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81.
K. M. Saqr M. K. Mansour M. N. Musa 《International Journal of Automotive Technology》2008,9(2):155-160
The potential for thermoelectric power generation (via waste heat recovery onboard automobiles) to displace alternators and/or
provide additional charging to a vehicle battery pack has increased with recent advances in thermoelectric material processing.
In gasoline fueled vehicles (GFVs), about 40% of fuel energy is wasted in exhaust heat, while a smaller amount of energy (30%)
is ejected through the engine coolant. Therefore, exhaust-based thermoelectric generators (ETEG) have been a focus for GFV
applications since the late 1980s. The conversion efficiency of modern thermoelectric materials has increased more than three-fold
in the last two decades; however, disputes as to the thermal design of ETEG systems has kept their overall efficiency at limited
and insufficient values. There are many challenges in the thermal design of ETEG systems, such as increasing the efficiency
of the heat exchangers (hot box and cold plate), maintaining a sufficient temperature difference across the thermoelectric
modules during different operating conditions, and reducing thermal losses through the system as a whole. This paper focuses
on a review of the main aspects of thermal design of ETEG systems through various investigations performed over the past twenty
years. This paper is organized as follows: first, the construction of a typical ETEG is described. The heat balance and efficiency
of ETEG are then discussed. Then, the third section of this paper emphasizes the main objectives and challenges for designing
efficient ETEG systems. Finally, a review of ETEG research activities over the last twenty years is presented to focus on
methods used by the research community to address such challenges. 相似文献
82.
Low viscosity engine oil can improve a vehicle’s fuel economy by decreasing the friction between the engine components. Frictional
torque varies with the velocity change due to different viscosity characteristics of SAE grade 5W-20, 5W-30 and 5W-40 engine
oils. The viscosity for each of these grades was measured to outline the effect low viscosity engine oils have on engine friction,
which may lead to improved fuel economy. Engine oil seal frictional torque increases with the shaft rotational speed for all
three engine oil grades. A decrease in engine oil seal frictional torque was confirmed when low viscosity engine oil was used.
Also, the leak-free performance of the engine oil with the seal satisfied the life limit durability test criteria. Thus, low
viscosity engine oil may be used to improve fuel economy by decreasing the frictional loss of the engine oil seal while having
no negative impact on performance due to leak-free functioning. 相似文献
83.
Desired yaw rate and steering control method during cornering for a six-wheeled vehicle 总被引:1,自引:0,他引:1
S. -J. An K. Yi G. Jung K. I. Lee Y. -W. Kim 《International Journal of Automotive Technology》2008,9(2):173-181
This paper proposes a steering control method based on optimal control theory to improve the maneuverability of a six-wheeled
vehicle during cornering. The six-wheeled vehicle is believed to have better performance than a four-wheeled vehicle in terms
of its capability for crossing obstacles, off-road maneuvering and fail-safe handling when one or two of the tires are punctured.
Although many methods to improve the four-wheeled vehicle’s lateral stability have been studied and developed, there have
only been a few studies on the six-wheeled vehicle’s lateral stability. Some studies of the six-wheeled vehicle have been
reported recently, but they are related to the desired yaw rate of a four-wheeled vehicle to control the six-wheeled vehicle’s
maneuvering during corning. In this paper, the sideslip angle and yaw rate are controlled to improve the maneuverability during
cornering by independent control of the steering angles of the six wheels. The desired yaw rate that is suitable for a six-wheeled
vehicle is proposed as a control target. In addition, a scaled-down vehicle with six drive motors and six steering motors
that can be controlled independently is designed. The performance of the proposed control methods is verified using a full
model vehicle simulation and scaled-down vehicle experiment. 相似文献
84.
This paper is the second invstigation on the effect of fuel stratification on flame propagation. In the previous work, the
characteristics under the no port-generated swirl condition, i.e., the conventional case was studied. In this work, the flame
development under the low swirl condition was considered. For this purpose, the initial flame development and propagation
were visualized under different axially stratified states in a modified optical single cylinder SI engine. The images were
captured by an intensified CCD camera through the quartz window mounted in the piston. Stratification was controlled by the
combination of the port swirl ratio and injection timing. These were averaged and processed to characterize the flame propagation.
The flame stability was estimated by the weighted average of flame area and luminosity. The stability was also evaluated through
the standard deviation of flame area and propagation distance and through the mean absolute deviation of the propagating direction.
The results show that the flame-flow interaction determines the direction of flame propagation and that the governing roles
of the two factors vary according to the stratified state and the location in the cylinder. In addition, the flame development
and the initial flame stability are strongly dependent on the stratified conditions, and the initial flame stability is closely
related to the engine stability and lean misfire limit. Lastly, there is no essential difference in gasoline and CNG flame
propagation characteristics. 相似文献
85.
The recursive component mode synthesis method (RCMS) has been implemented for the finite element analysis model of an automobile
structure as an efficient free vibration analysis tool. The RCMS method is intended to obtain a better performance relative
to the block Lanczos method, which is a traditional method in the industry of obtaining eigenvalues, while obtaining the acceptable
accuracy. A numerical example of the automobile finite element model demonstrates the outstanding performance of RCMS compared
to the block Lanczos method. 相似文献
86.
Konstantinos G. Zografos Konstantinos N. Androutsopoulos Teemu Sihvola 《Transportation》2008,35(6):777-795
Flexible transport services include a wide range of demand responsive transport systems that provide non-conventional passenger
and freight transportation services. Several alternative business models varying according to the local market conditions,
the socio-economic, legal, and institutional framework may be developed for the provision of Flexible Transport Systems (FTS).
The objective of this paper is twofold: first to present an integrated methodological framework for developing and assessing
alternative FTS business models and second to demonstrate its applicability to a case study regarding the prioritization of
alternative FTS business models for the provision of flexible passenger transport services in Helsinki.
相似文献
Teemu SihvolaEmail: |
87.
Exploring spatial variety in patterns of activity-travel behaviour: initial results from the Toronto Travel-Activity Panel Survey (TTAPS) 总被引:1,自引:0,他引:1
Studies of urban travel behaviour typically focus on weekday activities and commuting. This is surprising given the rising
contribution of discretionary activities to daily travel that has occurred during the last few decades. Moreover, current
understanding of the relationship between travel behaviour and land use remains incomplete, with little research carried out
to explore spatial properties of activity-travel behaviour during the off-peak and weekend time periods. Weekend behaviours,
for example, influenced by the availability of time and the spatiotemporal distribution of “weekend” destinations, likely
produce spatially and temporally distinct activity-travel patterns. Using data from the first wave of the Toronto Travel-Activity
Panel Survey (TTAPS), this paper examines an area of research that has received little attention; namely, the presence of
spatial variety in activity-travel behaviour. The paper begins by looking at the extent to which individuals engage in spatially
repetitive location choices during the course of a single week. Area-based measures of geographical extent and activity dispersion
are then used to expose differences in weekday-to-weekend and day-to-day activity-travel patterns. Examination of unclassified
activities carried out over a 1 week period reveals a level of spatial repetition that does not materialise across activities
classified by type, travel mode, and planning strategy. Despite the inherent spatial flexibility offered by the personal automobile,
spatial repetition is also found to be surprisingly similar across travel modes. The results also indicate weekday-to-weekend,
and day-to-day fluctuations in spatial properties of individual activity-travel behaviour. These findings challenge the utility
of the short-run survey as an instrument for capturing archetypal patterns of spatial behaviour. In addition, the presence
of a weekday-to-weekend differential in spatial behaviour suggests that policies targeting weekday travel reduction could
have little impact on travel associated with weekend activities.
相似文献
Tarmo K. RemmelEmail: |
88.
E. N. Smith E. Velenis D. Tavernini D. Cao 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(2):221-248
In this paper, the effect of both passive and actively-modified vehicle handling characteristics on minimum time manoeuvring for vehicles with 4-wheel torque vectoring (TV) capability is studied. First, a baseline optimal TV strategy is sought, independent of any causal control law. An optimal control problem (OCP) is initially formulated considering 4 independent wheel torque inputs, together with the steering angle rate, as the control variables. Using this formulation, the performance benefit using TV against an electric drive train with a fixed torque distribution, is demonstrated. The sensitivity of TV-controlled manoeuvre time to the passive understeer gradient of the vehicle is then studied. A second formulation of the OCP is introduced where a closed-loop TV controller is incorporated into the system dynamics of the OCP. This formulation allows the effect of actively modifying a vehicle's handling characteristic via TV on its minimum time cornering performance of the vehicle to be assessed. In particular, the effect of the target understeer gradient as the key tuning parameter of the literature-standard steady-state linear single-track model yaw rate reference is analysed. 相似文献
89.
B. Blanco A. Alonso L. Kari N. Gil-Negrete J. G. Giménez 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(4):529-552
The finite length nature of rail-pad supports is characterised by a Timoshenko beam element formulation over an elastic foundation, giving rise to the distributed support element. The new element is integrated into a vertical track model, which is solved in frequency and time domain. The developed formulation is obtained by solving the governing equations of a Timoshenko beam for this particular case. The interaction between sleeper and rail via the elastic connection is considered in an analytical, compact and efficient way. The modelling technique results in realistic amplitudes of the ‘pinned–pinned’ vibration mode and, additionally, it leads to a smooth evolution of the contact force temporal response and to reduced amplitudes of the rail vertical oscillation, as compared to the results from concentrated support models. Simulations are performed for both parametric and sinusoidal roughness excitation. The model of support proposed here is compared with a previous finite length model developed by other authors, coming to the conclusion that the proposed model gives accurate results at a reduced computational cost. 相似文献
90.
In order to improve the economical and environmental performances of the Diesel engines, the present paper aims to bring to the forefront solutions to increase the efficiency of the supercharging process carried out by the aggregates with Comprex type pressure waves. One solution to this is to drive the Comprex, not by the supercharged engine as it currently happens, but by a DC motor. The speed of the electric motor is modified, by means of an electronic management system, depending on the speed and load of the Diesel engine. The paper presents the experimental results obtained during the investigation of a supercharged Diesel engine by the Comprex driven type according to the proposed solution. 相似文献