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171.
Francesco Trotta Katia Martina Bruna Robaldo Alessandro Barge Giancarlo Cravotto 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):3-7
We describe improved syntheses of CD derivatives, like 6I-monotosyl, 6I-monoazido-6I -monodeoxy, 6I-monoamino-6I-monodeoxy-βCD and 2I-O-mono(methylamino)alkyl-βCDs, that were carried out under US or MW, to great advantage in terms of yield, purity and reaction
time. In the search for more efficient procedures to prepare monosubstituted CDs, we applied MW and/or US to some fundamental
preparations such as those of 6I-amino-6I-deoxy-βCD and a series of 2-monoaminomethyl-βCD derivatives. 相似文献
172.
Joaquim Bruna Artur Nicolau Knut Ø yma 《Proceedings of the American Mathematical Society》1996,124(4):1197-1204
In this note we formulate and solve a natural interpolation problem for the Hardy spaces in the unit disc in terms of maximal functions and weighted summable sequences.
173.
Lago JH Souza ED Mariane B Pascon R Vallim MA Martins RC Baroli AA Carvalho BA Soares MG dos Santos RT Sartorelli P 《Molecules (Basel, Switzerland)》2011,16(12):9827-9837
The chemical composition and antimicrobial activity of essential oils obtained from leaves of two Myrtaceae species-Eugenia uniflora L. and Plinia trunciflora (O. Berg) Kausel-were determined. Analysis by GC/MS as well as determination of Kovatz indexes indicated atractylone (26.78%) and curzerene (17.96%) as major constituents of E. uniflora oil and α-cadinol (19.15%), apiole (11.15%) and cubenol (5.43%) as main components in P. trunciflora oil. Both essential oils were tested for antimicrobial activity against yeasts and bacteria. E. uniflora and P. trunciflora essential oils were active towards two Gram-positive bacteria, Streptococcus equi and Staphylococcus epidermis. In addition, biological activity of both essential oils was detected for pathogenic yeasts of the genus Candida and Cryptococcus. E. uniflora was active towards all yeast tested and exhibited interesting minimal inhibitory concentrations (0.11 to 3.75 mg/mL) across a broad spectrum of activity. 相似文献
174.
[18-Crown-6 Na](2)S(2)O(4) complex was prepared in methanol solution but dissociates into 18-Crown-6 ((s)) and Na(2)S(2)O(4 (s)) on removal of the solvent. Evidence for complexation in methanol is supported by a quantitative mass analysis and the dissociation in the solid state by vibrational spectroscopy and powder X-ray diffraction. These observations are accounted for by investigating the energetics of complexation in solution and dissociation in the solid state using calculated density functional theory (DFT) gas phase binding enthalpies and free energies combined with conductor-like screening model (COSMO) solvation energies and lattice enthalpy and free energy terms derived from volume based thermodynamics (VBT). Our calculations show that complexation of alkali metal dianion salts to crown ethers are much less favorable than that of the corresponding monoanion salts in the solid state and that the formation of alkali metal crown complexes of stable simple oxy-dianion (e.g., CO(3)(2-), SO(4)(2-)) salts is unlikely. The roles of complexation with 18-Crown-6 and ion pair formation in the process of dissolution of Na(2)S(2)O(4) to methanol are discussed. 相似文献
175.
de Oliveira FM Somera BF Corazza MZ Yabe MJ Segatelli MG Ribeiro ES Lima EC Dias SL Tarley CR 《Talanta》2011,85(5):2417-2424
The present paper describes the synthesis of a new chemically modified cellulose microfiber through oxidation with sodium periodate and functionalization with N,N′-bis (2-aminoethyl)-1,2-ethanediamine for the fast and selective preconcentration of Cd(II) ions in flow system analysis. The new sorbentsorbent was characterized by FTIR, SEM, and surface area values. The uptake behavior of Cd(II) ions onto this sorbent was evaluated from kinetic data, pseudo-first-order and pseudo-second-order models, as well as from Langmuir, Freundlich and Langmuir-Freundlich adsorption isotherms. The maximum sorption capacity of 4.59 mg g−1 was estimated by the Langmuir-Freundlich model with fast kinetics for the sorption of Cd(II) described by the pseudo-second-order kinetic model. After characterization, the sorbent was packed in a mini-column, and a fast flow injection preconcentration system for Cd(II) determination by FAAS was developed. The best Cd(II) preconcentration condition, obtained by means of factorial design and response surface methodology, was achieved at pH 9.36 and a flow rate of 10 mL min−1 followed by elution with 1.0 mol L−1 nitric acid. By using 78 s preconcentration time, fast and highly sensitive determination of Cd(II) ions could be achieved with a limit of quantification of 0.20 μg L−1, preconcentration factor of 26, consumption index of 0.5 mL, concentration efficiency of 20 min−1, and sample throughput of 39 h−1. The repeatability for 10 replicate determinations was found to be 7.8 and 2.5% for Cd(II) ion concentrations of 5.0 and 100.0 μg L−1, respectively. The new sorbent efficiency for the interference-free preconcentration of Cd(II) ions was assessed by analysis of tap, mineral and lake waters, as well as synthetic seawater and normal saline waters. Furthermore, complex samples, such as biological samples, could be analysed by the proposed method in accordance with the accuracy attested by analysis of certified reference materials, TORT-2 (lobster hepatopancreas), and DOLT-4 (dogfish liver). 相似文献
176.
The aim of this work is to show the application of shape and parametric optimization techniques in the study of reactive silencers with extended inlet and outlet ducts. Parametric optimization is employed to evaluate the appropriate size of the inlet and outlet ducts. Shape optimization is employed to establish the proper profile of these ducts in order to improve the acoustic features of these mufflers in a specific frequency range. The objective function used in the optimization processes is defined through the average transmission loss (TL) for the desired frequency range. This type of objective function is strongly non-linear and the genetic algorithm, GA, was chosen as a mathematical method for determining the maximum of this function. The Finite Element Method with an axisymmetric formulation along with the modified four-parameter method are used to calculate the TL(ω). The Hermite polynomials were used in the shape optimization in order to obtain local boundary approximations with C1 continuity. The results showed the optimization efficiency of the inlet ducts profile for acting in specific frequency ranges with gains up to 20 dB with respect to silencers without shape optimization. The numerical analyses agree well with experimental results. 相似文献
177.
Rother W Dewald A Iwasaki H Lenzi SM Starosta K Bazin D Baugher T Brown BA Crawford HL Fransen C Gade A Ginter TN Glasmacher T Grinyer GF Hackstein M Ilie G Jolie J McDaniel S Miller D Petkov P Pissulla T Ratkiewicz A Ur CA Voss P Walsh KA Weisshaar D Zell KO 《Physical review letters》2011,106(2):022502
The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space. 相似文献
178.
Pablo J. Bruna 《Molecular physics》2013,111(3):429-446
Theoretical calculations on the fine, hyperfine and Zeeman (g-factor) parameters are reported for the X2Π and A2Σ+ states of FH+, ClH+ and BrH+. The fine-structure constants [spin–orbit (A), Λ-doubling (p, q) and spin–rotation constants (γ Π, γ Σ)] are evaluated up to second order (via SO/L couplings with several excited states) using a multireference configuration interaction (MRCI) method, a Breit–Pauli Hamiltonian and 6-311++(2d,2pd) basis sets. Hyperfine constants of magnetic and electric type [Frosch–Foley (a, b, c, d) and nuclear quadrupole (eQq 0, eQq 2)] are studied with density functional methods and various basis sets. Magnetic dipole moments (parameterized via g-factors) are calculated in second order like the fine structure constants. The situation is somewhat complex for X2Π since no less than five different g’s have to be evaluated in second order. In general, our results are in good agreement with those reported in the literature, mostly limited to the ground state. Our calculations confirm that, at equilibrium, all second-order properties are dominated by the couplings between the electronic states X and A. 相似文献
179.
A model of microstructure development for phase transformations driven by nucleation and growth is presented. The model is based on a set of Fokker-Planck-like equations which allows us to compute the particle grain density distribution at any time during the transformation, provided that the nucleation and growth dependences on time and/or grain radius are known. The model is applicable to any kind of nucleation and growth protocols fulfilling the Johnson–Mehl–Avrami–Kolmogorov conditions, namely spatially random nucleation and isotropic growth. Comparison with stochastic (Monte Carlo) simulations is presented, giving quantitative agreement in all cases. This work shows the relationship between kinetic parameters and microstructure evolution as well as the accuracy of the developed model. 相似文献
180.
Liana Sanches-Rocha Bruna Serpa Eduardo Figueiredo Nelson Hamerschlak Ronaldo Baroni 《Magnetic resonance imaging》2013