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   46篇
  免费   27篇
数学   4篇
物理学   69篇
  2022年   1篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2018年   1篇
  2013年   1篇
  2010年   1篇
  2008年   1篇
  2007年   1篇
  2006年   5篇
  2005年   4篇
  2004年   4篇
  2003年   2篇
  2002年   2篇
  2000年   4篇
  1999年   2篇
  1998年   2篇
  1993年   2篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   5篇
  1987年   2篇
  1986年   3篇
  1985年   5篇
  1984年   2篇
  1983年   2篇
  1982年   3篇
  1981年   3篇
  1980年   2篇
  1979年   2篇
  1977年   1篇
  1966年   1篇
  1965年   1篇
  1964年   1篇
排序方式: 共有73条查询结果,搜索用时 15 毫秒
1.
Starting from piezoelectric crystal dynamic equation etc.,both the electric potential and surface chargeinduced by the incident wave are obtained with electrical boundary perturbation technique.The scatteredwaves are then derived including both surface and bulk waves through integral transformation with theinduced charge as exciting source.The scattered surface waves from the grating on YZ-LiNbO_3 are then numerically calculated,and boththe reflective and forward scattering coefficients are given vs.the strip width.Furthermore,the surface wavephase velocity change when passing the grating is derived and numerically calculated too.The theoreticalprediction agrees well with measured results.  相似文献   
2.
A new weighting method,transducer weighting.for the uniform groove-deph RAC is proposed in thispaper.The weighted input and output transducersform a weighting transversal filter In addition,the groove-width weighting,which can be used as an auxiliary is also discussed. By using the new methods,two uniform groove depth RACs have been designed and fabricated,Thesidelobe suppressions achieved are 31 dB and 32 dB.respectively.The results are considered satisfactorybecause the phase compensation by metal strip was not applied.  相似文献   
3.
We achieve a successful novel lift-off of patterning Pt/Ti electrodes on SiO2/Si substrates by employing ZnO sacrificial layer deposition and patterning, successive uniform Pt/Ti deposition and final lift-off. Then we deposit PZT thin films on the electrodes. Compared with the conventional lift-off processes for the electrodes, this novel process does not need post-annealing, which must be performed after conventional lift-off process. It is demonstrated that the electrodes patterned by the novel lift-off process have stronger adhesion. The electrodes and the PZT films on the electrodes are more compact and smoother than those by the conventional lift-off process.  相似文献   
4.
We investigate the focusing phenomena of a surface acoustic wave (SAW) field generated by a circular-arc interdigital transducer (IDT) on a piezoelectric crystal. A rigorous vector field theory of surface excitation on the crystal we developed previously is used to evaluate the convergent SAW field instead of the prevalent scalar angular spectrum used in optics. The theoretical results show that the anisotropy of a medium has great impact on the focusing properties of the acoustic beams, such as focal length and symmetrical distributions near the focus. A dark field method is used in experiment to observe the focusing of the SAW tield optically. Although the convergent phenomena of SAW field on the anisotropic media or piezoelectric crystals are very complicated, the experimental data are in agreement with those from the rigorous theory.  相似文献   
5.
圆形振动膜ZnO压电微传声器的研制   总被引:1,自引:0,他引:1       下载免费PDF全文
本文介绍了一种新型圆形振动膜ZnO压电微传声器的制备,并对传声器制备的工艺过程进行了较为详细的描述。圆形振动膜的压电传卢器与以前方形振动膜结构设计相比,较大幅度提高了传声器的灵敏度和成品率,灵敏度达到-70dB(相对于1V/Pa),成品率达到80%。  相似文献   
6.
本对声表面波梯形谐振滤波器4级级联的5种不同级联结构进行了理论分析,计算出了其频响特性曲线。对5种不同结构的特性进行了比较,得出了不同结构在带宽、矩形系数、带外抑制等方面的特性,以期对以后实际器件的设计提供理论根据。  相似文献   
7.
单一空化气泡运动的高速摄影的实验研究   总被引:4,自引:0,他引:4  
作者用高速摄影方法实验研究了单一空化气泡的运动.气泡生长闭合运动的实验结果与理论基本上是符合的.在仔细研究空化气泡闭合瞬刻照片发现有“小脉动”现象存在,它为空化气泡在闭合瞬刻在气泡内会产生微骇波的假说提供了有力佐证.本文还通过实验研究了气泡生长、闭合和反跳运动的衰减性质.  相似文献   
8.
The diffraction phenomena of SAW normally incident on acoustic gratings have been developed.The acoustic grating which is composed of a periodic array of metal film stripes is fabricated on thesurface of Y-cut LiNbO_3 on which the SAWs propagate. Theoretically,the diffraction characteristics of the gratings on which the SAW beam normallyimpinges are analyzed by means of the phenomenological theory.The emphases are laid on twospecial cases,i.e."thin grating"and"thick grating"situations.For the former,the Raman-Nathapproximation is quoted from the theory of acousto-optical diffraction.For the latter,the analyticalexpressions of the diffracted intensities are deduced by using the normal mode theory. Experimentally,two sorts of samples which correspond respectively to"thick grating"and"thingrating"are designed and fabricated.Some interesting results are obtained by means of the opticalmethods.The images of the SAWs power flows of the diffracted acoustic fields as well as the SAWwavefronts within the grating  相似文献   
9.
The effect of electric load on the piezoelectric vibrational system due to electroacoustic coupling isanalytically investigated.The analytical results show that:(1)when load impedance continuallychanges from ∞to+∞,the mechanical resonant frequency of the system would fill all frequencydomain from 0 to ∞;(2)the displacement and stress distributions also would change,even the dis-placement may be zero at both free ends(i.e.at points where stress is equal to zero). Finally,the experiments for longitudinal vibration of piezoelectric strip of lateral polarizationare given and compared with theoretical results.  相似文献   
10.
This paper developes the general theory of the surface excitation of elastic wave field in a halfspace of piezoelectric crystal for both free and metallized surfaces.It is shown that the general elas-tic wave field U is equal to the convolution of the generalized Green's functions G and the general-ized forces T, U = G Twhere symbol,expresses dot-product-convolution. The generalized Green's functions are independent of excitation conditions and only dependenton material parameters and orientation. For the piezoelectric crystal,not only a mechanical source distribution at the surface,but anelectrical source distribution can also excite the elastic wave fields.Complete expressions of thegeneralized forces representing mechanical and electrical source distribution respectively are given.Especially for the free surface,the surface electrical sources can be composed of the discontinuityof normal electric displacement at the surface,and of the discontinuity of the tangential electric fieldas well.  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