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41.
单轴荷载下饱水岩石静态和动态抗压强度的细观力学分析 总被引:1,自引:0,他引:1
由于单轴荷载下饱水岩石的动态力学特性与静态力学特性存在很大差异,从宏观上进行力学分析
存在局限性。根据岩石受压全应力应变曲线的细观机制,分析了静态及动态单轴荷载条件下孔隙水影响饱水
岩石裂纹扩展的情况。在静态单轴压缩条件下,初始裂隙受压使自由水产生孔隙水压力,自由水对翼裂纹有
向外挤压的应力,促进裂纹扩展。在动态单轴压缩条件下,自由水会产生粘结力,抑制裂纹扩展。根据翼裂纹
受压扩展原理,推导出饱水单轴条件下动态抗压强度、静态抗压强度的计算公式,在相同断裂韧度下,饱水岩
石静态抗压强度风干岩石静态抗压强度饱水岩石动态抗压强度。对自然风干和饱水砂岩进行单轴静态、
动态压缩实验,结果与理论模型的结果相符。 相似文献
42.
43.
44.
压电材料平面裂纹尖端场的杂交应力有限元分析 总被引:3,自引:1,他引:3
基于复势理论和杂交变分原理建立了一种适用于力电耦合分析的杂交应力有限元模
型. 给出了建立刚度矩阵的主要公式和推导过程,单元内的位移场和应力场采用满足平
衡方程的复变函数级数解,假设的复变函数级数解事先精确满足裂纹的无应力和电位移法向
分量为零的条件,单元外边界的位移场假设按抛物线变化,
单元的刚度矩阵采用Gauss积分的方法得出. 通过对力电耦合裂尖场的数值计算验证了程序
的正确性和单元的有效性,同时也用所得结果校验了理论解. 相似文献
45.
The axisymmetric buckling (delamination) of a circular disk (plate) with a penny-shaped crack is analyzed using a continuum
model, piecewise-homogeneous model, and the three-dimensional linearized theory of stability. The FEM is used. The analysis
is carried out using various singular and ordinary finite elements. The numerical results obtained indicate that it is not
necessary to use singular finite elements to solve the problem
Published in Prikladnaya Mekhanika, Vol. 43, No. 9, pp. 120–129, September 2007. 相似文献
46.
G. V. Galatenko 《International Applied Mechanics》2007,43(7):745-753
The generalized Dugdale crack model is used to formulate two-parameter failure criteria for the cases of quasibrittle state
and developed plastic zones at a mode I crack tip. The failure criteria relate the fracture strength characteristics and the
stress mode at the crack tip through the plastic constraint factor. The critical state of bodies with cracks under uni-and
biaxial loading is analyzed in the cases of plane stress and plane strain using the Tresca and von Mises yield criteria. A
small-scale yield criterion, which is an analytic relation between the critical stress intensity factor and T-stresses, is established
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 47–57, July 2007. 相似文献
47.
A. M. Khludnev 《Journal of Applied Mechanics and Technical Physics》2008,49(4):553-567
The contact problem for two elastic plates aligned at a prescribed angle to each other is considered. The set of contact points
is assumed to be unknown in advance and to be determined only after the problem is solved. Various formulations of the problem
are given, and their equivalence is proved. A complete set of boundary conditions fulfilled on the contact domain is found,
and the character of satisfaction of these conditions is described. The asymptotic properties of solutions are studied for
rigidity parameters of the contacting plates tending to infinity.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 4, pp. 42–58, July–August, 2008. 相似文献
48.
Jianxiang Wang Zhuping Huang Huiling Duan Shouwen Yu Xiqiao Feng Gangfeng Wang Weixu Zhang Tiejun Wang LTCS and 《Acta Mechanica Solida Sinica》2011,24(1):52-82
This review article summarizes the advances in the surface stress effect in mechanics of nanostructured elements,including nanoparticles,nanowires,nanobeams,and nanofilms,and heterogeneous materials containing nanoscale inhomogeneities.It begins with the fundamental formulations of surface mechanics of solids,including the definition of surface stress as a surface excess quantity,the surface constitutive relations,and the surface equilibrium equations.Then,it depicts some theoretical and experimental studies of the mechanical properties of nanostructured elements,as well as the static and dynamic behaviour of cantilever sensors caused by the surface stress which is influenced by adsorption.Afterwards,the article gives a summary of the analytical elasto-static and dynamic solutions of a single as well as multiple inhomogeneities embedded in a matrix with the interface stress prevailing.The effect of surface elasticity on the diffraction of elastic waves is elucidated.Due to the difficulties in the analytical solution of inhomogeneities of complex shapes and configurations,finite element approaches have been developed for heterogeneous materials with the surface stress.Surface stress and surface energy are inherently related to crack propagation and the stress field in the vicinity of crack tips.The solutions of crack problems taking into account surface stress effects are also included.Predicting the effective elastic and plastic responses of heterogeneous materials while taking into account surface and interface stresses has received much attention.The advances in this topic are inevitably delineated.Mechanics of rough surfaces appears to deserve special attention due to its theoretical and practical implications.Some most recent work is reviewed.Finally,some challenges are pointed out.They include the characterization of surfaces and interfaces of real nanomaterials,experimental measurements and verification of mechanical parameters of complex surfaces,and the effects of the physical and chemical processes on the surface properties,etc. 相似文献
49.
进行了Ⅰ/Ⅱ复合型载荷作用下航空结构铝合金CTS试样线弹性的全场三维有限元计算,分析了复合型离面应力约束因子Tz和面内约束T应力的分布特性,研究了厚度和载荷条件对应力各分量及应力三轴性水平Rσ、应变能密度U0的影响以及这些量在实验中观察到的裂纹起裂方向上的特点。结果表明:(1)平面内约束T应力在此种试样形式下为零;(2)复合型裂纹的三维效应区与厚度成正比,为0.4-0.5B,与载荷条件基本无关,但是厚度效应随着载荷角的减小逐渐变小,到II型载荷时基本消失;(3)离面约束因子Tz随着径向和厚度尺寸的增加逐渐减小,但在周向基本不发生变化;(4)最小应变能密度U0min的方位能够表征此种材料三维复合型断裂的裂纹起裂方向。研究结果为建立三维复合型断裂准则提供了理论基础。 相似文献
50.
V型缺口裂端的三维应力状态及约束分析 总被引:1,自引:0,他引:1
利用三维有限元方法,研究了有限厚度板中V型缺口根部穿透裂纹前沿的三维弹性应力场。对不同厚度、不同缺口张开角和裂纹长度对应力强度因子及裂尖附近的三维约束程度的影响进行了分析,同时还讨论了三维约束区的大小。研究结果显示:当缺口张开角小于60度时,不同缺口的应力强度因子和离面约束因子的分布基本一致,角度的影响不明显。应力强度因子是厚度的函数,板中面的应力强度因子随厚度的增加逐渐减小趋近干平面值,最大为1.08倍的平面值。当板厚超过15倍的缺口深度时,应力强度因子最大值将从中面转移至接近自由表面位置,距中面约0.4倍板厚。三维约束非常明显的区域在裂尖前沿约0.45倍厚度的范围内.二维到三维的过渡区在裂尖前沿1.5倍厚度的区域内;在中面上三维效应影响区最大,随着离中面距离的增加逐渐减小,在自由表面上降为0。 相似文献