全文获取类型
收费全文 | 2602篇 |
免费 | 222篇 |
国内免费 | 191篇 |
专业分类
电工技术 | 76篇 |
综合类 | 443篇 |
化学工业 | 42篇 |
金属工艺 | 25篇 |
机械仪表 | 104篇 |
建筑科学 | 162篇 |
矿业工程 | 26篇 |
能源动力 | 14篇 |
轻工业 | 17篇 |
水利工程 | 23篇 |
石油天然气 | 21篇 |
武器工业 | 725篇 |
无线电 | 535篇 |
一般工业技术 | 141篇 |
冶金工业 | 53篇 |
原子能技术 | 8篇 |
自动化技术 | 600篇 |
出版年
2024年 | 23篇 |
2023年 | 44篇 |
2022年 | 57篇 |
2021年 | 85篇 |
2020年 | 75篇 |
2019年 | 74篇 |
2018年 | 68篇 |
2017年 | 84篇 |
2016年 | 88篇 |
2015年 | 125篇 |
2014年 | 191篇 |
2013年 | 148篇 |
2012年 | 202篇 |
2011年 | 203篇 |
2010年 | 194篇 |
2009年 | 188篇 |
2008年 | 141篇 |
2007年 | 179篇 |
2006年 | 165篇 |
2005年 | 120篇 |
2004年 | 81篇 |
2003年 | 86篇 |
2002年 | 58篇 |
2001年 | 44篇 |
2000年 | 52篇 |
1999年 | 37篇 |
1998年 | 26篇 |
1997年 | 23篇 |
1996年 | 31篇 |
1995年 | 27篇 |
1994年 | 20篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 10篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1980年 | 3篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1961年 | 2篇 |
1960年 | 1篇 |
1957年 | 1篇 |
1956年 | 2篇 |
1955年 | 3篇 |
1954年 | 2篇 |
排序方式: 共有3015条查询结果,搜索用时 15 毫秒
41.
This paper develops an event-triggered-based finite-time cooperative path following (CPF) control scheme for underactuated marine surface vehicles (MSVs) with model parameter uncertainties and unknown ocean disturbances. First, a finite-time extended state observer (FTESO) is proposed, in which the FTESO can estimate the velocities and compound disturbances in finite time. Then, the finite-time LOS guidance law based on velocity estimation values is designed to obtain the desired surge velocity and the desired yaw rate. In order to realize the cooperative control of multiple paths in finite time, the cooperative control law for the path variable is designed. In addition, the relative threshold event-triggered control (ETC) mechanism is incorporated into the formation control algorithm, and an event-triggered-based finite-time CPF controller is designed, which not only effectively reduces the update frequency of controller and the mechanical loss of actuator but also improves the control performance of system. Furthermore, by using homogeneous method, Lyapunov theory, and finite-time stability theory, it is proved that under the proposed finite-time CPF control scheme, the formation errors can converge to a small neighborhood around origin in finite time. Finally, numerical simulation results illustrate the effectiveness of the proposed control scheme. 相似文献
42.
彭晓玲 《重庆科技学院学报(社会科学版)》1998,(3)
在市场经济的冲击下,我国青年现阶段的价值观发生了很大的变化,主要表现为:一元化价值观向多元化价值观演变;理想主义价值取向转为务实求实的价值取向;群体本位向个体本位取向偏移。在这个价值观转变当中,往往出现一些畸形的价值取向,所以应坚持正确的导向,强化新的价值观。 相似文献
43.
Rapid growth of the volume of interactive questions available to the students of modern E‐Learning courses placed the problem of personalized guidance on the agenda of E‐Learning researchers. Without proper guidance, students frequently select too simple or too complicated problems and ended either bored or discouraged. This paper explores a specific personalized guidance technology known as adaptive navigation support. We developed JavaGuide, a system, which guides students to appropriate questions in a Java programming course, and investigated the effect of personalized guidance a three‐semester long classroom study. The results of this study confirm the educational and motivational effects of adaptive navigation support. 相似文献
44.
This paper presents a new methodology for the design and implementation of gain‐scheduled controllers for multi‐rate systems. The proposed methodology provides a natural way to address the integrated guidance and control problem for autonomous vehicles when the outputs are sampled at different instants of time. A controller structure is first proposed for the regulation of non‐square multi‐rate systems with more measured outputs than inputs. Based on this structure, an implementation for a gain‐scheduled controller is obtained that satisfies an important property known as the linearization property. The implementation resembles the velocity implementation for single‐rate systems. The method is then applied to the problem of steering an autonomous rotorcraft along a predefined trajectory defined in terms of space and time coordinates. By considering a convenient error vector to describe the vehicle's dynamics, the trajectory tracking problem is reduced to that of regulating the error variables to zero. Because of the periodic multi‐rate nature of the onboard sensor suite, the controller synthesis is dealt with under the scope of linear periodic systems theory. Simulation results obtained with a full non‐linear rotorcraft dynamic model are presented and discussed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
45.
In this work we address the tracking control problems for autonomous underwater vehicles (AUVs). The proposed solution is based on the variable structure systems (VSS) theory and, in particular, on the second‐order sliding‐mode (2‐SM) methodology. The tuning of the controller is carried out via black‐box approach, dispensing with the knowledge of the actual AUV parameters, by simply progressively increasing a single gain parameter. The presented stability analysis includes explicitly the unmodelled actuator dynamics and the presence of external uncertain disturbances. The good performance of the proposed scheme is verified by means of simulations on a 6‐DOF AUV. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
46.
应用型本科经管类专业Visual FoxPro程序设计课程教学改革探索 总被引:1,自引:0,他引:1
针对目前多数应用型本科院校经济、管理类专业计算机公共基础课Visual FoxPro程序设计教学中存在的问题,本文提出以项目导向、模块驱动的方式来组织教学内容,课堂教学和项目小组协同学习相互促进的教学方式,课内实验和实战演练相结合的训练方法,并给出具体实施办法,实践证明这种教学模式行之有效、教学效果良好。 相似文献
47.
文章分析了主题图的相关理论和传统文献组织方法优劣,论证了主题图在文献资源组织中的可行性,提出了基于主题图的文献资源组织模型及构建方法,引申了基于该模型的文献检索、主题导学、个性化资源推荐等应用研究。 相似文献
48.
针对欠驱动飞艇的路径跟踪控制问题,提出了一种基于制导向量场的三维路径跟踪控制方法.首先,引入向量场理论.接着基于牛顿–欧拉方程建立欠驱动飞艇动力学模型.基于所提模型和向量场理论构造制导向量场以获得期望姿态角和期望速度.然后结合反步法和PD控制设计路径跟踪控制器,用指令滤波器对控制器设计过程中虚拟控制的导数进行估计,避免了复杂的解析计算.所设计的控制器是由制导向量场子系统、姿态稳定环和速度跟踪环组成的内外环结构.稳定性分析证明了飞艇的路径跟踪误差最终一致有界.最后仿真结果验证了所提出方法的有效性. 相似文献
49.
A differential game‐based guidance law design is proposed for a class of accelerating exoatmospheric missiles. By analyzing the nonlinear dynamic equations, a class of motions that does not require maneuver effort is derived for the missile. Using this property, a two phase guidance scheme can be derived that permits a perfect interception. In Phase 1, the missile is put in collision course with the target, which means in Phase 2 the missile should intercept the target with a straight line flight course, at a specified terminal body angle. Differential game based guidance laws are derived respectively for the two phases to guarantee the implementation of the guidance scheme. Simulation results show that the methodology provides robust interception performance. 相似文献
50.