全文获取类型
收费全文 | 1683篇 |
免费 | 78篇 |
专业分类
公路运输 | 292篇 |
综合类 | 649篇 |
水路运输 | 432篇 |
铁路运输 | 296篇 |
综合运输 | 92篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 27篇 |
2021年 | 30篇 |
2020年 | 29篇 |
2019年 | 28篇 |
2018年 | 23篇 |
2017年 | 39篇 |
2016年 | 53篇 |
2015年 | 58篇 |
2014年 | 101篇 |
2013年 | 71篇 |
2012年 | 159篇 |
2011年 | 127篇 |
2010年 | 129篇 |
2009年 | 132篇 |
2008年 | 104篇 |
2007年 | 141篇 |
2006年 | 133篇 |
2005年 | 97篇 |
2004年 | 61篇 |
2003年 | 29篇 |
2002年 | 27篇 |
2001年 | 30篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 4篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1984年 | 3篇 |
排序方式: 共有1761条查询结果,搜索用时 15 毫秒
961.
Smoothed particle hydrodynamics (SPH) is a useful meshless method. The first and second ordersare the most popular derivatives of the field function in the mechanical governing equations. New methodswere proposed to improve accuracy of SPH approximation by the lemma proved. The lemma describes therelationship of functions and their SPH approximation. Finally, the error comparison of SPH method with orwithout our improvement was carried out. 相似文献
962.
海洋平台中管节点的疲劳寿命由焊缝周围热点应力的分布情况决定.该文采用有限元方法分析了承受轴向力作用下T节点焊缝周围的应力分布规律.通过对140个具有不同几何形状的T节点模型的有限元分析结果.提出了一种基于形函数插值理论的方法预测T节点焊缝周围的应力分布,并且通过比较插值法得到的结果和有限元结果进行比较,验证了这种方法的准确性. 相似文献
963.
The asymmetric effects of service quality on international travelers' airline choice behavior were investigated in this paper. The linear structural equation modeling system was first applied to quantify passengers' perceptions of service quality provided by airlines, which were then used as the input variables of the asymmetric response model developed to capture international travelers' airline decision. Their asymmetric responses to various service quality of airlines were assumed to be either gains or losses with respect to their reference points. The results showed that the asymmetric response model performs better than the traditional logit models that capture only symmetrical effects. 相似文献
964.
965.
With regard to the bounded linear continuous-time system, a universal chaotic anti-controlling method was presented on the basis of tracking control. A tracking controller is designed to such an extent that it can track any chaotic reference input, thus making it possible to chaotify the linear system. The controller is identical in structure for different controlled linear systems. Computer simulations proved the effectiveness of the proposed method. 相似文献
966.
黎军 《广东交通职业技术学院学报》2008,7(2):20-22
阐明了线元法的概念及意义,介绍了利用线元法计算公路中线坐标的过程及Gauss-Lgendre公式的计算方法。 相似文献
967.
This paper presents a study on the numerical calculation of the friction resistance coefficient of an infinitely thin plate
as a function of the Reynolds number. Seven eddy-viscosity models have been selected: the one-equation turbulence models of
Menter and Spalart–Allmaras; the k-ω two-equation model proposed by Wilcox and its TNT, BSL and SST variants and the two-equation model. The flow has been computed at 14 Reynolds numbers in sets of seven geometrically similar Cartesian grids
to allow a reliable estimation of the numerical uncertainty. The effect of the computational domain size has been reduced
to negligible levels (below the numerical uncertainty). And the same holds for the iterative and round-off errors. In the
finest grids of each set, the numerical uncertainty of the friction resistance coefficient is always below 1%. Special attention
has further been given to the solution behaviour in the laminar-to-turbulent transition region. Curve fits have been applied
to the data obtained at the 14 Reynolds numbers and the numerical friction lines are compared with four proposals from the
open literature: the 1957 ITTC line, the Schoenherr line and the lines suggested by Grigson and Katsui et al. The differences
between the numerical friction lines obtained with the seven turbulence models are smaller than the differences between the
four lines proposed in the open literature. 相似文献
968.
该文透析了近年来国有企业人才认识误区和人才纷纷流失的原因,以及管理中存在的一些不足;提出了识才、使用人才、培养人才、留住人才的对策;认为创造适宜人才成长的环境,营造促进人才健康成长的管理机制是遏制人才流失,保持企业常胜不衰,立于不败之地的重要手段,是促进人才健康成长,企业取得持续性发展的重要法宝。 相似文献
969.
船舶柴油机转速的线性自抗扰控制 总被引:2,自引:0,他引:2
船舶柴油机推进系统包含非线性、时变参数以及柴油机-推进轴系-螺旋桨之间的强耦合作用,难以建立精确的数学模型,且易受到螺旋桨负载扰动的影响,不利于船舶柴油机转速的实时准确控制。针对此问题,将线性自抗扰控制(Linear Active Disturbance Rejection Control,LADRC)技术应用于船舶柴油机的转速控制系统。首先,基于平均值建模方法建立了某大型低速二冲程船舶柴油机的模型,并分析了转速控制中的不确定因素;然后,针对柴油机的转速控制问题设计了二阶LADRC控制器;最后,以船舶柴油机平均值模型为载体对LADRC的控制性能进行仿真测试,并与经过遗传算法优化的PI控制器进行对比。仿真结果表明,在负载扰动及模型参数改变的情况下LADRC表现出良好的控制性能,并且比PI控制具有更优的扰动抑制能力和鲁棒性。 相似文献
970.