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   19178篇
  免费   1786篇
  国内免费   565篇
电工技术   932篇
技术理论   1篇
综合类   779篇
化学工业   4156篇
金属工艺   907篇
机械仪表   1031篇
建筑科学   926篇
矿业工程   281篇
能源动力   811篇
轻工业   1670篇
水利工程   212篇
石油天然气   600篇
武器工业   112篇
无线电   2652篇
一般工业技术   3240篇
冶金工业   792篇
原子能技术   226篇
自动化技术   2201篇
  2024年   46篇
  2023年   260篇
  2022年   506篇
  2021年   745篇
  2020年   578篇
  2019年   584篇
  2018年   608篇
  2017年   660篇
  2016年   685篇
  2015年   716篇
  2014年   1056篇
  2013年   1253篇
  2012年   1351篇
  2011年   1539篇
  2010年   1308篇
  2009年   1207篇
  2008年   1127篇
  2007年   961篇
  2006年   877篇
  2005年   791篇
  2004年   599篇
  2003年   572篇
  2002年   577篇
  2001年   473篇
  2000年   379篇
  1999年   372篇
  1998年   344篇
  1997年   247篇
  1996年   181篇
  1995年   170篇
  1994年   135篇
  1993年   103篇
  1992年   98篇
  1991年   55篇
  1990年   64篇
  1989年   60篇
  1988年   28篇
  1987年   31篇
  1986年   20篇
  1985年   15篇
  1984年   25篇
  1983年   22篇
  1982年   11篇
  1981年   20篇
  1980年   12篇
  1979年   6篇
  1978年   7篇
  1977年   12篇
  1976年   14篇
  1975年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The transmission mode of holographic polymer‐dispersed liquid crystals (HPDLCs) was developed an under electric field. It is reported that orientation of LC molecules under an electric field induces orientation of oligomer molecules giving rise to low off‐state diffraction and small grating shrinkage. Copyright © 2005 Society of Chemical Industry  相似文献   
2.
Biodegradable multiblock poloxamers (BMPs) with gel duration of 8 h to several weeks were prepared by varying their molecular weights from 4000 to 40 000 g mol?1. The molecular weight of the BMP was controlled by changing the poloxamer to coupling agent ratio. Assuming a micelle packing model of the BMP gel, as in the case of a poloxamer gel, the micelle properties and critical gel concentration of BMPs were investigated on the basis of the scaling concept. The findings suggest that the control of molecular weight by hydrolyzable groups can be a facile approach to optimize the gel properties for biomedical applications. Copyright © 2005 Society of Chemical Industry  相似文献   
3.
4.
鞠洪振 《中国橡胶》2008,24(20):4-9
2004年6月至2008年6月,第六届理事会任期届满。这四年,橡胶行业确立了以实施科学发展、名牌战略和循环经济为基本指导方针;这四年,协会不断改革,加强建设,强化了服务宗旨;这四年,自主创新成为橡胶工业可持续发展的主旋律。  相似文献   
5.
Human facial gestures often exhibit such natural stochastic variations as how often the eyes blink, how often the eyebrows and the nose twitch, and how the head moves while speaking. The stochastic movements of facial features are key ingredients for generating convincing facial expressions. Although such small variations have been simulated using noise functions in many graphics applications, modulating noise functions to match natural variations induced from the affective states and the personality of characters is difficult and not intuitive. We present a technique for generating subtle expressive facial gestures (facial expressions and head motion) semi‐automatically from motion capture data. Our approach is based on Markov random fields that are simulated in two levels. In the lower level, the coordinated movements of facial features are captured, parameterized, and transferred to synthetic faces using basis shapes. The upper level represents independent stochastic behavior of facial features. The experimental results show that our system generates expressive facial gestures synchronized with input speech.  相似文献   
6.
ZnO thin film was deposited on various metal electrodes by reactive sputtering, and c-axis preferred orientation of the film has been studied. ZnO, which has high piezoelectricity, is promising for oscillators or filter devices such as surface acoustic wave (SAW) device, gas sensor, and film bulk acoustic resonator (FBAR). But, for the application of ZnO film for these devices, the film should be grown with c-axis normal to the electrode. In this study, Pt, Al, and Au were deposited on Si wafer, and the surface roughness and crystal structure of the ZnO film on the electrode were investigated using AFM, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Columnar structures of ZnO films were grown with c-axis normal to all electrodes, and among them Pt electrode showed the highest preferred orientation of ZnO film.  相似文献   
7.
8.
Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches.  相似文献   
9.
本工作中我们选择了B2O3-La2O3-Y2O2-ZrO2系统作为玻璃基础组成。最后获得的LaK747/509玻璃组成中,不含有钍的成份。由于该玻璃具有一系列好的性质,如析晶范围窄、析晶速度慢以及粘度大等等,因此可以成功地在12-30L铂埚中进行熔制,并获得了尺寸为φ200×25mm的高质量玻璃。  相似文献   
10.
For multi-step heterogeneous consecutive reactions affected entirely by interphase diffusion under isothermal condition, the equations for the effectiveness factors, the surface concentrations and the point yields were derived in terms of the Damkoehler numbers or the measurables from the mass balances set up on the assumption that the mass-transfer rate balances the surface-reaction rate at steady state. From the analyses of the equations derived, the effectiveness factors for the intermediate steps and the surface concentrations of intermediates were understood to be enhanced by the measurables inclusive of the concentrations and the mass-transfer coefficients. Then the effect of the concentrations was concluded to be most significant. The effects of these measurables to the effectiveness factors and the surface concentrations were qualitatively discussed for simple consecutive reactions and also for additive consecutive reactions. Especially, as for two-step additive consecutive reactions, the effects of measurables η Da and the concentrations to the effectiveness factors were examined with graphical presentations. Finally, the brief discussion of the dependency of the Damkoehler number upon reaction time and the effect of the Renolds number and diffusivity to the extent of the mass-transfer resistance were presented.  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