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   535篇
  免费   135篇
  国内免费   179篇
航空   470篇
航天技术   148篇
综合类   64篇
航天   167篇
  2024年   8篇
  2023年   14篇
  2022年   35篇
  2021年   60篇
  2020年   46篇
  2019年   46篇
  2018年   30篇
  2017年   32篇
  2016年   54篇
  2015年   36篇
  2014年   48篇
  2013年   42篇
  2012年   28篇
  2011年   47篇
  2010年   53篇
  2009年   31篇
  2008年   35篇
  2007年   39篇
  2006年   22篇
  2005年   22篇
  2004年   23篇
  2003年   15篇
  2002年   10篇
  2001年   10篇
  2000年   13篇
  1999年   7篇
  1998年   10篇
  1997年   7篇
  1996年   5篇
  1995年   5篇
  1994年   1篇
  1993年   6篇
  1992年   2篇
  1991年   4篇
  1989年   2篇
  1988年   1篇
排序方式: 共有849条查询结果,搜索用时 15 毫秒
431.
装备采购中的工业工程管理模式   总被引:2,自引:0,他引:2       下载免费PDF全文
阐述了信息环境下与工业工程对应的管理模式是企业资源计划.为了能够通过企业资源计划(ERP)来提升自我竞争力,分析了ERP的内涵、技术特点,总结了装备生产中实施ERP的经验教训,并以某装备代理方为研究对象进行了ERP绩效评价指标体系与数学模型建立的研究.  相似文献   
432.
基于弧长参数的开边自由曲面构件上纤维均匀覆盖(英文)   总被引:3,自引:0,他引:3  
This article uses arc-length parameters for path planning to carry out robotic fibre placement (RFP) over open-contoured structures This allows representing the initial path and offset points using an identical mathematical equation and computation by more simple arithmetic. With the help of classical differential geometry, the calculation of fiber-placing paths may be reduced to solution of initial-value problems of first-order ordinary differential equations in the parametric domain (parametrically defined mould surface) or in 3D space (an implicitly defined mould surface), thereby significantly improving on the existing methods. Compared with the conventional methods, the proposed method, besides its computational simplicity, has a better error control mechanism in computing the initial path and offset points. Numerical experiments are also carried out to demonstrate the feasibility of the new method in composite forming processes and also its potential application in computer numerical control (CNC) machining, surface trim, and other industrial practices.  相似文献   
433.
基于蚁群算法的无人机航路规划   总被引:10,自引:0,他引:10  
为了提高无人机(UAV)作战任务的成功率,在敌方防御区域内执行攻击任务前必须规划设计出高效的无人机飞行航路,保证无人机能够以最小的被发现概率及可接受的航程到达目标点。针对这一问题,对新近发展的蚁群算法进行了讨论,提出了适用于航路规划的优化方法,并对无人机的攻击任务航路进行了仿真计算。仿真结果表明,该方法是一种有效的航路规划方法。  相似文献   
434.
自由漂浮空间机器人最小基座反作用轨迹规划   总被引:1,自引:0,他引:1  
在自由漂浮空间机器人系统中,由于机械臂与基座之间存在动力学耦合,机械臂运动会对基座产生不期望的反作用干扰,因此必须最小化基座反作用。为此,提出了一种关节空间内点对点轨迹规划的方法。首先,利用sin函数参数化关节轨迹;然后根据基座反作用和运动约束定义适应函数;最后利用混沌粒子群优化(CPSO)算法搜索空间机械臂的全局最优轨迹,使基座反作用最小。该方法考虑了机械臂的关节角、关节速度和加速度约束。给出一个仿真算例来验证该方法的有效性。规划的轨迹连续平滑,适用于多自由度空间机械臂。  相似文献   
435.
We examined the use of hand gestures while people solved spatial reasoning problem in which they had to infer motion from static diagrams (mental animation problems). In Experiment 1, participants were asked to think aloud while solving mental animation problems. They gestured on more than 90% of problems, and most gestures expressed information about the component motions that was not stated in words. Two further experiments examined whether the gestures functioned in the mechanical inference process, or whether they merely served functions of expressing or communicating the results of this process. In these experiments, we examined the effects of instructions to think aloud, restricting participants' hand motions, and secondary tasks on mental animation performance. Although participants who were instructed to think aloud gestured more than control groups, some gestures occurred even in control conditions. A concurrent spatial tapping task impaired performance on mechanical reasoning, whereas a simple tapping task and restricting hand motions did not. These results indicate that gestures are a natural way of expressing the results of mental animation processes and suggest that spatial working memory and premotor representations are involved in mental animation. They provide no direct evidence that gestures are functional in the thought process itself, but do not rule out a role for overt gestures in this type of spatial thinking.  相似文献   
436.
文章提出了在离散区域上,基于起始点和目标点相向传播波碰撞法的机器人路径规划法。设机器人作业环境为二维平面大小一定的矩形地形,机器人行走时仅限于作原地转向或直线行走。基于此开展路径规划的仿真研究,提出了搜索许可路径的算法。计算机模拟结果证实该算法可行、有效。  相似文献   
437.
城市公共设施是城市环境的重要组成部分,也是城市时代精神和文化状态的标准。廊坊市的公共设施景观规划应“以人为本”,有效地结合廊坊“龙凤文化”的历史文化传承,从中体现出高尚的城市品质、精致生活环境、优雅的生活情趣。  相似文献   
438.
多智能体路径规划应用广泛但求解困难。为更好地处理多智能体路径规划中的路径冲突问题,提高求解效率,将冲突进一步分类为相向顶点冲突和交叉顶点冲突,并提出了对应的消解方式。相向顶点冲突的消解方法采用提前添加约束的方式,避免在消解其冲突的过程中产生另一个可预见的冲突;交叉顶点冲突的消解方法采用寻找最佳等待时间的方式,在消解其冲突的同时消解其他存在的冲突。两种冲突消解方法均可减小约束树的规模,在一定程度上减少算法的计算量。并提出了基于冲突搜索算法的高层节点冲突搜索算法。实验结果表明,所提出的冲突分类及消解方式有效地减小了算法高层中约束树的规模,降低了算法计算量,并在智能体密集的环境下表现出更大的优势。  相似文献   
439.
航空产品加工生产线正向着自动化、数字化和智能化的方向发展,自动化生产线对车间整体布局、物流和生产节拍都提出了更为严格的要求,对生产线进行规划仿真可以直观、准确地反映出生产线运行过程中可能出现的问题,并通过科学方法解决和优化这些问题.介绍了生产线规划仿真技术,在此基础上,对某型飞机导管自动化生产线的生产过程、工艺布局和物...  相似文献   
440.
《中国航空学报》2021,34(2):554-562
Helicopters are widely used in maritime Search and Rescue (SAR) missions. To ensure the success of SAR missions, search areas need to be carefully planned. With the development of computer technology and weather forecast technology, the survivors’ drift trajectories can be predicted more precisely, which strongly supports the planning of search areas for the rescue helicopter. However, the methods used to determine the search area based on the predicted drift trajectories are mainly derived from the continuous expansion of the area with the highest Probability of Containment (POC), which may lead to local optimal solutions and a decrease in the Probability of Success (POS), especially when there are several subareas with a high POC. To address this problem, this paper proposes a method based on a Minimum Bounding Rectangle and K-means clustering (MBRK). A silhouette coefficient is adopted to analyze the distribution of the survivors’ probable locations, which are divided into multiple clusters with K-means clustering. Then, probability maps are generated based on the minimum bounding rectangle of each cluster. By adding or subtracting one row or column of cells or shifting the planned search area, 12 search methods are used to generate the optimal search area starting from the cell with the highest POC in each probability map. Taking a real case as an example, the simulation experiment results show that the POS values obtained by the MBRK method are higher than those obtained by other methods, which proves that the MBRK method can effectively support the planning of search areas and that K-means clustering improves the POS of search plans.  相似文献   
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