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   1560699篇
  免费   33125篇
  国内免费   9109篇
化学   686907篇
晶体学   20553篇
力学   75259篇
综合类   163篇
数学   243480篇
物理学   377904篇
无线电   198667篇
  2021年   14833篇
  2020年   17466篇
  2019年   17581篇
  2018年   14852篇
  2016年   30322篇
  2015年   22142篇
  2014年   32968篇
  2013年   78989篇
  2012年   42187篇
  2011年   40528篇
  2010年   41580篇
  2009年   46168篇
  2008年   43487篇
  2007年   41123篇
  2006年   46177篇
  2005年   39411篇
  2004年   39484篇
  2003年   36840篇
  2002年   37485篇
  2001年   36217篇
  2000年   32244篇
  1999年   29272篇
  1998年   27553篇
  1997年   27387篇
  1996年   26968篇
  1995年   24725篇
  1994年   24213篇
  1993年   23603篇
  1992年   23356篇
  1991年   23543篇
  1990年   22351篇
  1989年   21902篇
  1988年   21109篇
  1987年   19861篇
  1986年   18728篇
  1985年   25240篇
  1984年   26389篇
  1983年   22289篇
  1982年   23708篇
  1981年   22868篇
  1980年   22167篇
  1979年   22056篇
  1978年   23310篇
  1977年   22878篇
  1976年   22527篇
  1975年   21231篇
  1974年   20831篇
  1973年   21380篇
  1972年   15568篇
  1967年   13322篇
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
151.
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   
152.
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   
153.
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   
154.
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   
155.
Siberian Mathematical Journal - We give a simple proof of one assertion used in solving Waring’s problem.  相似文献   
156.
157.
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   
158.
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   
159.
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   
160.
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   
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