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   106230篇
  免费   18426篇
  国内免费   10834篇
化学   72422篇
晶体学   1270篇
力学   7042篇
综合类   620篇
数学   12520篇
物理学   41616篇
  2024年   110篇
  2023年   2170篇
  2022年   2329篇
  2021年   3508篇
  2020年   4461篇
  2019年   4303篇
  2018年   3623篇
  2017年   3396篇
  2016年   5290篇
  2015年   4999篇
  2014年   6140篇
  2013年   7987篇
  2012年   9678篇
  2011年   10186篇
  2010年   6782篇
  2009年   6482篇
  2008年   6880篇
  2007年   6303篇
  2006年   5767篇
  2005年   4804篇
  2004年   3584篇
  2003年   2779篇
  2002年   2449篇
  2001年   2034篇
  2000年   1760篇
  1999年   2039篇
  1998年   1836篇
  1997年   1687篇
  1996年   1833篇
  1995年   1506篇
  1994年   1474篇
  1993年   1165篇
  1992年   1067篇
  1991年   999篇
  1990年   797篇
  1989年   567篇
  1988年   464篇
  1987年   381篇
  1986年   373篇
  1985年   324篇
  1984年   243篇
  1983年   156篇
  1982年   141篇
  1981年   108篇
  1980年   77篇
  1979年   44篇
  1978年   35篇
  1976年   37篇
  1975年   34篇
  1974年   49篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Xu  Yifan  Zhang  Hehe  Ding  Tangjing  Tian  Ruiqi  Sun  Dongmei  Wang  Ming-Sheng  Zhou  Xiaosi 《中国科学:化学(英文版)》2022,65(9):1807-1816
Science China Chemistry - Due to their enormous potential for large-scale energy storage, rechargeable potassium-ion batteries have been widely researched and developed. However, the drastic volume...  相似文献   
102.
The N–N bond is present in many important organic compounds, such as hydrazines, pyrazoles, azos, etc. Many methods based on transition metal catalyzed N–N coupling or functionalization of hydrazine have been reported for the synthesis of N–N containing organic compounds. In recent years, electrochemical dehydrogenative N–H/N–H coupling has become a powerful tool for the construction of N–N bearing organic compounds. The electrochemical methods employ electrons as traceless redox reagents instead of chemicals and produce hydrogen as the only byproduct. In this review, we summarize the recent advances in the electrochemical dehydrogenative N–H/N–H coupling reactions with focus on the mechanistic insights and synthetic applications of these transformations.  相似文献   
103.
Li  Zh.  Zhang  Y.  Wang  R.  Jiang  D. 《Journal of Applied Spectroscopy》2022,89(2):371-380
Journal of Applied Spectroscopy - The concentration of heavy metals in drinking water is an important standard for water quality evaluation and water pipeline corrosion detection. This research...  相似文献   
104.
Acta Mathematica Sinica, English Series - We are interested in the existence and asymptotic behavior for the least energy solutions of the following fractional eigenvalue problem $$\left({\rm{P}}...  相似文献   
105.
Chen  Renhong  Mei  Jie  Xu  Jin  Xu  Wanjie  Wang  Laisen  Chen  Yuanzhi  Peng  Dong-Liang 《Journal of Solid State Electrochemistry》2022,26(6):1359-1368
Journal of Solid State Electrochemistry - High-voltage LiNi0.5Mn1.5O4 with a spinel structure is considered as important cathode materials for high-energy density Li-ion batteries (LIBs). In this...  相似文献   
106.
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   
107.
Science China Mathematics - This paper studies exact synchronization and asymptotic synchronization problems for a controlled linear system of ordinary differential equations. In this paper, we...  相似文献   
108.
Journal of Optimization Theory and Applications - This paper considers an optimal control problem governed by nonlinear fractional-order systems with multiple time-varying delays and subject to...  相似文献   
109.
Journal of Radioanalytical and Nuclear Chemistry - In the present work the final products of coumarin radiation chemical transformation are investigated by chromatography. During radiolysis of...  相似文献   
110.
Abstract

Complexes of [CdL2(NO3)2]·1.5H2O and [Ag2(μ-L)2(NO3)2] were synthesized by the reactions of 2-p-methylphenyl-5-(2-pyridyl)-1,3,4-thiadiazole (L) with Cd(NO3)2·4H2O and AgNO3, respectively. Their structures were determined by single crystal X-ray diffraction. The photophysical property and thermal stability were characterized by FT???IR, UV???Vis absorption, fluorescence, and thermogravimetric analysis (TGA). Both complexes belong to the triclinic system with space group p???1. The central metal of [CdL2(NO3)2]·1.5H2O has a distorted octahedral geometry [CdN4O2], while two central Ag(I) atoms of [Ag2(μ-L)2(NO3)2] exhibit distorted tetrahedral geometries [AgN3O].  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