全文获取类型
收费全文 | 457篇 |
免费 | 24篇 |
国内免费 | 9篇 |
专业分类
化学 | 315篇 |
晶体学 | 2篇 |
力学 | 13篇 |
数学 | 66篇 |
物理学 | 94篇 |
出版年
2020年 | 6篇 |
2018年 | 6篇 |
2016年 | 13篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 23篇 |
2012年 | 9篇 |
2011年 | 13篇 |
2010年 | 14篇 |
2009年 | 10篇 |
2008年 | 9篇 |
2007年 | 9篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 10篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 17篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 13篇 |
1972年 | 9篇 |
1971年 | 6篇 |
1970年 | 10篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 5篇 |
1966年 | 5篇 |
1965年 | 4篇 |
排序方式: 共有490条查询结果,搜索用时 15 毫秒
81.
K. I. Rezchikova O. P. Shitov V. A. Tartakovskii V. A. Shlyapochnikov 《Russian Chemical Bulletin》1981,30(6):1126-1129
Conclusions Based on the data of the vibrational spectra and quantum-chemical calculation, in its electronic structure the nitro group in sulfonium C-nitro ylides is closer to the nitro groups in nonionized nitro compounds than in their salts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1403–1406, June, 1981. 相似文献
82.
83.
S. V. Zaitsev A. A. Maksimov I. I. Tartakovskii 《Journal of Experimental and Theoretical Physics》2010,111(4):582-590
Two-magnon Raman scattering in dielectric, as well as superconducting, YBa2Cu3O6 + x single crystals with mobile oxygen content x = 0.2–0.7 and superconducting transition temperature T c = 0–74 K is studied in detail. Doping with oxygen in the range of x = 0.2–0.5 leads to two-magnon scattering peak broadening and a shift in the spectral position of the peak towards lower energies. The most significant qualitative changes in two-magnon scattering in YBa2Cu3O6 + x crystals are observed in a narrow oxygen concentration range near x = 0.7. This is explained by a considerable decrease in the correlation length ξAF of antiferromagnetic (AF) correlations upon an increase in the concentration of free carriers. For instance, doping is accompanied with a reduction of ξAF to values of several lattice constants a for x ≈ 0.7, a transition to the regime of short-range AF order, and local scattering of light from a small AF cluster with a size of 3 × 4 lattice constants. An increase in the free charge carrier concentration destroys the short-range AF order in a narrow range of the stoichiometry index near x = 0.7. Experimental data also indicate heterogeneity of cuprate planes at microscopic level, which leads to coexistence of superconducting and AF regions in YBa2Cu3O6 + x super-conducting crystals. 相似文献
84.
A workshop on high-resolution X-ray emission spectroscopy was held in conjunction with the joint NSLS/CFN 2006 Users' Meeting. With the availability of high-brightness X-ray sources, and the development of improved optics and detectors for high-resolution (millivolt to volt) X-ray detection, X-ray emission spectroscopy (XES) has become one of the more rapidly growing areas of condensed matter synchrotron science. Most of the applications to date have focused on using XES for problems in condensed matter physics. The goal of this workshop was to illustrate the potential of XES for addressing important questions in chemistry and biology. 相似文献
85.
86.
Dr. Amey Nimkar Dr. Sandeepan Maity Prof. Robert A Flowers II Prof. Shmaryahu Hoz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(44):10499-10504
The work described herein compares the effect of additives (HMPA, methanol, ethylene glycol, pinacol, N-methylethanolamine) on thermal and photochemical reactions of samarium diiodide (SmI2). In thermal reactions, additives that coordinate to SmI2 induce a significant increase in reaction rate. In photochemical reactions, the presence of an electronegative atom with a highly localized negative charge on the substrate leads to a rate deceleration. In order to benefit from the columbic interaction with the positively charged samarium cation, these substrates react preferentially by an inner sphere reduction mechanism. The addition of ligands prevents this close interaction causing rate retardation. Furthermore, studies demonstrate that excited state quenching of SmII by ethylene glycol and other additives indicate that it is unlikely to be the major cause for the observed rate retardation. This effect provides a simple diagnostic tool to distinguish between an inner and an outer sphere reduction mechanism. 相似文献
87.
Acid/Base‐Triggered Switching of Circularly Polarized Luminescence and Electronic Circular Dichroism in Organic and Organometallic Helicenes
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nidal Saleh Barry Moore II Monika Srebro Nicolas Vanthuyne Loïc Toupet J. A. Gareth Williams Christian Roussel Kirandeep K. Deol Gilles Muller Jochen Autschbach Jeanne Crassous 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1673-1681
Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene‐bipyridine proligand 1 a and in its “rollover” cycloplatinated derivative 2 a . Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum‐chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene‐bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge‐transfer‐type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation. 相似文献
88.
89.
Dr. J. Philipp Wagner David C. McDonald II Prof. Dr. Michael A. Duncan 《Angewandte Chemie (International ed. in English)》2018,57(18):5081-5085
The OH+ cation is a well‐known diatomic for which the triplet (3Σ?) ground state is 50.5 kcal mol?1 more stable than its corresponding singlet (1Δ) excited state. However, the singlet forms a strong donor–acceptor bond to argon with a bond energy of 66.4 kcal mol?1 at the CCSDT(Q)/CBS level, making the singlet ArOH+ cation 3.9 kcal mol?1 more stable than the lowest energy triplet complex. Both singlet and triplet isomers of this molecular ion were prepared in a cold molecular beam using different ion sources. Infrared photodissociation spectroscopy in combination with messenger atom tagging shows that the two spin isomers exhibit completely different spectral signatures. The ground state of ArOH+ is the predicted singlet with a covalent Ar?O bond. 相似文献
90.
Deborah C. Bebout James F. Bush II Elizabeth M. Shumann Julie A. Viehweg Margaret E. Kastner Damon A. Parrish Steven M. Baldwin 《Journal of chemical crystallography》2003,33(5-6):457-463
The dimeric mercurous ion has been encapsulated by a pair of the tetradentate tripodal nitrogen ligands tris[(2-(6-methylpyridyl))methyl]amine (TLA). The complex [Hg2(TLA)2](ClO4)2 (1) was isolated directly from an acetonitrile solution of Hg(ClO4)2 3H2O and TLA. Complex 1 crystallizes in the triclinic space group
with a = 10.537(2) Å, b = 10.751(2) Å, c = 10.907(2) Å, = 75.20(3), = 73.73(3), = 75.73(3), and Z = 1. The cation is located an inversion center. The Hg–Hg and Hg–Namine bond distances are 2.5469(8) and 2.297(6) Å, respectively, and the average Hg–Npyridyl bond length is 2.75(7) Å. Complex 1 was stable indefinitely in acetonitrile-d
3 solution, permitting detection of 13 and 22 Hz heteronuclear couplings between the Hg(I) ions and the methylene protons of the ligand. Comparisons with the structures and spectroscopic properties of related mercuric and mercurous complexes are made. 相似文献