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   260371篇
  免费   2333篇
  国内免费   319篇
电工技术   4280篇
综合类   107篇
化学工业   42376篇
金属工艺   15477篇
机械仪表   10359篇
建筑科学   4376篇
矿业工程   3825篇
能源动力   4520篇
轻工业   10815篇
水利工程   4240篇
石油天然气   13074篇
武器工业   28篇
无线电   21691篇
一般工业技术   65235篇
冶金工业   33566篇
原子能技术   11313篇
自动化技术   17741篇
  2021年   3244篇
  2019年   3125篇
  2018年   5953篇
  2017年   6194篇
  2016年   6491篇
  2015年   3306篇
  2014年   5736篇
  2013年   10877篇
  2012年   7769篇
  2011年   9557篇
  2010年   7796篇
  2009年   8583篇
  2008年   8603篇
  2007年   8202篇
  2006年   6640篇
  2005年   5792篇
  2004年   5692篇
  2003年   5495篇
  2002年   5286篇
  2001年   5073篇
  2000年   5061篇
  1999年   4392篇
  1998年   7494篇
  1997年   6048篇
  1996年   4654篇
  1995年   3849篇
  1994年   3582篇
  1993年   3766篇
  1992年   3335篇
  1991年   3495篇
  1990年   3579篇
  1989年   3466篇
  1988年   3376篇
  1987年   3362篇
  1986年   3240篇
  1985年   3422篇
  1984年   3336篇
  1983年   3238篇
  1982年   3078篇
  1981年   3125篇
  1980年   3142篇
  1979年   3302篇
  1978年   3527篇
  1977年   3511篇
  1976年   3980篇
  1975年   3239篇
  1974年   3321篇
  1973年   3369篇
  1972年   3005篇
  1971年   2767篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Wireless Personal Communications - Besides anti-malware usage for the eradication of malicious attacks, researchers have developed epidemic models in order to gain more insights into the spread...  相似文献   
13.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
14.
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically...  相似文献   
15.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is...  相似文献   
16.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  相似文献   
17.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the...  相似文献   
18.
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability.  相似文献   
19.
Automation and Remote Control - A linear-quadratic positional differential game of three persons is considered. Coefficient criteria are established under which there is no Nash equilibrium...  相似文献   
20.
A promising electrocatalyst containing variable percentage of V2O5–TiO2 mixed oxide in graphene oxide support was prepared by embedding the catalyst on Cu substrate through facile electroless Ni–Co–P plating for hydrogen evolution reaction. The solvothermal decomposition method was opted for tuning the crystalline characteristics of prepared material. The optimized mixed oxide was well characterized, active sites centres were identified and explained by X-ray diffraction, high resolution tunnelling electron microscopy, scanning electron microscopy coupled with energy dispersive X-ray and X-ray photon spectroscopy analysis. The structural and electronic characteristics of material was done by fourier transform infrared spectroscopy and the electrochemical behaviour of the prepared material was evaluated by using Tafel plot, electrochemical impedance analysis, linear sweep voltammetry, open circuit analysis and chronoamperometry measurements. The results show the enhanced catalytic activity of Ni–Co–P than pure Ni–P plate, due to synergic effect. Moreover, the prepared mixed oxide incorporated Ni–Co–P plate has a high activity towards HER with low over potential of 101 mV, low Tafel slope of 36 mVdec?1, high exchange current density of 9.90 × 10?2 Acm?2.  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