全文获取类型
收费全文 | 321篇 |
免费 | 9篇 |
国内免费 | 1篇 |
学科分类
数理化 | 331篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 5篇 |
2012年 | 16篇 |
2011年 | 21篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 13篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 15篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1969年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有331条查询结果,搜索用时 31 毫秒
41.
Sergeeva AP Averkiev BB Zhai HJ Boldyrev AI Wang LS 《The Journal of chemical physics》2011,134(22):224304
We have investigated the structural and electronic properties of the B(17)(-) and B(18)(-) clusters using photoelectron spectroscopy (PES) and ab initio calculations. The adiabatic electron detachment energies of B(17)(-) and B(18)(-) are measured to be 4.23 ± 0.02 and 3.53 ± 0.05 eV, respectively. Calculated electron detachment energies are compared with experimental data, confirming the presence of one planar C(2v) ((1)A(1)) isomer for B(17)(-) and two nearly isoenergetic quasi-planar C(3v) ((2)A(1)) and C(s) ((2)A') isomers for B(18)(-). The stability and planarity/quasi-planarity of B(17)(-) and B(18)(-) are ascribed to σ- and π-aromaticity. Chemical bonding analyses reveal that the nature of π-bonding in B(17)(-) and B(18)(-) is similar to that in the recently elucidated B(16)(2-) and B(19)(-) clusters, respectively. The planar B(17)(-) cluster can be considered as an all-boron analogue of naphthalene, whereas the π-bonding in the quasi-planar B(18)(-) is reminiscent of that in coronene. 相似文献
42.
Galeev TR Romanescu C Li WL Wang LS Boldyrev AI 《The Journal of chemical physics》2011,135(10):104301
The structures and the electronic properties of two aluminum-doped boron clusters, AlB(7)(-) and AlB(8)(-), were investigated using photoelectron spectroscopy and ab initio calculations. The photoelectron spectra of AlB(7)(-) and AlB(8)(-) are both broad, suggesting significant geometry changes between the ground states of the anions and the neutrals. Unbiased global minimum searches were carried out and the calculated vertical electron detachment energies were used to compare with the experimental data. We found that the Al atom does not simply replace a B atom in the parent B(8)(-) and B(9)(-) planar clusters in AlB(7)(-) and AlB(8)(-). Instead, the global minima of the two doped-clusters are of umbrella shapes, featuring an Al atom interacting ionically with a hexagonal and heptagonal pyramidal B(7) (C(6v)) and B(8) (C(7v)) fragment, respectively. These unique umbrella-type structures are understood on the basis of the special stability of the quasi-planar B(7)(3-) and planar B(8)(2-) molecular wheels derived from double aromaticity. 相似文献
43.
The potential energy surfaces of the Li(n)Si(4)(-) (n = 0-5) clusters were explored using the Kick Coalescence method. We found that, for those systems with n ≤ 2, the butterfly and parallelogram Si(4)(2-) kernels prevail as building blocks; however, when n ≥ 3, the Si(4)(4-) tetrahedral kernel, which is commonly found in heavier alkali monosilicides, MSi (M = Na, K, Rb, Cs), arises as the prevailing building block. In addition, by a natural population analysis (NPA) we found that the maximum charge transfer -4 from Li atoms to Si atoms is attained when n = 3. The addition of more Li atoms to the Si(4)(4-) system does not increase the charge transfer, but keeps it almost constant at the maximum value. We also calculated theoretical vertical electron detachment energies (VDEs) for low-lying isomers of the Li(n)Si(4)(-) (n = 0-4) clusters in order to facilitate their experimental identification. 相似文献
44.
V. N. Oraevsky G. E. Kocharov S. I. Boldyrev P. B. Dmitriev V. N. Ishkov V. P. Lazutkov G. A. Matveev Yu. N. Nitsora M. I. Savchenko D. V. Skorodumov Yu. E. Charikov 《Radiophysics and Quantum Electronics》1996,39(11-12):1015-1018
The first brief report on the results obtained in the IRIS experiment is presented. The IRIS instrument is an X-ray spectrometer based on proportional and scintillation counters designed for the measurement of solar X-ray radiation in the 2–200 keV range. Data on the 12 flares observed in March and April 1994 are reported, and examples of the flare radiation spectra are given. 相似文献
45.
L. E. Tsygankova V. I. Vigdorovich Ya. R. Kim V. I. Kichigin A. V. Boldyrev 《Russian Journal of Applied Chemistry》2005,78(12):1961-1969
The inhibitive power of AMDOR IK-7 formulation, homologous mixture of alkyl ammonium acetates C10–C14 in a specific solvent, and PKU-6 toward corrosion of St. 3 steel in weakly acid media containing 5.8 g l?1 NaCl, H2S, and CO2 was studied. The influence exerted by the inhibitors on the kinetics of partial electrode reactions and on the hydrogenation of steel was examined. Impedance spectra were recorded and analyzed. 相似文献
46.
The optical absorption spectra of single crystals of neodymium and samarium chromium borates are studied. A magnetic phase transition in NdCr3(BO3)4 (at T c = 8 ± 1 K) and SmCr3(BO3)4 (at T c = 5 ± 1 K) is observed. The effective magnetic field acting on the Nd3+ ion from the side of the ordered magnetic subsystem of chromium is estimated. 相似文献
47.
48.
49.
50.
Elliott BM Koyle E Boldyrev AI Wang XB Wang LS 《The journal of physical chemistry. A》2005,109(50):11560-11567
Gas-phase alkaline earth halide anions, MgX3(-) and CaX3(-) (X = Cl, Br), were produced using electrospray and investigated using photoelectron spectroscopy at 157 nm. Extremely high electron binding energies were observed for all species and their first vertical detachment energies were measured as 6.60 +/- 0.04 eV for MgCl3(-), 6.00 +/- 0.04 eV for MgBr3(-), 6.62 +/- 0.04 eV for CaCl3(-), and 6.10 +/- 0.04 eV for CaBr3(-). The high electron binding energies indicate these are very stable anions and they belong to a class of anions, called superhalogens. Theoretical calculations at several levels of theory were carried out on these species, as well as the analogous BeX3(-). Vertical detachment energy spectra were predicted to compare with the experimental observations, and good agreement was obtained for all species. The first adiabatic detachment energies were found to be substantially lower (by about 1 eV) than the corresponding vertical detachment energies for all the MX3(-) species, indicating extremely large geometry changes between MX3(-) and MX3. We found that all the MX3(-) anions possess D3h ((1)A1') structures and are extremely stable against dissociation into MX2 and X-. The corresponding neutral species MX3, however, were found to be only weakly bound with respect to dissociation toward MX2 + X. The global minimum structures of all the MX3 neutrals were found to be C2v ((2)B2), which can be described as (X2(-))(MX+) charge-transfer complexes, whereas the MX2...X (C2v, (2)B1) van der Waals complexes were shown to be low-lying isomers. 相似文献