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   330507篇
  免费   3457篇
  国内免费   937篇
化学   165476篇
晶体学   5392篇
力学   15540篇
综合类   7篇
数学   38532篇
物理学   109954篇
  2021年   3135篇
  2020年   3347篇
  2019年   3775篇
  2018年   5211篇
  2017年   5444篇
  2016年   7391篇
  2015年   4164篇
  2014年   7056篇
  2013年   15931篇
  2012年   12427篇
  2011年   14873篇
  2010年   11050篇
  2009年   10940篇
  2008年   13294篇
  2007年   13229篇
  2006年   12196篇
  2005年   10560篇
  2004年   9863篇
  2003年   8727篇
  2002年   8700篇
  2001年   10421篇
  2000年   7674篇
  1999年   5984篇
  1998年   4981篇
  1997年   4822篇
  1996年   4491篇
  1995年   3881篇
  1994年   3843篇
  1993年   3718篇
  1992年   4117篇
  1991年   4324篇
  1990年   4111篇
  1989年   4021篇
  1988年   3789篇
  1987年   3925篇
  1986年   3698篇
  1985年   4647篇
  1984年   4695篇
  1983年   3893篇
  1982年   3981篇
  1981年   3702篇
  1980年   3653篇
  1979年   3919篇
  1978年   3907篇
  1977年   3914篇
  1976年   3890篇
  1975年   3684篇
  1974年   3618篇
  1973年   3653篇
  1972年   2604篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity).  相似文献   
2.
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine...  相似文献   
3.
4.
5.
6.
7.
8.
This study was aimed at the development of a conductometric biosensor based on acetylcholinesterase considering the feasibility of its application for the inhibitory analysis of various toxicants. In this paper, the optimum conditions for enzyme immobilization on the transducer surface are selected as well as the optimum concentration of substrate for inhibitory analysis. Sensitivity of the developed biosensor to different classes of toxic compounds (organophosphorus pesticides, heavy metal ions, surfactants, aflatoxin, glycoalkaloids) was tested. It is shown that the developed biosensor can be successfully used for the analysis of pesticides and mycotoxins, as well as for determination of total toxicity of the samples. A new method of biosensor analysis of toxic substances of different classes in complex multicomponent aqueous samples is proposed.  相似文献   
9.
10.
Oxidation catalysis is used to increase the performance of hydrogen peroxide in laundry bleach applications. Bleach catalysts provide cost‐effective, energy‐saving and environmentally friendly bleach systems yielding perfect stain removal at lower temperatures. This comparative study is based on the synthesis of bis[bis(salicylhydrazonephenoxy)manganese(III)] phthalocyaninatozinc(II) ( 2 ), bis[bis(salicylhydrazonephenoxy)cobalt(III)] phthalocyaninatozinc(II) ( 3 ) and bis[bis(salicylhydrazonephenoxy)iron(III)] phthalocyaninatozinc(II) ( 4 ) as tri‐nuclear complexes consisting of two Schiff base complexes substituting a zinc phthalocyanine. Complexion on the periphery to obtain complexes 2 , 3 , 4 was performed through the reaction of a Schiff base‐substituted phthalocyanine using MnCl2?4H2O, CoCl2?6H2O or FeCl3?6H2O salts in basic condition in dimethylformamide. Fourier transform infrared, 1H NMR, 13C NMR, UV–visible, inductively coupled plasma optical emission and mass spectra were applied to characterize the prepared compounds. The bleach performances of the three phthalocyanine compounds 2 , 3 , 4 were examined by the degradation of morin as hydrophilic dye. The degradation progress in the presence of catalysts 2 , 3 , 4 /H2O2 combination in aqueous solution was investigated using an online spectrophotometric method. It was found that the catalysts 2 , 3 , 4 exhibited better bleaching performance at 25 °C than tetraactylethylethylenediamine as bleach activator used in powder detergent formulations for stain removal. Copyright © 2015 John Wiley & Sons, Ltd.  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