全文获取类型
收费全文 | 121篇 |
免费 | 3篇 |
专业分类
化学 | 51篇 |
数学 | 1篇 |
物理学 | 72篇 |
出版年
2023年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2014年 | 1篇 |
2013年 | 17篇 |
2012年 | 9篇 |
2011年 | 5篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 15 毫秒
61.
Schlueter JA Park H Halder GJ Armand WR Dunmars C Chapman KW Manson JL Singleton J McDonald R Plonczak A Kang J Lee C Whangbo MH Lancaster T Steele AJ Franke I Wright JD Blundell SJ Pratt FL deGeorge J Turnbull MM Landee CP 《Inorganic chemistry》2012,51(4):2121-2129
The structural and magnetic properties of the newly crystallized CuX(2)(pyzO)(H(2)O)(2) (X = Cl, Br; pyzO = pyrazine-N,N'-dioxide) coordination polymers are reported. These isostructural compounds crystallize in the monoclinic space group C2/c with, at 150 K, a = 17.0515(7) ?, b = 5.5560(2) ?, c = 10.4254(5) ?, β = 115.400(2)°, and V = 892.21(7) ?(3) for X = Cl and a = 17.3457(8) ?, b = 5.6766(3) ?, c = 10.6979(5) ?, β = 115.593(2)°, and V = 950.01(8) ?(3) for X = Br. Their crystal structure is characterized by one-dimensional chains of Cu(2+) ions linked through bidentate pyzO ligands. These chains are joined together through OH···O hydrogen bonds between the water ligands and pyzO oxygen atoms and Cu-X···X-Cu contacts. Bulk magnetic susceptibility measurements at ambient pressure show a broad maximum at 7 (Cl) and 28 K (Br) that is indicative of short-range magnetic correlations. The dominant spin exchange is the Cu-X···X-Cu supersuperexchange because the magnetic orbital of the Cu(2+) ion is contained in the CuX(2)(H(2)O)(2) plane and the X···X contact distances are short. The magnetic data were fitted to a Heisenberg 1D uniform antiferromagnetic chain model with J(1D)/k(B) = -11.1(1) (Cl) and -45.9(1) K (Br). Magnetization saturates at fields of 16.1(3) (Cl) and 66.7(5) T (Br), from which J(1D) is determined to be -11.5(2) (Cl) and -46.4(5) K (Br). For the Br analog the pressure dependence of the magnetic susceptibility indicates a gradual increase in the magnitude of J(1D)/k(B) up to -51.2 K at 0.84 GPa, suggesting a shortening of the Br···Br contact distance under pressure. At higher pressure X-ray powder diffraction data indicates a structural phase transition at ~3.5 GPa. Muon-spin relaxation measurements indicate that CuCl(2)(pyzO)(H(2)O)(2) is magnetically ordered with T(N) = 1.06(1) K, while the signature for long-range magnetic order in CuBr(2)(pyzO)(H(2)O)(2) was much less definitive down to 0.26 K. The results for the CuX(2)(pyzO)(H(2)O)(2) complexes are compared to the related CuX(2)(pyrazine) materials. 相似文献
62.
The organic radical-ion salt DEOCC-TCNQF4 contains linear chains of stacked molecules with significant Heisenberg antiferromagnet interactions along the chain and extremely weak interactions between the chains. Zero-field muSR has confirmed the absence of long-range magnetic order down to 20 mK and field-dependent muSR is found to be consistent with diffusive motion of the spin excitations. The anisotropic spin dynamics and the upper boundary for magnetic ordering temperature both indicate interchain magnetic coupling /J'/<7 mK. As the intrachain coupling J is 110 K, /J'/J/ is significantly less than 10(-4). This system therefore provides one of the most ideal examples of the one-dimensional S=1/2 Heisenberg antiferromagnet yet discovered. 相似文献
63.
M. T. Chen C. -Y. E. Tong S. Paine R. Blundell 《International Journal of Infrared and Millimeter Waves》1997,18(9):1697-1711
We present measurements of the near-field beam profiles of two corrugated feed horns with center frequencies of 216 and 300
GHz. Both co-polar and cross-polar components of the electric field have been probed across the operation band of the horns.
A full-wave numerical near-field transformation, based on a vector Kirchhoff integral, is implemented to transform the measured
field to the horn aperture for a comparison with the ideal aperture field. From the overlap integral of the transformed and
the ideal field, we conclude that the field radiated by these horns is the HE11 mode, to a purity of better than 99%. 相似文献
64.
65.
66.
67.
68.
69.
70.
This paper contributes a new methodology called Waste And Source-matter ANalyses (WASAN) which supports a group in building agreeable actions for safely minimising avoidable waste. WASAN integrates influences from the Operational Research (OR) methodologies/philosophies of Problem Structuring Methods, Systems Thinking, simulation modelling and sensitivity analysis as well as industry approaches of Waste Management Hierarchy, Hazard Operability (HAZOP) Studies and As Low As Reasonably Practicable (ALARP). The paper shows how these influences are compiled into facilitative structures that support managers in developing recommendations on how to reduce avoidable waste production. WASAN is being designed as Health and Safety Executive Guidance on what constitutes good decision making practice for the companies that manage nuclear sites. In this paper we report and reflect on its use in two soft OR/problem structuring workshops conducted on radioactive waste in the nuclear industry. 相似文献