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121.
122.
The fundamental solutions of elasticity are used to establish a numerical method for elastic and plastic multiple crack problems in two dimensions. The continuous distributions of the point forces, dislocations, and the plastic sources are used systematically to model the crack, non-crack boundary, and the plastic deformation. Use of these singularities are guided strictly by the physical interpretation of the problem. We adopt Muskhelishvili's complex variable formalism that facilitate the analytical evaluation of the integrals representing the continuous distributions of the singularities. The resulting numerical method is concise and accurate enough to be used for elastic and plastic multiple crack problems. 相似文献
123.
Behavior of concrete cylinders confined by carbon-composite tapes and prestressed yarns 1. Experimental data 总被引:1,自引:0,他引:1
V. Tamuzs R. Tepfers Chi-Sang You T. Rousakis I. Repelis V. Skruls U. Vilks 《Mechanics of Composite Materials》2006,42(1):13-32
The results of a comprehensive test program for the mechanical behavior of round concrete specimens confined by carbon-fiber
epoxy tapes and prestressed carbon yarns are reported. Five different concrete batches of compressive strength from 20 to
100 MPa and the confinement of various thickness and pretension level were investigated. The specimens, which were subjected
to monotonic or repeated compressive loadings, showed a nonlinear stress-strain behavior with a significant ductility and
increased ultimate strength, in contrary to the brittle behavior of plain concrete. The limit of linearity on the stress-strain
diagrams of the confined concrete roughly coincided with the ultimate strength of plain concrete. Above this limit, the damage
accumulation and plastic deformations proceeded in the confined specimens. This fact was evidenced by the increasing slope
of deformation diagrams in unloadings and repeated loadings and by the pronounced residual strains. The limit of linearity
could be raised significantly by pretension of the carbon yarns during their winding.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 21–44, January–February, 2006. 相似文献
124.
K.E. Aifantis 《Journal of the mechanics and physics of solids》2005,53(5):1047-1070
A deformation-theory version of strain-gradient plasticity is employed to assess the influence of microstructural scale on the yield strength of composites and polycrystals. The framework is that recently employed by Fleck and Willis (J. Mech. Phys. Solids 52 (2004) 1855-1888), but it is enhanced by the introduction of an interfacial “energy” that penalises the build-up of plastic strain at interfaces. The most notable features of the new interfacial potential are: (a) internal surfaces are treated as surfaces of discontinuity and (b) the scale-dependent enhancement of the overall yield strength is no longer limited by the “Taylor” or “Voigt” upper bound. The variational structure associated with the theory is developed in generality and its implications are demonstrated through consideration of simple one-dimensional examples. Results are presented for a single-phase medium containing interfaces distributed either periodically or randomly. 相似文献
125.
An analytical model is developed for the response of clamped monolithic and sandwich beams subjected to impulse loading over a central loading patch. A number of topologies of sandwich core are investigated, including the honeycomb core, pyramidal core, prismatic diamond core and metal foam. The various cores are characterised by their dependencies of through-thickness compressive strength and longitudinal tensile strength upon relative density. Closed-form expressions are derived for the deflection of the beam when the ratio r of length of loading patch to the beam span exceeds 0.5. In contrast, an ordinary differential equation needs to be solved numerically for the choice r<0.5. Explicit finite element calculations show that most practical shock loadings can be treated as impulsive and the accuracy of the impulsive analytical predictions is confirmed. The analytical formulae are employed to determine optimal geometries of the sandwich beams that maximise the shock resistance of the beams for a given mass. The optimisation reveals that sandwich beams have a superior shock resistance relative to monolithic beams of the same mass, with the prismatic diamond core sandwich beam providing the best performance. Further, the optimal sandwich beam designs are only mildly sensitive to the length of the loading patch. 相似文献
126.
An experimental study was carried out for the cyclic properties of pure aluminium subjected to uniaxial cyclic straining and stressing. For a material of pure aluminium the effects of the cyclic strain amplitude history and mean strain on the cyclic deformation behavior were investigated, and the influences of stress amplitude, mean stress and their histories on cyclic creep (i. e., ratcheting) were analyzed. It is shown that either uniaxial cyclic property under cyclic straining or ratcheting behavior under asymmetric uniaxial loading depends not only on the current loading, but also on the previous loading history. Some significant results were obtained.Financial support from NFSC is acknowledged. 相似文献
127.
Xiang Hongjun Wang Jinhua Chen Anping 《Annals of Differential Equations》2005,21(4):604-615
In this paper, a class of two-dimensional shunting inhibitory cellular neural networks with distributed delays and variable coefficients system is studied. By using the Schauder's fixed point theorem and Lyapunov function, we obtain some sufficient conditions about the existence and attractivity of almost periodic solutions to the above system, and all its solutions converge to such almost periodic solution. An example is given to illustrate that the conditions of our results are feasible. 相似文献
128.
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130.
A zero-curvature criterion is proposed to determine the practical collapse load. Six tests have been carried out on spherical pressure vessels with cylindrical nozzle. Results of these tests and other experimental data quoted from different references are discussed in order to compare the new criterion with various previously proposed criteria. It is concluded that: (1) the zero-curvature point is a characteristic point of the experimental curve and that the new criterion is an objective criterion without any artificial coefficient. (2) the deviation of the collapse load estimated by the new criterion is smaller than that estimated by other criteria.Supported by the Chinese National Foundation of Natural Science. 相似文献