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81.
Szilvia Gedey Ferenc Fülp Pirjo Vainiotalo Peter A. M. De Witte Istvían Zupk 《Journal of heterocyclic chemistry》2003,40(6):951-956
Five sets of 27‐membered combinatorial libraries of alicyclic β‐lactams were prepared via liquid‐phase Ugi 4‐center 3‐component reactions (U‐4C‐3CR) utilizing 3 different cis β‐amino acids, 3 different isonitriles and 5×3 sets of aldehydes. Through combinations of the building blocks of one of these libraries, all of the possible sublibraries were also generated. A few azetidinone derivatives were synthesized individually by parallel synthesis. 相似文献
82.
Kalevi Pihlaja Pentti Kuosmanen Pirjo Vainiotalo 《Journal of mass spectrometry : JMS》1988,23(11):770-776
The electron-impact-induced mass spectra of 1,3-dioxolane (la), 1,3-dithiolane (2a) and 1,3-oxatbiolane (3a) and their 2-methyl (1b–3b) and 2,2-dimethyl [(CH3)2: 1c–3c or (CD3)2: 1d–3d] derivatives have been studied in detail to gain further insight into their ion structures and competing reaction pathways with low-resolution, high-resolution, metastable and collision-induced dissociation (CID) techniques. For compounds 1a–1d the most significant reaction is loss of H˙ and CH3˙ by α-cleavage and a subsequent formation of CHO+ and C2H3O+ ions. The [M ? H]+ ions from 1a and 1b give a C2H3O+ ion which does not have the acyl cation structure as shown by their CID spectra. In compounds 3a–3d the sulphur-containing ions predominate, the C2H3O+ now having the acyl cation structure. 1,3-Dithiolanes (2a–2d) exhibit the most complicated fragmentation patterns. Furthermore the [M ? H]+ ion from 2a and [M ? CH3]+ ion from 2b have different structures as well as the [M ? H]+ ion from 2b and [M ? CH3]+ ion from 2c, as shown by their CID spectra. This can be utilized to explain why 3a–3c and 2a give principally a thiiranyl cation, whereas 2b gives a mixture of this and the thioacyl cation and 2c practically only the open-chain thioacetyl cation. 相似文献
83.
Cellulose nanofibrils—adsorption with poly(amideamine) epichlorohydrin studied by QCM-D and application as a paper strength additive 总被引:1,自引:0,他引:1
In this paper cellulose nanofibrils were used together with a cationic polylelectrolyte, poly(amideamine) epichlorohydrin
(PAE), to enhance the wet and the dry strength of paper. The adsorption of nanofibrils and PAE on cellulose model surfaces
was studied using quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM). The differences
in fibril and polyelectrolyte adding strategies onto cellulose fibres were studied by comparing layer-structures and nano-aggregates
formed by the nanofibrils and PAE. The results showed that when PAE was first adsorbed on the model fibre surface a uniform
and viscous layer of nanofibrils could be adsorbed. When PAE and nanofibrils were adsorbed as cationic aggregates a non-uniform
and more rigid layer was adsorbed. Paper sheets were prepared using both the bi-layer and nano-aggregate adding strategy of
the nanofibrils and PAE. When PAE and nanofibrils were adsorbed on pulp fibres as a bi-layer system significant increase in
both wet and dry tensile strength of paper could be achieved even at low added amounts of PAE. When the substances were added
as nano-aggregates the improvements in paper strength properties were not as significant. Bulk and surface nitrogen content
analyses of the paper samples showed that the adding strategy does not affect the total adsorbed amount of PAE but it has
a strong effect on distribution of substances in the paper matrix which has a crucial effect on paper wet and dry strength
development. 相似文献
84.
Monica Melegari Dr. Michele Suman Dr. Laura Pirondini Dr. Davide Moiani Dr. Chiara Massera Dr. Franco Ugozzoli Prof. Elina Kalenius Dr. Pirjo Vainiotalo Prof. Jean‐Christophe Mulatier Jean‐Pierre Dutasta Dr. Enrico Dalcanale Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(19):5699-5699
85.
An analytical procedure was developed for the simultaneous sensitive identification, screening and quantitation of 30 drugs of abuse using 250 microl of human oral fluid. The method employs sequential mixed-mode solid-phase extraction (SPE), optimized derivative formation and long-column fast gas chromatography/electron impact mass spectrometry (GC/EI-MS). After sequential SPE elution, the most sensitive and stable derivatives were formed by taking careful account of the characteristics of the active functional groups and possible steric hindrances affecting derivatization chemistry. Amphetamine-type stimulant drugs were acylated with heptafluorobutyric anhydride, benzodiazepines and Delta(9)-tetrahydrocannabinol were silylated with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide and benzoylecgonine, codeine, ethylmorphine, 6-monoacetylmorphine, morphine, pholcodine, buprenorphine and norbuprenorphine with N-methyl-N-(trimethylsilyl)trifluoroacetamide. In addition, the following analytes were included: methadone, cocaine, alprazolam, midazolam, fentanyl and zolpidem. In GC separation, fast temperature ramping and high carrier gas flow-rate combined with long 30 m columns of i.d. 0.32 mm offered a reduction in analysis time and sharp peak shapes while still maintaining sufficient resolution and high sample capacity. Validated parameters including selectivity, linearity, accuracy, intra- and inter-day precision, extraction efficiency and limit of quantitation were all within required limits. In contrast to previously published methods, this single procedure is suitable for the simultaneous toxicological determination of the most common illicit drugs and benzodiazepines, and also zolpidem, in a small amount of oral fluid. 相似文献
86.
87.
Paula Aulaskari Markku Ahlgrn Juha Rouvinen Pirjo Vainiotalo Esko Pohjala Jouko Vepslinen 《Journal of heterocyclic chemistry》1996,33(4):1345-1354
1-R-5-[(2-Nitro-2-phenyl)ethenyl]imidazoles (R = Bn, Me, H) 6a,b,c were synthesized by the Knoevenagel reaction of the corresponding aldehydes 4a,b,c with phenylnitromethane 5 . The E-isomers 6a,b,c were precipitated from the reaction mixture as crystalline compounds in 89, 81 and 60% yields, respectively. Traces of the Z-isomers 6a′b′,c′ were found in the reaction mixtures but could be obtained in a ratio of 4:3 from the E-form with UV irradiation. The E-forms were more stable and the Z-isomers changed again to the E-isomers in several weeks. 相似文献
88.
Pirjo Vainiotalo Tuula Partanen Ferenc Fülöp Gábor Bernáth Kalevi Pihlaja 《Journal of the American Society for Mass Spectrometry》1991,2(2):125-129
Six cyclohexene-fused 2-N-phenyliminoperhydro-3,1-oxazines and four related thiazines were prepared and their mass spectrometric behavior was studied by means of metastable ion analysis and exact mass measurement. In most of the fragmentations, extensive rearrangements took place. The decompositions through the retro-Diels-Alder reaction initiated by the double bond dominated in the case of the unsubstituted compounds. The effect of the double bond, however, was greatly outweighed by the effect of the substituent on the ring nitrogen atom. In comparison with the unsubstituted compounds, both electron-releasing (methyl) and electron-withdrawing (benzyl) substituents increased the contribution of the ring cleavage reactions in the heterocyclic part of the molecule; in the case of the benzyl group the loss of the substituent also became important. For isomeric compounds, the relative peak intensities were so different that such compounds were easy to differentiate. 相似文献
89.
Kantola AM Ahola S Vaara J Saunavaara J Jokisaari J 《Physical chemistry chemical physics : PCCP》2007,9(4):481-490
Deuterium Quadrupole Coupling Constant (DQCC) in benzene was determined both experimentally by Nuclear Magnetic Resonance spectroscopy in Liquid Crystalline solutions (LC NMR) and theoretically by ab initio electronic structure calculations. DQCCs were measured for benzene-d(1) and 1,3,5-benzene-d(3) using several different liquid crystalline solvents and taking vibrational and deformational corrections into account in the analysis of experimental dipolar couplings, used to determine the orientational order parameter of the dissolved benzene. The experimental DQCC results for the isotopomers benzene-d(1) and 1,3,5-benzene-d(3) are found to be 187.7 kHz and 187.3 kHz, respectively, which are essentially equal within the experimental accuracy (+/-0.4 kHz). Theoretical results were obtained at different C-D bond lengths, and by applying corrections for electron correlation and rovibrational motion on top of large-basis-set Hartree-Fock results. The computations give a consistent DQCC of ca. 189 kHz for three different isotopomers; benzene-d(1), 1,3,5-benzene-d(3), and benzene-d(6), revealing that isotope effects are not detectable within the present experimental accuracy. Calculations carried out using a continuum solvation model to account for intermolecular interaction effects result in very small changes as compared to the data obtained in vacuo. The comparison of theoretical and experimental results points out the selection of the underlying molecular geometry as the most likely source of the remaining discrepancy of less than 2 kHz. Such an agreement between the calculated and the experimental DQCC results can only be achieved if rovibrational effects are considered on one hand in the experimental direct dipolar coupling data, and on the other hand in the theoretical property calculation, as is done presently. 相似文献
90.
Kalenius E Kekäläinen T Neitola R Beyeh K Rissanen K Vainiotalo P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(17):5220-5228
The noncovalent complexation of tetraethyl and tetraphenyl resorcinarenes with mono-, di-, and oligosaccharides was studied with negative-polarization electrospray ionization quadrupole ion trap and electrospray ionization Fourier-transform ion cyclotron resonance mass-spectrometric analysis. The saccharides formed 1:1 complexes with deprotonated resorcinarenes, which exhibited clear size and structure selectivity in their complexation. In the case of the monosaccharides, hexoses formed much more abundant and kinetically stable complexes than pentoses or deoxyhexoses. A comparison of the mono-, di-, and oligosaccharides revealed that both the relative abundance and stability of the complexes increase up to biose and triose, but start to decrease after that point, as the length of the oligosaccharide is increased. This behavior was rationalized by comparing the lowest-energy conformations of the complexes formed between the resorcinarene and oligosaccharides. This comparison was achieved by using theoretical calculations and X-ray crystal studies. 相似文献