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61.
Ayyamperumal Sakthivel Anthony S.T. Chiang 《Journal of organometallic chemistry》2006,691(5):1007-1011
η5-Cp(COOMe)MoCl(CO)3 is grafted on the surface of mesoporous MCM-41 and MCM-48 materials through available silanol groups. The structural intactness of the supporting materials is confirmed by powder XRD and N2 adsorption analysis. The presence of the Mo complex on the surface is confirmed by FT-IR and elemental analysis. The catalysts are successfully applied for cyclooctene epoxidation. 相似文献
62.
63.
Cheng-yi LiiChia-ding Liao Leszek StobinskiPiotr Tomasik 《European Polymer Journal》2002,38(8):1601-1606
Polymerization of ethylene was initiated by low-pressure glow plasma generated in this gas. Depending on starch present in this plasma polymerization could be considered either as graft-polymerization of ethylene onto starch or homopolymerization. Result of the treatment of cassava, corn, potato, rice Indica, sweet potato, and waxy corn starches with ethylene plasma was analyzed by means of high-performance size exclusion chromatography, X-ray powder diffraction, thermogravimetry, digestion with β-amylase, and scanning electron microscopy. Analyses suggested that graft-polymerization occurred on sweet potato and rice starch. With other starches homopolymerization of ethylene on granules took place. 相似文献
64.
To realize the mechanism of particle formation followed by the grafting of styrene (St) onto poly(vinyl alcohol) (PVA) more precisely, we investigated the influence of additives on model experiments of emulsion polymerizations in 1 ml styrene (St) per 100 ml water at 70 °C using PVA as a protective colloid. In the case of a standard system without additive, experimental results indicate new particle formation, and that 30% of St feed and 30% of the PVA used were grafted. The sulfate radical seldom enters into particles but reacts with PVA, forming the PVA radical that yields the grafting of St onto PVA. The experimental results are thought to arise from a hydrogen abstraction from PVA with a sulfate radical. The addition of low-molecular-weight alcohol, such as isopropyl alcohol (i-PrOH) and n-propyl alcohol (n-PrOH), strongly affected the mechanism of particle formation in terms of a decrease in grafting, due to competition between hydrogen abstraction from PVA and the alcohols with a sulfate radical. Surprisingly, the addition of a low-reactive alcohol, such as t-butyl alcohol (t-BuOH), also resulted in the particle formation with a decrease in grafting, influenced the polymerization locus to be a monomer droplets dispersed by t-BuOH, and confirmed homogeneous nucleation with the increase in the solubility of St in the aqueous phase. 相似文献
65.
Radical polymerization of methyl methacrylate initiated by the system cellulose-water-carbon tetrachloride was kinetically studied. Results obtained are: 1) The amounts of water, carbon tetrachloride, and cellulose affected the conversion. Michaelis-Menten's equation was applied to the relationship between the rate of polymerization and the amount of MMA. 2) Other methacrylates and acrylates were also polymerized by this system. 3) When methanol or ethanol was used instead of water, some weak polymerization activity was observed. 4) Initiating ability depended on the kind of cellulose used. 5) The activity of cellulose was not changed by washing with boiling water or by solvent extraction. 6) Polymerization was inhibited by the presence of air. 7) Heating in the presence of water and carbon tetrachloride markedly decreased the activity of the cellulose. 相似文献
66.
Sukeewan Detyothin Susan E.M. Selke Ramani Narayan Maria Rubino Rafael Auras 《Polymer Degradation and Stability》2013
A response surface methodology (RSM) design was used to analyze the effects of maleic anhydride (MA) and 2,5-bis(tert-butylperoxy)-2,5-dimethyl hexane (Luperox or L101) content, and TSE screw speed on the degree of grafted MA (MAg) and number average molecular weight (Mn) of maleated PLA (PLA-g-MA), which can be used as a reactive compatibilizer in production of PLA blends with various components. PLA-g-MA's FTIR peaks indicated that MA was grafted onto the PLA backbone and oligomeric MA was also present. A maximum of 0.52 wt% MAg determined by titration was achieved at the expense of a 50% reduction of Mn and an increase in the polydispersity index to around 2.0. Generally, increasing L101 increased the degree of grafting and decreased Mn. L101 and MAg had a large effect on the stability of PLA-g-MA's Mn during storage. Nominally, amounts of MA equal to 4.5 wt%, L101 between 0.45 and 0.65 wt%, and screw speed of 20 rpm provided the optimal conditions for grafting MA onto PLA. 相似文献
67.
Producing ultra-thin silica coatings on iron-oxide nanoparticles to improve their surface reactivity
Slavko Kralj Darko Makovec Miha Drofenik 《Journal of magnetism and magnetic materials》2010,322(13):1847-89
The reactivity of the relatively inert surfaces of iron-oxide magnetic nanoparticles can be significantly improved by coating the surfaces with silica. Unfortunately, however, this nonmagnetic silica layer tends to dilute the magnetic properties of the nanoparticles. Therefore, the silica layer should be as continuous, homogeneous, and as thin as possible.In this investigation we coated superparamagnetic maghemite nanoparticles by hydrolysis and the polycondensation of tetraethyl orthosilicate (TEOS), with the ethanol solution of TEOS being added to a stable suspension of citric acid-coated nanoparticles. The influences of the various parameters of the procedure on the quality of the coatings were systematically evaluated. The quality of the silica layer was characterized using electron microscopy and by performing leaching of the nanoparticles in HCl, while the surface reactivity was tested by grafting (3-aminopropyl) triethoxysilane (APS) onto the nanoparticles. We observed that the surface concentration of the grafted APS strongly increased when the nanoparticles were coated with a silica layer. The choice of experimental conditions for the coating procedure that favors the heterogeneous nucleation of silica on the surfaces of the nanoparticles enabled the preparation of very thin silica layers, less than 2 nm thick. By decreasing the amount of added TEOS to correspond to a monolayer of -Si-OH at the nanoparticles' surfaces, their surface reactivity could be very much improved, and with a reduction in their magnetization of only ∼10%. 相似文献
68.
The use of polymeric materials in ion-exchange chromatography applications is advantageous because of their typically high
mechanical stability and tolerance of a wide range of pH conditions. The possibility of using polymeric monoliths in ion-exchange
chromatography is therefore obvious and many of the same strategies developed for polymeric particles have been adapted for
use with polymeric monoliths. In this review different strategies for the synthesis of polymeric monoliths with ion-exchange
functionality are discussed. The incorporation of ion-exchange functionality by co-polymerization is included, as also are
different post-polymerization alterations to the monolith surface such as grafting. The formulations and strategies presented
include materials intended for use in analytical separations in ion-exchange chromatography, sample pre-treatment or enrichment
applications, and materials for capillary electrochromatography. Finally, examples of the use of polymeric monoliths in ion-exchange
chromatography applications are included with examples published in the years 2003 to 2008.
相似文献
Emily F. HilderEmail: |
69.
Marta Abrantes Ayyamperumal Sakthivel Fritz E. Kühn 《Journal of organometallic chemistry》2006,691(14):3137-3145
The complex [(−)-menthylCp]Mo(CO)3Cl (1) was synthesized by the reaction of Mo(CO)3(EtCN)3 with [(−)-menthylCpH] to produce the hydride [(−)-menthylCp]Mo(CO)3H. The latter compound was then reacted with CCl4 to form [(−)-menthylCp]Mo(CO)3Cl (1). Compound 1 was tested as catalyst for the epoxidation of cis-cyclooctene, styrene and trans-β-methylstyrene in the presence of tert-butyl hydroperoxide (TBHP) at 55 °C using chloroform as solvent. Results under homogeneous conditions prompted the authors to immobilize complex 1 on mesoporous MCM-41 and MCM-48 surfaces leading to the grafted materials AM-41CpMoChi and AM-48CpMoChi. The presence of the organometallic complexes in the materials was confirmed by powder X-ray diffraction, N2 adsorption/desorption isotherms, TEM, EA, FT-IR, 1H MAS NMR and TG-MS. AM-41CpMoChi and AM-48CpMoChi were also tested as epoxidation catalysts. The catalytic examinations also included leaching experiments, and the reusing of the grafted materials for several runs. 相似文献
70.
Ying Zheng Xu-xu Wang Zhao-hui Li Ke-mei Wei 《Journal of organometallic chemistry》2005,690(13):3187-3192
The grafting reaction of SnMe4 on the surface of Hβ zeolite (Si/Al = 25.0) was studied under high vacuum conditions. The chemical compositions and structure of the resulting solid were characterized by in situ FTIR, ICP, XRD, XPS, 13C and 119Sn MAS NMR, UV-Vis DRS, gas phase chromatogram (GC), chemical analyses, temperature programmed decomposition (TPD), temperature programmed reduction (TPR), and N2 adsorption at low temperature. The results showed that SnMe4 reacts with Hβ zeolite quantitatively at temperature as low as 183 K and the reaction occurred on the surface of the zeolite without destroying the framework of zeolite. The BET surface area and the pore volume of the zeolite decreased and the surface properties changed, however the microporous structure was retained upon the reaction and post treatment. 相似文献