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221.
Kofi Obeng 《Transportation》1988,15(4):297-316
This paper develops a conceptual framework for bus maintenance based on path analysis and applies it to forty-eight bus transit systems. The application determines the total, direct, and indirect effects of the variables identified as having significant causal links with maintenance cost per mile. These variables are identified using the stepwise regression method. The findings are that the wage rate and fleet size increase maintenance cost directly and indirectly. In terms of the standardized regression coefficients, fleet size has been found to be the most important factor affecting maintenance cost per mile, followed by the proportion of articulated buses, the wage rate and local subsidy in that order. The proportion of articulated buses has been found to reduce maintenance cost per mile directly and to increase it indirectly. The indirect path coefficient of the proportion of articulated buses is 0.1794 whereas the direct path coefficient is –0.351. Similarly local subsidy as a proportion of revenue increases maintenance cost per mile directly and reduces it indirectly. The corresponding path coefficients for the direct and indirect effects of local subsidy are 0.2553 and –0.1073. In addition population density and the peak-base ratio are positively and significantly associated with miles between roadcalls. The implications of these findings are briefly examined in this paper. Because the path analysis methodology allows the direct and indirect effects of a causal variable to be determined, it is recommended for policy analysis. 相似文献
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223.
体外预应力混凝土结构研究现状与展望 总被引:4,自引:0,他引:4
对现阶段体外预应力技术在桥梁工程领域的研究现状进行了总结,并在总结分析的基础上,提出了体外预应力技术研究目前尚需完善的研究领域和方向,包括体外预应力筋应力增量取值、动力特性研究、试验数据收集、设计理论研究、极限强度综合分析系统开发等,为体外预应力技术的进一步研究提供了一定的参考依据。 相似文献
224.
体外预应力加固桥梁正截面强度的计算 总被引:1,自引:1,他引:1
针对体外预应力加固梁时的受力机理和破坏形式,推导出了采用体外预应力加固设计的计算公式和应满足的条件,并应用于川藏公路某大桥的加固实践。该大桥根据本文所论述的原理进行加固后,一直维持了正常的通车和承载力,取得了良好的使用效果。该加固方法施工简单易行,加固效果明显。本文中所建立的体外预应力加固设计计算公式可供同类加固设计参考使用。 相似文献
225.
基于供需平衡的城市路内停车合理规模分析模型 总被引:1,自引:0,他引:1
分析了影响路内停车需求和限制路内停车泊位供应的主要因素,提出了一种确定城市中心区路内停车泊位总体规模的方法:利用城市规模、经济水平等城市宏观指标对路内停车需求进行预测;同时,考虑路网容量,在路网饱和度允许的约束条件下以出行者的广义综合成本最小为目标,从而来确定与路外停车相匹配的路内停车泊位供应规模;然后,比较路内停车需求与路内泊位的供应能力,在尽量满足供需平衡的前提下再考虑管理、周转率等因素。给出建议的路内停车总体规模,为城市中心区的路内停车规划提供依据。文章最后给出实例估算,验证模型的有效性和实用性。 相似文献
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227.
The objective of this paper is to ease the planning of new toll projects by providing estimates of operating costs, and to
help us make better informed decisions about the design of toll collection systems. To do so we use panel data for Norwegian
toll companies to estimate average cost functions. The main results can be summarised as follows. We provide evidence of very
important unexploited economies of scale. The estimated cost curves are very steep for traffic levels below the sample mean,
and become almost entirely flat over a wide range above the sample mean. A higher share of vehicles using on board units will
significantly reduce average costs. Competitive tendering will significantly reduce average operating costs by as much as
25%. Our results also suggest that increased number of lanes, higher debt and passenger charging will increase average operating
costs whereas average operating costs are lower for toll cordons compared with other projects.
相似文献
Morten WeldeEmail: |
228.
The present study investigates the collapse performance of composite-repaired cylinders with internal metal loss subjected to external pressure. Three groups of intact, thinned, and repaired cylinders were designed, analytically verified, fabricated, geometrically measured, externally tested, and numerically modeled. Each group had three nominally identical cylinders to ensure the repeatability of experiments. The cylinders had the same end closure, effective length, total length, external radius, and intact thickness for an equivalent comparison. The thinned cylinder was considered as the intact cylinder with internal metal loss, whereas the repaired cylinder was considered as the thinned cylinder with composite reinforcement. The results indicated that the external loading capacity of cylinders with internal metal loss could be fully restored and even enhanced by composite reinforcement. Composite-repaired cylinders are much less sensitive to initial geometrical imperfections than intact cylinders. 相似文献