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   904篇
  免费   138篇
  国内免费   34篇
化学   93篇
力学   103篇
综合类   7篇
数学   9篇
物理学   864篇
  2023年   2篇
  2022年   14篇
  2021年   22篇
  2020年   14篇
  2019年   18篇
  2018年   15篇
  2017年   32篇
  2016年   46篇
  2015年   31篇
  2014年   81篇
  2013年   44篇
  2012年   70篇
  2011年   57篇
  2010年   48篇
  2009年   76篇
  2008年   63篇
  2007年   59篇
  2006年   59篇
  2005年   38篇
  2004年   36篇
  2003年   40篇
  2002年   28篇
  2001年   27篇
  2000年   21篇
  1999年   17篇
  1998年   18篇
  1997年   18篇
  1996年   12篇
  1995年   10篇
  1994年   5篇
  1993年   10篇
  1992年   8篇
  1991年   11篇
  1990年   4篇
  1989年   6篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1984年   6篇
  1982年   3篇
  1981年   2篇
  1979年   1篇
  1973年   1篇
排序方式: 共有1076条查询结果,搜索用时 31 毫秒
81.
High-speed filming is one of the most informative methods for assessing voice physiology data. Tracing high-speed images of the glottis provides quantitative parameters such as the glottal area and the glottal width function. By way of example, a number of studies are discussed which extract quantitative data from high-speed images showing voice onsets. Furthermore, a new computer system (MVAS; multi-dimensional voice analysis system) is presented that synchronously displays a laryngoscopic high-speed film, the electroglottographical signal, and several acoustic analyses of the recorded voice sample. The automatic measurement of glottal width and glottal area from the laryngoscopic images is also provided. Looking at former studies and our analyses of voice onsets reveals a tremendous intersubject and even intrasubject variability (different prephonatory closure, different time span until full amplitude is reached, different open quotient).  相似文献   
82.
高速光脉冲的测量方法   总被引:6,自引:1,他引:5       下载免费PDF全文
 综述了目前国际上公认的测量高速光脉冲的几种方法,主要包括电光条纹相机(SC)、快速脉冲取样、二次谐波产生(SHG)、频率分辨光学门(FROG)以及光谱相位干涉直接电场重建(SPIDER)等。详细地阐述和分析了这些方法的原理、特点、适用范围以及它们的研究现状。  相似文献   
83.
 利用双狭缝、透射光栅配亚仟X光条纹相机做了具有一维空间、时间和能谱分辨的三维软X光测量仪器(双狭缝透射光栅软X光时空分辨谱仪), 并成功地获得了金盘靶的N带X光(中心波长1.7nm)时空分辨图象 。该仪器空间分辨可达23μm, 时间分辨可达003ns, 能谱分辨(当源大小为100~300μm时对波长1.7nm的X光)可达0.4~ 0.7nm, 只需稍加改动, 即可用于其它波段的X光测量。  相似文献   
84.
Gas puff imaging (GPI) is one of the important diagnostics for the (ITPAC international tokamak physics activity ) and entering the ITPA IDD ( international diagnostics database ) . GPI is related to many investigations, for example, edge radiations, etc.  相似文献   
85.
温度变化导致航天相机光学系统像面位移的研究   总被引:3,自引:0,他引:3  
王红  韩昌元 《光学技术》2003,29(6):738-740
温度变化导致的像面位移会影响航天相机光学系统的成像质量。根据高斯光学理论,推导出了温度变化时的相机光学系统的像面位移公式,确定了温度敏感性最低的主、次反射镜的材料及与之相匹配的镜筒材料。最后计算和比较了在不同温度变化时的光学系统的传递函数。  相似文献   
86.
Infrared camera has been widely used in electrical power systems for predictive and preventive thermal fault diagnosis. Without historical IR images being considered, most thermograph analysis used at present are concerned with static image. The dynamic history and tendency analysis which compares the newly taken image with historical images is particularly attractive. Conclusions can be drawn from temperature variations rather than just from anomalous thermal pattern. However the spatial distortions prevent such dynamic analysis from being practicable. So the need to register infrared images arises. This paper proposes an automatic registration algorithm based on closed temperature contour matching for infrared image series of a target equipment taken at different times. Centroid Distance Function is used in image registration for the first time. The algorithm can remove spatial distortions, bring temperature variations into prominence and endow infrared camera with dynamic analysis ability. Experiment shows that the algorithm is simple, effective and extensible.  相似文献   
87.
陈超  谭显祥 《光子学报》1992,21(3):241-246
本文介绍了用全息干涉法诊断爆炸丝等离子体的数据处理方法。在考虑等离子体区域为轴对称的情况下,给出了由折射率计算等离子体电子密度的计算公式。在爆炸丝能量为9.6J的情况下,拍摄到了延时3μs的爆炸丝等离子体干涉图。运用计算机图象处理技术对反拍后的干涉图进行了处理,获得了较为理想的干涉图。用微机控制的线阵CCD摄像机判读了干涉条纹漂移。给出了等离子体密度随径向分布的曲线,并得到相应的等离子体密度在中心处约为1016个/cm3。  相似文献   
88.
圆扫描变像管人卫激光测距技术研究   总被引:1,自引:1,他引:0  
在本文中,我们设计并研制了用于毫米级精度人卫激光测距的圆扫描时间分析系统。研制的圆扫描变像管理论时间分辨率可优于3ps,可用于双色测距;偏转灵敏度高达10cm/kV,偏转空间分辨率优于24lp/mm;利用双MCP内增强,增益~1×106,并有门控功能以进一步提高信噪比和动态范围。扫描控制电路能提供300MHz、10W的正弦信号,其频率、幅度、相位稳定度均可满足要求。调试过程中较好地解决了阻抗变换、空间干扰和相位正交等关键问题。在仅2W的RF功率驱动下,即可实现稳定的φ24mm的圆扫描,系统实测时间分辨率达4.8ps。在实验室实测测距精度达亚毫米级。动态实验及模拟测距表明,该时间分析系统可满足第四代人卫激光测距系统的需要。  相似文献   
89.
Electrowetting-Based Variable-Focus Lens for Miniature Systems   总被引:1,自引:0,他引:1  
The meniscus between two immiscible liquids of different refractive indices can be used as a lens. A change in curvature of this meniscus by electrostatic control of the solid/liquid interfacial tension leads to a change in focal distance. It is demonstrated that two liquids in a tube form a self-centred variable-focus lens. The optical properties of this lens were investigated experimentally. We designed and constructed a miniature camera module based on this variable lens suitable for mobile applications. Furthermore, the liquid lens was applied in a Blu-ray Disc optical recording system to enable dual layer disc reading/writing.  相似文献   
90.
The generation and the subsequent evolution of dynamic failure events in homogeneous layered materials that occur within microseconds after impact were investigated experimentally. Tested configurations include three-layer and two-layer, bonded Homalite specimens featuring different bonding strengths. High-speed photography and dynamic photoelasticity were utilized to study the nature, sequence and interaction of failure modes. A series of complex failure modes was observed. In most cases, and at the early stages of the impact event, intra-layer failure (or bulk matrix failure) appeared in the form of cracks radiating from the impact point. These cracks were opening-dominated and their speeds were less than the crack branching speed of the Homalite. Subsequent crack branching in several forms was also observed. Mixed-mode inter-layer cracking (or interfacial debonding) was initiated when the intra-layer cracks approached the interface with a large incident angle. The dynamic interaction between inter-layer crack formation and intra-layer crack growth (or the so-called “Cook–Gordon Mechanism”) was visualized for the first time. Interfacial bonding played a significant role in impact damage spreading. Cracks arrested at weak bonds and the stress wave intensity was reduced dramatically by the use of a thin but ductile adhesive layer.  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