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41.
42.
Giovanna Bruni C. Milanese G. Bellazzi V. Berbenni P. Cofrancesco A. Marini M. Villa 《Journal of Thermal Analysis and Calorimetry》2007,89(3):761-766
The processes of production of drugs and dosage forms in the solid state often cause unwanted transformation of portions of
the substances into amorphous state, with significant changes of properties such as stability and bio-availability. When this
amorphous fraction is of the order of a few percent, it usually goes unnoticed, but it should be accurately determined within
a quality control system. In this work, we consider a model drug, perphenazine, where partial amorphisation may be induced
by standard mechanical treatments.
We show that Differential Scanning Calorimetry (DSC) leads to consistent estimations of the amorphous fractions induced by
the treatment. Furthermore, DSC also yields the expected amounts of amorphous perphenazine when analysing known mixtures of
perfectly crystalline samples (untreated) and partially amorphous samples (treated). We show that even amorphous fractions
of the order of 1% are accurately estimated by our method. 相似文献
43.
Mancinelli R Sodo A Bruni F Ricci MA Soper AK 《The journal of physical chemistry. B》2009,113(13):4075-4081
Neutron diffraction experiments with hydrogen isotope substitution on aqueous solutions of HCl and HBr have been performed at concentrations ranging from 1:17 to 1:83 solute per water molecules, at ambient conditions. Data are analyzed using the empirical potential structure refinement technique in order to extract information on both the ion hydration shells and the microscopic structure of the solvent. It is found that the influence of these solutes on the water structure is less concentration dependent than that of salts or hydroxides. Moreover protons readily form a strong H-bond with a water molecule upon solvation, at all proportions. The majority of them is also bonded via a longer bond to another water molecule, giving a prepeak in the g(OwOw). At high solute concentration, the second water molecule may be substituted by the counterion. In particular at solute concentrations of the order of 1:17 or higher, all protons have an anion within a distance of 4.5 A. 相似文献
44.
A. Marini V. Berbenni G. Bruni A. Maggioni M. Villa 《Journal of Thermal Analysis and Calorimetry》1999,56(2):699-715
The heat capacity calibration ‘constants’ of a commercial MTDSC system (TA 3100) were determined in a variety of experimental
conditions. For a given modulation frequency, the calibration constants are the same within a few percents for different temperatures,
and over a wide range of modulation amplitudes and scan rates. This variation decreases below 1% if hidden instrumental constraints
are taken into account, which are related with the capability of the control system to achieve the desired temperature program.
On the other hand, the calibration constant changes substantially with the period, and takes anomalously high values for the
short modulation periods (20+40 s). Rules to optimize the accuracy of the system are given.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
45.
46.
G. Bruni A. Marini V. Berbenni R. Riccardi M. Villa 《Journal of inclusion phenomena and macrocyclic chemistry》1999,35(3):517-530
The ketoprofen/beta-cyclodextrin (-CD) inclusion compounds may be conveniently obtained through a solid state reaction at room temperature in the presence of saturated water vapour. Relative to the corresponding complexes produced with the usual coprecipitation method, the new compounds have a higher ketoprofen content and/or different properties. In particular, the formation reaction is not accompanied by a loss of hydration water, which is released in distinct stages upon heating. The thermodynamics of the dehydration process is discussed. 相似文献
47.
48.
Imberti S Botti A Bruni F Cappa G Ricci MA Soper AK 《The Journal of chemical physics》2005,122(19):194509
Neutron-diffraction data on aqueous solutions of hydroxides, at solute concentrations ranging from 1 solute per 12 water molecules to 1 solute per 3 water molecules, are analyzed by means of a Monte Carlo simulation (empirical potential structure refinement), in order to determine the hydration shell of the OH- in the presence of the smaller alkali metal ions. It is demonstrated that the symmetry argument between H+ and OH- cannot be used, at least in the liquid phase at such high concentrations, for determining the hydroxide hydration shell. Water molecules in the hydration shell of K+ orient their dipole moment at about 45 degrees from the K+-water oxygen director, instead of radially as in the case of the Li+ and Na+ hydration shells. The K+-water oxygen radial distribution function shows a shallower first minimum compared to the other cation-water oxygen functions. The influence of the solutes on the water-water radial distribution functions is shown to have an effect on the water structure equivalent to an increase in the pressure of the water, depending on both ion concentration and ionic radius. The changes of the water structure in the presence of charged solutes and the differences among the hydration shells of the different cations are used to present a qualitative explanation of the observed cation mobility. 相似文献
49.
Di Vaira M Bazzicalupi C Orioli P Messori L Bruni B Zatta P 《Inorganic chemistry》2004,43(13):3795-3797
Clioquinol, a 8-hydroxyquinoline derivative, is producing very encouraging results in the treatment of Alzheimer's disease (AD). Its biological effects are most likely ascribed to complexation of specific metal ions, such as copper(II) and zinc(II), critically associated with protein aggregation and degeneration processes in the brain. We report here, for the first time, a structural characterization of the zinc(II) and copper(II) complexes of clioquinol. A ligand to metal stoichiometry of 2:1 is found in both cases, though in the presence of quite different coordination polyhedra. The present findings are discussed in the frame of modern approaches to AD treatment. 相似文献
50.
G. De Ninno D. Fanelli C. Bruni M.E. Couprie 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(2):269-277
The temporal dynamics of a storage-ring Free Electron Laser is here investigated with particular attention to the case in
which an external modulation is applied to the laser-electron beam detuning. The system is shown to produce bifurcations as
well as chaotic regimes. The peculiarities of this phenomenon with respect to the analogous behaviour displayed by conventional
laser sources are pointed out. Theoretical results, obtained by means of a phenomenological model reproducing the evolution
of the main statistical parameters of the system, are shown to be in a good agreement with experiments carried out on the
Super-ACO Free Electron Laser.
Received 27 March 2002 / Received in final form 17 July 2002 Published online 21 January 2003
RID="a"
ID="a"Present address: Sincrotone Trieste, 34012 Trieste, Italy.
RID="b"
ID="b"e-mail: fanelli@nada.kth.se 相似文献