全文获取类型
收费全文 | 690篇 |
免费 | 25篇 |
专业分类
公路运输 | 289篇 |
综合类 | 216篇 |
水路运输 | 118篇 |
铁路运输 | 70篇 |
综合运输 | 22篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 23篇 |
2020年 | 18篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 14篇 |
2016年 | 20篇 |
2015年 | 21篇 |
2014年 | 48篇 |
2013年 | 32篇 |
2012年 | 132篇 |
2011年 | 59篇 |
2010年 | 37篇 |
2009年 | 37篇 |
2008年 | 44篇 |
2007年 | 47篇 |
2006年 | 46篇 |
2005年 | 28篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 16篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 13篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1990年 | 2篇 |
排序方式: 共有715条查询结果,搜索用时 15 毫秒
631.
应用蒸汽驱动的五个由氨-复合吸附剂作制冷工质构成吸附床的制冷空调测试平台,分析循环冷却水进口温度、冷剂的循环量、蒸发温度、加热蒸汽的温度与体积流率变化影响系统供冷量的特点.结果表明,降低循环冷却水进口温度、合理地调控制冷剂流量和提供合适温度和体积流率的蒸汽可提高系统的制冷量和系统运行的稳定性.系统采用电加热锅炉产生蒸汽驱动时,制冷系数(COP)约为0.16,而采用船舶废气锅炉产生蒸汽驱动的COP将可达到1.02. 相似文献
632.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(7):547-568
A set of scaling factors has been introduced by Pacejka [Pacejka, H.B., 2002, Tyre and Vehicle Dynamics (Oxford: Butterworth Heinemann Editions)] into his Magic Formula tyre model to take into account the influence of a number of external overall parameters such as road roughness, weather conditions, suspension characteristics and so on. These scaling factors are important for a correct prediction of tyre–road contact forces, but are not a function of the tyre itself. Changing the point of view, one could say that scaling factors should remain constant for different tyres on the same circuit, with the same weather conditions and with the same car. After characterizing different tyres through indoor tests (that do not consider external overall parameters) and after having identified Pacejka’s coefficients with scaling factors equal to one, several outdoor experimental tests have been carried out to assess the influence of vehicle and road surface conditions on scaling factors. These experimental data allowed us to identify, through a minimization approach, the ‘best’ set of Pacejka’s scaling factors for that vehicle and for that tyre on that track. Scaling factors for equal track and vehicle but different tyres were compared to check whether their values remained constant. To access the validity of scaling factors, a comparison between experimental data, collected on an instrumented passenger car, and MB simulations considering unity and identified scaling factors’ values, were carried out. All experimental data shown in this article come from tests carried out within the VERTEC project, a European founded research project (Task 2.a and 2.b) that puts together knowledge coming from vehicle manufacturers (Volvo, Porsche and Centro Ricerche Fiat CRF), tyre manufacturers (Pirelli and Nokian Tyres), control logic manufacturers (Lucas Varity GmbH), road maintenance experts (Centres d’Études Techniques de l’Équipement CETE), transport research organizations (Transport Research Laboratory TRL, Swedish National Road and Transport Research Institute VTI) and universities (Helsinki University of Technology HUT, Politecnico di Milano and University of Florence UNIFI). 相似文献
633.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(11):1673-1687
A new method to describe tyre rolling kinematics and how to calculate tyre forces and moments is presented. The Lagrange–Euler method is used to calculate the velocity and contact deformation of a tyre structure under large deformation. The calculation of structure deformation is based on the Lagrange method, while the Euler method is used to analyse the deformation and forces in the contact area. The method to predict tyre forces and moments is built using kinematic theory and nonlinear finite element analysis. A detailed analysis of the tyre tangential contact velocity and the relationships between contact forces, contact areas, lateral forces, and yaw and camber angles has been performed for specific tyres. Research on the parametric sensitivity of tyre lateral forces and self-aligning torque on tread stiffness and friction coefficients is carried out in the second part of this paper. 相似文献
634.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(11):1689-1706
There are two aims for the second part of this paper: verifying the theory presented in the first part through parameter variation and comparison between simulation and experiment, and to study the effect of the belt structure on the cornering properties of radial tyres. Research has been carried out with a passenger car radial tyre and two different kinds of truck or bus radial tyres using both simulation and experiment. This second part of the paper shows that belt structure plays an important role in the generation of tyre forces and moments in addition to the effects of the tread stiffness and friction coefficients. The theory and method presented in this paper opens a new robust way to predict the tyre forces and moments from the tyre design and provides a reliable model for a generation mechanism. 相似文献
635.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(4):625-638
Closed-loop control of a snowplow applicator, based on direct measurement of the road surface condition, is a valuable technology for the optimisation of winter road maintenance costs and for the protection of the environment from the negative impacts of excessive usage of de-icing chemicals. To this end, a novel friction measurement wheel is designed to provide a continuous measurement of road friction coefficient, which is, in turn, utilised to control the applicator automatically on a snowplow. It is desired that the automated snowplow applicator deploy de-icing materials right from the beginning of any slippery surface detected by the friction wheel, meaning that no portion of the slippery road surface should be left untreated behind, as the snowplow travels over it at a reasonably high speed. This paper describes the developed wheel-based measurement system, the friction estimation algorithm and the expected performance of the closed-loop applicator system. Conventional and zero velocity applicators are introduced and their hardware time delays are measured in addition to the time delay of the friction estimation algorithm. The overall performance of the closed-loop applicator control system is shown to be reliable at typical snowplowing speeds if the zero velocity applicator is used. 相似文献
636.
研究了由一种废旧塑料再生的有机蜡(ROW)、有机改性剂(OMD)和无机稳定剂(ISD)制备的有机复合温拌剂对沥青的降黏效果及常规性能影响的作用。占沥青结合料4%,OMD含量为30%的有机复合温拌剂可使基质沥青140℃时的布鲁克菲尔德运动黏度与未加温拌剂基质沥青135℃运动黏度相当。该温拌剂还可以使SBS改性沥青在135℃时黏度从2 020mPa.s降到1 450mPa.s,降幅达500~600mPa.s左右。在满足重载交通沥青规范要求前提下,该温拌剂还在一定程度上提高了沥青的软化点和针入度,延度变长,沥青的高低温性能均得到有效改善和提高。为研究和开发高性价比温拌剂开辟了一个新方向。 相似文献
637.
638.
介绍了当前船用焚烧炉技术的现状,以及国内和国外的技术研究情况。通过对不同技术的比较,分析了船用焚烧炉的运行环境,探讨了船用焚烧炉技术的发展趋势。 相似文献
639.
640.