全文获取类型
收费全文 | 551篇 |
免费 | 12篇 |
专业分类
公路运输 | 189篇 |
综合类 | 35篇 |
水路运输 | 168篇 |
铁路运输 | 15篇 |
综合运输 | 156篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 19篇 |
2017年 | 14篇 |
2016年 | 34篇 |
2015年 | 6篇 |
2014年 | 20篇 |
2013年 | 83篇 |
2012年 | 24篇 |
2011年 | 23篇 |
2010年 | 32篇 |
2009年 | 34篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 9篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 13篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 19篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有563条查询结果,搜索用时 15 毫秒
531.
Abstract In this article we consider a linear programming model for assessing the aggregate impact of land‐use activities scattered over a large area on the resultant pollutant concentrations in coastal waters. The dispersion to coastal waters of the adverse environmental loads generated by the land uses is described by a set of transport coefficients that measure the attenuation of pollutants, such as industrial BOD, carried to the coast along surface drainage basins. Further dispersion in the waters caused by tidal action is then described by the simple procedure know as “pollution susceptibility.”; The model seeks to minimize the steady‐state concentrations of pollutants by establishing an optimal spatial configuration of residential, commercial, and industrial land uses. This configuration is constrained by a number of restrictions based on local and regional targets for growth and development. The methodology discussed in this article is intended to be useful to regional planners, and is based on a study conducted for the Long Island area. 相似文献
532.
William T. Davoren 《Coastal management》2013,41(2):111-153
Abstract Although the early efforts to save San Francisco Bay in the 1960's provided the role model for protection of California's 1100 mile ocean coastline, neither Proposition 20 of 1972 nor the California Coastal Act of 1976 provided any benefits to San Francisco Bay. One result is that the Bay is locked into its urban, shoreline‐use dominated plan of 1969 while every other estuary and coastal wetland in California receives much stronger protection of its resources. Furthermore, due to the complexity of California's water laws, there is no instream flow protection for receiving waters such as San Francisco Bay. This is particularly critical considering that 70% of the Bay's freshwater inflow has been diverted. The Bay's present decline as the largest and most important estuary on the West Coast, as well as its possible death as an estuary, may be irreversible. The problem requires the immediate attention of engineering, scientific, economic and legal disciplines if San Francisco Bay is to be saved. 相似文献
533.
介绍了一种经久耐用的可以减小汽油机摩擦功和CO2排放的新型抗磨损低摩擦的活塞裙部涂层。适应了当前高强化发动机和节能减排的市场需求。 相似文献
534.
Peter T. Leach 《中国远洋航务》2008,(9):34-35
自巴拿马运河管理局两年前宣布修建第三组船闸以来,许多行业观察家都怀疑巴拿马运河管理局是否过于野心勃勃。为了支付修建第三组船闸的费用,巴拿马运河计划增加通行费。此举是否会增加其它航线的竞争力?巴拿马运河管理局如何将项目成本控制在52.5亿美元以下,同时又保证项目如期竣工? 相似文献
535.
This paper presents a new controller design method based on a data-mining polynomial algorithm. We show application of a polynomial
data-mining algorithm, where an input-state linearized polynomial vehicle model is developed for very low speed operation
and, without introducing any processes with fudge factors, control inputs of a nonlinear system are obtained in the original
coordinates. We verify the developed modeling method and controller design method through numerical experiments. 相似文献
536.
This paper presents a space vector current controller for a brushless permanent magnet motor in electric and hybrid electric
vehicles. The proposed current controller selects space vectors based on the sector selection under a three-level hysteresis
comparator to decrease the current ripple. The proposed approach can improve the performance of a brushless PM drive such
as the average switching frequency and the total harmonic distortion (THD) compared with the conventional hysteresis current
control. The experiment is performed first to verify the proposed control. Then, the method is implemented in a hybrid electric
vehicle simulation model with standard driving cycles based on the control strategy to evaluate the drive performance in the
vehicle system. The experimental and simulation results indicate that the presented control can improve the performance of
the brushless PM machine drive. 相似文献
537.
K. -H. Moon S. -H. Lee S. Chang J. -K. Mok T. -W. Park 《International Journal of Automotive Technology》2009,10(4):441-449
Many methods we have been developed to control the rear wheels of a vehicle, but most of them are designed for automobiles
with four wheels. The AWS (all wheel steering) control method for articulated vehicles is currently applied only to Phileas
vehicles developed by APTS, but the control algorithm for this system has yet to be reported. In the present paper, a new
algorithm is proposed after the AWS ECU (electronic control unit) of the Phileas vehicle was tested and analyzed in order
to understand the existing steering algorithm. The new algorithm considers the vehicle geometry, stability of handling, and
safety, and can be easily applied to multi-axle vehicles. In order to verify the AWS algorithm, the trajectory and steering
angles of each algorithm were compared using the commercial software ADAMS. Turning radius, swing-out, and swept path width
were also investigated to determine the turning performance of the proposed algorithm. 相似文献
538.
The vibrational characteristics of automotives during idling were studied experimentally by considering the axial forces of
the drive shaft and the spider positions in a constant-velocity joint. The generated forces, such as PF (plunging force) and
GAF (generated axial force) in the assembly of the drive-shaft module, were measured directly by an experimental apparatus.
Measurements of the GAF and PF did not show the same trends as the joint angles. They depended instead on the types of CV
joints. In addition, the relationship between the offset values of the shaft and the spider positions in the tulip of the
constant-velocity joint were studied. As a result, the idle vibration characteristics were affected by the variation of the
spider positions and the vibrational characteristics in the axial direction of the shaft, including the amplitude and the
harmonic periods. 相似文献
539.
Piet M. T. Broersen 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1974,3(2):109-121
The so-called critical speed of a linearized railway vehicle is shown to be no useful measure for the stability of the system in practice. The important interaction between vehicle and track can be taken into account by the riding quality for a certain vehicle on every particular piece of track. The riding quality is determined by the accelerations transmitted to the payload, weighted according to comfort standards, and the relative displacements between wheel and rail. From the riding quality demands both for vehicle design and for maintenance of the track can be derived. 相似文献
540.
Adaptive Control of 4WS System by Using Neural Network 总被引:3,自引:0,他引:3
T. Shiotsuka A. Nagamatsu K. Yoshida 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1993,22(5):411-424
An adaptive control system of the model following type is proposed for drive motion control of a four wheel steering (4WS) car with using neural network (NN) which has mastered nonlinear friction force between tire and road surface. A model of one rigid body is adopted which represents appropriately two kinds of car motion caused by steering action, namely the lateral displacement and the yawing rotation, and an equation of motion is described in a simplified form to make a system equation for motion control possible. Nonlinear relation between the cornering force of tire and the slip angle is obtained by numerical analysis with the tire model proposed by E. Fiala, taking friction coefficient and car speed as the parameters. The result is used as the teaching signal for NN. Three NN are used in the control system composed of both the feed-forward and the feedback circuits in order to realize adaptive control. Validity and usefulness of the proposed adaptive control system with NN are verified by three kinds of computer simulation. 相似文献