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   318090篇
  免费   4332篇
  国内免费   1026篇
电工技术   4595篇
综合类   2481篇
化学工业   49020篇
金属工艺   15636篇
机械仪表   10568篇
建筑科学   7888篇
矿业工程   2953篇
能源动力   6700篇
轻工业   18877篇
水利工程   4460篇
石油天然气   8243篇
武器工业   24篇
无线电   32531篇
一般工业技术   65627篇
冶金工业   43250篇
原子能技术   7166篇
自动化技术   43429篇
  2021年   2407篇
  2020年   1876篇
  2019年   2387篇
  2018年   18237篇
  2017年   17183篇
  2016年   14212篇
  2015年   3259篇
  2014年   4689篇
  2013年   10966篇
  2012年   9881篇
  2011年   17787篇
  2010年   14963篇
  2009年   13020篇
  2008年   14522篇
  2007年   15347篇
  2006年   6867篇
  2005年   7380篇
  2004年   6691篇
  2003年   6632篇
  2002年   5869篇
  2001年   5175篇
  2000年   4951篇
  1999年   4814篇
  1998年   10812篇
  1997年   7685篇
  1996年   6115篇
  1995年   4670篇
  1994年   4120篇
  1993年   4359篇
  1992年   3455篇
  1991年   3325篇
  1990年   3310篇
  1989年   3264篇
  1988年   3235篇
  1987年   2924篇
  1986年   2937篇
  1985年   3353篇
  1984年   3160篇
  1983年   2983篇
  1982年   2756篇
  1981年   2704篇
  1980年   2690篇
  1979年   2716篇
  1978年   2707篇
  1977年   2788篇
  1976年   3143篇
  1975年   2499篇
  1974年   2307篇
  1973年   2434篇
  1972年   2091篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
2.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
3.
4.
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   
5.
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   
6.
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   
7.
Cell surface proteoglycans are known to be important regulators of many aspects of cell behavior. The principal family of transmembrane proteoglycans is the syndecans, of which there are four in mammals. Syndecan-1 is mostly restricted to epithelia, and bears heparan sulfate chains that are capable of interacting with a large array of polypeptides, including extracellular matrix components and potent mediators of proliferation, adhesion and migration. For this reason, it has been studied extensively with respect to carcinomas and tumor progression. Frequently, but not always, syndecan-1 levels decrease as tumor grade, stage and invasiveness and dedifferentiation increase. This parallels experiments that show depletion of syndecan-1 can be accompanied by loss of cadherin-mediated adhesion. However, in some tumors, levels of syndecan-1 increase, but the characterization of its distribution is relevant. There can be loss of membrane staining, but acquisition of cytoplasmic and/or nuclear staining that is abnormal. Moreover, the appearance of syndecan-1 in the tumor stroma, either associated with its cellular component or the collagenous matrix, is nearly always a sign of poor prognosis. Given its relevance to myeloma progression, syndecan-1-directed antibody—toxin conjugates are being tested in clinical and preclinical trials, and may have future relevance to some carcinomas.  相似文献   
8.
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   
9.
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   
10.
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   
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