全文获取类型
收费全文 | 106篇 |
免费 | 5篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 2篇 |
综合类 | 8篇 |
化学工业 | 45篇 |
机械仪表 | 3篇 |
建筑科学 | 1篇 |
矿业工程 | 1篇 |
能源动力 | 2篇 |
轻工业 | 28篇 |
石油天然气 | 11篇 |
一般工业技术 | 12篇 |
原子能技术 | 1篇 |
自动化技术 | 1篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 1篇 |
2009年 | 8篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 10篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1993年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有115条查询结果,搜索用时 468 毫秒
1.
Marcus Heinze Sandra Starke Marcel Händler Hartmut Komber Marco Drache Norbert Moszner Brigitte Voit Doris Pospiech 《应用聚合物科学杂志》2019,136(48):48256
We demonstrate in this study that the combination of modern inline monitoring methods [here: inline nuclear magnetic resonance (NMR)] with simulations gains more exact and profound kinetic results than previously used methods like linearization without that combination. The 1H-NMR spectroscopic data (more than 100 data points) are used to construct the copolymerization diagram. The reactivity ratios are obtained applying the van Herks nonlinear least square method. The examination of the radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) with (2-{[2-(ethoxycarbonyl)prop-2-en-1-yl]oxy}ethyl) phosphonic acid (ECPPA) as important adhesive monomer used in dentistry yields reactivity ratios of rHEMA = 1.83; rECPPA = 0.42. The copolymerization diagram reflects nonideal, non-azeotropic copolymerization. The sequence distribution of the obtained by Monte Carlo simulation indicates the generation of statistical copolymers. As an important finding, it is demonstrated that the repeating units responsible for etching and adhesion are arranged over the whole polymer chain, which is necessary to achieve proper functionality. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48256. 相似文献
2.
Raffaele Sacchi Isabel Medina Santiago P. Aubourg Francesco Addeo Livio Paolillo 《Journal of the American Oil Chemists' Society》1993,70(3):225-228
Based on proton nuclear magnetic resonance (1H-NMR) spectroscopy, a rapid and structure-specific method for the determination of ω-3 polyunsaturated fatty acids (PUFAs)
in fish lipids is presented. The different chemical shift observed for the methyl resonance of ω-3 PUFAs (δ=0.95 ppm) with
respect to the methyl resonance of all other fatty acids (δ=0.86 ppm) has provided the possibility of proposing a new and
rapid method for the determination of ω-3 PUFA content. Twenty-four fish lipid samples (raw, cooked and canned albacore tuna)
produced results that showed good agreement between1H-NMR analysis and gas chromatographic determination. Raw and cooked samples showed significantly higher levels of ω-3 PUFA
than canned tuna. 相似文献
3.
4.
侧链为亚乙氧基结构的EVOH梳型聚合物的合成 总被引:1,自引:0,他引:1
以乙烯-乙烯醇共聚物(EVOH)为原料,制备了一种主链为疏水的聚乙烯链段,侧链具有亚乙氧基结构的多羟基梳形聚合物,用元素分析法、凝胶渗透色谱法、核磁共振谱法对其进行了结构表征;用热重分析法和示差扫描量热法对其热学性能进行了表征。结果表明,接枝后产物的玻璃化转变温度在-52--40℃之间,熔点在55~600℃之间,由于侧链的引入破坏了EVOH的结晶,因此梳形聚合物的热分解温度比EVOH降低了约20℃。 相似文献
5.
Jose E. Herrera Ja Hun Kwak Jian Zhi Hu Yong Wang Charles H. F. Peden 《Topics in Catalysis》2006,39(3-4):245-255
The advantages of the atomic layer deposition (ALD) method for preparation of tungsten, vanadium, titanium, and molybdenum
oxide catalyst supported on mesoporous silica are discussed, with emphasis on the importance of synthesis conditions on dispersion,
structure and activity of the resulting materials. A suite of complementary techniques such as DRS-UV/Vis, BET, 1H-NMR, XRD, and TEM were used to study the structural properties of the supported metal oxides, and probe reactions such as
2-butanol dehydration and ethanol partial oxidation were used to demonstrate the potential advantages of the ALD-prepared
catalysts. Specifically, highly dispersed oxides of titanium, molybdenum, and tungsten oxide on mesoporous silica were synthesized
using the ALD method. It is also demonstrated that attainment of high dispersions of vanadium oxide on mesoporous silica requires
the presence of at least a single layer of titanium oxide due to the well-known poor interaction between vanadia and silica.
The highly dispersed catalysts prepared here by ALD methods exhibited superior catalytic performance relative to those prepared
using conventional incipient wetness impregnation. 相似文献
6.
In many transition metal dihydrides and dihydrogen complexes the hydrogens are relatively weakly bound and exhibit a fairly high mobility, in particular with respect to their mutual exchange. Part of this high mobility is due to the exchange symmetry of the two hydrogens, which causes an energy splitting into even and odd spatial energy eigenfunctions, resulting in the typical coherent tunneling of a two-level system. Owing to the quantum mechanical symmetry selection principles the eigenfunctions are connected to the possible nuclear spin states of the system. If the tunneling frequency is in the proper frequency window it is thus possible to observe these tunneling transitions by NMR at very low temperatures, where no thermally induced exchange reactions overshadow the tunneling. The first part of this review gives an introduction into the interplay of chemical kinetics and tunneling phenomena in general, rotational tunneling of dihydrogen in a two-fold potential in particular and the Bell tunnel model, followed by a summary of solid state NMR techniques for the observation of these tunnel processes. Then a discussion of the effects of these processes on the 2H NMR line shape is given. The second part of the review reports results of a 2H-solid state NMR spectroscopy and T1 relaxatiometry study of trans-[Ru(D2)Cl(PPh2CH2CH2PPh2)2]PF6, in the temperature regime from 5.4 to 320 K. In the Ru-D2 sample coherent tunneling and incoherent exchange processes on the time scale of the quadrupolar interaction are observed. From the spectra and T1-data the height of the tunneling barrier is determined. Next results of 2H-spin–lattice relaxation measurements for a selectively η2 − D2 labeled isotopomer of the complex W(PCy3)2(CO)3)(η2 − D2) are presented and discussed. The relaxation measurements are analyzed in terms of a simple one dimensional Bell tunnel model and comparison to incoherent neutron scattering (INS) data from the H2 complex. The comparison reveals a strong isotope effect of 2 × 103 for the exchange rates of the deuterons versus hydrons. 相似文献
7.
Ozonized oils have interesting applications in the cosmetic industry and several patents on enriched products were developed in the last years. Ozonides are known for their high reactivity and stability data are required for enriched cosmetic products during storage. In this paper a dedicated determination of Peroxide Value (PV) was performed on ozonized sunflower oil (Neozone 4000) and on some enriched cosmetics, in order to control their stability during storage. The optimal conditions of the PV method were determined, following the decomposition reaction of ozonides with KI utilizing 1H-NMR and GC/MS techniques. 相似文献
8.
醇水饮料中易于形成各种氧键,NMR适合于啤酒体系氢键的研究.乙醇浓度在60%左右时,羟基质子化学位移最大,啤酒中羟基质子化学位移在4.896~4.935ppm之间变化.啤酒体系中除乙醇外的其它物质对羟基质子化学位移有-23%-40%左右的影响,即会减弱醇水氢键的缔合.相同原麦汁度的原浓酿造酒比稀释酒的羟基质子化学位移偏高,且随着稀释率的增加,羟基质子化学位移逐渐减小.啤酒水化阶段氢键缔合作用经历平衡-增强-平衡-增强-极点-减弱-平衡的变化过程.水化14h左右达到极点. 相似文献
9.
Diego?L.?García-González Luisa?Mannina Marco?D’Imperio Anna?Laura?Segre Ramón?AparicioEmail author 《European Food Research and Technology》2004,219(5):545-548
The lack of any official analytical method to detect the adulteration of olive oil with a low percentage of hazelnut oil is explained by the similarities in the chemical compositions of both kinds of oils. To counter this problem, an artificial neural network based on 1H-NMR and 13C-NMR data has been developed to detect olive oil adulteration, and the results from this ANN are presented here. A training set consisting of hazelnut oils, pure olive oils, and olive oils blended with 2–20% hazelnut oils was used to design and train a multilayer perceptron with 100% correct classifications. This mathematical model was also validated using an external validation set of blend samples (3–15%) and genuine samples. The detection limit of the model was around 8%. 相似文献
10.
Ruediger Helling Anja Mieth Stefan Altmann 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(3):395-407
Different silicone baking moulds (37 samples) were characterized with respect to potential migrating substances using 1H-NMR, RP-HPLC–UV/ELSD and GC techniques. In all cases cyclic organosiloxane oligomers with the formula [Si(CH3)2–O] n were identified (n = 6 … 50). Additionally, linear, partly hydroxyl-terminated organosiloxanes HO–[Si(CH3)2–O] n –H (n = 7 … 20) were found in 13 samples. No substances other than siloxanes could be detected, meaning the migrants mainly consist of organopolysiloxanes. Based on this knowledge, a 1H-NMR quantification method for siloxanes was established for the analysis of both simulants and foodstuffs. Validation of the 1H-NMR method gave suitable performance characteristics: limit of detection 8.7 mg kg–1 oil, coefficient of variation 7.8% (at a level of 1.0 mg kg–1 food). Migration studies were carried out with simulants (olive oil, isooctane, ethanol (95%), Tenax) as well as preparation of different cakes. From the 1st to 10th experiment, siloxane migration into cakes only slightly decreased, with a significant dependence on fat content. Migration never exceeded a level of 21 mg kg–1 (3 mg dm–2) and was, therefore, well below the overall migration limit of 60 mg kg–1 (10 mg dm–2). However, migration behaviour into simulants differed completely from these results. 相似文献