全文获取类型
收费全文 | 189篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 123篇 |
晶体学 | 2篇 |
数学 | 60篇 |
物理学 | 7篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 17篇 |
2012年 | 11篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 13篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 7篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1976年 | 2篇 |
排序方式: 共有192条查询结果,搜索用时 15 毫秒
11.
Ciucanu I Kaykhaii M Montero L Pawliszyn J Szubra J 《Journal of chromatographic science》2002,40(6):350-354
A novel method for the continuous monitoring of thermooxidative degradation products of polystyrene by membrane extraction with sorbent interface (MESI) and gas chromatography (GC) is developed. The results are compared with solid-phase microextraction-GC, which can extract gases, vapors, and aerosols. The volatile and semivolatile degradation products are identified by mass spectrometry. The membrane used in the MESI-GC analysis shows a high permeation for volatile aromatic hydrocarbons; a low permeation for corresponding volatile aldehydes; and no permeation for less volatile alcohols, acids, and degradation products with a high molecular weight, thus reducing significantly the number of compounds detected from MESI-GC. Sensitivity of the method depends on the time of trapping, which is limited by the breakthrough of the trap. By heating the trap at fixed intervals of time, consecutive gas chromatograms are obtained. 相似文献
12.
We introduce the notion of the Fourier and Fourier-Stieltjes algebras of a
topological *-semigroup and show that these are commutative Banach algebras.
For a class of foundation semigroups, we show that these are preduals of von
Neumann algebras. 相似文献
13.
Solvent effects on the initial and transition states for the solvolysis of the trans-dichlorobis-(N-methylethylenediamine)cobalt(III), (meen), complex have been investigated in the 25–55 °C range in aqueous DMSO mixtures, of varying solvent composition up to 60% by vol. The log of the first order rate constant, k, varies non-linearly with the reciprocal of the dielectric constant at the same temperature, due to differential solvation of the initial and transition states. The changes in the enthalpy, H
, and entropy, S
, of activation with the mole fraction of the co-solvent show extrema at the composition range where the change in solvent structure occurs. The application of a free energy cycle to the process of the initial state going to the transition state suggests that the effect of solvent structure on the complex ion in the transition state dominates the initial state and that this effect increases as the mole fraction of co-solvent increases. 相似文献
14.
Massoud Malek 《Linear and Multilinear Algebra》1986,19(4):347-355
The purpose of this paper is to give some necessary conditions on a substochastic matrix which maximizes the values of Per(I-A) for A taken in the semigroup of n × n substochastic matrices, and to determine the exact value of the maximum which is found to be 2[n/2]. 相似文献
15.
Mashaallah Rahmani Massoud Kaykhaii Zahra Safari Ommolbanin Ansari Shahrzad Jaberi Nasab 《Chromatographia》2017,80(1):109-117
Three new dispersive liquid–liquid microextraction (DLLME) methods, air-assisted (AA-DLLME), vortex-assisted (VA-DLLME) and ultrasound-assisted (UA-DLLME), were compared from the point of view of their analytical application for preconcentration of trace amounts of benzene, toluene, ethylbenzene and xylene isomers (BTEX) in water samples. In all of these methods, no dispersive solvent is required and dispersion of extractant is carried out by air bubbles, vortex and ultrasound for AA-DLLEM, VA-DLLME, and UA-DLLME, respectively. Advantages and disadvantages of these three liquid phase microextraction methods and their capability in dispersion of a similar extractant phase in sample solutions were comprehensively compared. All other extraction parameters, which have an influence on the microextraction, were also investigated and optimized. Under optimized conditions, analytical figures of merit for the three techniques were determined and compared. It was found that the limit of detection of the three methods is almost the same, while AA-DLLME has a wider linear dynamic range and the shortest analysis time. Enrichment factors of 182, 45 and 245 were achieved for AA-DLLEM, VA-DLLME, and UA-DLLME, respectively. 相似文献
16.
Massoud Kaykhaii Greg W. Dicinoski Rebecca Smedley Janusz Pawliszyn Paul R. Haddad 《Journal of chromatography. A》2010,1217(20):3452-3456
The use of a functionalized latex nanoparticle coating as a new sorbent phase for solid-phase microextraction (SPME) was examined. By means of electrostatic absorption onto ionized silanol groups, a fused-silica rod was coated with polymeric nanoparticles functionalized with quaternary ammonium groups. Optimum conditions for the preparation of the coated fibre are presented. The fibre was used for the extraction of a mixture of seven anions from water samples which are analysed by coupling the SPME fibre to an ion chromatographic system via a special interface. The results obtained proved the suitability of this novel coating as a new SPME fibre. A linear calibration for the target analytes was achieved over the concentration range from 5 μg L−1 to 5 mg L−1 (r2 > 0.988), while limits of detection for these ions were all below 3.7 μg L−1 (S/N = 3). The reproducibility of a single fibre (n = 4) under similar conditions was between 7 and 12%, while the fibre to fibre reproducibility (n = 5) was between 8.9 and 14%. 相似文献
17.
We show that for an inverse semigroup S with the set idempotents E acting on S trivially from left and by multiplication from right, any bounded module derivation from \(\ell ^1(S)\) to \(({\ell ^1(S)}/{J})^*=J^{\perp }\) is inner, where J is the closed ideal generated by elements of the form \(\delta _{set}-\delta _{st}\) with \(s,t\in S\) and \(e\in E\). 相似文献
18.
We study the weak module amenability of Banach algebras which are
Banach module over another Banach algebra with compatible actions.
As an example we show that the semigroup algebra of a commutative inverse
semigroup is always weakly amenable as a module over the semigroup
algebra of its subsemigroup of idempotents. 相似文献
19.
A straightforward spectrophotometric method is described for the determination of uranium(VI) in trialkylamine sulphate extracts in kerosene diluent; 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) is used for colour formation without resort to backextraction into an aqueous phase. The method provides good tolerance to sulphate ion and rapid colour development and appears to be free from interference when applied to extracts from uranium sulphate leach liquors. 相似文献
20.