全文获取类型
收费全文 | 114篇 |
免费 | 4篇 |
专业分类
化学 | 46篇 |
数学 | 7篇 |
物理学 | 65篇 |
出版年
2021年 | 3篇 |
2020年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2013年 | 4篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 1篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1929年 | 1篇 |
排序方式: 共有118条查询结果,搜索用时 15 毫秒
91.
Danneau R Klochan O Clarke WR Ho LH Micolich AP Simmons MY Hamilton AR Pepper M Ritchie DA 《Physical review letters》2008,100(1):016403
We study the anomalous conductance plateau around G=0.7(2e2/h) and the zero bias anomaly in ballistic hole quantum wires with respect to in-plane magnetic fields applied parallel B parallel and perpendicular B perpendicular to the quantum wire. As seen in electron quantum wires, the magnetic fields shift the 0.7 structure down to G=0.5(2e2/h) and simultaneously quench the zero bias anomaly. However, these effects are strongly dependent on the orientation of the magnetic field, owing to the highly anisotropic effective Landé g-factor g* in hole quantum wires. Our results highlight the fundamental role that spin plays in both the 0.7 structure and zero bias anomaly. 相似文献
92.
S. Cin D. D. Arnone H. P. Hughes D. Whittaker M. Pepper D. A. Ritchie 《Physica E: Low-dimensional Systems and Nanostructures》2000,6(1-4)
We show that the presence of InAs dots embedded in a host GaAs quantum well containing a two-dimensional electron gas dramatically modifies the cyclotron resonance (CR). Far-infrared CR measurements show two modes with different dispersions with applied magnetic field B. The lower-frequency mode, with a sub-linear dependence on B, is identified as a CR at low B, developing into a skipping orbit around the dot perimeters at higher B. This has not been previously observed for a system with randomly distributed scatterers. The higher-frequency mode is identified as a magnetoplasmon localised by the confining effect of the arrays of repulsive potentials due to the dots in the well. 相似文献
93.
The mixed ligand coordination compounds containing acesulfamato and N,N -diethylnicotinamide biomolecules of some rare earth metal cations (Eu3+, Tb3+, Ho3+, Er3+ and Yb3+) were synthesized, and their structural properties were investigated. Possible structural formulas have been proposed by determining the chemical composition of molecules (elemental analysis), binding properties (infrared spectroscopy, mass analysis, solid-state UV-vis spectroscopy), thermal degradation properties (TGA / DTA curves). Based on the data collected, it is suggested that rare earth metal cations with a 3+ oxidation state have sextet coordination. The geometries of the structures were thought to be distorted octahedral. The charge balance of the coordination sphere is balanced by a monoanionic acesulfamato located outside the coordination sphere. When the thermal behaviours of the complexes were examined, it was determined that the compounds with Eu3+, Tb3+, and Yb3+ metal cations contained one hydrate water outside the coordination sphere. Hydrate waters do not exist in the Ho3+ and Er3+ metal cation-centred complexes. At the end of the thermal decomposition analysis of all complex structures, it was determined that they leave the relevant metal oxides in the reaction vessels as final decomposition products. 相似文献
94.
David Charles Pepper 《Macromolecular rapid communications》1996,17(3):157-161
Recently rediscovered evidence supports the conclusion that the bimodality of molarmass distributions in polystyrenes initiated by HCIO4 is not, as widely believed, the consequence of independent chain-growth by different propagating species, but originates from lack of uniformity in reagent concentrations during the earliest stage of the polymerization, where the time-scale of the growth and decay of the transient ionic population is short compared with that of mixing, in conventional preparative experiments. 相似文献
95.
S. E. Pepper D. R. Peterman T. J. Tranter B. M. White 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):909-912
A cloud point extraction method followed by inductively coupled plasma-mass spectrometry (ICP-MS) has been developed for the
detection of trivalent lanthanides (Ln(III)) in aqueous samples. Ammonium pyrrolodinedithiocarbamate (APDC) was used as the
chelating ligand with 2 wt% Triton X-114 as the surfactant. Various experimental parameters were investigated and the extraction
efficiency, distribution ratios and concentration factors for the extraction of lanthanum (La), neodymium (Nd), europium (Eu)
and thulium (Tm) were determined. 相似文献
96.
Total Synthesis Establishes the Biosynthetic Pathway to the Naphterpin and Marinone Natural Products
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lauren A. M. Murray Dr. Shaun M. K. McKinnie Dr. Henry P. Pepper Reto Erni Dr. Zachary D. Miles Michelle C. Cruickshank Dr. Borja López‐Pérez Prof. Bradley S. Moore Dr. Jonathan H. George 《Angewandte Chemie (International ed. in English)》2018,57(34):11009-11014
The naphterpins and marinones are naphthoquinone meroterpenoids with an unusual aromatic oxidation pattern that is biosynthesized from 1,3,6,8‐tetrahydroxynaphthalene (THN). We propose that cryptic halogenation of THN derivatives by vanadium‐dependent chloroperoxidase (VCPO) enzymes is key to this biosynthetic pathway, despite the absence of chlorine in these natural products. This speculation inspired a total synthesis to mimic the naphterpin/marinone biosynthetic pathway. In validation of this biogenetic hypothesis, two VCPOs were discovered that interconvert several of the proposed biosynthetic intermediates. 相似文献
97.
Al-Cu-Fe thin films were prepared by laser induced arc (laser-arc) method from a single source-Al63Cu25Fe12 alloy, which was proved to consist of quasicrystalline phase together with approximant phase. The composition of the deposited films meets the requirement for formation of icosahedral symmetry phase. Quasicrystalline phase was obtained after annealing the amorphous as-deposit film samples. The optical properties of the samples were investigated. Thin film samples of Al, Cu and Fe deposited under the same condition were employed for comparison. The results showed specific reflective properties of Al-Cu-Fe quasicrystal thin film in some wavelength range. The optical conductivity of the films exhibited a negative peak, centered about 440 nm in range of 190to 800 nm. The Al-Cu-Fe quasicrystal thin films could absorb almost all the ray in the wavelength range from 420nm to 450 nm. The ratio of absorption was greater than 99%. 相似文献
98.
Stable suspensions of small metal Au, Ru, PI, Pd, Rh, Co and Nl particles dispersed in n-heptane and n-dodecane have been prepared using a novel two-phase system, Involving the formation of the particles In a methanolic phase and subsequent phase transfer of the panicles to the alkane medium. The dispersions consisted of small particles having diameters In the range of 8-30 nm (the gold sols were very polydlsperse having average diameters of ca.34 nm). The phase transfer of the particles and their subsequent colloid stability were effected by the presence of dissolved dispersant in the hydrocarbon phase (either Oloa 1200 or Hypermer LP 8). In the case of Oloa 1200, a widely-used polylsobutylene succinimide automotive engine dispersant, It Is proposed that the amlne groups adsorb strongly to the acidic surface o1 the particles, and the 70-carbon polyisobutylene chains extend Into the hydrocarbon medium sufficiently to maintain the separation of adjacent particles by steric and possibly also by electrical repulsion. 相似文献
99.
D. C. Pepper 《Macromolecular Symposia》1992,60(1):267-277
The lecture reviews recent studies on vinyl and vinylidene compounds, chiefly alkyl cyanoacrylates. It emphasizes the kinetics, especially the distinctive SINT (slow-initiation-no-termination) pattern, and the composite mechanism of initiation by tertiary amines. The need for corroboration of interpretations, clarification of ambiguities and extensions is emphasized. 相似文献
100.
Polymerization of styrene by HClO4 in CH2Cl2 at 0° at various [M]0/[HClO4]0 ratios has been studied. At low values of this ratio, the reaction is second order in HClO4 whereas it is first order at the values commonly used in kinetic studies. The rates are strongly increased by the addition of the salt benzyl trimethyl ammonium hexafluoroantimoniate, the effect being greater the lower the monomer concentration. Molecular weight distributions in the polymers formed under various conditions support the conclusion that at very low [M]0/[HClO4]0 ratios the polymerization is predominantly ionic in character, and the higher order in [HClO4]0 is anomalous. 相似文献