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51.
52.
Dineshkumar Raja Abigail Philips Dr. Devikala Sundaramurthy Gopal Chandru Senadi 《化学:亚洲杂志》2021,16(22):3754-3759
D-fructose, a biomass-derived carbohydrate has been identified as an environmentally benign C2 synthon in the preparation of synthetically useful 2-hydroxymethylbenzimidazole derivatives by coupling with 1,2-phenylenediamines. Proof of concept was established by synthesizing 23 examples using BF3.OEt2 (20 mol%), TBHP (5.5 M, decane) (1.0 equiv.) in CH3CN at 90 °C for 1 h. The pivotal features of this method include metal-free conditions, short time, good functional group tolerance, gram scale feasibility and the synthesis of benzimidazole fused 1,4-oxazine. Control studies with conventional C2 synthons did not produce the desired product, thus suggesting a new reaction pathway from D-fructose. 相似文献
53.
《印度化学会志》2023,100(6):101007
A series of tungstophosphoric acid supported on activated carbon derived from left-over orange-peel catalysts (TPA/OAC) have been prepared. These catalysts were examined for one-pot catalytic transformation of fructose/glucose to 5-ethoxymethylfurfural. Physico-chemical properties of the catalytic materials were executed by using various characterization methods. Spectroscopic analysis results propose that TPA was finely distributed on the high surface area carbon support with persistent Keggin ion structure. The EMF yield is depended on the content of active component TPA on support and also on the reaction conditions. The catalyst with 25 wt% TPA on OAC presented highest activity towards EMF synthesis from fructose. Although, the catalyst 25 wt% TPA/OAC showed low activity towards EMF synthesis from glucose, higher yields of ethyl glucopyranoside could be formed from glucose in EtOH. Activated carbon was synthesized by carbonization of orange peel treated with H3PO4, which was used as a good support for HPAs. The catalysts are quite stable and recyclable for the dehydrative alkylation of fructose. 相似文献
54.
采用微波水热合成纳米β沸石,并利用微波辅助的类芬顿法可控去除纳米β沸石孔道中的模板剂,使其具备一定的孔道深度、比表面积以及可接近酸性位.以果糖酸催化转化为5-羟甲基糠醛(5-HMF)为探针反应,探索了果糖分子在不同孔道深度和活性位的纳米β沸石中的扩散行为对催化效果的影响.研究发现,酸性位相同的条件下,纳米沸石孔道深度越深扩散限制越显著,反应选择性越差.即使在催化剂加入量相同即可接近酸性位不同时,果糖分子在孔道中的扩散限制对催化反应的影响也显著于酸量的影响,充分说明了微孔催化剂中反应物/产物分子扩散限制对于催化反应影响的重要性,使得所制备催化剂的表面酸性位和适宜的孔道深度共同对反应产生有利的影响. 相似文献
55.
在水溶液中锡盐与β分子筛金属化过程中很容易水解为氢氧化物,因此,制备高度分散的、以孤立形式存在的锡物种非常具有挑战性.我们先采用SnCl2/氯化胆硷(ChCl)络合物将锡物种固定在高硅的商品化的β分子筛上,然后焙烧就可很方便地在水溶液条件下制得了高度分散于β分子筛上的锡物种.电镜照片、紫外-可见光光谱和X射线衍射结果证实了这一点.ChCl的存在促进了锡物种与分子筛的结合.担载(1-2)wt%Sn的β分子筛在葡萄糖-果糖异构化反应中表现出较高的催化活性和选择性. 相似文献
56.
Gabriel Morales Juan A. Melero Marta Paniagua Jose Iglesias Blanca Hern ndez Mar a Sanz 《催化学报》2014,35(5):644-655
Sulfonic acid-functionalized heterogeneous catalysts have been evaluated in the catalytic dehydration of C(,monosaccharides into 5-hydroxymethylfurfural(HMF) using dimethyl sulfoxide(DMSO)as solvent.Sulfonic commercial resin Amberlyst-70 was the most active catalyst,which was ascribed to its higher concentration of sulfonic acid sites as compared with the other catalysts,and it gave 93 mol%yield of HMF from fructose in 1 h.With glucose as the starting material,which is a much more difficult reaction,the reaction conditions(time,temperature,and catalyst loading) were optimized for Amberlyst-70 by a response surface methodology,which gave a maximum HMF yield of 33 mol%at 147 °C with 23 wt%catalyst loading based on glucose and 24 h reaction time.DMSO promotes the dehydration of glucose into anhydroglucose,which acts as a reservoir of the substrate to facilitate the production of HMF by reducing side reactions.Catalyst reuse without a regeneration treatment showed a gradual but not very significant decay in catalytic activity. 相似文献
57.
58.
磺酸官能化的磁性核壳结构的纳米材料用于果糖脱水制备5-羟甲基糠醛(英) 总被引:1,自引:0,他引:1
通过反相微乳液法制备了以Fe3O4为核,磺酸官能化的硅基材料为壳层的磁性酸性催化剂.首先制备纳米Fe3O4磁核,然后涂层包覆苯基修饰的纳米级硅层,最后进行苯基磺化修饰,制得固体酸催化剂Fe3O4@Si/Ph-SO3H.在果糖脱水制备5-羟甲基糠醛反应中,该催化剂表现出较好的催化活性,优于传统催化剂A-15,且与均相无机酸催化活性相当.当采用二甲基亚砜作溶剂,在110℃下反应3 h,果糖转化率达到99%,5-羟甲基糠醛收率为82%.另外,该催化剂经磁法回收后可多次重复使用. 相似文献
59.
Boiling points of aqueous solutions affect the design and operation of evaporators. Hence, boiling points of aqueous solutions of d-glucose and d-fructose were experimentally determined at soluble solute concentration from 10 to 60% sugar by mass and pressure from 20 to 93.6 kPa. The experimental data were correlated with data predicted by the calculation of the activity coefficients with the UNIFAC-Lyngby model using different approaches for decomposition of the molecular structure: the aliphatic groups and the cyclic groups. Moreover, the rise in experimental boiling point of the aqueous sugar solutions was evaluated by the Dühring's rule. It was observed that the cyclic approach resulted in better accuracy for liquid–vapor equilibrium prediction and the non-ideality of these solutions are relevant in the boiling point rise, confirming that the rise in boiling point of aqueous d-glucose and d-fructose concentrated solutions is significant to the design of heat and mass transport operations. 相似文献
60.
The vineyard produces one of the most important crops in Portugal and is affected by various pests, such as the Lobesia botrana moth, which can be attracted chemically by compounds on the grape skin.In this study, the sugar contents (glucose and fructose) on grape skin were analysed for five Portuguese Vitis vinifera grape varieties and compared in grape juice and whole grapes. Samples were harvested in July, August and September of 2001 and 2002.The quantification was attained employing a new methodology, which comprised the preparation of a methanol solution to extract the compounds from the grape skin and further chromatographic analyses by liquid chromatography (LC) with refractive index (RI) detection. The samples designated by whole grapes were homogenised, centrifuged and filtrated, while the juice was obtained by crushing and filtration.Grape skin has shown higher levels of glucose than fructose, but both compounds increased from green berry (July) to veraison (August) and had a slight decrease from veraison to harvest (September).As expected, the glucose and fructose contents (total sugar) were higher in the whole grape than in the juice and much higher than in the grape skin itself. For Loureiro and Trajadura varieties, the levels of both sugars on grape skin were very similar. This resemblance strengthened the statement of the decisive role of this parameter in female L. botrana oviposition behaviour. 相似文献