全文获取类型
收费全文 | 14846篇 |
免费 | 1622篇 |
国内免费 | 1276篇 |
专业分类
电工技术 | 660篇 |
技术理论 | 2篇 |
综合类 | 1456篇 |
化学工业 | 829篇 |
金属工艺 | 1158篇 |
机械仪表 | 1941篇 |
建筑科学 | 1001篇 |
矿业工程 | 432篇 |
能源动力 | 402篇 |
轻工业 | 291篇 |
水利工程 | 207篇 |
石油天然气 | 450篇 |
武器工业 | 189篇 |
无线电 | 1440篇 |
一般工业技术 | 2311篇 |
冶金工业 | 463篇 |
原子能技术 | 95篇 |
自动化技术 | 4417篇 |
出版年
2024年 | 63篇 |
2023年 | 240篇 |
2022年 | 464篇 |
2021年 | 448篇 |
2020年 | 533篇 |
2019年 | 378篇 |
2018年 | 362篇 |
2017年 | 462篇 |
2016年 | 505篇 |
2015年 | 641篇 |
2014年 | 840篇 |
2013年 | 1017篇 |
2012年 | 1051篇 |
2011年 | 1203篇 |
2010年 | 946篇 |
2009年 | 936篇 |
2008年 | 911篇 |
2007年 | 985篇 |
2006年 | 928篇 |
2005年 | 789篇 |
2004年 | 611篇 |
2003年 | 635篇 |
2002年 | 472篇 |
2001年 | 353篇 |
2000年 | 313篇 |
1999年 | 302篇 |
1998年 | 273篇 |
1997年 | 223篇 |
1996年 | 191篇 |
1995年 | 160篇 |
1994年 | 113篇 |
1993年 | 80篇 |
1992年 | 60篇 |
1991年 | 56篇 |
1990年 | 50篇 |
1989年 | 42篇 |
1988年 | 29篇 |
1987年 | 10篇 |
1986年 | 17篇 |
1985年 | 11篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1957年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
271.
272.
273.
Target point‐based path‐following controller for a car‐type vehicle using bounded controls
下载免费PDF全文
![点击此处可从《国际强度与非线性控制杂志<br>》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper, we have studied the control problem of target point‐based path following for car‐type vehicles. This special path‐following task arises from the needs of vision‐based guidance systems, where a given target point located ahead of the vehicle, in the visual range of the camera, must follow a specified path. A solution to this problem is developed through a nonlinear transformation of the path‐following problem into a reference trajectory tracking problem, by modeling the target point as a virtual vehicle. The use of target point complicates the control problem, as the development produces a first‐order nonlinear nonglobally Lipschitz differential equation with finite escape time. This problem is solved by using small control signals. Bounded feedback laws are designed to control the real vehicle's angular acceleration and the virtual vehicle's velocity, to achieve stability. The resulting controller is globally asymptotically stable with respect to the origin, the proof of which is derived from Lyapunov‐based arguments and a bootstrap argument. It is also shown that the use of exponentially convergent observers/differentiators does not affect the stability of the closed‐loop system. The effectiveness of this controller has been illustrated through simulations. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
274.
目的:探讨校园网组建起来后,所面临的各种问题,并提供有效的解决方案。方法:从网络的结构性,网络的可靠性,网络的安全性三个方面进行分析,并提出相应的优化策略。结果:提高了校园网运行的可靠性、安全性和效率。结论:采用路径分析、关联规则待方法对网络进行优化,可以提高校园网的运行效率以及安全性。 相似文献
275.
Rotman lenses are used to obtain multiple beams from a single array. Although the beams produced by the feed antennas at focal points have no path length errors, the beams produced by feed antennas at off focal points may have large path length errors. These path length errors cause deterioration in the multiple beams. In this article, two novel methods are introduced to obtain feed curves which reduce the path length errors of off focal feed points significantly, compared with the commonly used circular and elliptical feed curves. The first method obtains feed curve points based on having zero path length error at three chosen points of the radiating array for each beam direction. The second method uses the particle swarm optimization method for obtaining optimum feed points for each beam direction. The results show that there is a very significant drop in the level of the maximum path length errors (in the order of about 1:4). © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 634–638, 2013. 相似文献
276.
277.
中国水利投资的发展路径分析 总被引:1,自引:0,他引:1
通过数据分析,总结出改革开放以来我国水利投资的基本变化趋势:从长期来看,我国水利投资处于不断上升的趋势.并且投资增速呈现不稳定波动的态势。1998年以来水利投资总量虽大幅度提高,但水利投资仍存在投资总量与实际需求差距过大、增长速度缓慢、区域差异较大等问题。针对以上问题,从公共财政保障机制缺失、财政支持政策缺乏、中央地方事权和财权不匹配等三方面,着重分析我国水利投资变化的原因,从建立公共财政投资稳定增长的投入机制、保障地方投入机制、利用市场融资等方面,提出未来我国水利投资的发展路径。 相似文献
278.
This paper presents a 3D path planning algorithm for an unmanned aerial vehicle (UAV) in complex environments. In this algorithm, the environments are divided into voxels by octree algorithm. In order to satisfy the safety requirement of the UAV, free space is represented by free voxels, which have enough space margin for the UAV to pass through. A bounding box array is created in the whole 3D space to evaluate the free voxel connectivity. The probabilistic roadmap method (PRM) is improved by random sampling in the bounding box array to ensure a more efficient distribution of roadmap nodes in 3D space. According to the connectivity evaluation, the roadmap is used to plan a feasible path by using A* algorithm. Experimental results indicate that the proposed algorithm is valid in complex 3D environments. 相似文献
279.
The method of artificial potential field has obvious advantages among the robot path planning methods including simple structure, small amount of calculation and relatively mature in theory. This paper puts forward the "Integral method" focusing on solving the problem of local minimization. The method analyses the distribution of obstructions in a given environment and regards adjacent obstacles as a whole, By changing the parameters of the repulsive force field, robots can quickly get out of the minimum point and move to the target point. This paper uses the Simurosot platform to carry on the simulation experiment on the improved artificial potential field method, which projects a feasible path successfully and verifies this method. 相似文献
280.
Gigabit home networks represent a key technology to make the Future Internet success a reality. Consumers will require networks to be simple to install, without the need of any new wire and with green consideration. To make this network ubiquitous, seamless and robust, a technology independent MAC layer will ensure its global control and provide connectivities to any number of devices the user wishes to connect to it in any room. In order to make this vision comes true, substantial progress is required in the fields of protocol design and in systems architectures. For this goal, we introduce a new convergence layer denoted inter-MAC, which provides a common infrastructure to the home network, Among the inter-MAC functionalities, we focused the interest on the path selection mechanism including the green aspect. To improve quality of service, reduce energy consumption and radiofrequency devices number, we define a new path selection protocol based on several metrics. We present some preliminary results obtained on an experimental test bed. 相似文献