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排序方式: 共有223条查询结果,搜索用时 31 毫秒
51.
Olga Yakubovich Galina Kiriukhina Anatoliy Volkov Olga Dimitrova 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(5):514-522
A novel phosphate, sodium zinc aluminium bis(phosphate), NaZnAl(PO4)2, was obtained under mild‐temperature hydrothermal conditions at 553 K. The crystal structure has been studied using single‐crystal X‐ray experimental data. The pseudo‐hexagonal phase NaZnAl(PO4)2 crystallizes in the monoclinic space group P21/c. Its unique crystal structure is based on a three‐dimensional (3D) framework built by Zn‐, Al‐ and P‐centred tetrahedra sharing vertices. Channels parallel to the [101] and [01] directions are limited by six‐ and eight‐membered windows, and incorporate Na atoms. The new compound is discussed as a member of the morphotropic series AMM′PO4, where A = Na, K, Rb or NH4, M = Cu, Ni, Co, Fe, Zn or Mg and M′ = Fe, Al or Ga. The title compound is the first Na representative within the series and is characterized by a 3D architecture of tetrahedra populated in an ordered manner by Zn2+, Al3+ and P5+ ions. 相似文献
52.
The nature of the ground state and the lowest triplet excited state of the [Rh(2)(1,3-diisocyanopropane)(4)](2+) ion have been investigated by the density functional theory. Two locally stable geometrical conformations are found on the potential energy surfaces of both the ground and excited states, corresponding to the eclipsed and twisted conformations, the eclipsed conformation being more stable and having the shorter Rh-Rh bond length. While the Rh-Rh distances of the two conformations differ by approximately 0.4 A, they shorten to the same value upon excitation ( approximately 3.1 A). The excited state originates from the d(z)()()2 (metal antibonding) to p(z)() (ligand-metal bonding) electronic transition. The Mayer Rh-Rh bond order increases from approximately 0.2 to more than 0.8 upon excitation, while the Rh-C(N) bond order shows a slight decrease. A topological bond path between the Rh atoms is found in both the ground and excited states, while the electron localization function (ELF) indicates weak Rh-Rh covalent bonding for the excited state only. 相似文献
53.
Aqueous room temperature metal-catalyzed living radical polymerization of vinyl chloride 总被引:1,自引:0,他引:1
Percec V Popov AV Ramirez-Castillo E Monteiro M Barboiu B Weichold O Asandei AD Mitchell CM 《Journal of the American Chemical Society》2002,124(18):4940-4941
This paper describes the room-temperature living radical polymerization (LRP) of vinyl chloride in H2O/THF in the presence of Cu0 or CuI salts as catalysts, tren or PEI as ligands, and iodoform as initiator. The disproportionation reaction 2CuI + L --> Cu0 + CuII(L) is the crucial step, as it continuously provides the active species for both the initiation (Cu0) and the reversible termination step (CuII). Mn was found to increase linearly with conversion and is in good agreement with Mth, with the Mw/Mn being approximately 1.5. 相似文献
54.
Hyunseok Shim Hong-Kun Lyu Bunyod Allabergenov Yuriy Garbovskiy Anatoliy Glushchenko 《Liquid crystals》2016,43(10):1390-1396
Through the ferroelectric nanoparticles of BaTiO3 (BTO) doping, the response time for the frequency modulation of the polymer-dispersed liquid crystal (PDLC) was improved. The BTO-doped PDLC cells were prepared by polymerisation induced phase separation (PIPS) process using UV light. The capacitance of the PDLC composites was measured with an impedance analyzer in the frequency range of 100 Hz–1 MHz at 1 V. The dynamic signal for the response time of the PDLC devices was monitored through a digital oscilloscope. The electro-optical properties of the PDLC were found to strongly depend on the doped BTO concentration. The BTO doping caused a large increase in the capacitance. The dielectric constants were drastically decreased in the samples with rather low BTO doping ratio at a high frequency. No outstanding difference in the rising time of the LC was observed in the BTO-doped PDLC device, but the falling time was significantly decreased from 0.334 to 0.094 s. The present results imply that the nanoparticle-doping technology could improve the electro-optical performance of the PDLC requiring fast response and frequency modulation, such as optical modulators and PDLC-hybrid electroluminescence device for flexible electronic devices. 相似文献
55.
We introduce two new fluorescent viscosity probes, SYBR Green (SG) and PicoGreen (PG), that we have studied over a broad range of viscosity and in collagen solutions. In water, both dyes have low quantum yields and excited state lifetimes, while in viscous solvents or in complex with DNA both parameters dramatically (300–1000-fold) increase. We show that in log-log scale the dependence of the dyes’ quantum yield vs. viscosity is linear, the slope of which is sensitive to temperature. Application of SG and PG, as a fluorescence-based broad dynamic range viscosity probes, to the life sciences is discussed. 相似文献
56.
Anatoliy A. Pogoruy Ramón M. Rodríguez-Dagnino 《Advances in Applied Clifford Algebras》2010,20(1):79-84
The aim of this work is to prove some basic properties of coquaternions and to find the zeros of polynomials involving coquaternionic
elements. We also provide some expansions of hyperholomorphic function on coquaternion algebra by using Fueter polynomials. 相似文献
57.
58.
Zaikina JV Mori T Kovnir K Teschner D Senyshyn A Schwarz U Grin Y Shevelkov AV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(42):12582-12589
The creation of thermoelectric materials for waste heat recovery and direct solar energy conversion is a challenge that forces the development of compounds that combine appreciable thermoelectric figure‐of‐merit with high thermal and chemical stability. Here we propose a new candidate for high‐temperature thermoelectric materials, the type‐III Si172?xPxTey cationic clathrate, in which the framework is composed of partially ordered silicon and phosphorus atoms, whereas tellurium atoms occupy guest positions. We show that the utmost stability of this clathrate (up to 1500 K) in air is ensured by the formation of a nanosized layer of phosphorus‐doped silica on the surface, which prevents further oxidation and degradation. As‐cast (non‐optimized) Si‐P‐Te clathrates display rather high values of the thermoelectric figure‐of‐merit (ZT=0.24–0.36) in the temperature range of 700–1100 K. These ZT values are comparable to the best values achieved for the properly doped transition‐metal‐oxide materials. The methods of the thermoelectric efficiency optimization are discussed. 相似文献
59.
We report a laser spectroscopy technique for detecting optical absorption in gases and micro-objects via linked thermal effects and by using a sharp mechanical resonance in a quartz crystal. The performance of this technique is studied using near-IR diode lasers and two gases, pure CO(2) and C(2)H(2) diluted in nitrogen. A 7.3 × 10(-8) cm(-1)W/(Hz)(1/2) noise equivalent sensitivity to absorption in gases is demonstrated. Based on experimental results, it was estimated that 10(-8) fractional absorption of optical radiation by a micro-object deposited on a thin transparent fiber can be detected. 相似文献
60.
Yaroslav O. Tokaychuk Yaroslav E. Filinchuk Anatoliy O. Fedorchuk Ivanna R. Mokra 《Journal of solid state chemistry》2006,179(5):1323-1329
New ternary intermetallic compounds Sm2Ga7−xGex (x=5.2-6.1) and Sm4Ga11−xGex (x=5.76-8.75) were synthesized and their crystal structures were determined by X-ray powder diffraction at compositions Sm2Ga1.8Ge5.2 and Sm4Ga5.24Ge5.76. Sm2Ga1.8Ge5.2 crystallizes with the Ce2(Ga0.1Ge0.9)7 type of structure (space group Cmce, Pearson code oS80-8.00, a=8.46216(13), b=8.15343(13), , Z=8), while Sm4Ga5.24Ge5.76 exhibits a new structure (space group Cmmm, Pearson code oS52-22.00, a=4.21038(4), b=35.8075(3), , Z=2). Both structures are the members of the linear intergrowth structure series built up from segments of BaAl4, AlB2 and α-Po structure types. Their Ga/Ge networks contain characteristic empty cubes with one side capped by an atom subjected to an intrinsic displacive disorder. A model of Ga/Ge localization was suggested on the basis of crystal-chemical analysis. 相似文献