全文获取类型
收费全文 | 662篇 |
免费 | 152篇 |
国内免费 | 37篇 |
专业分类
化学 | 35篇 |
力学 | 217篇 |
综合类 | 5篇 |
数学 | 7篇 |
物理学 | 587篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 17篇 |
2020年 | 16篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 31篇 |
2016年 | 24篇 |
2015年 | 31篇 |
2014年 | 47篇 |
2013年 | 39篇 |
2012年 | 61篇 |
2011年 | 59篇 |
2010年 | 25篇 |
2009年 | 37篇 |
2008年 | 43篇 |
2007年 | 44篇 |
2006年 | 46篇 |
2005年 | 29篇 |
2004年 | 26篇 |
2003年 | 18篇 |
2002年 | 27篇 |
2001年 | 26篇 |
2000年 | 22篇 |
1999年 | 14篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 20篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有851条查询结果,搜索用时 15 毫秒
91.
This paper presents an application in the automotive industry where a combination of electronic speckle-pattern interferometry and laser doppler velocimetry were used at a critical stage in the design process of an internal combustion engine. Combined deformation and surface relief measurements were used to study the phase and amplitude of deformation of a vibrating engine. The relief data was combined with the interferometer geometry and used to geometrically correct the deformation data, in an effort to improve accuracy. The measurements allowed rapid identification and quantification of design weaknesses, particularly those causing undesirable resonances. This led to a significant reduction in the design time and lowering of costs, when compared with existing design optimisation methods. 相似文献
92.
93.
In this work the effects of electrode morphology on the slit flow of an electrorheological (ER) fluid via laser Doppler anemometry (LDA) are studied. For this purpose, oblique and corrugated electrodes were used. Under a.c.-conditions the ER-effect with the oblique and corrugated electrodes is greater in comparison to the case of smooth electrodes at the same voltage and pressure drop. An average factor of 2.0 and 2.5 (in the range 1–5 kV) describes the increase in the ER-effect for the oblique and corrugated electrodes, respectively. This increase in ER-effect is accompanied by a decrease in electric current. Under d.c.-conditions the ER-effect with the oblique and corrugated electrodes is somewhat better than with the smooth electrodes but only at a very low field strength. Increasing the field strength leads to a decreased ER-effect (in comparison to the smooth electrodes). This decrease of the ER-effect is always accompanied by a decrease in electric current (d.c.-field). 相似文献
94.
We have developed a fetal movement monitoring system based on small displacement measurement of internal tissues. When ultrasonic pulses are transmitted to the fetus, the reflected ultrasonic waves which have a Doppler frequency shift due to the fetal movements are detected by using an ultrasonic pulsed Doppler technique. In this paper, we propose a displacement measurement method for internal tissues which is based on the Doppler signal digital detection technique. In the method, the received ultrasonic RF signals are sampled with a sampling frequency of four times higher than the centre frequency of the ultrasonic waves; the Doppler frequency shift signals are derived using digital signal processing. From the detected signals, the internal displacements are estimated using the arc-tangent method. The basic algorithm of the detection method has already been used in the area of blood flow sensing, however, we apply the algorithm to the displacement measurement of internal tissues. The comparison between the proposed method and the conventional method is presented. The fetal movement quantitative monitoring system based on the method which has been constructed is shown. 相似文献
95.
A new incoherent Doppler lidar scheme is proposed using a high resolution Mach-Zehnder interferometer discriminator with sinusoidal transmission functions. A two-channel differential discrimination technique is developed which provides high sensitive velocity measurement. The aerosol and molecular backscatter signals can be separately measured and the backscatter ratio obtained. Principle of the measurement is described and the characteristics of this technique are analyzed and compared. Numerical calculation for a moderate size 1.064 μ lidar shows that an accuracy better than 1 m/s for the velocity measurement and 18% for the backscatter ratio measurement can be obtained up to a height of 10 km by a 500 shot average. 相似文献
96.
TheOptimizationofthePDAOpticalSystem¥HOUQingwen;ZENGZhoumo;SUNJiazi;YANGXueyou(Dept.ofPrecisionInstrumentEngineering,TianjinU... 相似文献
97.
1IntroductionLaserDopplertechniqueisacomprehensivetechniquerelevanttooptics,laser,optoelectronicdetectingandsignalprocesing.... 相似文献
98.
99.
E. Masciadri A. Bassini S. Musazzi E. Paganini U. Perini 《Optics & Laser Technology》1996,28(7):497-501
In this paper we explore the possibility of utilizing commercially available photothermoplastic plates as recording support in Particle Image Velocimetry (PIV), to allow real time analysis of recorded data. An experimental apparatus has been developed which allows holographic recording and reconstruction of simulated PIV images. We show that double exposed photothermoplastic plates can successfully be analysed provided that a suitable recording/reconstruction scheme is used. 相似文献
100.
基于当前等离子体物理,本文初步讨论了低环径比托卡马克堆中等离子体的特征。在自洽的低环径比堆芯参数下,计算了α粒子约束和损失,以及不同环径比对它们的影响。 相似文献