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91.
在应用海洋结构物疲劳寿命预报统一方法时,必须要输入载荷时间历程.在用疲劳寿命预报统一方法设计某个结构时,就需要提供某种标准类型的载荷时间历程.在文献中,标准载荷时间历程或标准载荷谱(均用缩写SLH表示)已经研究了30多年.人们普遍认识到使用SLH有一系列优点,不管是对研究或是应用而言.文章先从现在已经建立的标准载荷时间历程的综述开始,然后详细给出生成标准载荷时间历程或标准载荷谱的步骤,最后提供了一个示范计算的例子. 相似文献
92.
基于美国气垫登陆艇(LCAC)的研制实情及其最近的延寿计划(SLEP)和其未来替代者——舰岸连接器(SSC)的发展趋势,对LCAC的快速性等总体性能进行计算和分析,并追踪LCAC有关新技术在芬兰T-2000艇与韩国LSF-II艇上的应用情况。 相似文献
93.
Liping Zhao Zongchang Liu Jianming Dai Jiuhong Qiang Li Department of Material Science Engineering UIST Baotou Baotou China .Fushun Special Steel Plant Funshun China 《上海交通大学学报(英文版)》2000,(1)
IntroductionSteelingot.steelslabbecomest6elproductsafterheatingandrollingorforging.Steelproductsofforgingneedtobeheattfeatedinheattreatingfumace,fOrexampleannealingnormalization.Heattreatinentcandecreasestress,reducehydrogenconcentrationandimprovetheorganizationandperformanceofsteel.Everyprocessofproductionthatsteelingotschangeilltosteelproductsisaprocessofthermalcycleofsteel.Thisprocesswillconsumealargeamountofeneasmaterialandequipment.Inthepast,inmetallurgicalenterpriseofourcountrythetimeo… 相似文献
94.
Maged Dessouky Mansour Rahimi Merrill Weidner 《Transportation Research Part D: Transport and Environment》2003,8(6):433-465
In certain fleet systems, the environmental impacts of operation are, to some extent, a controllable function of vehicle routing and scheduling decisions. However, little prior work has considered environmental impacts in fleet vehicle routing and scheduling optimization, in particular, where the impacts were assessed systematically utilizing life-cycle impact assessment methodologies such as those described by the Society of Environmental Chemistry and Toxicology. Here a methodology is presented for the joint optimization of cost, service, and life-cycle environmental consequences in vehicle routing and scheduling, which we develop for a demand-responsive (paratransit or dial-a-ride) transit system. We demonstrate through simulation that, as a result of our methodology, it is possible to reduce environmental impacts substantially, while increasing operating costs and service delays only slightly. 相似文献
95.
This paper assesses alternative fuel options for transit buses. We consider the following options for a 40-foot and a 60-foot transit bus: a conventional bus powered by either diesel or a biodiesel blend (B20 or B100), a diesel hybrid-electric bus, a sparking-ignition bus powered by Compressed Natural Gas (CNG) or Liquefied Natural Gas (LNG), and a battery electric bus (BEB) (rapid or slow charging). We estimate life cycle ownership costs (for buses and infrastructure) and environmental externalities caused by greenhouse gases (GHGs) and criteria air pollutants (CAPs) emitted from the life cycle of bus operations. We find that all alternative fuel options lead to higher life cycle ownership and external costs than conventional diesel. When external funding is available to pay for 80% of vehicle purchase expenditures (which is usually the case for U.S. transit agencies), BEBs yield large reductions (17–23%) in terms of ownership and external costs compared to diesel. Furthermore, BEBs’ advantages are robust to changes in operation and economic assumptions when external funding is available. BEBs are able to reduce CAP emissions significantly in Pittsburgh’s hotspot areas, where existing bus fleets contribute to 1% of particulate matter emissions from mobile sources. We recognize that there are still practical barriers for BEBs, e.g. range limits, land to build the charging infrastructure, and coordination with utilities. However, favorable trends such as better battery performance and economics, cleaner electricity grid, improved technology maturity, and accumulated operation experience may favor use of BEBs where feasible. 相似文献
96.
The usage modeling in life cycle assessment (LCA) is rarely discussed despite the magnitude of environmental impact from the usage stage. In this paper, the usage modeling technique, predictive usage mining for life cycle assessment (PUMLCA) algorithm, is proposed as an alternative of the conventional constant rate method. By modeling usage patterns as trend, seasonality, and level from a time series of usage information, predictive LCA can be conducted in a real time horizon, which can provide more accurate estimation of environmental impact. Large-scale sensor data of product operation is suggested as a source of data for the proposed method to mine usage patterns and build a usage model for LCA. The PUMLCA algorithm can provide a similar level of prediction accuracy to the constant rate method when data is constant, and the higher prediction accuracy when data has complex patterns. In order to mine important usage patterns more effectively, a new automatic segmentation algorithm is developed based on change point analysis. The PUMLCA algorithm can also handle missing and abnormal values from large-scale sensor data, identify seasonality, and formulate predictive LCA equations for current and new machines. Finally, the LCA of agricultural machinery demonstrates the proposed approach and highlights its benefits and limitations. 相似文献
97.
The purpose of this paper is to gain a better understanding, through qualitative exploration, of the ways in which social influence affects the decision to start bicycling in England. ‘Social influence’ is defined as the process by which an individual’s thoughts and actions are changed by the thoughts and action of others. Its role was investigated at three levels: the immediate family, household members and significant others (direct social influence); the extended family, friends, peers and colleagues (less direct social influence); and the wider cultural context (indirect social influence). Interviews with 61 individuals living in 12 towns and cities across England were analysed. Half of the interviewees were new regular bicyclists and the other half did not bicycle at all, or only occasionally. Social influence was found to be the dominant factor for a minority of the cases where participants started bicycling regularly. It played a role alongside other factors in other cases. It could take the form of direct influence from family, friends and peers or indirect influence from the social and cultural context. The analysis illustrates the difficulty of capturing social influence which is often hidden and emerges incidentally in the course of the interviews and interacts with other contributing factors. The role of social influence found in this research challenges the rational approach to explaining travel decision making that has traditionally dominated transport studies. The paper suggests that social processes could be harnessed to improve the efficacy of bicycling promotion programs. 相似文献
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