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   69624篇
  免费   11987篇
  国内免费   2988篇
化学   63109篇
晶体学   719篇
力学   2145篇
综合类   116篇
数学   5361篇
物理学   13149篇
  2023年   411篇
  2022年   702篇
  2021年   1106篇
  2020年   2053篇
  2019年   3334篇
  2018年   1679篇
  2017年   1291篇
  2016年   4413篇
  2015年   4423篇
  2014年   4602篇
  2013年   6027篇
  2012年   5659篇
  2011年   5024篇
  2010年   4682篇
  2009年   4435篇
  2008年   4565篇
  2007年   3795篇
  2006年   3434篇
  2005年   3436篇
  2004年   2884篇
  2003年   2470篇
  2002年   3092篇
  2001年   2182篇
  2000年   1986篇
  1999年   881篇
  1998年   462篇
  1997年   530篇
  1996年   526篇
  1995年   426篇
  1994年   420篇
  1993年   377篇
  1992年   363篇
  1991年   295篇
  1990年   236篇
  1989年   210篇
  1988年   195篇
  1987年   150篇
  1986年   142篇
  1985年   200篇
  1984年   133篇
  1983年   113篇
  1982年   139篇
  1981年   95篇
  1980年   89篇
  1978年   84篇
  1977年   87篇
  1976年   95篇
  1975年   109篇
  1974年   81篇
  1973年   106篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Radioanalytical and Nuclear Chemistry - Eco-friendly and low-cost composite, amidoxime-functionalized microcrystalline cellulose/mesoporous silica (MCC/MS-AO), were synthesized by...  相似文献   
2.
The artificially accurate design of nonmetal electrocatalysts’ active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom.  相似文献   
3.
Fan  K.  Lu  R. S.  Liang  K. K.  Hou  Z. C. 《High Energy Chemistry》2022,56(4):264-269
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was...  相似文献   
4.
Journal of Algebraic Combinatorics - A dessin is called circular if the boundary of each face is a circuit (a simple cycle). In this paper, we address the problem of characterizing edge-transitive...  相似文献   
5.
Lyu  Pin  Vong  Seakweng 《Numerical Algorithms》2021,87(1):381-408
Numerical Algorithms - In this paper, we study a fast linearized numerical method for solving nonlinear time-fractional diffusion equations. A new weighted method is proposed to construct...  相似文献   
6.
Yu  Yangyang  Li  Jiajia  Yuan  Zhixuan  Fan  Yongchen  Wu  Ying 《Nonlinear dynamics》2022,109(4):3113-3132
Nonlinear Dynamics - Epilepsy is the second largest neurological disease which seriously threatens human life and health. The one important reason of inducing epileptic seizures is ischemic stroke...  相似文献   
7.
8.
The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g?1 for the CNOs/Ppy bilayer (electrochemical deposition).  相似文献   
9.
A two‐step synthesis of structurally diverse pyrrole‐containing bicyclic systems is reported. ortho‐Nitro‐haloarenes coupled with vinylic N‐methyliminodiacetic acid (MIDA) boronates generate ortho‐vinyl‐nitroarenes, which undergo a “metal‐free” nitrene insertion, resulting in a new pyrrole ring. This novel synthetic approach has a wide substrate tolerance and it is applicable in the preparation of more complex “drug‐like” molecules. Interestingly, an ortho‐nitro‐allylarene derivative furnished a cyclic β‐aminophosphonate motif.  相似文献   
10.
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