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81.
Giuseppe Bruno Francesco Nicol Fausto Puntoriero Gaetano Giuffrida Vittorio Ricevuto Giuseppe Rosace 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(7):o390-o391
The title compound, C21H19N7, is a polypyridine ligand that is suitable for assembling complex metal systems capable of photoinduced electron transfer. The solid‐state structure has been determined at room temperature by single‐crystal X‐ray diffraction. The molecule is not flat and both the bis(pyridyl)triazole and the benzylideneamine fragments show significant distortions from planarity. 相似文献
82.
Daniela Belli Dell'Amico Fausto Calderazzo Luca Labella Fabio Lorenzini Fabio Marchetti 《无机化学与普通化学杂志》2002,628(8):1868-1872
The hydrogensulfato‐carbonyl derivative [Cu(CO)(SO4H)]n, as obtained from the Cu2O/ H2SO4/CO system and recrystallized from H2SO4/(CH3O)2SO2 has been shown to possess a crystal structure organised in infinite chains built up by corner sharing of {CuO3(CO)} and {S(OH)O3} tetrahedra. The chains are connected by hydrogen bonds in layers, with CO groups leaning out on both sides. The absorption of CO by CuSO4/Cu or by Cu2O in sulfuric acid was quantified as a function of concentration. The CuSO4/Cu system in water absorbs carbon monoxide (CO/Cu molar ratio = 1.0). 相似文献
83.
Pump−probe experiments at the TEMPO beamline using the low‐α operation mode of Synchrotron SOLEIL
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Mathieu G. Silly Tom Ferté Marie Agnes Tordeux Debora Pierucci Nathan Beaulieu Christian Chauvet Federico Pressacco Fausto Sirotti Horia Popescu Victor Lopez-Flores Marina Tortarolo Maurizio Sacchi Nicolas Jaouen Philippe Hollander Jean Paul Ricaud Nicolas Bergeard Christine Boeglin Bharati Tudu Renaud Delaunay Jan Luning Gregory Malinowski Michel Hehn Cédric Baumier Franck Fortuna Damjan Krizmancic Luigi Stebel Rudi Sergo Giuseppe Cautero 《Journal of synchrotron radiation》2017,24(4):886-897
The SOLEIL synchrotron radiation source is regularly operated in special filling modes dedicated to pump–probe experiments. Among others, the low‐α mode operation is characterized by shorter pulse duration and represents the natural bridge between 50 ps synchrotron pulses and femtosecond experiments. Here, the capabilities in low‐α mode of the experimental set‐ups developed at the TEMPO beamline to perform pump–probe experiments with soft X‐rays based on photoelectron or photon detection are presented. A 282 kHz repetition‐rate femtosecond laser is synchronized with the synchrotron radiation time structure to induce fast electronic and/or magnetic excitations. Detection is performed using a two‐dimensional space resolution plus time resolution detector based on microchannel plates equipped with a delay line. Results of time‐resolved photoelectron spectroscopy, circular dichroism and magnetic scattering experiments are reported, and their respective advantages and limitations in the framework of high‐time‐resolution pump–probe experiments compared and discussed. 相似文献
84.
85.
Ortica F Smimmo P Mazzucato U Favaro G Heynderickx A Moustrou C Samat A 《Photochemistry and photobiology》2006,82(5):1326-1333
The photobehavior of five photochromic dipyrrolyl-perfluoro-cyclopentenes was studied by steady state and time-resolved absorption spectroscopy. The quantum yields of the UV-photoinduced ring-closing reaction (coloration) and the visible-stimulated cycloreversion reaction (bleaching) were measured. Kinetic and thermodynamic parameters of thermal bleaching were also determined. Nanosecond time-resolved experiments showed formation of a transient, which was not a precursor of the reaction photoproduct. This transient was tentatively assigned to a radical cation formed by direct photoionization through a short-lived triplet state. The nature of the transient species was supported by photoinduced electron transfer to electron acceptors. 相似文献
86.
Marie Labat Jean-Blaise Brubach Alessandra Ciavardini Marie-Emmanuelle Couprie Erik Elkaim Pierre Fertey Tom Ferte Philippe Hollander Nicolas Hubert Emmanuelle Jal Claire Laulhé Jan Luning Olivier Marcouillé Thierry Moreno Paul Morin Francois Polack Pascale Prigent Sylvain Ravy Jean-Paul Ricaud Pascale Roy Mathieu Silly Fausto Sirotti Amina Taleb Marie-Agnès Tordeux Amor Nadji 《Journal of synchrotron radiation》2018,25(2):385-398
The investigation of ultrafast dynamics, taking place on the few to sub‐picosecond time scale, is today a very active research area pursued in a variety of scientific domains. With the recent advent of X‐ray free‐electron lasers (XFELs), providing very intense X‐ray pulses of duration as short as a few femtoseconds, this research field has gained further momentum. As a consequence, the demand for access strongly exceeds the capacity of the very few XFEL facilities existing worldwide. This situation motivates the development of alternative sub‐picosecond pulsed X‐ray sources among which femtoslicing facilities at synchrotron radiation storage rings are standing out due to their tunability over an extended photon energy range and their high stability. Following the success of the femtoslicing installations at ALS, BESSY‐II, SLS and UVSOR, SOLEIL decided to implement a femtoslicing facility. Several challenges were faced, including operation at the highest electron beam energy ever, and achievement of slice separation exclusively with the natural dispersion function of the storage ring. SOLEIL's setup also enables, for the first time, delivering sub‐picosecond pulses simultaneously to several beamlines. This last feature enlarges the experimental capabilities of the facility, which covers the soft and hard X‐ray photon energy range. In this paper, the commissioning of this original femtoslicing facility is reported. Furthermore, it is shown that the slicing‐induced THz signal can be used to derive a quantitative estimate for the degree of energy exchange between the femtosecond infrared laser pulse and the circulating electron bunch. 相似文献
87.
Low temperature Fourier transform infrared spectra and hydrogen bonding in polycrystalline uracil and thymine 总被引:1,自引:0,他引:1
Rozenberg M Shoham G Reva I Fausto R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(10):2323-2336
The FTIR spectra of pure NH and isotopically diluted (NH/ND and ND/NH) polycrystalline uracil and thymine were measured in the range 4000-400 cm(-1) at temperatures from 300 to 10K. For the first time, the essentially narrow bands corresponding to the uncoupled stretching (nu(1)) and out of plane bending (nu(4)) NH proton modes of uracil and thymine were observed in the solid phase. It was found that in the nu(4) region the spectra reveal more details on the H-bond interactions present in both solids than in the nu(1) range. The frequencies of the various bands observed in both spectral regions were used for estimation of the H-bond energy, using empirical correlations between this property and both the red shift of nu(1) and the blue shift of nu(4) that occur upon crystallization due to the establishment of the H-bonds. The results are compared with known thermodynamic, structural and theoretical data. The IR data also suggest that the H-bond networks of both crystals contain, besides the two NH...O=C bonds revealed by X-ray experiments, additional types of H-bonds, which do not show long range periodicity and, thus, cannot be detected by the conventional structural methods. The assignment of some other bands in the spectra of both substances was also reviewed. 相似文献
88.
Anna?AmatEmail author Simona?FantacciEmail author Filippo?De?Angelis Benedetta?Carlotti Fausto?Elisei 《Theoretical chemistry accounts》2012,131(5):1218
Tetracyclines are a class of derivatives of polycyclic naphthacene carboxamide, which have attracted wide interest in the
pharmaceutical field for their use as antibiotics. These molecules are characterized by a substantial conformational flexibility
and by the presence of different binding sites which endow tetracycline with a noticeable capability in binding biological
targets. A salient property of tetracyclines is the presence of multiple acidic groups: four equilibrium constants have been
measured for the fully protonated tetracycline (TCH3
+) but so far no clear information concerning the pKas of the various sites has been reported. We present here a computational investigation on the correlation between the acid–base
and the spectroscopic properties of this important class of compounds. Starting from the TCH3
+ species, the pKa of all the possible deprotonation sites has been computed by DFT calculations. The computed pKas nicely compare with the experimental data, within 1 pKa unit, allowing us to individuate the products of the first deprotonation. This procedure has been iteratively repeated using
as starting species the products singled out from the previous deprotonation, thus individuating the stepwise products of
each deprotonation step. Then, the optical absorption spectra have been computed for all the species involved in the protonation/deprotonation
equilibria, comparing the results with the experimental data. The good agreement between theory and experiment has allowed
us to rationalize the correlation between the solution pH and the absorption spectra. 相似文献
89.
Spectroscopic techniques both in steady-state (in absorption and emission) and pulsed (absorption of excited states with femtosecond resolution) conditions were used to study the complexation process between six molecules belonging to the tetracycline family and Mg(2+); in the case of TC the study was extended to the metal ions Ca(2+) and Cu(2+). The study was carried out in aqueous solution at various pH values, where one acid-base form of the substrate prevails over the others. The processing of experimental results, performed by means of Singular Value Decomposition and Global Analysis methods, allowed us to evaluate the extent of interaction through the association constants, to identify the number of equilibria present in solution and the stoichiometry (1:1 or 1:2) of the tetracycline:metal ion complex, and to define the spectral and photophysical properties of the latter (in terms of fluorescence quantum yields, lifetimes and rate constants). In fact, the (allowed) radiative decay process is a minor root for the lowest excited state of the complexes which mainly decay to the ground state by internal conversion. Details of the complexation sites are proposed for the various protonated forms of tetracyclines, and for the various cations in the case of TC. In particular, the molecular structure seems to affect significantly the dynamics of interaction when the upper peripheral region of tetracycline is rich in additional hydroxyl groups. Moreover, the state of protonation of the substrate produces changes in the order of the complexation sites, whose affinity for the cation increases significantly when they are negatively charged owing to the loss of protons. Magnesium and calcium (hard cations) give similar interactions, at least in acid solution, while copper(ii) (borderline cation) binds more efficiently on different sites, thus forming complexes with different properties. 相似文献
90.
Redondo-Morata L Giannotti MI Sanz F 《Langmuir : the ACS journal of surfaces and colloids》2012,28(15):6403-6410
The lipid bilayer rupture phenomenon is here explored by means of atomic force microscopy (AFM)-based force clamp, for the first time to our knowledge, to evaluate how lipid membranes respond when compressed under an external constant force, in the range of nanonewtons. Using this method, we were able to directly quantify the kinetics of the membrane rupture event and the associated energy barriers, for both single supported bilayers and multibilayers, in contradistinction to the classic studies performed at constant velocity. Moreover, the affected area of the membrane during the rupture process was calculated using an elastic deformation model. The elucidated information not only contributes to a better understanding of such relevant process, but also proves the suitability of AFM-based force clamp to study model structures as lipid bilayers. These findings on the kinetics of lipid bilayers rupture could be extended and applied to the study of other molecular thin films. Furthermore, systems of higher complexity such as models mimicking cell membranes could be studied by means of AFM-based force-clamp technique. 相似文献