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A new isolator composed of a steel rope spring and a magneto-rheological (MR) damper was designed and a study on low-frequency mechanical characteristics of MR dampers in isolators was carried out. It used the characteristics of the MR damper, such as fast response, controllable damping, small energy consumption, wide dynamic scope, and great adaptation. The relationships between MR damping forces and influencing factors were analyzed based on experimental data. The results show that damping force is not only related to structural dimensions, but also closely related to controllable current and vibration frequency. Finally, the empirical formula for damping forces was corrected, and the relationship between correction coefficients and factors analyzed. 相似文献
403.
为预测圆柱形桥墩周围的局部冲刷坑形态和发展,基于计算流体动力学和泥沙运动理论开展了桥墩周围局部冲刷的三维数值模拟。首先使用雷诺时均Navier-Stokes方程和标准K-ε湍流模型对圆柱形桥墩周围三维复杂流场进行数值模拟,将床面瞬时切应力作为泥沙起动及运输的水动力学条件,计算出床底泥沙的单宽体积输沙率,以此为基础得到河床高程坐标的瞬时变化;再采用边界自适应网格技术修改动边界计算域网格,计算得到圆柱形桥墩周围局部冲刷坑的演化过程。结果表明:桥墩周围局部冲刷三维数值模拟结果与试验结果基本一致,数值模拟方法能用来预测圆柱形桥墩周围的局部冲刷情况。 相似文献
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《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(3):449-462
Engine mounts are used in the automotive industry to isolate engine and chassis by reducing the noise and vibration imposed from one to the other. This paper describes modelling, simulation and design of a semi-active engine mount that is designed specifically to address the complicated vibration pattern of variable displacement engines (VDE). The ideal isolation for VDE requires the stiffness to be switchable upon cylinder activation/deactivation operating modes. In order to have a modular design, the same hydraulic engine mount components are maintained and a novel auxiliary magneto-rheological (MR) fluid chamber is developed and retrofitted inside the pumping chamber. The new compliance chamber is a controllable pressure regulator, which can effectively alter the dynamic performance of the mount. Switching between different modes happens by turning the electrical current to the MR chamber magnetic coil on and off. A model has been developed for the passive hydraulic mount and then it is extended to include the MR auxiliary chamber as well. A proof-of-concept prototype of the design has been fabricated which validates the mathematical model. The results demonstrate unique capability of the developed semi-active mount to be used for VDE application. 相似文献
406.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(11):871-885
This article presents a model for solving solid–fluid interactions in vehicles carrying liquids. A tractor–semitrailer model is developed by incorporating suspension systems and tire dynamics. Owing to the solid–fluid interaction, equations of motion for the vehicle system are coupled. To simplify the complicated solution procedure, the coupled equations are solved separately using two different codes. Each code is analyzed separately; but as the parameters of the two codes depend on each other, the codes must be connected at the end of each time step. To determine the dynamic behavior of the system, different braking moments are applied. As the braking moments increase, braking time decreases. However, it turns out that increasing the braking moment to more than a certain level produces no significant results. It is also shown that vehicles carrying fluids need a greater amount of braking moments in comparison to vehicles carrying solids during braking. In addition, as the level of the fluid inside the tanker increases, from one-third to two-third of the tanker’s volume, the sloshing forces applied to the tanker’s walls increase. It was also concluded that the strategy used in this article to solve for the solid–fluid interaction by incorporating vehicle dynamic effects represents an effective method for determining the dynamic behavior of vehicles carrying fluids in other critical maneuvers. 相似文献
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晃荡是一种非常复杂的非线性液体流动现象,载液船舶的晃荡问题颇受关注,因为在外界的激励下液舱内会产生剧烈的晃荡现象,巨大的晃荡冲击力会造成结构的破坏.文中建立了三维晃荡数学模型及数值计算模型,借助处理自由表面的VOF(volume of fluid)方法对液舱内液体晃荡的自由表面进行追踪,编制程序实现了液舱内三维液体非线性晃荡的数值模拟,并就三维刚性液舱内粘性液体的自由晃荡和强迫晃荡做了分析,讨论了液体不同粘性系数对晃荡的影响.模拟结果证明了三维晃荡理论的可行性. 相似文献