全文获取类型
收费全文 | 654篇 |
免费 | 3篇 |
专业分类
公路运输 | 233篇 |
综合类 | 21篇 |
水路运输 | 213篇 |
铁路运输 | 23篇 |
综合运输 | 167篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 27篇 |
2015年 | 9篇 |
2014年 | 27篇 |
2013年 | 94篇 |
2012年 | 34篇 |
2011年 | 34篇 |
2010年 | 39篇 |
2009年 | 33篇 |
2008年 | 26篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 14篇 |
1997年 | 7篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 11篇 |
1980年 | 3篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 8篇 |
排序方式: 共有657条查询结果,搜索用时 15 毫秒
111.
Understanding Accessibility and Road Capacity Changes: A Response in Support of Metz 总被引:1,自引:0,他引:1
Robert B. Noland 《运输评论》2013,33(6):698-706
112.
Urea-SCR system optimization with various combinations of mixer types and decomposition pipe lengths
Y. S. Cho S. W. Lee W. C. Choi Y. B. Yoon 《International Journal of Automotive Technology》2014,15(5):723-731
The demand for NOx after-treatment system has increased dramatically due to the stricter NOx emission regulations for diesel vehicles. The urea-SCR system is one of the NOx after-treatment methods found to be quite effective to meet the regulation requirement enforced by various authorities including the Euro-6. In order to develop an effective urea-SCR system, it is critical to establish an even distribution of reductant over the catalyst surface since this favorable distribution can increase reduction reaction and in turn, improve NOx conversion efficiencies. In the current study, a number of design variations of the urea-SCR system which included two mixer types and three decomposition pipe lengths, were evaluated systematically using CFD analysis and experimental measurements. The purpose of the CFD analysis was to estimate the distribution of reductant within the urea-SCR system with a specific configuration and the purpose of the engine emission test was to measure the amount of NOx reduction, respectively. The results from the systematic analysis revealed the relation between the reductant distribution over the SCR and the performance of the NOx reduction. 相似文献
113.
A. Gauchía E. Olmeda M. J. L. Boada B. L. Boada V. Díaz 《International Journal of Automotive Technology》2014,15(3):451-461
Engineering bus design requires testing of bus structures prototypes in order to guarantee a certain level of strength and an appropriate static and dynamic behavior of the bus superstructure when exposed to road loads. However, experimental testing of real bus structures is very expensive as it requires expensive resources and space. If testing is done on a scale bus model the previous required expenses are considerably reduced. Therefore, a novel methodology based on dimensional analysis applied to bus structure prediction to evaluate the bus structure static and dynamic performance is proposed. The static performance is evaluated attending to torsion stiffness and the dynamic in terms of the natural vibration frequencies and rollover threshold. A scale bus has been manufactured and dimensionless parameters have been defined in order to project the results obtained in the scale bus model to a larger model. Validation of the proposed methodology has been carried out under experimental and finite element analysis. 相似文献
114.
A fuzzy stochastic approach to the multicriteria selection of an aircraft for regional chartering 下载免费PDF全文
Luiz Flavio Autran Monteiro Gomes Joao Erick de Mattos Fernandes João Carlos C. B. Soares de Mello 《先进运输杂志》2014,48(3):223-237
This article deals with the problem of decision support for the selection of an aircraft. This is a problem faced by an airline company that is investing in regional charter flights in Brazil. The company belongs to an economic group whose core business is logistics. The problem has eight alternatives to be evaluated under 11 different criteria, whose measurements can be exact, stochastic, or fuzzy. The technique chosen for analyzing and then finding a solution to the problem is the multicriteria decision aiding method named NAIADE (Novel Approach to Imprecise Assessment and Decision Environments). The method used allows tackling the problems by working with quantitative as well as qualitative criteria under uncertainty and imprecision. Another considerable advantage of NAIADE over other multicriteria methods relies in its characteristics of not requiring a prior definition of the weights by the decision maker. As a conclusion, it can be said that the use of NAIADE provided for consistent results to that aircraft selection problem. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
115.
Bicycle usage can be affected by colder weather, precipitation, and excessive heat. The research presented here analyzes the effect of weather on the use of the Washington, DC, bikeshare system, exploiting a dataset of all trips made on the system. Hourly weather data, including temperature, rainfall, snow, wind, fog, and humidity levels are linked to hourly usage data. Statistical models linking both number of users and duration of use are estimated. Further, we evaluate trips from bikeshare stations within one quarter mile of Metro (subway) stations at times when Metro is operating. This allows us to determine whether Metro serves as a back-up option when weather conditions are unfavorable for bicycling. Results show that cold temperatures, rain, and high humidity levels reduce both the likelihood of using bikeshare and the duration of trips. Trips taken from bikeshare stations proximate to Metro stations are affected more by rain than trips not proximate to Metro stations and less likely when it is dark. This information is useful for understanding bicycling behavior and also for those planning bikeshare systems in other cities. 相似文献
116.
117.
Fuel economy comparison of conventional drive trains series and parallel hybrid electric step vans 总被引:1,自引:0,他引:1
S. B. Han Y. H. Chang Y. J. Chung E. Y. Lee B. Suh A. Frank 《International Journal of Automotive Technology》2009,10(2):235-240
A hybrid electric vehicle (HEV) is a vehicle that combines a conventional propulsion system with an on-board rechargeable
energy storage system to achieve better fuel economy than a conventional vehicle HEVs do not have limited ranges like battery
electric vehicles, which use batteries charged by an external source. The different propulsion power systems may have common
subsystems or components. The objective of this study is to compare the fuel economies of a conventional step van, a series
hybrid electric step van (HESV), and a parallel HESV by calculating the fuel consumption using the ADVISOR software by NREL.
We also showed the results of the vehicles in different driving cycles including the Central Business District bus cycles,
the New York City Cycle, and the US EPA City and Highway cycles. 相似文献
118.
Analysis of a regenerative braking system for Hybrid Electric Vehicles using an Electro-Mechanical Brake 总被引:3,自引:0,他引:3
J. K. Ahn K. H. Jung D. H. Kim H. B. Jin H. S. Kim S. H. Hwang 《International Journal of Automotive Technology》2009,10(2):229-234
The regenerative braking system of the Hybrid Electric Vehicle (HEV) is a key technology that can improve fuel efficiency
by 20∼50%, depending on motor size. In the regenerative braking system, the electronically controlled brake subsystem that
directs the braking forces into four wheels independently is indispensable. This technology is currently found in the Electronic
Stability Program (ESP) and in Vehicle Dynamic Control (VDC). As braking technologies progress toward brake-by-wire systems,
the development of Electro-Mechanical Brake (EMB) systems will be very important in the improvement of both fuel consumption
and vehicle safety. This paper investigates the modeling and simulation of EMB systems for HEVs. The HEV powertrain was modeled
to include the internal combustion engine, electric motor, battery and transmission. The performance simulation for the regenerative
braking system of the HEV was performed using MATLAB/Simulink. The control performance of the EMB system was evaluated via
the simulation of the regenerative braking of the HEV during various driving conditions. 相似文献
119.
W. B. Hou H. Z. Zhang R. F. Chi P. Hu 《International Journal of Automotive Technology》2009,10(2):175-180
The concept design phase is a critical step in auto-body design, as it has a great effect on later design work. This paper
describes the implementation of an auto-body structure design in the early stages of a new auto-body developing program. In
order to reduce the long design period and analysis error that plagues traditional auto-body concept design, an intelligent
CAE system has been successfully developed and implemented based on the UGS NX/API opening platform. This system, the so-called
ACD-ICAE (Auto-body concept design-intelligent computer aided engineering) System that means concept design-intelligent computer
aided engineering system, employs a fully parametrized template method to build the conceptual auto-body geometry model and
FEM model quickly and easily. It also integrates auto-body modeling, analysis and optimization on only one CAD platform via
a parametric variables database. Moreover, all parametric variables are shared and updated in different phases of the ACD-ICAE
System. A wizard User Interface (UI) based on knowledge of auto-body engineering was developed and used in this system. The
procedures implementing the functional diagram of the ACD-ICAE system are also provided. A typical example of a car body concept
design with four doors shows that the ACD-ICAE system is efficient and accurate. 相似文献
120.
THAMANAM Srinivasa Rao NAGARAJA Potti NAIK B Balaji MANJUNATHACHARI K 《上海交通大学学报(英文版)》2021,26(4):488-493
Data security plays a vital role in the current scenario due to the advanced and sophisticated data access techniques.Present development in data access is alwa... 相似文献