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791.
随着计算机断层(CT,computed tomography)和MRI(nuclear magnetic resonance imaging)技术的发展,困扰着活体足建模的问题得到了解决,特别是DICOM(digital imaging and communications in medicine)标准的建立为计算机辅助足生物力学的研究开辟了一条新的途径。探讨了一种集CT扫描技术、Mimics(Materiaise’s interactive medical imagecontrol system)和ANSYS软件为一体的活体足研究的生物力学方法。利用PHILIPS 64排螺旋CT扫描仪获得了足部骨组织的DICOM图像;在工作站上用三维重建软件Mimics分别对足部骨、皮肤等建模,利用Mimics的逆向工程模块对模型去噪、平滑处理和点云运算,之后进行模型面网格的划分;在ANSYS中建立约束、加载载荷并求解,从而实现足的生物力学研究。CT扫描的足部断层图像通过Mimics能够实现对足的外型和骨的三维重建,在逆向工程软件中可以实现模型的体网格划分,用ANSYS实现有限元分析。根据运动中足的动力学规律(如通过压力分布测量平台),能够实现足的表面和骨的动力学和应力应变的计算机仿真研究,为运动损伤或运动鞋的评价等提供了依据。 相似文献
792.
Based on Timoshenko's beam theory and Vlasov's thin-walled member theory, a new model of spatial thin-walled beam element is developed for analyzing geometrical and physical nonlinearity, which incorporates an interior node and independent interpolations of bending angles and warp and takes diversified factors into consideration, such as traverse shear deformation, torsional shear deformation and their coupling, coupling of flexure and torsion, and the second shear stress. The geometrical nonlinear strain is formulated in updated Lagarange (UL) and the corresponding stiffness matrix is derived. The perfectly plastic model is used to account for physical nonlinearity, and the yield rule of von Mises and incremental relationship of Prandtle-Reuss are adopted. Elastoplastic stiffness matrix is obtained by numerical integration based on the finite segment method, and a finite element program is compiled. Numerical examples manifest that the proposed model is accurate and feasible in the analysis of thin-walled structures. 相似文献
793.
794.
采用ANSYS/LS-DYNA软件对SUS 304奥氏体不锈钢薄板的摩擦耦合变形过程进行了数值模拟.采用隐式-显式序列求解法和分段线性塑性材料模型,分析了钢带摩擦耦合变形时的应力分布规律及载荷、下压量和滑动速度等因素对钢带剪应力、主应力及等效应力的影响.结果表明:摩擦耦合变形的试验参数显著影响钢带的应力分布,验证了钢带在低于其屈服强度的应力条件下发生塑性变形的摩擦诱发效应.对奥氏体不锈钢摩擦诱发马氏体转变行为的研究及其摩擦学性能的改善具有一定的指导意义. 相似文献
795.
796.
Damage mechanics based on the cohesive zone model were applied to study the anodic dissolution stress corrosion cracking (SCC) in flat and U-shaped edge-notched specimens. The simulation results show that corrosion product films (CPFs) facilitate crack initiation in SCC due to the CPF-induced stress and CPF rupture. In the flat specimen, SCC susceptibility increases with the CPF thickness and CPF Young’s modulus, while it decreases with CPF fracture strength. For the U-shaped edge-notched specimen, the normalised threshold stress intensity factor KISCC/KIC decreases with the CPF thickness and notch depth. 相似文献
797.
Inverse methods offer a powerful tool for the identification of the elasto-plastic material parameters. One of the advantages
with respect to classical material testing is the fact that those inverse methods are able to deal with heterogeneous deformation
fields. The basic principle of the inverse method that is presented in this paper, is the comparison between experimentally
measured strain fields and those computed by the finite element (FE) method. The unknown material parameters in the FE model
are iteratively tuned so as to match the experimentally measured and the numerically computed strain fields as closely as
possible. This paper describes the application of an inverse method for the identification of the hardening behavior and the
yield locus of DC06 steel, based on a biaxial tensile test on a perforated cruciform specimen. The hardening behavior is described
by a Swift type hardening law and the yield locus is modeled with a Hill 1948 yield surface. 相似文献
798.
There are problems in linear elasticity theory whose corresponding deformations, usually associated with singular stress fields,
are open to question because they are not one-to-one and predict self-intersection. Recently, a theory has been advanced to
handle such situations, which consists in minimizing the quadratic energy functional of linear elasticity subject to the constraint
of local injectivity. In particular, the Jacobian of the deformation gradient is required to be not less than an arbitrarily
small positive quantity, and, thus, the local orientation is preserved. Here, this theory is applied to the classical Lekhnitskii
problem of an elastic aelotropic circular disk which is loaded on its boundary by a uniform radial pressure. Without the injectivity
constraint, this classical linear problem has a unique solution. This example, with the injectivity constraint, already has
been considered in previous works, but radial symmetry was assumed in order to reduce the problem from 2D to 1D. Here, making
use of an interior penalty formulation, a numerical scheme is implemented that solves a full 2D problem. Remarkably, it is
shown that there are values of the material moduli for which the minimal potential energy solution is no longer symmetric,
producing a strong azimuthal shear and nominally a 180° rotation of an internal central core of the disk. Although the elastic
strain energy is quadratic and convex, the strongly nonlinear character of the constraint allows for bifurcation instabilities.
We gratefully acknowledge the partial support of the Minnesota Supercomputing Institute and the Italian “Ministero per l’Università e la Ricerca Scientifica” under the program PRIN 2005 “Affidabilità di elementi
in vetro strutturale: indagini teoriche e sperimentali sulla risposta termo-meccanica del materiale e di strutture trasparenti
di tipo innovativo”. R.F. gratefully acknowledges the Department of Civil and Environmental Engineering at the Politecnico di Bari, Italy, for their kind hospitality and support during his visit of 2006. We appreciate the helpful comments and suggestions
of Paolo Podio-Guidugli on an earlier draft of this work. 相似文献
799.
800.
该文利用投影型插值,对于变系数两点边值问题,获得了一个高精度的有限元强校正格式,数值实验更验证了这一结果. 相似文献