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101.
Regularity results and critical group estimates are studied for critical (p, r)-systems. Multiplicity results of solutions for a critical potential quasilinear system are also proved using Morse theory. 相似文献
102.
103.
Andrey A. Toropov Alla P. Toropova Emilio Benfenati Giuseppina Gini Roberto Fanelli 《Structural chemistry》2013,24(4):1369-1381
A series of 53 endochin analogs (4(1-H)-quinolone derivatives) with anti-malarial activity against the clinically relevant multidrug resistant malarial strain TM-90-C2B has been studied. The CORAL (http://www.insilico.eu/coral) software has been used as a tool to build up the quantitative structure–activity relationships (QSAR) for the anti-malaria activity. The QSAR models were calculated with the representation of the molecular structure by simplified molecular input-line entry system and by the molecular graph of atomic orbitals. The method for splitting data into the sub-training set, the calibration set, the test set, and the validation set is suggested. Three various splits were examined. Statistical quality of models for the validation sets (which are not involved in the building up models) is good. Structural indicators (alerts) for increase and decrease of the anti-malaria activity are defined. 相似文献
104.
Pineschi M Del Moro F Gini F Minnaard AJ Feringa BL 《Chemical communications (Cambridge, England)》2004,(10):1244-1245
For the first time, an excellent enantioselectivity has been obtained in the conjugate addition of hard organometallic reagents to alpha,beta-unsaturated lactams bearing appropriate protecting-activating groups on the nitrogen. 相似文献
105.
Nir Barnea Victor Efros Winfried Leidemann Giuseppina Orlandini Edward Tomusiak 《Few-Body Systems》2014,55(8-10):1051-1053
This poster presentation is intended to show preliminary results from calculations of the inclusive (e,e′) transverse response functions of 4He. Up to now we have only included the E1 and M1 multipoles and therefore no comparison with experiment is shown. That will be done once all relevant multipoles have been calculated. Details of the calculation are summarized in the text below. 相似文献
106.
Manet I Manoli F Donzello MP Viola E Andreano G Masi A Cellai L Monti S 《Organic & biomolecular chemistry》2011,9(3):684-688
A water soluble Zn(II) porphyrazine drives the conformational equilibrium of the G-quadruplex of a human telomeric sequence exclusively towards a parallel conformation upon complexation. 相似文献
107.
Francesco Dallavalle Giuseppina Folesani Enrico Leporati Gianni Galaverna 《Helvetica chimica acta》1996,79(7):1818-1824
Formation constants of ternary complexes of CuII with (S)-amino-acid amides ((S)-phenylalaninamide, (S)-prolinamide, and (S)-tryptophanamide) and (R)- or (S)-histidine and (R)- or (S)-tyrosine were determined potentiometrically in aqueous solution. Significant stereoselectivity was presented by all three amides towards histidine, the diastereoisomeric complexes with ‘heterochiral’ ligands being more stable than those with ‘homochiral’ ligands (see Table 3). The stereoselectivity observed with (S)-phenylalaninamide and (S)-tryptophanamide may be explained on the basis of hydrophobic stacking interactions between 1H-imidazole and the aromatic side chain, favoured by the terdentate behaviour of histidine (see Fig.2), whereas repulsive effects seem to be prevalent with (S)-prolinamide. Only (S)-prolinamide and (S)-phenylalaninamide show appreciable stereoselectivity with tyrosine, which is bidentate, probably on account of repulsive interactions. The present results on the stability of ternary complexes in solution allow to draw some conclusions on the mechanism of chiral discrimination performed by CuII complexes of (S)-amino-acid amides added to the mobile phase in HPLC (reversed phase). 相似文献
108.
Giuseppina Castronuovo Marcella Niccoli 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(1-2):69-76
The formation of complexes between β-cyclodextrin or methyl-β-cyclodextrin and monocarboxylic acids from C5 to C12 has been studied calorimetrically at 298 K in aqueous buffer phosphate, pH 11.3. When a complex forms, calorimetry enables
the calculation of both the enthalpy and the association constant, from which the Gibbs free energy and the entropy of the
process can be obtained. The forces involved in the association process are then discussed in the light of the signs and values
of the thermodynamic parameters obtained. For β-cyclodextrin, 1:1 inclusion complexes form, characterized by an irregular
variation in the values of enthalpies, entropies and association constants at increasing alkyl chain length. A model is proposed
to explain this unusual behaviour for acids longer than ten carbon atoms. The association involving methyl-β-cyclodextrin
shows, instead, a regular variation of the thermodynamic parameters up to the C12 term. An elongation of the cavity effect is discussed: the cavity behaves as it were deeper than that of the natural cyclodextrins.
Association is characterized prevailingly by hydrophobic interactions; for the longer terms, the high and almost invariant
entropic contribution determines the large association constants, notwithstanding the positive, unfavorable enthalpic contribution.
This is an indication that the relaxation of water molecules from the hydrophobic hydration shells of the external methyl
groups is the contribution that mainly determines the association process. 相似文献
109.
Concistré M De Lorenzo L De Luca G Longeri M Pileio G Raos G 《The journal of physical chemistry. A》2005,109(44):9953-9963
We have obtained a very large data set of spectral parameters from the analysis of (1)H NMR and (13)C satellite spectra of 2,2'-bithiophene dissolved in anisotropic, partially orienting mesophases. In particular, this parameter set includes 33 dipolar couplings, which are directly related to the interatomic distances, the dihedral angle phi between the two thiophenic rings, and the anisotropic solute-solvent interaction potential. This allows an exhaustive investigation of the conformational equilibrium of 2,2'-bithiophene in a liquidlike phase. Comparison with the predictions of high-level theoretical calculations for the isolated molecule provides evidence of a strong flattening as well as the sharpening effect of the medium on the conformer population. The approximations needed to apply vibrational corrections to flexible molecules are discussed in detail and some general conclusions concerning their effect on structure and conformational equilibria are proposed. 相似文献
110.
When biomaterials are inserted in a biological environment, for instance in a body implant, proteins do quickly adsorb on the exposed surface. Such process is of fundamental importance, since it directs the subsequent cell adhesion. Here we review recent advances in this field obtained with molecular simulations. While coarse-grained models can provide important general results, as it has long been recognized in polymer science, the hierarchical structure of a very complex copolymer such as a protein, together with the nature of the biomaterial surface suggest that atomistic models are better suited to investigate these phenomena. Thus, after briefly mentioning some common features of coarse-grained and atomistic force fields, we first discuss early theoretical and coarse-grained simulation results about protein adsorption, and then we highlight the main results recently obtained by us with atomistic models. In particular, we discuss some conformational and energetic aspects of the adsorption of protein fragments with different secondary structure on surfaces of different wettability, including hydrophobic graphite and hydrophilic poly(vinylalcohol). We also consider other features, such as the simulation of the materials wettability, the hydration of the adsorbed fragments, their kinetics of spreading, and the sequential adsorption of two protein fragments on top of each other, highlighting the results of general interest. 相似文献