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   293795篇
  免费   5049篇
  国内免费   1309篇
电工技术   5385篇
综合类   1274篇
化学工业   43046篇
金属工艺   10613篇
机械仪表   9457篇
建筑科学   8204篇
矿业工程   1161篇
能源动力   7607篇
轻工业   30142篇
水利工程   2709篇
石油天然气   2975篇
武器工业   18篇
无线电   39677篇
一般工业技术   53907篇
冶金工业   51181篇
原子能技术   3868篇
自动化技术   28929篇
  2022年   3792篇
  2021年   5591篇
  2020年   4330篇
  2019年   5427篇
  2018年   3801篇
  2017年   3392篇
  2016年   3368篇
  2015年   2625篇
  2014年   4132篇
  2013年   12802篇
  2012年   7423篇
  2011年   11321篇
  2010年   8799篇
  2009年   9873篇
  2008年   9706篇
  2007年   9679篇
  2006年   9142篇
  2005年   8466篇
  2004年   9265篇
  2003年   8951篇
  2002年   8318篇
  2001年   8256篇
  2000年   6873篇
  1999年   7260篇
  1998年   16821篇
  1997年   11719篇
  1996年   8720篇
  1995年   6943篇
  1994年   6262篇
  1993年   5957篇
  1992年   4360篇
  1991年   4046篇
  1990年   3852篇
  1989年   3768篇
  1988年   3565篇
  1987年   2811篇
  1986年   2811篇
  1985年   3448篇
  1984年   2995篇
  1983年   2841篇
  1982年   2630篇
  1981年   2572篇
  1980年   2336篇
  1979年   2178篇
  1978年   2087篇
  1977年   2463篇
  1976年   2922篇
  1975年   1786篇
  1974年   1653篇
  1973年   1654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