全文获取类型
收费全文 | 474篇 |
免费 | 4篇 |
专业分类
公路运输 | 163篇 |
综合类 | 89篇 |
水路运输 | 103篇 |
铁路运输 | 7篇 |
综合运输 | 116篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 2篇 |
2019年 | 14篇 |
2018年 | 22篇 |
2017年 | 26篇 |
2016年 | 42篇 |
2015年 | 49篇 |
2014年 | 31篇 |
2013年 | 48篇 |
2012年 | 99篇 |
2011年 | 13篇 |
2010年 | 8篇 |
2009年 | 13篇 |
2008年 | 10篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有478条查询结果,搜索用时 9 毫秒
451.
用高分辨率激波捕捉格式求解Euler方程时,不可避免地会用到间断面两侧的点,从而在间断面附近发生数值耗散,降低分辨率.此文应用一种虚拟区域,将LevelSet方法与高分辨率激波捕捉方法结合起来求解Euler方程,不使用间断面两侧的点,从而提高了分辨率.通过激波管问题的数值实验,可以看到这种方法的优越性. 相似文献
452.
段言志 《上海交通大学学报(英文版)》2009,14(4):510-512
This letter investigates the time-machine problem in perfect fluid cosmologies. It solves the Einstein's field equations with the energy-momentum tensors for perfect fluid and constructs a class of time-machine solutions,by which the time-machine problem in the perfect fluid cosmologies is solved. 相似文献
453.
当一条附合导线测距值中出现明显的系统误差时 ,设立尺度比未知数的条件平差法可削弱它对平差结果的影响。此法被证明是非常精确、有效和经济的 相似文献
454.
This article presents a nonlinear time-domain simulation method for the prediction of large-amplitude motions of a Ro–Ro
ship in regular oblique waves in an intact and a damaged condition. Numerical computations and model tests have been carried
out to investigate the dynamic motion responses of Ro–Ro ship Dextra to various wave amplitudes at three different wave headings. The results of numerical and experimental investigations for
stern quartering waves are reviewed. Comparisons between predictions and measurements show good agreement except in the roll-resonant
region. Nonlinear effects are significant in horizontal modes of motion, and resonant roll motion, and there is strong coupling
between all modes of motion in the roll-resonant region for large-amplitude responses. On the other hand, the time-domain
simulation technique suffers from numerical drift in horizontal modes of motion as wave amplitude increases. This is due to
nonlinear equations of motion and the lack of a restoring force and moment in horizontal motion.
Received: April 30, 2002 / Accepted: August 9, 2002
Acknowledgments. II Programme of the European Community Commission under contract No. BRPR-CT97-0513.
Address correspondence to: H.S. Chan (hoi-sang.chan@ncl.ac.uk) 相似文献
455.
This paper focuses on the tradeoff in time allocation between maintenance activities/travel and discretionary activities/travel.
We recognize that people generally must travel a minimum amount of time in order to allocate one unit of time to the activity.
This minimum amount of travel is represented by the travel time price, a ratio obtained by dividing the total amount of time
traveling to maintenance or discretionary activities by the total amount of time spent on activities of the same type; it
is the time equivalent of the monetary price for performing an activity. Using the San Francisco Bay Area 1996 Household Travel
Survey data and applying the Almost Ideal Demand System (AIDS) of demand equations, we found that with respect to the time
equivalent of income elasticities of maintenance and discretionary activities, the former is less than unity and the latter
is greater than unity. In other words, maintenance activities are a necessity and discretionary activities are a luxury. With
respect to the own travel time price elasticities, if the travel time price of performing a certain type of activity increases
(for reasons such as traffic congestion), one would reduce the time allocated to that type of activity. Time spent on maintenance
activities is less elastic than the time spent on discretionary activities. As for the cross travel time price elasticities
(changes in time allocated to activity type i in responses to changes in the time price for activity type j), we found that ɛdm>0 and ɛmd>0, suggesting a substitution effect between maintenance and discretionary activities. 相似文献
456.
柳长茂 《西南交通大学学报(英文版)》2005,13(2)
Introduction Ampere,Faradayandotherphysicistsproposeda numberofexperimentallawsaboutelectromagnetism.OnthesebasesMaxwellestablishedMaxwell sequa tionsin1862.Meanwhile,accordingtomathematical theoreticalpointofview(consistencyofequations),hesupplementedelectromagnetismwithelectricdis placementvectors.Einsteinpointedoutthat,justaswhatthe ancientshadsaid,peoplemightgraspactualitybypure mathematicalthought.Butintheestablishmentof Maxwell sequations,mathematiciansplayedonlypar tiallyimportantrole… 相似文献
457.
石磊 《大连铁道学院学报》1991,(4)
本文研究了无穷时滞中立型泛函微分方程的解的局部理论.为了便于应用,得到了具无穷时滞中立型泛函微分方程的解的存在性、唯一性及关于初值的连续相依性. 相似文献
458.
The limited understanding of public–private partnerships (P3s) for transportation infrastructure finance has been generally attributed to a lack of data. The more fundamental question of how P3 data are utilized in the literature is more relevant and critical, but remains unclear. This study investigates this question by examining the linkages between research objectives and data characteristics through a meta-analysis of infrastructure P3 studies using multinomial regressions. It analyzes 95 empirical studies that adopt actual data, selected from a P3 research database that includes over 345 studies and are classified into five categories including performance, contract, risk, value for money, and institutional factors. Results show that the case studies are less frequently utilized to understand P3s' institutional issues compared to those that focus on P3s' performance or VFM. Survey data are more frequently used to study P3 contracts rather than issues related to P3 project risk. We highlight the need for policy-makers to require continuing disclosure of P3 performance for validating the effectiveness of the procurement model and to improve the practice. 相似文献
459.
Michal Maniowski 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(4):526-544
ABSTRACTThe paper presents an innovative method for a lap time minimisation by using genetic algorithms for a multi objective optimisation of a race driver–vehicle model. The decision variables consist of 16 parameters responsible for actions of a professional driver (e.g. time traces for brake, accelerator and steering wheel) on a race track part with RH corner. Purpose-built, high fidelity, multibody vehicle model (called ‘miMa’) is described by 30 generalised coordinates and 440 parameters, crucial in motorsport. Focus is put on modelling of the tyre tread thermodynamics and its influence on race vehicle dynamics. Numerical example considers a Rear Wheel Drive BMW E36 prepared for track day events. In order to improve the section lap time (by 5%) and corner exit velocity (by 4%) a few different driving strategies are found depending on thermal conditions of semi-slick tyres. The process of the race driver adaptation to initially cold or hot tyres is explained. 相似文献
460.