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101.
Walrand J Lengelé M Blanquet G Lepère M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(3):421-426
Absolute intensities have been measured for 26 lines of C2H4 in the nu7 fundamental transition, using a tunable diode-laser spectrometer. These lines with 3< or = J"< or = 21, 2< or = Ka< or = 4, 2< or = Kc< or = 20 are located in the spectral range 920-980 cm(-1). The intensities have been measured by using two methods: the equivalent width method (EWM) and the line profile fit method (FPM). For the last one, three models have been tested: Voigt, Rautian and Galatry profiles. 相似文献
102.
Visser T Nijhuis TA van der Eerden AM Jenken K Ji Y Bras W Nikitenko S Ikeda Y Lepage M Weckhuysen BM 《The journal of physical chemistry. B》2005,109(9):3822-3831
Well-defined Pt-nanoparticles with an average diameter of 1 nm supported on a series of zeolite Y samples containing different monovalent (H+, Na+, K+, Rb+, and Cs+) and divalent (Mg2+, Ca2+, Sr2+, and Ba2+) cations have been used as model systems to investigate the effect of promotor elements in the oxidation of CO in excess oxygen. Time-resolved infrared spectroscopy measurements allowed us to study the temperature-programmed desorption of CO from supported Pt nanoparticles to monitor the electronic changes in the local environment of adsorbed CO. It was found that the red shift of the linear Pt-coordinated CO vibration compared to that of gas-phase CO increases with an increasing cation radius-to-charge ratio. In addition, a systematic shift from linear (L) to bridge (B) bonded CO was observed for decreasing Lewis acidity, as expressed by the Kamlet-Taft parameter alpha. A decreasing alpha results in an increasing electron charge on the framework oxygen atoms and therefore an increasing electron charge on the supported Pt nanoparticles. This observation was confirmed with X-ray absorption spectroscopy, and the intensity of the experimental Pt atomic XAFS correlates with the Lewis acidity of the cation introduced. Furthermore, it was found that the CO coverage increases with increasing electron density on the Pt nanoparticles. This increasing electron density was found to result in an increased CO oxidation activity; i.e., the T(50%) for CO oxidation decreases with decreasing alpha. In other words, basic promotors facilitate the chemisorption of CO on the Pt particles. The most promoted CO oxidation catalyst is a Pt/K-Y sample, which has a T(50%) of 390 K and a L:B intensity ratio of 2.7. The obtained results provide guidelines to design improved CO oxidation catalysts. 相似文献
103.
J. Ruiz T. Antequera A. I. Andres M. J. Petron E. Muriel 《Analytica chimica acta》2004,520(1-2):201-205
The most used method for muscle lipid fractionation into major lipid classes was modified for improving its separation efficiency. Extracted lipids from a masseter muscle of one Iberian pig were separated into neutral lipids (NL), free fatty acids (FFA) and polar lipids (PL) using aminopropyl minicolumns, following the extensively used method of Kaluzny et al. [1] (old method-OM-) and a method based on that, developed by Pinkart et al. [2] with some (modifications modified method–MM). Obtained lipid classes were further analysed by TLC and lipid fractions were identified. TLC evidenced the presence of a certain amount of PL in the NL fraction obtained with the OM. On the other hand, using the MM only an almost undetectable presence of PL was evidenced in the NL fraction. Fatty acid composition of NL, PL and FFA obtained with each method was studied by gas chromatography. Fatty acid profile of NL was strongly influenced by the separation method used. Thus, NL obtained using the OM showed higher amounts of saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) and lower of monounsaturated fatty acids (MUFA) than those obtained using the MM. Moreover, NL obtained using the OM showed the presence of fatty alcohols, constituents of phospholipids (PhL) absent or present only in trace amounts in acylglycerols. This profile reflects the coelution of PL in the NL fraction. Fatty acid profile of FFA and PL fractions was also influenced by the solid phase extraction (SPE) method used, but to a lesser extent. 相似文献
104.
[Ru(II)(terpy)(DMSO)Cl(2)] complexes were synthesized as a 5/1 mixture of cis and trans isomers, and their reactivities with CO and with substituted 2,2':6',2' '-terpyridine (terpy) moieties have been investigated. The structure of a trans isomer and its CO adduct have been unambiguously assigned by spectroscopy and X-ray diffraction. The [Ru(terpy)(terpy-Br)](2+) complex prepared either from the cis-[Ru(II)(terpy)(DMSO)Cl(2)] or from the cis-[Ru(II)(terpy-Br)(DMSO)Cl(2)] precursor appeared to be reactive in cross-coupling reactions promoted by low-valent palladium(0) and is an attractive target for the stepwise synthesis of polynuclear complexes bearing vacant coordination sites (terpy-Br for 4'-bromo-2,2':6',2' '-terpyridine). Several bipyridine, phenanthroline, and bipyrimidine complexes were prepared this way and their optical and redox properties determined and discussed. 相似文献
105.
Herman Gershon Donald D. Clarke John J. McMahon Muriel Gershon 《Monatshefte für Chemie / Chemical Monthly》2001,132(7):833-838
Summary. 2,5-, 3,5-, 3,6-, 3,7-, 4,5-, 5,6-, 5,7-, and 6,7-dibromo-8-quinolinols were prepared and tested against six fungi (Aspergillus niger, Aspergillus oryzae, Myrothecium verrucaria, Trichoderma viride, Mucor cirinelloides, and Trichophyton mentagrophytes) in Sabouraud dextrose broth. Most of the compounds were strongly antifungal, inhibiting five of the fungi below 1μg/cm3, but were somewhat less fungitoxic than the corresponding chloro analogues. M. cirinelloides was not inhibited by any of the compounds except 4,5-dibromo-8-quinolinol. This high level of fungitoxicity is attributed
to intramolecular synergism.
Received December 28, 2000. Accepted (revised) February 3, 2001 相似文献
106.
Muriel Hissler Anthony Harriman Pierre Jost Georges Wipff Raymond Ziessel 《Angewandte Chemie (International ed. in English)》1998,37(23):3249-3252
Binding of K + or Ba 2+ ions attenuates intramolecular electron transfer between a chromophore and an electron-affinic macrocyclic receptor (see schematic representation), and simultaneously amplifies luminescence. In the complexed state, photons absorbed by the dicationic chromophore are emitted as luminescence, whereas illumination of the uncomplexed superstructure causes rapid reduction of the receptor. 相似文献
107.
Jean-Pierre Bouanich Ghislain Blanquet Muriel Lepère 《Journal of Molecular Spectroscopy》2004,227(2):172-179
H2-broadening coefficients have been measured for 35 lines of C2H4 at 173.2 K in the P, Q, and R branches of the ν7 fundamental band near 10 μm, using a tunable diode-laser spectrometer. These lines were individually fitted with a Voigt and a Rautian profile to determine their collisional widths. The resulting broadening coefficients, as well as those previously measured at room temperature are compared with values calculated on the basis of a semiclassical model of interacting linear molecules, using an atom-atom Lennard-Jones potential in addition to the weak electrostatic contributions. A satisfactory agreement is obtained for the results at room temperature, but the theoretical results at low temperature are generally smaller than the experimental data. Finally, the temperature dependence of the broadening coefficients has been determined both experimentally and theoretically. 相似文献
108.
In this paper we propose the application of double cavity fiber resonators as timing extraction circuits for gigabit networks. Spectral properties of double cavity fiber resonators, including the spectral enhancement achieved by means of the vemier effectare outlined. We investigate their suitability to obtain low cost all-fiber timing extraction circuits in broadband optical networks where single cavity structures previouslyproposed in the literature cannot be efficiently applied. 相似文献
109.
Muriel Ney-Nifle Marc Gabay 《Physica C: Superconductivity and its Applications》1995,250(3-4):349-360
We study the thermal fluctuations of anisotropic order parameters (OP) in layered superconductors. In particular, for copper oxides and a d-wave OP, we present some experimental consequences of fluctuations in the direction normal to the layers. It is shown that the c-axis penetration depth λc can have a “disorder-like” quadratic temperature dependence at low temperature. The fluctuations are analyzed in the framework of a Lawrence-Doniach model with an isotropic Fermi surface. Anisotropies pin the orientation of the OP to the crystallographic axes of the lattice. Then we study an extended t-J model that fits Fermi surface data of bilayers YBCO and BSCCO. This leads to a d-wave OP with two possible orientations and, including the thermal fluctuations, yields the announced temperature dependence of λc. Furthermore a reservoir layer is introduced. It implies a finite density of states at the Fermi energy which is successfully compared to conductance and specific heat measurements. 相似文献
110.