全文获取类型
收费全文 | 1184篇 |
免费 | 5篇 |
专业分类
公路运输 | 533篇 |
综合类 | 21篇 |
水路运输 | 265篇 |
铁路运输 | 15篇 |
综合运输 | 355篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 7篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 53篇 |
2017年 | 67篇 |
2016年 | 155篇 |
2014年 | 14篇 |
2013年 | 80篇 |
2012年 | 76篇 |
2011年 | 160篇 |
2010年 | 144篇 |
2009年 | 35篇 |
2008年 | 102篇 |
2007年 | 52篇 |
2006年 | 10篇 |
2005年 | 14篇 |
2004年 | 14篇 |
2003年 | 18篇 |
2002年 | 12篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 1篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有1189条查询结果,搜索用时 15 毫秒
171.
172.
173.
Stationar- und Ubergangsverhalten von Sattel- und Lasttugen bei der Kreisfahrt: Lineare Berechnungen
F. Vlk 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1983,12(6):331-350
Steady and Transient Turning of Tractor-Semitrailer and Truck-Trailer Combinations: A Linear Analysis
A simplified analysis is made of the yaw stability and control of the two types of the commercial vehicle combinations (tractor-semitrailer, truck-trailer) at a constant forward velocity during steady and transient turning. The combined vehicle is treated as a linear dynamic system (Fig. 2). The steer angle at the front wheels of the tractor (or truck) and the steady-state responses if the road verhicle train (yaw rate, articulation angles and sideslip angle) are calculated (Equations 18 to 25). Exploratory calculations are performed to determine the influence of the cornering stiffness of the tires for the two types of the vehicle combinations upon the steady-state responses (Figs. 7 to 10). For a linear simplified model of articulated vehicle the steady-state turning behaviour is stable also under conditions of rather high driving speed (70 km/h). A simplified analysis of the transient turning behaviour of the two types of road trains has shown the tractor-semitrailer to preserve stability even under driving speeds exceeding 70 km/h (Fig. 13), whereas the truck-trailer combinations appear to become oscillatory unstable if the driving speed rises above the 60 km/h margin (Fig. 14). 相似文献
A simplified analysis is made of the yaw stability and control of the two types of the commercial vehicle combinations (tractor-semitrailer, truck-trailer) at a constant forward velocity during steady and transient turning. The combined vehicle is treated as a linear dynamic system (Fig. 2). The steer angle at the front wheels of the tractor (or truck) and the steady-state responses if the road verhicle train (yaw rate, articulation angles and sideslip angle) are calculated (Equations 18 to 25). Exploratory calculations are performed to determine the influence of the cornering stiffness of the tires for the two types of the vehicle combinations upon the steady-state responses (Figs. 7 to 10). For a linear simplified model of articulated vehicle the steady-state turning behaviour is stable also under conditions of rather high driving speed (70 km/h). A simplified analysis of the transient turning behaviour of the two types of road trains has shown the tractor-semitrailer to preserve stability even under driving speeds exceeding 70 km/h (Fig. 13), whereas the truck-trailer combinations appear to become oscillatory unstable if the driving speed rises above the 60 km/h margin (Fig. 14). 相似文献
174.
Trucking industry demand for urban shared use freight terminals 总被引:1,自引:0,他引:1
The issue of shared use urban freight facilities first received attention during the 1970s when it was observed that, while inter-urban freight movements were becoming increasingly efficient, there were significant diseconomies in the movement of freight via truck within urban areas. Early research suggested that shared urban freight facilities should be constructed so that trucking companies could consolidate smaller shipments into larger ones. In the past few years, the concept of Urban Ports has gained increasing attention, not just for carriers who need to load and unload freight, but to provide a place near the urban center for truckers to wait out peak traffic periods. In this paper, using recently developed survey data, we examine trucking company interest in such facilities by examining the results of an ordered probit demand model. 相似文献
175.
G. S. Jung Y. H. Sung B. C. Choi C. W. Lee M. T. Lim 《International Journal of Automotive Technology》2012,13(3):347-353
Although premixed charge compression ignition (PCCI) combustion engines are praised for potentially high efficiency and clean
exhaust, experimental engines built to date emit more hydrocarbons (HCs) and carbon monoxide (CO) than the conventional machines.
These compounds are not only strictly controlled components of the exhaust gas of road vehicles but are also an energy loss
indicator. The prime objective of this study was to investigate the major sources of the HCs formed in the combustion chamber
of an experimental PCCI engine in order to suggest some effective technologies for HC reduction. In this study, to explore
the dominant sources of HC emissions in both operation modes, a single cylinder engine was prepared such that it could operate
using either conventional diesel combustion or PCCI combustion. Specifically, the contributions of the top-ring crevice volume
in the combustion chamber and the bulk quenching of the lean mixture were investigated. To understand the influence of the
shape and magnitude of the crevice on HC emissions, the engine was operated with 12 specially prepared pistons with different
top-ring crevices installed one after another. The engine emitted proportionally more HCs as the depth of the crevice increased
as long as the width remained narrower than the prevailing quench distance. The top-ring-crevice-originated exhaust HCs comprised
approximately 31% of the total HC emissions in the baseline condition. In a series of tests to estimate the effects of bulk
quench on exhaust HC emissions, intake air was heated from 300K to 400K in steps of 25K. With the intake air heated, HC and
CO emissions decreased with a gradually diminishing rate to zero at 375K. In conclusion, the most dominant sources of HC emissions
in PCCI engines were the crevice volumes in the combustion chamber and the bulk quenching of the lean mixtures. The key methods
for reducing HC emissions in PCCI engines are minimizing crevice volume in the combustion chamber and maximizing intake air
temperature allowed based on the permissible NOx level. 相似文献
176.
J. U. Cho A. Kinloch B. Blackman F. S. Rodriguez Sanchez M. S. Han 《International Journal of Automotive Technology》2012,13(7):1127-1131
Double-cantilever beam (DCB) and tapered double-cantilever beam (TDCB) specimens are the test configurations most commonly used to measure the fracture toughness of composites and adhesive joints. Strain rates of 1 to 18.47 m/s were applied to the test specimens via high-speed hydraulic test equipment. Because the fracture occurs through the adhesively bonded joints and the cracks grow rapidly, the crack length and beam displacement were recorded by a high-speed camera. An energy range from 0 to 10 J was often observed in the high-strain-rate fracture experiments for nonlinear plastic behavior of the dynamically loaded adhesively bonded DCB and TDCB specimens. The range of energy release rates (fracture energy) for TDCB specimen was 2 to 3 times higher than that of a DCB specimen for all high strain rates. The fracture energy of automotive adhesive joints can be estimated using the experimental results in this study for the fracture toughness (GIC) under high rates of loading. The crack grows as the applied fracture energy exceeds the value of the critical energy release rate (GIC) at the crack tip. The energy release rate was calculated using the fracture mechanics formula. The key fracture mechanics parameter, the fracture energy GIC, was ascertained as a function of the test rate and can be used to assess and model the overall joint performance. 相似文献
177.
G. Y. Zhang X. W. Zhao J. X. Qiang F. Tian L. Yang 《International Journal of Automotive Technology》2012,13(4):679-686
A novel regulation system for a vehicle generator and lead-acid battery is proposed in this paper. By integrating the regulation method, the output voltage of the generator is determined and controlled by the algorithm to save electrical energy and protect the lead-acid battery. The regulation algorithm is implemented in Matlab/Simulink, and the logic function of the system is verified using the dSPACE/AutoBox workbench. The experimental results show that the new algorithm improves the performance of the fuel economy of the vehicle and the battery state-of-health compared to the traditional control method. 相似文献
178.
This study compares the optimum designs of center pillar assembly with advanced high-strength steel (AHSS) to that of conventional
steel for crashworthiness and weight reduction in side impacts. A simplified side impact analysis method was used to simulate
the crash behavior of the center pillar assembly with efficient computing time. Thickness optimization aims to perform an
S-shaped deformation of the center pillar toward the cabin to reduce the injury level of a driver in a crash test. Center
pillar members were regarded as an assembly of parts that are fabricated with tailor-welded blanks, and the thickness of each
part was selected as a design variable. The thickness variables of parts that have significant effects on the deformation
mechanism were extracted as the main design variables for thickness optimization based on the results of a sensitivity analysis
with design of experiments. The optimization condition was constructed to induce an S-shaped deformation mode and reduce the
weight of the center pillar assembly. An optimum design was obtained after several iterations with response surface methodology
(RSM). Optimization was first performed with conventional steel and then with AHSS with the same procedure to optimize the
crashworthiness of the center pillar assembly. After thickness optimization, optimum designs were applied to the full vehicle
analysis to evaluate the validity of the optimization scheme with the simplified side impact analysis method. Then, the crashworthiness
of optimum designs with conventional steel and AHSS were compared using the full vehicle analysis. This comparison demonstrates
that AHSS can be more effectively utilized than conventional steel to obtain a lightweight design of an auto-body with enhanced
crashworthiness. 相似文献
179.
J. H. Bae J. S. Kim B. C. Hwang W. B. Bae M. S. Kim C. Kim 《International Journal of Automotive Technology》2012,13(2):285-291
The warm shrink fitting process is generally used to assemble automobile transmission parts (shafts/gears). However, this
process causes a deformation in the addendum and dedendum of the gear depending on the fitting interference and gear profile,
and this deformation causes additional noise and vibration between the gears. To address these problems, the warm shrink fitting
process is analyzed by considering the error in the dimensional deformation of the addendum and dedendum found when comparing
the results of a theoretical analysis and finite element analysis (FEA). A correction coefficient that reduces this error
is derived through an analysis of the difference in the cross-sectional area between the shapes used for the theoretical analysis
and that of the actual gear, and a closed-form equation to predict the dimensional deformation of the addendum and dedendum
is proposed. The FEA method is proposed to analyze the thermal-structural-thermal coupled field analysis of the warm shrink
fitting process (heating-fitting-cooling process). To verify the closed-form equation using the correction coefficient, measurements
are made of actual helical gears used in automobile transmissions. The results are in good agreement with those given by the
closed-form equation. 相似文献
180.