全文获取类型
收费全文 | 234篇 |
免费 | 18篇 |
国内免费 | 20篇 |
专业分类
化学 | 137篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 29篇 |
物理学 | 101篇 |
出版年
2022年 | 1篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2013年 | 9篇 |
2012年 | 8篇 |
2011年 | 17篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2008年 | 19篇 |
2007年 | 15篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 21篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1965年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有272条查询结果,搜索用时 453 毫秒
61.
In the framework of density functional theory (DFT), the electronic excitations and nonlinear optical (NLO) properties of six binuclear transition metal cluster anions with the formula of [Ch2M-(μ-Ch)2-M'CN]^2- (M = Mo, W; Ch = S, Se; M' = Cu, Ag) have been systemically investigated at both cases of gas phase and DMF solution. The obtained electronic absorption spectra reveal that the element replacements of metals M and ligands Ch have significant influence on the absorptions, especially on the low-lying ones. In addition, the transitions of μ-Ch→M are dominant for the low-lying excitations, whereas the transitions of M'→M as well as Ch→M are mainly responsible for the higher excitations. The calculated molecular first and second hyperpolarizabilities present the remarkable element substitution and solvent effects. The analyses show that the transitions involving μ-Ch→M charge transfer make the critical contributions to the first hyperpolarizability t, and that the charge transfers from the moieties of MCh4 to M'CN as well as those of μ-Ch→M and M'→M are responsible for the second hyperpolarizability y. Moreover, the introduction of solvent leads to the results that the transitions within the moieties of MCh4 and M'CN make larger contributions to the hyperpolarizability, especially to γ. 相似文献
62.
Based on Car-Parrinello ab initio molecular dynamics simulations of the benzosemiquinone radical anion in both aqueous solution and the gas phase, density functional calculations provide the currently most refined EPR hyperfine coupling (HFC) tensors of semiquinone nuclei and solvent protons. For snapshots taken at regular intervals from the molecular dynamics trajectories, cluster models with different criteria for inclusion of water molecules and an additional continuum solvent model are used to analyse the HFCs. These models provide a detailed picture of the effects of dynamics and of different intermolecular interactions on the spin-density distribution and HFC tensors. Comparison with static calculations allows an assessment of the importance of dynamical effects, and of error compensation in static DFT calculations. Solvent proton HFCs depend characteristically on the position relative to the semiquinone radical anion. A point-dipolar model works well for in-plane hydrogen-bonded protons but deviates from the quantum chemical values for out-of-plane hydrogen bonding. 相似文献
63.
Reese CE Guerrero CD Weissman JM Lee K Asher SA 《Journal of colloid and interface science》2000,232(1):76-80
We have developed a series of emulsion polymerization recipes for the synthesis of highly charged, monodisperse polystyrene colloids of diameters between 100-400 nm. These spherical colloidal particles were crosslinked with divinyl benzene and functionalized with 1-allyloxy-2-hydroxypropane sulfonate. These highly charged, monodisperse colloidal particles readily self-assemble into robust three-dimensionally ordered crystalline colloidal arrays (CCAs). These CCAs operate as photonic crystals that Bragg diffract light in the ultraviolet, visible, and infrared regions of the spectrum. Copyright 2000 Academic Press. 相似文献
64.
Tom Otieno Jaime R. Blanton M. Jason Hatfield Sherry L. Asher Sean Parkin 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):m182-m185
The reaction of Cu(ClO4)2·6H2O, NaAsF6 and excess pyrazole yields hexakis(pyrazole‐κN2)copper(II) bis(hexafluoroarsenate), [Cu(C3H4N2)6](AsF6)2 or [Cu(pzH)6](AsF6)2 (pzH is pyrazole), (I). The analogous hexakis(pyrazole‐κN2)copper(II) hexafluorophosphate perchlorate complex, [Cu(C3H4N2)6](PF6)1.29(ClO4)0.71 or [Cu(pzH)6](PF6)1.29(ClO4)0.71, (II), is obtained in a similar fashion, using KPF6 in place of NaAsF6. Both compounds contain the hitherto unknown [Cu(pzH)6]2+ complex cation, in which the copper(II) ion lies at the center of a regular octahedron of coordinated N atoms. The cation has crystallographically imposed symmetry. The X‐ray data indicate that the lack of the expected distortion can be accounted for by the presence of either static Jahn–Teller disorder or dynamic Jahn–Teller distortion. 相似文献
65.
Retro Diels Alder fragmentation is highly stereospecific in the diones 1 under chemical ionization conditions, both with methane and isobutane as the reagent gases. Only the cis-isomers yield abundant protonated diene and quinone ions. The isotope effect indicates preferential protonation on a CO oxygen, and a subsequent H-migration prior to the formation of the protonated diene cations in the cis isomers. 相似文献
66.
Asher Peres 《Foundations of Physics》1985,15(2):201-205
Linear combinations of elements of reality, as defined by Einstein, Podolsky, and Rosen, may not be themselves elements of reality. There are questions which can be formulated (and unambiguously answered) in the ordinary language of experimental physics, but cannot be represented in the mathematical framework of quantum theory in a nontrivial way. 相似文献
67.
P. MORLIÉRE M. BAZIN L. DUBERTRET R. SANTUS T. SA E. MELO G. HÜPPE J. HAIGLE P. FORLOT A. BERNARD 《Photochemistry and photobiology》1991,53(1):13-19
5-Geranoxypsoralen, commonly called bergamottin, a major furocoumarin contained in bergamot oil, is reported in vitro as a highly photoreactive psoralen. In ethanol, it exhibits quite a high triplet state quantum yield (approximately 0.37). The triplet state is involved in subsequent photochemistry which depends on the initial concentration and on the presence of oxygen. In contrast to most psoralens, absorption and fluorescence data suggest that 5-geranoxypsoralen does not interact with DNA in the dark. No UVA-induced interstrand cross-links in DNA were shown. 相似文献
68.
Asher Peres 《International Journal of Theoretical Physics》1999,38(3):799-805
Errors in quantum computers are of two kinds:sudden perturbations to isolated qubits, and slow,random drifts of all the qubits. Isolated errors can becorrected by using quantum codewords that represent a logical qubit in a redundant way, by severalphysical qubits. On the other hand, slow drifts can bereduced, but not completely eliminated, by means ofsymmetrization, namely by using many replicas of the computer, and forcing their joint quantumstate to be completely symmetric. Several symmetrizationstrategies are examined and analyzed. 相似文献
69.
G. Asher Newsome Gary L. Glish 《Journal of the American Society for Mass Spectrometry》2009,20(6):1127-1131
A focused laser is used to make infrared multiphoton photodissociation (IRMPD) more efficient in a quadrupole ion trap mass
spectrometer. Efficient (up to 100%) dissociation at the standard operating pressure of 1 × 10−3 Torr can be achieved without any supplemental ion activation and with shorter irradiation times. The axial amplitudes of
trapped ion clouds are measured using laser tomography. Laser flux on the ion cloud is increased six times by focusing the
laser so that the beam waist approximates the ion cloud size. Unmodified peptide ions from 200 Da to 3 kDa are completely
dissociated in 2.5–10 ms at a bath gas pressure of 3.3 × 10−4 Torr and in 3–25 ms at 1.0 × 10−3 Torr. Sequential dissociation of product ions is increased by focusing the laser and by operating at an increased bath gas
pressure to minimize the size of the ion cloud. 相似文献
70.
The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo; X=S, O, Cl, Se, Br) makes contribution to the optical nonlinearity. It is possible to enhance the hyperpolarizability by substituting the ligands of the clusters. 相似文献