全文获取类型
收费全文 | 725篇 |
免费 | 8篇 |
专业分类
公路运输 | 218篇 |
综合类 | 24篇 |
水路运输 | 213篇 |
铁路运输 | 17篇 |
综合运输 | 261篇 |
出版年
2023年 | 13篇 |
2022年 | 21篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 29篇 |
2017年 | 17篇 |
2016年 | 34篇 |
2015年 | 9篇 |
2014年 | 40篇 |
2013年 | 106篇 |
2012年 | 35篇 |
2011年 | 42篇 |
2010年 | 34篇 |
2009年 | 44篇 |
2008年 | 36篇 |
2007年 | 20篇 |
2006年 | 19篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 13篇 |
1998年 | 4篇 |
1997年 | 12篇 |
1996年 | 7篇 |
1995年 | 12篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 4篇 |
排序方式: 共有733条查询结果,搜索用时 484 毫秒
711.
C. H. Zheng G. Q. Xu Y. I. Park W. S. Lim S. W. Cha 《International Journal of Automotive Technology》2014,15(1):117-123
Pontryagin’s Minimum Principle (PMP) and Dynamic Programming (DP) are both from the optimal control theory and can both achieve optimal trajectories when they are applied to power management strategies of hybrid vehicles. However they have totally different control concepts. In order to select the superior one, the PMP-based and the DP-based power management strategies are introduced and compared for a fuel cell hybrid vehicle (FCHV) in this paper. The two power management strategies are applied to the FCHV in a computer simulation environment, and the simulation results from the two strategies are compared when the control variable for the PMP is fuel cell system (FCS) net power and for the DP is battery power. As a result, the superiority of the PMP-based power management strategy is proved. 相似文献
712.
J. H. Jeong D. W. Jung O. T. Lim Y. D. Pyo Y. J. Lee 《International Journal of Automotive Technology》2014,15(6):861-869
This work experimentally investigates how the dwell time between pilot injection and main injection influences combustion and emissions characteristics (NOx, CO, THC and smoke) in a single-cylinder DI diesel engine. The experiments were conducted using two fuel injection systems according to the fuel type, diesel or dimethyl ether (DME), due to the different fuel characteristics. The injection strategy is accomplished by varying the dwell time (10°CA, 16°CA and 22°CA) between injections at five main injection timings (?4°CA aTDC, ?2°CA aTDC, 0°CA aTDC, 2°CA aTDC and 4°CA aTDC). Results from pilot-main injection conditions are compared with those shown in single injection conditions to better demonstrate the potential of pilot injection. It was found that pilot injection is highly effective for lowering heat-release rates with smooth pressure traces regardless of the fuel type. Pilot injection also offers high potential to maintain or increase the BMEP; even the combustion-timing is retarded to suppress the NOx emission formation. Overall, NOx emission formation was suppressed more by the combustion phasing retard effect, and not the pilot injection effect considered in this study. Comparison of the emissions for different fuel types shows that CO and HC emissions have low values below 100 ppm for DME operation in both single injection and pilot-main injection. However, NOx emission is slightly higher in the earlier main injection timings (?4°CA aTDC, ?2°CA aTDC) than diesel injections. Pilot injection was found to be more effective with DME for reducing the amount of NOx emission with combustion retardation, which indicates a level of NOx emission similar to that of diesel. Although the diesel pilot-main injection conditions show higher smoke emission than single-injection condition, DME has little smoke emission regardless of injection strategy. 相似文献
713.
Hot judder simulation of a ventilated disc and design of an improved disc using sensitivity analysis
J. H. Park T. W. Park J. H. Lee M. H. Cho 《International Journal of Automotive Technology》2014,15(1):1-6
In a disc brake system, thermal expansion of the material is caused by friction energy that is generated by the sliding contact between a disc and pad during braking. This phenomenon, thermo-elastic instability, can lead to hot spots on the disc surface and a hot judder phenomenon. Transient finite element analysis has been used to simulate this phenomenon. Three dimensional finite element models of a disc, pad, and cylinder were created. Each part was connected by a joint. Contact condition was applied to the disc and pad with a friction coefficient (μ) of 0.4. A convective heat transfer coefficient was set as 40 W/m2K. Using a commercial program SAMCEF, the simulation of the thermo-mechanically coupled system was performed. In order to find the sensitive parameters of brake judder, sensitivity analysis was carried out with consideration for disc design parameters. As a result, the hot spot phenomenon was confirmed and hot judder was predicted. Moreover, the more sensitive parameters of the hot judder phenomenon were presented. Finally, an improved disc model and an analysis technique were verified by comparison to dynamo test results. 相似文献
714.
From MY2010 US-NCAP, the 5th percentile female Hybrid III dummy has been used for the safety evaluation of the right front passenger position in the frontal impact test. In Korea, the Ministry of Land, Infrastructure and Transport (MLIT) decided to evaluate the safety of the 5th percentile female dummy in the frontal impact test from 2013 KNCAP. In this paper, using the frontal NCAP data for the 5 vehicles available from the NHTSA test database, the safety of the 5th percentile female dummy were examined. Using the evaluation and rating method by the KNCAP, 5 vehicles received 5 stars. Using the evaluation and rating method by the US-NCAP, only one vehicle received 5 stars and the remaining 4 vehicles received 4 stars. In the US-NCAP, the Nij was the most influential factor for the star rating. In the KNCAP, the evaluation and rating method for the 5th percentile female Hybrid III dummy is less stringent than the method of the US-NCAP. The evaluation and rating method is proposed to increase the stringency of the star rating for the female dummy in the KNCAP. 相似文献
715.
S. G. Zuo T. X. Ni X. D. Wu K. Wu X. W. Yang 《International Journal of Automotive Technology》2014,15(3):505-515
As a research method, finite element analysis (FEA) with ABAQUS can help researchers to study throughout the whole process of abnormal tire wear. For precise tread wear simulation, this paper introduces a tire finite element model building method. Then, the model is verified by comparing its simulation results with experiment data. Based on the verified model, tire high-speed rolling procedure is presented by combining steady-state transport analysis and dynamic analysis. To predict the wear distribution, micro tread wear calculation method is described. Finally, the wear prediction procedure of tread mesh evolving is introduced and tire polygonal wear pattern is simulated by this procedure. 相似文献
716.
W. K. Park S. D. Mun H. K. Lee G. E. Yang 《International Journal of Automotive Technology》2011,12(5):705-712
Compressed air can be used as an energy source for brake systems in medium-heavy and heavy-duty commercial vehicles. The moisture
in compressed air, which is due to high temperature and humidity, can be eliminated by using an air dryer. In this paper,
drying performance data for a cartridge were obtained and used to develop a drying performance program, to predict the moisture
and relative humidity in the air tanks of vehicles. The on-load time, off-load time, air flow, duty cycle, humidity and dew
point temperature were calculated according to air consumption. The validity of the program was verified, and it was shown
to be able to predict humidity changes in the air tank. The air tank capacity was increased from 100 to 130 to reduce the
duty cycle. Therefore, the regeneration rate decreased from 18% to 15%, but the dew point depression temperature (ΔT) remained
above 30°C. The duty cycle decreased from 50% to 43%, and the total operation time and power consumption of the air compressor
were reduced. In conclusion, fuel savings were obtained by changing the parameters to optimize the system. 相似文献
717.
G. H. Lee W. C. Choi S. I. Kim S. O. Kwon J. P. Hong 《International Journal of Automotive Technology》2011,12(2):291-297
This paper identifies a control method used to reduce torque ripple of a permanent magnet synchronous motor (PMSM) for an
electric power steering (EPS) system. NVH (Noise Vibration Harshness) is important for safe and convenient driving. Vibration
caused by motor torque is a problem in column type EPS systems. Maintaining a very low torque ripple is one solution that
allows for smoother steering. Theoretically, it is possible to design and drive the motor without torque ripple. However,
in reality, a PMSM system torque ripple is caused by the motor itself (saturation in the iron core and EMF distortion) and
the imperfect driver. This paper analyzes torque ripple of a PMSM system, and an advanced PMSM control method for the column
typed EPS system is presented. Results of the analysis indicate that the compensation current is needed in order to minimize
torque ripple when a PMSM is driven. 相似文献
718.
Changes in Swiss accessibility since 1850 总被引:2,自引:0,他引:2
This paper discusses the changes in Swiss accessibility since 1850 after arguing that such spatially detailed measures are needed, if one wants to understand the impact of transport investment on the economy and land use patterns.The road-based accessibility overtook that offered by the railways around 1930 and has kept a steady relative lead since then. The relative advantage of the large cities has been eroded since 1950 through their population loss and the massive population gain of the metropolitan fringe. In absolute terms, though, they are still locations with the highest accessibilities. 相似文献
719.
Assessing the impact of characteristics of the built environment on travel behavior can yield valuable tools for land use
and transportation planning. Of particular interest are planning models that can estimate the effects of ‘smart growth’ planning.
In this paper, a post-processor method of quantifying and searching for relationships among many aspects of travel behavior
and the built environment is developed and applied to the Buffalo, NY area. A wide scope of travel behavior is examined, and
over 50 variables, many of which are based on high-detail data sources, are examined for potentially quantifying the built
environment. Linear modeling is then used to relate travel behavior and the built environment, and the resulting models may
be applied in a post-processor fashion to travel models to provide some measure of sensitivity to built environment modifications.
The study’s findings demonstrate that mode choice is highly correlated to measures of the built environment, and that many
of the principles of smart growth appear to be a valid way to encourage non-vehicle travel. Home-based VHT and VMT appear
to be affected by the built environment to a lesser degree. 相似文献
720.
This study introduces an extended version of a standard multilevel cross-classified logit model which takes co-variations
into account, i.e., variations jointly caused by two or more unobserved factors. Whilst focusing on mode choice behavior,
this study deals with four different types of variation: spatial variations, inter-individual variations, intra-individual
variations and co-variations between inter-individual and spatial variations. Such co-variations represent individual-specific
spatial effects, reflecting different responses to the same space among individuals, which may for example be due to differences
in their spatial perceptions. In our empirical analysis, we use data from Mobidrive (a continuous six-week travel survey) to clarify the existence of co-variation effects by comparing two models with and without
co-variation terms. The results of this analysis indicate that co-variations certainly exist, especially for utility differences
in bicycle and public transport use in comparison with car use. We then sequentially introduce four further sets of explanatory
variables, examine the sources of behavioral variations and determine what types of influential factors are dominant in mode
choice behavior. 相似文献