全文获取类型
收费全文 | 1878篇 |
免费 | 9篇 |
专业分类
公路运输 | 664篇 |
综合类 | 56篇 |
水路运输 | 577篇 |
铁路运输 | 51篇 |
综合运输 | 539篇 |
出版年
2023年 | 11篇 |
2022年 | 36篇 |
2021年 | 15篇 |
2020年 | 11篇 |
2019年 | 17篇 |
2018年 | 60篇 |
2017年 | 46篇 |
2016年 | 73篇 |
2015年 | 16篇 |
2014年 | 76篇 |
2013年 | 293篇 |
2012年 | 96篇 |
2011年 | 97篇 |
2010年 | 91篇 |
2009年 | 90篇 |
2008年 | 97篇 |
2007年 | 46篇 |
2006年 | 36篇 |
2005年 | 36篇 |
2004年 | 28篇 |
2003年 | 29篇 |
2002年 | 23篇 |
2001年 | 24篇 |
2000年 | 34篇 |
1999年 | 20篇 |
1998年 | 29篇 |
1997年 | 35篇 |
1996年 | 31篇 |
1995年 | 44篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 14篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 27篇 |
1980年 | 18篇 |
1979年 | 33篇 |
1978年 | 12篇 |
1977年 | 18篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 8篇 |
排序方式: 共有1887条查询结果,搜索用时 31 毫秒
981.
There has been recent interest in intelligent vehicle technologies, such as advanced driver assistance systems (ADASs) or
in-vehicle information systems (IVISs), that offer a significant enhancement of safety and convenience to drivers and passengers.
However, the use of ADAS- and IVIS-based information devices may increase driver distraction and workload, which in turn can
increase the chance of traffic accidents. The number of traffic accidents involving older drivers that are due to distraction,
misjudgment, and delayed detection of danger, all of which are related to the drivers’ declining physical and cognitive capabilities,
has increased. Because the death rate in traffic accidents is higher when older drivers are involved, finding ways to reduce
the distraction and workload of older drivers is important. This paper generalizes driver information device operations and
assesses the workload while driving by means of experiments involving 40 drivers in real cars under actual road conditions.
Five driving tasks (manual only, manual primarily, visual only, visual primarily, and visual-manual) and three age groups
(younger (20–29 years of age), middle-aged (40–49 years of age), and older (60–69 years of age)) were considered in investigating
the effect of age-related workload difference. Data were collected from 40 drivers who drove in a real car under actual road
conditions. The experimental results showed that age influences driver workload while performing in-vehicle tasks. 相似文献
982.
S. J. Kang M. F. Kader Y. D. Jun K. B. Lee 《International Journal of Automotive Technology》2011,12(1):39-44
Adequate visibility through the automobile windshield is of paramount practical significance, most often at very low temperatures
when ice tends to form on the windshield screen. But the numerical simulation of the defrost process is a challenging task
because phase change is involved. In this study numerical solution was computed by a finite volume computational fluid dynamics
(CFD) program and experimental investigations were performed to validate the numerical results. It was found that the airflow
produced by the defrost nozzle is highly nonuniform in nature and does not cover the whole windshield area. The nonuniformity
also severely affected the heating temperature pattern on the windshield. The windshield temperature reached a maximum in
the vicinity of the defroster nozzle in the lower part of the windshield and ranged from 9∼31°C over a period of 30 min, which
caused the frost to melt on the windshield. The melting time was under 10 minutes, which satisfied the NHTSA standard. The
numerical predictions were in close agreement with the experimental results. Thus, CFD can be a very useful design tool for
an automobile HVAC system. 相似文献
983.
C. -H. Lee J. -M. Lee M. -S. Choi C. -K. Kim E. -B. Koh 《International Journal of Automotive Technology》2011,12(2):193-198
Since the invention of automobiles, the need to know the braking performance of vehicles has been acknowledged. However, because
there are numerous design variables as well as nonlinearities in the braking system, it is difficult to predict the performance
accurately. In this paper, a computational program is developed to estimate the braking performance numerically. This synthetic
braking performance program accounts for pedal force, pedal travel and deceleration of braking parts, such as master cylinder,
booster, valve, brake pad, rotor, and hoses. To improve the accuracy of program, a semi-empirical model of a braking system
is introduced by using the empirical test data of pad compression, hose expansion and the friction coefficient between the
pad and rotor. The accuracy of the estimation is evaluated by comparing it to the actual vehicle test results. The developed
program is easy for the brake system engineers to manipulate and it can be used in the development of new vehicles by incorporating
the graphical presentations. 相似文献
984.
W. M. Choi J. S. Kim H. S. Jung T. S. Kwon 《International Journal of Automotive Technology》2011,12(3):383-389
As a crash energy absorber, a tube-type crash element (expansion tube) dissipates kinetic energy through the internal deformation
energy of the tube and through frictional energy. In this paper, the effects of the variation of punch angles on the energy-absorbing
characteristics of expansion tubes were studied by quasi-static tests using three punch angles (15°, 30°, and 45°). A finite
element analysis of the tube expanding process (m = τ
max
/K) was performed using a shear friction model to confirm the variation of the shear friction factor with respect to punch angles
using the inverse method. Additional analyses were performed using angles of 20°, 25°, 35°, and 40° to study the effect of
the punch angles on the internal deformation energy, frictional energy, and expansion ratio of the tubes. The results of the
experiment and finite element analysis showed that the shear friction factor was inversely proportional to the punch angles,
and a specific punch angle existed at which the absorbed energy and expansion ratio remained constant. 相似文献
985.
The accurate estimation of sideslip angle is necessary for many vehicle control systems. The detection of sliding and skidding
is especially critical in emergency situations. In this paper, a sideslip angle estimation method is proposed that considers
severe longitudinal velocity variation over the short period of time during which a vehicle may lose stability due to sliding
or spinning. An extended Kalman filter (EKF) based on a kinematic model of a vehicle is used without initialization of the
inertial measurement unit to estimate vehicle longitudinal velocity. A dynamic compensation method that compensates for the
difference in the locations of the vehicle velocity sensor and the IMU in on-road vehicle tests is proposed. Evaluations with
a CarSim™ 27-degree-of-freedom (DOF) model for various vehicle test scenarios and with on-road tests using a real vehicle
show that the proposed sideslip angle estimation method can accurately predict sideslip angle, even when vehicle longitudinal
velocity changes significantly. 相似文献
986.
Constant velocity universal joints play a very important role in automotive drivelines. The traditional development method,
based on a physical prototype and experimenting, is time consuming and costly. This test-based method does not easily identify
rational design clues. Therefore, a virtual product development method, which is based on dynamics modeling and simulation,
is necessary. Virtual prototyping for a universal joint has been developed using the simulation software package MSC.ADAMS.
Dynamics simulation has been performed to predict and evaluate joint behaviors. This virtual product development method has
been implemented by the WanXiang Group Co., which is one of the most famous Chinese automotive component manufacturers. 相似文献
987.
J. K. Kim Y. J. Kim W. H. Yang Y. C. Park K.-H. Lee 《International Journal of Automotive Technology》2011,12(3):375-381
This study proposes a structural design method for an outer tie rod installed in a passenger car. The weight of the outer
tie rod is optimized by using the aluminum alloy Al6082M, which is developed as a steel-substitute material, and applying
structural optimization techniques. The high strength aluminum with improved mechanical properties was developed to reduce
the weight of the outer tie rod. The newly developed aluminum alloy Al6082M is applied as the material of the outer tie rod.
The static strength due to inertia force, durability and buckling performances are considered in the structural design of
the outer tie rod. At the proto design stage of a new outer tie rod, it is cost-effective to utilize FE (finite element) analysis
to predict each of these performances. In addition, the current trend in the structural design of automobile parts is to use
optimization techniques to reduce the weights of the parts. First, for an arbitrary base design, the static strength, the
life cycle and the buckling load are calculated to check whether the design satisfies its criteria. Then, the critical performance
is selected so as to include its loading condition only in the optimization process. In this study, the metamodel based optimization
process using kriging is adopted to obtain the minimum weight satisfying the critical design requirement. Then, the feasibility
of the determined optimum shape is investigated against the other performances. Finally, the optimum design of outer tie rod
is modified by considering forging efficiency. The performances of the final design are investigated through simulation and
experiment. 相似文献
988.
M. J. L. Boada B. L. Boada D. Garcia-Pozuelo V. Diaz 《International Journal of Automotive Technology》2011,12(6):821-829
The behaviour of the tyre plays an important role in the vehicle handling. An accurate tyre model that estimates these forces
and moments it is highly essential for the studies of vehicle behaviour. For the last ten years neural networks have attracted
a great deal of attention in vehicle dynamics and control. Neural networks have been effectively applied to model complex
systems due to their good learning capability. In this paper a recursive lazy learning method based on neural networks is
considered to model the tyre characteristics under combined braking and cornering. The proposed method is validated by comparison
with experimental obtained responses. Results show the estimated model correlates very well with the data obtained experimentally.
Moreover, the neural model proposed allows to include the asymetric tyre behaviour in the tyre model without difficulty. 相似文献
989.
M. H. Lee H. M. Lee K. S. Lee S. K. Ha J. I. Bae J. H. Park H. G. Park H. J. Choi H. H. Chun 《International Journal of Automotive Technology》2011,12(5):733-744
In this paper, a hardware-in-the-loop simulation (HILS) system was developed before the development of an electric power steering
(EPS) system in a vehicle. This study was focused on the establishment of the HILS system. Driving conditions are simulated
with the HILS system. The actual steering input parameters are confirmed on the monitor while driving the HILS system. The
steering forces observed in the simulation with the developed HILS system are similar to those in real vehicle tests. The
developed HILS system can be applied in the development of various types of EPS systems. 相似文献
990.
An experiment was conducted to characterize the effects of SOF on EGR cooler fouling. A removable singletube test rig combined with a soot generator was developed to represent an EGR cooler and diesel exhaust gas. The use of a soot generator, which controlled the size and concentration of soot particles, enabled independent variables to be completely controlled. Either n-dodecane or diesel lube oil as substitute SOFs were vaporized and injected into the test rig to evaluate their effects on the growth of PM deposits and the degradation performance of the EGR cooler. Coolant temperature, which seemed to be associated with SOF content, was chosen as an independent variable, and PM deposit mass per unit area and the effectiveness drop versus time increased as the coolant temperature decreased. The PM deposit mass per unit area and effectiveness drop had maximum values at a coolant temperature of 40°C for every n-dodecane injection rate. For substitute SOFs tested in this experiment, the deposit mass increased when either n-dodecane or diesel lube oil was injected, but the effect of lube oil was more significant. Diesel lube oil seemed to have a stronger effect on the reduction of thermal conductivity by filling pores in the deposits. When diesel lube oil was injected, the deposit mass per unit area increased 127% compared to dry soot without injection. The effectiveness drop after 10 hours increased only 12.5%. 相似文献