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   1610768篇
  免费   28506篇
  国内免费   7007篇
电工技术   34329篇
综合类   6599篇
化学工业   260686篇
金属工艺   65526篇
机械仪表   45663篇
建筑科学   45997篇
矿业工程   11664篇
能源动力   50132篇
轻工业   127278篇
水利工程   16569篇
石油天然气   36892篇
武器工业   158篇
无线电   198924篇
一般工业技术   302735篇
冶金工业   233533篇
原子能技术   34347篇
自动化技术   175249篇
  2021年   14464篇
  2020年   12104篇
  2019年   14857篇
  2018年   17985篇
  2017年   17338篇
  2016年   22753篇
  2015年   17825篇
  2014年   29107篇
  2013年   88643篇
  2012年   39506篇
  2011年   54175篇
  2010年   45384篇
  2009年   52709篇
  2008年   49804篇
  2007年   47563篇
  2006年   47703篇
  2005年   42688篇
  2004年   44509篇
  2003年   43828篇
  2002年   40903篇
  2001年   38133篇
  2000年   35266篇
  1999年   36081篇
  1998年   64272篇
  1997年   50394篇
  1996年   41540篇
  1995年   35492篇
  1994年   32618篇
  1993年   32341篇
  1992年   27015篇
  1991年   24356篇
  1990年   24598篇
  1989年   23582篇
  1988年   22103篇
  1987年   20334篇
  1986年   19853篇
  1985年   23192篇
  1984年   22778篇
  1983年   20679篇
  1982年   19516篇
  1981年   19676篇
  1980年   18356篇
  1979年   18769篇
  1978年   18030篇
  1977年   19009篇
  1976年   22091篇
  1975年   16121篇
  1974年   15607篇
  1973年   15728篇
  1972年   13272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