全文获取类型
收费全文 | 718篇 |
免费 | 43篇 |
专业分类
公路运输 | 365篇 |
综合类 | 141篇 |
水路运输 | 127篇 |
铁路运输 | 109篇 |
综合运输 | 19篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 16篇 |
2020年 | 22篇 |
2019年 | 16篇 |
2018年 | 8篇 |
2017年 | 18篇 |
2016年 | 14篇 |
2015年 | 19篇 |
2014年 | 62篇 |
2013年 | 37篇 |
2012年 | 102篇 |
2011年 | 60篇 |
2010年 | 45篇 |
2009年 | 41篇 |
2008年 | 37篇 |
2007年 | 58篇 |
2006年 | 58篇 |
2005年 | 33篇 |
2004年 | 26篇 |
2003年 | 16篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
排序方式: 共有761条查询结果,搜索用时 93 毫秒
491.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(8):1173-1185
A method for detecting wheel slip/slide and re-adhesion control of AC traction motors in railway applications is presented in this paper. This enables a better utilisation of available adhesion and could also reduce wheel wear by reducing high creep values. With this method, the wheel–rail (roller) creepage, creep force and friction coefficient can be indirectly detected and estimated by measuring the voltage, current and speed of the AC traction motor and using an extended Kalman filter. The re-adhesion controller is designed to regulate the motor torque command according to the maximum available adhesion based on the estimated results. Simulations under different friction coefficients are carried out to test the proposed method. 相似文献
492.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(4):497-512
Real-time measurement of tyre–road friction coefficient is extremely valuable for winter road maintenance operations, since knowledge of tyre–road friction coefficient can be used to optimise application of deicing chemicals to the roadway. In this paper, a wheel-based tyre–road friction coefficient measurement system is developed for snowploughs. Unlike a traditional Norse meter, this system is based on measurement of lateral tyre forces, has minimal moving parts and does not use a brake actuator. Hence, it is reliable and inexpensive. A key challenge is quickly detecting changes in the estimated tyre–road friction coefficient while rejecting the high levels of vibratory noise in the measured force signal. Novel filtering and signal processing algorithms are developed to address this challenge, including a biased quadratic mean filter and an accelerometer-based vibration removal filter. Detailed experimental results are presented on the performance of the friction estimation system on different types of road surfaces. It is also shown that disturbances due to lateral and longitudinal vehicle manoeuvres on the estimated friction coefficient can be removed by using accelerometer-based filtering. 相似文献
493.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(12):1658-1680
A number of driver models were fitted to a large data set of human truck driving, from a simulated near-crash, low-friction scenario, yielding two main insights: steering to avoid a collision was best described as an open-loop manoeuvre of predetermined duration, but with situation-adapted amplitude, and subsequent vehicle stabilisation could to a large extent be accounted for by a simple yaw rate nulling control law. These two phenomena, which could be hypothesised to generalise to passenger car driving, were found to determine the ability of four driver models adopted from the literature to fit the human data. Based on the obtained results, it is argued that the concept of internal vehicle models may be less valuable when modelling driver behaviour in non-routine situations such as near-crashes, where behaviour may be better described as direct responses to salient perceptual cues. Some methodological issues in comparing and validating driver models are also discussed. 相似文献
494.
将增强基体组无铜粉氧化与未氧化的两种铁基粉末冶金材料在MM-1000型摩擦材料试验机上进行对比制动试验,测定了摩擦系数与转速、压力的关系曲线及磨损量。结果表明,若加的铅粉发生氧化而真空烧结时不能被还原,则CuO可成为磨粒磨损的磨料,使摩擦材料及对偶的耐磨性降低。 相似文献
495.
分析研究了新高摩合成闸瓦的三元结构体系及对闸瓦理化性能的影响,提出了预防金属镶嵌的措施,并简述了实际装车应用效果及发展方向。 相似文献
496.
以中缅油气管道穿越铁路防护工程为例,分别介绍云南省内管道穿越铁路顶管、框架涵及隧道3种防护形式。由于云南地区地质复杂,结合项目特点,详细对顶管减阻、高水位淤泥质粉质黏土中框架涵顶进及粉细砂地层暗挖隧道防护措施进行了论述;同时对高压油气管道穿越铁路防护工程防火防爆设计进行了介绍。 相似文献
497.
建立超长桩和土体共同作用的三维非线性有限元数值模型,采用预压排水固结法研究软土地基预压后超长桩的承载特性,分析地基土固结沉降、桩身侧摩阻力、桩顶位移-荷载曲线和桩身轴力的变化规律。通过运用控制变量法对预压时间和预压荷载以及不同土质的预压效果进行分析,对比分析单桩与群桩对预压效果的敏感度,并分析固结度对超长桩承载性状的影响。结果表明:预压能较好地改善地基、提高超长群桩的承载能力。增大预压荷载,可增大土体的固结沉降和桩身侧摩阻力;延长预压时间,可提高桩身侧摩阻力,减小桩顶沉降和桩身轴力;预压对群桩的影响好于单桩;固结度越大,超长群桩承载性能越好;对于粉质黏土、黏土以及淤泥质粉质黏土,当预压时间分别达到90 d及180 d时,地基固结基本完成,预压不再改变土的力学指标。 相似文献
498.
499.
500.
基于对深水起重铺管船作业系统设备的设计及应用研究,重点阐述AR绞车的系统组成、结构特点、设计选型及控制系统原理。通过详细分析系统中的牵引绞车、储缆绞车、导向滑轮、补偿装置及PLC控制系统,提出一整套设计思路与方法,解决工程师在系统设计中遇到的诸多问题。 相似文献