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   1357556篇
  免费   29963篇
  国内免费   7781篇
化学   684082篇
晶体学   20119篇
力学   74803篇
综合类   111篇
数学   243569篇
物理学   372616篇
  2021年   13531篇
  2020年   16027篇
  2019年   16178篇
  2016年   27812篇
  2015年   20931篇
  2014年   30718篇
  2013年   75020篇
  2012年   39577篇
  2011年   36530篇
  2010年   37019篇
  2009年   39124篇
  2008年   35570篇
  2007年   31043篇
  2006年   38480篇
  2005年   29742篇
  2004年   31250篇
  2003年   29397篇
  2002年   30651篇
  2001年   30164篇
  2000年   25876篇
  1999年   23097篇
  1998年   21331篇
  1997年   21256篇
  1996年   21245篇
  1995年   19284篇
  1994年   18706篇
  1993年   18273篇
  1992年   18409篇
  1991年   18644篇
  1990年   17847篇
  1989年   17854篇
  1988年   17454篇
  1987年   17335篇
  1986年   16340篇
  1985年   22738篇
  1984年   23916篇
  1983年   20067篇
  1982年   21765篇
  1981年   20968篇
  1980年   20287篇
  1979年   20518篇
  1978年   21809篇
  1977年   21409篇
  1976年   21152篇
  1975年   19879篇
  1974年   19579篇
  1973年   20050篇
  1972年   14516篇
  1968年   12347篇
  1967年   12677篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown...  相似文献   
132.
Doklady Mathematics - Two classes of Taylor-type formulas for arbitrary continuous functions on intervals are obtained using Bernstein polynomials. These formulas are applicable to both smooth...  相似文献   
133.
Journal of Solid State Electrochemistry - The electrochemical deposition of a nickel–iron alloy from a plating solution based on a deep eutectic solvent (a eutectic mixture of ethylene glycol...  相似文献   
134.
By linking the carbazole unit to the nitrogen atom of acridone through phenyl or pyridyl, two compounds, named 10-(4-(9H-carbazol-9-yl)phenyl)acridin-9(10H)-one (AC-Ph-Cz) and 10-(5-(9H-carbazol-9-yl)pyridin-2-yl)acridin-9(10H)-one (AC-Py-Cz) were designed and synthesized. These two materials, characterized with highly twisted and rigid structure, good thermal stability, and balanced carrier-transporting properties, were employed as host materials for green phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes (OLEDs). The carbazole group, despite its small contribution to the highest occupied molecular orbitals (HOMOs) of these two materials, plays an essential role as an intramolecular host in energy delivering and improving the hole transporting ability of these two hosts. The incorporation of the electron-deficient pyridyl group as a linking group slightly improves the electron transporting capability of AC-Py-Cz. The green phosphorescent OLED (PhOLED) based on AC-Py-Cz exhibited excellent device performance with a turn-on voltage of 2.5 V, a maximum power efficiency and an external quantum efficiency (ηext) of 89.8 lm W−1 and 25.2 %, respectively, benefitting from the better charge-balancing ability of AC-Py-Cz host due to the presence of the pyridyl bridge. More importantly, all the devices based on these two hosts showed low efficiency roll-off at high brightness due to the suppressed non-radiative transition in the emitting layer. In particular, the AC-Py-Cz-hosted green PhOLED exhibited an efficiency roll-off of 1.6 % from the maximum next at a high brightness of 1000 cd m−2 and a roll-off of 15.9 % at an extremely high brightness of 10000 cd m−2. This study manifests that acridone-based host materials have great potential in fabricating OLEDs with low efficiency roll-off.  相似文献   
135.
Physics of the Solid State - Local internal stresses in two natural inhomogeneous materials differing in the structure have been calculated using analysis of pauses between acoustic emission...  相似文献   
136.
Siberian Mathematical Journal - We give a simple proof of one assertion used in solving Waring’s problem.  相似文献   
137.
138.
Statistical Inference for Stochastic Processes - The problem of linear interpolation in the context of a multivariate time series having multiple (possibly non-consecutive) missing values is...  相似文献   
139.
Siberian Mathematical Journal - A lattice homomorphism between quasi-Banach lattices is known to be compact if and only if it is a sum of a series of rank one lattice...  相似文献   
140.
Theoretical and Mathematical Physics - This paper is devoted to tetrahedron maps, which are set-theoretical solutions of the Zamolodchikov tetrahedron equation. We construct a family of tetrahedron...  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