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221.
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沥青路面性能衰减规律的预测模型是进行路面预防性养护管理的重要内容,通过采用经验法预测模型对性能指标IRI、PCI进行分析,来预测路面的使用性能,总结出经验法预测模型的建模程序和使用特点.  相似文献   
223.
The paper develops a forecasting model of emissions from traffic flows embracing the dynamics of driving behavior due to variations in payload. To measure of emissions at the level of individual vehicles under varying payloads a portable emission measurement system is used. This paper reports on a model based on data at the level of individual vehicles for a representative road trajectory. The model aggregates the data to the level of a homogeneous flow dependent of velocity and specific power, which is dependent on payload weight. We find a lean specification for the model that provides emission factors for CO2, NOx, HC, CO, and NO2. The results indicate that, in comparison with earlier models, NOx emissions in particular tend to be underestimated.  相似文献   
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Frequency setting takes place at the strategic and tactical planning stages of public transportation systems. The problem consists in determining the time interval between subsequent vehicles for a given set of lines, taking into account interests of users and operators. The result of this stage is considered as input at the operational level. In general, the problem faced by planners is how to distribute a given fleet of buses among a set of given lines. The corresponding decisions determine the frequency of each line, which impacts directly on the waiting time of the users and operator costs. In this work, we consider frequency setting as the problem of minimizing simultaneously users' total travel time and fleet size, which represents the interest of operators. There is a trade‐off between these two measures; therefore, we face a multi‐objective problem. We extend an existing single‐objective formulation to account explicitly for this trade‐off, and propose a Tabu Search solving method to handle efficiently this multi‐objective variant of the problem. The proposed methodology is then applied to a real medium‐sized problem instance, using data of Puerto Montt, Chile. We consider two data sets corresponding to morning‐peak and off‐peak periods. The results obtained show that the proposed methodology is able to improve the current solution in terms of total travel time and fleet size. In addition, the proposed method is able to efficiently suggest (in computational terms) different trade‐off solutions regarding the conflicting objectives of users and operators. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   
226.
美国Amtrak公司东北走廊在纽约和华盛顿之间的接触网采用单相交流12 kV 25 Hz电流制.沿线有向牵引变电所供电的二相交流138 kV 25 Hz架空输电线.各种供电源又与这根输电线连接.在东北走廊的线路改造中,在费城里士满建造了世界上最大的静止变频装置.这个装置由5组额定容量各为36 MW/45 MVA的相同的变频单元组成,向架空输电线输送180 MW/225 MVA的电能.该装置于2002年7月投入运行.  相似文献   
227.
A summary of the seasonal development of the Northeast Water Polynya ice cover characteristics is presented. This is based primarily on satellite remote sensing observations, with some in situ measurements, including both new and published data.  相似文献   
228.
Historically, human systems integration (HSI) and other operational issues are not addressed during the science and technology (S&T) phase because the focus is on technology development. That view is to solve the "tough science" first, and the rest is simple application by a program office or operational forces. An imbalance between technology development efforts and total system performance considerations, e.g., total ownership cost, workload, manning, training, operational concept, skills, and human performance, leads to suboptimal solutions at best, and at worst prevents the technology's benefits from transitioning out of S&T at all. If HSI is not addressed during the S&T phase, the responsibility falls to the acquisition programs to ensure that operator, maintainer, and total system performance are optimized in the final design. By this point, cost and schedule constraints can make this prohibitive, limiting the options to either using a legacy system or accepting the technology with suboptimal performance and high life-cycle costs (because design problems lead to manpower, training, and human error problems). However, if the S&T community uses HSI in their technology readiness level evaluation criteria, the Department of Defense can reduce its out-year costs and recapitalize that funding to buy required weapons systems and platforms while still reaping the tactical benefits that a new technology offers.  相似文献   
229.
A major component of the US Army's Future Combat Systems (FCS) will be a fleet of eight different manned ground vehicles (MGV). There are promises that "advanced automation" will accomplish many of the tasks formerly performed by soldiers in legacy vehicle systems. However, the current approach to automation design does not relieve the soldier operator of tasks; rather, it changes the role of the soldiers and the work they must do, often in ways unintended and unanticipated. This paper proposes a coherent, top-down, overarching approach to the design of a human–automation interaction model. First, a qualitative model is proposed to drive the functional architecture and human–automation interface scheme for the MGV fleet. Second, the proposed model is applied to a portion of the functional flow of the common crew station on the MGV fleet. Finally, the proposed model is demonstrated quantitatively via a computational task-network modeling program (Improved Performance Research and Integration Tool). The modeling approach offers insights into the impacts on human task-loading, workload, and human performance. Implications for human systems integration domains are discussed, including Manpower and Personnel, Human Factors Engineering, Training, System Safety, and Soldier Survivability. The proposed model gives engineers and scientists a top-down approach to explicitly define and design the interactions between proposed automation schemes and the human crew. Although this paper focuses on the Army's FCS MGV fleet, the model and analytical processes proposed, or similar approaches, are appropriate for many manned systems in multiple domains (aviation, space, maritime, ground transportation, manufacturing, etc.).  相似文献   
230.
Over the past generation seaports have undergone a transformation from traditional cargo handling to logistical support centers and changed from bulk shipping and processing to high value-added management centers in an increasingly competitive global environment. Many have reorganized to become leaders of their region's economic development strategies. This paper reviews these changing roles and their impact on organizational issues. This organizational assessment is applied to the port of Kaohsiung and its envisioned role as a commercial hub and operations centre on the Pacific Rim. Issues such as split lines of responsibility, authority and jurisdiction across different levels of government are considered. Competing goals such as economic development, urban waterfront development, metropolitan urban structure, logistical integration, and infrastructure investment are discussed in this context.  相似文献   
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