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   1599583篇
  免费   28199篇
  国内免费   7061篇
电工技术   34866篇
综合类   6482篇
化学工业   261712篇
金属工艺   66480篇
机械仪表   47212篇
建筑科学   45432篇
矿业工程   11940篇
能源动力   50225篇
轻工业   122484篇
水利工程   16727篇
石油天然气   37542篇
武器工业   149篇
无线电   200384篇
一般工业技术   303467篇
冶金工业   219925篇
原子能技术   34801篇
自动化技术   175015篇
  2021年   14606篇
  2020年   12051篇
  2019年   14850篇
  2018年   19955篇
  2017年   19825篇
  2016年   23526篇
  2015年   17800篇
  2014年   28930篇
  2013年   88447篇
  2012年   39357篇
  2011年   55368篇
  2010年   47016篇
  2009年   54633篇
  2008年   50384篇
  2007年   48694篇
  2006年   47327篇
  2005年   43260篇
  2004年   44213篇
  2003年   43472篇
  2002年   40394篇
  2001年   37201篇
  2000年   34588篇
  1999年   35105篇
  1998年   60300篇
  1997年   47792篇
  1996年   39799篇
  1995年   34280篇
  1994年   31518篇
  1993年   31366篇
  1992年   26562篇
  1991年   23956篇
  1990年   24323篇
  1989年   23260篇
  1988年   21837篇
  1987年   20069篇
  1986年   19527篇
  1985年   22853篇
  1984年   22524篇
  1983年   20453篇
  1982年   19319篇
  1981年   19451篇
  1980年   18127篇
  1979年   18530篇
  1978年   17814篇
  1977年   18369篇
  1976年   20493篇
  1975年   16024篇
  1974年   15489篇
  1973年   15660篇
  1972年   13127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