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411.
Coupling a traffic microsimulation with an emission model is a means of assessing fuel consumptions and pollutant emissions at the urban scale. Dealing with congested states requires the efficient capture of traffic dynamics and their conditioning for the emission model. Two emission models are investigated here: COPERT IV and PHEM v11. Emission calculations were performed at road segments over 6 min periods for an area of Paris covering 3 km2. The resulting network fuel consumption (FC) and nitrogen oxide (NOx) emissions are then compared. This article investigates: (i) the sensitivity of COPERT to the mean speed definition, and (ii) how COPERT emission functions can be adapted to cope with vehicle dynamics related to congestion. In addition, emissions are evaluated using detailed traffic output (vehicle trajectories) paired with the instantaneous emission model, PHEM.COPERT emissions are very sensitive to mean speed definition. Using a degraded speed definition leads to an underestimation ranging from −13% to −25% for fuel consumption during congested periods (from −17% to −36% respectively for NOx emissions). Including speed distribution with COPERT leads to higher emissions, especially under congested conditions (+13% for FC and +16% for NOx). Finally, both these implementations are compared to the instantaneous modeling chain results. Performance indicators are introduced to quantify the sensitivity of the coupling to traffic dynamics. Using speed distributions, performance indicators are more or less doubled compared to traditional implementation, but remain lower than when relying on trajectories paired with the PHEM emission model. 相似文献
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《铁道标准设计通讯》2020,(1):215-219
动车运用所室外综合管线是指所内室外各个专业的管沟、管槽、管线、管廊等,其数量种类多、交叉点数量庞大、多专业设计内容又互为边界条件,综合管线设计一直是动车所工程的重难点。传统二维施工图设计具有局限性,协调难度大,容易造成施工阶段管线安装工序不当,进而引发安装空间不足或管线冲突等问题。提出基于BIM的三维正向设计方法,通过研究协同设计、重要基准导入、三维管线综合排布方法、复杂交叉点优化方法、管线碰撞检查和调整方法等,立体直观地展现综合管线的空间排布位置,同时优化三维模型转二维施工图出图方法,合理规划出图内容,确保图纸表达完整,减少设计出错率,指导施工,减少返工和浪费人力物力等现象,为后续复杂段所室外综合管线正向设计提供借鉴。 相似文献
415.
The paper explores what can occur when select street lanes throughout a city are periodically reserved for buses. Simulations of an idealized city were performed to that end. The city’s time-varying travel demand was studied parametrically. In all cases, queues formed throughout the city during a rush, and dissipated during the off-peak period that followed. Bus lanes were activated all at once across the city, and were eventually deactivated in like fashion. Activation and deactivation schedules varied parametrically as well. Schedules that roughly balanced the trip-time savings to bus riders against the added delays to car travelers were thus identified.Findings reveal why activating conversions near the start of a rush can degrade travel, both by car and by bus. Balance was struck by instead activating lane conversions nearer the end of the rush, when vehicle accumulation in the city was at or near its maximum. Most of the time savings to bus riders accrued after the conversions had been left in place for only 30 min. Leaving them for longer durations often brought modest additional savings to bus travelers. Yet, the added delays to cars often grew large as a result.These findings held even when buses garnered high ridership shares. This was the case when lane conversions gradually induced new bus trips among residents who formerly did not travel. It was also true when high ridership was a pre-existing feature of the city. Activating conversions a bit earlier in a rush was found to make sense only if commuters shifted from cars to buses in very large numbers. Findings also unveiled how to fine-tune activation and deactivation schedules to suit a city’s congestion level. Guidelines for scheduling conversions in real settings are furnished. So is discussion on how these schedules might be adapted to daily variations in city-wide traffic states. Roles for technology are discussed as well. 相似文献
416.
根据柴-燃联合动力装置各个部件之间的结构关系及系统热力循环方式,采用模块化建模思想,基于MATLAB/SIMULINK环境,建立了并车控制器、原动机、齿轮箱、离合器、轴系、螺旋桨等部件和系统仿真模型。以船速最优为原则将车钟手柄控制档位划分为十档,即将原动机输出功率由低到高划分为十档,在每个档位下利用系统稳态仿真,通过优化变距桨螺距比的方式,得出最高船速,并以此确定各个档位下的螺旋桨轴转速,获得了基于船-机-桨匹配的柴-燃联合动力装置稳态运行特性,为装置动态控制目标参数的确定提供了依据。 相似文献
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Bruce B. Parker 《Journal of Marine Science and Technology》1996,1(2):75-84
The improved monitoring and modeling capability resulting from recent technological advances in oceanographic sensors, computer
processing power, and telecommunications can play a major role in environmental preservation. In particular, this capability
can help improve: safe navigation and thus the prevention of maritime accidents that lead to hazardous spills; the effective
cleanup of hazardous spills when they do occur; the real-time assessment of water quality problems; the assessment of long-term
trends and variability due to both anthropogenic and climate change effects; and the understanding of key physical, chemical,
and ecological processes.
Presented at the International Conference on Technologies for Marine Environment Preservation (MARIENV’95), Tokyo, Japan,
September 24–29, 1995 相似文献
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高速铁路环境中无线信道传输特性的探讨 总被引:3,自引:0,他引:3
在高速铁路环境下,无线信道的性能发生急剧的变化。针对高速环境下电波传播的特点,阐述了高速铁路中无线信道的特点并对无线信道进行了建模,分析了高速铁路中多普勒频移的特性及对误码率的影响,讨论了隧道传播环境,最后对无线传输的可靠性进行了分析。 相似文献