全文获取类型
收费全文 | 151篇 |
免费 | 22篇 |
国内免费 | 8篇 |
专业分类
化学 | 154篇 |
晶体学 | 1篇 |
物理学 | 26篇 |
出版年
2024年 | 1篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 12篇 |
2012年 | 6篇 |
2011年 | 11篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 11篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 11篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有181条查询结果,搜索用时 31 毫秒
1.
Z. S. Klemenkova B. V. Lokshin L. I. Strunkina M. Kh. Minacheva 《Russian Chemical Bulletin》1994,43(9):1516-1521
Raman and IR spectra (4000-50 cm–1) of solid cyclopentadienyl zirconium and hafnium hydrides Cp2MH2, Cp2MD2, Cp2Zr(H)X, and Cp2Zr(D)X (Cp = 5-C5H5; M = Zr, Hf; X = Cl, Br) have been studied. The vibrational modes of MH groups, Cp-rings, and metal-ligand bonds are discussed and the band assignments are proposed. In the solid state, these complexes form polymers with linear hydride bridges of the M-H-M type. The force constants of the M-H and M-Cp bonds increase on going from Zr to Hf.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1604–1609, September, 1994. 相似文献
2.
B. G. Bazarov R. F. Klevtsova A. D. Tsyrendorzhieva L. A. Glinaskaya Zh. G. Bazarova 《Journal of Structural Chemistry》2004,45(6):993-998
Physicochemical analysis (XRPA, DTA) was used to study phase equilibria in a ternary salt system Rb2MoO4-Fe2(MoO4)3-Hf(MoO4)2 in the subsolidus region. Ternary molybdates with compositions 5:1:3, 5:1:2, and 1:1:1 have been found and synthesized. Crystal and thermal characteristics have been determined. Single crystals of the ternary molybdate Rb5FeHf(MoO4)6 with a composition of 5:1:2 were grown. The crystal structure of the compound was solved using X-ray diffractometry (CAD-4 automatic diffractometer, MoK
α radiation, 1766 F(hkl), R = 0.0298). Hexagonal crystals with unit cell dimensions: a = b = 10.124(1) Å, c =15.135(3) Å, V = 1343.4(4) Å3, Z = 2, ρcalc = 4.008 g/cm3, space group P63. The mixed three-dimensional framework of the structure is formed from two sorts of MoO4 tetrahedra and Fe and Hf octahedra linked through their common O-vertices. Rubidium atoms of three varieties occupy the large voids of the framework.Original Russian Text Copyright © 2004 by B. G. Bazarov, R. F. Klevtsova, A. D. Tsyrendorzhieva, L. A. Glinaskaya, and Zh. G. Bazarova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1038–1043, November–December, 2004. 相似文献
3.
Synthesis and X-ray structural study of octa-coordinated hexafluoroacetylacetone hafnium(IV) complex
K. V. Zherikova N. B. Morozova I. A. Baidina V. I. Alekseev I. K. Igumenov 《Journal of Structural Chemistry》2006,47(1):82-86
Hexafluoroacetylacetonate hafnium(IV) complex has been synthesized and studied by X-ray structural analysis. Crystal data for C30H8F36Hf2O14 are: a = 12.957(3) Å, b = 16.687(3) Å, c = 12.398(3) Å, β = 108.97°, space group P21/c, Z = 2, d calc = 2.137 g/cm3, R = 0.047. The molecular structure is built from discrete binuclear molecules of Hf2(OH)2(hfac)6 composition; the Hf...Hf distance in dimer is 3.533 Å. The structural units are connected by van der Waals interactions in the crystal. 相似文献
4.
Marina Lulla Jelena Asari Jaan Aarik Kaupo Kukli Raul Rammula Unto Tapper Eero Kauppinen Väino Sammelselg 《Mikrochimica acta》2006,155(1-2):195-198
Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating
samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage
and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO2 films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed.
For comparison, Al2O3, Ta2O5 and TiO2 films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized
by atomic layer deposition method. 相似文献
5.
The triplet nature of rare long-lived states of d0 metallocenes formed upon ligand-to-metal energy transfer was confirmed by studies of triplet-triplet charge transfer in biscyclopentadienyl
complexes Cp2MCl2 (M = Zr (1), Hf (2)). The interaction between precatalysts and substrates of catalytic polymerization systems, viz., complexes 1 and 2 and unsaturated hydrocarbons (alkenes and dienes), was studied in the region of concentrations close to catalytic values.
For organometallic π-complexes, it has been shown for the first time that, in the case of the unsaturated hydrocarbons, the
efficiency of energy transfer obeys the Perrin equation. The process occurs at distances R
0 close to the diameter of the interacting molecules and is well described by the exchange-resonant mechanism of interaction.
In the case of the cyclopentadiene-Cp2MCl2 (M = Zr, Hf) systems, R
0 = 14.6 Å. A linear relationship between the critical radius of the quenching sphere R
0 and the number of carbon atoms in a linear α-olefin has been revealed for the first time and evidences the formation of a
π-complex between the precatalyst and substrate molecules.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–39, January, 2007. 相似文献
6.
B. G. Bazarov R. F. Klevtsova A. E. Sarapulova K. N. Fedorov L. A. Glinskaya Zh. G. Bazarova 《Journal of Structural Chemistry》2005,46(4):756-760
Single crystals of triple molybdate of composition 5:1:3 K5Pb0.5Hf1.5(MoO4)6 have been grown and their crystal structure has been solved from X-ray diffraction data (an automated diffractometer X8 APEX, MoK α -radiation, 2173 F(hkl), R = 0.0321). Trigonal unit cell parameters are: a = b = 10.739(2) Å, c = 37.933(9) Å; V = 3789(1) Å3, Z = 6, ρcalc = 4.014 g/cm3, space group \(R\bar 3\). Three-dimensional mixed framework of the structure is formed by two types of MoO4 tetrahedra and Pb and Hf octahedra linking via common O-vertices. Potassium atoms of three types occupy large vacancies in the framework. 相似文献
7.
Helmut G. Alt 《Russian Chemical Bulletin》1995,44(1):1-8
Ansa metallocene dichloride complexes of titanium, zirconium, and hafnium can be activated by methyl aluminoxane (MAO) to give excellent catalysts for the homogeneous polymerization of ethylene and propylene. The symmetry of the corresponding metaliocene dichloride complexes is essential for the stereospecific polymerization of propylene (isotactic, syndiotactic or atactic). The application of fluorenyl groups instead of cyclopentadienyl groups greatly increases the activity of the catalysts. The first ansa bis(fluorenyl) complexes of zirconium and hafnium, (C13H8-C2H4-C13Hs)MCl2 (M = Zr, Hf), have been prepared. It was found that after the activation by MAO the zirconium derivative demonstrates a very high activity. Several model complexes are presented in order to discuss the mechanism of the polymerization.This paper was presented at the INEOS-94 Workshop The Modern Problems of Organometallic Chemistry (Moscow, May 21–27, 1994).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 7–14, January, 1995. 相似文献
8.
Mit"kina T. V. Gerasko O. A. Sokolov M. N. Naumov D. Yu. Fedin V. P. 《Russian Chemical Bulletin》2004,53(1):80-85
Slow evaporation of hydrochloric acid solutions of zirconium(iv) or hafnium(iv) oxochlorides and cucurbituril in air afforded compounds with composition [M4(OH)8(H2O)16]Cl8·(C36H36N24O12)·16H2O, where M = Zr (1) or Hf (2). According to the X-ray diffraction data, complexes 1 and 2 are isostructural. Their crystal structures can be described as packings of polymer chains consisting of alternating cucurbituril molecules and tetranuclear cations [M4(OH)8(H2O)16]8+ linked to each other via an extensive network of hydrogen bonds. Compound 2 is the first structurally characterized tetranuclear hafnium aqua complex. 相似文献
9.
B. Gorski Nguyen Za Hung N. Ya Ljubman 《Isotopes in environmental and health studies》2013,49(3):275-282
Abstract Possibilities of using a new generation of sorbents have been investigated. Polymers of spatial-globular (spherulitic) structure (RGS polymers) have been tested to separate Cs, Sr and rare earth elements – which can also be radioactive contaminants – from different waters. RGS polymers are both, solids and highly-disperse systems being extremely permeable to fluids and gases with low pressure decline. They were currently used to clean industrial waste-water. It is shown that these polymers can be used successfully to separate radionuclides. Polymers RGS-81 and RGS-112 have high distribution coefficients for CS, Sr, Sc, the lanthanide series and Hf in weakly acid solutions. In HF solutions, Sc and Hf can be separated from Cs, Sr and the lanthanides. 相似文献
10.
Yu Zhang Dr. Novruz G. Akhmedov Prof. Jeffrey L. Petersen Prof. Carsten Milsmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3042-3052
Luminescent seven-coordinated zirconium and hafnium complexes bearing three mono-anionic 2,2′-pyridylpyrrolide ligands and one chloride were synthesized. Solid-state structures and the dynamic behaviors in solution were probed by X-ray crystallography and variable temperature 1H NMR experiments, respectively. Absorption spectroscopy and time-dependent density functional theory (TD-DFT) calculations supported a hybrid of ligand-to-metal charge transfer (LMCT)/ligand-to-ligand charge transfer (LLCT) for the visible light absorption band. The complexes (MePMPMe)3MCl (M=Zr, Hf, MePMPMe=3,5-dimethyl-2-(2-pyridyl)pyrrolide) are emissive in solution at room temperature upon irradiation with visible light due to a combination of phosphorescence and fluorescence characterized by excited state lifetimes in the μs and low to sub-ns timescale, respectively. Electrochemical experiments revealed that the zirconium complex possesses a reversible redox event under highly reducing condition (−2.29 V vs. Fc+/0). 相似文献