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   619680篇
  免费   5936篇
  国内免费   1650篇
化学   319758篇
晶体学   9171篇
力学   29920篇
综合类   22篇
数学   78276篇
物理学   190119篇
  2021年   5384篇
  2020年   5962篇
  2019年   6653篇
  2018年   8863篇
  2017年   8957篇
  2016年   12535篇
  2015年   6902篇
  2014年   11416篇
  2013年   27137篇
  2012年   20800篇
  2011年   24934篇
  2010年   18456篇
  2009年   18146篇
  2008年   23460篇
  2007年   23308篇
  2006年   21443篇
  2005年   19404篇
  2004年   17924篇
  2003年   16157篇
  2002年   16003篇
  2001年   17076篇
  2000年   13255篇
  1999年   10265篇
  1998年   8951篇
  1997年   8826篇
  1996年   8235篇
  1995年   7543篇
  1994年   7417篇
  1993年   7139篇
  1992年   7666篇
  1991年   8131篇
  1990年   7784篇
  1989年   7721篇
  1988年   7586篇
  1987年   7378篇
  1986年   7038篇
  1985年   9059篇
  1984年   9496篇
  1983年   7994篇
  1982年   8495篇
  1981年   7886篇
  1980年   7613篇
  1979年   8078篇
  1978年   8475篇
  1977年   8288篇
  1976年   8252篇
  1975年   7881篇
  1974年   7611篇
  1973年   8092篇
  1972年   5739篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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   
12.
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   
13.
Theoretical and Mathematical Physics - We describe the procedure of dimensional reduction of massless fields in $$(d+1)$$ -dimensional Minkowski space to massive fields in $$d$$ dimensions in the...  相似文献   
14.
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   
15.
Journal of Applied Spectroscopy - The present work aims to focus on the synthesis and spectral studies of the charge-transfer interaction between the nitro organic acceptors molecules [e.g.,...  相似文献   
16.
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   
17.
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the...  相似文献   
18.
19.
In this concept review, the fundamental and polymerization chemistry of inverse vulcanization for the preparation of statistical and segmented sulfur copolymers, which have been actively developed and advanced in various applications over the past decade is discussed. This concept review delves into a discussion of step-growth polymerization constructs to describe the inverse vulcanization process and discuss prepolymer approaches for the synthesis of segmented sulfur polyurethanes. Furthermore, this concept review discusses the advantages of inverse vulcanization in conjunction with dynamic covalent polymerization and post-polymerization modifications to prepare segmented block copolymers with enhanced thermomechanical and flame retardant properties of these materials.  相似文献   
20.
Nodargi  Nicola A.  Bisegna  Paolo 《Meccanica》2022,57(1):121-141
Meccanica - The static limit analysis of axially symmetric masonry domes subject to pseudo-static seismic forces is addressed. The stress state in the dome is represented by the shell stress...  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