全文获取类型
收费全文 | 1426篇 |
免费 | 22篇 |
专业分类
公路运输 | 568篇 |
综合类 | 45篇 |
水路运输 | 372篇 |
铁路运输 | 48篇 |
综合运输 | 415篇 |
出版年
2023年 | 14篇 |
2022年 | 38篇 |
2021年 | 13篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 29篇 |
2017年 | 38篇 |
2016年 | 64篇 |
2015年 | 21篇 |
2014年 | 72篇 |
2013年 | 193篇 |
2012年 | 78篇 |
2011年 | 75篇 |
2010年 | 82篇 |
2009年 | 98篇 |
2008年 | 72篇 |
2007年 | 41篇 |
2006年 | 32篇 |
2005年 | 35篇 |
2004年 | 24篇 |
2003年 | 23篇 |
2002年 | 26篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 19篇 |
1998年 | 14篇 |
1997年 | 17篇 |
1996年 | 20篇 |
1995年 | 25篇 |
1994年 | 12篇 |
1993年 | 19篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 15篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 12篇 |
1976年 | 15篇 |
1975年 | 18篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 4篇 |
排序方式: 共有1448条查询结果,搜索用时 343 毫秒
261.
Griet De Backer Marc Vantorre Peter Frigaard Charlotte Beels Julien De Rouck 《Journal of Marine Science and Technology》2010,15(2):119-130
Oscillating point absorber buoys may rise out of the water and be subjected to bottom slamming upon re-entering the water.
Numerical simulations are performed to estimate the power absorption, the impact velocities and the corresponding slamming
forces for various slamming constraints. Three buoy shapes are considered: a hemisphere and two conical shapes with deadrise
angles of 30° and 45°, with a waterline diameter of 5 m. The simulations indicate that the risk of rising out of the water
is largely dependent on the buoy draft and sea state. Although associated with power losses, emergence occurrence probabilities
can be significantly reduced by adapting the control parameters. The magnitude of the slamming load is severely influenced
by the buoy shape. The ratio between the peak impact load on the hemisphere and that on the 45° cone is approximately 2, whereas
the power absorption is only 4–8% higher for the 45° cone. This work illustrates the need to include slamming considerations
aside from power absorption criteria in the buoy shape design process and the control strategy. 相似文献
262.
关于铁路隧道内安全的新UIC规程适用于新建和既有隧道。该规程制定了可靠的基础设施、车辆和运输调度措施来提高隧道内的安全性,尤其注意了隧道内的防火问题。 相似文献
263.
Peter.J.Fox 《汽车杂志》2010,(5):196-199
“如果2009年的开局并不是我们现在所看到的,我认为我们已经驾驶着RB5赢得了世界冠军,因为我们有F1里最的底盘”。克里斯蒂安·霍纳如是说。 相似文献
264.
The importance of vehicle safety cannot be exaggerated in today’s mobile societies. Many manufacturers, associates related
to vehicles and universities make an effort to improve vehicle safety by developing new technologies, applying high strength
steel to the body structure etc. However, the majority of these efforts are focused on decreasing injury. It is absolutely
important to minimize injury, but a more important aspect is coping with vehicle accidents. That is, As undeniably important
as it is to minimize potential injuries, it is critical that experts focus on developing ways to keep drivers out of situations
likely to lead to crashes in the first place. The purpose of this paper is to determine what the most critical factor is when
coping with an unfamiliar driving situation. The answer is to provide a wide-open field of vision, especially for the driver.
The driver’s field of vision is obstructed by the vehicle’s A-pillar. To solve this, the A-pillar obstruction angle, which
is the angle between the driver’s eyes and the A-pillar should be decreased. This paper purposes three-methods for decreasing
this angle structurally and applying a slim A-pillar which is as the best solution to decrease the A-pillar obstruction angle
and ensure the drivers field of vision at the same time 相似文献
265.
This paper explores issues related to the electrical safety of Hybrid Electrical Vehicles (HEVs) during and after various
crash events. Japanese and American federal regulations regarding occupant protection against high voltages in Electric Vehicles
(EVs) and HEVs were surveyed and analyzed in this study. Front, side and rear impact tests for two types of HEVs were conducted
to investigate electrolyte spillage, the retention of the propulsion battery system and the electrical isolation of the occupant.
The test results met the related criteria. The test procedures and the criteria for occupant protection established through
this study were amended to Korean Motor Vehicle Safety Standard (KMVSS) No. 91 to add the crash protection of the EVs and
the HEVs. 相似文献
266.
H. J. Kim B. Han W. S. Hong W. H. Shin G. B. Cho Y. K. Lee Y. J. Kim 《International Journal of Automotive Technology》2010,11(4):447-453
A 3000 cc diesel engine attached to an engine dynamo was used to test three newly developed electrostatic Diesel Particulate
matter filtration Systems (DPS 1, 2, and 3) under four steady-state engine operating conditions: idle, 2000 rpm with no load,
and 2000 rpm under 25% and 50% loads. Of the two developed alternatives, DPS 1 and DPS 2, DPS 2 comprises an ionization section,
electrostatic field additional section and Flow-Through Filter (FTF), which achieved almost 90% removal of particulate matter
(PM) under the engine’s operating conditions, and the efficiency of the FTF was maintained between 20% and 50%. Comparing
the long-term performance of DPS 2 and DPS 3 (effectively a serial combination of two DPS 2s) with a commercially-available
Diesel Particulate Filter (DPF), the DPS 2 and DPS 3 achieved almost the same efficiency for removing PM as the DPF but had
significantly improved (75%∼90% lower) differential pressure drops. 相似文献
267.
Fault detection method for electric parking brake (EPB) systems with sensorless estimation using current ripples 总被引:1,自引:0,他引:1
C. W. Lee H. B. Chung Y. O. Lee C. C. Chung Y. S. Son P. Yoon 《International Journal of Automotive Technology》2010,11(3):387-394
A fault detection method with parity equations is proposed in this paper. Due to its low cost implementation, the velocity
of the motor is not measurable in electric parking brake (EPB) systems. Therefore, residuals are not reliable when estimating
the motor velocity with a low-resolution encoder. In this paper, we propose a fault detection method with sensorless estimation
using current ripples that estimates the position and velocity of the motor by detecting periodical oscillations of the armature
current caused by rotor slots. In addition, this method can estimate the position and velocity of the motor with less computational
effort than a state observer. Moreover, the method is less sensitive to motor parameters than model-based estimation methods.
The effectiveness of this method is validated with experimental data, and the simulation results show that various faults
have their own residual patterns. Therefore, we can detect the presence of faults by monitoring the residual signals. 相似文献
268.
This paper describes the on-line debugging software developed by our research team. The software has five functions and can be helpful in achieving rapid development for hybrid electric buses. In addition, the software can monitor system states continuously and also modify parametric maps or update control programs using its on-line programming function. Based on the on-line debugging system, the hybrid propulsion control system is designed, and all the working modes of the hybrid electric bus are tested. Finally, experiments are carried out that verify that the debugging system is feasible and reliable. The test results show that the hybrid electric bus can reduce fuel consumption by about 19.1 percent, in comparison with conventional buses. 相似文献
269.
J. Kim J. Kang Y. Kim T. Kim B. Min H. Kim 《International Journal of Automotive Technology》2010,11(4):565-571
The power split type hybrid system transmits engine power by dividing it into the electrical unit and the mechanical unit.
Its power transmission efficiency is highest at the mechanical point (MP), where the full power is transmitted to the mechanical
unit. In this study, the equation for the MP was derived for the gear ratios of a general 4-node lever model. The MP characteristics
for the transmission ratio (TR) of the input split and compound split structures were examined using the equation derived.
Using the examined input split and compound split structures, a systematic design method for the dual mode power split transmission
was proposed. In the dual mode power split transmission, the MP could be positioned at the desired TR, and the input split
and compound split modes could be selectively used according to the clutch combination, which leads to the operation of the
vehicle within a high system efficiency range. 相似文献
270.
We investigated the effects of injection parameters such as injection pressure, ambient pressure, and ambient temperature
on spray characteristics. We calculated the turbulence occurring point (t
c
), defined as the time required to generate a vortex, and the deceleration point (t
b
), defined as the time when spray penetration begins to decelerate, to elucidate the breakup mechanism of the test injectors.
The spray velocity coefficient (Cv) was obtained to evaluate the spray characteristics. As the ambient pressure increases in the case of a slit injector, Cv decreases. We investigated the effects of nozzle tip shape according to injection pressure, ambient pressure, and fuel properties
on spray characteristics and provide a Cv value of 0.38 for the swirl injector with a spray angle of 60° and the slit injector under atmospheric conditions. The value
of Cv in the case of a slit injector was reduced by increasing the ambient pressure. Our results suggest that Cv of a swirl injector is constant regardless of changes in ambient pressure, injection pressure, and fuel properties. On the
other hand, Cv of a slit injector is altered by changes in ambient pressure. 相似文献