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   1416181篇
  免费   29829篇
  国内免费   7755篇
化学   713987篇
晶体学   16008篇
力学   76956篇
综合类   120篇
数学   250472篇
物理学   396222篇
  2021年   13511篇
  2020年   16015篇
  2019年   16143篇
  2018年   16632篇
  2017年   15317篇
  2016年   29774篇
  2015年   21306篇
  2014年   30625篇
  2013年   74830篇
  2012年   43036篇
  2011年   44432篇
  2010年   41023篇
  2009年   42654篇
  2008年   42432篇
  2007年   39628篇
  2006年   40783篇
  2005年   36128篇
  2004年   35179篇
  2003年   32181篇
  2002年   32288篇
  2001年   31563篇
  2000年   26749篇
  1999年   23454篇
  1998年   21430篇
  1997年   21363篇
  1996年   21343篇
  1995年   19320篇
  1994年   18490篇
  1993年   17794篇
  1992年   17957篇
  1991年   18218篇
  1990年   17396篇
  1989年   17411篇
  1988年   17090篇
  1987年   17026篇
  1986年   15896篇
  1985年   22427篇
  1984年   23686篇
  1983年   19721篇
  1982年   21375篇
  1981年   20588篇
  1980年   19922篇
  1979年   20355篇
  1978年   21598篇
  1977年   21256篇
  1976年   21042篇
  1975年   19752篇
  1974年   19438篇
  1973年   19934篇
  1972年   14417篇
排序方式: 共有10000条查询结果,搜索用时 198 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