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71.
The asymmetric deformation and eccentricity problems of near hemispherical diaphragm under the uniform surface load are quantitatively
characterized in the paper. The analysis is based on a 3D finite element analysis (FEA) model established according to elastic-plasticity
and large displacement nonlinear finite element method. Besides, the deformation experiments are taken to validate the reliability
of FEA model which shows that the simulation results are in good agreement with the experimental results. Then, three angle
parameters, deflection angle β, circumvolving angle θ and distributing angle γ, are introduced and expressed to characterize the asymmetric deformation and eccentricity quantitatively. According to the
angle parameters, the inversion processes of uniform thickness diaphragm and varying thickness diaphragm are calculated respectively.
The inversion process of varying thickness diaphragm is much steadier than that of uniform thickness diaphragm. The present
results show that the asymmetric deformation process can be characterized by curve of three angle parameters (β, θ, γ) exactly, the degrees of eccentricity can be indicated by the final value of deflection angle and the eccentricity position
can be characterized by the final values of the three angle parameters. 相似文献
72.
The performance of vacuum arc remelting (VAR) ingot depends largely on ingot structure and chemical uniformity, which are
strongly influenced by molten pool profile that is influenced by VAR process. To better understand the effect of remelting
current on molten pool profile of titanium alloy ingot during VAR process, a 3D finite element model is developed by the ANSYS
software. The results show that there are three remelting stages during VAR process when the remelting current is 2.0 kA.
The molten pool depth increases gradually from 30 to 320 s, then the change of molten pool depth is very small during the
steady state stage from 320 to 386 s, and lastly the molten pool depth becomes shallow after 386 s. The melting rate and temperature
of superheat increase with the remelting current increasing, which leads to the augment of molten pool volume. In the end,
the total remelting time and steady state molten pool time decrease with the melting current from 1.6 to 2.8 kA. 相似文献
73.
In this paper, the effects of hardening exponent, yield strength and elastic modulus on the deformability of near hemispherical
shells are investigated by means of finite element method and orthogonal experiment design. The largest eccentric angle during
the deformation process and thickness reduction after the deformation are introduced to estimate the deformability quantitatively
according to the deformation characteristics of near hemispherical shells. The results indicate that the hardening exponent
is the most influential parameter, followed by elastic modulus and yield strength. The shell exhibits good deformability when
the hardening exponent and elastic modulus are in the range of 0.1–0.125 and 70–108 GPa, respectively. 相似文献
74.
75.
76.
挤土桩在沉桩过程中,由于挤土效应将引起桩周土体产生较高的超孔隙水压力,随着桩周土体中孔隙水压力的缓慢消散,土体会出现较大的重固结沉降,对周围的建筑物产生不利影响。由于软粘土中挤土桩的重固结沉降包含有几何非线性和材料非线性又涉及三维的渗流固结问题,计算较为复杂。基于ADINA有限元程序和三维Biot固结有限元理论,定义桩周土为多孔介质材料,按照圆柱形空腔体扩张理论来模拟沉桩过程,分析了打桩完成后粘性土超孔隙水压力的消散和桩周土随时间固结沉降情况,得出了一些初步成果。并与软粘土中某挤土桩工程的地表实测沉降结果进行了比较,结果表明,考虑弹塑性本构关系和三维渗流固结的有限元模型能较好地模拟挤土桩重固结沉降过程,为挤土桩的进一步研究奠定基础。 相似文献
77.
某高速公路项目沿线分布大量的高液限土,为解决不良土用于路基填筑的应用问题,通过系统的室内试验研究公路沿线土质的物理力学性质,确定其工程分类;并根据该公路土质的特性,提出填筑改良措施。 相似文献
78.
本文分析了在湖南省高速公路上应用沥青稳定碎石基层应采用的混合料类型和级配范围,提出了基于经济性的简单易行的ATB—25材料组成设计方法——"三指标设计法",并通过试验路进行了验证。 相似文献
79.
80.
针对传统蚁群算法在无人驾驶车辆路径规划中收敛速度慢、易陷入局部最优等问题,提出一种全局路径规划的双向蚁群算法.通过双向搜索策略改进蚁群算法,设计相遇机制求解更多可行路径,提高算法全局搜索能力;引入奖惩因子分别扩大和减小双向搜索后的较优路径和较差路径对信息素浓度的影响,加快求解最优路径的速度;最后在Matlab中模拟无人... 相似文献