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341.
A modified CVT ratio map is proposed to obtain the improved fuel economy for a metal belt CVT. Since the CVT system loss,
which occupies most of the drivetrain loss, depends on the engine speed, input torque, primary and secondary actuator pressure,
a modified CVT ratio map is produced to realize the highest engine-CVT overall efficiency through the consideration of CVT
system loss. The modified CVT ratio map is constructed with respect to the demanded vehicle power and present vehicle speed
based on the steady state CVT system loss. Using the modified CVT ratio map, performance simulations are carried out using
the dynamic models of the CVT powertrain. The simulation results indicate that the modified CVT ratio control provides improved
engine-CVT overall system efficiency, and improves the fuel economy of the federal urban driving schedule by 4.9 percent. 相似文献
342.
Alexander Olshevskiy Alexey Olshevskiy Svetlana Inshakova Chang-Wan Kim 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(10):1492-1507
In this study, simulations of shunting impacts for groups of freight cars that include up to six cars are considered. The simulation technique employs a white-box improved dynamic model of friction draft gear considering all its components and detailed finite element models of the freight cars. The key differences between the one-to-one shunting impact and the impact of long groups of cars in terms of features of the draft gear deflections and the coupler force time history are discussed. We present an example of dynamic finite element analysis for the car body using the coupler force time history obtained from the shunting impact simulation. 相似文献
343.
Dong Won Yi Soung Hie Kim Hyung Rim Choi Nam-Kyu Park Tae-Woo Lee 《Maritime Policy and Management》2000,27(2):155-167
It is an important matter closely connected with saving logistics costs, as well as encouraging national competitive power, to improve the productivity of container terminals by efficient utilization of container terminal resources. In this respect, this paper tries to suggest a conceptual model for sharing container terminal resources, taking as a case study the Gamman Container Terminal (GCT) in the port of Pusan. In so doing, it identifies what kinds of resources can be systematically shared from the viewpoint of their common use and draws some problems resulting from terminal operation by four operators at GCT. The model does not imply the conception that each terminal has its own resources individually, but recommends that tentatively-called Container Terminal Resource Management Center (CTRMC) should be established and operated in order to save operation and investment costs and improve operational efficiency. In addition, the continuous acquisition and life-cycle support (CALS) concept is imbedded in the model so that it can control the supply and demand of resources efficiently by sharing the database, through which the CTRMC can automatically identify the status of the excess or deficit of a certain resource in each berth at GCT. 相似文献
344.
345.
Hwa-Joong KimYoung-Tae Chang Kwang-Tae KimHyo-Jeong Kim 《Transportation Research Part D: Transport and Environment》2012,17(2):97-103
This paper provides an algorithm to minimize the fixed ordering, purchase, and inventory-carrying costs associated with bunker fuel together with ship time costs; and environmental costs associated with greenhouse gas emissions. It determines the optimum ship speed, bunkering ports, and amounts of bunker fuel for a given ship’s route. To solve the problem, we use an epsilon-optimal algorithm by deriving a property. The algorithm is illustrated by applying it to typical sample data obtained and the effects of bunker prices, carbon taxes, and ship time costs on the ship speed are analyzed. The results indicate that the ship speed and CO2 emissions are highly sensitive to the factors considered. 相似文献
346.
This paper studies the springing response of a flexible floating barge under an oblique wave. A time domain Rankine panel
method was used to represent fluid motion surrounding a flexible seagoing vessel, and a finite element method was used for
structural response. For accurate prediction of the structural response under an oblique wave, special attention was given
to the structural model, such as the effect of warping distortion and bending-torsion coupling. The Vlasov assumption was
followed for a deformable beam element to take into account the effect of warping distortion so that the cross section of
the beam deforms out of its original plane without changing its cross-section contour. The coupled equation for both the fluid
and structural domain was solved by using the implicit iterative method. A fixed point iteration with a relaxation scheme
was employed in this study with the aid of the Aitken δ2 process seeking acceleration of solution convergence. Accuracy of a developed computer program was verified through the comparison
with experimental work done by Remy et al. (Experimental and numerical study of the wave response of a flexible barge, Hydroelasticity in Marine Technology, Wuxi, 2006) resulting in good correspondence between the two results. 相似文献
347.
Computational predictions of ship-speed performance 总被引:1,自引:0,他引:1
Jung-Eun Choi Jung-Hun Kim Hong-Gi Lee Bong-Jun Choi Dong-Hyun Lee 《Journal of Marine Science and Technology》2009,14(3):322-333
This paper examines ship-speed performance based on acomputational method. The computations are carried out under identical
model conditions, i.e., resistance and self-propulsion tests, to predict the speed-power relationship. The self-propulsion
point is obtained from the self-propulsive computational results of two propeller rotative speeds. The speed-power relationship
in full scale is obtained through analyzing the computational results in model scale according to the model-ship performance
analysis method of ITTC’78. The object ship is a VLCC. The limiting streamlines and the distribution of the pressure coefficient
on the hull, the wake characteristics on the propeller plane, and the wave characteristics around a model ship are also investigated.
After completing the computations, a series of model tests are conducted to evaluate the accuracy of the predictions by comparing
the computational results with the experimental results. 相似文献
348.
Hyung Rim Choi Jae Joong Kim Jae Kee Lee Kang Bae Lee Joong Jo Shin 《Maritime Policy and Management》2018,45(3):388-402
To ensure the successful implementation of China’s Belt and Road (B&R) Initiative, it is essential to enable the real-time monitoring of containers’ locations, prevent theft during cargo delivery, ensure more efficient logistics management and reduce carbon emissions. For this, it is vital to have an economic and effective system to track and control containers across multiple countries. However, this requirement cannot be met by today’s container tracking systems because they are either limited within the borders of each country or expensive to employ internationally. This study thus presents a framework for an IoT-based container tracking system that enables users not only to grasp the international flow of container movement with one check but also to achieve smooth cross-border procedures. To verify the system’s performance, an empirical test was made for an actual container shipped from Korea to Poland. The test results showed that the system could successfully track the location of the container in real time across international borders. Last, this study discusses the policy development and international cooperation that should take place to enable the introduction of this container tracking system. 相似文献
349.
Conventional fixed-route bus services are generally preferred to flexible-route services at high demand densities, and vice versa. This paper formulates the problem of integrating conventional and flexible services that connect a main terminal to multiple local regions over multiple time periods. The system’s vehicle size, route spacing (for conventional services), service area (for flexible services), headways and fleet sizes are jointly optimized to minimize the sum of supplier costs and user costs. The route spacing for conventional bus services and service area for flexible bus services are also optimized for each region. The proposed solution method, which uses a genetic algorithm and analytic optimization, finds good solutions quickly. Numerical examples and sensitivity analyses confirm that the single fleet variable-type bus service may outperform either the single fleet conventional bus service or the single fleet flexible bus service when demand densities vary substantially among regions and time periods. 相似文献
350.
While most aggregate studies of transit ridership are conducted at either the stop or the route level, the present study focused
on factors affecting Metro ridership in the Seoul metropolitan area at the station-to-station level. The station-to-station
analysis made it possible to distinguish the effect of origin factors on Metro ridership from that of destination factors
and to cut down the errors caused by the aggregation of travel impedance-related variables. After adopting two types of direct-demand
patronage forecasting models, the multiplicative model and the Poisson regression model, the former was found to be superior
to the latter because it clearly identified the negative influences of competing modes on Metro ridership. Such results are
rarely found with aggregate level analyses. Moreover, the importance of built environment in explaining Metro demand was confirmed
by separating built environment variables for origin and destination stations and by differentiating ridership by the time
of day. For morning peak hours, the population-related variables of the origin stations played a key role in accounting for
Metro ridership, while employment-related variables prevailed in destination stations. In evening peak hours, both employment-
and population-related variables were significant in accounting for the Metro ridership at the destination station. This showed
that a significant number of people in the Seoul metropolitan area appear to take various non-home-based trips after work,
which is consistent with the results from direct household travel surveys. 相似文献