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61.
5-Aminofurazano[3,4-d]pyrimidines carrying a variety of substituents at position 7 suffer ring cleavage by either acid or base to give 4-guanidino-3-furazancarboxylic acid (), the esters of which can be recyclised to give the pterin analog 5-amino-7(6H)-furazano[3,4-d]pyrimidinone (9). The pyrimidine ring of (9) is cleaved by hydrolysis, and the furazan ring by hydrogenolysis. 相似文献
62.
Aihara H Alston-Garnjost M Avery RE Barker AR Bauer DA Bay A Belcinski R Bingham HH Bloom ED Buchanan CD Caldwell DO Chao HY Chun SB Clark AR Cowan GD Crane DA Dahl OI Daoudi M Derby KA Eastman JJ Eberhard PH Edberg TK Eisner AM Erné FC Fairfield KH Fridman A Godfrey G Hauptman JM Ho C Hofmann W Kamae T Kenney RW Khacheryan S Kofler RR Lambert DJ Langeveld WG Layter JG Lin WT Linde FL Loken SC Lu A Lynch GR Lys JE Madaras RJ Magnuson BD Marsiske H Masek GE Mathis LG Maxfield SJ Miller ES 《Physical review D: Particles and fields》1991,43(1):29-33
63.
Domino Pd0‐Catalyzed C(sp3)–H Arylation/Electrocyclic Reactions via Benzazetidine Intermediates 下载免费PDF全文
Ronan Rocaboy Dr. David Dailler Florian Zellweger Dr. Markus Neuburger Dr. Christophe Salomé Dr. Eric Clot Prof. Dr. Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2018,57(37):12131-12135
The Pd0‐catalyzed C(sp3)‐H arylation of 2‐bromo‐N‐methylanilides leads to unstable benzazetidine intermediates that rearrange to benzoxazines through 4π electrocyclic ring‐opening and 6π electrocyclization. The introduction of a bulky, non‐activatable amide group on the nitrogen atom was key to favor the challenging reductive elimination step and disfavor undesired reaction pathways. 相似文献
64.
Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnett BA Bauer DA Bay A Bobbink GJ Buchanan CD Buijs A Caldwell DO Chao HY Chun SB Clark AR Cowan GD Crane DA Dahl OI Daoudi M Derby KA Eastman JJ Eberhard PH Edberg TK Eisner AM Erné FC Fairfield KH Hauptman JM Hofmann W Hylen J Kamae T Kaye HS Kenney RW Khacheryan S Kofler RR Langeveld WG Layter JG Lin WT Linde FL Loken SC Lu A Lynch GR Madaras RJ Magnuson BD Masek GE Mathis LG Matthews JA Maxfield SJ Miller ES Moses W 《Physical review letters》1990,64(2):172-175
65.
Debrauwer L Riu A Jouahri M Rathahao E Jouanin I Antignac JP Cariou R Le Bize B Zalko D 《Journal of chromatography. A》2005,1082(1):98-109
Atmospheric pressure photo ionisation has been evaluated for the analysis of brominated flame retardants and their related degradation products by LC-MS. Degradation mixtures obtained from the photochemical degradation of tetrabromobisphenol A and decabromodiphenylether were used as model systems for the assessment of the developed methodology. Negative ion mode gave best results for TBBPA and its degradation compounds. [M - H]- ions were formed without the need of using a doping agent. MS and MS/MS experiments allowed the structural identification of new TBBPA "polymeric" degradation compounds formed by attachment of TBBPA moieties and/or their respective cleavage products. In the case of polybromodiphenylethers, the positive mode provided M*+ ions and gave better results for congeners ranging from mono- to pentabromodiphenylethers whereas for higher bromination degrees, the negative ion mode (providing [M - Br + O]- ions) was best suited. Under both positive and negative ionisation modes, the use of toluene as doping agent gave better results. Liquid chromatography-mass spectrometry by means of atmospheric pressure photo-ionisation was applied to the analysis of aromatic brominated flame retardants and their degradation products. This methodology proved to be particularly useful, for the characterisation and structural identification of some compounds which are not amenable to GC-MS, especially in the case of apolar "polymeric" degradation products of tetrabromobisphenol A investigated in this work. 相似文献
66.
Ronan Le Lagadec Laura Rubio Rubén A. Toscano Rolandas Meškys Michel Pfeffer 《Journal of organometallic chemistry》2004,689(25):4820-4832
Cyclometalated derivatives of ring-substituted N,N-dimethylbenzylamines with controlled redox potentials as potent mediators of bioelectrochemical electron transport are reported. The cycloruthenation of R1R2R3C6H2CH2NMe2 (R1, R2, R3 = H, Me, tBuO, MeO, NMe2, F, CF3, CN, NO2) by [(η6-C6H6)RuCl(μ-Cl)]2 in the presence of NaOH/KPF6 in acetonitrile or pivalonitrile affords cyclometalated complexes [(η6-C6H6)Ru(C6HR1R2R3-o-CH2NMe2)(RCN)]PF6 [R = Me (1) and R = CMe3 (2)] in good yields. Reactions of complexes 1 and 2 with 2,2′-bipyridine (bpy) in acetonitrile or pivalonitrile result in dissociation of η6-bound benzene and the formation of [Ru(C6HR1R2R3-o-CH2NMe2)(bpy)(RCN)2]PF6 [R = Me (3) and R = CMe3 (4)]. All new compounds have been fully characterized by mass spectrometry, 1H/13C NMR, and IR spectroscopy. An X-ray crystal structural investigation of complex 1 (R1/R2/R3 = H/H/H) and two complexes of type 3 (R1/R2/R3 = MeO/H/H, MeO/MeO/H) has been performed. Acetonitrile ligands of 3 are mutually cis and the σ-bound carbon is trans to one of the bpy nitrogens. Measured by the cyclic voltammetry in MeOH as solvent, the redox potentials of complexes 3 for the RuII/III feature cover the range 320-720 mV (versus Ag/AgCl) and correlate linearly with the Hammett constants. Complexes 3 mediate efficiently the electron transport between the active site of PQQ-dependent glucose dehydrogenase (PQQ = pyrroloquinoline quinone) and a glassy carbon electrode. Determined by cyclic voltammetry the second order rate constant for the oxidation of the reduced (by d-glucose) enzyme active site by RuIII derivative of 3 (R1/R2/R3 = H) (generated electrochemically) is as high as 4.8 × 107 M−1 s−1 at 25 °C and pH 7. 相似文献
67.
Ronan Baron Biljana Šljukić Chris Salter Alison Crossley Richard G. Compton 《Electroanalysis》2007,19(10):1062-1068
The combinatorial screening of different metallic nanoparticles as electrocatalysts was investigated and efficiently applied for the detection of hydrazine. In a first step, glassy carbon microspheres decorated with metallic nanoparticles (Au, Pd, and Ag) were abrasively attached on the surface of a basal plane pyrolytic electrode giving a ‘multi–metal’ nanoarray. In a second step, electrodes modified with only one type of metallic nanoparticles allowed the identification of Pd as the unique catalytic material. In addition, a carbon‐epoxy composite electrode loaded with the Pd nanoparticles was then constructed for a practical use. The carbon‐epoxy composite nanoarray electrode was found to have excellent characteristics as for the sensing of hydrazine with a limit of detection of 2 μM. 相似文献
68.
Damien Jeannerat Dawn Ronan Yoann Baudry Andr Pinto Jean‐Paul Saulnier Stefan Matile 《Helvetica chimica acta》2004,87(9):2190-2207
The usefulness of computer‐assisted aliasing to secure maximal resolution of signal clusters in 1H‐ and 13C‐NMR spectra (which is essential for structure determination by HMBC 2D NMR spectroscopy) in minimal acquisition time is exemplified by the complete characterization of the two complementary p‐octiphenyls 1 and 2 with complex substitution patterns. The need for digital resolution near 1 Hz/pt to dissect the extensive signal clusters in the NMR spectra of these refined oligomers excluded structure determination under routine conditions. High resolution was secured by exploiting the low signal density in the 13C dimension of HMBC spectra by using computer‐assisted aliasing to maximize signal density. Based on the observed shifts in DEPT and 1H‐decoupled 13C‐NMR spectra of 1 and 2 , computer‐assisted aliasing allowed to reduce the number of required time increments by a factor of 20 to 30 compared to full‐width spectra with identical resolution. Without signal‐to‐noise constraints, this computer‐assisted aliasing reduced the acquisition time for high‐resolution NMR spectra needed for complete characterization of refined oligomers 1 and 2 by the same factor (e.g., from over a day to about an hour). With resolved signal clusters in fully aliased HSQC and HMBC spectra, unproblematic structure determination of 1 and 2 is demonstrated by unambiguous assignment of all C‐ and H‐atoms. These findings demonstrate that computer‐assisted aliasing of the underexploited 13C dimension makes extensive molecular complexity accessible by conventional multidimensional heteronuclear NMR experiments without extraordinary efforts. 相似文献
69.
New multiresidue analytical method dedicated to trace level measurement of brominated flame retardants in human biological matrices 总被引:1,自引:0,他引:1
Cariou R Antignac JP Marchand P Berrebi A Zalko D Andre F Le Bizec B 《Journal of chromatography. A》2005,1100(2):144-152
A new method has been developed for the multi-residue measurement of the main brominated flame retardants (alpha- and gamma-hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBP-A) and polybrominated diphenyl ethers including decabromodiphenyl ether) in human biological matrices (serum, adipose tissue and breast milk). The proposed sample preparation procedure focused on reduced solvent and consumable consumption and associated procedural contamination, as well as reduced sample size. This protocol was fully validated and was proved to be suitable for identification of brominated flame retardant residues at ultra-trace level, as attested by preliminary results on real samples. 相似文献
70.
Aurélie Jolivet Ronan Fablet Jean-François Bardeau Hélène de Pontual 《Analytical and bioanalytical chemistry》2013,405(14):4787-4798
The high spatial resolution analysis of the mineral and organic composition of otoliths using Raman micro-spectrometry involves rigorous protocols for sample preparation previously established for microchemistry and trace elements analyses. These protocols often include otolith embedding in chemically neutral resin (i.e., resins which do not contain, in detectable concentration, elements usually sought in the otoliths). Such embedding may however induce organic contamination. In this paper, Raman micro-spectrometry reveals the presence of organic contamination onto the surface obtained from the use of epoxy resin, specifically Araldite. This contamination level varies depending on otolith structures. Core and checks, known as structural discontinuities, exhibit the most important level of contaminations. Our results suggest that otolith embedding with resin affects the organic matrix of the otolith, probably through an infiltration of the resin in the crystalline structure. The interpretation of chemical otolith signatures, especially Raman otolith signatures, and stable isotope analyses should then be revised in light of these results. In this respect, we propose a method for the correction of Raman otolith signatures for contamination effects. 相似文献