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排序方式: 共有484条查询结果,搜索用时 31 毫秒
191.
W. Ryu N. Cho I. Yoo H. Song H. Kim 《International Journal of Automotive Technology》2009,10(1):115-121
In this study, the performance of a CVT clutch system for a hybrid electric vehicle was investigated. To analyzed the vehicle
performance at restart, the restart delay and driveshaft torque was investigated by simulations and experiments. It was found
from the simulation results that the vehicle restart response depends on the clutch pressure buildup time to the point where
the clutch torque begins to overcome the vehicle road load, and driving comfort at restart is directly related to the rate
change of the clutch pressure. 相似文献
192.
S. H. Jun T. K. Kim J. Y. Jang Y. Kidoguchi 《International Journal of Automotive Technology》2009,10(6):663-668
In an earlier study, the current authors showed that an unsteady-state lifted flame generated by an equivalence ratio conversion
system for a given fuel, was similar to a steady-state lifted flame in terms of the change characteristics from a premixed
flame to a critical flame and then to a triple flame with a diffusion flame positioned in the middle according to the concentration
difference. Therefore, this study used an OH-PLIF method to investigate the characteristics of a steady-state lifted flame
and an unsteady-state lifted flame created under conditions identical to the flames in the preceding study. PLIF (Planar laser
induced fluorescence) is practically effective for visualizing the concentration fields within a flame. The resulting OH-radical
measurements showed that an unsteady-state lifted flame created under the specific conditions used in this study showed similar
tendencies in terms of OH-radical distribution, fluorescence intensity, and liftoff height, to a steady-state lifted flame,
thereby confirming that the behavior of an unsteady-state lifted flame can be effectively predicted based on the behavior
of a steady-state lifted flame. 相似文献
193.
Y. T. Son B. Y. Kim K. J. Park H. Y. Lee H. J. Kim M. W. Suh 《International Journal of Automotive Technology》2009,10(5):635-644
To guarantee the efficiency of maintenance strategies for a complex structure, safety and cost limitations must be considered.
This research introduces RCM-based (Reliability Centered Maintenance) life cycle optimization for reasonable maintenance.
The design variable is the reliability of each part, which consists of a complex structure, while the objective is to minimize
the total cost function in order to maintain the system within the desired system reliability. This research constructs the
cost function that can reflect the current operating condition and maintenance characteristics of individual parts by generating
essential cost factors. To identify the optimal reliability of each component in a system, this paper uses a Neuro-Evolutionary
technique. Additionally, this research analyzes the reliability growth of a system by using the AMSAA (Army Material Systems
Analysis Activity) model to estimate the failure rate of each part. The MTBF (Mean Time Between Failure) and the failure rate
of the whole system, which is responding to the individual parts, are estimated based on the history data by using neural
networks. Finally, this paper presents the optimal life cycle of a complex structure by applying the optimal reliability and
the estimated MTBF to the RAMS (Reliability, Availability, Maintainability, and Safety) algorithm. 相似文献
194.
Sejoon Kim 《Coastal management》2018,46(3):222-234
The release of captive dolphins (Tursiops aduncus) from South Korean marine parks, which occurred in 2013, 2015, and 2017, is described and evaluated for its usefulness for conservation of coastal ecosystems. The campaign to free the dolphins created a flagship species, uniting the efforts of national government agencies, local government, and NGOs. However, the Korean management agencies framed the release as a species-specific conservation intervention, while the NGOs brought forward welfare-based demands for the curtailment of cetacean captivity. We argue that the release of the Korean dolphins changed the policy climate, to facilitate two major policy changes: revision of anti-whaling regulations to prohibit capture of cetaceans for exhibit, and improvement of regulations for rescue, rehabilitation, and release of stranded marine animals. Tradeoffs between welfare and conservation concerns are described in terms of risk for the management agency, welfare for the animals, and feasibility of a continued commitment to maintain the viability of the dolphin stock in the wild. The release of captive animals to their native range relies on a single-species conservation focus which poses little risk for management agencies but does not guarantee their continued commitment. 相似文献
195.
Jooyoung Kim 《运输规划与技术》2017,40(4):465-478
In a destination choice model, it is important to introduce alternatives that have been adequately aggregated into traffic analysis zone levels based on spatial similarities and feasibility of analysis, because considering every spatial location possible for the traveler as an elemental alternative is intractable in terms of data management and analysis. In this study, we derive strata for alternative sets through simple random sampling and stratified importance sampling based on the concept of Moran’s I. As a result of comparative analysis, we are able to reduce errors by drawing an adequate number of samples for the destination choice model’s choice alternative sets based on measures of spatial similarity. 相似文献
196.
Sung-Pil Hong Yun-Hong Min Myoung-Ju Park Kyung Min Kim Suk Mun Oh 《Transportation》2016,43(5):749-769
The aim of this study is to estimate both the physical and schedule-based connections of metro passengers from their entry and exit times at the gates and the stations, a data set available from Smart Card transactions in a majority of train networks. By examining the Smart Card data, we will observe a set of transit behaviors of metro passengers, which is manifested by the time intervals that identifies the boarding, transferring, or alighting train at a station. The authenticity of the time intervals is ensured by separating a set of passengers whose trip has a unique connection that is predominantly better by all respects than any alternative connection. Since the connections of such passengers, known as reference passengers, can be readily determined and hence their gate times and stations can be used to derive reliable time intervals. To detect an unknown path of a passenger, the proposed method checks, for each alternative connection, if it admits a sequence of boarding, middle train(s), and alighting trains, whose time intervals are all consistent with the gate times and stations of the passenger, a necessary condition of a true connection. Tested on weekly 32 million trips, the proposed method detected unique connections satisfying the necessary condition, which are, therefore, most likely true physical and schedule-based connections in 92.6 and 83.4 %, respectively, of the cases. 相似文献
197.
Safety mechanism is required for an automotive battery pack to prevent thermal failure which could lead to catastrophic events. Passively cooled battery packs can prevent thermal failure by conducting adaptive control of battery power without any external cooling device. The key to this power control is how to secure battery safety while minimizing energy loss. This paper proposes a novel, adaptive power control strategy for automotive passive-cooling battery packs. Four different cases with electrochemical battery model are simulated and compared to each other according to a city driving profile. Driving simulation result confirmed that the present power control algorithm is an effective solution for preventing thermal failure along with improving energy efficiency of automotive battery packs. 相似文献
198.
In 1994, Townend proposed a method to calculate the relative changes in various wave characteristics and structure-related parameters due to sea level rise for regular waves. The method was extended to irregular waves by Cheon and Suh in 2016. In this study, this method is further extended to include the effect of future change in offshore wave height and the sea level rise. The relative changes in wavelength, refraction coefficient, shoaling coefficient, and wave height in nearshore area are presented as functions of the relative changes in water depth and offshore wave height. The calculated relative changes in wave characteristics are then used to estimate the effect of sea level rise and offshore wave height change on coastal structures by calculating the relative changes in wave run-up height, overtopping discharge, crest freeboard, and armor weight of the structures. The relative changes in wave characteristics and structure-related parameters are all expressed as a function of the relative water depth for various combinations of the relative changes in water depth and offshore wave height. 相似文献
199.
J. Kim 《International Journal of Automotive Technology》2010,11(3):331-337
A methodology is presented for estimating vehicle handling dynamics, which are important to control system design and safety
measures. The methodology, which is based on an extended Kalman filter (EKF), makes it possible to estimate lateral vehicle
states and tire forces on the basis of the results obtained from sinusoidal steering stroke tests that are widely used in
the evaluation of vehicle and tire handling performances. This paper investigates the effect of vehicle-road system models
on the estimation of lateral vehicle dynamics in the EKF. Various vehicle-road system models are considered in this study:
vehicle models (2-DOF, 3-DOF, 4-DOF), tire models (linear, non-linear) and relaxation lengths. Handling tests are performed
with a vehicle equipped with sensors that are widely used by vehicle and tire manufacturers for handling maneuvers. The test
data are then used in the estimation of the EKF and identification of lateral tire model coefficients. The accuracy of the
identified values is validated by comparing the RMS error between experimentally measured states and regenerated states simulated
using the identified coefficients. The results show that the relaxation length of the tire model has a notable impact on the
estimation of lateral vehicle dynamics. 相似文献
200.
Kwang Hyo Jung Kyung Chun Kim Sang Youl Yoon Seong Hun Kwon Ho Hwan Chun Moon Chan Kim 《Journal of Marine Science and Technology》2006,11(4):270-278
Stereoscopic particle image velocimetry measurements were made in a wind tunnel using a prototype waterjet model. The main
wind tunnel provided the vehicle velocity and a secondary wind tunnel was set up as the waterjet propulsion model. Pressure
distributions along the ramp and lip sides inside the duct were measured for three jet velocity to vehicle velocity ratios.
Three-dimensional velocity fields were obtained at the intake entrance and the nozzle exit of the waterjet system. The flow
into the duct was faster in the lip region than on the ramp side. Because of the variation in intake geometry from a rectangular
to a circular section and because of the sudden curvature change on the lip side, a pair of counter-rotating vortices was
observed in the mean velocity field at the nozzle exit. In addition, the turbulent kinetic energy correlated with the vortex
pair was stronger on the lip side than in other areas. Dominant large-scale structures were extracted by using a snapshot
proper orthogonal decomposition analysis. It was found that most of the turbulent kinetic energy was attributed to at least
three vortices near the nozzle exit. This detailed three-dimensional velocity field will be useful for the verification of
CFD simulations applied to the waterjet system. 相似文献