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991.
992.
Hongbin Ren Sizhong Chen Gang Liu Lin Yang 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(2):168-190
This paper proposes an improved virtual reference model for semi-active suspension to coordinate the vehicle ride comfort and handling stability. The reference model combines the virtues of sky-hook with ground-hook control logic, and the hybrid coefficient is tuned according to the longitudinal and lateral acceleration so as to improve the vehicle stability especially in high-speed condition. Suspension state observer based on unscented Kalman filter is designed. A sliding mode controller (SMC) is developed to track the states of the reference model. The stability of the SMC strategy is proven by means of Lyapunov function taking into account the nonlinear damper characteristics and sprung mass variation of the vehicle. Finally, the performance of the controller is demonstrated under three typical working conditions: the random road excitation, speed bump road and sharp acceleration and braking. The simulation results indicated that, compared with the traditional passive suspension, the proposed control algorithm can offer a better coordination between vehicle ride comfort and handling stability. This approach provides a viable alternative to costlier active suspension control systems for commercial vehicles. 相似文献
993.
Handheld global positioning system (GPS) devices can serve as a new tool to collect an individual's trip information with advantages of low cost, accurate data, and intensive spatial coverage. Various machine learning algorithms have been explored to detected trip train information in previous studies; however, few of them focused on the evaluation and comparison of the performance and applicability of different models. Meanwhile, according to previous studies, car and bus mode detection is a thorny issue due to their similar travel characteristics, and algorithms still need to be well explored and improved to solve this problem. In this article, an innovative method is proposed to detect trip information, including trip modes, mode-changing time and location, and other attributes, from personal trajectory data. The method is a two-step process. A machine learning algorith-based module (including artificial neural network, support vector machine, random forests, and Bayesian network) is firstly used to identify walk, bicycle, and motorized trip modes (bus or car); we thoroughly compared the performance of these four algorithms. Then a second module, using critical points on the GPS trajectories, is further developed to distinguish car and bus mode, incorporated with GIS map information. Field test results show that the proposed machine learning models can all be applied for walk, bicycle, and motorized mode detection with high detection rates exceeding 90%; however, the algorithms work relatively poorly for bus and car mode detection, with results mostly below 75%. The proposed two-step method can greatly improve bus and car mode detection accuracy by 14–30%. As a result, the average mode detection rates for all the four modes are above 90%. Compared with mode detection results by using only the machine learning algorithm, the proposed two-step method has much better performance in both accuracy and consistency. 相似文献
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995.
我国现行沥青路面设计规范以15℃作为测定沥青混合料疲劳性能的试验温度,忽略了地区之间存在明显的温度差异。根据路面弹性力学层状理论,对控制应力与应变两种疲劳加载模式进行分析,讨论了适用于路面实际疲劳状况的加载模式。分析了影响沥青路面疲劳寿命的因素,并采用SHELL方法,根据Miner法则计算疲劳当量温度,提出了日疲劳当量温度的计算公式,计算了我国8地区的年疲劳当量温度,讨论了不同地区疲劳当量温度的取值范围和取值方法。此研究结果为提高路面结构分析精度提供了可靠的温度参数依据。 相似文献
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997.
潘晓军 《广东交通职业技术学院学报》2008,7(3):65-69
文中从大学英语网络自主学习教学实验易产生的诸多问题出发,以建构主义理论和学习策略理论为基础,就网络自主学习、评估模式、大班教学和网络第二课堂开拓方面对广东工业大学本科二年级学生进行了问卷调查和访谈。根据所发现的问题,广东工业大学针对性改革了教学,实施了新的措施。 相似文献
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A. Harifi A. Aghagolzadeh G. Alizadeh M. Sadeghi 《Transportation Research Part C: Emerging Technologies》2008,16(6):731-741
Antilock brake system (ABS) has been designed to achieve maximum negative acceleration by preventing the wheels from locking. Research shows that the friction between road and tire is a nonlinear function of wheel slip. Therefore, maximum negative acceleration can be achieved by designing a suitable control system for wheel slip regulation at its optimum value. Since there is a lot of nonlinearity and uncertainty (uncertainty in mass and center of gravity of the vehicle and road condition) in vehicle dynamics, a robust control method should be used. In this research, a sliding mode controller for wheel slip control has been designed based on a two-axle vehicle model. Important considered parameters for vehicle dynamic include two separated brake torques for front and rear wheels as well as longitudinal weight transfer caused by the acceleration or deceleration. One of the common problems in sliding mode control is chattering phenomenon. In this paper, primary controller design has been improved using integral switching surface to reduce chattering effects. Simulation results show the success of integral switching surface in elimination of chattering side effects and by high performance of this controller. At the end, the performance of the designed controller has been compared with three of the prevalent papers results to determine the performance of sliding mode control integrated with integral switching surface. 相似文献
1000.