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   722篇
  免费   26篇
  国内免费   5篇
电工技术   9篇
化学工业   138篇
金属工艺   24篇
机械仪表   12篇
建筑科学   28篇
能源动力   44篇
轻工业   78篇
水利工程   6篇
石油天然气   5篇
无线电   74篇
一般工业技术   177篇
冶金工业   47篇
原子能技术   26篇
自动化技术   85篇
  2024年   3篇
  2023年   10篇
  2022年   25篇
  2021年   34篇
  2020年   26篇
  2019年   25篇
  2018年   33篇
  2017年   24篇
  2016年   29篇
  2015年   15篇
  2014年   30篇
  2013年   46篇
  2012年   39篇
  2011年   51篇
  2010年   27篇
  2009年   33篇
  2008年   36篇
  2007年   36篇
  2006年   27篇
  2005年   15篇
  2004年   14篇
  2003年   14篇
  2002年   18篇
  2001年   13篇
  2000年   10篇
  1999年   6篇
  1998年   11篇
  1997年   6篇
  1996年   5篇
  1995年   5篇
  1994年   10篇
  1993年   11篇
  1992年   8篇
  1991年   4篇
  1990年   6篇
  1989年   1篇
  1988年   9篇
  1987年   3篇
  1986年   1篇
  1985年   5篇
  1984年   7篇
  1983年   8篇
  1982年   2篇
  1981年   4篇
  1980年   3篇
  1979年   3篇
  1977年   1篇
  1973年   1篇
排序方式: 共有753条查询结果,搜索用时 0 毫秒
131.
In this paper, we establish a set of sufficient conditions for the controllability of damped second-order impulsive neutral integrodifferential systems with nonlocal initial conditions in Banach spaces. The approach used is the Sadovskii fixed point theorem combined with a noncompact condition on the cosine family of operators. An example is presented to illustrate the result.  相似文献   
132.
The effects of different types of variations in profile and thickness on the amplitude and the dynamic bending stresses of a square cantilever plate excited by a point harmonic load resonance has been investigated. A four-noded plate bending element has been used for the analysis. The response has been determined for the first three modes of vibration. In each case the results obtained for different thickness variations are compared with those of the uniform thickness plate. It is observed that considerable reductions in amplitude and/or bending stresses can be achieved by the proper selection of thickness variation.  相似文献   
133.
Equilibrium phase fields of the ternary Pb-Bi-O system were established by long-term equilibration in the temperature range 660-840 K. Using these results, the partial phase diagram of the ternary system has been constructed. The standard molar Gibbs energy of formation of the ternary oxides, 〈Pb5Bi8O17〉 and 〈PbBi12O19〉, was determined by measuring the equilibrium oxygen partial pressures over the relevant phase fields by static manometry in conjunction with a solid oxide electrolyte-based emf cell. Further, the standard molar Gibbs energy of formation of 〈Pb3O4〉 was also measured by the manometric method. The oxide that coexists with the Pb-Bi eutectic alloy (LBE) has been experimentally confirmed as [β-PbO]ss. Using the thermochemical data measured, the compositions of Pb-Bi alloys that coexist with [β-PbO]ss and ternary oxides were derived and reported.  相似文献   
134.
The influence of temperature and thickness on the electrical transport properties of 10% excess tin-doped polycrystalline SnTe thin films were investigated. From the observed variation of electrical resistivity and Seebeck coefficient it is concluded that the material exhibits a p-type degenerate behaviour. Using the size effect data, different physical parameters such as Fermi energy, effective mass and scattering parameter were evaluated and compared with the results on SnTe thin films to understand the effect of excess tin.  相似文献   
135.
Vibrations of skew plates immersed in water have been studied in the present work. Two skew prism fluid elements have been developed for the above study. As there is no information available on them, a few experiments have been conducted to measure the frequencies of vibration of these plates immersed in water. The results of both the theoretical and experimental investigations have been compared and found to be agreeing reasonably well. The general findings of these plates regarding their aspect ratios, thickness ratios and boundary conditions are discussed. In addition, the influence of skew angles on the vibration of skew plates have been investigated. It has been noticed that the effect of added mass is found to decrease with the increase of skew angle.  相似文献   
136.
137.
An 8-MHz seventh-degree elliptic-function low-pass filter is described, demonstrating an approach to low-distortion antialias filtering for high-definition video applications. The filter's performance goals are achieved through the use of circuit design principles that capitalize on the strengths of BiCMOS technology. The integrator circuits composing the filter consist of a new wideband low-distortion transconductor circuit and a unique BiCMOS Miller-stage circuit. Integrator time constants are determined by stable RC products, enabling a simplified filter calibration scheme that is insensitive to temperature-induced variations and requires no phaselock circuits. The prototype filter IC, consisting of seven integrators assembled in an active-ladder configuration, was fabricated in a 10-V, 2-μm 2.5-GHz BiCMOS technology that also features thin-film resistors and polysilicon-plate capacitors. Measured results from the calibrated filter show passband flatness of 0.2 dB, with aberrations of less than ±1 dB over a 100°C temperature range. Stopband attenuation meets its designed goal of 60 dB. Driven by 7-Vpp, differential input signals, the filter exhibits less than -72-dBc third-order intermodulation distortion products at 1 MHz. For 5-Vpp inputs at 4 MHz, third-order intermodulation spurs remain below -65 dBc  相似文献   
138.
The photographic negative-mask method of neutralizing the diffraction-halo effect in speckle photography is applied to enhance the quality of Young's fringes obtained in particle-image-velocimetry studies. The improvement of the fringes achieved with the negative-mask method is compared with improvements by the commonly used method of analyzing a contact copy of particle-image-velocimetry specklegrams. Theoretical analysis and experimental results are presented.  相似文献   
139.
Multimedia Tools and Applications - With the fast growing technologies in the field of remote sensing, hyperspectral image analysis has made a great breakthrough. It provides accurate and detailed...  相似文献   
140.
Multimedia Tools and Applications - Digital images are widely distributed today over the internet and through other mediums. There are powerful digital image processing tools which have made...  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