全文获取类型
收费全文 | 1367篇 |
免费 | 8篇 |
专业分类
公路运输 | 350篇 |
综合类 | 37篇 |
水路运输 | 460篇 |
铁路运输 | 39篇 |
综合运输 | 489篇 |
出版年
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 27篇 |
2017年 | 26篇 |
2016年 | 49篇 |
2015年 | 18篇 |
2014年 | 26篇 |
2013年 | 226篇 |
2012年 | 63篇 |
2011年 | 66篇 |
2010年 | 54篇 |
2009年 | 56篇 |
2008年 | 63篇 |
2007年 | 48篇 |
2006年 | 27篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 26篇 |
2002年 | 20篇 |
2001年 | 29篇 |
2000年 | 19篇 |
1999年 | 24篇 |
1998年 | 44篇 |
1997年 | 20篇 |
1996年 | 23篇 |
1995年 | 23篇 |
1994年 | 17篇 |
1993年 | 18篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 11篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 18篇 |
1974年 | 10篇 |
1973年 | 10篇 |
排序方式: 共有1375条查询结果,搜索用时 46 毫秒
81.
Steven A. Velinsky Robert A. White 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1980,9(6):359-384
Road roughness and surface texture are known to affect tire rolling resistance; however, little emphasis has been placed on the consequent changes in total vehicle energy dissipation due to road roughness. Thus, tire rolling resistance, in isolation from vehicle contributed losses such as dissipation in the suspension, appears to be a weakness in present evaluation procedures as they relate to fuel economy and pollution level testing: Recent work by Funfsinn and Korst has shown that substantial and measurable increases in energy losses occur for vehicles traveling on rough roads. The present investigation uses vehicle axle accelerations as a means of examining various road surfaces. Correlation with computer simulations has allowed the development of a deterministic road roughness model which permits the prediction of energy dissipation in both the tire and suspension as functions of road roughness, tire pressure, and vehicle speed. Comparison to the experiments of Korst and Funfsinn results in good agreement and shows that total rolling loss increases of up to 20 percent compared to ideal smooth roads are possible. The aerodynamic drag coefficient is also found to increase while driving on rough roads. 相似文献
82.
83.
Edward Weiner 《Transportation》1975,4(4):351-367
Taxicab transportation is a significant segment of urban transportation. Taxicabs, along with other “paratransit” type systems, provide service with characteristics between the automobile and mass transportation. Consequently, they are well suited to a number of special purposes. Taxicabs currently serve a wide range of trip purposes by travellers with varied socio-economic characteristics. Taxicab transportation is most attractive for serving lower density area and off-peak travel particularly where there is only minimal mass transit service. In this regard, taxicabs are a supplement to conventional mass transit. The use of taxicabs for collection and distribution functions for both passengers and freight is gradually being realized. The multiple use of taxicabs offers advantages of increasing taxicab productivity and reducing individual trip costs. Many of the problems related to taxicabs are regulatory and institutional in nature. Unless these constraints are eased or removed, wider application of taxicab transportation, including productivity gains, will be limited. 相似文献
84.
Computer simulation models are used in a variety of applications in transportation engineering and have become a prime aid in decision making. The applications range from evaluating traffic control strategies for single intersections to such complex decision processes as evaluating the impact of removing toll facilities at the George Washington Bridge in New York City. While it is widely accepted that simulation offers an unmatchable capability of evaluating alternate control policies, the high variance of the output variable presents a critical problem in such comparative analyses. The simulation models with high output variance must be run longer or replicated many times to achieve a desired precision level, and that corresponds to increased cost of computer resources. This paper describes and illustrates the application of variance reduction concepts that can improve the reliability and efficiency of the simulation experimental process by taking advantage of the simulation model structure. The two variance reduction concepts (common random numbers and antithetic variates) reduce the variance of the output variable by replacing the original sampling procedure with a new procedure that yields the same expected value but with a smaller variance. The application of the variance reduction concept was illustrated using results from experiments with a freeway simulation model. The results indicate that both common random numbers and antithetic variates sampling procedures appreciably reduce the variance of the simulation output measure. 相似文献
85.
This article presents a novel intersection traffic management system for automated vehicles and quantifies its impact on fuel consumption and greenhouse gas emissions of CO2 relative to traditional traffic signal and roundabout intersection control. The developed intelligent traffic management (ITM) techniques, which are based on a spatiotemporal reservation scheme, ensure that vehicles proceed through the intersection without colliding with other vehicles while at the same time reducing the intersection delay and environmental impacts. Specifically, the spatiotemporal reservation scheme provides each vehicle a collision-free path that is decomposed into a speed profile along with navigational instructions. The integration of the developed microscopic traffic simulator with instantaneous emission model, provides improved assessments of the environmental impact of traffic control strategies at intersections. The simulator architecture integrates several ITM algorithms, vehicle sensors, V2V/V2I communications, and emission and fuel consumption models. Each vehicle is modeled by an agent and each agent provides information depending on the specific vehicle sensors. The ITM system is supported by V2V and V2I communications, allowing the exchange of information among vehicles and infrastructure. The data include the estimated vehicle position and speed. Compared with traditional traffic management techniques, the simulation results prove that the proposed ITM system reduces CO2 emissions significantly. The research also shows that these reductions are more significant when the traffic flow increases. 相似文献
86.
87.
Travel time functions specify the relationship between the travel time on a road and the volume of traffic on the road. Until recently, the parameters of travel time functions were rarely estimated in practice; however, a compelling case can be made for the empirical examination of these functions. This paper reviews, and qualitatively evaluates, a range of options for developing a set of travel time functions. A hierarchy of travel time functions is defined based on four levels of network detail: area, corridor, route and link. This hierarchy is illustrated by considering the development of travel time functions for Adelaide. Alternative sources of data for estimating travel time functions are identified. In general, the costs and benefits increase as the travel time functions are estimated at finer levels of network detail. The costs of developing travel time functions include data acquisition costs and analysis costs. The benefits include the potential for reducing prediction errors, the degree of application flexibility and the policy sensitivity of the travel time functions. 相似文献
88.
越来越多的机构开始为交通系统的可持续发展定义,并试图将这一概念融入区域交通规划过程.然而,只有极少数的区域规划机构意识到了交通系统和土地利用变化给经济、环境和社会生活质量(这三者通常被认为是可持续交通系统的三个基本方面)带来的广泛影响.首先,论述了使用多个可持续发展指标的多准则决策方法,并应用其评估亚特兰大大都市区的三... 相似文献
89.
ALEXANDROS A. KARAMANLIDIS PANAYIOTIS DENDRINOS ELENI TOUNTA SPYROS KOTOMATAS 《Coastal management》2013,41(3):293-306
Mediterranean monk seal populations have declined dramatically and survive in subpopulations scattered throughout their original distribution. The National Marine Park of Alonnisos, Northern Sporades is the first marine protected Area dedicated to the protection of the species in the Mediterranean. A Monitoring and Awareness Project has been carried out in the area from 1993 to 2000, the results of which have produced a detailed profile of the human usage pattern of the Park and indicated a significant reduction of illegal activities in the area. The pattern of human usage has enabled the monitoring team to adjust their efforts in the Park over time and provided essential baseline data for future management. The combined monitoring and awareness efforts have contributed significantly to the conservation of the Mediterranean monk seal by successfully protecting pupping sites and reducing human-induced mortality of the species in the area. 相似文献
90.
A. De-Juan R. Sancibrian F. Viadero 《International Journal of Automotive Technology》2012,13(7):1033-1046
This paper presents an approach to optimize planar mechanisms for function generation synthesis. It is applied to the design of different steering linkages used in road vehicles where the Ackermann condition is formulated as the objective function. Four different mechanisms are kinematically defined and synthesized in terms of the proposed method. Limitations of the size of the elements are also considered by means of inequality constraints. Solutions are presented as the difference between desired behaviour, established by Ackermann, and actual generated performance. The results show that the accuracy achieved by the proposed procedure is satisfactory for working conditions in this type of linkages. 相似文献