全文获取类型
| 收费全文 | 263篇 |
| 免费 | 7篇 |
专业分类
| 公路运输 | 152篇 |
| 综合类 | 18篇 |
| 水路运输 | 39篇 |
| 铁路运输 | 21篇 |
| 综合运输 | 40篇 |
出版年
| 2024年 | 12篇 |
| 2023年 | 4篇 |
| 2022年 | 15篇 |
| 2021年 | 16篇 |
| 2020年 | 9篇 |
| 2019年 | 5篇 |
| 2018年 | 9篇 |
| 2017年 | 12篇 |
| 2016年 | 14篇 |
| 2015年 | 12篇 |
| 2014年 | 22篇 |
| 2013年 | 10篇 |
| 2012年 | 14篇 |
| 2011年 | 10篇 |
| 2010年 | 14篇 |
| 2009年 | 8篇 |
| 2008年 | 7篇 |
| 2007年 | 13篇 |
| 2006年 | 8篇 |
| 2005年 | 20篇 |
| 2004年 | 10篇 |
| 2003年 | 9篇 |
| 2002年 | 3篇 |
| 2001年 | 9篇 |
| 2000年 | 2篇 |
| 1999年 | 1篇 |
| 1997年 | 1篇 |
| 1988年 | 1篇 |
排序方式： 共有270条查询结果，搜索用时 15 毫秒
181.
182.
This research presents an integrated optimal controller to maximize the fuel efficiency of a Hybrid Electric Vehicle (HEV) traveling on rolling terrain. The controller optimizes both the vehicle acceleration and the hybrid powertrain operation. It takes advantage of the emerging Connected Vehicle (CV) technology and utilizes present and future information as optimization input, which includes road topography, and dynamic speed limit. The optimal control problem was solved using Pontryagin’s Minimum Principle (PMP). Efforts were made to reduce the computational burden of the optimization process. The evaluation shows that the benefit of the proposed optimal controller is significant compared to regular HEV cruising at the speed limit on rolling terrain. The benefit ranges from 5.0% to 8.9% on mild slopes and from 15.7% to 16.9% on steep slopes. The variation is caused by the change of hilly road density. 相似文献
183.
Various regulations are imposed on shipping to increase energy efficiency and reduce environmental impacts. Alternative fuels and power systems are among the solutions for compliance with these regulations. The power system of a ship may not operate optimally because of the diversity of the operational profile during its lifetime. This article uses an activity-based approach and big data from the Automatic Identification System (AIS) to study the operational profiles of eight ship types operating in Norwegian waters around mainland Norway in 2016. The aim is to identify ship types that can benefit from electric and hybrid propulsion through analysis of their operational profiles. Close to shore, the operational profiles of various ship types are similar, and all ships spend a great proportion of their time with lower loads. As the distance from shore increases, the operational profiles of various ship types follow distinct trends. Among the considered ship types, reefers spend more operational time close to the diesel engine design condition. On the other hand, offshore and passenger ships show the most dynamic operational profiles and spend a large percentage of their operational time with a partial load, away from diesel engine design conditions. Such ships can benefit from hybridisation, diesel-electric propulsion, and other electric concepts, such as batteries and fuel cells. Another option is to downsize diesel engines for better operation while fuel cells and batteries supply peak and partial loads. Operational profiles are plotted and details of the approach are presented in the article. 相似文献
184.
Intelligent decision support systems for the real-time management of landing and take-off operations can be very effective in helping air traffic controllers to limit airport congestion at busy terminal control areas. The key optimization problem to be solved regards the assignment of airport resources to take-off and landing aircraft and the aircraft sequencing on them. The problem can be formulated as a mixed integer linear program. However, since this problem is strongly NP-hard, heuristic algorithms are typically adopted in practice to compute good quality solutions in a short computation time. This paper presents a number of algorithmic improvements implemented in the AGLIBRARY solver (a state-of-the-art optimization solver to deal with complex routing and scheduling problems) in order to improve the possibility of finding good quality solutions quickly. The proposed framework starts from a good initial solution for the aircraft scheduling problem with fixed routes (given the resources to be traversed by each aircraft), computed via a truncated branch-and-bound algorithm. A metaheuristic is then applied to improve the solution by re-routing some aircraft in the terminal control area. New metaheuristics, based on variable neighbourhood search, tabu search and hybrid schemes, are introduced. Computational experiments are performed on an Italian terminal control area under various types of disturbances, including multiple aircraft delays and a temporarily disrupted runway. The metaheuristics achieve solutions of remarkable quality, within a small computation time, compared with a commercial solver and with the previous versions of AGLIBRARY. 相似文献
185.
This paper assesses the demand for a flexible, demand-adaptive transit service, using the Chicago region as an example. We designed and implemented a stated-preference survey in order to (1) identify potential users of flexible transit, and (2) inform the service design of the flexible transit mode. Multinomial logit, mixed-logit, and panel mixed-logit choice models were estimated using the data obtained from the survey. The survey instrument employed a dp-efficient design and the Google Maps API to capture precise origins and destinations in order to create realistic choice scenarios. The stated-preference experiments offered respondents a choice between traditional transit, car, and a hypothetical flexible transit mode. Wait time, access time, travel time, service frequency, cost, and number of transfers varied across the choice scenarios. The choice model results indicate mode-specific values of in-vehicle travel time ranging between $16.3 per hour (car) and $21.1 per hour (flexible transit). The estimated value of walking time to transit is $25.9 per hour. The estimated value of waiting time at one’s point of origin for a flexible transit vehicle is $11.3 per hour; this value is significantly lower than the disutility typically associated with waiting at a transit stop/station indicating that the ‘at-home’ pick-up option of flexible transit is a highly desirable feature. The choice model results also indicate that respondents who use active-transport modes or public transit for their current commute trip, or are bikeshare members, were significantly more likely to choose flexible and traditional transit than car commuters in the choice experiments. The implications of these and other relevant model results for the design and delivery of flexible, technology-enabled services are discussed. 相似文献
186.
加州承载比是评价路基土和路面材料强度及稳定性的重要技术指标,对于路基填筑材料的合理选择具有重要的指导意义。文章通过对内蒙古锡林郭勒盟地区各层矿山废弃土和混合料进行室内CBR试验研究,探讨其强度和水稳性能否满足路基填料的要求,并分析影响CBR的主要因素。研究结果可为矿山废弃土作为路基填料的进一步研究提供参考。 相似文献
187.
While discrete choice analysis is prevalent in capturing consumer preferences and describing their choice behaviors in product design, the traditional choice modeling approach assumes that each individual makes independent decisions, without considering the social impact. However, empirical studies show that choice is social – influenced by many factors beyond engineering performance of a product and consumer attributes. To alleviate this limitation, we propose a new choice modeling framework to capture the dynamic influence from social networks on consumer adoption of new products. By introducing social influence attributes into a choice utility function, social network simulation is integrated with the traditional discrete choice analysis in a three-stage process. Our study shows the need for considering social impact in forecasting new product adoption. Using hybrid electric vehicles as an example, our work illustrates the procedure of social network construction, social influence evaluation, and choice model estimation based on data from the National Household Travel Survey. Our study also demonstrates several interesting findings on the dynamic nature of new technology adoption and how social networks may influence hybrid electric vehicle adoption. 相似文献
188.
The 2005 California Clean Air Access Sticker program offered stickers to owners of hybrid cars allowing unrestricted access to High Occupancy Vehicle lanes. The program was conceived as a zero-cost mechanism to encourage purchase of hybrid cars and to reduce air pollution. Information from sales of used hybrids allows us to estimate sticker market value. We then derive the value of excess HOV space the hybrids occupied, which is considerably greater than the air pollution benefits achieved. A more effective policy would sell space to drivers of any vehicle and use the revenue to stimulate hybrid demand, preferably via direct subsidy. 相似文献
189.
190.