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761.
Porchia M Papini G Santini C Gioia Lobbia G Pellei M Tisato F Bandoli G Dolmella A 《Inorganic chemistry》2005,44(11):4045-4054
Reactions of [NBu4][Re(O)Cl4] with bis(pyrazol-1-yl)methane (bpzm) and bis(pyrazol-1-yl)acetate (Hbpza) and with the lithium salts lithium [bis(3,5-dimethylpyrazol-1-yl)acetate] (Libdmpza) and lithium [bis(3,5-dimethylpyrazol-1-yl)methanesulfonate] (Libdmpzs) produce a series of new compounds containing either a kappa2-N,N bidentate pyrazolyl ligand [Re(O)(bpzm)Cl3 (1), Re(O)(bpzm)(OMe)Cl2 (2), Re(O)(bpzaOMe)(OMe)Cl2 (4)] or a kappa3-N,N,O heteroscorpionate [Re(O)(bpza)Cl2 (3), Re(O)(bdmpza)Cl2 isomers 5 and 6, Re(O)(bdmpza)(OMe)Cl (7), Re(O)(bdmpza)(OEt)Cl (8), Re(O)(bdmpzs)(OMe)Cl (9), Re(O)(bdmpzs)(OEt)Cl (10)]. X-ray analyses of 1 and 3 show in both cases a distorted octahedral environment around the rhenium atom. The nature and the geometry of the products are strongly determined by the reaction solvent and by the heteroscorpionate ligand itself. When scorpionates bear methylated pyrazolyl rings mixed heterocomplexes Re(O)(bdmpza)(glycol) (11) and Re(O)(bdmpzs)(glycol) (12) are obtained (H2glycol = ethylene glycol). Also 11 shows an octahedral geometry as assessed by X-ray study. 相似文献
762.
Ulic SE Kosma A Leibold C Della Védova CO Willner H Oberhammer H 《The journal of physical chemistry. A》2005,109(16):3739-3744
Structural and conformational properties of two sulfenyl derivatives, trifluoromethanesulfenyl acetate, CF3S-OC(O)CH3 (1), and trifluoromethanesulfenyl trifluoroacetate, CF3S-OC(O)CF3 (2), were determined by gas electron diffraction, vibrational spectroscopy, in particular with IR (matrix) spectroscopy, which includes photochemical studies, and by quantum chemical calculations. Both compounds exist in the gas phase as a mixture of two conformers, with the prevailing component possessing a gauche structure around the S-O bond. The minor form, 15(5)% in 1 and 11(5)% in 2 according to IR(matrix) spectra, possesses an unexpected trans structure around the S-O bond. The C=O bond of the acetyl group is oriented syn with respect to the S-O bond in both conformers. UV-visible broad band irradiation of 1 and 2 isolated in inert gas matrixes causes various changes to occur. Conformational randomization clearly takes place in 2 with simultaneous formation of CF3SCF3. For 1 the only reaction channel detected leads to the formation of CH3SCF3 with the consequent extrusion of CO2. Quantum chemical calculations (B3LYP/6-31G and MP2 with 6-31G and 6-311G(2df,pd) basis sets) confirm the existence of a stable trans conformer. The calculations reproduce the conformational properties for both compounds qualitatively correct with the exception of the B3LYP method for compound 2 which predicts the trans form to be prevailing, in contrast to the experiment. 相似文献
763.
Giovanna Brusatin Gioia Della Giustina Massimo Guglielmi Plinio Innocenzi 《Progress in Solid State Chemistry》2006,34(2-4):223
Hybrid sol-gel materials are promising candidates for electro/optical applications, combining the most important glass-like and polymer-like properties. Hybrid patternable materials produced by photopolymerisation processes have been mainly developed on 3-methacrloxypropyltrimethoxysilane based systems in which the polymerisable organic function is the CC bond of the methacrylic group. A new photosensitive hybrid material is described here, based on 3-glycidoxypropyltrimethoxysilane (GPTMS) and on the cationic photopolymerisation of the epoxide groups, which lead to the formation of a PEO organic interpenetrating network. 相似文献
764.
Roberto Maffei Facino Anna Sparatore Marina Carini Bruno Gioia Emanuele Arlandini Luigi Franzoi 《Journal of mass spectrometry : JMS》1991,26(11):951-955
The mass spectral fragmentation of echinacoside, a pharmacologically active caffeoyl-glycoside isolated from Echinacea angustifolia roots, has been investigated using different soft-ionization techniques, field desorption and fast atom bombardment (positive and negative ions) mass Spectrometry. Both ionization modes are successful in molecular mass determination and furnish approximately equivalent structural information. A fast atom bombardment tandem mass spectrometry approach (negative ions) was developed for the study of the fragmentation pathways and for the detection of echinacoside in crude plant extracts. The results demonstrate the usefulness of this technique for the rapid search of this important caffeoyl-glucoside directly in natural complex matrices. 相似文献
765.
Erben MF Della Védova CO Boese R Willner H Leibold C Oberhammer H 《Inorganic chemistry》2003,42(22):7297-7303
The geometric structure and conformational properties of trifluoromethyl chlorosulfonate (chlorosulfuric acid trifluoromethyl ester), CF(3)OSO(2)Cl, have been determined by X-ray crystallography, gas electron diffraction (GED), and vibrational spectroscopy (IR(gas), IR(matrix), and Raman(liquid)). These experimental investigations were supplemented by quantum chemical calculations (B3LYP with 6-311G* and 6-311+G(3df) basis sets). All experimental methods result in a single conformer with gauche orientation of the CF(3) group relative to the S[bond]Cl. The dihedral angle delta(COSCl) is determined to be 91.7(3) degrees in the crystal and 94(3) degrees in the gas phase. This dihedral angle corresponds to a near-eclipsed orientation of the O[bond]C relative to one of the S[double bond]O bonds (delta(CO[bond]SO) = -23.0(3) degrees and -21(3) degrees in the crystal and gas phase, respectively). 相似文献
766.
Scandale W Still DA Carnera A Della Mea G De Salvador D Milan R Vomiero A Baricordi S Dalpiaz P Fiorini M Guidi V Martinelli G Mazzolari A Milan E Ambrosi G Azzarello P Battiston R Bertucci B Burger WJ Ionica M Zuccon P Cavoto G Santacesaria R Valente P Vallazza E Afonin AG Baranov VT Chesnokov YA Kotov VI Maisheev VA Yaznin IA Afansiev SV Kovalenko AD Taratin AM Denisov AS Gavrikov YA Ivanov YM Ivochkin VG Kosyanenko SV Petrunin AA Skorobogatov VV Suvorov VM Bolognini D Foggetta L Hasan S 《Physical review letters》2007,98(15):154801
The volume reflection phenomenon was detected while investigating 400 GeV proton interactions with bent silicon crystals in the external beam H8 of the CERN Super Proton Synchrotron. Such a process was observed for a wide interval of crystal orientations relative to the beam axis, and its efficiency exceeds 95%, thereby surpassing any previously observed value. These observations suggest new perspectives for the manipulation of high-energy beams, e.g., for collimation and extraction in new-generation hadron colliders, such as the CERN Large Hadron Collider. 相似文献
767.
Maura Pellei Giancarlo Gioia Lobbia Riccardo Spagna 《Journal of organometallic chemistry》2006,691(8):1615-1621
New mono-, di- and tri-organotin(IV) derivatives containing the neutral bis(2-pyridylthio)methane ligand, [(pyS)2CH2] and tris(2-pyridylthio)methane ligand, [(pyS)3CH] have been synthesized from reaction with SnRnCl4−n (R = Me, nBu, Ph and Cy, n = 1-3) acceptors. Mono-nuclear adducts of the type {[(pyS)2CH2]RnSnCl4−n} and {[(pyS)3CH]RnSnCl4−n} have been obtained and characterized by elemental analyses, FT-IR, ESI-MS, multinuclear (1H and 119Sn) NMR spectral data. The 1H and 119Sn NMR and ESI-MS data suggest for the triorganotin(IV) derivatives a complete dissociation of the compounds in solution. The mono- and di-organotin(IV) derivatives show a greater stability in solution, and their spectroscopic data are in accordance with the existence of six-coordinated RSnCl3N2 or R2SnCl2N2 species. 相似文献
768.
Della Villa A Enoch S Tayeb G Pierro V Galdi V Capolino F 《Physical review letters》2005,94(18):183903
This Letter presents a study of the local density of states (LDOS) in photonic quasicrystals. We show that the LDOS of a Penrose-type quasicrystal exhibits small additional band gaps. Among the band gaps, some exhibit a behavior similar to that typical of photonic crystals, while others do not. The development of certain band gaps requires large-size quasicrystals. It is explained by the long-range interactions involved in their formation. Moreover, the frequencies where the band gaps occur are not necessarily explained using single scattering and should therefore involve multiple scattering. 相似文献
769.
Biancamaria Della Vecchia Giuseppe Mastroianni Szabados J 《Acta Mathematica Hungarica》2006,111(4):325-345
Summary We give error estimates for the weighted approximation of functions with singularities at the endpoints on the semiaxis by
some modifications of Sz\'asz--Mirakyan operators. To do so, we define a new weighted modulus of smoothness and prove its
equivalence to the weighted K-functional. Also, the class of functions for which the modified Sz\'asz--Mirakyan operator can be defined will be extended
to a much wider set than for the original operator. 相似文献
770.
Bertini L Greco C De Gioia L Fantucci P 《The journal of physical chemistry. A》2006,110(47):12900-12907
The valence electronic excited states of Fe2(CO)9 have been studied using the time-dependent density functional theory (TDDFT). Both tribridged D3h and monobridged C2v structures have been considered, and the structure of selected low-lying singlet and triplet excited states have been optimized on the basis of the TDDFT analytical gradient. Optimized excited-state geometries are used to obtain an insight into certain aspects of the Fe2(CO)9 photochemistry. The Fe2(CO)9 (D3h) first triplet and second singlet excited states are unbound with respect to dibridged Fe2(CO)8 + CO, and the first two monobridged Fe2(CO)9 (C2v) singlet states are unbound with respect to the Fe(CO)5 + Fe(CO)4 dissociation. These results are discussed in light of the experimental data available. 相似文献