全文获取类型
收费全文 | 1862篇 |
免费 | 0篇 |
专业分类
公路运输 | 184篇 |
综合类 | 656篇 |
水路运输 | 653篇 |
综合运输 | 369篇 |
出版年
2019年 | 1篇 |
2018年 | 334篇 |
2017年 | 290篇 |
2016年 | 247篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 55篇 |
2011年 | 205篇 |
2010年 | 213篇 |
2009年 | 45篇 |
2008年 | 176篇 |
2007年 | 121篇 |
2006年 | 1篇 |
2005年 | 50篇 |
2004年 | 41篇 |
2003年 | 55篇 |
2002年 | 16篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1862条查询结果,搜索用时 345 毫秒
651.
Modeling residential sorting effects to understand the impact of the built environment on commute mode choice 总被引:5,自引:2,他引:3
Abdul Rawoof Pinjari Ram M. Pendyala Chandra R. Bhat Paul A. Waddell 《Transportation》2007,34(5):557-573
This paper presents an examination of the significance of residential sorting or self selection effects in understanding the
impacts of the built environment on travel choices. Land use and transportation system attributes are often treated as exogenous
variables in models of travel behavior. Such models ignore the potential self selection processes that may be at play wherein
households and individuals choose to locate in areas or built environments that are consistent with their lifestyle and transportation
preferences, attitudes, and values. In this paper, a simultaneous model of residential location choice and commute mode choice
that accounts for both observed and unobserved taste variations that may contribute to residential self selection is estimated
on a survey sample extracted from the 2000 San Francisco Bay Area household travel survey. Model results show that both observed
and unobserved residential self selection effects do exist; however, even after accounting for these effects, it is found
that built environment attributes can indeed significantly impact commute mode choice behavior. The paper concludes with a
discussion of the implications of the model findings for policy planning.
相似文献
Paul A. WaddellEmail: |
652.
The thermal energy storage phase change material used for building has been prepared with a few of fatty acids based on the
principle of binary low eutectic point. The thermal behaviors such as phase transition temperature and enthalpy of compound
energy storage material are researched through differential scanning calorimeter (DSC) and scanning electron microscope (SEM).
The results show that the thermal energy storage phase change composite material can be used in the wall panels well as its
higher latent heat. 相似文献
653.
The dynamic recrystallization(DRX) behaviors in SPHC steel were investigated with hot compression tests at deformation temperatures of 950-1 150,strain rates of 0.1-15 s-1,and initial austenite grain sizes of 86-232 μm.The effects of deformation temperature,strain,strain rate and the initial austenite grain size on the microstructural evolution during DRX were studied in detail.The results show that DRX is observed under the condition of the Zener-Hollomon parameter being less than 1.07×10 13 s-1.The deformation activation energy for SPHC steel is calculated to be 299.4 kJ/mol by regression analysis.Austenite grain size of DRX is refined with decreasing temperature and increasing strain rate under steady state conditions,but it is not influenced by the initial grain size.The mathematical equation of DRX grain size of SPHC steel is obtained. 相似文献
654.
The micro-crystalline diamond (MCD) and fine-grained diamond (FGD) films are deposited on commercial silicon nitride inserts
by the hot-filament chemical vapor deposition (HFCVD) method. The friction and cutting properties of as-deposited MCD and
FGD films coated silicon nitride (Si3N4) inserts are comparatively investigated in this study. The scanning electron microscopy (SEM) and Raman spectroscopy are
adopted to study the characterization of the deposited diamond films. The friction tests are conducted on a ball-on-plate
type reciprocating friction tester in ambient air using Co-cemented tungsten carbide (WC-Co), Si3N4 and ball-bearing steel (BBS) balls as the mating materials of the diamond films. For sliding against WC-Co, Si3N4 and BBS, the FGD film presents lower friction coefficients than the MCD film. However, after sliding against Si3N4, the FGD film is subject to more severe wear than the MCD film. The cutting performance of as-deposited MCD and FGD coated
Si3N4 inserts is examined in dry turning glass fiber reinforced plastics (GFRP) composite materials, comparing with the uncoated
Si3N4 insert. The results indicate that the lifetime of Si3N4 inserts can be prolonged by depositing the MCD or FGD film on them and the FGD coated insert shows longer cutting lifetime
than the MCD coated one. 相似文献
655.
This paper presents an application of strut-and-tie model (STM) to design the interior anchorage zone (IAZ) in the post-tensioned
concrete structure. The STM theory and range of IAZ are introduced. Then, based on the finite element analysis, a series of
simplified equations to calculate internal forces in IAZ are presented. Finally, the STM model for IAZ is given. In the proposed
STM model, internal forces in ties vary with the dimension ratio and the eccentricity of load. The U-turn of internal forces
is suggested to allocate rebar to resist bearing flexural tensile force. Compared with the FIP (International Federation for
Prestressing) model, the proposed STM model is more reasonable and applicable. 相似文献
656.
Phase space can be constructed for N equal and distinguishable binary subsystems which are correlated in a scale-invariant manner. In the paper, correlation coefficient
and reduced probability are introduced to characterize the scale-invariant correlated binary subsystems. Probabilistic sets
for the correlated binary subsystems satisfy Leibnitz triangle rule in the sense that the marginal probabilities of N-system are equal to the joint probabilities of the (N −1)-system. For entropic index q ≠ 1, nonextensive entropy S
q
is shown to be additive in the scale-invariant occupation of phase space. 相似文献
657.
Petal failure characteristics of a conical projectile penetrating a thin plate at high oblique angle
In order to determine the impact depth of a conical projectile impacting a thin plate at high oblique angle, the residual
velocity of the projectile after penetrating must be known. Based on the petal failure mode of the conical projectile impacting
the thin plate at high oblique angle, the energy consumption mode of the target was determined. During the perforation process,
the energy consumption of the target was completed by the saucerization, the power work of the petals, the propagation of
radial cracks and petal bending. The energy formula was deduced for each energy dissipation mode and the energy consumed in
the impact process was determined. The residual velocity and the ballistic limit velocity of the projectile were deduced by
energy conservation principle. Comparison of the analytical results of the residual velocity to the numerical results demonstrates
the accuracy and reliability of the analytical formula. 相似文献
658.
A new solution to the inverse position analysis of the redundant serial robot is presented. The inverse position analysis
problem of the redundant serial robot is transformed into a minimization problem and then the optimization method is adopted
to solve the nonlinear least square problem with the analytic form of a new Jacobi matrix. In this way, the inverse solution
of the redundant serial robot can be searched out quickly under the desired precision when the positions of the three non-collinear
end effector points are given. The inverse position analysis of the 7R redundant serial robot is illustrated as an example
and the simulation results verify the efficiency of the proposed algorithm. 相似文献
659.
The steered covariance matrix (STCM) and its inverse matrix should be calculated in each beam for steered minimum variance
(STMV). The inverse matrix needs complex computation and restricts its application in engineering. Combining the integration
character of one-phase regressive filter with the iterative formula of inverse matrix, an STMV iterative algorithm is proposed.
The computational cost of the iterative algorithm is reduced approximately to be 2/M times of the original one when there are M sensors, and is more advantaged for the realization of the algorithm in real time. Simulation results show that the STMV
iterative algorithm can preserve the characters of STMV on high azimuth resolution and weak target detection while the computational
cost reduced sharply. The analysis on sea trial data proves that the proposed algorithm can estimate each target’s azimuth
even when the source powers differ in large scales or their bearings are very approximate. 相似文献
660.
Turbulence enhancement by particle wake effect is studied by numerical simulation of gas turbulent flows passing over particle
under various particle sizes, inlet gas velocities, gas viscosity, gas density and the distance of particles. By performing
dimension analysis and using the form of gas-particle interaction source term for reference, a new semi-empirical turbulence
enhancement model by the particle-wake effect is proposed. The turbulence model is then incorporated into second-order moment
model for simulating gas-particle flows in a horizontal channel with different wall roughness and a sudden-expansion chamber.
The results show that this model is with higher calculating accuracy than another two turbulence models in comparison with
the experimental results. 相似文献