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   206986篇
  免费   2503篇
  国内免费   561篇
电工技术   3512篇
综合类   140篇
化学工业   32249篇
金属工艺   10279篇
机械仪表   7038篇
建筑科学   4021篇
矿业工程   2161篇
能源动力   4656篇
轻工业   13185篇
水利工程   2924篇
石油天然气   7729篇
武器工业   22篇
无线电   21506篇
一般工业技术   45308篇
冶金工业   34446篇
原子能技术   6623篇
自动化技术   14251篇
  2021年   2122篇
  2019年   2050篇
  2018年   3724篇
  2017年   3758篇
  2016年   4063篇
  2015年   2268篇
  2014年   3834篇
  2013年   8833篇
  2012年   5753篇
  2011年   7304篇
  2010年   5913篇
  2009年   6531篇
  2008年   6661篇
  2007年   6524篇
  2006年   5600篇
  2005年   5155篇
  2004年   4652篇
  2003年   4574篇
  2002年   4391篇
  2001年   4486篇
  2000年   4195篇
  1999年   4204篇
  1998年   10196篇
  1997年   7196篇
  1996年   5505篇
  1995年   4135篇
  1994年   3602篇
  1993年   3847篇
  1992年   2983篇
  1991年   2999篇
  1990年   2894篇
  1989年   2858篇
  1988年   2868篇
  1987年   2511篇
  1986年   2569篇
  1985年   2857篇
  1984年   2689篇
  1983年   2555篇
  1982年   2302篇
  1981年   2269篇
  1980年   2346篇
  1979年   2361篇
  1978年   2382篇
  1977年   2490篇
  1976年   2879篇
  1975年   2188篇
  1974年   2068篇
  1973年   2166篇
  1972年   1940篇
  1971年   1755篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
4.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...  相似文献   
5.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
6.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
7.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  相似文献   
8.
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C.  相似文献   
9.
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability.  相似文献   
10.
Automation and Remote Control - A linear-quadratic positional differential game of three persons is considered. Coefficient criteria are established under which there is no Nash equilibrium...  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