全文获取类型
收费全文 | 1458篇 |
免费 | 76篇 |
专业分类
公路运输 | 425篇 |
综合类 | 501篇 |
水路运输 | 332篇 |
铁路运输 | 230篇 |
综合运输 | 46篇 |
出版年
2024年 | 4篇 |
2023年 | 17篇 |
2022年 | 43篇 |
2021年 | 45篇 |
2020年 | 69篇 |
2019年 | 39篇 |
2018年 | 28篇 |
2017年 | 35篇 |
2016年 | 39篇 |
2015年 | 46篇 |
2014年 | 116篇 |
2013年 | 92篇 |
2012年 | 108篇 |
2011年 | 125篇 |
2010年 | 76篇 |
2009年 | 96篇 |
2008年 | 99篇 |
2007年 | 118篇 |
2006年 | 112篇 |
2005年 | 59篇 |
2004年 | 36篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 14篇 |
2000年 | 20篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
排序方式: 共有1534条查询结果,搜索用时 15 毫秒
91.
A fully three-dimensional, computationally inexpensive vehicular model is presented. In contrast to traditional rigid body models, the vehicle's sprung mass is modeled as a (nonlinearly) deformable body. The formulation of the equations of motion is based on a continuum theory known as the theory of a Cosserat point. These equations largely preserve the relative simplicity of rigid body dynamics but incorporate deformable features. The ease of computer implementation permits the simultaneous simulation of vehicle and collision dynamics of multiple vehicles and highway objects. In this paper, the theory of a Cosserat point is summarized and its general application to vehicle and collision dynamics is illustrated. A three-dimensional collision algorithm is discussed with emphasis on small closing velocities (negligible residual crush, elastic rebound). The novel model is compared to standard procedures. 相似文献
92.
详细分析了变流技术应用试验室试验电源系统的设计方案,阐明了交流调压器与感应调压器配合调压方案的优越性,并给出了实际运行波形。 相似文献
93.
海底管道是海上油气田生产设施的重要组成部分,是保证油气田正常运转的生命线。海底管道在位强度分析对研究其破坏机理及进行安全评估非常重要。基于DNV2000海底管道设计规范和相关文献,根据波浪流等环境参数、管道参数和海床土壤参数之间的关系,并结合相关理论知识,着重阐述了管道在位强度分析的计算原理。最后通过工程实例计算,完成了海底管道结构的在位强度分析及极限状态校核。 相似文献
94.
95.
96.
97.
98.
������ѧϰ����ѵ����������Է��� 总被引:1,自引:0,他引:1
在实际的快速路交通流系统中,入口匝道的流量和快速路主路的速度都是受限的,因此在对快速路交通流进行控制时考虑这些限制十分必要. 基于迭代学习控制的快速路入口匝道控制是近年来快速路控制领域的一个研究热点,然而,至今为止还没有在输入和状态同时受限情况下的相关收敛性分析. 本文首先介绍了快速路交通流模型,并将交通密度控制转化为输出跟踪问题;然后通过严格的数学分析证明了在入口匝道流量受限和主路速度受限的情况下,基于迭代学习控制的入口匝道控制仍然能保证交通流密度收敛于期望密度;最后通过仿真研究验证了该方法在受限情况下能达到很好的控制效果. 相似文献
99.
Shijun YU Yingshun LIU Xiandeng LIANG 《Journal of Transportation Systems Engineering and Information Technology》2011,11(4):91-96
Because of the complex influencing factors, the research on transportation structure usually based on a simple combination of qualitative analysis and ratio-based relation, which lacks of objective quantitative evaluation. The paper applies the information entropy theory to quantitatively study the evolution and development law for regional transportation structure. First, the transport structure information entropy is proposed, and a balanced transportation structure and dominance indicators is proposed to measure the structure and evolution law. Based on that, the main driving-force factors are identified by principal component analysis with combination of gray relational method. The driving-force factors are: total investment in fixed assets, comprehensive factor and population. These may provide evidence for structural optimization of transportation decision-making theory. In the final section, Jiangsu province structural analysis is taken as an example to demonstrate the feasibility of the proposed method. 相似文献
100.
Urban Traffic State Estimation Considering Resident Travel Characteristics and Road Network Capacity
Shunping JIA Hongqin PENG Shuang LIU 《Journal of Transportation Systems Engineering and Information Technology》2011,11(5):81-85
Urban traffic state is usually measured by vehicle average travel speed. It reflects the resident travel behavior on urban road network, and changes with the actual matching status of traffic demand and supply. In this paper, the traffic supply is estimated by the ideal carrying capacity, and the traffic demand is evaluated by vehicle traffic intensity considering resident travel characteristics. In this way, the network carrying capacity and traffic intensity are compared by equative unit. By introducing the intensity/capacity ratio, the matching degree between traffic demand and supply is determined, and the traffic state is identified based on average vehicle speed. In the last section, the 2005 field data of Beijing city is used to test and verify the proposed method. 相似文献