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171.
Santiago PS Neto Dde S Gandini SC Tabak M 《Colloids and surfaces. B, Biointerfaces》2008,65(2):247-256
Fluorescence quenching of meso-tetrakis-4-sulfonatophenyl (TPPS(4)) and meso-tetrakis-4-N-methylpyridil (TMPyP) porphyrins is studied in aqueous solution and upon addition of micelles of sodium dodecylsulfate (SDS), cetyltrimethylammonium chloride (CTAC), N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and t-octylphenoxypolyethoxyethanol (Triton X-100). Potassium iodide (KI) was used as quencher. Steady-state Stern-Volmer plots were best fitted by a quadratic equation, including dynamic (K(D)) and static (K(S)) quenching. K(S) was significantly smaller than K(D). Frequency-domain fluorescence lifetimes allowed estimating bimolecular quenching constants, k(q). At 25 degrees C, in aqueous solution, TMPyP shows k(q) values a factor of 2-3 higher than the diffusional limit. TPPS(4) shows collisional quenching with pH dependent k(q) values. For TMPyP quenching results are consistent with reported binding constants: a significant reduction of quenching takes place for SDS, a moderate reduction is observed for HPS and almost no change is seen for Triton X-100. Similar data were obtained at 50 degrees C. For CTAC-TPPS(4) system an enhancement of quenching was observed as compared to pure buffer. This is probably associated to accumulation of iodide at the cationic micellar interface. The attraction between CTAC headgroups and I(-), and repulsion between SDS and I(-), enhances and reduces the fluorescence quenching, respectively, of porphyrins located at the micellar interface. The small quenching of TPPS(4) in Triton X-100 is consistent with strong binding as reported in the literature. 相似文献
172.
Aline de Souza Ramos Joyce Benzaquem Ribeiro Leonardo Vazquez Selma Gomes Ferreira Leite Francisco Radler de Aquino Neto 《Tetrahedron letters》2009,50(52):7362-6129
The enantioselective reduction of ethyl benzoylacetate (EBA) into ethyl (S)-3-hydroxy-3-phenylpropanoate (S-HPPE) by nine yeast strains and three filamentous fungi strains is described. The conversion obtained was in the range 0-89% and the enantiomeric excess was 100% in many cases. Conversion levels were higher when the reduction was performed with microorganisms immobilized in calcium alginate and enantioselectivity remained excellent. Some reaction’s conditions of bioreduction by immobilized cells of Rhodotorula rubra were studied using a 25-2 fractional factorial design. 相似文献
173.
174.
Melyna Chaves Leite-Andrade Luiz Nascimento de Araújo Neto Maria Daniela Silva Buonafina-Paz Franz de Assis Graciano dos Santos Adryelle Idalina da Silva Alves Maria Carolina Accioly Brelaz de Castro Edna Mori Bruna Caroline Gonalves Vasconcelos de Lacerda Isaac Moura Araújo Henrique Douglas Melo Coutinho Grayna Kowalska Radosaw Kowalski Tomasz Baj Rejane Pereira Neves 《Molecules (Basel, Switzerland)》2022,27(24)
Yeasts from the Candida parapsilosis complex are clinically relevant due to their high virulence and pathogenicity potential, such as adherence to epithelial cells and emission of filamentous structures, as well as their low susceptibility to antifungals. D-limonene, a natural compound, emerges as a promising alternative with previously described antibacterial, antiparasitic, and antifungal activity; however, its mechanisms of action and antivirulence activity against C. parapsilosis complex species have not been elucidated. Therefore, in the present study, we aimed to evaluate the antifungal and antivirulence action, as well as the mechanism of action of D-limonene against isolates from this complex. D-limonene exhibited relevant antifungal activity against C. parapsilosis complex yeasts, as well as excellent antivirulence activity by inhibiting yeast morphogenesis and adherence to the human epithelium. Furthermore, the apoptotic mechanism induced by this compound, which is not induced by oxidative stress, represents an important target for the development of new antifungal drugs. 相似文献
175.
Michael O’Carroll Paulo A. Faria da Veiga Antônio Francisco Neto 《Communications in Mathematical Physics》2013,321(1):249-282
We consider a lattice SU(3) QCD model in 2 + 1 dimensions, with two flavors and 2 × 2 spin matrices. An imaginary time functional integral formulation with Wilson’s action is used in the strong coupling regime, i.e. small hopping parameter ${0 < \kappa \ll 1}$ , and much smaller plaquette coupling ${\beta, 0 < \beta \ll \kappa}$ . In this regime, it is known that the low-lying energy-momentum spectrum contains isolated dispersion curves identified with baryons and mesons with asymptotic masses ${m\approx-3\ln\kappa}$ and ${m_m\approx-2\ln\kappa}$ , respectively. We prove the existence of two (labelled by ±) two-baryon bound states for each of the total isospin sectors I = 0,1 and we obtain, in each case, the exact binding energies ${\epsilon_{I\,\pm} }$ (of order ${\kappa^2}$ ) which extend to jointly analytic function in ${\kappa}$ and β. We also prove that these points are the only mass spectrum up to slightly above the bound state masses. Precisely, we show, for ${\alpha_0=\frac 14, \alpha_1=\frac 1{12}, \alpha_2=\frac12, \alpha_3=\frac 34}$ and small ${\delta >0 }$ , that the bound state masses ${2m-\epsilon_{I\,\pm}}$ are the only points in the mass spectrum in ${(0,2m-\epsilon_{I\,\pm}+\delta \alpha_I\kappa^2)}$ , for I = 0,1, and in ${(0,2m-(1+\delta)\alpha_I\kappa^2)}$ , for I = 2,3. These results are exact and validate our previous results obtained in a ladder approximation. The method employs suitable two- and four-point correlations with spectral representations and a lattice Bethe-Salpeter equation. For I = 0,1, a quark, antiquark space-range one potential of order ${\kappa^2}$ is found to be the dominant contribution to the two-baryon interaction and the interaction of the individual quark isospins of one baryon with those of the other is described by permanents. A novel spectral free decomposition (but spectral representation motivated, for real κ and β) of the two-point correlation, after performing a complex extension, is a key ingredient in showing the joint analyticity of the binding energy. 相似文献
176.
177.
Carlos B. da Silva Pedro Neto José C. F. Pereira 《Theoretical and Computational Fluid Dynamics》2009,23(4):287-296
Direct and large-eddy simulations (DNS/LES) of accelerating round jets are used to analyze the effects of acceleration on
the kinematics of vortex rings in the near field of the jet (x/D < 12). The acceleration is obtained by increasing the nozzle jet velocity with time, in a previously established (steady)
jet, and ends once the inlet jet velocity is equal to twice its initial value. Several acceleration rates (α = 0.02–0.6) and Reynolds numbers (Re
D
= 500–20000) were simulated. Acceleration maps were used to make a detailed study of the kinematics of vortex rings in accelerating
jets. One of the effects of the acceleration is to cause a number of new primary and secondary vortex merging events that
are absent from steady jets. As the acceleration rate α increases, both the number of primary merging events between rings
and the axial position where these take place decreases. The statistics for the speed of the starting ring that forms at the start of the acceleration phase for each simulation, agree well with the statistics for the “front” speed
observed by Zhang and Johari (Phys Fluids 8:2185–2195, 1996). Acceleration maps and flow visualizations show that during the
acceleration phase the near field coherent vortices become smaller and are formed at an higher frequency than in the steady
jet, and their (mean) shedding frequency increases linearly with the acceleration rate. Finally, it was observed that the
acceleration decreases the spreading rate of the jet, in agreement with previous experimental works.
相似文献
178.
The limitation of macroscopic models to represent structural parameters, such as topology and morphology, as well as population effects, i.e. multi-molecules movement, in the modeling of chromatography systems has implications on the understanding of the phenomenological aspects that contribute to the separation mechanisms in porous media. The representation of the porous structure of chromatographic columns by a three-dimensional cubic network of interconnected sites allows a better analysis of the structural characteristics of the porous column and its connection with the phenomena of adsorption, diffusion and convection. In the present work the application of an interconnected cubic network model associated with a stochastic modeling of the adsorption, diffusion and convection phenomena leads to the proper representation of the dynamic aspects of the breakthrough curves related to separation processes in chromatographic columns. Therefore, it is possible to study the dynamics of solute retention from the molecules distribution in the separation processes throughout the column. Among the mass transfer mechanisms investigated, the convection showed to be closely related to the separation dynamics of chromatography, with the diffusion having little effects. The adsorption influenced both the separation dynamics and solute retention. 相似文献
179.
Freire CS Silvestre AJ Pascoal Neto C Gandini A Fardim P Holmbom B 《Journal of colloid and interface science》2006,301(1):205-209
The topochemistry of the controlled heterogeneous esterification of cellulose fibers with fatty acid chlorides of different chain length, both in swelling and non-swelling media, was assessed by X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and contact angle measurements. On the one hand, the results provided by the combined use of these three powerful techniques showed unambiguously the occurrence of the reaction at the fibers' surface and, on the other hand, the XPS results showed that the surface coverage with the fatty acid moieties increased with their chain length, but was only modestly affected by the degree of substitution (DS), suggesting that when the esterification yield was increased (higher DS values), an in-depth reaction also occurred, particularly when DMF was used as a cellulose swelling medium, involving the OH groups buried below the fibers' surface. 相似文献
180.
Marcio Colombo Fenille Oziride Manzoli Neto 《Central European Journal of Mathematics》2010,8(3):421-429
Given a model 2-complex K
P
of a group presentation P, we associate to it an integer matrix Δ
P
and we prove that a cellular map f: K
P
→ S
2 is root free (is not strongly surjective) if and only if the diophantine linear system Δ
P
Y = $
\overrightarrow {deg}
$
\overrightarrow {deg}
(f) has an integer solution, here $
\overrightarrow {deg}
$
\overrightarrow {deg}
(f)is the so-called vector-degree of f 相似文献