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371.
Jorma HölsäManu Lahtinen Mika Lastusaari Jussi ValkonenJussi Viljanen 《Journal of solid state chemistry》2002,165(1):48-55
The crystal structures of the tetragonal rare earth (RE) oxychlorides, REOCl (RE=La-Nd, Sm-Ho, and Y) were studied by X-ray powder diffraction measurements, Rietveld analyses, and bond valence calculations. The tetragonal structure (space group P4/nmm, No. 129, Z=2) is stable for all but Er-Lu oxychlorides, which possess a hexagonal structure. The tetragonal structure consists of alternating layers of (REO)nn+ complex cations and Xn− anions, where the rare earth is coordinated to four oxygens and four plus one chlorines in a monocapped tetragonal antiprism arrangement. The Rietveld analyses yielded a coherent series of structural parameters. Preferred orientation and microabsorption effects were found significant. The evolution of interatomic distances and bond angles indicated that the reason for the preferred structure changing from tetragonal to hexagonal is the strain in the chlorine layer. The bond valence parameter B for the RE-O bonds had to be recalculated due to the covalent nature of the (REO)nn+ unit. The results obtained with the new parameter confirmed the strains in the chlorine layer to be the cause for the phase transition. 相似文献
372.
P. K. Sazonov V. Yu. Stolyarenko G. A. Artamkina I. P. Beletskaya 《Russian Chemical Bulletin》2005,54(1):159-164
Nucleophilic substitution in β-chlorovinyl phenyl ketone with diaza-18-crown-6 ether resulting in displacement of the chlorine atom afforded N,N’-bis(3-oxo-3-phenylpropen-1-yl)-1,10-diaza-18-crown-6 ether. The ability of the latter to form complexes with a number of metal cations was studied. However, the complex formation occurs only with the rare-earth cations Ln3+ and Th4+. This fact was demonstrated by UV and 1H NMR spectroscopy of solutions, confirmed by isolations of glassy phases of composition L3M2(NO3)6 · nH2O (M = La, Y, n ≈ 4–7), and supported by IR spectra of these phases in KBr pellets. The formation of complexes with La3+ and Y3+ leads to an increase in fluorescence intensity of the ligand. The stability constants of the 1 : 1 complexes in methanol were evaluated by spectrophotometry. These constants increase with decreasing ionic radius of the cation.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 156–160, January, 2005. 相似文献
373.
Synthesis and Crystal Structure of Cs3Y7Se12 The oxidation of yttrium metal with selenium in the presence of CsCl (7 d, 700°C, evacuated silicia tubes) results in the formation of pale yellow, lath-shaped single crystals of Cs3Y7Se12. The crystal structure (orthorhombic, Pnnm, Z = 2, a = 1272.8(3), b = 2627.7(5), c = 413.32(8) pm) consists of edge- and vertex-connected [YSe6] octahedra forming a rocksalt-related network [Y7Se12]3?. One-dimensional infinite channels along [001], apt to take up extra cations, provide coordination numbers of 6 and 7 + 1, respectively, for two crystallographically different Cs+. 相似文献
374.
Ya.V Galadzhun Ya.M Kalychak A.P Pikul D Kaczorowski 《Journal of solid state chemistry》2004,177(1):17-25
A new compound Ce12Pt7In was synthesized and its crystal structure at 300 K has been determined from single crystal X-ray data. It is tetragonal, space group I4/mcm, Z=4, with the lattice parameters: a=12.102(1) Å and c=14.542(2) Å, wR2=0.1102, 842 F2 values, 33 variable parameters. The structure of Ce12Pt7In is a fully ordered ternary derivative of the Gd3Ga2-type. Isostructural compounds has been found to form with Pr (a=11.976(1) Å, c=14.478(2) Å), Nd (a=11.901(1) Å, c=14.471(2) Å), Gd (a=11.601(3) Å, c=14.472(4) Å), and Ho (a=11.369(1) Å, c=14.462(2) Å). Magnetic properties of Ce12Pt7In, Pr12Pt7In and Nd12Pt7In were studied down to 1.7 K. All three ternaries order magnetically at low temperatures with complex spin arrangements. The electrical resistivity of Ce12Pt7In and Nd12Pt7In is characteristic of rare-earth intermetallics. 相似文献
375.
Thermal decomposition of 4,4′-dipyridyl complexes of light rare-earth thiocyanates in air atmosphere
D. Czakis-Sulikowska J. Radwanska-Doczekalska M. Markiewicz 《Journal of Thermal Analysis and Calorimetry》1994,41(1):81-89
The thermal decompositions of Ln(NCS)3(4-dipy)2·5H2O were studied, whereLn=La, Pr, Nd, Sm, Eu and Y, and 4-dipy=4,4′-dipyridyl. The compounds are first dehydrated. During the thermal decomposition
of Ln(NCS)3(4-dipy)2, deamination takes place. The transient products decompose with the formation of Ln2O2SO4. The energies of activation for the first step of dehydration of the La, Pr, Nd, Sm and Eu complexes were determined.
Zusammenfassung Es wurde die thermische Zersetzung von Ln(NCS)3(4-dipy)2.5H2O mitLn=La, Pr, Nd, Sm, Eu, Y und 4-dipy=4,4′-Dipyridyl untersucht. Die Verbindungen werden zuerst dehydratiert. Bei der thermischen Zersetzung von Ln(NCS)3(4-dipy)2 findet eine Desaminierung statt. Die übergangsprodukte zersetzen sich unter Bildung von Ln2O2SO4. Die Aktivierungsenergie für den ersten Schritt der Dehydratation der La-, Pr-, Nd-, Sm- und Eu-Komplexe wurde ermittelt.相似文献
376.
本文对Judd-Ofelt光谱分析理论(J-O理论)的发展和应用进行了综述.J—O理论用于分析固体中的稀土离子的吸收、发射光谱,可计算它们的跃迁几率、谱线强度、能级寿命、发射截面等. 相似文献
377.
60年来稀土金属有机配合物化学取得重要发展. 辅助配体从环戊二烯基,五甲基环戊二烯基,茚基发展到各种非茂配体,如双酚,β-二亚胺,胍基,脒基等. 配合物的种类从简单的三茂稀土配合物发展到各种形式的二茂稀土配合物和单茂稀土配合物. 非茂配体的应用不仅拓展了稀土金属有机配合物的结构种类,还极大推动稀土金属有机配合物在高分子和有机合成中的应用. 稀土金属有机配合物可有效催化烯烃均聚与共聚,共轭双烯烃以及极性单体的选择性聚合. 稀土金属有机配合物还能催化氢化,氢胺化和膦氢化等重要有机反应. 本文对稀土金属有机配合物化学过去60年的发展进行综述. 相似文献
378.
上转换纳米发光材料(UCNPs)是一种能在长波长光激发下发出短波长光的发光材料.在较多的研究中UCNPs在980 nm红外光激发下,能发出不同颜色的可见光,可以显著提高信噪比,所以UCNPs在三维立体显示、上转换激光器、红外探测、防伪识别、生物检测等诸多领域都具有广阔的应用前景.从稀土上转换纳米发光材料的基质和稀土离子及其光学性能方面概述了近几年稀土上转换纳米发光材料的研究进展. 相似文献
379.
Markus Nentwig Dr. Simon D. Kloß Dr. Lukas Neudert Lucien Eisenburger Prof. Dr. Wolfgang Schnick Prof. Dr. Oliver Oeckler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(63):14382-14387
The lanthanum oxonitridophosphate La21P40O46N57 was synthesized by high-pressure metathesis from partially hydrolysed LiPN2 and LaCl3 at 750–950 °C and 7–9 GPa. The combination of transmission electron microscopy (TEM) and diffraction using microfocused synchrotron radiation revealed a monoclinic crystal structure (space group P21/n, a=14.042(4), b=7.084(3), c=41.404(10) Å, β=97.73(3)° and Z=2), which is characterized by loop-branched 21 member single chains of P(O,N)4 tetrahedra that extend along [2 0 1]. These chains are related to the loop-branched dreier single chains with dreier-ring loops in stillwellite (CeBSiO5). In La21P40O46N57, these chains are characterized by a complex long-periodic conformation and exhibit disorder that involves La/N and P split positions. This is an extraordinarily long periodicity with respect to branched single chains of tetrahedra. La21P40O46N57 constitutes the first rare-earth oxonitridophosphate exhibiting a chain structure. Single-crystal data are consistent with electron and powder X-ray diffraction. 相似文献
380.