首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3183篇
  免费   8篇
公路运输   847篇
综合类   719篇
水路运输   953篇
铁路运输   36篇
综合运输   636篇
  2023年   10篇
  2022年   21篇
  2021年   10篇
  2020年   8篇
  2019年   8篇
  2018年   368篇
  2017年   325篇
  2016年   362篇
  2015年   10篇
  2014年   37篇
  2013年   140篇
  2012年   126篇
  2011年   344篇
  2010年   334篇
  2009年   100篇
  2008年   281篇
  2007年   149篇
  2006年   14篇
  2005年   69篇
  2004年   60篇
  2003年   60篇
  2002年   30篇
  2001年   8篇
  2000年   18篇
  1999年   12篇
  1998年   25篇
  1997年   14篇
  1996年   20篇
  1995年   18篇
  1994年   6篇
  1993年   11篇
  1992年   12篇
  1991年   8篇
  1990年   12篇
  1989年   8篇
  1988年   7篇
  1987年   10篇
  1986年   9篇
  1985年   8篇
  1984年   9篇
  1983年   12篇
  1982年   7篇
  1981年   13篇
  1980年   8篇
  1979年   15篇
  1977年   16篇
  1976年   11篇
  1975年   10篇
  1974年   10篇
  1973年   5篇
排序方式: 共有3191条查询结果,搜索用时 15 毫秒
961.
962.
A. D. May 《Transportation》1992,19(4):313-333
This paper reviews experience with road pricing in Europe and Asia. It considers the objectives of road pricing, and demonstrates that differences in objectives lead to differences in scheme design and performance. It reviews the criteria for design of road pricing systems, and the development of charging structures and technologies to meet those criteria. In particular it discusses the relative merits of pre-determined and congestion-dependent charging structures, and of off-vehicle and on-vehicle charging systems. It assesses the performance of road pricing systems to date, discusses objections to road pricing and demonstrates that the role of road pricing within a wider transport strategy and the use made of the revenue generated, will be important determinants of public acceptability. Finally it assesses the relative merits of alternative approaches to implementation and argues that these will need to pay as much regard to public acceptability as to technical performance.  相似文献   
963.
A six degree of freedom model of an agricultural tractor and trailer combination has been developed. Results from eigenvalue and frequency response calculations indicated that tractor operator vibration levels will be higher when operating with a trailer than for the tractor alone, due mainly to increased tractor pitch motion.

Although minor improvements could be made to present tractor and trailer combinations by moving the hitch forward of the tractor rear axle or providing some damping at a sprung hitch, the scope for a significant improvement in ride lies in changing the configuration. If higher speed specialised transport vehicles prove economical for agriculture, there are some advantages in ride vibration to be gained by changing the layout of the tractor and trailer combination to resemble an off-road version of a commercial articulated lorry.  相似文献   
964.
965.
In this note, a simple network equilibrium based approach for estimating a trip matrix using link traffic count data is proposed. In essence a combined distribution and assignment model is formulated in which the link flow data serve to furnish an estimate for the sum of the integrals of the link cost functions. A comparison of this model with others proposed previously is made.  相似文献   
966.
Array calibration is important in engineering practice. In this paper, fast calibration methods for a ULA's gain and phase errors both in far and near fields are proposed. In the far field, using a single sound source without exact orientation, this method horizontally rotates the array exactly once, performs eigen value decomposition for the covariance matrix of received data, then computes the gain and phase error according to the formulas. In the near field, using the same single sound source, it is necessary to rotate the array horizontally at most three times, build equations according to geometric relations, then solve them. Using the formula proposed in this paper, spherical waves are modified into plane waves. Then eigen values decomposition is performed. These two calibration methods were shown to be valid by simulation and are fast, accurate and easy to use. Finally, an analysis of factors influencing estimation precision is given.  相似文献   
967.
968.
For multibody systems with closed kinematic Loops a set of ordinary differential equations and decoupled algebraic equations is formulated which can be solved with explicit multistep integration algorithms. This is achieved by introducing a minimal set of generalized coordinates being specified during numerical integration. For avoiding restart of the integration algorithm after changing these variables transformation relationships are given. Velocity and acceleration constraints are satisfied exactly, position constraints are fulfilled approximately by a dynamic invariant projection onto the constraint manifold. The method is demonstrated by an application to a five-point wheel suspension.  相似文献   
969.
Paper deals with the linear behaviour of a railway vehicle with any arbitrary number of wheelsets, body parts and connecting elements. A vehicle which has both perfect curving properties and asymptotical stability at vanishing speed, has to satisfy a twofold condition, indicated by Wickens in 1978. In the present paper this condition is derived in reliance upon the dimension theorem for linear mappings. How the investigation can be executed in practice, is shown for the case of a two-axled vehicle. At last the behaviour in a transition curve is discussed.  相似文献   
970.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号