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   191329篇
  免费   2532篇
  国内免费   807篇
化学   102674篇
晶体学   2590篇
力学   8337篇
综合类   14篇
数学   19865篇
物理学   61188篇
  2021年   1122篇
  2020年   1280篇
  2019年   1316篇
  2018年   1340篇
  2017年   1382篇
  2016年   2653篇
  2015年   2138篇
  2014年   2828篇
  2013年   8710篇
  2012年   6961篇
  2011年   8709篇
  2010年   5403篇
  2009年   5569篇
  2008年   7933篇
  2007年   7991篇
  2006年   7654篇
  2005年   7105篇
  2004年   6350篇
  2003年   5506篇
  2002年   5407篇
  2001年   6622篇
  2000年   4998篇
  1999年   3868篇
  1998年   2963篇
  1997年   2918篇
  1996年   2861篇
  1995年   2648篇
  1994年   2527篇
  1993年   2378篇
  1992年   2698篇
  1991年   2691篇
  1990年   2377篇
  1989年   2295篇
  1988年   2316篇
  1987年   2231篇
  1986年   2120篇
  1985年   3156篇
  1984年   3154篇
  1983年   2484篇
  1982年   2683篇
  1981年   2586篇
  1980年   2519篇
  1979年   2490篇
  1978年   2581篇
  1977年   2514篇
  1976年   2463篇
  1975年   2398篇
  1974年   2309篇
  1973年   2403篇
  1972年   1365篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Yang  T. L.  Kao  C. L.  Kuo  C. E.  Yeh  H. C.  Li  W. J.  Li  H. T.  Chen  C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the...  相似文献   
2.
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   
3.
In the pursuit to enlarge the library of polyimide materials for energy applications, new polyimide/MWCNTs composite films have been developed by MWCNTs-assisted polycondensation reaction of a hydroxyl and triphenylmethane-containing diamine with benzophenone tetracarboxylic dianhydride targeting to highlight their electrical storage capability as flexible electrodes in micro-supercapacitors (mSCs). The Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, UV–vis, fluorescence, and Raman spectroscopies were used to demonstrate the evolution of interfacial interactions between MWCNTs and the precursors (diamine monomer and intermediate polyamidic acid) and polyimide matrix that proved to be the origin of MWCNTs homogeneous dispersion. Thus, composite films incorporating 1, 3, 5, and 10 w.t.% MWCNTs were obtained and thoroughly investigated with regard to their morphology, mechanical behavior, thermal stability, and electrical conductivity. The electrochemical performance of these composites was first analyzed in a classical three-electrode cell by cyclic voltammetry and galvanostatic charge-discharge in both aqueous and organic electrolyte systems. By far, the best electrical storage capacity was obtained with the composite polyimide film containing 10% MWCNTs that was further used as both active material and current collector in a flexible symmetric mSC realized by a straightforward and low-cost procedure. In the attempt to better exploit the advantages of this composite film, it was layered with a graphite-containing paint and tested as an electrode in a flexible mSC, which provided satisfactory results. To our knowledge, this is the first report on the electrical charge storage capability of a polyimide/MWCNTs free-standing film as a flexible electrode in mSCs, which do not require time- and resource-consuming processing steps.  相似文献   
4.
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial...  相似文献   
5.
6.
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   
7.
8.
9.
Journal of Optimization Theory and Applications - A framework for monitoring a target modeled as Dubins car using multiple UAVs is proposed. The UAVs are subject to minimum and maximum speed,...  相似文献   
10.
Kumar  Sanjay  Jiwari  Ram  Mittal  R. C.  Awrejcewicz  Jan 《Nonlinear dynamics》2021,104(1):661-682
Nonlinear Dynamics - In this article, the authors simulate and study dark and bright soliton solutions of 1D and 2D regularized long wave (RLW) models. The RLW model occurred in various fields such...  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