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   691282篇
  免费   6610篇
  国内免费   1780篇
化学   354528篇
晶体学   9979篇
力学   34112篇
综合类   26篇
数学   91066篇
物理学   209961篇
  2021年   5829篇
  2020年   6531篇
  2019年   7336篇
  2018年   9785篇
  2017年   9919篇
  2016年   13971篇
  2015年   7778篇
  2014年   12796篇
  2013年   30352篇
  2012年   23234篇
  2011年   27675篇
  2010年   20393篇
  2009年   20127篇
  2008年   26094篇
  2007年   26085篇
  2006年   24019篇
  2005年   21424篇
  2004年   19809篇
  2003年   17908篇
  2002年   17800篇
  2001年   18854篇
  2000年   14749篇
  1999年   11464篇
  1998年   9916篇
  1997年   9866篇
  1996年   9271篇
  1995年   8384篇
  1994年   8541篇
  1993年   8117篇
  1992年   8704篇
  1991年   9116篇
  1990年   8776篇
  1989年   8533篇
  1988年   8435篇
  1987年   8300篇
  1986年   7886篇
  1985年   10249篇
  1984年   10763篇
  1983年   9055篇
  1982年   9400篇
  1981年   8946篇
  1980年   8624篇
  1979年   9023篇
  1978年   9503篇
  1977年   9365篇
  1976年   9379篇
  1975年   8869篇
  1974年   8684篇
  1973年   9034篇
  1972年   6534篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Thin films with a nanometer-scale thickness are of great interest to both scientific and industrial communities due to their numerous applications and unique behaviors different from the bulk. However, the understanding of thin-film mechanics is still greatly hampered due to their intrinsic fragility and the lack of commercially available experimental instruments. In this review, we first discuss the progression of thin-film mechanical testing methods based on the supporting substrate: film-on-solid substrate method, film-on-water tensile tests, and water-assisted free-standing tensile tests. By comparing past studies on a model polymer, polystyrene, the effect of different substrates and confinement effect on the thin-film mechanics is evaluated. These techniques have generated fruitful scientific knowledge in the field of organic semiconductors for the understanding of structure–mechanical property relationships. We end this review by providing our perspective for their bright prospects in much broader applications and materials of interest.  相似文献   
12.
13.
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   
14.
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   
15.
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   
16.
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   
17.
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   
18.
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   
19.
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   
20.
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