全文获取类型
收费全文 | 57篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学 | 25篇 |
数学 | 18篇 |
物理学 | 15篇 |
出版年
2022年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 1篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2003年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1972年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有58条查询结果,搜索用时 15 毫秒
1.
Using the concept of a twisted trace density on a cyclic groupoid, a trace is constructed on a formal deformation quantization of a symplectic orbifold. An algebraic index theorem for orbifolds follows as a consequence of a local Riemann-Roch theorem for such densities. In the case of a reduced orbifold, this proves a conjecture by Fedosov, Schulze, and Tarkhanov. Finally, it is shown how the Kawasaki index theorem for elliptic operators on orbifolds follows from this algebraic index theorem. 相似文献
2.
3.
Lei Ji Stefan Riese Alexander Schmiedel Marco Holzapfel Maximillian Fest Jrn Nitsch Basile F. E. Curchod Alexandra Friedrich Lin Wu Hamad H. Al Mamari Sebastian Hammer Jens Pflaum Mark A. Fox David J. Tozer Maik Finze Christoph Lambert Todd B. Marder 《Chemical science》2022,13(18):5205
Reversible conversion between excited-states plays an important role in many photophysical phenomena. Using 1-(pyren-2′-yl)-o-carborane as a model, we studied the photoinduced reversible charge-transfer (CT) process and the thermodynamic equilibrium between the locally-excited (LE) state and CT state, by combining steady state, time-resolved, and temperature-dependent fluorescence spectroscopy, fs- and ns-transient absorption, and DFT and LR-TDDFT calculations. Our results show that the energy gaps and energy barriers between the LE, CT, and a non-emissive ‘mixed’ state of 1-(pyren-2′-yl)-o-carborane are very small, and all three excited states are accessible at room temperature. The internal-conversion and reverse internal-conversion between LE and CT states are significantly faster than the radiative decay, and the two states have the same lifetimes and are in thermodynamic equilibrium.Reversible conversion between excited-states is key to many photophysical phenomena. We studied the equilibrium between LE and CT states by time-resolved and temperature-dependent fluorescence, fs- and ns-transient absorption, and LR-TDDFT calculations. 相似文献
4.
We define the “localized index” of longitudinal elliptic operators on Lie groupoids associated with Lie algebroid cohomology classes. We derive a topological expression for these numbers using the algebraic index theorem for Poisson manifolds on the dual of the Lie algebroid. Underlying the definition and computation of the localized index, is an action of the Hopf algebroid of jets around the unit space, and the characteristic map it induces on Lie algebroid cohomology. This map can be globalized to differentiable groupoid cohomology, giving a definition of the “global index”, that can be computed by localization. This correspondence between the “global” and “localized” index is given by the van Est map for Lie groupoids. 相似文献
5.
By using a sheaf-theoretical language, we introduce a notion of deformation quantization allowing not only for formal deformation parameters but also for real or complex ones as well. As a model for this approach to deformation quantization, we construct a quantization scheme for cotangent bundles of Riemannian manifolds. Here, we essentially use a complete symbol calculus for pseudodifferential operators on a Riemannian manifold. Depending on a scaling parameter, our quantization scheme corresponds to normally ordered, Weyl or antinormally ordered quantization. Finally, it is shown that our quantization scheme induces a family of pairwise isomorphic strongly closed star products on a cotangent bundle. 相似文献
6.
In this paper, we construct an explicit quasi-isomorphism to study the cyclic cohomology of a deformation quantization over a Riemannian étale groupoid. Such a quasi-isomorphism allows us to propose a general algebraic index problem for Riemannian étale groupoids. We discuss solutions to that index problem when the groupoid is proper or defined by a constant Dirac structure on a 3-dimensional torus. 相似文献
7.
Doubly charged lead clusters Pb72+, Pb92+, Pb112+ and Pb132+, far below the critical size for Coulomb explosion of par ticles with sphere like configurations (Pb30) have been detected in time of flight mass spectra. Their existence can be explained by chain-like clusters. 相似文献
8.
Vollmer A Jurchescu OD Arfaoui I Salzmann I Palstra TT Rudolf P Niemax J Pflaum J Rabe JP Koch N 《The European physical journal. E, Soft matter》2005,17(3):339-343
We use ultraviolet photoelectron spectroscopy to investigate the effect of oxygen and air exposure on the electronic structure of pentacene single crystals and thin films. It is found that O2 and water do not react noticeably with pentacene, whereas singlet oxygen/ozone readily oxidize the organic compound. Also, we obtain no evidence for considerable p-type doping of pentacene by O2 at low pressure. However, oxygen exposure lowers the hole injection barrier at the interface between Au and pentacene by 0.25 eV, presumably due to a modification of the Au surface properties. 相似文献
9.
The beam quality and output power of high power solid-state lasers is influenced by birefringence. Inhomogeneous distribution of the thermal field inside the laser crystal rod occurs due to non-uniform absorption of the pump light inside the crystal and a heat sink only at boundaries. Due to the photoelastic effect, this distribution leads to inhomogeneous thermal strains and birefringence inside the rod. Plane stress and plane strain assumptions for an axially symmetric pumped crystal have been used formerly for analytical models for calculating the birefringence. This model leads in case of an [111]-cut crystal to an axially symmetric birefringence pattern. However, the shear strains in the axial-radial plane are neglected in this former models using plane stress and plane strain assumptions. This shear strains are taken into account by full 3D numerical calculations. A threefold symmetry pattern due to the anisotropic behaviour of the photoelastic tensor, which is contradictory to the ideal use of a radial or azimuthal polarized beam, is shown by results of the birefringence simulation. A laser rod pumped at three sides with threefold symmetry is analysed in order to reduce the effect of birefringence. In this case the absorption is not axially symmetric anymore. Within the crystal in regions where pumping is stronger, the pump light absorption and consequently the temperature, the strains and birefringence are higher. The degree of three-fold symmetry of birefringence will be reduced, if the region having a low birefringence due to the photoelastic effect is more strongly pumped than the rest of domain. This means the birefringence is affected by the rotation of crystal around its [111]-axis. By an optimal rotation with respect to the edges of the crystal, smallest birefringence can be obtained. For generating radial or azimuthal polarizations, the output beam of this laser device is therefore more suitable. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.