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   150629篇
  免费   24465篇
  国内免费   18167篇
化学   105858篇
晶体学   1803篇
力学   8829篇
综合类   1212篇
数学   19340篇
物理学   56219篇
  2024年   334篇
  2023年   2782篇
  2022年   3665篇
  2021年   5027篇
  2020年   5977篇
  2019年   5732篇
  2018年   5157篇
  2017年   4855篇
  2016年   7087篇
  2015年   6996篇
  2014年   8614篇
  2013年   11275篇
  2012年   13439篇
  2011年   14007篇
  2010年   9875篇
  2009年   9517篇
  2008年   10057篇
  2007年   8986篇
  2006年   8424篇
  2005年   7127篇
  2004年   5566篇
  2003年   4488篇
  2002年   4225篇
  2001年   3457篇
  2000年   3058篇
  1999年   3199篇
  1998年   2606篇
  1997年   2381篇
  1996年   2359篇
  1995年   2086篇
  1994年   1867篇
  1993年   1531篇
  1992年   1334篇
  1991年   1157篇
  1990年   974篇
  1989年   749篇
  1988年   563篇
  1987年   503篇
  1986年   491篇
  1985年   401篇
  1984年   272篇
  1983年   237篇
  1982年   177篇
  1981年   122篇
  1980年   90篇
  1979年   43篇
  1976年   41篇
  1975年   46篇
  1973年   37篇
  1957年   39篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture.  相似文献   
102.
103.
A series of tetraimidazolium salts with different anions was prepared and applied in the isomerization of β-pinene oxide. After examining the activity of different catalysts, a remarkable enhancement of the selectivity of perillyl alcohol (47 %) was obtained over [PEimi][HNO3]4 under mild reaction conditions and using DMSO as the solvent. Furthermore, noncovalent interactions between solvent molecules and the catalyst were found by FT-IR spectroscopy and confirmed by computational chemistry. The homogeneous catalyst showed excellent stability and was reused up to six times without significant loss.  相似文献   
104.
Guo  Yan  Li  Zhuang  Wei  Yuxi  Zhang  Xinxu  Shi  Kexin 《Journal of Solid State Electrochemistry》2022,26(4):1051-1065
Journal of Solid State Electrochemistry - Polyvinylpyrrolidone (PVP) and graphene (G)-modified iron oxides (Fe2O3-PVP-G) are prepared by a simple hydrothermal reaction. Their morphology and...  相似文献   
105.
106.
The Ramanujan Journal - Inspired by Andrews and Merca’s recent work on the number of even parts over all partitions into distinct parts, we introduce a new kind of Beck type identities, which...  相似文献   
107.
108.
Let L be an additive map between (real or complex) matrix algebras sending n×n Hermitian idempotent matrices to m×m Hermitian idempotent matrices. We show that there are nonnegative integers p,q with n(p+q)=rm and an m×m unitary matrix U such thatL(A)=U[(Ip?A)(Iq?At)0m?r]U?,for any n×n Hermitian A with rational trace. We also extend this result to the (complex) von Neumann algebra setting, and provide a supplement to the Dye-Bunce-Wright Theorem asserting that every additive map of Hermitian idempotents extends to a Jordan ?-homomorphism.  相似文献   
109.
Journal of Algebraic Combinatorics - By appropriately choosing a defining set, we define a class of linear codes and establish their complete weight enumerators and weight enumerators using Weil...  相似文献   
110.
This work is concerned with the extension of the Jacobi spectral Galerkin method to a class of nonlinear fractional pantograph differential equations. First, the fractional differential equation is converted to a nonlinear Volterra integral equation with weakly singular kernel. Second, we analyze the existence and uniqueness of solutions for the obtained integral equation. Then, the Galerkin method is used for solving the equivalent integral equation. The error estimates for the proposed method are also investigated. Finally, illustrative examples are presented to confirm our theoretical analysis.  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