全文获取类型
收费全文 | 2617篇 |
免费 | 197篇 |
专业分类
公路运输 | 925篇 |
综合类 | 677篇 |
水路运输 | 686篇 |
铁路运输 | 450篇 |
综合运输 | 76篇 |
出版年
2024年 | 19篇 |
2023年 | 31篇 |
2022年 | 52篇 |
2021年 | 88篇 |
2020年 | 103篇 |
2019年 | 65篇 |
2018年 | 52篇 |
2017年 | 61篇 |
2016年 | 67篇 |
2015年 | 91篇 |
2014年 | 202篇 |
2013年 | 144篇 |
2012年 | 274篇 |
2011年 | 253篇 |
2010年 | 173篇 |
2009年 | 162篇 |
2008年 | 151篇 |
2007年 | 207篇 |
2006年 | 214篇 |
2005年 | 109篇 |
2004年 | 62篇 |
2003年 | 48篇 |
2002年 | 33篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 17篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
排序方式: 共有2814条查询结果,搜索用时 922 毫秒
691.
针对客运专线隧道如何提高施工进度,制定了相应的管理办法和制度,并将其运用到石太客运专线太行山隧道8号斜井工区的施工管理中,收到了很好的经济效果。 相似文献
692.
在悬架可靠性试验中,通过在其硬点位置安装力传感器,有效控制悬架硬点受力情况,使得悬架系统在台架试验中的受力状态更加真实和全面。该方法对于尚无白车身作为约束系统的悬架可靠性试验尤为有效。 相似文献
693.
以某异形钢塔钢梁斜拉桥为例,对该体系桥的结构受力进行分析评价;针对该桥桥塔的独特造型,应用结构计算软件对其进行总体受力分析.分析结果验证了该桥结构设计的安全性及施工合理性,同时对类似桥型设计中需要注意的地方提出了合理建议. 相似文献
694.
为精确优化系杆拱桥的吊杆内力,提出基于响应面法的系杆拱桥吊杆内力优化方法,优化过程包括试验设计、有限元分析、响应面函数拟合和内力优化。以一跨72m系杆拱桥为例,选取各个吊杆初始内力作为自变量,系梁、拱肋的关键截面弯矩以及系梁关键截面位移和结构应变能作为因变量;采用Box-Behnken试验设计方法进行样本点试验设计,采用显式响应面函数拟合结构静力响应值与吊杆内力间复杂的隐式关系。确定目标函数和多约束条件,采用优化软件对多约束条件下的吊杆内力进行优化分析,给出了成桥在多约束条件下的吊杆最优初内力。研究结果表明:该方法可以很好地对系杆拱桥吊杆初内力进行优化,为系杆拱桥的设计和施工控制提供指导。 相似文献
695.
This article suggests a new methodology for the objective assessment and quantification of the response of a vehicle subjected to transient-handling manoeuvres. For this purpose, a non-dimensional measure is defined, namely the normalized yaw impulse. This measure appears in two variations. In its general or dynamic form, it represents the difference between the yaw moment due to the front-tyre forces and the yaw moment due to the rear-tyre forces, divided by the sum of the aforementioned yaw moments. By employing a linear, two-degree-of-freedom bicycle model, it is shown that the general form of the normalized yaw impulse can be written as a function of the steer angle and the forward, lateral and yaw velocities of the vehicle. This form is referred to as the kinematic yaw impulse. It is demonstrated that the combined application of the dynamic and kinematic expressions of the yaw impulse not only facilitates the explicit assessment and quantification of the transient behaviour of a vehicle, but also reveals the influence of parameters such as the yaw moment of inertia, which traditionally leave the steady-state behaviour unaffected. 相似文献
696.
行人交通仿真模型与相关软件的对比分析 总被引:1,自引:0,他引:1
从描述行人运动行为的尺度和精细程度出发,行人交通仿真模型分为宏观模型、中观模型和微观模型3类。总结了常见的格子气模型、元胞自动机模型、社会力模型和磁力模型的原理及算法,对比分析了其仿真效果。论述了如何运用Legion、STEPS、SimWalk和AnyLogic软件建立行人交通仿真模型,比较和评述了上述软件的技术性能。研究表明,充分、合理利用已有软件,可实现快速有效的行人交通仿真建模。 相似文献
697.
复杂悬跨条件下的管线涡激振动分析(英文) 总被引:1,自引:0,他引:1
Spans occur when a pipeline is laid on a rough undulating seabed or when upheaval buckling occurs due to constrained thermal expansion. This not only results in static and dynamic loads on the flowline at span sections, but also generates vortex induced vibration (VIV), which can lead to fatigue issues. The phenomenon, if not predicted and controlled properly, will negatively affect pipeline integrity, leading to expensive remediation and intervention work. Span analysis can be complicated by: long span lengths, a large number of spans caused by a rough seabed, and multi-span interactions. In addition, the complexity can be more onerous and challenging when soil uncertainty, concrete degradation and unknown residual lay tension are considered in the analysis. This paper describes the latest developments and a .state-of-the-art. finite element analysis program that has been developed to simulate the span response of a flowline under complex boundary and loading conditions. Both VIV and direct wave loading are captured in the analysis and the results are sequentially used for the ultimate limit state (ULS) check and fatigue life calculation. 相似文献
698.
介绍当前高校资金管理中存在的问题,针对相应问题提出对策与建议,从高校内部控制的总体目标和应遵循的原则出发,讨论岗位分工控制、授权批准控制、现金控制、银行存款控制、票据控制、印章控制、日记账控制、监督检查8个方面的高校货币资金内部控制方式。该方式可以降低风险,保护高校货币资金安全和完整。 相似文献
699.
700.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(8):1099-1114
In certification of new rail vehicles with respect to running characteristics, a wide variety of operating conditions needs to be considered. However, in associated test runs the wheel–rail friction condition is difficult to handle because the friction coefficient needs to be fairly high and the friction is also generally hard to assess. This is an issue that has been studied in the European project DynoTRAIN and part of the results is presented in this paper. More specifically, an algorithm for estimating the wheel–rail friction coefficient at vehicle certification tests is proposed. Owing to lack of some measurement results, the algorithm here is evaluated in a simulation environment which is also an important step towards practical implementation. A quality measure of the friction estimate is suggested in terms of estimated wheel–rail spin and total creep. It is concluded that, tentatively, the total creep should exceed 0.006 and the spin should be less than 1.0 m?1 for the algorithm to give a good friction estimate. Sensitivity analysis is carried out to imitate measurement errors, but should be expanded in further work. 相似文献