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   220952篇
  免费   5062篇
  国内免费   2665篇
化学   114874篇
晶体学   3521篇
力学   10299篇
综合类   108篇
数学   24275篇
物理学   75602篇
  2022年   1764篇
  2021年   2297篇
  2020年   2526篇
  2019年   2704篇
  2018年   3322篇
  2017年   3162篇
  2016年   4606篇
  2015年   3115篇
  2014年   4598篇
  2013年   10341篇
  2012年   8782篇
  2011年   10203篇
  2010年   7066篇
  2009年   6874篇
  2008年   8966篇
  2007年   9070篇
  2006年   8624篇
  2005年   7714篇
  2004年   7014篇
  2003年   6153篇
  2002年   5978篇
  2001年   6795篇
  2000年   5277篇
  1999年   4211篇
  1998年   3376篇
  1997年   3377篇
  1996年   3104篇
  1995年   2888篇
  1994年   2683篇
  1993年   2535篇
  1992年   2844篇
  1991年   2802篇
  1990年   2755篇
  1989年   2502篇
  1988年   2522篇
  1987年   2501篇
  1986年   2337篇
  1985年   3015篇
  1984年   3243篇
  1983年   2659篇
  1982年   2825篇
  1981年   2788篇
  1980年   2646篇
  1979年   2729篇
  1978年   2821篇
  1977年   2822篇
  1976年   2886篇
  1975年   2670篇
  1974年   2644篇
  1973年   2777篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
Siberian Mathematical Journal - Suppose that $ n $ is an integer, $ n\geq 3 $ . We prove that a periodic group saturated with a set of the finite simple groups $ O_{2n+1}(q) $ , where $ q $ is...  相似文献   
12.
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation.  相似文献   
13.
Kobayashi  M.  Zhang  Y.  Ishikawa  H.  Sun  J.  Oddershede  J.  Juul Jensen  D.  Miura  H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such...  相似文献   
14.
Russian Physics Journal - The specific features of the sorption activity of silver nanoparticles (AgNPs) on biodegradable polymers of natural (collagen) and artificial (polyamide 6.6) origin have...  相似文献   
15.
16.
Doklady Physics - This work is devoted to analysis and generalization of the kinetic criteria of vitrification using the model of delocalized atoms. The generalized criterion of a...  相似文献   
17.
Ferrarini  A.  Finotello  A.  Salsano  G.  Auricchio  F.  Palombo  D.  Spinella  G.  Pane  B.  Conti  M. 《Acta Mechanica Sinica》2021,37(7):1192-1192
Acta Mechanica Sinica - A Correction to this paper has been published: https://doi.org/10.1007/s10409-021-01066-2  相似文献   
18.
Journal of Experimental and Theoretical Physics - The studies of the topological properties of systems have recently been extended due to a new concept of higher-order topological insulators and...  相似文献   
19.
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   
20.
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