全文获取类型
收费全文 | 99篇 |
免费 | 1篇 |
专业分类
化学 | 75篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 15篇 |
物理学 | 5篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 4篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 3篇 |
2007年 | 8篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1993年 | 1篇 |
1985年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有100条查询结果,搜索用时 0 毫秒
21.
Trinuclear mixed-metal gold-silver compounds are obtained by the reaction of gold(I) carbeniate [Au(mu-C(OEt)=NC6H4-p-CH3)]3, TR(carb), or gold(I) imidazolate [Au-mu-C,N-1-benzyl-2-imidazolate]3, TR(bzim), with silver(I) pyrazolate [Ag(mu-3,5-Ph2pz)]3. The crystalline products are mixed-ligand, mixed-metal dimeric products [Au(carb)Ag2(mu-3,5-Ph2pz)2], [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2, [Au(bzim)2Ag2(mu-3,5-Ph2pz)], and [Au2(bzim)2Ag(mu-3,5-Ph2pz)]. They have been characterized by elemental analysis and 1H NMR and mass spectrometry. The X-ray structure of [Au(carb)Ag2(mu-3,5-Ph2pz)2] shows it to be a dimer with two Ag...Au contacts between the trinuclear units of 3.083(2) and 3.310(2) A and with average intramolecular Ag...Ag and Au...Ag distances of approximately 3.3 and 3.2 A, respectively. The structure of [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 is a dimer with one intermolecular Au...Au attraction of 3.3354(10) A and a short Ag...Au distance of approximately 3.42 A and intramolecular Ag...Au and Au...Au contacts of approximately 3.2 and approximately 3.3 A, respectively. Packing diagrams of both complexes show that the dimeric units are independent, similar to their parent molecules. The dimers of trinuclear [Au(carb)Ag2(mu-3,5-Ph2pz)2] and [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 crystallize in the triclinic space group P (Z = 2), a = 9.688(3) A, b = 15.542(4) A, c = 23.689(6) A, alpha = 82.560(5) degrees , beta = 87.887(6) degrees , gamma = 78.060(5) degrees , and the orthorhombic space group Pca2(1) (Z = 4), a = 29.644(4) A, b = 7.4582(10) A, c = 30.473(4) A, respectively. The structure of [Au(bzim)Ag2(mu-3,5-Ph2pz)2] is a dimer with two metallophilic Ag...Au interactions of 3.14 A. The complex crystallizes in the monoclinic space group C2/c (Z = 4), a = 26.368(5) A, b = 15.672(3) A, c = 17.010(3) A, beta = 102.206(3) degrees . 相似文献
22.
Tatiana F. Pereira Marcelo F. Oliveira Izaque A. Maia Jorge V. L. Silva Marysilvia F. Costa Rossana M. S. M. Thiré 《Macromolecular Symposia》2012,319(1):64-73
Summary: Poly(3-hydroxybutyrate) (PHB) 3D porous cubes were successfully built with Selective Laser Sintering (SLS), one of the many existing 3D printing technologies. The resulting cubes presented shape and dimensions very close to the corresponding virtual model. Moreover, they were resistant to handling without presenting any visible damage. The PHB powder did not present variation in thermal properties and chemical composition after 32.15 hours of SLS process as observed by proton nuclear resonance (1H NMR) and differential scanning calorimetry (DSC) analysis, indicating that it can be re-utilized to print additional structures without affecting the reproducibility of the process. 相似文献
23.
Remote substituents that influence ground state state rotamer populations were found to be important controlling factors in the intramolecular Diels-Alder reaction with furan. 相似文献
24.
Fiorella Bachechi Alfredo Burini Rossana Galassi Bianca Rosa Pietroni 《Journal of Molecular Structure》2005,740(1-3):119-123
The Hg(II) complex [Hg(TFP)2(OTFP)3][ClO4]2 with TFP=tri-2-furyl-phosphine and OTFP=tri-2-furylphosphinoxide has been prepared and characterised. It crystallises in the hexagonal P63/m space group with Z=2, a=13.308(3), c=21.092 (4) Å, V=3235(1) Å3. The structure of the complex cation consists of independent molecules with Hg pentacoordinated in exact trigonal bipyramidal geometry. 相似文献
25.
Alicata R Barbuzzi T Giuffrida M Ballistreri A 《Rapid communications in mass spectrometry : RCM》2006,20(4):568-576
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) of narrowly dispersed molecular weight gel permeation chromatography (GPC) fractions was used to characterize random and microblock poly[(R)-3-hydroxybutyrate-co-epsilon-caprolactone] [P(HB-co-CL)] copolymers obtained via the acid-catalyzed transesterification of the corresponding homopolymers, poly([(R)-3-hydroxybutyrate] (PHB) and poly(epsilon-caprolactone) (PCL). High-quality mass spectra were obtained, which made it possible to establish the nature of the polymer end groups. Besides the carboxylic termination, two other moieties were found: alcoholic and tosyl end groups. MALDI mass spectra of CL-rich samples possessed mostly tosyl end groups, while HB-rich samples possessed mostly alcoholic end groups, showing that the tosyl moiety is linked prevalently to CL terminal units. The higher resolution of electrospray ionization (ESI) mass spectra of lower molecular weight GPC fractions permitted the identification of the different oligomer species hypothesized in the assignment of the corresponding MALDI mass spectra. Partial methanolysis of these copolymers was explored as a method of producing mixed HB-CL oligomers to be utilized as new synthons, possessing a minor number of chiral centers from those obtained from hydrolysis of biotechnologically synthesized poly(hydroxyalkanoates) (PHAs). 相似文献
26.
Mohamed AA Burini A Galassi R Paglialunga D Galan-Mascarós JR Dunbar KR Fackler JP 《Inorganic chemistry》2007,46(7):2348-2349
A chloride-centered hexanuclear copper(II) pyrazolate [Au(PPh3)2][trans-Cu6(micro-OH)6[micro-(3,5-CF3)2pz]6Cl] is isolated from the reaction of the trinuclear copper(I) pyrazolate [Cu3[micro-(CF3)2pz]3] with PPh3AuCl and Ph3P in moist air. The six copper atoms are bridged by pyrazolate and hydroxyl ligands, above and below the copper plane. The chloride anion exists at the center of the planar cavity formed by the copper atoms with Cu-Cl distances of 3.02-3.13 A. The magnetic susceptibility measurements show a strong antiferromagnetic coupling between the copper centers with an estimated exchange constant of J approximately 650 cm-1. 相似文献
27.
Emilio Scamporrino Placido Mineo Andrea Scamporrino Sandro Dattilo Daniele Vitalini Rossana Alicata 《Journal of polymer science. Part A, Polymer chemistry》2009,47(21):5682-5689
A totally aromatic polyether/sulfone resin (PES‐E) was synthesized and tested as an insulating glue in the construction of a Chip‐on‐Chip (CoC) device. PES‐E, essentially constituted of open‐chain macromolecules of low molecular mass (M n of about 3000 Da) with hydroxy and/or epoxy end‐groups, has a glass transition temperature of about 150 °C and is subject to crosslinking at temperatures higher than 320 °C. A CoC device was assembled using a five‐step process by interposing a layer of PES‐E between two chips. After curing, SEM cross section images showed a homogeneous crosslinked resin layer well stuck (flick and shear tests) to both chips. The chemical structure of the chains and the hydroxy/epoxy end‐groups ratio were optimized to obtain a crosslinked material with good adhesion and sufficient flexibility to avoid cracking during assembly and use. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5682–5689, 2009 相似文献
28.
Cardillo G Fabbroni S Gentilucci L Perciaccante R Piccinelli F Tolomelli A 《Organic letters》2005,7(4):533-536
The stereoselective anti SN2' attack of NaN3 to 3-alkenyl-3-bromo-azetidin-2-ones gave a mixture of diastereomeric azides in fast equilibrium. The [3,3]-sigmatropic rearrangement of allylic azides occurred with complete stereocontrol, allowing the equilibrium to be directed preferentially toward the (E)- or (Z)-isomer, useful precursors of 3(2'-amino)-beta-lactams. [reaction: see text] 相似文献
29.
Charruault L Michelet V Taras R Gladiali S Genêt JP 《Chemical communications (Cambridge, England)》2004,(7):850-851
This paper describes the asymmetric version of highly atom-economical alkoxycyclization of 1,6-enynes, using a combination of silver salts with the Pt(II)/(R)-Ph-BINEPINE system. 相似文献