全文获取类型
收费全文 | 375篇 |
免费 | 17篇 |
专业分类
公路运输 | 89篇 |
综合类 | 108篇 |
水路运输 | 70篇 |
铁路运输 | 108篇 |
综合运输 | 17篇 |
出版年
2022年 | 3篇 |
2021年 | 17篇 |
2020年 | 14篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 23篇 |
2013年 | 15篇 |
2012年 | 21篇 |
2011年 | 25篇 |
2010年 | 35篇 |
2009年 | 24篇 |
2008年 | 35篇 |
2007年 | 34篇 |
2006年 | 34篇 |
2005年 | 20篇 |
2004年 | 13篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有392条查询结果,搜索用时 343 毫秒
171.
GPSRTK(Real Time Kinematic,RTK)定位技术已经在公路工程测量中得到了较广泛的应用,其便捷的操作、良好的精度、可观的经济效益,已为工程测量界所公认。鉴于此,基于对GPSRTK技术的介绍,阐述了其发展前景,并对其应用现状进行了详细分析。 相似文献
172.
Non-electrification efficiency-improving technologies and powertrain technologies for reducing the heavy-duty truck fuel consumption are studied. The study indicates that improvements in engine efficiency, aerodynamic drag and rolling resistance will benefit fuel economy significantly over the day drive and over-the-road highway driving cycles; 6–13% in fuel savings can be expected from each technology. Hybridization can achieve fuel saving of 16% and is financially attractive for the day drive cycle. Compared to the baseline Class 8 conventional trucks, an improvement of 20–22% and 28–50% in fuel economy by 2020 can be expected using non-electrification efficiency-improving and a combination of non-electrification and hybrid technologies. Fuel economy improvements of a factor of four to five can be achieved by hybridizing the heavy-duty trucks used on ocean ports. 相似文献
173.
钒对高铬锰白口铸铁组织和性能的影响 总被引:1,自引:0,他引:1
谭银元 《武汉船舶职业技术学院学报》2006,5(2):23-24,27
探讨了钒以及热处理工艺对高铬锰白口铸铁组织和性能的影响。结果表明:在高铬锰白口铸铁中加入一定数量的钒,能细化晶粒,改善碳化物的形态和分布,提高力学性能。在含钒量为0.25%~0.5%时,热处理温度为1 000℃时,其力学性能最佳。 相似文献
174.
本文根据多次sct8#泊位靠离泊的操作,总结了如何靠好该泊位的实践经验。特别是在涨末时段,为配合港口生产需要,顺应码头要求右舷顺靠的情况下,如何克服水流的影响达到安全、快捷、顺利靠泊的实践经验,提出控制船位偏前,以船尾顶流入泊的操作方法,引发同行讨论,以期达到获得更多认识,更多经验。其他情况下,不论涨潮落潮,靠离泊受水流影响都比较明显,在按常规方法操作的前提下,确保安全靠离泊。 相似文献
175.
对2块厚度为24mm的Ti-6Al-4VELI厚板进行夹角为171.98°的多层TIG焊接试验,基于SYSWELD软件平台,在焊板两端完全刚性固定的装夹条件下数值模拟计算焊接温度场、应力场和焊接引起的变形.计算结果表明,焊接温度场的变化规律符合实际,焊缝区的拉伸残余应力最大,热影响区的压缩残余应力较大.焊接数值模拟得到的残余应力场与试验测量值能较好地吻合,验证了数值模拟模型的准确性.该数值模拟方法可应用到大深度Ti-6Al-4VELI载人舱强度计算中的焊缝残余应力模拟中. 相似文献
176.
Currently autonomous or self-driving vehicles are at the heart of academia and industry research because of its multi-faceted advantages that includes improved safety, reduced congestion, lower emissions and greater mobility. Software is the key driving factor underpinning autonomy within which planning algorithms that are responsible for mission-critical decision making hold a significant position. While transporting passengers or goods from a given origin to a given destination, motion planning methods incorporate searching for a path to follow, avoiding obstacles and generating the best trajectory that ensures safety, comfort and efficiency. A range of different planning approaches have been proposed in the literature. The purpose of this paper is to review existing approaches and then compare and contrast different methods employed for the motion planning of autonomous on-road driving that consists of (1) finding a path, (2) searching for the safest manoeuvre and (3) determining the most feasible trajectory. Methods developed by researchers in each of these three levels exhibit varying levels of complexity and performance accuracy. This paper presents a critical evaluation of each of these methods, in terms of their advantages/disadvantages, inherent limitations, feasibility, optimality, handling of obstacles and testing operational environments.Based on a critical review of existing methods, research challenges to address current limitations are identified and future research directions are suggested so as to enhance the performance of planning algorithms at all three levels. Some promising areas of future focus have been identified as the use of vehicular communications (V2V and V2I) and the incorporation of transport engineering aspects in order to improve the look-ahead horizon of current sensing technologies that are essential for planning with the aim of reducing the total cost of driverless vehicles. This critical review on planning techniques presented in this paper, along with the associated discussions on their constraints and limitations, seek to assist researchers in accelerating development in the emerging field of autonomous vehicle research. 相似文献
177.
178.
179.
文中提出了一种利用公共无线网络实现AIS、VHF、VTMIS功能的内河船舶管理与信息服务系统的总体架构,对实现原理、终端和服务器系统的设计进行了详细描述,就实现系统功能的关键技术问题进行了初步探讨,并通过天津港小型船舶管理系统的应用进行了实例说明这种系统的应用,将能够实现内河船舶避碰、安全通信、船舶调度和综合信息服务的多种功能,大大降低多种系统并行的建设、维护成本,并可以为内河航运信息化、智能化提供综合应用公用平台 相似文献
180.
本设计采用美国MOTOROLA半导体公司生产的8位微处理器MC68HC908LJ12,以液晶数字显示器的方式,直观显示摩托车行驶过程中的车速、累计里程(km或mile)、环境温度、蓄电池电压等信息,让骑乘者充分享受到现代科技带来的美妙驾驶乐趣。 相似文献