全文获取类型
收费全文 | 1207篇 |
免费 | 12篇 |
专业分类
公路运输 | 632篇 |
综合类 | 24篇 |
水路运输 | 245篇 |
铁路运输 | 26篇 |
综合运输 | 292篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 46篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 99篇 |
2017年 | 68篇 |
2016年 | 154篇 |
2015年 | 11篇 |
2014年 | 57篇 |
2013年 | 47篇 |
2012年 | 82篇 |
2011年 | 161篇 |
2010年 | 151篇 |
2009年 | 60篇 |
2008年 | 100篇 |
2007年 | 51篇 |
2006年 | 11篇 |
2005年 | 12篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有1219条查询结果,搜索用时 46 毫秒
891.
Properties of the active power/angle sub-matrix in the power flow Jacobian for power system analysis are studied. The sub-matrix is a dominant and irreducible matrix under very general conditions of power systems, so that it is invertible. Also the necessary conditions for its singularity are given. These theoretical results can be used to clarify the ambiguous understanding of the sub-matrix in current literature, and also provide the theoretical foundations for the applications based on reduced power flow Jacobian. Numerical simulation on the IEEE 118-bus power system is used to illustrate our results. 相似文献
892.
Effect of residual stress on impact damage in a dissimilar laminated plate at a biaxial bending mode
S. Y. Oh 《International Journal of Automotive Technology》2008,9(3):347-352
Systematic investigations have been performed on the mechanisms that lead to impact damage in a dissimilar laminated plate
with a thermal residual stress at a biaxial bending mode. Glass/polymer laminated plates are often used as blast-proof safety
screens, and bullet-proof windows, and in windshields in the automotive and the aerospace and aeronautical fields. Their many
advantages, the development of new materials, and the need for high-performance, low-weight structures ensure that laminated
plate construction will continue to be in demand. In this work, the impact damage in glass/Al alloy laminated circular plates
cured at RT and 80°C was investigated using an instrumented long bar impact tester at a biaxial bending mode. A circular plate
was cured at different curing temperatures to form a thermally induced residual stress at the bonding interface. To improve
the damage tolerance of laminated circular plates, various geometric (thickness ratio of the inner to outer layer) and material
parameters are considered by determining their effects of maximizing impact absorbed energy. The measured impact force profiles
and the impulse of the force explained the impact damage behaviors induced in the laminated circular plates. We show that
a compressive residual stress could reduce the initiation of radial cracks and the impact damaged area of the laminated plate
in the outer layer. Greater an inner layer thickness results in smaller a damaged area. A design guideline for effective dissimilar
laminated plate construction is proposed. 相似文献
893.
A. Stotsky 《International Journal of Automotive Technology》2008,9(3):289-295
A new computationally efficient filtering algorithm based on the Kaczmarz projection method for reconstruction of the first
harmonic of a periodic signal is presented. The algorithm allows the recovery of combustion quality information from noise-contaminated
engine speed measurements. The algorithm is verified using a spark-ignition six-cylinder engine in the torque estimation problem. 相似文献
894.
U. B. Azimov E. A. Roziboyev K. S. Kim D. S. Jeong Y. G. Lee J. E. Yun 《International Journal of Automotive Technology》2008,9(5):523-534
In this study, a visual investigation of sprays and flames is performed, and soot formation in Diesel-GTL fuel blends is studied
in a specially designed quiescent constant-volume chamber under various ambient gas temperatures and O2 concentrations. Similar to the case of soot formation during diesel fuel combustion, the sooting zone during the mixing-controlled
combustion of Diesel-GTL blends is located in the leading portion of the jet boundaries. Auto-ignition delay and soot concentration
decrease with an increase of GTL content in the fuel blend. Soot also decreases with lower O2 concentration, higher injection pressure, and lower ambient gas temperature. The lack of soot formation at lower O2 concentrations and lower temperatures suggests that Diesel-GTL fuel blends can be successfully utilized in low-temperature
diesel combustion technologies that are currently being developed. Furthermore, this mixing controlled combustion method with
Diesel-GTL blends can be used to modulate various engine operation parameters, and therefore to simultaneously reduce the
formation of soot and NOx within a wide range of diesel engine loads. 相似文献
895.
The need for the unmanned ground combat vehicle (UGCV), which is used for the surveillance, reconnaissance and targeting during
extremely dangerous condition on the battlefield, has steadily increased, and the transition from manned ground combat vehicles
to unmanned ground combat vehicles is expected to reduce the loss of lives during battle. The UGCV needs many types of capabilities
to achieve satisfactory performance. This paper focuses on the modeling and control of the power system of the UGCV, and proposes
the fuel cell hybrid system (FCHS) for the power system of the UGCV. The fuel cell hybrid system has many advantages in stealth
drive and the system efficiency. In addition, the FCHS is much quieter than the engine generator and generates much less heat.
The benefits of the FCHS are advantageous for use in Army operations, which require ‘silent watch’ capability and the ability
to operate without showing up on an enemy’s radar screen. The FCHS has a fuel cell and uses an energy storage system (ESS)
as a power source. The ESS (e.g., batteries or ultracapacitors) helps the fuel cell supply power to the electric drive system
and also recovers energy during deceleration. The ESS makes it possible to improve the efficiency and dynamic characteristic
of the power system. In this paper, the FCHS is composed of different combinations of component models. The component sizes
are chosen to satisfy performance requirements. In order to determine the power distribution between the fuel cell and the
ESS, a power management strategy based on the required power and the SOC (state of charge) of the ESS is proposed. Batteries
and ultracapacitor, components of the ESS, have different characteristics. Accordingly, varying the combination of ESS components
can change the performance of the power system. The performance of the FCHS with respect to different combinations of ESS
is analyzed using simulated results. 相似文献
896.
In this paper, a novel controller, the fractional order PDμ controller, is designed to improve the performance of the driver-vehicle system. First, fractional calculus and fractional
order PIλDμ controller are introduced. A control algorithm for vehicle directional control using the fractional order PDμ controller is then presented. Based on preview-follower theory, the on-line tuning method of the fractional order PDμ controller is designed. By comparing simulated and experimental results, the validity and robustness of the proposed fractional
order PDμ controller in the closed loop system are verified. Finally, comprehensive evaluations are performed between the systems with
the fractional order PDμ controller and with an integer PD controller. The results demonstrate that the use of the fractional order controller leads
to an improvement of the performance of the driver-vehicle system. 相似文献
897.
Combined control of a regenerative braking and antilock braking system for hybrid electric vehicles 总被引:1,自引:0,他引:1
D. Peng Y. Zhang C. -L. Yin J. -W. Zhang 《International Journal of Automotive Technology》2008,9(6):749-757
Most parallel hybrid electric vehicles (HEV) employ both a hydraulic braking system and a regenerative braking system to provide
enhanced braking performance and energy regeneration. A new design of a combined braking control strategy (CBCS) is presented
in this paper. The design is based on a new method of HEV braking torque distribution that makes the hydraulic braking system
work together with the regenerative braking system. The control system meets the requirements of a vehicle longitudinal braking
performance and gets more regenerative energy charge back to the battery. In the described system, a logic threshold control
strategy (LTCS) is developed to adjust the hydraulic braking torque dynamically, and a fuzzy logic control strategy (FCS)
is applied to adjust the regenerative braking torque dynamically. With the control strategy, the hydraulic braking system
and the regenerative braking system work synchronously to assure high regenerative efficiency and good braking performance,
even on roads with a low adhesion coefficient when emergency braking is required. The proposed braking control strategy is
steady and effective, as demonstrated by the experiment and the simulation. 相似文献
898.
H. N. Kim T. J. Kim B. C. Choi M. T. Lim 《International Journal of Automotive Technology》2008,9(5):563-570
The objective of this experimental study is to investigate the characteristics of the size distribution and the number concentration
of PM (particulate matters) emitted from the diffusion flame of a boiler burner, which has the same type of combustion as
a diesel engine. This study is performed to investigate the emission characteristics of nanoparticles generated from diffusion
combustion in diesel fuel, and it considered fuel factors and the reaction characteristics of the nanoparticles on the DOC
(Diesel oxidation catalyst). The factors examined in this experiment included the sulfur content in the fuel, the blend of
the diesel fuel containing biodiesel and bio-ethanol, and the concentration of engine oil (0.1% and 1.0%) blended with diesel
fuel. The particle size distribution of the nanoparticles exhausted from the boiler burner was measured by an SMPS (scanning
mobility particle sizer). The number concentration of PM that were smaller than 70 nm in diameter greatly increased in the
rear of the DOC when fuel containing 250 ppm of sulfur was used. The experiment also suggested that the particle number concentration
in both the front and rear of the DOC was lower when ULSD (ultra low sulfur diesel) fuel blended with biodiesel and bio-ethanol,
which are oxygenated fuels, was used than when only ULSD fuel was used. The higher the content of engine oil in the fuel,
the higher the particle number concentration was in the front and rear of the catalyst. When the first dilution air temperature
is increased from 30°C to 180°C, the nanoparticle number concentration dramatically dropped in the rear of the catalyst when
fuel containing 250 ppm of sulfur was used, while the particle size distribution remained almost the same when the fuel with
engine oil was used. 相似文献
899.
A robust H
∞ preview control is investigated for an active suspension system with look-ahead sensors. The uncertain system is described
by a state-space model with linear nominal parts and additional nonlinear time-varying norm-bounded uncertainties. Proof of
robust stability and a feedback-type robust H
∞ preview controller are derived by augmenting the dynamics of the original system and previewed road input. As, however, the
augmented previewed road input gives the system a much larger dimension than the original system, much more computation time
is required for solving of Riccati equations. To resolve this problem, a decomposed robust H
∞ preview controller is proposed. Robust stability and performance variations for system uncertainties are shown using a numerical
example of a quarter-car model. 相似文献
900.
Y. -S. Choi J. -G. Kim Y. -S. Kim J. -Y. Huh 《International Journal of Automotive Technology》2008,9(5):625-631
This project evaluated the corrosion damage over a five-year period of organic coated steels in automotive chassis parts during
P/G and field tests using electrochemical impedance spectroscopy (EIS) in a 3.5 wt.% NaCl solution. EIS can provide both quantitative
kinetic and mechanistic information about the performance of organic coating/metal systems. The difference in coating performance
between the P/G and field test specimens was assessed in relation to the impedance parameters. In particular, it was found
that the coating resistance and charge transfer resistance could be used to estimate the difference in corrosion damage between
the P/G and field test specimens. The coating performance of the P/G and field test specimens was visually evaluated using
SEM. The mechanism of corrosion occurring in the P/G test was similar to that taking place in the field test. The field test
environment was about ten times as corrosive as the P/G environment in terms of the electrochemical impedance parameters and
surface analysis. 相似文献