全文获取类型
收费全文 | 2334篇 |
免费 | 64篇 |
国内免费 | 2篇 |
专业分类
化学 | 1314篇 |
晶体学 | 48篇 |
力学 | 78篇 |
数学 | 557篇 |
物理学 | 403篇 |
出版年
2023年 | 12篇 |
2022年 | 29篇 |
2021年 | 39篇 |
2020年 | 48篇 |
2019年 | 61篇 |
2018年 | 98篇 |
2017年 | 103篇 |
2016年 | 110篇 |
2015年 | 81篇 |
2014年 | 126篇 |
2013年 | 336篇 |
2012年 | 126篇 |
2011年 | 161篇 |
2010年 | 160篇 |
2009年 | 105篇 |
2008年 | 139篇 |
2007年 | 128篇 |
2006年 | 84篇 |
2005年 | 48篇 |
2004年 | 47篇 |
2003年 | 31篇 |
2002年 | 34篇 |
2001年 | 21篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 15篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 17篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1968年 | 9篇 |
排序方式: 共有2400条查询结果,搜索用时 46 毫秒
1.
Functional zinc(II) phthalocyanines bearing Schiff base complexes as oxidation catalysts for bleaching systems
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
2.
3.
In this study, stoichiometric protonation constants of L-tyrosine, L-cysteine, L-tryptophane, L-lysine, and L-histidine, and
their methyl and ethyl esters in water and ethanol–water mixtures of 30, 50, and 70% ethanol (v/v), were determined potentiometrically
using a combined pH electrode system calibrated as the concentration of hydrogen ion. Titrations were performed at 25∘C and the ionic strength of the medium was maintained at 0.10 mol⋅L−1 using sodium chloride. Protonation constants were calculated by using the BEST computer program. The effect of solvent composition
on the protonation constants is discussed. The log10 K2 values of esters generally decreased with increasing ethanol content. However, the log10 K1 values of the esters of L-tyrosine, L-cysteine, and L-tryptophane were found to increase with increasing ethanol content
in contrast those of L-lysine and L-histidine esters. 相似文献
4.
Suppose there exists a global solution u to the incompressible Navier–Stokes equations, such that . We prove that its norm goes to 0 at infinity. We next use this fact to control the norm of u, and finally we prove that such a solution is stable. To cite this article: I. Gallagher et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 289–292. 相似文献
5.
Stefan Cobzaş 《Acta Appl Math》2004,80(3):363-363
6.
Mustafa Çelebier Ertan Şahin Nilgün Ancın Nurşen Altuntaş Öztaş Selma Gül Öztaş 《应用有机金属化学》2007,21(10):viii-viii
The article referenced above was first published online on 30 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
7.
We continue the studies on the so–called genuine Bernstein–Durrmeyer operators U
n
by establishing a recurrence formula for the moments and by investigating the semigroup T(t) approximated by U
n
. Moreover, for sufficiently smooth functions the degree of this convergence is estimated. We also determine the eigenstructure
of U
n
, compute the moments of T(t) and establish asymptotic formulas.
Received: January 26, 2007. 相似文献
8.
We give a concise review and extension of S-procedure that is an instrumental tool in control theory and robust optimization analysis. We also discuss the approximate S-Lemma as well as its applications in robust optimization.The many suggestions and detailed corrections of an anonymous referee are gratefully acknowledged. 相似文献
9.
Dilek Yildiz JeronimusP.A.J. vanBeeck MichelL. Riethmuller 《Particle & Particle Systems Characterization》2004,21(5):390-402
Two‐phase flows hold an interest in many areas of science and engineering. In the safety field, one such topic is the accidental release of flammable and toxic pressure‐liquefied gases. In case of such a release, a flashing vapor explosion takes place resulting in a very dense two‐phase cloud. If the released substance is flammable, this cloud can be combustible and can lead to deflagration or detonation. For understanding the source processes of flashing and risk assessment, data related to cloud characteristics (i.e. droplet size, velocity etc.) is needed especially in the near region of the release. Due to the non‐equilibrium nature of the near field regions accurate data measurement is not possible with intrusive techniques. Therefore, laser‐based optical techniques (like Particle Image Velocimetry (PIV), Particle Tracking Velocimetry and Sizing (PTVS), Phase Doppler Anemometry (PDA) etc.) present the only possibility to obtain information for particle diameter and velocity evolution in this harsh environment. 相似文献
10.
Adsorption of the copper ions from aqueous solutions, benzene, and water on the active carbon obtained by chemical activation
from walnut shells was studied. The active carbon was additionally oxidized with hydrogen peroxide and then impregnated with
nitrogen-containing compounds. As a result of impregnation with melamine, a secondary porosity is formed within the oxidized
active carbon, leading to an increase in the specific surface of the sorbent. A modified carbon surface is heterogeneous,
and the carbons themselves exhibit catalytic activity in the oxidation of luminol and decomposition of hydrogen peroxide. 相似文献