全文获取类型
收费全文 | 3452篇 |
免费 | 31篇 |
专业分类
公路运输 | 984篇 |
综合类 | 172篇 |
水路运输 | 1146篇 |
铁路运输 | 139篇 |
综合运输 | 1042篇 |
出版年
2022年 | 53篇 |
2021年 | 27篇 |
2020年 | 28篇 |
2019年 | 39篇 |
2018年 | 80篇 |
2017年 | 97篇 |
2016年 | 126篇 |
2015年 | 48篇 |
2014年 | 118篇 |
2013年 | 543篇 |
2012年 | 172篇 |
2011年 | 190篇 |
2010年 | 154篇 |
2009年 | 171篇 |
2008年 | 158篇 |
2007年 | 112篇 |
2006年 | 83篇 |
2005年 | 89篇 |
2004年 | 55篇 |
2003年 | 62篇 |
2002年 | 54篇 |
2001年 | 53篇 |
2000年 | 57篇 |
1999年 | 40篇 |
1998年 | 54篇 |
1997年 | 56篇 |
1996年 | 65篇 |
1995年 | 74篇 |
1994年 | 22篇 |
1993年 | 38篇 |
1992年 | 38篇 |
1991年 | 34篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 25篇 |
1987年 | 26篇 |
1986年 | 22篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 25篇 |
1982年 | 23篇 |
1981年 | 35篇 |
1980年 | 33篇 |
1979年 | 34篇 |
1978年 | 32篇 |
1977年 | 26篇 |
1976年 | 19篇 |
1975年 | 29篇 |
1974年 | 19篇 |
1973年 | 18篇 |
排序方式: 共有3483条查询结果,搜索用时 812 毫秒
471.
C. E. M. Pearce 《Transportation Research Part B: Methodological》1981,15(6):427-435
An analytical study is made of the determination of the travel intensity at an arbitrary point of a city with a straight line barrier. For a given origin and destination a trip is made by the shortest path not crossing the barrier or the city perimeter. The joint trip end distribution is arbitrary except for a continuity assumption. 相似文献
472.
E. C. Mikulcik 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1980,9(5):281-289
The characteristic equation for a simple automobile-trailer combination is analyzed, revealing the parameter groups which are important in determining the stability characteristics. Application of Routh's method results in separate criteria for oscillatory and non-oscillatory criteria which can be evaluated algebraically, and which can also be displayed graphically showing a region of stability on a two-dimensional plot. The stability region is bounded by limits of oscillatory and non-oscillatory stability, and the evaluation of a specific case corresponds to the location of a point relative to the boundaries. 相似文献
473.
474.
E. Esmailzadeh 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1978,7(2):83-96
The transmission of road-generated vibrations into a vehicle body is treated as a source-path-receiver problem. The suspension system acts as the path, and improved isolation can be achieved by having a single compliant bushing at the connecting point of the shock absorber to the body with none at the other end. A mathematical model is derived for such a system which would enable detailed parameter investigation to be undertaken using the gradient method of optimization. An expression for the absolute displacement transmissibility of the body is derived and the optimization procedure is applied in order to evaluate the optimum values of the non-dimensional variables involved. This minimizes the maximum motion transmitted to the body from the road surface over a broad frequency range. Design data which are presented non-dimensionally for parameter variations show the influence of three variables: the bushing stiffness, the resonant frequency ratio and the damping coefficient upon the transmissibility. 相似文献
475.
Okechukwu C. Iheduru 《Maritime Policy and Management》1993,20(1):31-49
While recognizing the need for increased participation of the private sector in the maritime industry of developing countries, there is a need to go beyond the call for privatization in terms of mere change of ownership from state to private sector as the only solution to the inefficiency of the maritime industry in developing countries. This limited understanding of the maritime problems of these countries abounds in the literature on maritime privatization. This study departs from this approach and focuses on the political economy of the maritime industry, and suggests that maritime privatization will not necessarily result in increased efficiency of the divested maritime enterprises. Rather, it argues that maritime problems in these countries have less to do with ownership than with the structural constraints in world shipping together with internal management and local ~olitics. The maritime industrv in West and Central Africa is used as a case studv. and recommendations such as selective privatization, 'programme contract', and most importantly, corporatization, are suggested as alternative strategies that could enhance maritime privatization and the development of the maritime industry in developing countries. 相似文献
476.
房志宇 《西安交通大学学报(英文版)》1995,(2)
INVITROGLYCATIONOFHEMOGLOBIN(HB):CHOOSINGTHEAPPROPRIATEMODELFangZhiyu;R.R.Little,H.M.Wiedmeyer,D.E.Goldstein(DepartmentofChil... 相似文献
477.
Mohamed M. ELMADANY 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1988,17(4):193-210
Stochastic optimal control and estimation theories are used to design an active suspension system for a cab ride in a tractor-semitrailer vehicle. A discrete-continuous vehicle model with eleven degrees of freedom is augmented by a stochastic road excitation model and a human perception of vibration shape filter. Both perfect measurement and estimated state cases are considered. The impact of the measurement noise on the design of the optimal controller is demonstrated. The performance of the optimally controlled system is compared with an optimal passive system. It is shown that significant improvements in ride comfort can be achieved through the use of actively controlled cab suspensions. 相似文献
478.
F. M. Everard 《Maritime Policy and Management》1995,22(3):197-199
The paper, first of all, examines what a 'rogue ship' is and then moves on to the various practical solutions as to how to deal with the problem. There is no one single answer but the author believes that it is in the interest of society in general to get rid of these ships. 相似文献
479.
480.
C. C. Macadam M. W. Sayers J. D. Pointer M. Gleason 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1990,19(4):201-236
Results of vehicle crosswind research involving both full-scale driver-vehicle tests and associated analyses are presented. The paper focuses on experimental crosswind testing of several different vehicle configurations and a group of seven drivers. A test procedure, which utilized wind-generating fans arranged in alternating directions to provide a crosswind “gauntlet”, is introduced and described. Driver preferences for certain basic chassis and aerodynamic properties are demonstrated and linked to elementary system responses measured during the crosswind gauntlet tests. Based on these experimental findings and confirming analytical results, a two-stage vehicle design process is then recommended for predicting and analyzing the crosswind sensitivity of a particular vehicle or new design. 相似文献