全文获取类型
收费全文 | 1330篇 |
免费 | 112篇 |
专业分类
公路运输 | 387篇 |
综合类 | 372篇 |
水路运输 | 456篇 |
铁路运输 | 170篇 |
综合运输 | 57篇 |
出版年
2024年 | 10篇 |
2023年 | 12篇 |
2022年 | 13篇 |
2021年 | 32篇 |
2020年 | 42篇 |
2019年 | 37篇 |
2018年 | 39篇 |
2017年 | 46篇 |
2016年 | 40篇 |
2015年 | 48篇 |
2014年 | 116篇 |
2013年 | 80篇 |
2012年 | 82篇 |
2011年 | 126篇 |
2010年 | 99篇 |
2009年 | 73篇 |
2008年 | 87篇 |
2007年 | 105篇 |
2006年 | 103篇 |
2005年 | 79篇 |
2004年 | 43篇 |
2003年 | 29篇 |
2002年 | 24篇 |
2001年 | 23篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有1442条查询结果,搜索用时 375 毫秒
901.
Xuewu Ji Xiangkun He Chen Lv Jian Wu 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(6):923-946
Modelling uncertainty, parameter variation and unknown external disturbance are the major concerns in the development of an advanced controller for vehicle stability at the limits of handling. Sliding mode control (SMC) method has proved to be robust against parameter variation and unknown external disturbance with satisfactory tracking performance. But modelling uncertainty, such as errors caused in model simplification, is inevitable in model-based controller design, resulting in lowered control quality. The adaptive radial basis function network (ARBFN) can effectively improve the control performance against large system uncertainty by learning to approximate arbitrary nonlinear functions and ensure the global asymptotic stability of the closed-loop system. In this paper, a novel vehicle dynamics stability control strategy is proposed using the adaptive radial basis function network sliding mode control (ARBFN-SMC) to learn system uncertainty and eliminate its adverse effects. This strategy adopts a hierarchical control structure which consists of reference model layer, yaw moment control layer, braking torque allocation layer and executive layer. Co-simulation using MATLAB/Simulink and AMESim is conducted on a verified 15-DOF nonlinear vehicle system model with the integrated-electro-hydraulic brake system (I-EHB) actuator in a Sine With Dwell manoeuvre. The simulation results show that ARBFN-SMC scheme exhibits superior stability and tracking performance in different running conditions compared with SMC scheme. 相似文献
902.
基于“状态修”的概念,通过在线监测,选择并联电机的电流与电势差作比较,用模糊判别的方法,确定机车运行中的故障电机。根据故障记录,有针对性地维修电机,从而实现牵引电动机的状态修。 相似文献
903.
夏良云 《江苏科技大学学报(社会科学版)》2007,21(4):37-41
在局部凸拓扑向量空间中,建立了弧连通凸映射向量优化问题关于基的Henig真有效解的标量化定理、Kuhn-Tucker条件、对偶性定理以及鞍点定理。 相似文献
904.
905.
Application of a genetic algorithm to the optimal structural design of a ship's engine room taking dynamic constraints into consideration 总被引:4,自引:0,他引:4
Mitsuru Kitamura Hisashi Nobukawa Fengxiang Yang 《Journal of Marine Science and Technology》2000,5(3):131-146
The genetic algorithm, known as GA, is used to optimize engine room structure, not only under static constraints, but also
under dynamic constraints. A penalty function method is used to handle the complicated constraint conditions based on the
numerical results of dynamic and static analyses. There are several ways to take the dynamic effect into account in the optimum
design of ship structure. First, the inequality constraint condition is applied to separate the natural frequency and the
exciting frequency. Second, generalized design variables are introduced in order to transfer not only the dynamic but also
the static equilibrium equations into the equality constraints, resulting in the optimal structural design without the need
to solve these equilibrium equations. Third, the magnitudes of the acceleration and displacement are constrained instead of
applying the natural frequency constraint condition. In order to achieve better convergency in the optimization with least
resources, several operators and methods are considered and then introduced into the structural design of the engine room.
The new operator, called either objective elitism or fitness elitism, is introduced to improve the efficiency of the method.
The effect of boundary mutation and nonuniform mutation on the performance of the GA is examined. Not only binary representation
but also floating-point representation are used to express the design gene in the GA. Fuzzy theory is applied in the GA to
handle the uncertainty of the constraint conditions. Two ways of solving fuzzy optimization are investigated in order to obtain
a fuzzy solution and a crisp solution.
Received: October 2, 2000 / Accepted: November 30, 2000 相似文献
906.
将进气迟闭角调整到最佳,可以使得在一个行程内进更多的气,在改善柴油机的进气性能的同时,提高柴油机的整体性能.通过在4110柴油机上实验,获得所需要加载的边界条件,利用CFD软件FLUENT建立模型,并模拟进气过程,得到进气迟闭角对充气效率的影响关系. 相似文献
907.
将一种由典型的方尾流动物理模型(水流沿方尾下缘切向脱体)导出的数值方尾边界条件应用于高速多体船兴波问题计算。兴波波形与兴波阻力的数值计算采用基于非均匀有理B样条的广义高阶面元法,所得到的高速双体船算例与高速三体船算例的计算结果合理。 相似文献
908.
采用欧洲的瞬态排放标准来评价中国的汽车瞬态排放具有局限性,在天津大学和北京工商大学实验数据的基础上,对195s简易瞬态工况进行了改进。 相似文献
909.
林炳龙 《铁路通信信号工程技术》2014,(4):75-77
从4个方面阐述《联锁表》之敌对信号设计方法,总结敌对信号的设计规律,以及对敌对信号条件的描述均具独到的见解,对如何编制《联锁表》、提高《联锁表》设计质量具有很大的参考意义。 相似文献
910.
Complex Shifted Morlet Wavelets (CSMW) present a number of advantages, since the concept of shifting the Morlet wavelet in the frequency domain allow the simultaneous optimal selection of both the wavelet center frequency and the wavelet bandwidth. According to the proposed method, a cluster of CSMW wavelets is used, covering appropriate ranges in the frequency domain. Then, instead of directly processing the instantaneous frequency of each CSMW, an invariance approach is used to indirectly recover the individual harmonic components of the signal. This invariance approach is based actually on the same rotational approach, using the same matrix properties, which consists the core of the well known ESPRIT algorithm. Moreover, the DESFRI (DEtection of Source Frequencies via Rotational Invariance) approach is introduced to support the proposed CSMW method to semi-automated selection of the center frequency of the applied Morlet window. This approach is based on the singular values that are extracted as an intermediate product of the proposed decomposition process. By the application of the method in a multi-component synthetic signal a way to select the critical parameters of the Morlet wavelet, is investigated. The method is further tested on a time-varying acoustic Doppler signal generated by a passing railway vehicle, indicating promising results for the estimation of the variable instantaneous frequency and the multi-component decomposition of it. 相似文献