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81.
A DeWitt supermanifold always has the structure of a vector bundle over an ordinary spacetime manifold, whereas a Rogers supermanifold is not so restricted. Corresponding to the vector space fibers of the DeWitt supermanifold, a Rogers supermanifold has a foliation by submanifolds, or leaves, parametrized by soul coordinates only. We show that the universal covering space of any leaf always admits a flat metric. If the covering space is complete in this metric, it must in fact be a vector space. We combine this result with known theorems about foliations to give conditions under which a compact Rogers supermanifold with a single even dimension is necessarily a quotient space of flat superspace. We also show that a supermanifold defined by a polynomial equation in flat superspace is always of the DeWitt type. Finally, we exhibit new supermanifold structures forR
2 and the 2-torus which show that the foliation of a Rogers supermanifold can be quite exotic.Enrico Fermi Fellow. Research supported by the NSF: PHY 83-01221, and the Department of Energy: DE AC02-82-ER-40073 相似文献
82.
I. Rabin C. Jackschath W. Schulze F. W. Froben 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,19(4):401-404
Nonstoichiometric silver-halogen cluster compounds Ag n X m (0≤m≤n;X=F, Br) are generated by cocondensation of Ag atoms and AgX species using a slightly modified gas aggregation technique. The AgX molecules are produced by partial decomposition of SF6 and Br2 respectively at the surface of the hot silver containing crucible, followed by the reaction of halogen atoms with silver, giving rise to the formation of AgX molecules. In a heterogeneous nucleation between these molecules and evaporated Ag atoms the afore mentioned cluster compounds are formed. The degree of halogenation can either be controlled by the adjustment of the silver evaporation rate, or even more easily by controlling the partial pressure of the halogenating agent. The mass spectra of singly charged halogenated clusters, which are generated by electron impact ionization, reflect the stability of ions. These mass spectra demonstrate that there is an alternation in the intensity pattern up to a relatively high degree of halogenation (m) for each of the investigated compound series Ag n X m ,n≤8. This behavior is similar to the well-known odd-even effect for pure metal clusters, allowing us to postulate the existence of a “metallic” core which governs the stability of the cluster ion (at least for not too high degree of halogenation). 相似文献
83.
84.
Rabin Bera Nalivela Kumara Swamy G. Dhananjaya J. Moses Babu P. Rajender Kumar K. Mukkanti Manojit Pal 《Tetrahedron》2007,63(52):13018-13023
The first Pd/C-mediated Sonogashira coupling of β-chloroacroleins with terminal alkynes is described here. Pd/C–CuI–PPh3 was found to be an efficient catalyst system for this coupling reaction. Using this economic and general process a variety of 4-alkynyl-2H-chromene-3-carbaldehydes and 5-alkynyl-2,3-dihydro benzo[b]oxepine-4-carbaldehydes were prepared in good yields. 相似文献
85.
I. Rabin C. Jackschath W. Schulze 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,19(4):153-155
The mass spectra of silver- and gold-clusters, generated by a gas aggregation technique and ionized by electron impact, reveal anomalies in the relative abundance of both singly and multiply charged clusters. Concentration maxima for singly charged species Ag n + and Au n + (n=3, 9, 19, (21), 35) are in agreement with experimental data of Katakuse and the predictions from the electronic shell model. The observed anomalies in the abundance spectra of doubly charged silver and gold clusters as well as triply charged silver cluster ions are explained in terms of electronic shell closing. 相似文献
86.
87.
88.
When shear flow is generated in molecularly thin liquid films of simple liquids confined between two parallel plates, the effective viscosity of the liquid increases by many orders of magnitude compared to its bulk value. Non-Newtonian effects such as shear thinning with a universal power law exponent of
are observed in experiments and computer simulations. We present a simple model of these phenomena based on shear melting of solid-like layers induced by the strong coupling with the crystalline walls. 相似文献
89.
As part of an ongoing program to study the thermo-mechanical effects associated with cryopreservation via vitrification (vitreous
in Latin means glassy), the current study focuses on the development of a new device for mechanical testing of blood vessels
at cryogenic temperatures. This device is demonstrated on a bovine carotid artery model, permeated with the cryoprotectant
cocktail VS55 and a reference solution of 7.05M DMSO, below glass transition. Results are also presented for crystallized
specimens, in the absence of cryoprotectants. Results indicate that the elastic modulus of a specimen with no cryoprotectant,
at about −140°C (8.6 and 15.5°C below the glass transition temperature of 7.05M DMSO and VS55, respectively), is 1038.8 ± 25.2 MPa,
which is 8 and 3% higher than that of a vitrified specimen permeated with 7.05M DMSO and VS55, respectively. The elastic modulus
of a crystallized material at −50°C is lower by ∼20% lower from that at −140°C. 相似文献
90.