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   1449690篇
  免费   31992篇
  国内免费   8135篇
化学   618602篇
晶体学   19898篇
力学   73315篇
综合类   101篇
数学   236611篇
物理学   348318篇
无线电   192972篇
  2021年   14660篇
  2020年   17289篇
  2019年   17438篇
  2016年   28750篇
  2015年   21473篇
  2014年   32591篇
  2013年   78292篇
  2012年   36066篇
  2011年   29739篇
  2010年   37198篇
  2009年   42791篇
  2008年   34197篇
  2007年   30347篇
  2006年   39411篇
  2005年   30335篇
  2004年   33002篇
  2003年   31841篇
  2002年   33373篇
  2001年   30964篇
  2000年   28735篇
  1999年   27650篇
  1998年   26934篇
  1997年   26877篇
  1996年   26631篇
  1995年   24490篇
  1994年   23947篇
  1993年   23300篇
  1992年   22576篇
  1991年   22816篇
  1990年   21603篇
  1989年   21295篇
  1988年   20438篇
  1987年   19266篇
  1986年   18039篇
  1985年   24632篇
  1984年   25935篇
  1983年   22001篇
  1982年   23504篇
  1981年   22731篇
  1980年   21978篇
  1979年   21672篇
  1978年   23065篇
  1977年   22580篇
  1976年   22116篇
  1975年   20777篇
  1974年   20380篇
  1973年   20905篇
  1972年   15112篇
  1968年   12836篇
  1967年   12932篇
排序方式: 共有10000条查询结果,搜索用时 890 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