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   37964篇
  免费   2776篇
  国内免费   1471篇
电工技术   1868篇
技术理论   2篇
综合类   2247篇
化学工业   6451篇
金属工艺   2128篇
机械仪表   2270篇
建筑科学   2960篇
矿业工程   925篇
能源动力   886篇
轻工业   2314篇
水利工程   533篇
石油天然气   2605篇
武器工业   202篇
无线电   4615篇
一般工业技术   4786篇
冶金工业   2086篇
原子能技术   404篇
自动化技术   4929篇
  2024年   148篇
  2023年   640篇
  2022年   961篇
  2021年   1450篇
  2020年   1078篇
  2019年   903篇
  2018年   977篇
  2017年   1167篇
  2016年   1047篇
  2015年   1365篇
  2014年   1742篇
  2013年   2212篇
  2012年   2151篇
  2011年   2451篇
  2010年   2214篇
  2009年   2037篇
  2008年   2026篇
  2007年   2009篇
  2006年   2033篇
  2005年   1769篇
  2004年   1203篇
  2003年   1042篇
  2002年   1011篇
  2001年   868篇
  2000年   898篇
  1999年   1093篇
  1998年   948篇
  1997年   828篇
  1996年   822篇
  1995年   631篇
  1994年   546篇
  1993年   379篇
  1992年   340篇
  1991年   255篇
  1990年   194篇
  1989年   168篇
  1988年   137篇
  1987年   104篇
  1986年   77篇
  1985年   58篇
  1984年   57篇
  1983年   30篇
  1982年   37篇
  1981年   24篇
  1980年   18篇
  1979年   11篇
  1977年   7篇
  1976年   7篇
  1973年   5篇
  1970年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
姚晓刚  王辉 《光电工程》1993,20(6):16-21
设计一电路,将彩色图象信息编码到黑白CRT的亮度之中,并将其写入液晶光阀,用白光读出,当编码合适时,读出的象颜色可与原图像一致。本文讨论了这一技术原理并进行了单液晶光阀彩色大屏幕投影的实验验证。  相似文献   
82.
本文提出一种测量孔边干涉螺接应力分布的新实验方法,用激光散斑干涉技术测量出由干涉螺接应力形成的孔周位移场分布,进而确定孔这应力分布,在保证测量精度同时,该方法体现出了简单,实用,有效等优点。  相似文献   
83.
84.
The fracture toughness J Ic (ρ) and fractal dimension D f of fractured surfaces of CuNiAl single crystal have been measured at temperatures in the range 20 °C to 120 °C, in which thermoelastic martensitic transformation takes place. The parent phase has higher fracture toughness than the martensite phase due to stress-induced transformation. The relationship between J Ic (ρ) and D f has been studied. It was found that log J Ic (ρ) is linearly related to D f if the failure involves a single mechanism. The slope of the plot may either be positive or negative for brittle or ductile failure, respectively. The difference in the J Ic (ρ)-D f correlation can be understood in terms of the micromechanism of fracture.  相似文献   
85.
Groups of algebraic integers used for coding QAM signals   总被引:2,自引:0,他引:2  
Linear block codes over Gaussian integers and Eisenstein integers were used for coding over two-dimensional signal space. A group of Gaussian integers with 22n elements was constructed to code quadrature amplitude modulation (QAM) signals such that a differentially coherent method can be applied to demodulate the QAM signals. This paper shows that one subgroup of the multiplicative group of units in the algebraic integer ring of any quadratic number field with unique factorization, modulo the ideal (Pn), can be used to obtain a QAM signal space of 2p2n-2 points, where p is any given odd prime number. Furthermore, one subgroup of the multiplicative group of units in the quotient ring Z[ω]/(pn) can be used to obtain a QAM signal space of 6p2n-2 points; one subgroup of the multiplicative group of units in the quotient ring Z[i](pn) can be used to obtain a QAM signal space of 4p2n-2 points which is symmetrical over the quadrants of the complex plane and useful for differentially coherent detection of QAM signals; the multiplicative group of units in the quotient ring Z[ω]/(2n) can be used to obtain a QAM signal space of 3·22n-2 points, where i=√-1, ω=(-1+√-3)/2=(-1+i√3)/2, p is any given odd prime number, Z[i] and Z[ω] are, respectively, the Gaussian integer ring and the Eisenstein integer ring. These multiplicative groups can also be used to construct block codes over Gaussian integers or Eisenstein integers which are able to correct some error patterns  相似文献   
86.
The techniques for image analysis and classification generally consider the image sample labels fixed and without uncertainties. The rank regression problem studied in this paper is based on the training samples with uncertain labels, which often is the case for the manual estimated image labels. A core ranking model is designed first as the bilinear fusing of multiple candidate kernels. Then, the parameters for feature selection and kernel selection are learned simultaneously by maximum a posteriori for given samples and uncertain labels. The provable convergency Expectation Maximization (EM) method is used for inferring these parameters in an iterative manner. The effectiveness of the proposed algorithm is finally validated by the extensive experiments on age ranking task and human tracking task. The popular FG-NET and the large scale Yamaha aging database are used for the age estimation experiments, and our algorithm outperforms those state-of-the-art algorithms ever reported by other interrelated literatures significantly. The experiment result of human tracking task also validates its advantage over conventional linear regression algorithm. A short version of this paper appeared in ICME07.  相似文献   
87.
Nonlinear boundary element analysis provides a more accurate and detailing tool for the design of switched reluctance machines than conventional equivalent-circuit methods. Design optimization through more detailed analysis and simulation can reduce development and prototyping costs and time to market. Firstly, magnetic field modeling of an industrial switched reluctance machine by the boundary element method is reported in this paper. Secondly, performance prediction and dynamic simulation of motor and control design are presented. Thirdly, magnetic forces that cause noise and vibration are studied, to include the effects of motor and control design variations on noise in the design process. Testing of such a motor in the NEMA 215-Frame size is carried out to verify the accuracy of modeling and simulation  相似文献   
88.
89.
用傅里叶变换红外扫描光致发光方法研究了Hg1-xCdxTe体单晶样品,该方法可直接得到HgCdTe晶片组分的二维平面分布,并可得到辐射复合在复合机制中所占比重的平面分布,以及晶体中非平衡载流子寿命的分布  相似文献   
90.
光纤智能复合材料   总被引:1,自引:0,他引:1  
唐见茂 《材料工程》1996,(6):45-48,F003
对光纤型智能复合材料的工作原理,性能特点和应用前景作了介绍,并讨论了制造成型的技术问题。  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