value is an eigenvalue both for the main body and the spike. The
method of matched asymptotic expansions is used to construct total asymptotics of the eigenvalues of the perturbed problem
and obtain closed formulas for the leading asymptotic terms.
Translated fromMatematicheskie Zametki, Vol. 61, No. 4, pp. 494–502, April, 1997.
Translated by V. E. Nazaikinskii 相似文献
842.
J. Liu F. Rybnikar A. J. East P. H. Geil 《Journal of Polymer Science.Polymer Physics》1993,31(13):1923-1940
4-Acetoxy 4′-carboxy biphenyl has been polymerized from solution, the bulk melt, and in constrained thin films, all below the melting point of the monomer as measured by differential scanning calorimetry (DSC). An isothermal sublimation–recrystallization–melting (and chemical change)–polymerization–crystallization process is proposed. From solution and in the thin films, single crystals consisting of ca. 100 Å thick lamellae are observed, with evidence for monomer addition–reaction on the end (top and bottom) surfaces. The bulk samples are fibrous, the “fibers” consisting of whisker-like single crystals. The polymer is highly heat and radiation (electron beam) resistant, with numerous successive electron diffraction (ED) patterns from the same crystal or sheared sample permitting comparison of the changes in ED patterns with transitions seen by DSC at ca. 350, 530, and 590°C. Phase I (a = 7.8, b = 5.5, c = 10.8 Å), a possible phase II (a = 15.6, b = 3.6 Å c = unknown), and a phase III (a = 9.0, b = 5.2 = √3a, c = 10.8 Å). Phases I and II are seen in samples polymerized at temperatures at and below 310°C; phase III is observed in samples polymerized at and above 350°C and in sheared samples. © 1993 John Wiley & Sons, Inc. 相似文献
843.
The thermofluid dynamic fields in two-dimensional multiconnected domains are analysed by solving the Navier–Stokes equations with the Boussinesq approximation in the vorticity–velocity formulation. The need of an integral condition for the pressure to be single-valued on each independent irreducible loop, in analogy with the ω–Ψ formulation, is demonstrated. The field equations are discretized by a finite difference technique and solved at the steady state via an alternating direction implicit method of a scalar type. Two test cases at low Reynolds and Rayleigh numbers are considered: the multiconnected driven cavity and an annulus with isothermal walls and stationary or rotating inner cylinder. 相似文献
844.
S. Yu. Fialko 《International Applied Mechanics》2003,39(3):324-331
A direct method is proposed to solve large systems of linear algebraic equations that arise in using the finite-element method. The method suggests to subdivide the initial structure into nonoverlapping, deeply nested substructures. The subdivision is performed automatically by the nested dissection method. Initially, the structure is subdivided into isolated finite elements. The solution process is step-by-step assembly of subsystems with simultaneous elimination of unknowns for completely assembled ones. The efficiency of the method is demonstrated by comparing it with the incomplete Cholesky conjugate-gradient method and the traditional envelope method as applied to a circular cylindrical shell with high ribs 相似文献
845.
Cabanillas V. R. de Menezes S. B. Zuazua E. 《Journal of Optimization Theory and Applications》2001,110(2):245-264
We consider the null controllability problem for the semilinear heat equation with nonlinearities involving gradient terms in an unbounded domain of
N
with Dirichlet boundary conditions. The control is assumed to be distributed along a subdomain such that the uncontrolled region \ is bounded. Using Carleman inequalities, we prove first the null controllability of the linearized equation. Then, by a fixed-point method, we obtain the main result for the semilinear case. This result asserts that, when the nonlinearity is
C1
and globally Lipschitz, the system is null controllable. 相似文献
846.
847.
K. Wlodarczyk D. Klim E. Gontarek 《Proceedings of the American Mathematical Society》2000,128(12):3475-3482
Conditions guaranteeing the uniform convergence to constant maps of random iterations of holomorphic contractions on unbounded domains in complex Banach spaces are established.
848.
Stefan Johansson. 《Mathematics of Computation》2000,69(229):339-349
Let be a totally real algebraic number field and an order in a quaternion algebra over . Assume that the group of units in with reduced norm equal to is embedded into as an arithmetic Fuchsian group. It is shown how Ford's algorithm can be effectively applied in order to determine a fundamental domain of as well as a complete system of generators of .
849.
850.
E. Simonnet 《Physica D: Nonlinear Phenomena》2008,237(20):2539-2552
We investigate the behavior of the unstable discrete spectrum of the linearized 2-D Euler equation when the domain is smoothly perturbed. It is shown that when a self-adjoint Schrödinger-type operator undergoes a codimension-1 bifurcation it translates into a bifurcation in the linearized Euler equation associated with an instability either appearing or disappearing.We give sufficient conditions in order to observe smooth quadratic growth of the unstable eigencurves of the linearized Euler equation. The critical exponent is explicitly given as a function of the null-vector involved into the codimension-1 bifurcation using first and second-order moments of a Laplace transform.This analysis provides an explanation for the successive symmetry-breaking bifurcations observed in models of the mid-latitude oceans. An explicit example is also given. 相似文献