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   1573649篇
  免费   28139篇
  国内免费   7083篇
电工技术   34418篇
综合类   6595篇
化学工业   259163篇
金属工艺   65539篇
机械仪表   45250篇
建筑科学   44899篇
矿业工程   11725篇
能源动力   50076篇
轻工业   122410篇
水利工程   16121篇
石油天然气   37168篇
武器工业   174篇
无线电   198244篇
一般工业技术   295994篇
冶金工业   214048篇
原子能技术   34467篇
自动化技术   172580篇
  2021年   14364篇
  2020年   12023篇
  2019年   14771篇
  2018年   18289篇
  2017年   17719篇
  2016年   22657篇
  2015年   17707篇
  2014年   28923篇
  2013年   88318篇
  2012年   38364篇
  2011年   52943篇
  2010年   45275篇
  2009年   52969篇
  2008年   48754篇
  2007年   46527篇
  2006年   46588篇
  2005年   41959篇
  2004年   43572篇
  2003年   42847篇
  2002年   40048篇
  2001年   36985篇
  2000年   34435篇
  1999年   34905篇
  1998年   58451篇
  1997年   46628篇
  1996年   38967篇
  1995年   33834篇
  1994年   31155篇
  1993年   31081篇
  1992年   26546篇
  1991年   23782篇
  1990年   24168篇
  1989年   23085篇
  1988年   21596篇
  1987年   19864篇
  1986年   19317篇
  1985年   22655篇
  1984年   22401篇
  1983年   20355篇
  1982年   19316篇
  1981年   19493篇
  1980年   18199篇
  1979年   18549篇
  1978年   17853篇
  1977年   18454篇
  1976年   20736篇
  1975年   16019篇
  1974年   15507篇
  1973年   15644篇
  1972年   13162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