全文获取类型
收费全文 | 277篇 |
免费 | 10篇 |
专业分类
化学 | 225篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 12篇 |
物理学 | 47篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 10篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 8篇 |
2012年 | 14篇 |
2011年 | 14篇 |
2010年 | 14篇 |
2009年 | 8篇 |
2008年 | 10篇 |
2007年 | 24篇 |
2006年 | 19篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1957年 | 2篇 |
1932年 | 1篇 |
排序方式: 共有287条查询结果,搜索用时 31 毫秒
191.
192.
S.M. Borisov G. Nuss W. Haas R. Saf M. Schmuck I. Klimant 《Journal of photochemistry and photobiology. A, Chemistry》2009,201(2-3):128-135
New platinum(II) and palladium(II) complexes with fluorinated benzoporphyrins are prepared and characterized. The photo-physical and electrochemical properties, as well as quenching by oxygen are investigated. The complexes possess highly efficient room-temperature NIR phosphorescence and are excitable with blue- and red-light. The fluorinated derivatives show improved photo-physical properties and photo-stability. The new dyes are particularly suitable as indicators for the use in optical oxygen sensors. 相似文献
193.
194.
K. Bajema R. Merlin F.-Y. Juang S.-C. Hong J. Singh P.K. Bhattacharya 《Superlattices and Microstructures》1987,3(6)
We report on a Raman scattering study of the electric-field dependence of c0 → c1 intersubband transitions of
electrons in a 264 Å GaAs- Al0.3Ga0.7As quantum-well structure. The measured Stark shifts are in very good agreement with theoretical predictions. The intensity of the intersubband peak increases rapidly with applied field due to parity-mixing. In contrast to the enhanced broadening shown by excitation resonances, the width of c0 → c1 is nearly independent of the field. This feature is attributed to effects of structural disorder. 相似文献
195.
196.
Pablo J. Baricelli Luis G. Melean Santiago Ricardes Victor Guanipa Mariandry Rodriguez Carlos Romero Alvaro J. Pardey Sergio Moya Merlin Rosales 《Journal of organometallic chemistry》2009,694(21):3381-3385
The complex Mo(CO)3(NCMe)(PPh3)2, was synthesized by the reaction of Mo(NCMe)3(CO)3 with two equivalents of PPh3 and characterized by UV–Vis, IR, NMR and X-ray diffraction. This complex was used as a catalyst precursor for the hydrogenation of 1-hexene, styrene, cyclohexene and 2,3-dimethyl-1-butene and their mixtures under moderate conditions in homogeneous media. Under mild reaction conditions (T = 373 K, P = 60 atm), the substrates showed the following reactivity order: styrene > 1-hexene > cyclohexene > 2,3-dimethyl-1-butene. A quaternary equimolar mixture showed a different hydrogenation order: 1-hexene > cyclohexene > styrene > 2,3-dimethyl-1-butene; the presence of dibenzothiophene or mercury does not interfere with the activity of the catalyst. 相似文献
197.
Coherent time-domain optical experiments on GaAs-AlAs superlattices reveal the existence of an unusually long-lived acoustic mode at approximately 0.6 THz which couples weakly to the environment by evading the sample boundaries. Classical as well as quantum states that steer clear of surfaces are generally shown to occur in the spectrum of periodic structures, for most boundary conditions. These surface-avoiding waves are associated with frequencies outside forbidden gaps and wave vectors in the vicinity of the center and edge of the Brillouin zone. Possible consequences for surface science and resonant-cavity applications are discussed. 相似文献
198.
Rosales Merlin González Ángel Mora Milagros Nader Nidal Navarro Janeth Sánchez Ligbel Soscún Humberto 《Transition Metal Chemistry》2004,29(2):205-211
Kinetic and mechanistic studies of the homogeneous hydrogenation of cyclohexanone were carried out using the cationic complexes [MH(CO)(NCMe)2(PPh3)2]BF4 (M = Ru, Os) as the catalyst precursors, which were very efficient under mild reaction conditions in 2-methoxyethanol solution. For both complexes, the catalytic hydrogenation of cyclohexanone proceeds according to the rate law r = k[M][H2]. The activation parameters were also calculated, the activation energy for the osmium catalyst being higher than for the ruthenium(I). All experimental data are consistent with a mechanism involving the oxidative addition of hydrogen as the rate-determining step of the catalytic cycle. Finally, the [MH(CO)(NCMe)2(PPh3)2]BF4 complexes were efficient precatalysts for the selective reduction of 2-cyclohexen-1-one to cyclohexanone; the reduction of the CO group of cyclohexanone only begins to take place when the ,-unsaturated ketone has been consumed. 相似文献
199.
We report the first experimental demonstration of quantum squeezing of a collective spin-wave excitation (magnon) using femtosecond optical pulses to generate correlations involving pairs of spins in an antiferromagnetic insulator MnF2. In the squeezed state, the fluctuations of the magnetization of a crystallographic unit cell vary periodically in time and are reduced below that of the ground-state quantum noise. 相似文献
200.
A new tris-cation 1 binds N-acetyl amino acid carboxylates in water even at millimolar salt concentrations with Kass approximately 103 M-1 due to a clustering of electrostatic interactions. Binding is efficient enough to allow a naked-eyed detection using an indicator displacement assay. Furthermore, receptor 1 shows an unexpected 2:1 complex formation with strong positive cooperativity with glutamate but not aspartate. 相似文献