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691.
692.
A filtration procedure was developed to measure the reversibility of fouling during cross-flow filtration based on the square wave of applied pressure. The principle of this method, the apparatus required, and the associated mathematical relationships are detailed. This method allows for differentiating the reversible accumulation of matter on, and the irreversible fouling of, a membrane surface. Distinguishing these two forms of attachment to a membrane surface provides a means by which the critical flux may be determined. To validate this method, experiments were performed with a latex suspension at different degrees of destabilization (obtained by the addition of salt to the suspension) and at different cross-flow velocities. The dependence of the critical flux on these conditions is discussed and analysed through the osmotic pressure of the colloidal dispersion. 相似文献
693.
The aim of the present study was to characterize pegylated nanoparticles (NPs) for their microporosity and study the effect of microporosity on drug release kinetics. Blank and drug-loaded NPs were prepared from three different pegylated polymers, namely, poly(ethylene glycol)1%-graft-poly(D,L)-lactide, poly(ethylene glycol)5%-graft-poly(D,L)-lactide, and the multiblock copolymer (poly(D,L)-lactide-block-poly(ethylene glycol)-block-poly(D,L)-lactide)n. These NPs were characterized for their microporosity using nitrogen adsorption isotherms. NPs of the multiblock copolymer showed the least microporosity and Brunauer-Emmett-Teller (BET) surface area, and that of PEG1%-g-PLA showed the maximum. Based on these results, the structural organization of poly(D,L)-lactide (PLA) and poly(ethylene glycol) (PEG) chains inside the NPs was proposed and was validated with differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS) surface analysis. An in vitro drug release study revealed that PEG1%-g-PLA NPs exhibited slower release despite their higher surface area and microporosity. This was attributed to the presence of increased microporosity forming tortuous internal structures, thereby hindering drug diffusion from the matrix. Thus, it was concluded that the microporous structure of NPs, which is affected by the molecular architecture of polymers, determines the release rate of the encapsulated drug. 相似文献
694.
Rousseau A Pedrini M Chiap P Ivanyi R Crommen J Fillet M Servais AC 《Electrophoresis》2008,29(17):3641-3648
A nonaqueous capillary electrophoresis (NACE) assay was developed for the separation and determination of flurbiprofen enantiomers in plasma samples using 6-monodeoxy-6-mono(3-hydroxy)propylamino-beta-cyclodextrin as chiral selector. The nonaqueous background electrolyte was made up of 40 mM ammonium acetate in methanol (MeOH), and flufenamic acid was employed as internal standard. Solid-phase extraction was used for sample cleanup prior to the NACE separation. The NACE method reproducibility was optimized by evaluating different capillary washing sequences between runs. After having tested various conditions, trifluoroacetic acid (1 M) in MeOH was finally selected. Concerning the solid-phase extraction procedure, good and reproducible analyte recoveries were obtained using MeOH for protein denaturation and a polymeric phase combining hydrophobic interactions with anion exchange properties (Oasis) MAX) was selected as extraction sorbent. The method selectivity was not only demonstrated toward a blank plasma sample but also toward other non-steroidal anti-inflammatory drugs. The method was then successfully validated with respect to response function, trueness, precision, accuracy, linearity and limit of quantification. 相似文献
695.
696.
Ivana uri
kovi Rmy Claverie Patrice Bourson Mario Marchetti Jean‐Marie Chassot Marc D. Fontana 《Journal of Raman spectroscopy : JRS》2011,42(6):1408-1412
Raman spectroscopy was used to study the liquid–solid water phase transition. Special attention was devoted to the OH stretching band of the Raman spectrum, which shows monotonous changes in the temperature range between 10 and − 15 °C. The interpretation of this spectral change, as well as a careful analysis of its integrated scattered intensity, led to a spectral marker that allows the determination of the water phase (liquid or solid), and the efficient identification of the liquid–solid phase transition itself. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
697.
Morlière P Patterson LK Santos CM Silva AM Mazière JC Filipe P Gomes A Fernandes E Garcia MB Santus R 《Organic & biomolecular chemistry》2012,10(10):2068-2076
The flavonoid quercetin is known to reduce the α-tocopheroxyl radical (˙TocO) and reconstitute α-tocopherol (TocOH). Structurally related polyphenolic compounds, hydroxy-2,3-diarylxanthones (XH), exhibit antioxidant activity which exceeds that of quercetin in biological systems. In the present study repair of ˙TocO by a series of these XH has been evaluated using pulse radiolysis. It has been shown that, among the studied XH, only 2,3-bis(3,4-dihydroxyphenyl)-9H-xanthen-9-one (XH9) reduces ˙TocO, though repair depends strongly on the micro-environment. In cationic cetyltrimethylammonium bromide (CTAB) micelles, 30% of ˙TocO radicals are repaired at a rate constant of ~7.4 × 10(6) M(-1) s(-1) by XH9 compared to 1.7 × 10(7) M(-1) s(-1) by ascorbate. Water-soluble Trolox (TrOH) radicals (˙TrO) are restored by XH9 in CTAB (rate constant ~3 × 10(4) M(-1) s(-1)) but not in neutral TX100 micelles where only 15% of ˙TocO are repaired (rate constant ~4.5 × 10(5) M(-1) s(-1)). In basic aqueous solutions ˙TrO is readily reduced by deprotonated XH9 species leading to ionized XH9 radical species (radical pK(a) ~10). An equilibrium is observed (K = 130) yielding an estimate of 130 mV for the reduction potential of the [˙X9,H(+)/XH9] couple at pH 11, lower than the 250 mV for the [˙TrO,H(+)/TrOH] couple. A comparable value (100 mV) has been determined by cyclic voltammetry measurements. 相似文献
698.
Lanoë PH Gallavardin T Dupin A Maury O Baldeck PL Lindgren M Monnereau C Andraud C 《Organic & biomolecular chemistry》2012,10(31):6275-6278
A molecular engineering strategy based on rational variations of the bromine substitution pattern in two-photon absorbing singlet oxygen sensitizers allows studying the relations that exist between the positioning of an inter-system crossing promoter on the charge-transfer chromophore and its ability to generate singlet oxygen. 相似文献
699.
Kaminska I Das MR Coffinier Y Niedziolka-Jonsson J Woisel P Opallo M Szunerits S Boukherroub R 《Chemical communications (Cambridge, England)》2012,48(9):1221-1223
A one step process for simultaneous reduction and functionalization of graphene oxide using tetrathiafulvalene (TTF) is described. Chemical oxidation of TTF to TTF(2+) using an aqueous solution of Fe(ClO(4))(3) expels the charged molecule from the graphene nanosheets, while subsequent immersion in neutral TTF solution allows the capture of the TTF molecules. 相似文献
700.
[structure: see text] A convergent and rapid stereoselective synthesis of (-)-spongidepsin has been achieved from the Roche ester in 14 steps with an overall yield of 13%. 相似文献