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   1544610篇
  免费   37511篇
  国内免费   12463篇
化学   672173篇
晶体学   20458篇
力学   76022篇
综合类   238篇
数学   242686篇
物理学   377638篇
无线电   205369篇
  2021年   16162篇
  2020年   18654篇
  2019年   18867篇
  2018年   14384篇
  2016年   31136篇
  2015年   23281篇
  2014年   34720篇
  2013年   81045篇
  2012年   42309篇
  2011年   38694篇
  2010年   41353篇
  2009年   46380篇
  2008年   41451篇
  2007年   37881篇
  2006年   44964篇
  2005年   36684篇
  2004年   37768篇
  2003年   35550篇
  2002年   36598篇
  2001年   35233篇
  2000年   31508篇
  1999年   29426篇
  1998年   28008篇
  1997年   27833篇
  1996年   27469篇
  1995年   25204篇
  1994年   24553篇
  1993年   23821篇
  1992年   23401篇
  1991年   23602篇
  1990年   22304篇
  1989年   21874篇
  1988年   20941篇
  1987年   19720篇
  1986年   18542篇
  1985年   25081篇
  1984年   26230篇
  1983年   22214篇
  1982年   23658篇
  1981年   22843篇
  1980年   22072篇
  1979年   21912篇
  1978年   23195篇
  1977年   22742篇
  1976年   22339篇
  1975年   21002篇
  1974年   20607篇
  1973年   21137篇
  1972年   15342篇
  1967年   13118篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
81.
Telecommunication Systems - Energy saving in User Equipment (UE) is one of the important issues for limited sources of power in the device. It is critical for the UE to maximize its energy...  相似文献   
82.
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   
83.
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically...  相似文献   
84.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is...  相似文献   
85.
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   
86.
Mobile Networks and Applications - Project MindCatcher is an art/research project which has the intention to explore the potential of interactive artistic environments for measuring and a better...  相似文献   
87.
Sohrabi  M. 《Analysis Mathematica》2021,47(2):421-435
Analysis Mathematica - In this paper, we discuss measure theoretic characterizations for Moore-Penrose inverse of Lambert conditional operators, denoted by (MwEMu)?, in some operator classes...  相似文献   
88.
Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI2. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions.  相似文献   
89.
90.
Sun  J.  Yuan  H. 《Experimental Mechanics》2021,61(3):565-580
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients...  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