全文获取类型
收费全文 | 1995篇 |
免费 | 8篇 |
专业分类
公路运输 | 529篇 |
综合类 | 58篇 |
水路运输 | 665篇 |
铁路运输 | 54篇 |
综合运输 | 697篇 |
出版年
2022年 | 21篇 |
2021年 | 14篇 |
2020年 | 16篇 |
2019年 | 14篇 |
2018年 | 44篇 |
2017年 | 44篇 |
2016年 | 69篇 |
2015年 | 25篇 |
2014年 | 55篇 |
2013年 | 305篇 |
2012年 | 91篇 |
2011年 | 95篇 |
2010年 | 93篇 |
2009年 | 83篇 |
2008年 | 94篇 |
2007年 | 57篇 |
2006年 | 45篇 |
2005年 | 49篇 |
2004年 | 34篇 |
2003年 | 45篇 |
2002年 | 37篇 |
2001年 | 33篇 |
2000年 | 28篇 |
1999年 | 32篇 |
1998年 | 59篇 |
1997年 | 34篇 |
1996年 | 34篇 |
1995年 | 29篇 |
1994年 | 20篇 |
1993年 | 28篇 |
1992年 | 26篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 20篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 12篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1975年 | 20篇 |
1974年 | 17篇 |
1973年 | 10篇 |
排序方式: 共有2003条查询结果,搜索用时 0 毫秒
991.
Audrey de Nazelle Daniel A. Rodríguez 《Transportation Research Part D: Transport and Environment》2009,14(4):255-263
A microsimulation of individuals’ activities is used in the context of a risk analysis framework to assess the impacts of hypothesized changes to the built environment on personal energy expenditure and on inhalation of air pollutants. Uncertainty is assessed using Monte Carlo simulations and sensitivity analyzes. We find both simulated individuals that augment and others that reduce their energy expenditure and inhalation dose of pollutants, with median increases displaying larger magnitudes than the decreases. Up to 75% of the population has significant increases in energy expenditure and pollutant inhalation. We also find, however, high uncertainty associated with the estimates. Results differ considerably depending on the travel mode choice model used in the simulation. 相似文献
992.
P. Laurence M. Basset P. Coutant G. Gissinger 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2000,34(5):357-379
This paper presents an original method for the aggregation of transverse behaviour indicators obtained first from a subjective assessment then from an objective one of different vehicles tested under normal working conditions. The Choquet integral is used with respect to fuzzy measures. The main advantage of this method is to take account of the existing interactions between the indicators: redundancy, complementarity, inde-pendence. When this tool is used for subjective and objective evaluations, the computation methods of the objective indicators can be validated. Moreover, the influence of the human factor in the judgment of vehicle behaviour is easier to understand. 相似文献
993.
The external morphology of the first three larval stages of Nucellicola holmanae is described. These stages were cultured from eggs found with the adults in the viscera of dog whelks collected from Robin Hood's Bay, North Yorkshire. The nauplius develops within the whelk. It moults to a metanauplius which is released as a free-swimming stage. The metanauplius moults to a free copepodid stage which exhibits a combination of characters typical of the first, second and third copepodid stages of other poecilostomatoid copepods. The infective copepodid stage which locates and penetrates the host is visible through the integument of this free-swimming copepodid. 相似文献
994.
A framework for developing object-oriented software in transport modelling in proposed and demonstrated with the implementation of the calculation of road traffic noise (CORTN). Major tasks in the life cycle of an object-oriented development process are identified, and illustrated with the implementation of TRANSOOP – a software library containing 33,000 lines of C++ programming code. Software re-use from this library to produce a object-oriented noise program is compared with conventional computer programming shows that almost 90 per cent of the lines of code were drawn from TRANSOOP. Advantages of the object-oriented approach are discussed. 相似文献
995.
H. -H. Hinrichsen M. St.John A. Lehmann B. R. MacKenzie F. W. Kster 《Journal of Marine Systems》2002,32(4)
Variations in oxygen conditions below the permanent halocline influence the ecosystem of the Baltic Sea through a number of mechanisms. In this study, we examine the effects of physical forcing on variations in the volume of deep oxygenated water suitable for reproductive success of central Baltic cod. Recent research has identified the importance of inflows of saline and oxygenated North Sea water into the Baltic Sea for the recruitment of Baltic cod. However, other processes have been suggested to modify this reproduction volume including variations in timing and volume of terrestrial runoff, variability of the solubility of oxygen due to variations in sea surface temperature as well as the influence of variations in wind stress. In order to examine the latter three mechanisms, we have performed simulations utilizing the Kiel Baltic Sea model for a period of a weak to moderate inflow of North Sea water into the Baltic, modifying wind stress, freshwater runoff and thermal inputs. The model is started from three-dimensional fields of temperature, salinity and oxygen obtained from a previous model run and forced by realistic atmospheric conditions. Results of this realistic reference run were compared to runs with modified meteorological forcing conditions and river runoff.From these simulations, it is apparent that processes other than major Baltic inflows have the potential to alter the reproduction volume of Baltic cod. Low near-surface air temperatures in the North Sea, the Skagerrak/Kattegat area and in the western Baltic influence the water mass properties (high oxygen solubility). Eastward oriented transports of these well-oxygenated highly saline water masses may have a significant positive impact on the Baltic cod reproduction volume in the Bornholm Basin.Finally, we analysed how large scale and local atmospheric forcing conditions are related to the identified major processes affecting the reproduction volume. 相似文献
996.
Michael G H Bell 《先进运输杂志》2002,36(3):231-242
In‐vehicle information has an important social role to play in improving the efficiency and safety of travel by all modes. In this review, three generations of system are identified. The first generation consists of simple in‐vehicle units relying heavily on external data. The second generation has more sophisticated in‐vehicle units with colour TFT screens and DVD players for maps and entertainment. The third generation again makes use of external data, using the mobile phone network to download map sections and other data as and when required, thereby obviating the need for beacons and map CDs. For locationing, GPS (and/or Galileo, the European version of GPS) remains the favoured technology. Portable devices offering multi‐modal information could improve inter‐modal transport efficiency. 相似文献
997.
Kaiyu Chen David G. Beale 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,39(3):227-244
Summary A MacPherson suspension mechanism is modeled as a two degrees of freedom spatial mechanism. Its dynamic response under two excitement forces is simulated with the motion equations in Euler Parameters with the off-the-center-of-mass body-fixed coordinates derived in this paper. Simulation results are sampled and input into a numerical estimation routine based on singular value decomposition (SVD). Accurate numerical estimation results are achieved. A set of base dynamic parameters in symbolic expressions is also derived from the numerical results utilizing the concepts of mass transfer and moments of inertia transfer. This makes it possible to apply the estimation results to any MacPherson suspension mechanism with the same joint configuration. The potential applications of the symbolic base dynamic parameters in suspension design are also considered. 相似文献
998.
Direct Computation of the Performance Index for an Optimally Controlled Active Suspension with Preview Applied to a Half-Car Model 总被引:1,自引:0,他引:1
A. G. Thompson C. E. M. Pearce 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2001,35(2):121-137
A quadratic integral performance index is defined for a linear active preview-type suspension and a series of matrix expressions derived for its evaluation by means of MATLAB or some similar computer program in the case of a unit step input to the system. The computation, which is both fast and accurate compared to simulation, requires the solution of Lyapunov- and Riccati-type equations. Some examples of numerical computation are given and these show excellent agreement with published results. The conclusion features a useful computer program. 相似文献
999.
Recent developments in residential location choice models have considered the individual as the basic unit of analysis and have attempted to model the actual choice process used by individuals in selecting residential location sites. This paper demonstrates that the choice model derived from these studies is a more general form of many macroscopic models of location used in the past. The prime difference between the two classes of model is seen to be the much wider range of factors and geographic settings which can be accounted for in disaggregate behavioural models of residential location choice. 相似文献
1000.