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741.
L. F. P. Etman R. C. N. Vermeulen J. G. A. M. Van Heck A. J. G. Schoofs D. H. Van Campen 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,38(2):85-101
Summary A stroke dependent damper is designed for the front axle suspension of a truck. The damper supplies extra damping for inward deflections rising above 4 cm. In this way the damper should reduce extreme suspension deflections without deteriorating the comfort of the truck. But the question is which stroke dependent damping curve yields the best compromise between suspension deflection working space and comfort. Therefore an optimization problem is defined to minimize the maximum inward suspension deflection subject to constraints on the chassis acceleration for three typical road undulations. The optimization problem is solved using sequential linear programming (SLP) and multibody dynamics simulation software. Several optimization runs have been carried out for a small two degree of freedom vehicle model and a large full-scale model of the truck semi-trailer combination. The results show that the stroke dependent damping can reduce large deflections at incidental road disturbances, but that the optimum stroke dependent damping curve is related to the acceleration bound. By means of vehicle model simulation and numerical optimization we have been able to quantify this trade-off between suspension deflection working space and truck comfort. 相似文献
742.
Role of steering wheel feedback on driver performance: driving simulator and modeling analysis 总被引:1,自引:0,他引:1
D. Toffin G. Reymond A. Kemeny J. Droulez 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2007,45(4):375-388
When driving in curves, how do drivers use the force appearing on the steering wheel? As it carries information related to lateral acceleration, this force could be necessary for drivers to tune their internal model of vehicle dynamics; alternatively, being opposed to the drivers' efforts, it could just help them stabilize the steering wheel position. To assess these two hypotheses, we designed an experiment on a motion-based driving simulator. The steering characteristics of the vehicle were modified in the course of driving, unknown to drivers. Results obtained with standard drivers showed a surprisingly wide range of adaptation, except for exaggerated modifications of the steering force feedback. A two-level driver model, combining a preview of vehicle dynamics and a neuromuscular steering control, reproduces these experimental results qualitatively and indicates that adaptation occurs at the haptic level rather than in the internal model of vehicle dynamics. This effect is related to other theories on the manual control of dynamics systems, wherein force feedback characteristics are abstracted at the position control level. This research also illustrates the use of driving simulation for the study of driver behavior and future intelligent steering assistance systems. 相似文献
743.
C. Ruff T. Jost A. Eichberger 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2007,45(10):953-967
The commonly used 'uniform pressure method' (UP) is a well-tried method to simulate an airbag deployment in accident cases. Nevertheless, this method indicates rather heavy inadequacies at the examination of the airbag deployment in the first milliseconds. A solution is the airbag deployment calculation by using computational fluid dynamics (CFD) methods, wherein the calculated gas flow pressure may be applied 'correctly' to the airbag shell elements.
This CFD simulation is integrated in LS-Dyna with the so-called Arbitrary Lagrangian Eulerian (ALE) method and in this review the result's accuracy will be discussed. According to the FMVSS 208, an OoP model will be built-on and comparisons with simulations and tests are done. Another important detail in this labour is the airbag cover examination and the tear seam modelling, as a trivial FE modelling cannot be done due to the very fine mesh. So two possible solutions for tear seam modelling are introduced and discussed. Furthermore considerations concerning the gas generator combustion will also be revealed and an analysis about the impossibility of the direct comparison between gas generator tank test and airbag deployment will be done. At least some parameters, which take effects in the simulation, are researched and evaluated, so finally an optimised simulation model can be made available for further examinations. 相似文献
This CFD simulation is integrated in LS-Dyna with the so-called Arbitrary Lagrangian Eulerian (ALE) method and in this review the result's accuracy will be discussed. According to the FMVSS 208, an OoP model will be built-on and comparisons with simulations and tests are done. Another important detail in this labour is the airbag cover examination and the tear seam modelling, as a trivial FE modelling cannot be done due to the very fine mesh. So two possible solutions for tear seam modelling are introduced and discussed. Furthermore considerations concerning the gas generator combustion will also be revealed and an analysis about the impossibility of the direct comparison between gas generator tank test and airbag deployment will be done. At least some parameters, which take effects in the simulation, are researched and evaluated, so finally an optimised simulation model can be made available for further examinations. 相似文献
744.
We estimate spatial hedonic price functions to examine local and regional accessibility benefits of commuter rail service
in Eastern Massachusetts, while controlling for proximity-related negative externalities and other confounding influences.
The data include 1,860 single-family residential properties from four municipalities with commuter rail service, and three
municipalities without commuter rail service. We find some evidence of the capitalization of accessibility to commuter rail
stations. Two model specifications suggest that properties located in municipalities with commuter rail stations exhibit values
that are between 9.6% and 10.1% higher than properties in municipalities without a commuter rail station. With a third model
we detect weak evidence of the capitalization of auto access time or walking time to the stations, suggesting that properties
located within a one-half mile buffer of a station have values that are 10.1% higher than properties located outside of this
buffer area and that an additional minute of drive time from the station is related to a decrease of 1.6% in property values.
Our results also indicate that proximity to commuter rail right-of-way has a significant negative effect on property values,
which suggests that for every 1,000 ft. in distance from the commuter rail right-of-way, property values are between $732
and $2,897 higher, all else held equal. At the mean sample values, this result translates into an elasticity of between 0.03
and 0.13, depending on the functional form of the hedonic price equation. 相似文献
745.
Recursive least squares with forgetting for online estimation of vehicle mass and road grade: theory and experiments 总被引:2,自引:0,他引:2
A. Vahidi A. Stefanopoulou H. Peng 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2005,43(1):31-55
Good estimates of vehicle mass and road grade are important in automation of heavy duty vehicles, vehicle following manoeuvres or traditional powertrain control schemes. Recursive least square (RLS) with multiple forgetting factors accounts for different rates of change for different parameters and thus, enables simultaneous estimation of the time-varying grade and the piece-wise constant mass. An ad hoc modification of the update law for the gain in the RLS scheme is proposed and used in simulation and experiments. We demonstrate that the proposed scheme estimates mass within 5% of its actual value and tracks grade with good accuracy provided that inputs are persistently exciting. The experimental setups, signals, their source and their accuracy are discussed. Issues like lack of persistent excitations in certain parts of the run or difficulties of parameter tracking during gear shift are explained and suggestions to bypass these problems are made. 相似文献
746.
Luiz A. D. S. Senna 《Transportation》1994,21(2):203-228
Current benefits from travel time savings have only been related to the benefits from reducing mean travel time. Some previous attempts of including variability in the generalised cost function have mainly assumed commuters with fixed arrival time. This paper presents a comprehensive framework for valuing travel time variability that allows for any journey purpose and arrival time constraint. The proposed model is based on the expected utility approach and the mean-standard deviation approach. Stated Preference methods are considered the best technique for providing the data for calibrating the models. The values of time derived from the models are highly influenced by the value of travel time variability and it strongly depends on the probability distribution function travellers are faced with. 相似文献
747.
748.
T. Legouis A. Laneville P. Bourassa G. Payre 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1987,16(5):279-295
This article deals with the simulation of a vehicle/pilot system experiencing external disturbances. In the simulation, the car is modeled with two degrees of freedom and the pilot is assumed to respond to the state vector with a time delay. When perturbations are introduced, the pilot is expected to drive his car back to the initial state while minimizing a quadratic cost function. With some simplifications for low frequencies responses, the model is then used to simulate the response of different vehicles to an initial step in lateral displacement. The results from the simulations are interpreted in the light of the controllability diagrams. 相似文献
749.
Part I of this paper has argued that any meaningful evaluation of transport system safety must include a consideration of the exposure to accidents, and has demonstrated the use and limitations of several measures of exposure at intersections and along links of the network. To complement this treatment of site exposure, this part of the paper will describe the use of group exposure measures in the assessment of risks incurred by people within particular population groupings. The use of induced exposure measures is also briefly reviewed. 相似文献
750.