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181.
Interest in nanofibrillated cellulose has been increasing exponentially because of its relatively ease of preparation in high yield, high specific surface area, high strength and stiffness, low weight and biodegradability etc. This bio-based nanomaterial has been used mainly in nanocomposites due to its outstanding reinforcing potential. Solvent casting, melt mixing, in situ polymerization and electrospinning are important techniques for the fabrication of nanofibrillated cellulose-based nanocomposites. Due to hydrophilic character along with inherent tendency to form strong network held through hydrogen-bonding, nanofibrillated cellulose cannot uniformly be dispersed in most non-polar polymer matrices. Therefore, surface modification based on polymer grafting, coupling agents, acetylation and cationic modification was used in order to improve compatibility and homogeneous dispersion within polymer matrices. Nanofibrillated cellulose opens the way towards intense and promising research with expanding area of potential applications, including nanocomposite materials, paper and paperboard additive, biomedical applications and as adsorbent. 相似文献
182.
183.
Poli T Chiantore O Giovagnoli A Piccirillo A 《Analytical and bioanalytical chemistry》2012,402(9):2977-2984
The study of polished cross sections is a well-assessed and practical method to investigate the stratigraphy of paintings
and multilayer polychromies on works of art, in general. Analyses on cross sections allow us to characterize, at once, all
the layers in the stratigraphy, giving information about the artists technique, the number of layers and their composition
and sometimes about the conservation history of the artefact. In this paper, the application of an imaging detector focal
plane array (FPA) coupled to an infrared (IR) microscope has been studied, focusing on the characteristics and potential of
the different working methodologies (attenuated total reflectance (ATR) and total reflection). FPA detector coupled with ATR
crystal can “localize” IR information coming from a 30 × 30μm sample area, in a 64 × 64 dot matrix detector. In particular,
an innovative analysis methodology has been tested for the total reflectance measurements in order to obtain maximum information
with single measurements. Micro-infrared total reflection measurements have been carried out in an extended IR range (from
1,000 to 5,266 cm−1) exploiting the broad spectral response of mercury cadmium telluride detector in order to include overtones and combination
bands from near-infrared spectral range without any modification of the standard mid-infrared micro-FT instrumentation. The
potentialities of this new approach have been successfully transferred in the imaging/mapping investigations with a minimal
tuning of the apparatus. Results obtained on a polished cross section coming from a modern painting and on a micro-sample
of a wood polychromy from an undated historic polyptic are shown for demonstration. 相似文献
184.
Tedeschi A Auriemma F Ricciardi R Mangiapia G Trifuoggi M Franco L Rosa CD Heenan RK Paduano L D'Errico G 《The journal of physical chemistry. B》2006,110(46):23031-23040
Surfactant-containing poly(vinyl alcohol) (PVA) cryogels have been prepared by drying and reswelling hydrogel patches, previously obtained by the freeze/thaw procedure, in decyltrimethylammonium bromide (C10TAB) aqueous solutions. The microstructural and diffusive properties of the resulting material have been characterized by a combined experimental strategy. Gravimetric measurements show that the cryogel maximum swelling is not affected by the surfactant. The surfactant concentration within the cryogel, measured by ion chromatography, is the same as that in the rehydrating surfactant solution. Electron paramagnetic resonance (EPR) spin-probe and small-angle neutron scattering (SANS) measurements show that surfactant self-aggregation in the gel is similar to that in water, occurring at the same critical concentration and resulting in the formation of micellar aggregates whose structure is not affected by the cryogel polymeric scaffold. However, both the micelle intradiffusion coefficients, measured by PGSE-NMR, and the spin-probe correlation times, measured by EPR, indicate that dynamic processes in the hydrogel are much slower than in bulk water. A quantitative analysis of these results suggests that the cryogel polymer-poor domains, in which surfactant molecules are solubilized, have an average dimension of approximately 0.1 microm. Interestingly the experimental data also show that the polymer-poor phase contains more polymer than expected, suggesting that the spinodal decomposition, which occurs during the freezing step of cryogel preparation, is not complete or prevented by ice formation. 相似文献