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   200176篇
  免费   2348篇
  国内免费   606篇
电工技术   3477篇
综合类   153篇
化学工业   29039篇
金属工艺   8054篇
机械仪表   6078篇
建筑科学   4836篇
矿业工程   1303篇
能源动力   5156篇
轻工业   17172篇
水利工程   2313篇
石油天然气   4044篇
武器工业   8篇
无线电   23133篇
一般工业技术   40127篇
冶金工业   37269篇
原子能技术   5091篇
自动化技术   15877篇
  2021年   1671篇
  2019年   1569篇
  2018年   2574篇
  2017年   2647篇
  2016年   2778篇
  2015年   1794篇
  2014年   3077篇
  2013年   8943篇
  2012年   5053篇
  2011年   7022篇
  2010年   5593篇
  2009年   6352篇
  2008年   6448篇
  2007年   6515篇
  2006年   5581篇
  2005年   5232篇
  2004年   5018篇
  2003年   4910篇
  2002年   4531篇
  2001年   4659篇
  2000年   4580篇
  1999年   4730篇
  1998年   11387篇
  1997年   8131篇
  1996年   6418篇
  1995年   4678篇
  1994年   4277篇
  1993年   4080篇
  1992年   3226篇
  1991年   3081篇
  1990年   2871篇
  1989年   2954篇
  1988年   2828篇
  1987年   2401篇
  1986年   2309篇
  1985年   2715篇
  1984年   2505篇
  1983年   2346篇
  1982年   2091篇
  1981年   2204篇
  1980年   2031篇
  1979年   2126篇
  1978年   2120篇
  1977年   2367篇
  1976年   3192篇
  1975年   1833篇
  1974年   1764篇
  1973年   1774篇
  1972年   1445篇
  1971年   1341篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Glass and Ceramics - A catalyst was developed in the form of a composite based on a zeolite matrix modified with titanium nanoparticles based on zeolite raw materials from the Kulikovskoe deposit...  相似文献   
82.
Glass and Ceramics - The granulometric compositions of native and acid-activated rocks containing aluminosilicates are compared. It is shown that in water rocks gradually dissolve and the particle...  相似文献   
83.
Russian Engineering Research - Polymer samples based on polydicyclopentadiene produced from Russian dicyclopentadiene are investigated by thermogravimetric analysis and differential scanning...  相似文献   
84.
85.
Composites comprising Poly(Methyl Methacrylate) (PMMA) and CaCu3Ti4O12 (CCTO) via melt mixing followed by hot pressing were fabricated. These were characterized using X‐ray diffraction, thermo gravimetric, scanning electron microscopy, and Impedance analyzer for their structural, morphology, and dielectric properties. Composites were found to have better thermal stability than that of pure PMMA. The composite, with 38 Vol % of CCTO (in PMMA), exhibited remarkably low dielectric loss at high frequencies and the low frequency relaxation is attributed to the space charge polarization/MWS effect. Theoretical models were employed to rationalize the dielectric behavior of these composites. At higher temperatures, the relaxation peak shifts to higher frequencies, due to the merging of both β and α relaxations into a single dielectric dispersion peak. The AC conductivity in the high frequency region was attributed to the electronic polarization. POLYM. ENG. SCI., 54:551–558, 2014. © 2013 Society of Plastics Engineers  相似文献   
86.
Toughness of rigid thermoplastic is an important mechanical property in polymer technology. In the present study, toughening of waste polypropylene (WPP) with ethylene–propylene–diene monomer (EPDM) rubber at different loading levels was carried out by melt blending at 180 °C. The EPDM-toughened WPP samples were characterized for its thermo-mechanical properties. The effect of carbon black (5 wt%) as a functional filler in WPP/EPDM to impart UV protection was also studied. The test sheets were subjected to natural weathering in variable climatic conditions for a 4-month period of time and were taken out at regular intervals for characterization. The waste PP underwent excessive degradation as the mechanical strength properties such as tensile, flexural and impact strengths were reduced drastically. On the other hand, WPP containing varying proportions of EPDM and carbon black showed better retention of strength properties. The percentage degree of crystallinity has been unusually increased after the environmental degradation due to chemi-crystallization. The impact-modified WPP which contains carbon black retained the processability even after the environmental aging. After aging, the non-stabilized systems were shown extensive change, whereas the structural integrity has been well retained of the toughened WPP containing carbon black as was evident from SEM and optical photomicroscopy.  相似文献   
87.
Poorvasha  S.  Lakshmi  B. 《SILICON》2022,14(4):1479-1488
Silicon - This paper presents the analytical approximation of device physics of heterojunction based double gate (DG) Tunnel field effect transistors (TFETs) in terms of potential distribution,...  相似文献   
88.
Samal  Priyaranjan  Surekha  B.  Vundavilli  Pandu R. 《SILICON》2022,14(7):3317-3328
Silicon - Aluminum metal matrix composites (MMCs) exhibit promising mechanical properties that are potential materials for the aeronautical and automotive industries. In this study,...  相似文献   
89.
Metal Science and Heat Treatment - The nature of stability of dendritic microsegregation of rhenium in single crystals of intermetallic (γ′ + γ) alloys based on γ′-Ni3Al...  相似文献   
90.
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