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111.
Antti O. Helminen Harri Korhonen Jukka V. Seppl 《Journal of polymer science. Part A, Polymer chemistry》2003,41(23):3788-3797
Resorbable poly(ester anhydride) networks based on ε‐caprolactone, L ‐lactide, and D,L ‐lactide oligomers were synthesized. The ring‐opening polymerization of the monomers yielded hydroxyl telechelic oligomers, which were end‐functionalized with succinic anhydride and reacted with methacrylic anhydride to yield dimethacrylated oligomers containing anhydride bonds. The degree of substitution, determined by 13C NMR, was over 85% for acid functionalization and over 90% for methacrylation. The crosslinking of the oligomers was carried out thermally with dibenzoyl peroxide at 120 °C, leading to polymer networks with glass‐transition temperatures about 10 °C higher than those of the constituent oligomers. In vitro degradation tests, in a phosphate buffer solution (pH 7.0) at 37 °C, revealed a rapid degradation of the networks. Crosslinked polymers based on lactides exhibited high water absorption and complete mass loss in 4 days. In ε‐caprolactone‐based networks, the length of the constituent oligomer determined the degradation: PCL5‐AH, formed from longer poly(ε‐caprolactone) (PCL) blocks, lost only 40% of its mass in 2 weeks, whereas PCL10‐AH, composed of shorter PCL blocks, completely degraded in 2 days. The degradation of PCL10‐AH showed characteristics of surface erosion, as the dimensions of the specimens decreased steadily and, according to Fourier transform infrared, labile anhydride bonds were still present after 90% mass loss. © 2003 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3788–3797, 2003 相似文献
112.
Katajisto J Karskela T Heinonen P Lönnberg H 《The Journal of organic chemistry》2002,67(23):7995-8001
Synthetic glycoclusters are extensively used as mimetics of naturally occurring, multivalent carbohydrate ligands in various glycobiological applications. Their preparation, however, is far from trivial, and it still is a limiting factor in the study of carbohydrate binding. We herein report the synthesis of an orthogonally protected building block, N-Alloc-N'-Boc-N' '-Fmoc-alpha,alpha-bis(aminomethyl)-beta-alanine (1), and its use in the preparation of triantennary peptide glycoclusters (21-24) on a solid support. The assembly of the clusters involves removal of the amino protections of the solid-supported branching unit 1 in the order Fmoc, Boc, and Alloc, and subsequent coupling of peracetylated O-(glycopyranosyl)-N-Fmoc-L-serine pentafluorophenyl esters (galactose, glucose, mannose, and ribose) to each amino group exposed. 相似文献
113.
The syntheses of five new aminoalkylbis(phenolate) ligands (as hydrochlorides) and their uranyl complexes are described. The reaction between uranyl nitrate hexahydrate and phenolic ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminopropane) · HCl], H2L1 · HCl, forms a uranyl complex [UO2(HL1)2] · 2CH3CN (1). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminobutane) · HCl], H2L2 · HCl, forms a uranyl complex with a formula [UO2(HL2)2] · 2CH3CN (2). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methyl benzyl)-1-aminohexane) · HCl], H2L3 · HCl, yields a uranyl complex with a formula [UO2(HL3)2] · 2CH3CN (3) and the ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-cyclohexylamine) · HCl], H2L4 · HCl, yields a uranyl complex with a formula [UO2(HL4)2] (4). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-benzylamine) · HCl], H2L5 · HCl, forms a uranyl complex with a formula [UO2(HL5)2] · 2MeOH (5). The molecular structures of 1, 2′ (2 without methanol), 3, 4 and 5 were verified by X-ray crystallography. The complexes 1–5 are neutral zwitterions which form in a molar ratio of 1:2 (U to L) in the presence of a base (triethylamine) and bear similar mononuclear, distorted octahedral uranyl structures with the four coordinating phenoxo ligands forming an equatorial plane and resulting in a centrosymmetric structure for the uranyl ion. In uranyl ion extraction studies from water to dichloromethane with ligands H2L1 · HCl–H2L5 · HCl, the ligands H2L2 · HCl and H2L4 · HCl are the most effective ones. 相似文献
114.
Kavakka JS Heikkinen S Kilpeläinen I Mattila M Lipsanen H Helaja J 《Chemical communications (Cambridge, England)》2007,(5):519-521
Pyrene mediated noncovalent attachment of a chlorophyll derivative, pyro-pheophorbide a, to a soluble single wall carbon nanotube is reported and the resultant CD, UV-Vis absorbance, fluorescence and 1H NMR spectra are discussed. 相似文献
115.
Krow GR Gandla D Guo W Centafont RA Lin G Debrosse C Sonnet PE Iii CW Ramjit HG Cannon KC 《The Journal of organic chemistry》2008,73(6):2122-2129
The ability of Selectfluor to act as a nucleofuge for hydrolysis of beta-anti-halides was investigated with N-alkoxycarbonyl derivatives of 6-anti-Y-7-anti-X-2-azabicyclo[2.2.1]heptanes and 4-anti-Y-8-anti-X-6-azabicyclo[3.2.1]octanes. The azabicycles contained X = I or Br groups in the methano bridge and Y = F, Br, Cl, or OH substituents in the larger bridge. The relative reactivities of the halides were a function of the azabicycle, the halide, and its bridge and the addition of Selectfluor or HgF(2) as a nucleofuge. All halide displacements occurred with retention of stereochemistry. Selectfluor with sodium bromide or sodium chloride, but not sodium iodide, competitively oxidized some haloalcohols to haloketones. A significant 15.6 Hz F...HO NMR coupling was observed with 4-anti-fluoro-8-anti-hydroxy-6-azabicyclo[3.2.1]octane. 相似文献
116.
Sami Valkama Olli Lehtonen Kristian Lappalainen Harri Kosonen Pascal Castro Timo Repo Mika Torkkeli Ritva Serimaa Gerrit ten Brinke Markku Leskel Olli Ikkala 《Macromolecular rapid communications》2003,24(9):556-560
Several alkyl side chains are bonded to each polymeric repeat unit using both coordinated ligands and electrostatically bound counterions to directly control the interface curvature of the self‐organized structures. 2,6‐Bis(octylaminomethyl)pyridine is Zn‐coordinated to poly(4‐vinylpyridine) (P4VP) with dodecylbenzenesulfonate (DBS) counterions, leading to multicomb polymeric supramolecules, poly[(4VP)Zn(2,6‐bis(octylaminomethyl)pyridine)(DBS)2]. Coordination is evidenced by infrared spectroscopy and visualized by quantum chemical calculations. The amorphous hexagonal self‐organized structures are characterized using X‐ray measurements.
117.
118.
Hydrophobicities of poly(ε-caprolactone) oligomers functionalized with different succinic anhydrides
Risto A. Hakala Harri Korhonen Susanna Holappa Jukka V. Seppälä 《European Polymer Journal》2009,45(2):557-564
Different succinic anhydrides were used for modification of hydrophobicities of linear and star-shaped poly (ε-caprolactone) oligomers with different molecular weights. Hydroxyl-terminated poly(ε-caprolactone) oligomers were acid-functionalized either with succinic anhydride (SAH) or with alkenylsuccinic anhydrides (ASAs) containing 8 or 18 carbons in their alkenyl chains. Hydrophobicities of the linear and corresponding star-shaped oligomers were investigated by immersion studies and by water contact angle measurements. In comparison with SAH functionalized oligomers, alkenyl chain containing oligomers showed lower thermal transitions and higher hydrophobicities. In addition, oligomers with 18 carbons alkenyl chain showed considerably higher hydrophobicities than corresponding oligomers with 8 carbon alkenyl chain. 相似文献
119.
Roy Pöllänen Harri Toivonen Kari Peräjärvi Tero Karhunen Petri Smolander Tarja Ilander Kimmo Rintala Tuure Katajainen Jarkko Niemelä Marko Juusela Timo Palos 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(2):433-437
The performance of an air sampler and a small gamma-ray spectrometer was tested in an unmanned aerial vehicle (UAV) able to carry payload with mass up to 0.5 kg. Operation of the sampler was investigated with the aid of radon progeny normally present in outdoor air. Detection limits for several transuranium nuclides in air are of the order of 0.3 Bq m?3 assuming 0.5 h sampling time and 1 h counting time in direct alpha spectrometry. Unshielded 137Cs and 60Co point sources at the ground level were used to test the CsI spectrometer. Detection limits are approximately 1 GBq or larger depending on the flying altitude. 相似文献
120.
Harri Koskela Outi Heikkil? Ilkka Kilpel?inen Sami Heikkinen 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,202(1):24-33
The finite RF power available on carbon channel in proton–carbon correlation experiments leads to non-uniform cross peak intensity response across carbon chemical shift range. Several classes of broadband pulses are available that alleviate this problem. Adiabatic pulses provide an excellent magnetization inversion over a large bandwidth, and very recently, novel phase-modulated pulses have been proposed that perform 90° and 180° magnetization rotations with good offset tolerance. Here, we present a study how these broadband pulses (adiabatic and phase-modulated) can improve quantitative application of the heteronuclear single quantum coherence (HSQC) experiment on high magnetic field strength NMR spectrometers. Theoretical and experimental examinations of the quantitative, offset-compensated, CPMG-adjusted HSQC (Q-OCCAHSQC) experiment are presented. The proposed experiment offers a formidable improvement to the offset performance; 13C offset-dependent standard deviation of the peak intensity was below 6% in range of ±20 kHz. This covers the carbon chemical shift range of 150 ppm, which contains the protonated carbons excluding the aldehydes, for 22.3 T NMR magnets. A demonstration of the quantitative analysis of a fasting blood plasma sample obtained from a healthy volunteer is given. 相似文献