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   1503311篇
  免费   32101篇
  国内免费   8236篇
化学   653050篇
晶体学   19997篇
力学   74032篇
综合类   104篇
数学   238904篇
物理学   362642篇
无线电   194919篇
  2021年   14709篇
  2020年   17336篇
  2019年   17501篇
  2016年   29177篇
  2015年   21585篇
  2014年   32747篇
  2013年   78527篇
  2012年   39119篇
  2011年   34679篇
  2010年   38485篇
  2009年   43594篇
  2008年   38428篇
  2007年   34985篇
  2006年   43366篇
  2005年   34466篇
  2004年   36469篇
  2003年   34495篇
  2002年   35746篇
  2001年   34787篇
  2000年   31142篇
  1999年   28726篇
  1998年   27347篇
  1997年   27227篇
  1996年   26801篇
  1995年   24606篇
  1994年   24065篇
  1993年   23436篇
  1992年   23084篇
  1991年   23300篇
  1990年   22028篇
  1989年   21703篇
  1988年   20834篇
  1987年   19610篇
  1986年   18447篇
  1985年   24950篇
  1984年   26165篇
  1983年   22165篇
  1982年   23607篇
  1981年   22815篇
  1980年   22057篇
  1979年   21876篇
  1978年   23216篇
  1977年   22755篇
  1976年   22349篇
  1975年   21043篇
  1974年   20636篇
  1973年   21199篇
  1972年   15371篇
  1968年   13044篇
  1967年   13148篇
排序方式: 共有10000条查询结果,搜索用时 15 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