全文获取类型
收费全文 | 3165篇 |
免费 | 210篇 |
国内免费 | 112篇 |
专业分类
化学 | 57篇 |
力学 | 111篇 |
综合类 | 11篇 |
数学 | 37篇 |
物理学 | 337篇 |
综合类 | 2934篇 |
出版年
2024年 | 17篇 |
2023年 | 19篇 |
2022年 | 41篇 |
2021年 | 53篇 |
2020年 | 61篇 |
2019年 | 48篇 |
2018年 | 47篇 |
2017年 | 72篇 |
2016年 | 68篇 |
2015年 | 98篇 |
2014年 | 142篇 |
2013年 | 116篇 |
2012年 | 181篇 |
2011年 | 154篇 |
2010年 | 152篇 |
2009年 | 140篇 |
2008年 | 165篇 |
2007年 | 224篇 |
2006年 | 195篇 |
2005年 | 183篇 |
2004年 | 170篇 |
2003年 | 166篇 |
2002年 | 145篇 |
2001年 | 123篇 |
2000年 | 111篇 |
1999年 | 87篇 |
1998年 | 68篇 |
1997年 | 86篇 |
1996年 | 71篇 |
1995年 | 52篇 |
1994年 | 57篇 |
1993年 | 40篇 |
1992年 | 36篇 |
1991年 | 22篇 |
1990年 | 13篇 |
1989年 | 28篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 5篇 |
1984年 | 1篇 |
排序方式: 共有3487条查询结果,搜索用时 15 毫秒
211.
导出工程上实用的确定开关磁阻电动机主要尺寸绕组匝数的公式,详细论述了该类电机主要参数的选取原则,由此提供一个适合于计算机编程的具体设计方法。 相似文献
212.
在交流电动机矢量控制的基础上,对双馈电机动的数学模型作了符合工程实际的简单,并且采用求极值的方法,推导了3种最佳控制方式。 相似文献
213.
介绍了一种新型的转子位置检测器,它与已往的位置检测器相比较,不同之处在于去掉了与主电机同轴相连的小型绕线式感应电动机以及与其相关的复杂的机械连接部件 相似文献
214.
215.
Friction is one of the main factors that affect the positioning accuracy of motion system. Friction compensation based on friction model is usually adopted to eliminate the nonlinear effect of friction. This paper presents a proportional-plus-derivative (PD) feedback controller with a friction compensator based on LuGre friction model. We also design a state observer to observe the unknown state of LuGre friction model, and adopt a parameter adaptive law and off-line approximation to estimate the parameters of LuGre friction model. Comparative experiments are carried out among our proposed controller, PD controller with friction compensation based on classical friction model, and PD controller without friction compensation. Experimental results demonstrate that our proposed controller can achieve better performance, especially higher positioning accuracy. 相似文献
216.
217.
王智平 《西南师范大学学报(自然科学版)》1996,21(1):97-100
探讨了运动信息的不同模拟方式对运动学习的影响,36名女大学生随机均分三组A组的运动信息采用视觉模型,B组采用视觉模拟和语言模拟(1),C组采用视觉模拟和语言模拟(Ⅰ),(Ⅱ),其中语言模拟(I)是技术动作的详细语言描述,语言模拟(Ⅱ)是技术动作名称,运动学习的任务为初级剑术的4个技术动作,运动学习成绩的方差分析表明,对即时运动练习,B,C两组的成绩显著优于A组,但B,C两组无显著差异,一周后的延迟 相似文献
218.
The stability of the rotor of ultrasonic motor driving fluid directly is a key to its applications and control. This paper introduced the acoustic streaming and acoustic viscous stress near the boundary layer. Following this, the effect of acoustic viscous force on the stability of the rotor of ultrasonic motor driving fluid directly was presented in detail. The result showed that this system can be equivalent to a mass-spring and the spring constant can be used to weigh the stability of the rotor. By this model and relevant experiments, factors that affect the stability of the rotor such as the driving frequency, the rotor's weight and radius, the saturated acoustic streaming velocity, the mode number of stator vibration, the fluid's height and type are investigated and useful guidelines for design and application are obtained. 相似文献
219.
Elastic friction drive of surface acoustic wave motor 总被引:2,自引:0,他引:2
Importance of elastic deformation control to obtain large output force with a surface acoustic wave (SAW) motor is discussed in this paper. By adding pre-load to slider, stator and slider surfaces are deformed in a few tens nanometer. Appropriate deformation in normal direction against normal vibration displacement amplitude of SAW existed. By moderate deformation, the output force of the SAW motor was enlarged up to about 10 N and no-load speed was 0.7 m/s. To produce this performance, the transducer weight and slider size were only 4.2 g and 4 x 4 mm(2).By traveling wave propagation, surface particles of the SAW device move in elliptical motion. Due to the amplitude of the elliptical motion is 10 or 20 nm order, the contact condition of the slider is very critical. To control the contact condition, namely, the elastic deformation of the slider and stator surface in nanometer order, a lot of projections were fabricated on the slider surface. The projection diameter was 20 micro m. In static condition, the elastic deformation and stress were evaluated with the FEM analysis. From this calculation and the simulation result, it is consider that the wave crest is distorted, hence the elasticity has influence on the friction drive condition.Elastic deformation of the stator surface beneath the projection from the initial position were evaluated. In 4 x 4 mm(2) square area, the sliders had from 1089 to 23,409 projections. Depression was independent to the contact pressure. However, the output force depended on the depression although the projection density were different. From the view point of the output power of the motor, the proper depression was independent to the projection density. Around 25 nm depression, the output force and output power were maximized. This depression value was almost same as the vibration displacement amplitude of the stator transducer. 相似文献
220.