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61.
The preliminary analysis of the DFT calculations and the high-resolution Fourier transform spectrum of the ν7 band of CD3NO2 have been carried out for the first time. The rotational structure up to J = 10 have been fitted using Watson’s A-reduction in I
r
representation with a standard deviation of 0.0048cm−1. The rotational constants A, B, C have been obtained for the ν7 state of CD3NO2 with good statistical significance. 相似文献
62.
Somesh Kr. Bhattacharya Anjali Kshirsagar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(3):355-364
Density functional calculations of structural and electronic properties
of stoichiometric and nonstoichiometric
CdTe clusters, containing up to few tens of atoms, are carried out
using projector augmented wave method.
Molecular dynamics has been performed
for Cd12Te12 and Cd15Te15
to predict the structure corresponding to global energy minimum.
Cage type structures and bulk fragments, both in zinc blende and
wurtzite structures, are used as starting geometries and
conjugate gradient method is used to locate the local energy minima for other clusters.
The aim of these calculations is to get the energetically favorable probable
structures, to be compared with the experimentally known
structures. Clusters are relaxed both in vacuum and in
the presence of surface passivating ligands and the resulting structural
rearrangement is analyzed. As expected, passivation increases the stability of an
individual cluster, as indicated by specific properties like binding energy,
vertical detachment energy, electron affinity etc.
Passivation also locks the symmetry for three-dimensional structures but the small
CdnTen (1 ≤ n ≤ 6) clusters, which are planar, attain higher
symmetry structures on passivation.
We observe `self-healing' mechanism viz., opening of optical
gap on relaxation without the aid of passivating ligand, in CdTe clusters as
observed in CdSe clusters [A. Puzder et al., Phys. Rev. Lett. 92,
217401 (2004)]. However, we note that 'self-healing' is a stoichiometry dependent
phenomenon. Te atoms are found to achieve a total coordination of 4 on passivation,
a fact useful in chemical synthesis of nanoclusters. 相似文献
63.
LeClair P Swagten HJ Kohlhepp JT van De Veerdonk RJ de Jonge WJ 《Physical review letters》2000,84(13):2933-2936
Co/Al2O3/Co magnetic tunnel junctions with an interfacial Cu layer have been investigated with in situ growth characterization and ex situ magnetotransport measurements. Cu interlayers grown on Co give an approximately exponential decay of the tunneling magnetoresistance with xi approximately 0.26 nm while those grown on Al2O3 have a decay length of 0.70 nm. The difference in decay lengths can be explained by different growth morphologies, and in this way clarifies a present disagreement in the literature. For monolayer coverage of Cu, we show that the tunneling spin polarization is suppressed by at least a factor of 2 compared to Co and beyond approximately 5 ML it becomes vanishingly small. 相似文献
64.
Le Roy RJ 《Journal of Molecular Spectroscopy》1999,194(2):189-196
A new way of representing vibration-rotation term values for multiple isotopomers of a given electronic state of a diatomic molecule is presented which resolves problems associated with the way the conventional combined isotopomer expansion represents the atomic mass-dependent JWKB and Born-Oppenheimer breakdown correction terms. Its application to infrared and microwave data for HF and DF yields new Dunham expansion coefficients and Born-Oppenheimer breakdown correction terms for this species. This procedure is implemented in a generally available computer program for fitting to various types of data involving one or several electronic states of multiple isotopomers of a diatomic molecule. Copyright 1999 Academic Press. 相似文献
65.
Sachin D. Kshirsagar Ummar Pasha Shaik M. Ghanashyam Krishna Surya P. Tewari 《Applied Physics A: Materials Science & Processing》2013,111(3):861-865
Laser-induced darkening and crystallization of ZnTe-based thin films is reported. ZnTe thin films of 1500-nm thickness were deposited on bare and Zn buffer layered borosilicate glass substrates. The as-deposited films were subjected to laser irradiation at 532 nm. The as-deposited films were amorphous but transformed to the crystalline state under influence of the laser treatment. The X-ray diffraction patterns revealed that the ZnTe crystallized in the zinc blende structure. In addition, presence of peaks from Te was observed, signifying the dissociation of ZnTe. The spectral transmission of the films decreased by more than 15 % under the influence of the laser irradiation and this was accompanied by a red shift in the band gap. These results clearly point to the occurrence of laser-induced darkening and crystallization of the films. To understand the mechanisms of darkening and crystallization, all the films were annealed at 500 °C for 60 min. Similar to the laser-irradiated samples, the thermally annealed films showed an amorphous–crystalline transition, presence of Te in the X-ray diffraction patterns as well as a large decrease in spectral transmission (>70 %). Photoinduced emission analysis carried out as a function of laser intensities indicated a strong red shift of about 51 meV in emission energy with increase in laser intensity due to the photodarkening. The peak position of the emission spectrum can be tuned by increasing the laser intensity and is completely reversible with decrease in laser intensity. It is proposed that laser-induced darkening occurs due to the dissociation of ZnTe into ZnTe and Te and that crystallization is a consequence of laser annealing. 相似文献
66.
67.
68.
69.
Yan B Fang L Irving M Zhang S Boldi AM Woolard F Johnson CR Kshirsagar T Figliozzi GM Krueger CA Collins N 《Journal of combinatorial chemistry》2003,5(5):547-559
The quality of combinatorial libraries determines the success of biological screening in drug discovery programs. In this paper, we evaluate and compare various methods for measuring identity, purity, and quantity (yield) of combinatorial libraries. Determination of quantitative purity reveals the true library quality and often indicates potential quality problems before full-scale library production. The relative purity can be determined for every member in a large library in a high-throughput mode, but must be cautiously interpreted. In particular, many impurities are not observable by relative purity measurements using detectors such as UV(214), UV(254), and evaporative light-scattering detection. These "invisible" impurities may constitute a significant portion of the sample weight. We found that TFA, plastic extracts, inorganic compounds, and resin washout are among these impurities. With compelling evidence, we reach a conclusion that purification is the only way to remove "invisible" impurities and improve the quantitative purity of any compound even though some compounds may have a high relative purity before purification. 相似文献
70.
The authors present theoretical results describing the adsorption of H2 and H2S molecules on small neutral and cationic gold clusters (Au(n)((0/+1)), n=1-8) using density functional theory with the generalized gradient approximation. Lowest energy structures of the gold clusters along with their isomers are considered in the optimization process for molecular adsorption. The adsorption energies of H2S molecule on the cationic clusters are generally greater than those on the corresponding neutral clusters. These are also greater than the H2 adsorption energies on the corresponding cationic and neutral clusters. The adsorption energies for cationic clusters decrease with increasing cluster size. This fact is reflected in the elongations of the Au-S and Au-H bonds indicating weak adsorption as the cluster grows. In most cases, the geometry of the lowest energy gold cluster remains planar even after the adsorption. In addition, the adsorbed molecule gets adjusted such that its center of mass lies on the plane of the gold cluster. Study of the orbital charge density of the gold adsorbed H2S molecule reveals that conduction is possible through molecular orbitals other than the lowest unoccupied molecular orbital level. The dissociation of the cationic Au(n)SH2+ cluster into Au(n)S+ and H2 is preferred over the dissociation into Au(m)SH2+ and Au(n-m), where n=2-8 and m=1-(n-1). H2S adsorbed clusters with odd number of gold atoms are more stable than neighboring even n clusters. 相似文献