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   1551365篇
  免费   32292篇
  国内免费   8317篇
化学   683064篇
晶体学   20255篇
力学   74761篇
综合类   111篇
数学   241810篇
物理学   374693篇
无线电   197280篇
  2021年   14789篇
  2020年   17429篇
  2019年   17594篇
  2018年   13366篇
  2016年   29878篇
  2015年   21838篇
  2014年   32972篇
  2013年   78827篇
  2012年   41465篇
  2011年   38754篇
  2010年   40058篇
  2009年   44818篇
  2008年   41820篇
  2007年   38803篇
  2006年   45790篇
  2005年   37516篇
  2004年   38779篇
  2003年   36364篇
  2002年   37250篇
  2001年   37507篇
  2000年   32859篇
  1999年   29496篇
  1998年   27638篇
  1997年   27471篇
  1996年   26992篇
  1995年   24766篇
  1994年   24273篇
  1993年   23626篇
  1992年   23734篇
  1991年   23884篇
  1990年   22672篇
  1989年   22247篇
  1988年   21429篇
  1987年   20148篇
  1986年   19001篇
  1985年   25430篇
  1984年   26553篇
  1983年   22424篇
  1982年   23775篇
  1981年   22965篇
  1980年   22204篇
  1979年   22224篇
  1978年   23439篇
  1977年   23072篇
  1976年   22635篇
  1975年   21333篇
  1974年   20905篇
  1973年   21421篇
  1972年   15589篇
  1967年   13386篇
排序方式: 共有10000条查询结果,搜索用时 140 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