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   1505947篇
  免费   27778篇
  国内免费   7010篇
电工技术   33906篇
综合类   6552篇
化学工业   255144篇
金属工艺   63954篇
机械仪表   42897篇
建筑科学   43885篇
矿业工程   11490篇
能源动力   49834篇
轻工业   115031篇
水利工程   15557篇
石油天然气   36534篇
武器工业   188篇
无线电   196074篇
一般工业技术   286583篇
冶金工业   179237篇
原子能技术   33966篇
自动化技术   169903篇
  2021年   14434篇
  2020年   11901篇
  2019年   14700篇
  2018年   16036篇
  2017年   15406篇
  2016年   21579篇
  2015年   17414篇
  2014年   28784篇
  2013年   87883篇
  2012年   36551篇
  2011年   49517篇
  2010年   42990篇
  2009年   51063篇
  2008年   46027篇
  2007年   43373篇
  2006年   45914篇
  2005年   40088篇
  2004年   42109篇
  2003年   41621篇
  2002年   38984篇
  2001年   36057篇
  2000年   33573篇
  1999年   33448篇
  1998年   48177篇
  1997年   40406篇
  1996年   34939篇
  1995年   31485篇
  1994年   29319篇
  1993年   29105篇
  1992年   26028篇
  1991年   23302篇
  1990年   23594篇
  1989年   22412篇
  1988年   21084篇
  1987年   19333篇
  1986年   18868篇
  1985年   22201篇
  1984年   22252篇
  1983年   20207篇
  1982年   19106篇
  1981年   19192篇
  1980年   17848篇
  1979年   18440篇
  1978年   17651篇
  1977年   17542篇
  1976年   18685篇
  1975年   15890篇
  1974年   15464篇
  1973年   15552篇
  1972年   13044篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Materials Science -  相似文献   
2.
Photonic Network Communications - In the present work, a high-speed optical encoder is proposed based on two-dimensional photonic crystal ring resonator using coupled mode theory and resonance...  相似文献   
3.
Anzaldo  Alexis  Andrade  Ángel G. 《Wireless Networks》2022,28(8):3613-3620
Wireless Networks - Beyond five generation (B5G) systems will demand strict and heterogeneous service requirements for the emerging applications. One solution to meet these demands is the dense...  相似文献   
4.
Journal of Materials Science: Materials in Electronics - The Co1?xZnxFe2O4 (Co–Zn) ferrite nanoparticles with x varying from 0.0 to 0.4 have been manufactured by facile chemical...  相似文献   
5.
Journal of Materials Science: Materials in Electronics - The ZnO and TiO2 nanopowders have been prepared by means of the pulsed laser reactive ablation of metallic (Zn, Ti) targets. The Structural,...  相似文献   
6.
Journal of Materials Science: Materials in Electronics - Non-volatile organic memory devices were fabricated using polystyrene sulfonate (PSS)?+?nitrogen-doped multi-walled carbon...  相似文献   
7.

InN thin films are grown on sapphire substrates by remote plasma-assisted metal organic chemical vapor deposition while varying the indium pulse length and substrate temperature. The effects of the indium pulse length and temperature on the structural, morphological, electronic, and optical properties of the thin films are studied. The structural parameters are determined by X-ray diffraction and X-ray photoelectron spectroscopy and the effects of incorporating oxygen atoms in the structure is described. The N K-edge X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) measurements are used to determine the band gap and it is found to be 1.80?±?0.25 eV for all samples. A complementary measurement namely, X-ray excited optical luminescence measurement is performed to confirm the band gap value obtained from XAS and XES measurements. O K-edge XAS measurements are performed to determine the presence of oxygen impurities in the samples. Meanwhile, we carry out the density functional theory calculations for Wurtzite InN, hypothetical Wurtzite-type InO0.5N0.5, and InO0.0625N0.9375 structures. We find that the measured N-edge spectra agree well with our Wurtzite InN calculations and the measured O K-edge spectra agree better with hypothetical Wurtzite-type InO0.0625N0.9375 than Wurtzite-type InO0.5N0.5.

  相似文献   
8.
Journal of Materials Science: Materials in Electronics - In the recent years, metal oxides have attracted more interest for researchers because of their applications in energy and...  相似文献   
9.
Journal of Materials Science: Materials in Electronics - A mixed solution of 2-aminopyridine and succinic acid, with a 1:1 molar ratio, was kept at room temperature to develop a 2-aminopridinium...  相似文献   
10.

The non-centrosymmetric space group organic nonlinear optical single crystal of 4-chloro-2-nitroaniline (4Cl2NA) was developed by slow evaporation method at 40 °C. Grown 4Cl2NA was monoclinic structure with Pc space group which was recognized by single-crystal XRD analysis. An intermolecular contact of 4Cl2NA was visually analysed by Hirshfeld surface analysis. Active functional groups and their respective vibrations were identified by FTIR and FT-Raman spectral analysis. Optical properties were evaluated by UV–Visible spectral analysis. Thermal TG/DTA thermogram analysis and mechanical Vickers hardness analysis revealed that the synthesis material was thermally stable up to 115 °C and mechanical work hardness coefficient (n?=?2.98) confirmed the grown crystal was soft material. Laser beam-irradiated LDT analysis expressed the laser utility limitation of the 4Cl2NA crystal. The NLO second harmonic generation efficiency was tested by Kurtz Perry powder method.

  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