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   1583830篇
  免费   32221篇
  国内免费   8276篇
化学   694975篇
晶体学   20905篇
力学   76162篇
综合类   113篇
数学   246202篇
物理学   386825篇
无线电   199145篇
  2021年   14803篇
  2020年   17398篇
  2019年   17527篇
  2018年   17132篇
  2017年   15631篇
  2016年   31250篇
  2015年   22128篇
  2014年   32785篇
  2013年   78601篇
  2012年   43248篇
  2011年   43484篇
  2010年   42807篇
  2009年   47251篇
  2008年   45775篇
  2007年   44040篇
  2006年   46392篇
  2005年   41286篇
  2004年   40956篇
  2003年   37830篇
  2002年   37961篇
  2001年   36763篇
  2000年   32285篇
  1999年   29315篇
  1998年   27585篇
  1997年   27384篇
  1996年   26959篇
  1995年   24689篇
  1994年   24192篇
  1993年   23563篇
  1992年   23375篇
  1991年   23539篇
  1990年   22366篇
  1989年   22015篇
  1988年   21245篇
  1987年   19925篇
  1986年   18724篇
  1985年   25236篇
  1984年   26396篇
  1983年   22329篇
  1982年   23679篇
  1981年   22877篇
  1980年   22120篇
  1979年   22065篇
  1978年   23326篇
  1977年   22894篇
  1976年   22477篇
  1975年   21172篇
  1974年   20802篇
  1973年   21320篇
  1972年   15496篇
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
151.
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   
152.
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   
153.
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   
154.
Siberian Mathematical Journal - We give a simple proof of one assertion used in solving Waring’s problem.  相似文献   
155.
156.
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   
157.
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   
158.
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   
159.
Wireless Personal Communications - Multiple inputs multiple outputs (MIMO) is a reliable technique which can manage the increased wireless data traffic in the future generation of wireless...  相似文献   
160.
Wireless Personal Communications - This paper summarizes the ongoing research initiatives based on the advanced multiple access techniques towards the fifth generation (5G) wireless communication...  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