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快速多极多域虚边界元法解不同材料组合结构 总被引:1,自引:0,他引:1
将快速多极算法和广义极小残值法(GMRES)的基本思想运用于虚边界元法的方程求解中,并构造了多域组合问题虚边界元法的快速多极展开的实施思路,且将此方法用于不同材料组合结构问题的求解.采用此方法能够使得原问题方程组求解的计算耗时量和储存量降至与所求问题的计算自由度数成线性比例.数值算例验证了方法的可行性、计算精度和计算效率. 相似文献
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不同龄期混凝土组合而成的组合构件截面由于各组合部分徐变系数不同会引起截面应力重分布,从而导致截面内的附加应力.本文引入假想弹性模量的概念,提出了计算徐变引起的应力重分布的附加应力的方法,并通过算例说明考虑这一附加应力的重要性. 相似文献
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The physical aspects of commodity trade are becoming increasingly important on a global scale for transportation planning, demand management for transportation facilities and services, energy use, and environmental concerns. Such aspects (for example, weight and volume) of commodities are vital for logistics industry to allow for medium-to-long term planning at the strategic level and identify commodity flow trends. However, incomplete physical commodity trade databases impede proper analysis of trade flow between various countries. The missing physical values could be due to many reasons such as, (1) non-compliance of reporter countries with the prescribed regulations by World Customs Organization (WCO) (2) confidentiality issues, (3) delays in processing of data, or (4) erroneous reporting. The traditional missing data imputation methods, such as the substitution by mean, substitution by linear interpolation/extrapolation using adjacent points, the substitution by regression, and the substitution by stochastic regression, have been proposed in the context of estimating physical aspects of commodity trade data. However, a major demerit of these single imputation methods is their failure to incorporate uncertainty associated with missing data. The use of computationally complex stochastic methods to improve the accuracy of imputed data has recently become possible with the advancement of computer technology. Therefore, this study proposes a sophisticated data augmentation algorithm in order to impute missing physical commodity trade data. The key advantage of the proposed approach lies in the fact that instead of using a point estimate as the imputed value, it simulates a distribution of missing data through multiple imputations to reflect uncertainty and to maintain variability in the data. This approach also provides the flexibility to include fundamental distributional property of the variables, such as physical quantity, monetary value, price elasticity of demand, price variation, and product differentiation, and their correlations to generate reasonable average estimates of statistical inferences. An overview and limitations of most commonly used data imputation approaches is presented, followed by the theoretical basis and imputation procedure of the proposed approach. Lastly, a case study is presented to demonstrate the merits of the proposed approach in comparison to traditional imputation methods. 相似文献
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Lanshan Han Satish Ukkusuri Kien Doan 《Transportation Research Part B: Methodological》2011,45(10):1749-1767
In this paper we formulate the dynamic user equilibrium problem with an embedded cell transmission model on a network with a single OD pair, multiple parallel paths, multiple user classes with elastic demand. The formulation is based on ideas from complementarity theory. The travel time is estimated based on two methods which have different transportation applications: (1) maximum travel time and (2) average travel time. These travel time functions result in linear and non-linear complementarity formulations respectively. Solution existence and the properties of the formulations are rigorously analyzed. Extensive computational experiments are conducted to demonstrate the benefits of the proposed formulations on various test networks. 相似文献
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影响建筑企业工程项目利润值的主要变量有工程成本、追加价格、创优增量成本。工程成本包括直接费、其他直接费、现场经费、间接费和非生产费用支出;追加价格包括设计变更、施工索赔以及区域内滚动发展的其他项目投资;创优增量成本包括质量、安全、工期、环保、文明施工等增量成本。分别给出成本利润弹性、追加价格利润弹性、创优增量成本利润弹性的理论计算公式。分析提高利润弹性的途径。在工程项目中,目标利润分为正常利润和经济利润,分析工程成本利润弹性、追加价格利润弹性、创优增量成本利润弹性对经济利润的影响。认为事前速度、事中激励、事后评价是提高利润弹性的有效方法。 相似文献
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