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61.
Building on the method of Kantorovich majorants, we give convergence results and error estimates for the two-step Newton method for the approximate solution of a nonlinear operator equation. 相似文献
62.
Javier Ulises Ortiz MayoMartial Thomas Carole SaintoméPascale Clivio 《Tetrahedron》2003,59(37):7377-7383
The synthesis of a building block containing the photobiologically relevant cis-syn thymine cyclobutane photoproduct and its incorporation into oligonucleotides by the phosphoramidite-based solid-phase synthesis is reported. Compared to previous syntheses, this route is extremely short and allows such modified oligonucleotides to be easily available for biological studies. 相似文献
63.
The transposition of the molecular ions (ring contraction) of 2-decalones is demonstrated by a study of the [M–28]+˙ peak and its homologue in labelled products using ionization and appearance energy measurements, and mass analysed ion kinetic energy and collision induced dissociation spectra. 相似文献
64.
Pascale Tavarès Marek M. Kubicki Philippe Meunier Bernard Gautheron Gabriel Dousse Hélène Lavayssière Jacques Satgé 《Transition Metal Chemistry》1992,17(3):220-223
o-Thiatelluraphenylenezirconocene complexes were obtained in good yield by reaction of dilithiumo-benzenthiatelluride with zirconocene dichlorides. These compounds represent the first examples of heterodichalcogenaphenylene
bent metallocences. They were characterized by spectroscopic methods and the effect on the n.m.r. results of stepwise substitution
of one and two Te atoms for S is discussed.
X-ray crystal structure analysis was performed for one representative complex. The structure is very similar to that previously
reported for a diselenaphenylene complex, but the disorder observed for chalcogen atoms prevents an accurate comparison of
the geometrical parameters with other related compounds. 相似文献
65.
Soulard P Asselin P Cuisset A Aviles Moreno JR Huet TR Petitprez D Demaison J Freedman TB Cao X Nafie LA Crassous J 《Physical chemistry chemical physics : PCCP》2006,8(1):79-92
CHFClI is among the more favorable molecules for parity violation (PV) measurements in molecules. Despite the fact that calculated PV effects are two orders of magnitude smaller than in some organometallic compounds, CHFClI displays interesting features which could make possible a new experimental PV test on this molecule. Indeed, ultrahigh resolution spectroscopy using an ultrastable CO(2) laser is favored by several intrinsic properties of this molecule. For example, the high vapor pressure of CHFClI allows investigation by supersonic beam spectroscopy. Indeed, the spectroscopic constants have been accurately determined by microwave and millimetre wave spectroscopy. This is important for the subsequent selection of an appropriate absorption band of CHFClI that could be brought to co?ncide with the absorption of CO(2). Partially resolved (+)- and (-)-CHFClI enantiomers with respectively 63.3 and 20.5% ee's have been recently prepared and analyzed by molecular recognition using chiral hosts called cryptophanes. Finally, the S-(+)/R-(-) absolute configuration was ascertained by vibrational circular dichro?sm (VCD) in the gas phase. 相似文献
66.
Orlando R Torres FJ Pascale F Ugliengo P Zicovich-Wilson C Dovesi R 《The journal of physical chemistry. B》2006,110(2):692-701
The vibrational spectrum of the Si-free katoite hydrogarnet (116 atoms in the unit cell) has been calculated at the periodic ab initio quantum mechanical level with the CRYSTAL program, by using a Gaussian type basis set and the hybrid B3LYP Hamiltonian. The harmonic frequencies at the Gamma point have been obtained by diagonalizing the mass-weighted Hessian matrix, that is evaluated by numerical differentiation of the analytical first derivatives of the energy with respect to the atomic Cartesian coordinates. The parameters controlling the numerical differentiation, as well as the numerical integration of the exchange-correlation functional for the self-consistent field (SCF) calculation, are shown to affect the obtained frequencies by less than 3 cm-1. Before diagonalization, the dynamical matrix is transformed to a block diagonal form according to the irreducible representations of the point group, so that the 345 vibrational modes are automatically classified by symmetry. Various tools are adopted (graphical representation, isotopic substitution, "freezing" part of the unit cell) that permit a complete classification of normal modes and, in particular, an analysis of the modes in terms of simple models (octahedra modes, Ca modes, H stretching, bending, rotations). The harmonic OH stretching band (48 modes) is quite narrow (20 cm-1), indicating that the interaction among OH groups is very weak. As the OH stretching modes are known to be totally separable from the other modes and strongly anharmonic, the one-dimensional Schroedinger equation for the anharmonic oscillator is solved numerically for the two extreme situations, corresponding to the vibration of one decoupled OH and of all 48 OH groups moving in phase. The anharmonic frequencies are 3682 and 3673 cm-1, respectively, in good agreement with IR experiments (a single band at 3661 cm-1 with a width at half band height of 33 cm-1) and confirming that the interaction between OH groups is extremely weak. 相似文献
67.
De Giacomo A Dell'Aglio M Casavola A Colonna G De Pascale O Capitelli M 《Analytical and bioanalytical chemistry》2006,385(2):303-311
Double-pulse laser-induced plasma spectroscopy (DP-LIPS) is applied to submerged targets to investigate its feasibility for
elemental analysis. The role of experimental parameters, such as inter-pulse delay and detection time, has been discussed
in terms of the dynamics of the laser-induced bubble produced by the first pulse and its confinement effect on the plasma
produced by the second laser pulse. The analytical performance of this technique applied to targets in a water environment
are discussed. The elemental analysis of submerged copper alloys by DP-LIPS has been compared with conventional (single-pulse)
LIBS in air. Theoretical investigation of the plasma dynamics in water bubbles and open air has been performed. 相似文献
68.
Barrès AL El-Ghayoury A Zorina LV Canadell E Auban-Senzier P Batail P 《Chemical communications (Cambridge, England)》2008,(19):2194-2196
Complementary shapes of the neutral symmetrical halogen-bond bis-donor core and octahedral inorganic cluster core prevent halogen-bonded polymers developing in more than one direction, favouring further templating by conducting radical cation slabs and yielding an 8 : 1 : 1 phase formulation instead of n : 2 : 1, with a 2D net, or m : 3 : 1, with a pseudo-cubic architecture, which may in principle also be targeted. 相似文献
69.
Paolini J Tomi P Bernardini AF Bradesi P Casanova J Kaloustian J 《Natural product research》2008,22(14):1270-1278
The composition of the essential oil of Cistus albidus (L.) obtained from plants growing wild in Provence (France) has been investigated using GC-RI (RI = retention indices), GC/MS and (13)C-NMR. Eighty-eight components were reported accounting for 81.8% of the essential oil. This essential oil was characterized by a high content of sesquiterpenes with alpha-zingiberene (12.8%), alpha-curcumene (7.7%), (E)-beta-caryophyllene (5.9%), alpha-cadinol (5.4%), alpha-bisabolol (4.1%), caryophyllene oxide (3.8%), allo-aromadendrene (3.4%), delta-cadinene (3.4%), and germacrene D (3.1%) being the main components. 相似文献
70.
Poisson L Roubin P Coussan S Soep B Mestdagh JM 《Journal of the American Chemical Society》2008,130(10):2974-2983
The dynamics of the enolic form of acetylacetone (E-AcAc) was investigated using a femtosecond pump-probe experiment. The pump at 266 nm excited E-AcAc in the first bright state, S2(pi pi*). The resulting dynamics was probed by multiphoton ionization at 800 nm. It was investigated for 80 ps on the S2(pi pi*) and S1(n pi*) potential energy surfaces. An important step is the transfer from S2 to S1 that occurs with a time constant of 1.4 +/- 0.2 ps. Before, the system had left the excitation region in 70 +/- 10 fs. An intermediate step was identified when E-AcAc traveled on the S2 surface. Likely, it corresponds to an accidental resonance in the detection scheme that is met along this path. More importantly, some clues are given that an intramolecular vibrational energy relaxation is observed, which transfers excess vibrational energy from the enolic group O-H to the other modes of the molecule. The present multistep evolution of excited E-AcAc probably also describes, at least qualitatively, the dynamics of other electronically excited beta-diketones. 相似文献