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31.
The present research is aimed at monitoring the evolution of the volatile organic compounds of different samples of aceto balsamico tradizionale of modena (ABTM) during ageing. The flavouring compounds, headspace fraction, of the vinegars of four batterie were sampled by solid phase microextraction technique (SPME), and successively analysed by gas chromatography. Obtaining a data set characterized by different sources of variability such as, different producers, samples of different age and chromatographic profile. The gas chromatographic signals were processed by a three-way data analysis method (Tucker3), which allows an easy visualisation of the data by furnishing a distinct set of graphs for each source of variability. The obtained results indicate that the samples can be separated according to their age highlighting the chemical constituents, which play a major role for their differentiation. The present study represents an example of how the application of Tucker3 models, on gas chromatographic signals may help to follow the transformation processes of food products. 相似文献
32.
Alessandro Dolmella Giuliano BandoliClaudio Grandi 《Journal of Molecular Structure》2002,607(1):43-58
Muscarone analogues are compounds that have been proposed for the prevention or treatment of senile dementias. ARL-16607 (I), ARL-15467 (II), ARL-14995 (III) and YM-796 (IV) are spiromuscar-3-one derivatives and behave as muscarinic M1 agonists, with different binding selectivity and efficacy at the M1 receptors. In this work, we have elucidated the solid-state structures of I-III and compared the results obtained with the data available in the literature for IV.The solid-state arrangements of I-IV have then been used to input a series of theoretical calculations. For each molecule, eight conformations have been modeled and the obtained structures (1-32) have been submitted to a series of molecular dynamics/simulated annealing and molecular mechanics calculations aimed to explore the conformational freedom of the spiromuscar-3-one moiety. Some hints about the reactivity of I-IV have been obtained by performing Hartree-Fock, density functional theory and semiempirical quantum mechanics calculations. These studies analyzed the properties of the frontier orbitals and of the molecular electrostatic potential of I-IV.The information gained has been used to explain the better efficacy and poorer selectivity shown by III. Our results suggest that the behavior of III is due to its smaller size, the features of its molecular surface, the shape of its electrostatic potential and the orientation of its reactive domains. 相似文献
33.
Antonio?ArcelliEmail author Daniele?Balducci Alessandro?Grandi Gianni?Porzi Monica?Sandri Sergio?Sandri 《Monatshefte für Chemie / Chemical Monthly》2004,135(8):951-958
Summary. A series of chiral 1,4-morpholine-2,5-dione derivatives were synthesized. These substrates behave as non competitive inhibitors against -glucosidase showing a moderate inhibition (Ki< 0.8mM) and were found inactive towards -glucosidase. 相似文献
34.
J.C. de Lima T.O. Almeida A.R. Jerônimo S.M. Souza C.E.M. Campos T.A. Grandi 《Journal of Non》2006,352(2):109-115
The local atomic structure of an amorphous Cr25Nb75 alloy produced by mechanical alloying was determined using only one X-ray total structure factor S(K) as input data for reverse Monte Carlo simulations. The results showed that the amorphous alloy has a local atomic structure similar to that predicted by the additive hard sphere model for a Cr and Nb mixture with same composition of the alloy, and quite different of those found in the cubic and hexagonal Cr2Nb crystals. 相似文献
35.
K.?D.?MachadoEmail author J.?C.?de?Lima C.?E.?M.?Campos T.?A.?Grandi 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,37(4):421-424
We have investigated the local atomic structure of amorphous TM-Ti alloys (TM = Co, Ni, Cu) produced by Mechanical Alloying by means of EXAFS analyses on TM and Ti K-edges. Coordination numbers and interatomic distances for the three alloys where found and compared. EXAFS results obtained indicated a shortening in the unlike pairs TM-Ti as the difference between d electrons of TM and Ti atoms increases, suggesting an increase in the chemical short range order (CSRO) from TM = Co to Cu.Received: 12 October 2003, Published online: 9 April 2004PACS:
61.43.Dq Amorphous semiconductors, metals, and alloys - 61.10.Ht X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc. - 81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation 相似文献
36.
The performance obtainable with busy-channel multiple access (BCMA) techniques is analytically defined in the context of multichannel local radio networks. Network behavior is characterized in terms of throughput and transmission delay when a single radiofrequency channel is shared among many users, thought to be within the range of a central station, suitably located in the local area. The analytical model is based on a suitable Markov model for the generic terminal, and it is assumed that the traffic presented to the common channel conforms to a Poisson distribution. An analytical evaluation of throughput as a function of offered traffic and average transmission delay is presented. The numerical results obtained are for a particular case of BCMA, the well-known busy-tone multiple access (BTMA). In this example, the analytical model proposed allows fast performance evaluation and suitable comparison with CSMA and ALOHA protocol techniques and evaluation of the capture effect 相似文献
37.
The four stereoisomers of 3-isopropyl-5-methoxy-6-ketoheptanoic acid methylester and those of 2-methoxy-4-isopropylhexandioic acid methylester were synthesized from R(?)- and S(+)-carvone. The combined data given provide a basis for specific enantiomer assignment to natural product degradation materials. 相似文献
38.
On the basis of chemical evidence, the stereostructure 7 is proposed for ageratriol, a germacranic sesquiterpene isolated from Achillea ageratum L. 相似文献
39.
Jielin Zhang Eleonora Grandi Haigen Fu Thangavelu Saravanan Laura Bothof Pieter G. Tepper Andy‐Mark W. H. Thunnissen Gerrit J. Poelarends 《Angewandte Chemie (International ed. in English)》2020,59(1):429-435
Aspartic acid derivatives with branched N‐alkyl or N‐arylalkyl substituents are valuable precursors to artificial dipeptide sweeteners such as neotame and advantame. The development of a biocatalyst to synthesize these compounds in a single asymmetric step is an as yet unmet challenge. Reported here is an enantioselective biocatalytic synthesis of various difficult N‐substituted aspartic acids, including N‐(3,3‐dimethylbutyl)‐l ‐aspartic acid and N‐[3‐(3‐hydroxy‐4‐methoxyphenyl)propyl]‐l ‐aspartic acid, precursors to neotame and advantame, respectively, using an engineered variant of ethylenediamine‐N,N′‐disuccinic acid (EDDS) lyase from Chelativorans sp. BNC1. This engineered C–N lyase (mutant D290M/Y320M) displayed a remarkable 1140‐fold increase in activity for the selective hydroamination of fumarate compared to that of the wild‐type enzyme. These results present new opportunities to develop practical multienzymatic processes for the more sustainable and step‐economic synthesis of an important class of food additives. 相似文献
40.
We address a finite-plasticity model based on the symmetric tensor \(\varvec{P}^\top \! \varvec{P}\) instead of the classical plastic strain \(\varvec{P}\). Such a structure arises by assuming that the material behavior is invariant with respect to frame transformations of the intermediate configuration. The resulting variational model is lower dimensional, symmetric and based solely on the reference configuration. We discuss the existence of energetic solutions at the material-point level as well as the convergence of time discretizations. The linearization of the model for small deformations is ascertained via a rigorous evolution-\(\Gamma \)-convergence argument. The constitutive model is combined with the equilibrium system in Part II where we prove the existence of quasistatic evolutions and ascertain the linearization limit (Grandi and Stefanelli in 2016). 相似文献