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   652319篇
  免费   7041篇
  国内免费   1540篇
化学   332721篇
晶体学   9509篇
力学   32186篇
综合类   16篇
数学   86799篇
物理学   199669篇
  2021年   6242篇
  2020年   6677篇
  2019年   7538篇
  2018年   10186篇
  2017年   10089篇
  2016年   14461篇
  2015年   8317篇
  2014年   13553篇
  2013年   29269篇
  2012年   23223篇
  2011年   27920篇
  2010年   20815篇
  2009年   20837篇
  2008年   26213篇
  2007年   25767篇
  2006年   23649篇
  2005年   20908篇
  2004年   19573篇
  2003年   17474篇
  2002年   17644篇
  2001年   18678篇
  2000年   14450篇
  1999年   11152篇
  1998年   9665篇
  1997年   9304篇
  1996年   8830篇
  1995年   7948篇
  1994年   7906篇
  1993年   7683篇
  1992年   8245篇
  1991年   8632篇
  1990年   8332篇
  1989年   8190篇
  1988年   7974篇
  1987年   7914篇
  1986年   7436篇
  1985年   9355篇
  1984年   9604篇
  1983年   7804篇
  1982年   8067篇
  1981年   7772篇
  1980年   7270篇
  1979年   7966篇
  1978年   8180篇
  1977年   8167篇
  1976年   8153篇
  1975年   7530篇
  1974年   7374篇
  1973年   7491篇
  1972年   5724篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Kinetics and Catalysis - The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using...  相似文献   
2.
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the...  相似文献   
3.
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a...  相似文献   
4.
5.
Chemistry of Natural Compounds - O- and N-propylamino-derivatives of betulin and betulonic acid oxime and methyl ester were synthesized. Their antitumor activity against a panel of 60 human cancer...  相似文献   
6.
7.
Journal of Structural Chemistry - The structures of Ni(II), Cu(II), and Zn(II) complexes with anions of 2,5-pyrrolyl-disubstituted nitronyl nitroxide (L1) and iminonitroxide (L2) diradicals (HL1 is...  相似文献   
8.
Kinetics and Catalysis - The results of studies in the field of synthesis and characterization of layered double hydroxides (LDHs) obtained using solid-phase reactions are summarized. The effect of...  相似文献   
9.
Mechanics of Composite Materials - Carbon fiber (CF)/ polyamide (PA6) composites are one of the most promising thermoplastic materials for automobile applications. However, the interfacial...  相似文献   
10.
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   
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