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481.
As a newly industrialized country, Korea has shown remarkable economic progress in the last three decades. This phenomenal growth has rapidly increased demands for better quality of life. This includes, among others, increasing demand for high quality transportation system services. In this paper, the method of Analytic Hierarchy Process (AHP) is utilized to evaluate rural highway improvement projects in Korea. The appropriate rural highway improvement projects for widening and paving were selected and studied on the basis of some selection criteria. The results have shown that there are some significant differences in prioritizing projects using the traditional economic evaluation method as compared to those resulting from the use of AHP. As demonstrated, the AHP proves to be an effective tool in evaluating transportation system projects. 相似文献
482.
Tae-Woo Lee 《Maritime Policy and Management》1996,23(2):177-186
The issues surrounding the future of Korea's shipping policy have been heavily debated since 1990 because the Korean shipping industry has been facing rising crew costs and difficulties in recruitment of qualified crew, an adverse taxation system, very limited access to foreign capital markets, and an inflexible government regulatory environment. Consequently, this has contributed to the deterioration of Korea's compectitive edge. This paper aims to provide both an account of the current adverse situtation in Korean shipping business and proposals to alleviate the plight of shipping enterprises. Within the context of that adversity, two solutions are suggested to improve the current situation, by either establishing a Korean second register or flagging out. The paper explores the advantages and disadvantages of each solution. Because ship management is closely interrelated to flagging strategies, the paper also discusses areas of co-operation between Korean shipping or ship management companies and advanced foreign ship management companies. 相似文献
483.
J. Jung J. H. Lee S. Song K. M. Chun 《International Journal of Automotive Technology》2008,9(4):423-428
Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration.
Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate
the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction
mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation
process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO2-O2-H2O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range
of 250∼500°C. This value was exceedingly lower than the activation energy of NO2-O2 oxidation, which was 60±3 kJ/mol. When NO2 exists with O2 and H2O, the reaction rate increases in proportion to NO2. It increases nonlinearly with O2 or H2O concentration when the other two oxidants are fixed. 相似文献
484.
Jin Sol Cheon Beom-Seon Jang Ki Ho Yim HoSeong Daniel Lee Bon-Yong Koo Hanbaek Ju 《Journal of Marine Science and Technology》2016,21(2):309-324
Normally, the design slamming pressure on the bottomof a semi-submersible-type floating rig is determined in a simple way using the relative speed obtained from an air-gap analysis. However, few studies have taken a thorough, robust, and deep-background approach to the estimation of design pressure. To investigate the slamming pressure on the bottom of a semi-submersible rig, a simplified deformable stiffened plate of a zero-degree deadrise angle is simulated using the nonlinear FEM software LS-DYNA, which can take the influence of fluid–structure interaction (FSI) into account. Various parametric studies are carried out to examine the effects of structural flexibility, coupling stiffness, mesh size, velocity, stiffener size, and air cushion. The pressure response on the plate by the coupling of fluid and structure is studied and the FSI effect of each parameter is discussed. Then, equivalent transient and static loads that result in the same maximum or permanent deformation as FSI are evaluated for design purposes through a series of parametric studies. 相似文献
485.
Low heating value (LHV) of di-methyl ether (DME) is lower than that of diesel. To get the similar heat value with diesel from the diesel engine operation, single injection quantity of DME should be increased. This investigation was tried to increase the injection quantity of DME by the modified diesel injector and investigated the penetration length and spray angle of DME spray. DME was injected by using three-type modified diesel injectors those nozzle-hole diameters (Injector 1: 1.66 mm, Injector 2 and 3: 0.25 mm) and orifice diameters were different (Injector 1 and 2: 0.6 mm, Injector 3: 1 mm). Spray characteristics of DME was investigated with a various ambient pressures (2.5, 5.0 MPa) in the constant volume chamber and a fuel was injected by varied injection pressure from 35 to 70 MPa by interval of 5 MPa using a DME common rail fuel injection system. The result shows that DME injection quantity by Injector 3 was 1.69 ~ 2.02 times larger than that of diesel injection quantity by Injector 1. In this case, DME spray got the similar heat value compared with diesel spray. The penetration speed of DME spray by Injector 3 was the fastest, thus when the spray development was end, the penetration length of DME spray by Injector 3 was the longest compared with the other cases. In case of the spray angle, Injector 2 and 3 had the similar spray angle and these were larger than that of diesel and DME sprays by Injector 1. As the result, Injector 3 was the solution for how to solve the low heating value of DME. 相似文献
486.
This work details the simulation of tsunami waves generated by seaquakes in the Manila Trench and their effect on fixed oil and gas jacket platforms in waters offshore North Borneo. For this study, a four-leg living quarter jacket platform located in a water depth of 63m is modelled in SACS v5.3. Malaysia has traditionally been perceived to be safe from the hazards of earthquakes and tsunamis. Local design practices tend to neglect tsunami waves and include no such provisions. In 2004, a 9.3M w seaquake occurred off the northwest coast of Aceh, which generated tsunami waves that caused destruction in Malaysia totalling US$ 25 million and 68 deaths. This event prompted an awareness of the need to study the reliability of fixed offshore platforms scattered throughout Malaysian waters. In this paper, we present a review of research on the seismicity of the Manila Trench, which is perceived to be high risk for Southeast Asia. From the tsunami numerical model TUNA-M2, we extract computer-simulated tsunami waves at prescribed grid points in the vicinity of the platforms in the region. Using wave heights as input, we simulate the tsunami using SACS v5.3 structural analysis software of offshore platforms, which is widely accepted by the industry. We employ the nonlinear solitary wave theory in our tsunami loading calculations for the platforms, and formulate a platform-specific risk quantification system. We then perform an intensive structural sensitivity analysis and derive a corresponding platform-specific risk rating model. 相似文献
487.
In this paper, we demonstrate the use of an inexpensive and easy-to-collect long-term dataset to address the problems caused by basing activity space studies off short-term data. In total, we use 63,114 geo-tagged tweets from 116 unique users to create individuals’ activity spaces based on minimum bounding geometry (convex hull). By using polygon density maps of activity space, we found clear differences between weekday and weekend activity spaces, and were able to observe the growth trajectory of activity space over 17 weeks. In order to reflect the heterogeneous nature of spatial behavior and tweeting habits, we used Latent Class Analysis twice. First, to identify five unique patterns of location-based activity spaces that are different in shape and anchoring. Second, we identify three unique growth trajectories. The comparison among these latent growth trajectories shows that in order to capture the extent of activity spaces we need long time periods for some individuals and shorter periods of observation for others. We also show that past studies using a single digit number of weeks may not be sufficient to capture individuals’ activity space. The major activity locations identified using a multilevel latent class model, do not appear to be statistically related to the growth patterns of Twitter users activity spaces. The evidence here shows Twitter data can be a valuable complementary source of information for heterogeneity analysis in activity-based modeling and simulation. 相似文献
488.
Since 2012, the Korean and EU governments have been running a tyre labelling system. All tyres sold in Korea have to carry a label that displays information of two performance criteria: rolling resistance and wet grip. The rolling resistance of the tyres determines their fuel efficiency grading, and the wet grip of the tyres determines their braking safety grading. The rolling resistance and wet grip measurements must be reproducible, so the same tests on the same tyres in different laboratories must produce the same results to ensure a fair comparison between tyres from different suppliers. In addition, a good reproducibility of testing results prevents market surveillance authorities from obtaining results different from those provided by suppliers when testing the same tyres. The laboratory alignment procedure for the rolling resistance measurements was developed and published as the EU Commission Regulation No. 1235 in 2011. However, the laboratory alignment procedure for the wet grip measurements has not yet been developed. Therefore, there are many differences in the wet grip test results among test laboratories throughout the world. The new procedure that is proposed for the wet grip measurement alignment for tyre testing laboratories can improve the reproducibility of the wet grip testing results, and five laboratory alignment tests were carried out between KATECH and five other test laboratories in the world to evaluate the results of the proposed procedure. 相似文献
489.
Jounghee Lee Dongyoon Hyun Kyoungseok Han Seibum Choi 《International Journal of Automotive Technology》2018,19(4):651-658
The longitudinal location of a vehicle’s center of gravity (CG) is used as an important parameter for vehicle safety control systems, and can change considerably according to various driving conditions. Accordingly, for the better performance of vehicle safety control systems, it is essential to obtain the accurate CG location. However, it is generally difficult to acquire the value of this parameter directly through sensors due to cost reasons. In this study, a practical algorithm for estimating vehicle’s longitudinal CG location in real time is proposed. This algorithm is derived based only on longitudinal motion of the vehicle, excluding excessive lateral, yaw and roll movements of the vehicle. Moreover, the proposed algorithm has main differences from previous studies in that it does not require information such as vehicle mass, vehicle moments of inertia, road grade or tire-road surface friction, which are difficult to acquire. In the proposed algorithm, the relationship between the ratio of rear-to-front tire longitudinal force and the corresponding wheel slips are used to determine the CG location. To demonstrate a practical use of the proposed algorithm, the ideal brake force distribution is tested. The proposed CG estimation algorithm and its practical use are verified via simulations and experiments using a test vehicle equipped with electro-mechanical brakes in the rear wheels. It is shown that the estimated CG locations are close to the actual ones, and that the deceleration can be maximized by the ideal brake force distribution. 相似文献
490.
Heeyun Lee Juyean Sung Hyeokjun Lee Chunhua Zheng Wonsik Lim Suk Won Cha 《International Journal of Automotive Technology》2018,19(4):687-694
In this study, a model-based integrated control method for engines and continuous variable transmissions (CVTs) is developed. CVT refers to a type of transmission which allows an engine to be operated independently with respect to the vehicle speed, with the engine torque and CVT gear ratio controlled in an integrated manner. In the proposed integrated control scheme, engine operating points which minimize the rate of instantaneous fuel consumption are calculated, and the engine target torque and target gear ratio are determined in an integrated manner based on the results of the calculations. Unlike the previous map-based control method, the method introduced in this study does not require an engine torque map or a CVT ratio map for tuning, and the engine torque and CVT ratio are controlled to minimize the amount of fuel used while satisfying the level of acceleration demand from the driver. The control scheme is based on the powertrain model, and the CVT response lag and transmission loss are also considered in the integrated control processes. The algorithm is simulated with various driving cycles, with the simulation results showing that the fuel economy performance of the vehicle system is improved with the newly suggested engine-CVT integrated control algorithm. 相似文献