全文获取类型
收费全文 | 710篇 |
免费 | 16篇 |
专业分类
公路运输 | 183篇 |
综合类 | 45篇 |
水路运输 | 395篇 |
铁路运输 | 49篇 |
综合运输 | 54篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 10篇 |
2021年 | 26篇 |
2020年 | 27篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 20篇 |
2015年 | 31篇 |
2014年 | 54篇 |
2013年 | 38篇 |
2012年 | 74篇 |
2011年 | 48篇 |
2010年 | 52篇 |
2009年 | 29篇 |
2008年 | 34篇 |
2007年 | 53篇 |
2006年 | 38篇 |
2005年 | 15篇 |
2004年 | 36篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有726条查询结果,搜索用时 171 毫秒
321.
曲轴箱通风系统作为对发动机性能与可靠性有着非常重要影响的核心子系统,随着排放法规日益严苛,发动机性能日益提升,运行工况愈发复杂的情况,对曲轴箱通风系统以及油气分离器的设计提出了更大的挑战。文章通过对车辆出现的故障问题进行详细的分析而找到故障的根本原因,并提出了相应的设计更改方案,并将改进后零件搭载在相关的试验车辆上进行验证,证明了解决措施的有效性。 相似文献
322.
323.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(6):525-548
The directional dynamic analyses of partly-filled tank vehicles have been limited to quasi-static fluid motion due to computational complexities associated with dynamic fluid slosh analyses. The dynamic fluid slosh causes significantly higher magnitudes of slosh forces and moments in the transient state that cannot be characterized through quasi-static approach, which provides reasonably good estimates of the mean responses. In this study, a three-dimensional nonlinear model of a partly-filled cylindrical tank with and without baffles is developed to investigate the significance of resulting destabilizing forces and moments caused by the transient fluid slosh, and the effects of baffles. The baffles and the end caps are modeled with curved shapes. The analyses are performed under varying magnitudes of steady lateral, longitudinal and combinations of lateral and longitudinal accelerations of the tank, and two different fill volumes using the FLUENT software. The results of the study are presented in terms of mean and peak slosh forces and moments, and variations in the mass moments of inertia of the fluid cargo within a clean bore and a baffled tank, for two different fill volumes and different magnitudes of acceleration excitations. The ratios of transient responses to the mean responses, termed as amplification factors, are further described to emphasize the significance of dynamic fluid slosh on the forces and moments induced on the vehicle. The results in general suggest that the mean responses attained from dynamic fluid slosh analyses correlate well with those attained from the quasi-static analyses for a clean bore tank. The amplification ratios of the resulting forces and moments could approach as high as 2. The results clearly show that the presence of baffles helps to suppress the peak as well as mean slosh forces and moments significantly. 相似文献
324.
通过试验对比,机前补气+单催化器净化和闭环电喷+单催化器净化技术方案,尾气排放均较佳,其中,闭环电喷+单催化器净化技术方案,稳定性、可靠性较好,但价格较高,改动较大;机前补气+单催化器净化技术方案,具有相对价格优势,且尾气排放及性能均较好。 相似文献
325.
326.
327.
328.
围绕船舶的能效设计指数(EEDI)和能效运营指数(EEOI)标准的制定和实施,如何降低航行船舶的能耗和废气排放一直是人们关注的热点。基于SHIPFLOW软件模拟船后不同布局的预旋三角导管对阻力、自航因子和各效率的影响,优选出性能较好的布局,并通过水池试验验证。为船舶节能装置的设计和应用提供数值参考。 相似文献
329.
A meshless numerical simulation method, the moving-particle semi-implicit method (MPS) is presented in this paper to study the sloshing phenomenon in ocean and naval engineering. As a meshless method, MPS uses particles to replace the mesh in traditional methods, the governing equations are discretized by virtue of the relationship of particles, and the Poisson equation of pressure is solved by incomplete Cholesky conjugate gradient method (ICCG), the free surface is tracked by the change of numerical density. A numerical experiment of viscous liquid sloshing tank was presented and compared with the result got by the difference method with the VOF, and an additional modification step was added to make the simulation more stable. The results show that the MPS method is suitable for the simulation of viscous liquid sloshing, with the advantage in arranging the particles easily, especially on some complex curved surface. 相似文献
330.