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91.
池洁 《重庆交通学院学报》2006,25(1):117-119
在公路资产的构成中,由于引进了社会资本的投入,不可避免出现公路收费问题.本文针对公路收费问题,分析了公路产品的特点:排他性、非竞争性和外部特征,通过对公路产品外部特征所产生的效益的分析,应用技术经济和动态分析的方法,从理论上讨论了降低公路收费标准存在的合理性和可能性. 相似文献
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A fleet sizing problem (FSP) in a road freight transportation company with heterogeneous fleet and its own technical back‐up facilities is considered in the paper. The mathematical model of the decision problem is formulated in terms of multiple objective mathematical programming based on queuing theory. Technical and economical criteria as well as interests of different stakeholders are taken into account in the problem formulation. The solution procedure is composed of two steps. In the first one a sample of Pareto‐optimal solutions is generated by an original program called MEGROS. In the second step this set is reviewed and evaluated, according to the Decision Maker's (DM's) model of preferences. The evaluation of solutions is carried out with an application of an interactive multiple criteria analysis method, called Light Beam Search (LBS). Finally, the DM selects the most desirable, compromise solution. 相似文献
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随着舰船设计难度和工程复杂程度的增加,现有的舰船规范和标准已无法满足其要求,而型号设计准则则可以解决这一问题。设计准则是型号专用的设计指导性文件,也是质量控制的依据。文章通过分析比较型号设计准则与标准规范间的异同点,提出了建立设计准则框架体系的两个方案,并在此基础上提出了设计准则的工作定位和编制的技术途径;理解型号设计思想;结合关键技术攻关;遴选现有标准规范;统一规划,不断完善。最后,对设计准则的标准化转换工作给予了讨论。 相似文献
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基于不同设想和考虑,澳大利亚、欧洲、中国标准对风荷载的计算是不同的,在工程设计中,设计标准和风的基本参数应该明确,特别是重现期,是用来确定设计风速的基础条件。 相似文献
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Two-stage data envelopment analysis (DEA) models are commonly used in the evaluation and benchmarking of sustainable operations and processes across multiple research fields. To date, however, little attention has been given to the unrealistic weight distribution and weak discrimination power in the modeling and evaluation of the two-stage sustainable operations when using two-stage DEA models. In order to overcome this methodological weakness, we use the multiple criteria DEA (MCDEA) approach in the evaluation of the two-stage processes. The outcome is a multiple criteria two-stage DEA model which yields more realistic weights for the inputs and outputs and thus has better discrimination power than traditional two-stage DEA models. The developed model is tested and validated by assessing the sustainable design performances of a sample of car product designs. 相似文献
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Various methods have been proposed for defining an environmental contour, based on different concepts of exceedance probability. In the inverse first-order reliability method (IFORM) and the direct sampling (DS) method, contours are defined in terms of exceedances within a region bounded by a hyperplane in either standard normal space or the original parameter space, corresponding to marginal exceedance probabilities under rotations of the coordinate system. In contrast, the more recent inverse second-order reliability method (ISORM) and highest density (HD) contours are defined in terms of an isodensity contour of the joint density function in either standard normal space or the original parameter space, where an exceedance is defined to be anywhere outside the contour. Contours defined in terms of the total probability outside the contour are significantly more conservative than contours defined in terms of marginal exceedance probabilities. In this work we study the relationship between the marginal exceedance probability of the maximum value of each variable along an environmental contour and the total probability outside the contour. The marginal exceedance probability of the contour maximum can be orders of magnitude lower than the total exceedance probability of the contour, with the differences increasing with the number of variables. For example, a 50-year ISORM contour for two variables at 3-h time steps, passes through points with marginal return periods of 635 years, and the marginal return periods increase to 10,950 years for contours of four variables. It is shown that the ratios of marginal to total exceedance probabilities for DS contours are similar to those for IFORM contours. However, the marginal exceedance probabilities of the maximum values of each variable along an HD contour are not in fixed relation to the contour exceedance probability, but depend on the shape of the joint density function. Examples are presented to illustrate the impact of the choice of contour on simple structural reliability problems for cases where the use of contours defined in terms of either marginal or total exceedance probabilities may be appropriate. The examples highlight that to choose an appropriate contour method, some understanding about the shape of a structure's failure surface is required. 相似文献