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51.
In the presence of acetic anhydride, both sodium perborate and sodium percarbonate have been found to be effective reagents for the oxidation of α-phenylselenocarbonyl compounds to α,β,-unsaturated carbonyl compounds. 相似文献
52.
A series of resorcinarene glycol derivatives have been synthesized as secondary substitution products via a Mannich reaction catalyzed by iminodiacetic acid. The products are potentially useful candidates as podands for supramolecular chemistry. The synthesis presented in this article is effective and uses readily available and inexpensive substrates. 相似文献
53.
Ioannis Tsivintzelis Georgios Koutsou Georgios M. Kontogeorgis 《Molecules (Basel, Switzerland)》2022,27(18)
The CPA equation of state is applied to model binary, ternary, and multicomponent mixtures that contain CO2 with polyethylene glycols or compounds relevant to biodiesel production, such as glycerol and various triglycerides. Effort has been made to evaluate the model performance on correlating both the liquid and the vapor phase compositions, which is a demanding task, revealing the model’s and parameters’ limitations, due to the rather low concentrations of heavy compounds in the vapor phase. Initially the model’s binary parameters, which in all cases were temperature independent, were estimated using experimental data for binary systems. Those parameters were used to predict the phase behavior of supercritical CO2 containing ternary and multicomponent mixtures. Since no parameter was adjusted to ternary or multicomponent systems’ data, the reported CPA results for such mixtures are considered as pure predictions. This is the final part of a series of studies [Tsivintzelis et al. Fluid Phase Equilibria 430 (2016) 75–92 and 504 (2020) 112337] that complete the parameterization of the CPA equation of state for systems relevant to the biodiesel production, which allows the application of the model to multicomponent mixtures of the relevant processes. 相似文献
54.
测定了水溶性高分子聚乙二醇(PEC1000、PEG2000、PEG6000)和聚乙烯吡咯烷酮(PVP-K30、PVP-K90)对三种非离子表面活性剂十二烷基聚氧乙烯聚氧丙烯醚C12H25O(EO)m(PO)nH(LS36,m=3,n=6;LS5,m=4,n=5;LS54,m=5,n=4)浊点的影响.结果表明,聚乙二醇(PEG)可使三种表面活性剂水溶液浊点降低;而聚乙烯吡咯烷酮(PVP)随其浓度增加,表面活性剂溶液浊点先升高然后又下降;浊点下降程度与聚合物浓度和分子量有关. 相似文献
55.
Darja?Rudan-Tasic Cveto?KlofutarEmail author 《Monatshefte für Chemie / Chemical Monthly》2003,134(9):1185-1193
Summary. The density and refractive index of aqueous, 1,4-dioxane, and benzene solutions of poly (oxyethylene) glycols of the type HO–(CH2CH2O)
n
–H (n varying from 1 to 4) were measured at 298.15K. From these experimental data the apparent molar volume and the apparent molar refraction at infinite dilution were calculated. The limiting apparent molar volume of the investigated compounds in a definite solvent depends linearly on the number of oxyethylene groups. From these data, the volume of the monomeric unit was evaluated and found to be greater in non-aqueous solvents than in water. The limiting apparent molar refraction of the solute for the investigated systems, within the experimental uncertainties, is equal to the molar refraction of the pure solute. The electronic polarizability of the solute molecule depends linearly on the number of monomeric units and the ratio of the electronic polarizability to the molecular van der Waals volume is constant and independent of the number of oxyethylene groups.Received February 24, 2003; accepted (revised) April 10, 2003
Published online August 18, 2003 相似文献
56.
Tyrone L. Vigo 《先进技术聚合物》1997,8(5):281-288
Binding of polyethylene glycols to any fibrous substrate (such as a natural cellulosic or wool, or synthetic fibers polyester, polyamide or polyolefin) is achieved by in situ network polymerization with polyfunctional resins and acid catalysts. The modified substrates contain crosslinked polyethylene glycols that impart several improved functional properties. Two of these properties (thermal adaptability and reversible shrinkage in the wet and dry states) make it appropriate to categorize the modified fibrous substrates as “intelligent materials”. The thermal and dimensional/shape memories of the substrates are influenced and, hence, controlled by the molecular weight of the polyol, crosslink density, curing conditions to affix the polyol and construction of the fibrous substrate. Verification of these effects has been noted by thermal analysis and infrared thermography (for thermal memories) and by measurement of power generated and work performed during wet shrinkage of appropriate substrates (for shape memories). Numerous potential commercial applications are described and some are being actively pursued. © 1997 John Wiley & Sons, Ltd. 相似文献
57.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):1137-1149
ABSTRACT The condensation copolymerization of Dimethyl 5-hydroxyisophthalate (1) with Polyethylene glycols (PEGs) (2a–2d) of varying molecular weights, catalyzed by Novozyme-435 (immobilized Candida antarctica lipase B) in bulk is reported. The structures of the resulting polymers, Poly[(poly(oxyethylene)-oxy-5-hydroxyisophthaloyl] (3a–3c) were characterized by 1H (1D and 2D) and 13C-NMR spectroscopic experiments. Further, these polymers have been derivatized by attaching decanyl and 12-hydroxydodecanyl chains to the phenolic hydroxyl group. The resulting amphiphilic polymeric systems were characterized by detailed spectroscopic analysis. Light Scattering Photometry as well as Gel Per meation Chromatography were used to evaluate the particle size and molecular weights of the polymers. In principle, the method developed is flexible so that it can be used to generate a wide array of functionalized amphiphilic polymers. In the absence of biocatalytic transformation, such structural control would be extremely difficult or currently impossible to obtain. 相似文献
58.
Anu Kumari Najam A. Shakil Braj B. Singh Arthur C. Watterson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):417-424
Sixteen amphiphilic polymers were synthesized using poly(ethylene glycols) (PEGs) of different molecular weights, viz. 1000, 1500, 2000 and 4000 as hydrophilic block and linkers namely azelaic acid, suberic acid, terephthalic acid and glycolic acid as hydrophobic block in the presence of catalyst conc. H2SO4 out of which four with glycolic acid as linker are new. Synthesized polymers were characterized by using 1H-NMR, 13C-NMR and IR spectroscopy. Micellar sizes of the polymers were determined using Dynamic Light Scattering (DLS) technique which ranged from 32.1–262.0 nm and confirmed by Transmission Electron Microscope (TEM) analysis. Molecular weights were determined using HORIBA SZ-100 scientific and varied from 6.5?×?102 to 6.5?×?103 Kilo Daltons(kDa) by Debye plot. Critical Micelle Concentrations (CMC) of the synthesized polymers was determined using electrical conductivity meter and it ranged from 105 to 125 milligrams per litre (mg L?1). 相似文献
59.
S. Kucharski 《Colloid and polymer science》1994,272(3):332-337
The van der Waals, Redlich-Kwong, Peng-Robinson and an equation of state derived by Smith were applied to approximate the run of surface pressure () — area () curves of the adsorption layer ofn-pentyl ton-octyl thioethers of tri- and tetraoxyethylene glycols. The equation parameters: excluded molar area (oi) and an interaction energy term (a
i) were determined by simplex method for values in the range of 2–23.5 mN/m. The equations parameters were found to be related to the structure of the amphiphile. The oi decreased with the length of hydrocarbon thioether chain and was nearly uniform for equations of state in question except for Smith equation. The value ofa
i was dependent on the amphiphile structure. It was used to obtain the interaction energy i between amphiphiles in the adsorption layer. The values of i determined as an increment per methylene group was in the range of ca. 0.2–0.32R*T, depending on the equation of state used. 相似文献
60.
A formal synthesis of (2R-cis)-4-methyl-1-(2,3,4,5-tetrahydro-5-methyl-[2,3′-bifuran]-2-pentanone, or ipomeamarone (1) [494-23-5] was accomplished from 3-furaldehyde 5 and ethyl-2-bromocrotonate 4. The key step involved the formation of the dihydrofuran ring in 2 via a vinyloxirane rearrangement of 3 in the [2+3] dihydrofuran annulation. Mechanistic duality of reactions of those tetrahydrofurans possessing acidic hydrogens adjacent to the ring is addressed. 相似文献