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   1543368篇
  免费   32317篇
  国内免费   8293篇
化学   679151篇
晶体学   20110篇
力学   74729篇
综合类   105篇
数学   241125篇
物理学   372130篇
无线电   196628篇
  2021年   14769篇
  2020年   17379篇
  2019年   17545篇
  2016年   29558篇
  2015年   21741篇
  2014年   32872篇
  2013年   78810篇
  2012年   40961篇
  2011年   37716篇
  2010年   39401篇
  2009年   44202篇
  2008年   40981篇
  2007年   38055篇
  2006年   45672篇
  2005年   36957篇
  2004年   38538篇
  2003年   36169篇
  2002年   37247篇
  2001年   37477篇
  2000年   32852篇
  1999年   29515篇
  1998年   27692篇
  1997年   27507篇
  1996年   26961篇
  1995年   24730篇
  1994年   24212篇
  1993年   23594篇
  1992年   23690篇
  1991年   23798篇
  1990年   22578篇
  1989年   22190篇
  1988年   21342篇
  1987年   20078篇
  1986年   18933篇
  1985年   25408篇
  1984年   26476篇
  1983年   22370篇
  1982年   23743篇
  1981年   22939篇
  1980年   22174篇
  1979年   22210篇
  1978年   23397篇
  1977年   23028篇
  1976年   22630篇
  1975年   21354篇
  1974年   20945篇
  1973年   21501篇
  1972年   15653篇
  1968年   13362篇
  1967年   13446篇
排序方式: 共有10000条查询结果,搜索用时 125 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