全文获取类型
收费全文 | 46篇 |
免费 | 0篇 |
专业分类
化学 | 13篇 |
力学 | 2篇 |
数学 | 2篇 |
物理学 | 29篇 |
出版年
2021年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2009年 | 1篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有46条查询结果,搜索用时 29 毫秒
1.
2.
As a first step towards computing instanton-generated superpotentials in heterotic standard model vacua, we determine the Gromov–Witten invariants for a Calabi–Yau threefold with fundamental group π1(X)=Z3×Z3. We find that the curves fall into homology classes in H2(X,Z)=Z3⊕(Z3⊕Z3). The unexpected appearance of the finite torsion subgroup in the homology group complicates our analysis. However, we succeed in computing the complete genus-0 prepotential. Expanding it as a power series, the number of instantons in any integral homology class can be read off. This is the first explicit calculation of the Gromov–Witten invariants of homology classes with torsion. We find that some curve classes contain only a single instanton. This ensures that the contribution to the superpotential from each such instanton cannot cancel. 相似文献
3.
Stephan Müller David Scheidegger Carsten Haber Wilhelm Simon 《Journal of separation science》1991,14(3):174-177
Fused silica columns of 4.6 μm i.d. were coated with 3-sulfopropylsilane as a cation exchanger and 3-(2-aminoethyl-amino)-propylsilane as an anion exchanger. Fast separations of cations (< 25 seconds) and of anions (< 35 seconds) were obtained, using a potentiometric microelectrode as a detector. In proceeding towards smaller i.d.s, a mixture of alkali metal cations could be separated successfully in an uncoated fused silica capillary of 2.3 μm i.d. as a result of retention by the surface silanol groups at pH 9.4. 相似文献
4.
Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on
the LAO (control) and LCMO side of the substrate. Critical current, I
c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed
that while the control side showed a J
c of ∼ 2 × 106 A/cm2, the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J
c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of
J
c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection
length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length
has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection. 相似文献
5.
Study of magnetoresistance and conductance of bicrystal grain boundary in La0.67Ba0.33MnO3 thin film
La0.67Ba0.33MnO3 (LBMO) thin film is deposited on a 36.7°C SrTiO3 bicrystal substrate using laser ablation technique. A microbridge is created across bicrystal grain boundary and its characteristics
are compared with a microbridge on the LBMO film having no grain boundary. Presence of grain boundary exhibits substantial
magnetoresistance ratio (MRR) in the low field and low temperature region. Bicrystal grain boundary contribution in MRR disappears
at temperature T>175 K. At low temperature, I-V characteristic of the microbridge across bicrystal grain boundary is nonlinear. Analysis of temperature dependence of dynamic
conductance-voltage characteristics of the bicrystal grain boundary indicates that at low temperatures (T<175 K) carrier transport across the grain boundary in LBMO film is dominated by inelastic tunneling via pairs of manganese
atoms and tunneling through disordered oxides. At higher temperatures (T>175 K), magnetic scattering process is dominating. Decrease of bicrystal grain boundary contribution in magnetoresistance
with the increase in temperature is due to enhanced spin-flip scattering process. 相似文献
6.
R. Scheidegger 《Fresenius' Journal of Analytical Chemistry》1969,245(1-2):54-57
Zusammenfassung Ein Gerät wird beschrieben, das die vollautomatische Herstellung von Lösungen wählbarer Konzentrationen erlaubt. Hierbei wird eine elektrische Waage automatisch tariert, die Einwaage elektrisch analog umgerechnet und die erforderliche Lösungsmittelmenge über elektrische Teflonventile gravimetrisch zudosiert. Es lassen sich Genauigkeiten von besser als 1 erreichen.
Device for the automatic preparation of solutions
A device is described for the fully automatic preparation of solutions of selectable concentrations. An electric balance is automatically tared, the weighed-in quantity is electrically converted (analog conversion) and the solvent quantity required is gravimetrically fed in by means of electrical Teflon valves. Accuracies better than 1 can be achieved.相似文献
7.
Molar extinction coefficients of some carbohydrates viz. l-arabinose (C5H10O5), d-glucose (C6H12O6), d-mannose (C6H12O6), d-galactose (C6H12O6), d(-) fructose (C6H12O6) and maltose (C12H24O12) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a
narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter
polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying
within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well. 相似文献
8.
adrian e. Scheidegger 《International Journal of Mathematical Education in Science & Technology》2013,44(6):765-772
A new type of generalization of fundamental calculating operations is attempted. Instead of generalizing the nature of the elements upon which operations are acting, the nature of the operations themselves is changed. By iterating the step which leads from addition to multiplication, new types of operations are generated. Some of these operations are discussed briefly. 相似文献
9.
de Alwis SP 《Physical review D: Particles and fields》1992,46(12):5429-5438
10.