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   317086篇
  免费   6022篇
  国内免费   1339篇
电工技术   5647篇
综合类   1319篇
化学工业   47618篇
金属工艺   11095篇
机械仪表   9873篇
建筑科学   9806篇
矿业工程   1220篇
能源动力   8243篇
轻工业   31997篇
水利工程   2924篇
石油天然气   3052篇
武器工业   29篇
无线电   41225篇
一般工业技术   58362篇
冶金工业   54832篇
原子能技术   3997篇
自动化技术   33208篇
  2022年   3897篇
  2021年   6114篇
  2020年   4714篇
  2019年   5861篇
  2018年   4342篇
  2017年   3871篇
  2016年   4028篇
  2015年   3231篇
  2014年   4892篇
  2013年   14280篇
  2012年   8699篇
  2011年   12977篇
  2010年   9937篇
  2009年   10968篇
  2008年   11046篇
  2007年   10951篇
  2006年   10218篇
  2005年   9394篇
  2004年   10117篇
  2003年   9711篇
  2002年   9323篇
  2001年   8607篇
  2000年   7198篇
  1999年   7590篇
  1998年   17019篇
  1997年   11956篇
  1996年   8981篇
  1995年   7243篇
  1994年   6535篇
  1993年   6224篇
  1992年   4624篇
  1991年   4191篇
  1990年   4073篇
  1989年   3976篇
  1988年   3756篇
  1987年   3028篇
  1986年   3018篇
  1985年   3669篇
  1984年   3170篇
  1983年   3024篇
  1982年   2792篇
  1981年   2724篇
  1980年   2453篇
  1979年   2298篇
  1978年   2211篇
  1977年   2526篇
  1976年   2987篇
  1975年   1882篇
  1974年   1726篇
  1973年   1712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.
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   
4.
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   
5.
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   
6.
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   
7.
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   
8.

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   
9.
Journal of Engineering Physics and Thermophysics - The generalized nonlocal thermoelastic model in the context of Eringen’s nonlocal elasticity is applied to investigate the...  相似文献   
10.
This study was conducted to evaluate the effect of red-wine grape pomaces on the quality and sensory attributes of beef hamburger patties. Both phenolic content and antioxidant activity were assessed using Syrah, Merlot and Cabernet Sauvignon pomaces. Following the assessment, hamburger patties were prepared with Merlot pomace at 0%, 2% and 4% for the patty quality and sensory attributes. Grape seeds possessed significantly higher phenolics and antioxidant activities over the seedless pomace (P < 0.05), whereas no significant difference was found for phenolics and antioxidant activities within the seeds and seedless pomaces. The patty pH decreased as the pomace was added for 2% and 4%. Colour values (L*, a* and b*) of patties lowered as the pomace was added. Allo-Kramer shear force and hardness values increased while cooking yield decreased (P < 0.05) with the addition of pomace. No significant difference between control and Merlot patties was found for flavour, juiciness and colour, whereas lower sensory attributes were observed for texture, taste and overall acceptability. It is observed that the addition of fermented red-wine grape pomace provides hamburger patties with health promoting factors such as antioxidant and other functional components, but it also provided darker, sourer and lower cooking yield.  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