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   1481763篇
  免费   29983篇
  国内免费   7869篇
化学   758399篇
晶体学   16749篇
力学   78326篇
综合类   121篇
数学   255611篇
物理学   410409篇
  2021年   13600篇
  2020年   16111篇
  2019年   16232篇
  2018年   17848篇
  2017年   16528篇
  2016年   30477篇
  2015年   21535篇
  2014年   30850篇
  2013年   75170篇
  2012年   46486篇
  2011年   50382篇
  2010年   42916篇
  2009年   43939篇
  2008年   47365篇
  2007年   45166篇
  2006年   44863篇
  2005年   40725篇
  2004年   38822篇
  2003年   35031篇
  2002年   34719篇
  2001年   34933篇
  2000年   28867篇
  1999年   24458篇
  1998年   21848篇
  1997年   21654篇
  1996年   21574篇
  1995年   19521篇
  1994年   19021篇
  1993年   18634篇
  1992年   19294篇
  1991年   19432篇
  1990年   18048篇
  1989年   17967篇
  1988年   17687篇
  1987年   17571篇
  1986年   16482篇
  1985年   22948篇
  1984年   24029篇
  1983年   19965篇
  1982年   21531篇
  1981年   20752篇
  1980年   20077篇
  1979年   20698篇
  1978年   21792篇
  1977年   21520篇
  1976年   21333篇
  1975年   20074篇
  1974年   19771篇
  1973年   20225篇
  1972年   14699篇
排序方式: 共有10000条查询结果,搜索用时 38 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