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The properties of boron nitride (BN), boron phosphide (BP), aluminum nitride (AlN), and aluminum phosphide (AlP) nanocones were investigated by density functional theory (DFT) calculations. The investigated structures were optimized and chemical shielding (CS) properties including isotropic and anisotropic CS parameters were calculated for the atoms of the optimized structures. The magnitudes of CS parameters were observed to be mainly dependent on the bond lengths of considered atoms. The results indicated that the atoms could be divided into atomic layers due to the similarities of their CS properties for the atoms of each layer. The trend means that the atoms of each layer detect almost similar electronic environments. Moreover, the atoms at the apex and mouth of nanocones exhibit different properties with respect to the other atomic layers. 相似文献
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A detailed study is undertaken to analyze the two-dimensional transient fluid-structure interaction of a plane acoustic pressure
pulse with an arbitrarily thick, isotropic, functionally graded, hollow cylinder of infinite length, submerged in and filled
with non-viscous compressible fluids. A laminate approximate model is adopted to deal with the assumed power-law variation
of the constituents’ volume fractions across the thickness of the inhomogeneous cylinder. The problem solution is obtained
by employing the classical method of modal expansion in conjunction with the powerful Transfer matrix solution technique and
Durbin’s numerical Laplace inversion algorithm. Detailed numerical examples for the transient responses of water-filled and
submerged thick-walled TiC-Al FGM cylinders with ceramic or metal rich material compositional gradient profiles under wideband
and narrowband Gaussian incident shock loadings are presented and discussed. Many of the interesting dynamic features in the
transient shell-shock interaction are addressed through appropriate plots of the internal/external pressure field as well
as the induced dynamic stress concentrations within the shell material. Also, the response curves for the FGM cylinders are
compared with those of equivalent bi-laminate shells containing comparable total volume fractions of constituent materials.
A limiting case is considered and the validity of the work is established by comparison with the data obtained with the aid
of a commercial finite element package. 相似文献
87.
In this paper of a two-paper series a new method is proposed for the analysis and assessment of fatigue crack closure phenomena. Based on the proposed model, the combined effect of residual plastic stretch, asperity mismatch, and corrosion debris on the closure behavior of a fatigue crack can be simulated by a hypothetical rigid insert located in an ideal crack wake. The formulation of the model results in a set of equations which can predict the closure load as well as the load-CMOD characteristics using the residual CMOD at zero load as a unique experimental input. The model is verified using different sets of experimental data reported in the literature. 相似文献
88.
Kobra?Hasanirokh Jafar?Azizi Arash?PhirouzniaEmail author Hakimeh?Mohammadpour 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(4):95
In the current work, based on a semiclassical Boltzmann approach, we have investigatedthe influence of the Rashba spin-orbit coupling on spin-current of a single layer gappedgraphene. It was shown that the Rashba coupling plays a considerable role in thegeneration of the spin-current of vertical spins in mono-layer graphene. The behavior ofthe spin-current is determined by the density of impurities. It was also shown that thespin-current of the system could increase by increasing the Rashba coupling strength andband-gap of the graphene and the sign of the spin-current could be controlled by thedirection of the current-driving electric field. 相似文献
89.
The reaction of dialkyl acetylenedicarboxylates with alkyl 2‐[3‐oxo‐3,4‐dihydro‐2(1H)‐quinoxadinylidene]ethanoates in the presence of triphenylphosphine leads to trialkyl (E)‐3‐{3‐oxo‐2‐3,4‐dihydro‐2‐(1H)‐quinoxalinylidene}‐prop‐1‐ene‐1,2,3‐tricarboxylates in good yields. 相似文献
90.
Hossein Fakhraian Akbar Mirzaei 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):511-518
A liquid–liquid phase-transfer-catalyzed (PTC) Michaelis-Becker reaction was adopted in the preparation of dialkyl methyl phosphonate (R = Me, iPr, nBu, and iBu). This was performed by the reaction of an appropriate dialkyl hydrogen phosphonate with methyl iodide in the presence of benzyl triethyl ammonium chloride and sodium hydroxide as PTC and base, respectively. A liquid–liquid two-phase system (H2O/CH2Cl2) introduced a suitable situation for the preparation of dialkyl methyl phosphonates with bulky alkyl groups (R = iPr, nBu, and iBu), but with R = Me, the hydrolysis of dimethyl hydrogen phosphonate (reagent) reduced the yield to 22%. In this case, a solid–liquid PTC-free system was successfully applied and yield of over 80% was obtained. 相似文献