全文获取类型
收费全文 | 124篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
化学 | 70篇 |
力学 | 5篇 |
数学 | 26篇 |
物理学 | 28篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 15篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 9篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1991年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有129条查询结果,搜索用时 15 毫秒
71.
Malouche Abdelmalek Oumellal Yassine Ghimbeu Camelia Matei de Yuso Alicia Martínez Zlotea Claudia 《Journal of nanoparticle research》2017,19(8):1-11
Journal of Nanoparticle Research - Copper/silver core/shell nanopowders with different metal ratio have been elaborated by electrochemistry (ultrasound-assisted electrolysis followed by a... 相似文献
72.
Marc‐Etienne Moret Ivano Tavernelli Dr. Majed Chergui Prof. Ursula Rothlisberger Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(20):5889-5894
Hybrid DFT/classical molecular dynamics of the long‐lived triplet excited state of [Ru(bpy)3]2+ (bpy=2,2′‐bipyridine) in aqueous solution is used to investigate the solvent‐mediated electron localization and dynamics in the triplet metal‐to‐ligand charge‐transfer (MLCT) state. Our studies reveal a solvent‐induced breaking of the coordination symmetry with consequent localization of the photoexcited electron on one or two bipyridine units for the entire length of our simulation, which amounts to several picoseconds. Frequent electronic “hops” between the ligands constituting the pair are observed with a characteristic time of approximately half a picosecond. 相似文献
73.
A. Ajdarzadeh Oskouei O. Brm A. Cannizzo F. van Mourik A. Tortschanoff M. Chergui 《Journal of Molecular Liquids》2008,141(3):118
In this article we present a new photon echo set-up operating in the UV range and our first results of photon echo peak shift (PEPS) experiments of a small non-polar dye molecule, p-terphenyl (pTP), in three different solvents: ethanol, methanol and 2-propanol. The experiments show the feasibility of UV transient grating and photon echo measurements and highlight the sensitivity of this technique for the study of non-polar solvation dynamics. The transient grating experiments indicate a relaxation of the ground state hole of about 6 ps. The photon echo experiments show that while electronic dephasing occurs on timescales shorter than 100 fs, solvation dynamics timescales are in the picosecond regime, in agreement with the literature. 相似文献
74.
Nabih N. Abdelmalek 《BIT Numerical Mathematics》1971,11(4):345-367
Round off error analysis for the classical Gram-Schmidt orthogonalization method with re-orthogonalization is presented. The effect of the round-off error on the orthogonality of the derived vectors and also on the solution of the linear least squares problems when solved by the Gram-Schmidt algorithm are given. Numerical results compared favorably with the results of other methods. The classical case when no re-orthogonalization takes place is also discussed. 相似文献
75.
Abdelmalek Azizi 《Proceedings of the American Mathematical Society》2002,130(8):2197-2202
Let and be prime numbers such that and . Let , , and let be the 2-Hilbert class field of , the 2-Hilbert class field of and the Galois group of . The 2-part of the class group of is of type , so contains three extensions . Our goal is to study the problem of capitulation of the 2-classes of in , and to determine the structure of .
RS
76.
M. Chergui V. Chandrasekharan W. Böhmer R. Haensel H. Wilcke N. Schwentner 《Chemical physics letters》1984,105(4):386-390
A new ultraviolet band system identified as emission from the theoretically predicted but so far unobserved 2Φ state of NO trapped in an argon matrix is reported. The energy of the ν = 0 level is estimated to be 6.57 ± 0.015 or 6.785 ± 0.015 eV. The intensity distribution yields an internuclear distance of 1.415 ± 0.015 Å. 相似文献
77.
Gawelda W Pham VT Benfatto M Zaushitsyn Y Kaiser M Grolimund D Johnson SL Abela R Hauser A Bressler C Chergui M 《Physical review letters》2007,98(5):057401
Structural changes of the iron(II)-tris-bipyridine ([Fe(II)(bpy)(3)](2+)) complex induced by ultrashort pulse excitation and population of its short-lived (< or =0.6 ns) quintet high spin state have been detected by picosecond x-ray absorption spectroscopy. The structural relaxation from the high spin to the low spin state was followed over the entire lifetime of the excited state. A combined analysis of the x-ray-absorption near-edge structure and extended x-ray-absorption fine structure spectroscopy features delivers an Fe-N bond elongation of 0.2 A in the quintet state compared to the singlet ground state. 相似文献
78.
Cannizzo A Bräm O Zgrablic G Tortschanoff A Oskouei AA van Mourik F Chergui M 《Optics letters》2007,32(24):3555-3557
We show a femtosecond fluorescence upconversion setup with broadband detection to measure time-resolved emission spectra in the 300-550 nm range, upon excitation between 250 and 300 nm, with a time resolution of 100 fs. We present time-resolved fluorescence emission spectra of 2,5-diphenyloxazole in solution, which demonstrate the capabilities of the setup. 相似文献
79.
Montero-Cabrera LA Röhrig U Padrón-Garcia JA Crespo-Otero R Montero-Alejo AL Garcia de la Vega JM Chergui M Rothlisberger U 《The Journal of chemical physics》2007,127(14):145102
Very large molecular systems can be calculated with the so called CNDOL approximate Hamiltonians that have been developed by avoiding oversimplifications and only using a priori parameters and formulas from the simpler NDO methods. A new diagonal monoelectronic term named CNDOL/21 shows great consistency and easier SCF convergence when used together with an appropriate function for charge repulsion energies that is derived from traditional formulas. It is possible to obtain a priori molecular orbitals and electron excitation properties after the configuration interaction of single excited determinants with reliability, maintaining interpretative possibilities even being a simplified Hamiltonian. Tests with some unequivocal gas phase maxima of simple molecules (benzene, furfural, acetaldehyde, hexyl alcohol, methyl amine, 2,5 dimethyl 2,4 hexadiene, and ethyl sulfide) ratify the general quality of this approach in comparison with other methods. The calculation of large systems as porphine in gas phase and a model of the complete retinal binding pocket in rhodopsin with 622 basis functions on 280 atoms at the quantum mechanical level show reliability leading to a resulting first allowed transition in 483 nm, very similar to the known experimental value of 500 nm of "dark state." In this very important case, our model gives a central role in this excitation to a charge transfer from the neighboring Glu(-) counterion to the retinaldehyde polyene chain. Tests with gas phase maxima of some important molecules corroborate the reliability of CNDOL/2 Hamiltonians. 相似文献
80.
The photochemistry of DNA systems is characterized by the ultraviolet (UV) absorption of π-stacked nucleobases, resulting in exciton states delocalized over several bases. As their relaxation sensitively depends on local stacking conformations, disentangling the ensuing electronic and structural dynamics has remained an experimental challenge, despite their fundamental role in protecting the genome from potentially harmful UV radiation. Here we use transient absorption and transient absorption anisotropy spectroscopy with broadband femtosecond deep-UV pulses (250–360 nm) to resolve the exciton dynamics of UV-excited adenosine single strands under physiological conditions. Due to the exceptional deep-UV bandwidth and polarization sensitivity of our experimental approach, we simultaneously resolve the population dynamics, charge-transfer (CT) character and conformational changes encoded in the UV transition dipoles of the π-stacked nucleotides. Whilst UV excitation forms fully charge-separated CT excitons in less than 0.3 ps, we find that most decay back to the ground state via a back-electron transfer. Based on the anisotropy measurements, we propose that this mechanism is accompanied by a structural relaxation of the photoexcited base-stack, involving an inter-base rotation of the nucleotides. Our results finally complete the exciton relaxation mechanism for adenosine single strands and offer a direct view into the coupling of electronic and structural dynamics in aggregated photochemical systems.Despite its key role in DNA photochemistry, the decay mechanism of excitons in stacked bases has remained difficult to resolve. Ultrafast polarization spectroscopy now reveals a back-electron transfer and ultrafast base motions in adenosine strands. 相似文献