全文获取类型
收费全文 | 128篇 |
免费 | 3篇 |
专业分类
化学 | 93篇 |
力学 | 1篇 |
数学 | 15篇 |
物理学 | 22篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 19篇 |
2011年 | 10篇 |
2010年 | 2篇 |
2009年 | 9篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有131条查询结果,搜索用时 31 毫秒
21.
22.
Dimitris Georgiou Athanasios Megaritis Kyriakos Papadopoulos Vasilios Petropoulos 《Quaestiones Mathematicae》2016,39(3):363-379
Let Y and Z be two fixed topological spaces and C(Y, Z) the set of all continuous maps from Y into Z. We construct and study topologies on C(Y, Z) that we call Fn(τn)-family-open topologies. Furthermore, we find necessary and su?cient conditions such that these topologies to be splitting and jointly continuous. Finally, we present questions concerning a further study on this area. 相似文献
23.
Diffusion jumps of small molecules dispersed in chain molecules or other kinds of slow-moving matrices have already been observed in many previous simulations of such systems, and their treatment led to important qualitative conclusions. In the present work, a new, very simple yet effective method is described, allowing for both identification of individual penetrant jump events and their quantitative treatment in a statistical sense. The method is applied in equilibrium Molecular Dynamics simulations for systems of gaseous alkanes, methane through n-butane, including also a mixture of methane and n-butane, dispersed in n-decane or n-eicosane. Equilibration and attainment of a linear diffusion regime is confirmed by means of various criteria, and the jumps detection method is applied to all systems studied. The results obtained clearly show the existence of distinct jump events in all cases, although the average jump length is reduced with penetrant or liquid alkane molecular weight. The method allows one to determine the average jump length and the corresponding jumps frequency. On the basis of these results, it was possible to estimate a random walk type diffusion coefficient, D(s,jumps), of the penetrants, which was found to be substantially lower compared with the overall diffusion coefficient D(s,MSD) obtained by the mean square displacement method. This finding led us to assume that the overall penetrants' diffusion in the studied systems is a combination of longer jumps with a smoother and more gradual displacement, a result that confirms assumptions suggested in previous studies. 相似文献
24.
25.
26.
Jack Dalton Gareth W. Richings Jack M. Woolley Temitope T. Abiola Scott Habershon Vasilios G. Stavros 《Molecules (Basel, Switzerland)》2021,26(24)
Para-hydroxy methylcinnamate is part of the cinnamate family of molecules. Experimental and computational studies have suggested conflicting non-radiative decay routes after photoexcitation to its S1(ππ*) state. One non-radiative decay route involves intersystem crossing mediated by an optically dark singlet state, whilst the other involves direct intersystem crossing to a triplet state. Furthermore, irrespective of the decay mechanism, the lifetime of the initially populated S1(ππ*) state is yet to be accurately measured. In this study, we use time-resolved ion-yield and photoelectron spectroscopies to precisely determine the S1(ππ*) lifetime for the s-cis conformer of para-hydroxy methylcinnamate, combined with time-dependent density functional theory to determine the major non-radiative decay route. We find the S1(ππ*) state lifetime of s-cis para-hydroxy methylcinnamate to be ∼2.5 picoseconds, and the major non-radiative decay route to follow the [1ππ*→1nπ*→3ππ*→S0] pathway. These results also concur with previous photodynamical studies on structurally similar molecules, such as para-coumaric acid and methylcinnamate. 相似文献
27.
28.
This paper provides the construction of a powerful and efficient computational method, that translates Polyrakis algorithm [I.A. Polyrakis, Minimal lattice-subspaces, Trans. Am. Math. Soc. 351 (1999) 4183–4203, Theorem 3.19] for the calculation of lattice-subspaces and vector sublattices in . In the theory of finance, lattice-subspaces have been extensively used in order to provide a characterization of market structures in which the cost-minimizing portfolio is price-independent. Specifically, we apply our computational method in order to solve a cost minimization problem that ensures the minimum-cost insured portfolio. 相似文献
29.
Cristina Jimnez-Holgado Paola Calza Debora Fabbri Federica Dal Bello Claudio Medana Vasilios Sakkas 《Molecules (Basel, Switzerland)》2021,26(17)
This study investigated the direct and indirect photochemical degradation of citalopram (CIT), a selective serotonin reuptake inhibitor (SSRI), under natural and artificial solar radiation. Experiments were conducted in a variety of different operating conditions including Milli-Q (MQ) water and natural waters (lake water and municipal WWT effluent), as well as in the presence of natural water constituents (organic matter, nitrate and bicarbonate). Results showed that indirect photolysis can be an important degradation process in the aquatic environment since citalopram photo-transformation in the natural waters was accelerated in comparison to MQ water both under natural and simulated solar irradiation. In addition, to investigate the decontamination of water from citalopram, TiO2-mediated photocatalytic degradation was carried out and the attention was given to mineralization and toxicity evaluation together with the identification of by-products. The photocatalytic process gave rise to the formation of transformation products, and 11 of them were identified by HPLC-HRMS, whereas the complete mineralization was almost achieved after 5 h of irradiation. The assessment of toxicity of the treated solutions was performed by Microtox bioassay (Vibrio fischeri) and in silico tests showing that citalopram photo-transformation involved the formation of harmful compounds. 相似文献
30.
Westlake P Siozos P Philippidis A Apostolaki C Derham B Terlixi A Perdikatsis V Jones R Anglos D 《Analytical and bioanalytical chemistry》2012,402(4):1413-1432
Wall paintings spanning two millennia of Cretan painting history and technology were analysed in an effort to determine similarities
and evolutions of painting materials and technology. A multi-technique approach was employed that combined the use of (a)
laser-induced breakdown spectroscopy (LIBS) and Raman microspectroscopy, based on mobile instrumentation, appropriate for
rapid, routine-level object characterization, and (b) non-destructive X-ray diffractometry (XRD), performed directly on the
wall painting fragment, which provides detailed information on the minerals constituting the paint. Elemental analysis data
obtained through LIBS were compared with molecular and crystal structure information from Raman spectroscopy and XRD. Cross-sections
from selected samples were also investigated by means of optical microscopy and scanning electron microscopy coupled to micro-probe
analysis and X-ray mapping that enabled identification of several mineral components of the paint confirming the results of
the XRD analysis. In parallel, replica wall paintings, created with known pigments and binding media for reference purposes,
were examined with optical microscopy and stain tested for organic materials. The overall study shows that the LIBS and Raman
techniques offer key advantages, such as instrument mobility and speed of data collection and interpretation that are particularly
important when dealing with on-site investigations. Thus, they are capable of providing important compositional information
in an effective manner that enables quick surveying of wall paintings and permit targeted sample selection for further analysis
by advanced laboratory techniques. 相似文献