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排序方式: 共有177条查询结果,搜索用时 46 毫秒
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K. Bunzl W. Kracke E. P. Petrayev A. Ruchlja 《Journal of Radioanalytical and Nuclear Chemistry》1993,176(1):11-20
239+240Pu and-when possible-also the ratio238Pu/239+240Pu was determined in the lungs and livers of 15 residents from Chernobyl-fallout contaminated areas in Byelorussia. In several cases various sections of the lungs were analyzed separately. With the exception of one person the activity concentrations of239+240Pu, were always within the range expected from the global fallout of weapon tests in the sixties and did not indicate any contribution of Chernobyl-derived plutonium. 相似文献
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Ternary Halides of the A3MX6 Type. II. The System Ag3?xNaxYCl6: Synthesis, Structures, Ionic Conductivity . The influence of the substitution of Ag+ by Na+ ions on the crystal structure and the ionic conductivity of Ag3YCl6 (stuffed LiSbF6-type structure) has been investigated. The system Ag3?xNaxYCl6 forms a complete solid solution. The stuffed LiSbF6-type structure is stable for all compositions. For compounds with Na+ contents of x > 1.67, the cryolite-type structure is observed as the high-temperature form. The transition temperature decreases steadily with increasing Na+ content. The “end member” phase Na3YCl6 transforms at 243 K from the monoclinic cryolite-type structure to the stuffed LiSbF6-type structure (trigonal, R3 ; a = 697.3(1), c = 1 868.4(14) pm, Z = 3; R = 0.094; Rw = 0.069). The crystal structures of Ag1.3Na1.7YCl6 (trigonal, R3 ; a = 691.5(2), c = 1 853.7(6) pm, Z = 3; R = 0.099, Rw = 0.081) and AgNa2YCl6 (trigonal, R3 ; a = 691.7(1), c = 1 853.9(5) pm, Z = 3; R = 0.099, Rw = 0.064) have also been determined. Both chlorides crystallize like Ag3YCl6 and Na3YCl6-I in the stuffed LiSbF6-type structure. The monovalent cations, Ag+ and Na+, are distributed over the five octahedral voids that are occupied by the Ag+ ions alone in Ag3YCl6. The ionic conductivity for compounds within the solid solution Ag3?xNaxYCl6 decreases with increasing Na+ content. The values for Na3YCl6 (σ = 1 · 10?6 Ω?1 cm?1 at T = 500 K) are by 2.5 to 3.5 orders of magnitude smaller than those for Ag3YCl6 (σ = 6 · 10?4 Ω?1 cm?1 at T = 500 K). 相似文献
4.
Let k be a field and let Λ be an indecomposable finite dimensional k-algebra such that there is a stable equivalence of Morita type between Λ and a self-injective split basic Nakayama algebra over k. We show that every indecomposable finitely generated Λ-module V has a universal deformation ring and we describe explicitly as a quotient ring of a power series ring over k in finitely many variables. This result applies in particular to Brauer tree algebras, and hence to p-modular blocks of finite groups with cyclic defect groups. 相似文献
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Freia Ruegenberg Dr. Markus Seibald Dr. Dominik Baumann Dr. Simon Peschke Dr. Frauke Philipp Prof. Dr. Hubert Huppertz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(45):11701-11706
In order to expand the field of alkali lithosilicates, a new representative of the substance class with a previously unknown structure type was found based on solid-state synthesis. The novel compound with the sum formula Rb[Li5Si2O7] crystallizes in the orthorhombic space group Pbcm (no. 57) with a=7.6269(3), b=9.5415(4), and c=9.4095(3) Å by means of single-crystal X-ray diffraction. The structure consists of a highly condensed lithosilicate framework, built up of corner- and edge-linked [LiO4]-tetrahedra and [Si2O7]-units, and the rubidium ions aligned in channels. Suitable crystals of the material were obtained using sealed tantalum ampoules as reaction tube at a temperature of 750 °C. The new compound was further characterized via powder diffraction, Rietveld analysis, and EDX measurements. At first glance, Eu2+-doped Rb[Li5Si2O7] reveals an intense green luminescence. In-depth crystal analysis shows that a core-shell formation is present even for apparently high quality single-crystals. As a minority phase, the known green phosphor RbLi[Li3SiO4]2:Eu2+ is the origin of the luminescence, representing a tiny core inside of the particles surrounded by a large matrix of transparent Rb[Li5Si2O7] dominating the single-crystal diffraction pattern. 相似文献
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A novel nitridogallate fluoride LiBa5GaN3F5 – Synthesis,crystal structure,and band gap determination
LiBa5GaN3F5 was obtained as red crystals by reaction of Ba, Ga, NaN3 and EuF3 in a Na/Li flux at 760 °C in weld-shut tantalum crucibles. The crystal structure (Pnma (no. 62), a = 15.456(3), b = 5.707(1), c = 12.259(3) Å, Z = 4) was solved on the basis of single-crystal X-ray diffraction data. In the solid there are trigonal planar [GaN3]6? ions and zigzag chains of vertex sharing LiF6 octahedrons surrounded by Ba2+ ions. Optical measurements and calculations of the electronic structure revealed a band gap of ≤1.9 eV. According to the calculations, the observed transition occurs from a nitrogen state into a hybrid Ba/N state. 相似文献
9.
Winfried Sickel Frauke Sprengel 《Journal of Computational Analysis and Applications》1999,1(3):263-288
We investigate the order of convergence of periodic interpolation on sparse grids (blending interpolation) in the framework of tensor products of Nikol'skij–Besov spaces. To this end, we make use of the uniformity of the considered tensor norms and provide a unified approach to error estimates for the interpolation of univariate periodic functions from Nikol'skij–Besov spaces. 相似文献
10.
Frauke Schimmele Christiane Kaiser Susanne Pitsch Helmut Sitzmann 《Chemie in Unserer Zeit》2016,50(4):234-243
Reactions of the alkaline earth metals magnesium, calcium, strontium, and barium with water, phenolphthalein solution, diluted extract of red cabbage, diluted hydrochloric acid, or ammonia are well suited for a demonstration of the increase in reactivity within this group of metals with increasing atomic number. If the alkali metals lithium and sodium are included, the reactivity of six s‐block elements can be demonstrated in test tubes with small amounts of chemicals. 相似文献