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121.
The automatic recognition of the molecular content of a molecule''s graphical depiction is an extremely challenging problem that remains largely unsolved despite decades of research. Recent advances in neural machine translation enable the auto-encoding of molecular structures in a continuous vector space of fixed size (latent representation) with low reconstruction errors. In this paper, we present a fast and accurate model combining deep convolutional neural network learning from molecule depictions and a pre-trained decoder that translates the latent representation into the SMILES representation of the molecules. This combination allows us to precisely infer a molecular structure from an image. Our rigorous evaluation shows that Img2Mol is able to correctly translate up to 88% of the molecular depictions into their SMILES representation. A pretrained version of Img2Mol is made publicly available on GitHub for non-commercial users.The automatic recognition of the molecular content of a molecule''s graphical depiction is an extremely challenging problem that remains largely unsolved despite decades of research. 相似文献
122.
We study the regularity of the solutions u of a class of P.D.E., whose prototype is the prescribed Levi curvature equation in ℝ2
n
+1. It is a second-order quasilinear equation whose characteristic matrix is positive semidefinite and has vanishing determinant
at every point and for every function u∈C
2. If the Levi curvature never vanishes, we represent the operator ℒ associated with the Levi equation as a sum of squares
of non-linear vector fields which are linearly independent at every point. By using a freezing method we first study the regularity
properties of the solutions of a linear operator, which has the same structure as ℒ. Then we apply these results to the classical
solutions of the equation, and prove their C
∞ regularity.
Received: October 10, 1998; in final form: March 5, 1999?Published online: May 10, 2001 相似文献
123.
M. M. Britto Q. B. Cass I. C. S. F. Jardim C. A. Montanari H. Y. Aboul-Enein 《Chromatographia》2001,53(1-2):11-16
Summary The partition coefficients, logP
app
RPLC, for a series of propranolol analogues have been determined by reversed phase high performance liquid chromatography. The
hydrochloride salts and free base logP
app
RPLC show that charged and uncharged species can partition into the reversed phase. An extrathermodynamic relationship was found
for logP
app
RPLC measured in two different column stationary phases, C8 and PMOS, suggesting that the same set of compounds experience a similar
trend in these elution systems. The importance of using phosphate and/or MOPS buffer is due to the fact that the latter can
avoid ion-pairing partitioning, but the former does play the same role for PMOS column when the free base is considered. 相似文献
124.
In this article we discuss several aspects of the stochastic dynamics of spin models. The paper has two independent parts. Firstly, we explore a few properties of the multi-point correlations and responses of generic systems evolving in equilibrium with a thermal bath. We propose a fluctuation principle that allows us to derive fluctuation–dissipation relations for many-time correlations and linear responses. We also speculate on how these features will be modified in systems evolving slowly out of equilibrium, such as finite-dimensional or dilute spin-glasses. Secondly, we present a formalism that allows one to derive a series of approximated equations that determine the dynamics of disordered spin models on random (hyper) graphs. 相似文献
125.
Carlo Corvaja Lorenzo Franco Luigi Pasimeni Antonio Toffoletti Luciano Montanari 《Chemical physics letters》1993,210(4-6):355-361
The EPR spectrum of a free trapped in single crystals of chloranil changes its phase from absorption to emission when the crystal is illuminated by visible light. The time evolution of the EPR signal is discussed in terms of the interaction between the doublet species and triplet excitons produced by light excitation. 相似文献
126.
Two n-heptane-precipitated asphaltene samples, characterized by elemental analysis and nuclear magnetic resonance spectrometry, were fractionated according to relative molecular size by gel permeation chromatography (GPC). Both the whole asphaltene samples and their fractions were analysed by pyrolysis/gas chromatography/mass spectrometry. The data obtained from the pyrograms (average side-chain length, aromaticity index, sulphur compounds vs. aliphatic compounds, presence of SO2 and CO2) demonstrated that, in the case of asphaltenes, GPC fractionation results in the separation of different chemical structures ranging from lower molecular mass, highly aromatic and polar compounds to higher molecular mass, less polar and aromatic compounds. 相似文献
127.
A novel fluorous capping reagent is introduced to facilitate purification during solid-phase peptide synthesis (SPPS). Reagent 1 is a trivalent iodonium salt that reacts vigorously with free amines to deliver a long-chain fluoroalkyl group. It has been used to tag all unreacted amines following the peptide coupling step in SPPS. The resulting fluoroalkylated amine is no longer able to couple in further peptide coupling steps and is also stable to standard peptide synthesis conditions. Deletion products are removed using flash fluorous chromatography to yield the pure, full-length peptide. 相似文献
128.
Rita Annunziata Mauro Cinquini Franco Cozzi Fernando Montanari Angelo Restelli 《Tetrahedron》1984,40(19):3815-3822
The aldol-type condensation of enantiomerically pure α-sulphinylacetamides is described. The stereochemical outcome of the reaction mainly depends on the nature of the base used to generate the enolate. Experimental evidences allow the identification of preferred reaction paths. 相似文献
129.
Salla I Montanari T Salagre P Cesteros Y Busca G 《Physical chemistry chemical physics : PCCP》2005,7(12):2526-2533
The low temperature adsorption of CO and the room temperature adsorption of propionitrile and ortho-toluonitrile on LiMOR, NaMOR, KMOR and CsMOR zeolites have been investigated by FT-IR spectroscopy. Two different CO species, both most probably located in the main channels coordinated on Na ions at IV and VI sites, have been observed. They are associated to a shift of the CO stretching to higher frequencies, as usual. However, together, more strongly bonded species associated to a slight shift of the CO stretching to a lower frequency are also observed. Similar species, with the CN stretching shifted upwards (weaker adsorption) and with the CN stretching shifted downwards (stronger adsorption) are also observed in the case of the interaction of propionitrile (PrN), a molecule that should enter the main channels, and in the case of the interaction of ortho-toluonitrile (o-TN), whose access to the main channels should be highly hindered. The data show that the species characterized by a stronger adsorption but a lower stretching frequency may form both in the main channels and at the external surface. Their formation is easier with the larger cations. These species are identified as "multiply bonded", possibly to two cations. The evidence for this new interaction, stronger than the usual one site-one molecule species, may change considerably the view of the adsorption chemistry of cationic zeolites, from localized simple sites to cooperative complex interactions. 相似文献
130.