全文获取类型
收费全文 | 7810篇 |
免费 | 101篇 |
专业分类
公路运输 | 1662篇 |
综合类 | 581篇 |
水路运输 | 2516篇 |
铁路运输 | 764篇 |
综合运输 | 2388篇 |
出版年
2023年 | 43篇 |
2022年 | 112篇 |
2021年 | 52篇 |
2019年 | 80篇 |
2018年 | 190篇 |
2017年 | 105篇 |
2016年 | 126篇 |
2015年 | 90篇 |
2014年 | 240篇 |
2013年 | 1220篇 |
2012年 | 316篇 |
2011年 | 372篇 |
2010年 | 224篇 |
2009年 | 366篇 |
2008年 | 298篇 |
2007年 | 266篇 |
2006年 | 230篇 |
2005年 | 269篇 |
2004年 | 288篇 |
2003年 | 181篇 |
2002年 | 146篇 |
2001年 | 132篇 |
2000年 | 138篇 |
1999年 | 98篇 |
1998年 | 129篇 |
1997年 | 111篇 |
1996年 | 138篇 |
1995年 | 149篇 |
1994年 | 84篇 |
1993年 | 189篇 |
1992年 | 160篇 |
1991年 | 77篇 |
1990年 | 83篇 |
1989年 | 57篇 |
1988年 | 74篇 |
1987年 | 65篇 |
1986年 | 59篇 |
1985年 | 77篇 |
1984年 | 73篇 |
1983年 | 73篇 |
1982年 | 73篇 |
1981年 | 95篇 |
1980年 | 68篇 |
1979年 | 91篇 |
1978年 | 56篇 |
1977年 | 69篇 |
1976年 | 53篇 |
1975年 | 65篇 |
1974年 | 50篇 |
1973年 | 45篇 |
排序方式: 共有7911条查询结果,搜索用时 343 毫秒
991.
V. Rapoport
J. Alford
《Marine Structures》1989,2(3-5):451-462This paper, based on analyses of case histories, reviews soil conditions causing sudden uncontrolled leg penetrations, together with site data needed to plan safe installations of jack-up drilling units. Punch-through-like failure in uniform clay profile is analysed. Preloading procedures aimed at minimizing potential damage to the unit are suggested and discussed. 相似文献
992.
S. Venkiteswaran 《Maritime Policy and Management》1995,22(3):229-230
The major and minor ports in India operate within different legal frameworks. Both allow privatization, but impose different conditions. Administrative culture has acted as a constraint on privatization in the major ports; private development at the minor ports has been very responsive to the amount of assistance offered by individual States. 相似文献
993.
994.
本文在现有晶界偏聚热力学和动力学模型的基础上,根据热力学定律、非克扩散定律及局部平衡理论,溶质原子晶界偏聚动力学模型。该模型既适合于平衡偏聚或非平衡偏聚的动力学计算,也适合于混合偏聚(平衡偏聚+非平衡偏聚)的动力学计算。计算结果和有关实测结果基本符合。 相似文献
995.
本文以联邦德国农业及经济状况为出发点,介绍了利用生物制品,主要是粮食,油料等农产品转化为发动机燃料的研究工作情况,并重点介绍了用菜籽油和酒精的试验研究情况。 相似文献
996.
Alan J. Horowitz 《Transportation》1984,12(3):261-275
The growth in popularity of microcomputers has reemphasized the need for simplified transit-planning techniques. This paper describes and evaluates a single-route ridership forecasting model which is designed to fit within a modest-sized microcomputer. The model is based upon the traditional four-step urban transportation modeling process, but it is simplified by removing the possibility of multiple transfers and by eliminating the highway network. An analysis of model error shows that these simplifications do not appreciably affect the accuracy of the forecasts. A particular advantage of implementing the model on a microcomputer is the user-friendliness that can be achieved by employing interactive color graphics for data input. 相似文献
997.
In 1982, a national survey of U.S. taxicab operators was conducted. This survey sought to assess the economic, operational and organizational status of the industry and to determine how these characteristics have been changing in response to rising costs and an economic recession. Two results of this survey are reported in this paper; the size structure and the organization of the industry. Both of these characteristics show that it has recently been undergoing two fundamental changes. These are the rapid switch away from employees as drivers to independent contractor drivers and decreasing average company size. 相似文献
998.
Roy E. SMITH Consultant 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1989,18(1):45-69
Railway vehicles with steered axles possess some unique dynamic characteristics. This paper reviews the reasons for the differences between these and more conventional vehicles and examines the results of analysis demonstrating the sensitivity of the phenomena to various mass, stiffness and geometric parameters. The implications which these results carry are discussed in terms of their design importance and their effect upon the performance boundaries of steel-wheeled rail vehicles. This review shows that a profound understanding of steered axle railway vehicles is developing and that this leads to the conclusion that a wide range of applications can benefit from their use. 相似文献
999.
Application of Sensitivity Methods to Analysis and Synthesis of Vehicle Dynamic Systems 总被引:1,自引:0,他引:1
Andrzej G. NALECZ Associate Professor Research Fellow 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1989,18(1):1-44
The development and application of sensitivity methods for determining the effects of parameter changes on the response of vehicle dynamic systems is presented. The procedures shown can be used to enhance the analysis and synthesis processes of virtually any road or rail vehicle system regardless of its complexity. The parametric sensitivity of vehicle models in time domain, steady state models and vehicle models in frequency domain can be investigated using different types of sensitivity functions, both dimensional and dimensionless including first order standard, percentage, logarithmic, second order standard, and logarithmic and percentage sensitivity measures. These sensitivity functions and measures are determined as functions of partial derivatives of system variables taken with respect to system parameters. In the case of sensitivity functions in the frequency domain the variable values are computed as either the magnitude or phase angle of a complex element of the transfer function matrix. The methods presented enable to determine the influence of all system primary (constant) and secondary (non-constant) parameters on system primary and secondary variables. The primary variables are state variables or elements of the transfer function matrix and the secondary variables may be any functions of primary variables and system parameters. Typical secondary system parameters which can be examined include initial conditions, time variant coefficients, natural frequencies, loads, and typical secondary variables are forces, weight transfers, stability factors and energy components. The analysis of sensitivity results obtained for three vehicle handling models in both linear and nonlinear regimes of vehicle performance and utilizing various types of sensitivity functions is also presented. 相似文献
1000.
研究调查了某地区4个火车站搬运作业工人的作业特点,劳动休息制度,劳动负荷及健康状况等,铁路搬运作业采用“三班两运转”轮班制度,工人劳动过程中负荷量较大,且主要是弯腰和转身这类易造成腰部损伤的动作,调查结果表明搬运工人的腰痛人数明显高于对照组,应加强劳动组织和劳动保护,以保障工人健康和提高工作效率。 相似文献