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   1484749篇
  免费   33324篇
  国内免费   8999篇
化学   638765篇
晶体学   20035篇
力学   74017篇
综合类   159篇
数学   238549篇
物理学   357462篇
无线电   198085篇
  2021年   15052篇
  2020年   17659篇
  2019年   17859篇
  2016年   29335篇
  2015年   22007篇
  2014年   33212篇
  2013年   79208篇
  2012年   37981篇
  2011年   32511篇
  2010年   38476篇
  2009年   43884篇
  2008年   36451篇
  2007年   32621篇
  2006年   41280篇
  2005年   32189篇
  2004年   34596篇
  2003年   33183篇
  2002年   34536篇
  2001年   33566篇
  2000年   30337篇
  1999年   28491篇
  1998年   27388篇
  1997年   27295篇
  1996年   26899篇
  1995年   24679篇
  1994年   24144篇
  1993年   23466篇
  1992年   23059篇
  1991年   23255篇
  1990年   22080篇
  1989年   21667篇
  1988年   20861篇
  1987年   19662篇
  1986年   18411篇
  1985年   24955篇
  1984年   26187篇
  1983年   22166篇
  1982年   23589篇
  1981年   22782篇
  1980年   22024篇
  1979年   21881篇
  1978年   23176篇
  1977年   22733篇
  1976年   22242篇
  1975年   20900篇
  1974年   20516篇
  1973年   20980篇
  1972年   15202篇
  1968年   12942篇
  1967年   13053篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
81.
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   
82.
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   
83.
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   
84.
85.
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   
86.
Journal of Optimization Theory and Applications - Direct optimization of many-revolution spacecraft trajectories is performed using an unconstrained formulation with many short-arc, embedded...  相似文献   
87.
Russian Physics Journal - The temperature dependences of the linear dielectric permittivity ε′ and the third harmonic coefficient γ3ω for nanocomposites obtained by embedding a...  相似文献   
88.
89.
90.
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