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   1572675篇
  免费   32291篇
  国内免费   8308篇
化学   694371篇
晶体学   20475篇
力学   75669篇
综合类   106篇
数学   244275篇
物理学   380423篇
无线电   197955篇
  2021年   14816篇
  2020年   17438篇
  2019年   17580篇
  2018年   15152篇
  2016年   30540篇
  2015年   22002篇
  2014年   32920篇
  2013年   78856篇
  2012年   42629篇
  2011年   41678篇
  2010年   41470篇
  2009年   45898篇
  2008年   44056篇
  2007年   41626篇
  2006年   46604篇
  2005年   39487篇
  2004年   40054篇
  2003年   37249篇
  2002年   37838篇
  2001年   37835篇
  2000年   32964篇
  1999年   29625篇
  1998年   27705篇
  1997年   27477篇
  1996年   27014篇
  1995年   24776篇
  1994年   24265篇
  1993年   23677篇
  1992年   23722篇
  1991年   23846篇
  1990年   22646篇
  1989年   22262篇
  1988年   21460篇
  1987年   20163篇
  1986年   18997篇
  1985年   25467篇
  1984年   26503篇
  1983年   22375篇
  1982年   23747篇
  1981年   22943篇
  1980年   22185篇
  1979年   22205篇
  1978年   23375篇
  1977年   22953篇
  1976年   22558篇
  1975年   21241篇
  1974年   20872篇
  1973年   21326篇
  1972年   15529篇
  1967年   13327篇
排序方式: 共有10000条查询结果,搜索用时 0 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