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991.
A boundary integral method was developed for simulating the motion and deformation of a viscous drop in an axisymmetric ambient Stokes flow near a rigid wall and for direct calculating the stress on the wall. Numerical experiments by the method were performed for different initial stand-off distances of the drop to the wall, viscosity ratios, combined surface tension and buoyancy parameters and ambient flow parameters. Numerical results show that due to the action of ambient flow and buoyancy the drop is compressed and stretched respectively in axial and radial directions when time goes. When the ambient flow action is weaker than that of the buoyancy the drop raises and bends upward and the stress on the wall induced by drop motion decreases when time advances. When the ambient flow action is stronger than that of the buoyancy the drop descends and becomes flatter and flatter as time goes. In this case when the initial stand-off distance is large the stress on the wall increases as the drop evolutes but when the stand-off distance is small the stress on the wall decreases as a result of combined effects of ambient flow, buoyancy and the stronger wall action to the flow. The action of the stress on the wall induced by drop motion is restricted in an area near the symmetric axis, which increases when the initial stand-off distance increases. When the initial stand-off distance increases the stress induced by drop motion decreases substantially. The surface tension effects resist the deformation and smooth the profile of the drop surfaces. The drop viscosity will reduce the deformation and migration of the drop. 相似文献
992.
基于广义变分原理得到的磁力计算公式,采用塑性增量理论,Mises屈服准则和有效的增量有限元计算方法,研究了线性强化材料铁磁矩形板的磁弹塑性弯曲行为。在文中定量模拟了铁磁简支矩形板在外加磁场作用下的挠度特征曲线,铁磁板发生塑性变形时的构型图和不同外加磁场下的中截面构型,以及铁磁板在卸载后的残余挠度特征曲线等力学特征,分析了塑性区域随磁场增加而扩展的情况。数值结果表明:当铁磁矩形板上的部分区域发生塑性屈服后,其变形明显大于相同磁场条件下铁磁板发生的弹性变形值;且随着外加磁场倾角的增大(0°<α≤45°),铁磁板进入塑性屈服状态的临界屈服磁场值减小;铁磁板的中截面构形为双半波型,其塑性区域由铁磁板两侧挠度最大的区域向板的中心区域扩展,板的中心最后进入塑性区域等。 相似文献
993.
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996.
A mathematical model is developed for saturated flow of a Newtonian fluid in a thermoelastic, homogeneous, isotropic porous medium domain under nonisothermal conditions. The model contains mass, momentum and energy balance equations. Both the momentum and energy balance equations have been developed to include a Forchheimer term which represents the interaction at the solid-fluid interface at high Reynolds numbers. The evolution of these equations, following an abrupt change in both fluid pressure and temperature, is presented. Using a dimensional analysis, four evolution periods are distinguished. At the very first instant, pressure, effective stress, and matrix temperature are found to be disturbed with no attenuation. During this stage, the temporal rate of pressure change is linearly proportional to that of the fluid temperature. In the second time period, nonlinear waves are formed in terms of solid deformation, fluid density, and velocities of phases. The equation describing heat transfer becomes parabolic. During the third evolution stage, the inertial and the dissipative terms are of equal order of magnitude. However, during the fourth time period, the fluid's inertial terms subside, reducing the fluid's momentum balance equation to the form of Darcy's law. During this period, we note that the body and surface forces on the solid phase are balanced, while mechanical work and heat conduction of the phases are reduced. 相似文献
997.
998.
静电陀螺仪实心球转子变形分析 总被引:6,自引:0,他引:6
介绍了静电陀螺仪实心球转子的两种典型结构,并利用有限元仿真工具根据工作环境对这两种结构分别进行了离心变形、温度变形、压力变形以及这三种载荷的耦合变形的仿真分析。得出了实心球转子的变形规律及变形量,为转子的设计和静电陀螺的建模提供了重要的参考依据。 相似文献
999.
One purpose of this paper is to give a brief overview on the research status of deformation, fracture and toughening mechanisms
of polymers, including experimental, theoretical and numerical studies. Emphasis is on the more recent progresses of micromechanics
of rubber particle cavitation and crazing, and the development of fracture criteria for ductile polymers.
The other purpose is to study the effect of triaxial stress constraint on the deformation and fracture behavior of polymers.
Polycarbonate (PC), acrylonitrile-butadienestyrene (ABS) and PC/ABS alloy are considered in this investigation. A series of
circumferentially blunt-notched bars are used to experimentally generate different triaxial stress fields. The fracture surfaces
of specimens with different notch radius are examined by scanning electron microscope (SEM) to study the fracture and toughening
mechanisms of polymer alloy. It is shown that the triaxial stress constraint has a significant effect on the deformation,
fracture and toughening of PC, ABS and PC/ABS alloy. We will also discuss the extent to which a micromechanics criterion proposed
by the first author can serve as a fracture criterion for ductile polymers. A new ductile fracture parameter is emphasized,
which can be employed to evaluate the fracture ductility of polymers. Stress state independence of the parameter for the PC,
ABS and PC/ABS alloy has been experimentally verified.
The project supported by the National Natural Science Foundation of China (10125212), the Trans-Century Training Program Foundation
and the Key Research Fund of the Education Ministry of China (01159) 相似文献
1000.
For the thermoelastic dynamic axisymmetric problem of a finite orthotropic hollow cylinder, one comes closer to reality to
involve the effect of axial strain than to consider the plane strain case only. However, additional mathematical difficulties
should be encountered and a different solution procedure should be developed. By the separation of variables, the thermoelastic
axisymmetric dynamic problem of an orthotropic hollow cylinder taking account of the axial strain is transformed to a Volterra
integral equation of the second kind for a function of time, which can be solved efficiently and quickly by the interpolation
method. The solutions of displacements and stresses are obtained. It is noted that the present method is suitable for an orthotropic
hollow cylinder with an arbitrary thickness subjected to arbitrary axisymmetric thermal loads. Numerical comparison is made
to show the effect of the axial strain on the displacements and stresses.
The project supported by the National Natural Science Foundation of China (10172075) and China Postdoctoral Science Foundation
(20040350712) 相似文献