全文获取类型
收费全文 | 4317篇 |
免费 | 155篇 |
专业分类
公路运输 | 1020篇 |
综合类 | 1506篇 |
水路运输 | 995篇 |
铁路运输 | 755篇 |
综合运输 | 196篇 |
出版年
2024年 | 16篇 |
2023年 | 29篇 |
2022年 | 54篇 |
2021年 | 77篇 |
2020年 | 102篇 |
2019年 | 67篇 |
2018年 | 68篇 |
2017年 | 72篇 |
2016年 | 99篇 |
2015年 | 124篇 |
2014年 | 269篇 |
2013年 | 197篇 |
2012年 | 338篇 |
2011年 | 355篇 |
2010年 | 291篇 |
2009年 | 275篇 |
2008年 | 270篇 |
2007年 | 332篇 |
2006年 | 323篇 |
2005年 | 205篇 |
2004年 | 133篇 |
2003年 | 113篇 |
2002年 | 63篇 |
2001年 | 64篇 |
2000年 | 57篇 |
1999年 | 30篇 |
1998年 | 19篇 |
1997年 | 34篇 |
1996年 | 35篇 |
1995年 | 7篇 |
1994年 | 31篇 |
1993年 | 57篇 |
1992年 | 48篇 |
1991年 | 50篇 |
1990年 | 62篇 |
1989年 | 65篇 |
1988年 | 35篇 |
1987年 | 4篇 |
1984年 | 2篇 |
排序方式: 共有4472条查询结果,搜索用时 15 毫秒
821.
The economic impact of logistics infrastructure: the case of PLAZA – the Zaragoza Logistics Platform
Abstract The economics literature offers many examples of studies of the economic impact of transportation infrastructure such as highways, ports, and airports; however, little attention has been paid to other types of infrastructure such as logistics platforms. This article is a first assessment of the economic effects of the largest logistics platform in Europe – PLAZA, the Zaragoza Logistics Platform – located in Spain. More precisely, this paper analyzes the economic significance of PLAZA on the economy of the Aragon region where it is located. The methodology is based on the application of input–output analysis to the final demand of logistics platform-based companies in a manner that is similar to well-established studies of the economic impacts of tourism on tourist expenditure. This makes it possible to quantify the various levels of economic effects (direct, indirect, and induced) in terms of jobs, salaries, and wages, turnover, gross operating surplus (GOS), and gross value added (GVA). The conclusions reveal the economic importance PLAZA has for the regional economy of Aragon, representing just over 2% of total GVA and 3% of turnover. 相似文献
822.
823.
Avishai Ceder 《先进运输杂志》2013,47(6):595-618
The idea of designing an integrated smart feeder/shuttle service stemmed from the need to overcome the problem of using an excessive number of cars arriving and parking at a train station within the same time span. This problem results in high parking demand around the train station. Moreover, some potential train riders will, instead, use their cars and hence become a party to increasing the traffic congestion. This work develops a new idea of an integrated and innovative feeder/shuttle system with new operating and routing concepts. The fulfilled objectives are as follows: (i) to construct and examine different operating strategies from both the user and operator perspectives; (ii) to examine different routing models and scenarios; and (iii) to construct a simulation tool for (i) and (ii). Ten different routing strategies are examined, with all the combinations of fixed/flexible routes, fixed/flexible schedules, a unidirectional or bidirectional concept, and shortcut (shortest path) and/or short‐turn (turnaround) concepts. These strategies are investigated by employing a simulation model specifically developed and constructed for this purpose. This simulation model is used in a case study of Castro Valley in California in which the feeder/shuttle service is coordinated with the Bay Area Rapid Transit service, and the 10 routing strategies are compared in regard to four fleet‐size scenarios. One of the interesting results found is that the fixed‐route and flexible‐route concepts are comparable in performance measures when applying a combination of operating strategies. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
824.
825.
针对二维平面设计方法难以对悬挂系统各种工况准确分析校核的问题,介绍了通过建立合理的实体模型,运用Pro/ENGINEER软件骨挂模型中参数化设计的特点对悬挂系统进行协调,并进行动态分析,模拟悬挂系统在各种工况下的运动干涉情况的三维设计方法。此方法可提高设计效率,缩短产品开发周期且便于协同设计。 相似文献
826.
827.
828.
829.
Li H.-Q.Fan C.-L. 《铁道工程学报》2014,(9):93-96
Research purposes: Lightning has been one of the important factors endangering safe and reliable operation of the railway. The grounding grid performance plays a particularly important role in lightning protection. In this paper, the author has established a grounding grid transient model by the electromagnetic transient analysis software and intended for quantitative analysis of typically grounding grid layout in engineering practice, to lay important theoretical basis for future lightning protection and grounding. Research conclusions: (1) The results show that the ground potential is significantly affected by the soil resistivity, lightning current amplitude and the mesh size. With increase of the soil resistivity and lightning current amplitude, the ground potential at the point of the lightning current injection will significantly improve, but due to the spark discharge of the soil. The ground potential does not increase exponentially with potential lightning current amplitude. The smaller the mesh size, the better the ground potential attenuation. For example of the lightning current 20 kA and the soil resistivity 100 Ω·m, the ground potential of the 5 m×5 m mesh decreases 22.3% compared with the 10 m×10 m mesh. (2) The study finds that the ground potential attenuation away from the lightning strike point at 15 m basically reaches the maximum, which is about 89%. And the degree of attenuation is independent of lightning current amplitude. (3) The results are mainly used for optimization program and design fields on substation lightning protection and grounding. 相似文献
830.
采用节线法对悬索桥进行初始平衡状态分析,编制 MATLAB 计算程序,计算了实例的缆索线形及其无应力长度等主要参数;同时利用 MIDAS 对程序的计算结果进行了分析对比。最后以 MATLAB 计算结果为边界条件建立 ANSYS 有限元模型,进行结果分析,验证了节线法在进行悬索桥初始平衡状态分析时不很精确的结论。 相似文献