全文获取类型
收费全文 | 519篇 |
免费 | 0篇 |
专业分类
公路运输 | 408篇 |
综合类 | 22篇 |
水路运输 | 62篇 |
铁路运输 | 11篇 |
综合运输 | 16篇 |
出版年
2022年 | 1篇 |
2021年 | 14篇 |
2020年 | 17篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 19篇 |
2013年 | 14篇 |
2012年 | 36篇 |
2011年 | 30篇 |
2010年 | 29篇 |
2009年 | 22篇 |
2008年 | 15篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 25篇 |
2004年 | 26篇 |
2003年 | 21篇 |
2002年 | 22篇 |
2001年 | 19篇 |
2000年 | 31篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 27篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
排序方式: 共有519条查询结果,搜索用时 515 毫秒
61.
62.
63.
凸轮测量的目的不同,对测点间距的要求也不同;为了最大限度地减少测量工作量,把测量误差控制在允许范围之内,必须按公差要求进行凸轮测点布局;在实际测量中,应把计算出的测点间距间的角度值圆整为整数度;无论是用平面测头还是滚柱测头测量,按本文方法算出的测点间距与测量误差的平方根成正比,而与被测点的曲率半径的平方根成反比。 相似文献
64.
65.
66.
This paper shows the results of a comparative fleet test the main objective of which was to measure the influence of Low Viscosity Oils (LVO) over the fuel consumption and CO2 emissions of urban buses. To perform this test, 39 urban buses, classified into candidate and reference groups depending on the engine oil viscosity, covered a 60,000 km mileage corresponding to two rounds of standard Oil Drain Interval (ODI). In the same way, for 9 buses of the 39 buses, the effect of differential LVO over fuel consumption and their interaction with engine LVO was assessed during the second ODI.Test results confirm that the use of LVO could reduce fuel consumption, hence CO2 emissions. However, special attention should be taken prior to its implementation in a fleet, particularly if the vehicles are powered by engines with high mechanical and thermal stresses during vehicle operation because this could lead to friction loss increase, loss of the potential fuel consumption reduction of LVO and, in the worst scenario, higher rates of engine wear. 相似文献
67.
A potential solution to reduce greenhouse gas (GHG) emissions in the transport sector is the use of alternative fuel vehicles (AFV). As global GHG emission standards have been in place for passenger cars for several years, infrastructure modelling for new AFV is an established topic. However, as the regulatory focus shifts towards heavy-duty vehicles (HDV), the market diffusion of AFV-HDV will increase as will planning the relevant AFV infrastructure for HDV. Existing modelling approaches need to be adapted, because the energy demand per individual refill increases significantly for HDV and there are regulatory as well as technical limitations for alternative fuel station (AFS) capacities at the same time. While the current research takes capacity restrictions for single stations into account, capacity limits for locations (i.e. nodes) – the places where refuelling stations are built such as highway entries, exits or intersections – are not yet considered. We extend existing models in this respect and introduce an optimal development for AFS considering (station) location capacity restrictions. The proposed method is applied to a case study of a potential fuel cell heavy-duty vehicle AFS network. We find that the location capacity limit has a major impact on the number of stations required, station utilization and station portfolio variety. 相似文献
68.
船舶机舱监测报警系统是轮机模拟器的重要组成部分,是替代轮机员正确实现对机舱中主、辅机等设备和各系统进行有效巡视管理的主要手段。本系统软件部分以VC++6.0为开发平台设计而成,功能完善、界面友好。文中介绍了该软件的主要功能,并给出了关键部分实现方法及相应代码。 相似文献
69.
船舶机舱自动化监控系统故障自诊断技术研究 总被引:1,自引:0,他引:1
对我国船舶机舱自动化的发展历程进行全面阐述,根据现代船舶机舱自动化的特点来解析我国船舶机舱自动化监控系统存在的主要问题和矛盾.最后,对我国船舶机舱自动化监控系统故障自诊断技术进行全面解析,形成可行的故障自诊断方法.希望通过本文阐述,可以给相关领域研究提供一定思路. 相似文献
70.