全文获取类型
收费全文 | 2412篇 |
免费 | 418篇 |
国内免费 | 370篇 |
专业分类
化学 | 1885篇 |
晶体学 | 25篇 |
力学 | 12篇 |
综合类 | 7篇 |
数学 | 40篇 |
物理学 | 1231篇 |
出版年
2024年 | 7篇 |
2023年 | 34篇 |
2022年 | 41篇 |
2021年 | 56篇 |
2020年 | 106篇 |
2019年 | 84篇 |
2018年 | 59篇 |
2017年 | 64篇 |
2016年 | 102篇 |
2015年 | 89篇 |
2014年 | 95篇 |
2013年 | 185篇 |
2012年 | 144篇 |
2011年 | 132篇 |
2010年 | 99篇 |
2009年 | 145篇 |
2008年 | 141篇 |
2007年 | 219篇 |
2006年 | 136篇 |
2005年 | 85篇 |
2004年 | 101篇 |
2003年 | 148篇 |
2002年 | 116篇 |
2001年 | 173篇 |
2000年 | 114篇 |
1999年 | 81篇 |
1998年 | 78篇 |
1997年 | 76篇 |
1996年 | 52篇 |
1995年 | 50篇 |
1994年 | 41篇 |
1993年 | 28篇 |
1992年 | 25篇 |
1991年 | 19篇 |
1990年 | 22篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有3200条查询结果,搜索用时 15 毫秒
241.
K. Ohno Y. Noguchi S. Ueda J. Onoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):137-140
Optimized three-dimensional (3D) cell structures and energy bands
of fused (peanut-shaped) C60 polymers (p55 and p66) have been
investigated using the first-principles pseudopotential approach
within the local density approximation of the density functional theory.
We found that the resulting electronic structure is either metal or
semiconductor depending on the shape of the polymer chains and
the unit cell structure. 相似文献
242.
E. Kasabova D. Alamanova M. Springborg V. G. Grigoryan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):425-431
The soft deposition of Ni13 and Cu13 clusters on Ni(111) and Cu(111) surfaces is studied by
means of constant-energy molecular-dynamics simulations.
The atomic interactions are described by the Embedded Atom Method.
It is shown that the shape of the nickel clusters deposited on Cu(111) surfaces remains rather intact,
while the copper clusters impacting on Ni(111) surfaces collapse forming double and triple layered
products. Furthermore, it is found that for an impact energy of 0.5 eV/atom the structures of all
investigated clusters show the lowest similarity to the original structures, except for the case of
nickel clusters deposited on a Cu(111) surface. Finally, it is demonstrated that when cluster and
substrate are of different materials, it is possible to control whether the deposition results in
largely intact clusters on the substrate or in a spreading of the clusters. This separation into
hard and soft clusters can be related to the relative cohesive energy of the crystalline materials. 相似文献
243.
L. Guo H.-S. Wu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):259-267
Geometries, electronic states and electron affinities of AlmAsn and AlmAs n (m+n=2–5) clusters have been examined using
four hybrid and pure density functional theory (DFT) methods. Structural
optimization and frequency analyses are performed using a 6-311+G(2df)
one-particle basis set. The geometries are fully optimized with each DFT
method independently. The three types of energy separations reported in this
work are the adiabatic electron affinity (EAad), the vertical electron
affinity (EAvert), and the vertical detachment energy (VDE). The
calculation results show that the singlet structures have higher symmetry
than that of doublet structures. The best functional for predicting
molecular structures was found to be BLYP, while other functionals generally
underestimated bond lengths. The largest adiabatic electron affinity,
vertical electron affinity and vertical detachment energy, obtained at the
6-311+G(2df)/BP86 level of theory, are 2.20, 2.04 and 2.27 eV (AlAs), 2.13,
1.94 and 2.38 eV (AlAs2), 2.44, 2.39 and 2.47 eV (Al2As), 2.09,
1.80 and 2.53 eV (Al2As2), 2.01, 1.57 and 2.36 eV (AlAs3),
2.32, 2.11 and 2.55 eV (Al2As3), 2.40, 1.45 and 3.26 eV
(AlAs4), 1.94, 1.90 and 2.07 eV (Al4As), respectively. However, the
BHLYP method gives the largest values for EAad and EAvert of
Al3As and EAad of Al3As2, respectively. For the
vibrational frequencies of the AlnAsm series, the B3LYP method
produces good predictions with the average error only about 10 cm-1 from available experimental and theoretical values. The other three functionals overestimate or underestimate the vibrational
frequencies, with the worst predictions given by the BHLYP method. 相似文献
244.
H. Jensen J. Kröger N. Néel R. Berndt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):465-469
Clusters on surfaces have been investigated with low-temperature scanning tunnelling microscopy and spectroscopy. Constant
current spectra acquired on Ag oligomers and one-dimensional chains on a Ag(111) reveal a
single resonance peak whose energy shifts towards the Fermi level with increasing cluster size. Next, controlled and reproducible
contact between a STM tip and a C60 molecule adsorbed on Cu(100) is reported. The
transition from tunnelling to contact is discussed in terms of local heating of the tip-molecule junction. 相似文献
245.
A. Tanaka R. Saito T. Kamikake M. Imamura H. Yasuda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):229-232
We have performed the optical and photoelectron
spectroscopic studies of alkyl-passivated Si nanoparticles synthesized by a
solution route. The alkyl-passivated Si nanoparticle with mean diameter less
than about 2 nm exhibits a strong ultraviolet-blue photoluminescence.
Furthermore, we have directly investigated their electronic structures in
the vicinity of Fermi level by means of valence-band photoemission
measurements using synchrotron radiation. From these results, the detailed
optical properties and electronic structures of alkyl-passivated Si
nanoparticles are discussed. 相似文献
246.
J. Moc 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):247-252
Five doublet isomers of the Al3H2 cluster lying
within a narrow range of 5 kcal/mol, along with the isomerization transition
states connecting them, have been located with the coupled-cluster CCSD(T)
and DFT methods. The two most stable doublet structures, the C2v planar
including the two Hs bound terminally and C1 non-planar showing one H
in terminal site and the other in threefold site are found to be essentially
degenerate. Although the reaction of Al3 with H2 to yield
Al3H2 is found to be significantly exothermic, by 23.5 kcal/mol,
this hydrogenation is impeded by a considerable kinetic barrier of 16 kcal/mol. Our result is consistent with the observed
lack of reactivity of
Aln towards H2(D2) for n=3 under thermal conditions [3].
The quartet Al3H2 isomers are predicted to lie 16–21 kcal/mol higher
in energy than the doublet analogues. Further dimerization of
Al3H2 to form Al6H4 has also been examined.
Electronic supplementary material Supplementary Online Material 相似文献
247.
J. Bansmann A. Kleibert F. Bulut M. Getzlaff P. Imperia C. Boeglin K.-H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):521-528
Mass-filtered cobalt clusters with a size of 8 nm have been deposited in-situ under soft-landing conditions onto Au(111).
The spin and orbital moments of the Co nanoparticles on a Au (111) single crystal have been investigated as a function of
the temperature using the element-specific method of X-ray magnetic circular dichroism in photoabsorption. The results hint
at an temperature-dependent spin-reorientation transition which is discussed with respect to different contribution to the
magnetic anisotropy. Furthermore, by means of an in-situ oxidation experiment, the influence of an exposure to oxygen on the
properties of the cobalt clusters has been investigated. 相似文献
248.
We present tight-binding molecular dynamics (TBMD) calculations on V, Nb and Ta nanoclusters with N = 15, 65, 175 and 369 atoms. We found that rhombic dodecahedra are energetically favoured over rhombic hexahedra and icosahedra, with V forming the most compact cluster with the gyration radius increasing with the cluster size. In addition, from the calculated electronic density of states we found that the cluster size plays an important role in the HOMO-LUMO gap and that an increase in cluster size results in enhancement of the electronic density around the Fermi level. Furthermore, we found that the small clusters (N = 15, 65) exhibit energy gap that persists even at 900 K. These findings originate from charge transfer occurring between the inner and outer cluster atoms; interestingly, we found that in the small N = 15, 65 clusters electronic charge accumulates at each surface site at the expense of the inner cluster atoms, while in the larger clusters, N = 175 and 369, charge is gathered on the central particles of the cluster, suggesting different sub-surface character of the clusters. These findings are in agreement with available experimental and theoretical data and promise to offer important information for creating nanostructured materials with improved properties suitable for multiple technological applications. 相似文献
249.
T.I. Gorbanyuk A.A. Evtukh V.G. Litovchenko V.S. Solntsev 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):211
The effect of hydrogen sulphide on the current–voltage characteristics of metal–insulator–semiconductor (MIS) structures based on nanoporous silicon (Sinanopor) under copper doping has been investigated. Scanning electron (SEM), atomic force (AFM) and optic microscopes and/or secondary ion mass spectroscopy (SIMS) were used to obtain detailed characterisation of copper cluster distribution present at the surface and pores, respectively. SIMS spectra reveal that finite gradient in copper distribution along the pores and oxidation of nanoporous silicon simultaneously can be obtained successfully under electroless deposition process. It was also shown that the doping of nanoporous silicon by Cu leads to enhanced hydrogen sulphide sensitivity of MIS structures even without catalytic active top electrodes (for example, Pd) at room temperature. Furthermore, for different types of familiar MIS structures based on nanoporous silicon, e.g., MIS structures doped or undoped by copper and by using Pd metal electrodes, the hydrogen sulphide detection at room temperature mainly depends on the modification in the height of barrier of hetero- (Al–Cu–Sinanopor–c-Si) or Schottky-like (Pd–Cu–Sinanopor–c-Si) structures resulting the chemical interaction of molecular H2S gas with copper clusters at the surface and in the pores. It is demonstrated that MIS structures based on the nanoporous silicon with copper doping are more sensitive to H2S action at room temperature. In addition, the physical mechanism explaining the observed phenomena is also discussed. 相似文献
250.
Zhao-Sha MengJun-Liang Liu Ji-Dong LengFu-Sheng Guo Ming-Liang Tong 《Polyhedron》2011,30(18):3095-3099
The reaction of a compartmentalized hydrazino Schiff base ligand with a MnII salt followed by a LnIII salt (Ln = Tb and Dy), afforded linear heterometallic MnLnMn complexes that showed interesting magnetic properties. 相似文献