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   597060篇
  免费   5461篇
  国内免费   1503篇
化学   292718篇
晶体学   9256篇
力学   30378篇
综合类   16篇
数学   83724篇
物理学   187932篇
  2021年   4270篇
  2020年   4727篇
  2019年   5327篇
  2018年   12876篇
  2017年   13443篇
  2016年   13123篇
  2015年   6612篇
  2014年   10099篇
  2013年   23952篇
  2012年   21031篇
  2011年   30200篇
  2010年   20848篇
  2009年   20747篇
  2008年   27097篇
  2007年   29411篇
  2006年   18765篇
  2005年   20663篇
  2004年   17378篇
  2003年   15963篇
  2002年   14535篇
  2001年   15616篇
  2000年   12019篇
  1999年   9208篇
  1998年   7858篇
  1997年   7743篇
  1996年   7384篇
  1995年   6581篇
  1994年   6653篇
  1993年   6292篇
  1992年   7001篇
  1991年   7175篇
  1990年   6960篇
  1989年   6745篇
  1988年   6622篇
  1987年   6686篇
  1986年   6347篇
  1985年   8160篇
  1984年   8461篇
  1983年   7078篇
  1982年   7241篇
  1981年   6929篇
  1980年   6879篇
  1979年   7109篇
  1978年   7461篇
  1977年   7260篇
  1976年   7318篇
  1975年   6770篇
  1974年   6831篇
  1973年   7042篇
  1972年   4984篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
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   
103.
104.
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   
105.
106.
Experimental Techniques - The analysis of residual stress in glass is usually carried out by means of photoelastic methods. This article considers the automation of the white light photoelastic...  相似文献   
107.
108.
Russian Journal of General Chemistry - 8-Phenyltetrazolo[5,1-b][1,3,4]thiadiazepine was obtained as a result of intermolecular cyclization of 1-amino-1H-tetrazole-5-thiol and 3-phenyl-2-propynal....  相似文献   
109.
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied.  相似文献   
110.
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