全文获取类型
收费全文 | 140篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 89篇 |
晶体学 | 1篇 |
力学 | 7篇 |
数学 | 24篇 |
物理学 | 28篇 |
出版年
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 4篇 |
2012年 | 14篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有149条查询结果,搜索用时 15 毫秒
21.
Energy transfer processes between Er3+ and Tm3+ were investigated examining the frequency upconversion emissions in a fluoroindate glass pumped at 790 nm. A 60-fold enhancement in the emission at ≈670 nm originating from Er3+ was observed when Tm3+ at concentration of 2% was introduced in a sample containing 2% of Er3+. The results are explained considering the influence of cross-relaxation processes between the active ions. 相似文献
22.
23.
Lanthanide luminescent anion sensing: evidence of multiple anion recognition through hydrogen bonding and metal ion coordination 总被引:2,自引:0,他引:2
dos Santos CM Fernández PB Plush SE Leonard JP Gunnlaugsson T 《Chemical communications (Cambridge, England)》2007,(32):3389-3391
The delayed lanthanide luminescence of the terbium [Tb(III)] diaryl-urea complex 1xTb is significantly enhanced upon sensing of dihydrogenphosphate (H2PO4(-)) in CH3CN, which occurs through multiple anion binding through hydrogen bonding interactions and potential metal ion coordination to Tb(III). 相似文献
24.
Juan‐José Cid Dr. Miguel García‐Iglesias Jun‐Ho Yum Dr. Amparo Forneli Josep Albero Eugenia Martínez‐Ferrero Dr. Purificación Vázquez Prof. Michael Grätzel Prof. Mohammad K. Nazeeruddin Prof. Emilio Palomares Prof. Tomás Torres Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(20):5130-5137
Let it shine! The impact of the anchoring group on photovoltaic performance by a series of phthalocyanine sensitisers (see figure) has been demonstrated.
25.
Bonilla JB Cid MB Contreras FX Goñi FM Martín-Lomas M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(5):1513-1528
The nature of chiro-inositol-containing inositolphosphoglycans (IPGs), reported to be putative insulin mediators, was studied by examination of the substrate specificities of the phosphatidylinositol-specific phospholipase C (PI-PLC) and the glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) by using a series of synthetic D- and L-chiro-glycosylphosphoinositides. 3-O-alpha-D-Glucosaminyl- (3) and -galactosaminyl-2-phosphatidyl-L-chiro-inositol (4), which show the maximum stereochemical similarity to the 6-O-alpha-D-glucosaminylphosphatidylinositol pseudodisaccharide motifs of GPI anchors, were synthesized and asymmetrically incorporated into phospholipid bilayers in the form of large unilamellar vesicles (LUVs). Similarly, 2-O-alpha-D-glucosaminyl- (5) and -galactosaminyl-1-phosphatidyl-D-chiro-inositol (6), which differ from the corresponding pseudodisaccharide motif of the GPI anchors only in the axial orientation of the phosphatidyl moiety, were also synthesized and asymmetrically inserted into LUVs. The cleavage of these synthetic molecules in the liposomal constructs by PI-PLC from Bacillus cereus and by GPI-PLD from bovine serum was studied with the use of 6-O-alpha-D-glucosaminylphosphatidylinositol (7) and the conserved GPI anchor structure (8) as positive controls. Although PI-PLC cleaved 3 and 4 with about the same efficiency as 7 and 8, this enzyme did not accept 5 or 6. GPI-PLD accepted both the L-chiro- (3 and 4) and the D-chiro- (5 and 6) glycosylinositolphosphoinositides. Therefore, IPGs containing L-chiro-inositol only are expected to be released from chiro-inositol-containing GPIs if the cleavage is effected by a PI-PLC, whereas GPI-PLD cleavage could result in both L-chiro- and D-chiro-inositol-containing IPGs. 相似文献
26.
Boron compounds have been traditionally regarded as "Lewis acids" preferring to accept electrons rather than donate them in the course of their reactions but current examples of unusual reactivity between tricoordinated boranes and electrophilic sites suggest a new conceptual context for the boryl moieties, based on their nucleophilic character which can be enhanced depending on the substituents on boron. 相似文献
27.
M. A. García del Cid M. G. Prolongo C. Salom C. Arribas M. Sánchez-Cabezudo R. M. Masegosa 《Journal of Thermal Analysis and Calorimetry》2012,108(2):741-749
Epoxy–clay nanocomposites have been prepared with an organically modified montmorillonite. The epoxy network was based on
diglycidyl ether of bisphenol A (DGEBA) cured with diaminodiphenylmethane (DDM). The stoichiometry DGEBA–DDM was varied, the
molar ratio of amine hydrogen/epoxy groups, r, ranged from 0.85 to 1.15. The influence of stoichiometry on curing and properties of the nanocomposites was studied using
differential scanning calorimetry, dynamic mechanical thermal analysis and X-ray diffraction. All nanocomposites had intercalated
clay structures. The clays accelerated the curing reaction whose rate was also increased when increasing r. The heat of reaction, −ΔH (J/g epoxy), increased as r increased, reaching a constant value for r ≥ 1. In the presence of clays −ΔH was lower than in the neat DGEBA–DDM. The glass transition temperature (T
g) of the neat epoxy thermosets reached a maximum at r = 1; however, the nanocomposites showed the T
g maximum at 0.9 < r < 1. The presence of clay lowered the T
g for r > 0.94 and raised T
g for r ≤ 0.85. The elastic modulus of neat epoxy thermosets reached a maximum in the rubber state and a minimum in the glassy state
at r = 1. The nanocomposites showed similar behavior, but the maximum and the minimum values of the elastic modulus were reached
at stoichiometry r < 1. The comparison of the properties of neat epoxy with those of the nanocomposites varying the stoichiometry indicates
that the clay itself induces stoichiometric changes in the system. 相似文献
28.
Vehicle and crew scheduling for urban bus lines 总被引:1,自引:0,他引:1
Maikol M. Rodrigues Cid C. de Souza Arnaldo V. Moura 《European Journal of Operational Research》2006,170(3):844-862
A solution to the urban transportation problem is given by vehicle and crew schedules. These schedules must meet the passenger demand and satisfy technical and contractual restrictions stemming from the daily operation of the lines, while optimizing some measure of operational cost. This work describes a computational tool developed to solve the urban transportation problem in the large metropolitan area of São Paulo, Brazil. The techniques used are based on integer programming models coupled with heuristics. The former produces good feasible solutions, and the latter improves the quality of the final solutions. While the operational and labor restrictions are specific to the city of São Paulo, the same ideas can inspire similar approaches for solving the urban transportation problem arising in other metropolitan areas. 相似文献
29.
José M. Cid 《Tetrahedron letters》2004,45(6):1133-1136
A method for the selective α-monoallylation of phenyl ketones and benzocycloalkanones with allyl alcohol under microwave irradation is described. The corresponding α-allyl ketones are obtained in moderate to good yields with only minor quantities of diallylation by-products. 相似文献
30.
Íngrid Amer Cid Yera Ye Ussembayev Kristiaan Neyts Filip Strubbe 《Electrophoresis》2021,42(16):1623-1635
The electrophoretic mobility of micron-scale particles is of crucial importance in applications related to pharmacy, electronic ink displays, printing, and food technology as well as in fundamental studies in these fields. Particle mobility measurements are often limited in accuracy because they are based on ensemble averages and because a correction for electroosmosis needs to be made based on a model. Single-particle approaches are better suited for examining polydisperse samples, but existing implementations either require multiple measurements to take the effect of electroosmosis into account or are limited in accuracy by short measurement times. In this work, accurate characterization of monodisperse and polydisperse samples is achieved by measuring the electrophoretic mobility on a particle-to-particle basis while suppressing electroosmosis. Electroosmosis can be suppressed by measuring in the middle of a microchannel while applying an AC voltage with a sufficiently high frequency. An accurate measurement of the electrophoretic mobility is obtained by analyzing the oscillating particle motion for per particle with a high-speed camera measuring at , synchronized to the applied electric field. Attention is paid to take into account the effect of the rolling shutter and the non-uniform sampling in order to obtain the accurate amplitude and phase of the electrophoretic mobility. The accuracy of method is experimentally verified and compared with a commercial apparatus for polystyrene microspheres in water. The method is further demonstrated on a range of particle materials and particle sizes and for a mixture of positively and negatively charged particles. 相似文献