全文获取类型
收费全文 | 115篇 |
免费 | 3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
41.
42.
43.
44.
Kataoka M Schneble RJ Thorn AL Barnes CH Ford CJ Anderson D Jones GA Farrer I Ritchie DA Pepper M 《Physical review letters》2007,98(4):046801
We use a pulse of surface acoustic waves (SAWs) to control the electron population and depopulation of a quantum dot. The barriers between the dot and reservoirs are set high to isolate the dot. Within a time scale of approximately 100 s the dot can be set to a nonequilibrium charge state, where an empty (occupied) level stays below (above) the Fermi energy. A pulse containing a fixed number of SAW periods is sent through the dot, controllably changing the potential, and hence the tunneling probability, to add (remove) an electron to (from) the dot. 相似文献
45.
46.
D.H. Cobden A.S. Dzurak M. Field C.G. Smith A.K. Savchenko M. Pepper D.A. Ritchie J.E.F. Frost G.A.C. Jones D.G. Hasko 《Physica A》1993,200(1-4):65-79
A brief review is presented on some of the consequences of single electron transport in GaAs structures. Particular topics considered include noise and fluctuations in the ballistic regime where the quantised conductance imposes a limit on the magnitude of the random telegraphic signals and the consequences of single traps changing occupancy can be clearly observed. Results are also presented on the non-invasive detection of the Coulomb blockade and factors determining transport in the conductance minima are discussed. Thermo-electric effects in the blockade regime are discussed as these are complementary to studies of electrical transport and show that the thermopower oscillates about zero with a period corresponding to the removal of a single electron. 相似文献
47.
We present a modified mathematical expression for the interfacial tension of very thin films. At large thicknesses the modified expression converges to the classic mathematical expression. We use this modified expression to derive an equation for the spreading coefficient as a function of film thickness. The spreading coefficient equation is then used to calculate the equilibrium thickness of a wetting liquid film for a "pancake drop". Our predictions agree with experimental data. The study is subjected to systems with van der Waals interactions only. 相似文献
48.
Melanie J. M. Pepper Isaiah Shavitt Paul Von Ragu Schleyer Mikhail N. Glukhovtsev Rudolf Janoschek Martin Quack 《Journal of computational chemistry》1995,16(2):207-225
Large basis set ab initio calculations at correlated levels, including MP2, single reference, as well as multireference configuration interaction, carried out on the methane potential energy surface, have located and characterized a transition structure for stereomutation (one imaginary frequency). This structure is best described as a pyramidal complex between singlet methylene and a side-on hydrogen molecule with Cs symmetry. At the single reference CI level, it lies 105 kcal/mol above the methane Td-ground state but is stable relative to dissociation into CH2(1A1) and H2 by 13 kcal/mol at 0 K (with harmonic zero point energy (ZPE) corrections for all structures). Dissociation of the transition state into triplet methylene and hydrogen also is endothermic (by 4 kcal/mol), but single bond rupture to give CH and H. is 3 kcal/mol exothermic. Thus, it does not appear likely that methane can undergo stereomutation classically beneath the dissociation limit. Confirming earlier conclusions, side-on insertion of 1A1 CH2 into H2 in a perpendicular geometry occurs without activation energy. Planar (D4h) methane (130.5 kcal/mol) has four imaginary frequencies. Two of these are degenerate and lead to equivalent planar C2v structures with one three-center, two-electron bond and two two-electron bonds and two imaginary frequencies. The remaining imaginary frequencies of the D4h form lead to tetrahedral (Td) and pyramidal (C4v) methane. The latter has three negative eigenvalues in the force-constant matrix; one of these leads to the Td global minimum and the other to the Cs (parallel) stereomutation transition structure. Multireference CI calculations with a large atomic natural orbitals basis set produce similar results, with the electronic energy of the Cs stereomutation transition state 0.7 ± 0.5 kcal/mol higher than that of CH + H. dissociation products, and a ZPE-corrected energy which is 5 ± 1 kcal/mol higher. Also considered are photochemical pathways for stereomutation and the possible effects of nuclear spin, inversion tunneling, and the parity-violating weak nuclear interaction on the possibility of an experimental detection of stereomutation in methane. © 1995 by John Wiley & Sons, Inc. 相似文献
49.
A method utilizing solvent extraction and analysis by gas chromatography-positive chemical ionization mass spectrometry (SE-GC-PCIMS) was developed for the analysis of three neutral hydrophobic perfluorooctanesulfonamide compounds [perfluorooctanesulfonamide (PFOSA), N-ethyl perfluorooctanesulfonamide (N-EtPFOSA), and N,N-diethyl perfluorooctanesulfonamide (N,N-Et2PFOSA)]. These compounds are suspected metabolic precursors of perfluorooctane sulfonate. The SE-GC-PCI-MS method was used to analyze all three perfluorooctanesulfonamides in fast food, fish, and Arctic marine mammal liver samples. The SE-GC-PCI-MS method produced relatively higher recoveries of the analytes (averaging 83 +/- 6%, 84 +/- 9%, and 89 +/- 19% for N,N-Et2PFOSA, N-EtPFOSA, and PFOSA, respectively) with lower coefficients of variation, and less susceptibility to matrix effects, than ion pair extraction-liquid chromatography-tandem mass spectrometric methods. Method detection limits (MDLs) were 100, 120, and 250 pg/g for N,N-Et2PFOSA, N-EtPFOSA, and PFOSA, respectively. The three compounds were found at concentrations ranging from below the MDL to 22 ng/g wet weight in fast food, fish, and Arctic marine mammal liver samples. 相似文献
50.
Sfigakis F Ford CJ Pepper M Kataoka M Ritchie DA Simmons MY 《Physical review letters》2008,100(2):026807
We investigate the conductance of quantum wires with a variable open quantum dot geometry, displaying an exceptionally strong Kondo effect and most of the 0.7 structure characteristics. Our results indicate that the 0.7 structure is not a manifestation of the singlet Kondo effect. However, specific similarities between our devices and many of the clean quantum wires reported in the literature suggest a weakly bound state is often present in real quantum wires. 相似文献