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   1546081篇
  免费   32227篇
  国内免费   8206篇
化学   681133篇
晶体学   20080篇
力学   74688篇
综合类   104篇
数学   242431篇
物理学   371763篇
无线电   196315篇
  2021年   14746篇
  2020年   17381篇
  2019年   17528篇
  2016年   29468篇
  2015年   21790篇
  2014年   32886篇
  2013年   78885篇
  2012年   41556篇
  2011年   38436篇
  2010年   39588篇
  2009年   44258篇
  2008年   41620篇
  2007年   38553篇
  2006年   46521篇
  2005年   37506篇
  2004年   39071篇
  2003年   36615篇
  2002年   37784篇
  2001年   37207篇
  2000年   32701篇
  1999年   29520篇
  1998年   27743篇
  1997年   27542篇
  1996年   27018篇
  1995年   24784篇
  1994年   24251篇
  1993年   23639篇
  1992年   23568篇
  1991年   23697篇
  1990年   22442篇
  1989年   22034篇
  1988年   21227篇
  1987年   19873篇
  1986年   18780篇
  1985年   25282篇
  1984年   26403篇
  1983年   22340篇
  1982年   23784篇
  1981年   22938篇
  1980年   22180篇
  1979年   22116篇
  1978年   23366篇
  1977年   22929篇
  1976年   22569篇
  1975年   21274篇
  1974年   20949篇
  1973年   21458篇
  1972年   15612篇
  1968年   13295篇
  1967年   13345篇
排序方式: 共有10000条查询结果,搜索用时 906 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