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911.
《International Journal of Solids and Structures》2014,51(25-26):4477-4484
In this paper, based on the principle of virtual work, we formulate the equivalent eigenstrain approach for inhomogeneous inclusions. It allows calculating the elastic deformation of an arbitrarily connected and shaped inhomogeneous inclusion, by replacing it with an equivalent homogeneous inclusion problem, whose eigenstrain distribution is determined by an integral equation. The equivalent homogeneous inclusion problem has an explicit solution in terms of a definite integral. The approach allows solving the problems about inclusions of arbitrary shape, multiple inclusion problems, and lends itself to residual stress analysis in non-uniform, heterogeneous media. The fundamental formulation introduced here will find application in the mechanics of composites, inclusions, phase transformation analysis, plasticity, fracture mechanics, etc. 相似文献
912.
Porous materials, such as geomaterials, exhibit a behaviour dependent on the confining pressure. The aim of this paper is to study the degradation of the elastic stiffness of mean stress dependent materials, due to the deterioration of the microstructure during loading.Continuum damage mechanics offers a framework to model this rigidity deterioration. In addition to the concept of effective stress, a choice has to be made between two widely used hypotheses, the principle of strain equivalence and the principle of equivalent elastic energy, in order to build a complete modelling framework.A mean stress dependent hyperelastic formulation is used to ensure a conservative behaviour, and associated to the two previous damage modelling assumptions, whose effects are compared. This allows for mean stress dependent elasticity to be reproduced, with elastic moduli increasing with mean stress while decreasing with damage. 相似文献
913.
Lili Wang ;Shisheng Hu ;Liming Yang ;Zijian Sun ;Jue Zhu ;Huawei Lai ;Yuanyuan Ding 《Acta Mechanica Solida Sinica》2014,27(4):331-344
The split Hopkinson pressure bar(SHPB) technique and the wave propagation inverse analysis(WPIA) technique are both extensively used to experimentally investigate the impact behavior of materials, although neither of them alone provides a fully satisfactory analysis. In the present paper, attention is given to new experimental techniques by incorporating a damagemodified constitutive model into the SHPB technique and combining the Hopkinson pressure bar(HPB) technique with WPIA. First, to distinguish the response due to dynamic constitutive behavior and the response due to dynamic damage evolution, the SHPB method incorporating a damage-modified constitutive model is developed, including an explicit damage-modified Zhu–Wang–Tang model and an implicit damage-modified constitutive model. Second, when the SHPB results become invalid, a method of combining new Lagrange inverse analyses with the HPB technique is developed, including cases of the HPB arranged in front of a long specimen and behind the specimen. As examples of these new methods, typical results are given for nonlinear viscoelastic polymers and concretes considering damage evolution, a super-elastic Ti–Ni alloy with phase transformation and an aluminum foam with shock waves propagating within it. 相似文献
914.
915.
916.
渐进结构优化方法失效机理分析与改进策略 总被引:1,自引:0,他引:1
针对ESO方法在Zhou-Rozvany算例中失效的根本机理进行了深入的分析,提出有效的改进策略。指出ESO方法失效的根本原因既不是网格划分的数目过少,也不是优化策略的不合理,而是对于各单元内材料有效性评估的误差所致。针对ESO方法的失效机理引入奇异单元的概念,并提出了一种基于奇异单元的改进策略,改进后的ESO方法能够在网格较为稀疏的情况下保证0-1优化结果的合理性。 相似文献
917.
In this study, slow strain rate tensile testing at elevated temperature is used to evaluate the influence of temperature and strain rate on deformation behaviour in two different austenitic alloys. One austenitic stainless steel (AISI 316L) and one nickel-base alloy (Alloy 617) have been investigated. Scanning electron microscopy related techniques as electron channelling contrast imaging and electron backscattering diffraction have been used to study the damage and fracture micromechanisms. For both alloys the dominante damage micromechanisms are slip bands and planar slip interacting with grain bounderies or precipitates causing strain concentrations. The dominante fracture micromechanism when using a slow strain rate at elevated temperature, is microcracks at grain bounderies due to grain boundery embrittlement caused by precipitates. The decrease in strain rate seems to have a small influence on dynamic strain ageing at 650°C. 相似文献
918.
关于如何提升惠斯通电桥灵敏度一直是惠斯通电桥研究的热门话题.运算放大器组装成为的差分放大电路在一定范围内可以线性放大输入电压.但是,使用运算放大器提高电桥灵敏度的方法并未被采用.本文采用LM358N型运算放大器来提高电桥两端电势差的测量精度,从而提升惠斯通电桥的灵敏度.我们使用Multisim软件对该方案进行仿真,结果表明如果将放大倍数调至20倍,那么实际误差将小于2%.经过对改进电桥进行实际测量,实验和理论结论符合得很好.采用此方法可以得到一个易操作、低成本、高灵敏度的惠斯通电桥. 相似文献
919.
利用密度泛函理论和非平衡态格林函数相结合的方法,系统地研究了边修饰Net-Y纳米带的电子结构和器件特性的应变调控效应..计算表明:本征纳米带为金属,但边缘的氢或氧原子端接能使其转变为半导体.应变能有效地调控纳米带带隙的大小,适当的应变使能带结构从间接带隙转变为较小的直接带隙,这有利于光的吸收.应变也能改变纳米带的功函数,压缩应变能明显减小功函数,这有利于纳米带实现场发射功能.特别是应变能有效地调控纳米带相关器件的I-V特性,能使其开关比(Ion/Ioff)达到106,据此,可设计一个机械开关,通过拉伸及压缩纳米带使其可逆地工作在“开”和“关”态之间.这种高开关比器件也许对于制备柔性可穿戴电子设备具有重要意义. 相似文献
920.
We study the effect of strain on band structure and valley-dependent transport properties of graphene heterojunctions. It is found that valley-dependent separation of electrons can be achieved by utilizing strain and on-site energies. In the presence of strain, the values of transmission can be effectively adjusted by changing the strengths of the strain, while the transport angle basically keeps unchanged. When an extra on-site energy is simultaneously applied to the central scattering region, not only are the electrons of valleys K and K' separated into two distinct transmission lobes in opposite transverse directions, but the transport angles of two valleys can be significantly changed. Therefore, one can realize an effective modulation of valley-dependent transport by changing the strength and stretch angle of the strain and on-site energies, which can be exploited for graphene-based valleytronics devices. 相似文献