首页 | 官方网站   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   1362423篇
  免费   29743篇
  国内免费   7661篇
数理化   1399827篇
  2021年   13437篇
  2020年   15938篇
  2019年   16068篇
  2018年   15146篇
  2017年   13780篇
  2016年   28968篇
  2015年   21050篇
  2014年   30490篇
  2013年   74474篇
  2012年   39716篇
  2011年   38842篇
  2010年   39137篇
  2009年   41268篇
  2008年   37386篇
  2007年   33905篇
  2006年   36801篇
  2005年   31116篇
  2004年   31490篇
  2003年   29218篇
  2002年   29812篇
  2001年   29879篇
  2000年   25473篇
  1999年   22841篇
  1998年   21181篇
  1997年   21160篇
  1996年   21159篇
  1995年   19216篇
  1994年   18667篇
  1993年   18200篇
  1992年   18351篇
  1991年   17996篇
  1990年   17203篇
  1989年   17238篇
  1988年   16864篇
  1987年   16876篇
  1986年   15791篇
  1985年   22289篇
  1984年   23544篇
  1983年   19625篇
  1982年   21291篇
  1981年   20513篇
  1980年   19826篇
  1979年   20203篇
  1978年   21457篇
  1977年   21129篇
  1976年   20870篇
  1975年   19525篇
  1974年   19169篇
  1973年   19702篇
  1972年   14179篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
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   
132.
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   
133.
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   
134.
Siberian Mathematical Journal - We give a simple proof of one assertion used in solving Waring’s problem.  相似文献   
135.
136.
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   
137.
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   
138.
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   
139.
CRANAD-2 is a fluorogenic curcumin derivative used for near-infrared detection and imaging in vivo of amyloid aggregates, which are involved in neurodegenerative diseases. We explore the performance of CRANAD-2 in two super-resolution imaging techniques, namely stimulated emission depletion (STED) and single-molecule localization microscopy (SMLM), with markedly different fluorophore requirements. By conveniently adapting the concentration of CRANAD-2, which transiently binds to amyloid fibrils, we show that it performs well in both techniques, achieving a resolution in the range of 45–55 nm. Correlation of SMLM with atomic force microscopy (AFM) validates the resolution of fine features in the reconstructed super-resolved image. The good performance and versatility of CRANAD-2 provides a powerful tool for near-infrared nanoscopic imaging of amyloids in vitro and in vivo.  相似文献   
140.
Designs, Codes and Cryptography - Given an integer $$k\ge 3$$ and a group G of odd order,  if there exists a 2-(v, k, 1)-design and if v is sufficiently large then there...  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-23

京公网安备 11010802026262号