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   1439385篇
  免费   29926篇
  国内免费   7786篇
化学   736803篇
晶体学   19588篇
力学   76710篇
综合类   109篇
数学   249502篇
物理学   394385篇
  2021年   13580篇
  2020年   16054篇
  2019年   16199篇
  2018年   14632篇
  2016年   29098篇
  2015年   21219篇
  2014年   30789篇
  2013年   75034篇
  2012年   44020篇
  2011年   45101篇
  2010年   40132篇
  2009年   41492篇
  2008年   42631篇
  2007年   39344篇
  2006年   43262篇
  2005年   36252篇
  2004年   36146篇
  2003年   33124篇
  2002年   33565篇
  2001年   34137篇
  2000年   28271篇
  1999年   24223篇
  1998年   21746篇
  1997年   21576篇
  1996年   21459篇
  1995年   19456篇
  1994年   18935篇
  1993年   18512篇
  1992年   19170篇
  1991年   19313篇
  1990年   18515篇
  1989年   18496篇
  1988年   18139篇
  1987年   17958篇
  1986年   16989篇
  1985年   23325篇
  1984年   24286篇
  1983年   20340篇
  1982年   21945篇
  1981年   21127篇
  1980年   20458篇
  1979年   20915篇
  1978年   22034篇
  1977年   21418篇
  1976年   21211篇
  1975年   19974篇
  1974年   19652篇
  1973年   20116篇
  1972年   14604篇
  1967年   12951篇
排序方式: 共有10000条查询结果,搜索用时 328 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