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961.
Terra J Gonzalez GB Rossi AM Eon JG Ellis DE 《Physical chemistry chemical physics : PCCP》2010,12(47):15490-15500
Substitution of cadmium into bulk hydroxyapatite Ca((10-x))Cd(x)(PO(4))(6)(OH)(2) (CdHA: x = 0.12, 1.3, 2.5) is studied by combining X-ray diffraction data from synchrotron radiation, Fourier transform infra-red spectroscopy (FTIR) and density functional theory (DFT) calculations. Energetic and electronic analyses are carried out for several configurations of Cd substitution for Ca at both cationic sites. Rietveld analysis shows preferential occupation of the Ca2 site by cadmium. FTIR data suggest a non-negligible covalent character of Cd-OH. The much-discussed cation site preference for substitution is determined on the basis of relaxed-lattice energetics, and interpreted in terms of chemical concepts; theory indicates that the Ca2 site is clearly favored and this preference is related to the more covalent character of this site compared to that of site 1. 相似文献
962.
963.
Spatial and temporal variations of the inherent and apparent optical properties in a shallow coastal lake 总被引:2,自引:0,他引:2
Bracchini L Dattilo AM Falcucci M Loiselle SA Hull V Arena C Rossi C 《Journal of photochemistry and photobiology. B, Biology》2005,80(3):161-177
Apparent and inherent optical properties in the coastal lagoon of Fogliano were measured in three seasonal surveys in 2002. Irradiance data from in situ measurements of ultraviolet and visible wavebands permitted to estimate the related attenuation coefficients. Laboratory extinction measurements on filtered (0.22 microm) and unfiltered water samples were also performed. The integrated approach between in situ and laboratory measurements allowed the determination of the role of the suspended and dissolved matter in the attenuation and extinction of ultraviolet and visible radiation within the water column. As noted, the impact of the suspended and dissolved matter on the lake optical quality was influenced by wind resuspension of particulate matter: the relative role of dissolved matter in the absorption of UV and visible radiation was prevailing at low wind velocity conditions (less than 2.2 m s(-1)), while at high wind velocities (3.9 m s(-1)), particulate matter resuspension strongly influenced the attenuation and the extinction measurements. The extinction in the analyzed wavelengths of filtered and unfiltered water samples and the in situ irradiance measurements allowed us to define new optical parameters and important correlations with limnological and classical optical measurements. By sampling at high spatial resolution (18 stations in 4 km2), it was possible to evidence a spatial gradient of the optical and limnological properties, these distributions showed a consistent pattern in all three surveys, and were important for the characterization of the chromophoric dissolved organic matter that was estimated with the spectral slope of the extinction curve spectra. A relatively higher spectral slope was found in the southern basin with respect to the northern, where the maximum values of the attenuation coefficients and limnological parameters were found. These results suggest different sources of dissolved organic matter and/or a different level of photobleaching. 相似文献
964.
Franco Frau Antonella Rossi Carla Ardau Riccardo Biddau Stefania Da Pelo Davide Atzei Cristina Licheri Carla Cannas GianCarlo Capitani 《Mikrochimica acta》2005,151(3-4):189-201
Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) have been used to refine the solid-state
speciation of As in mine waste materials and stream-bed sediments from the Baccu Locci mine area in Sardinia, Italy. The combined
use of TEM and XPS confirmed previous studies and pointed out that: (i) As is contained in plumbojarosite in substitution
of S, (ii) As-bearing Fe(III) hydroxides are represented by arsenical 2-line ferrihydrites with most Fe/As molar ratios in
the range of 1.6–3.2, (iii) scorodite often lacks long range order. Arsenatian plumbojarosite will tend to dissolve incongruently
in ferrihydrite, releasing Pb and As into water. However, Pb is fated to precipitate as Pb(OH)2 or to be adsorbed onto ferrihydrite, whereas As mobility is favoured since the adsorptive capacity of ferrihydrite for As(V)
is notably reduced under the neutral to alkaline pH conditions occurring in the Baccu Locci stream water. Arsenical ferrihydrites
will tend to be converted into goethite or hematite with time, releasing As into the water as a consequence of the notably
lower density of the adsorption sites of the crystalline Fe(III) phases. Also scorodite is relatively unstable under the Baccu
Locci system conditions, and its stability is further decreased owing to the higher solubility of the amorphous form compared
to the crystalline one. 相似文献
965.
Andrea Marchi Roberto Rossi Adriano Duatti Gian Luigi Zucchini Luciano Magon 《Transition Metal Chemistry》1986,11(5):164-166
Summary The complex [Tc(PPh3)2(CO)3Cl] reacts with the lithium salt of amido-carboxylato- and thiazolato-derivatives to give the new complexes (Ar= C6H4Me-p or C6H4OMe-p), [Tc(PPh3)2(CO)2(amt1,2)] [amt1=anion of 2-(methylamino)thiazole; amt2=anion of 2-4-methoxyphenylamino(thiazole)] and [Tc(PPh3)2(CO)2- (R = Ph2CH, PhCH2 or CCl3). The compounds have been characterized by elemental analysis, and i.r. and1H n.m.r. spectra. 相似文献
966.
6-Chloro-2(2H)-pyranone, which can be prepared in high yield from commercially available trans-glutaconic acid, undergoes facile Pd/Cu-catalyzed reaction with various 1-alkynes to give rise to the corresponding 6-(1-alkynyl)-2(2H)-pyranones in moderate to good yields. These last hitherto unknown compounds have been used as direct precursors to 6-alkyl- and 6-[(Z)-1-alkenyl]-2(2H)-pyranones. 相似文献
967.
Granados AM Kreiker J de Rossi RH Fuertes P Torroba T 《The Journal of organic chemistry》2006,71(2):808-810
[reaction: see text] Tricyclic 4-ethyl-5-thioxo-3H,5H-bis[1,2]dithiolo[3,4-d][4,3-b]pyrrol-3-one and monocyclic 3H-1,2-dithiole-3-thione derivatives reacted with Fischer carbene complexes, giving 1,3-dithiin dithioortho esters through insertion of the carbenic carbon into the S-S bond next to the thiocarbonyl function of the substrate. 相似文献
968.
Rhodium (I) bis-olefin complexes Cp*Rh(VTMS)(2) and CpRh(VTMS)(2) (Cp* = C(5)Me(5), Cp = C(5)Me(4)CF(3), VTMS = vinyl trimethylsilane) were found to catalyze the addition of aromatic aldehydes to olefins to form ketones. Use of the more electron-deficient catalyst CpRh(VTMS)(2) results in faster reaction rates, better selectivity for linear ketone products from alpha-olefins, and broader reaction scope. NMR studies of the hydroacylation of vinyltrimethylsilane showed that the starting Rh(I) bis-olefin complexes and the corresponding Cp*/Rh(CH(2)CH(2)SiMe(3))(CO)(Ar) complexes were catalyst resting states, with an equilibrium established between them prior to turnover. Mechanistic studies suggested that CpRh(VTMS)(2) displayed a faster turnover frequency (relative to Cp*Rh(VTMS)(2)) because of an increase in the rate of reductive elimination, the turnover-limiting step, from the more electron-deficient metal center of CpRh(VTMS)(2). Reaction of Cp*/Rh(CH(2)CH(2)SiMe(3))(CO)(Ar) with PMe(3) yields acyl complexes Cp*/Rh[C(O)CH(2)CH(2)SiMe(3)](PMe(3))(Ar); measured first-order rates of reductive elimination of ketone from these Rh(III) complexes established that the Cp ligand accelerates this process relative to the Cp* ligand. 相似文献
969.
A new tetraphosphine, all-cis-3-(2-diphenylphosphinoethyl)-1,2,4-tris(diphenylphosphinomethyl)cyclopentane (Ditricyp), has been synthesised in seven steps from commercially available dicyclopentadiene. The ozonolysis of dicyclopentadiene occurred first on the double bond of the bicycloheptene moiety. A very high chemoselective ozonolysis was observed at −60 °C leading to the diol after reductive treatment. From this diol, cis,cis,cis-3-(2-hydroxyethyl)-1,2,4-tri(hydroxymethyl)cyclopentane was obtained after a second ozonolysis. Mesylation and substitution with Ph2PLi led to the title tetradiphenylphosphine Ditricyp. The efficiency of this new tetraphosphine ligand for palladium-catalysed coupling reactions has been studied. Satisfactory results in terms of substrate/catalyst ratio have been obtained for Suzuki, Negishi and Sonogashira couplings and also for Heck vinylation reaction. After chromatographic separation, one enantiomer of this ligand associated to palladium was able to induce enantioselective allylic alkylation with modest enantiomeric excess. 相似文献
970.
Slice imaging experiments are reported for the quantum state-to-state photodissociation dynamics of OCS. Both one-laser and two-laser experiments are presented detecting CO(J) or S((1)D(2)) photofragments from the dissociation of hexapole state-selected OCS(v(2) = 0,1,2 / J = 1,2) molecules. We present data using our recently developed large frame CCD centroiding detector and have implemented a new high speed MCP high voltage pulser with an effective slice width of only 6 ns. Slice images are presented for quantum state-to-state photolysis, near 230 nm, of vibrationally excited OCS(v(2) = 0,1,2). Two-laser pump-probe experiments detecting CO(J = 63 or 64) show a dramatic change in the beta parameter for the same final state of CO(J) when the photolysis energy is reduced by about 1000 cm(-1). We attribute the observed change from large positive to large negative beta to a large increase of the molecular frame deflection angle at very slow recoil velocity, due to a breakdown of the axial recoil. Two-laser experiments on the S((1)D(2)) fragment reveal single well-separated rings in the slice images correlating with individual CO(J) states. Strong polarization effects of the probe laser are observed, both in the angular distribution of the intensity of single S((1)D(2)) rings and in the resolution of the radial velocity distribution. It is shown how the broadening of the velocity distribution can be reduced by a directed ejection of the electron in the ionization process perpendicular to the slice imaging plane. The dissociation energy of OCS(v(2) = 0, J = 0) --> CO(J = 0) + S((1)D(2)) is determined with high accuracy D(0) = (34 608 +/- 24) cm(-1). 相似文献