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   536610篇
  免费   5568篇
  国内免费   2107篇
化学   275498篇
晶体学   7751篇
力学   26250篇
综合类   83篇
数学   69359篇
物理学   165344篇
  2021年   5292篇
  2020年   5783篇
  2019年   6493篇
  2018年   8652篇
  2017年   8792篇
  2016年   12050篇
  2015年   6582篇
  2014年   10905篇
  2013年   24128篇
  2012年   19166篇
  2011年   22692篇
  2010年   17072篇
  2009年   16830篇
  2008年   21331篇
  2007年   21172篇
  2006年   19218篇
  2005年   17113篇
  2004年   15906篇
  2003年   14234篇
  2002年   14073篇
  2001年   14854篇
  2000年   11441篇
  1999年   8860篇
  1998年   7660篇
  1997年   7529篇
  1996年   6984篇
  1995年   6303篇
  1994年   6303篇
  1993年   6054篇
  1992年   6411篇
  1991年   6889篇
  1990年   6609篇
  1989年   6504篇
  1988年   6339篇
  1987年   6156篇
  1986年   5885篇
  1985年   7434篇
  1984年   7790篇
  1983年   6545篇
  1982年   6826篇
  1981年   6333篇
  1980年   6016篇
  1979年   6513篇
  1978年   6751篇
  1977年   6634篇
  1976年   6590篇
  1975年   6308篇
  1974年   6134篇
  1973年   6427篇
  1972年   4707篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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   
12.
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   
13.
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   
14.
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   
15.
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   
16.
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   
17.
18.
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   
19.
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