全文获取类型
收费全文 | 229篇 |
免费 | 2篇 |
国内免费 | 28篇 |
专业分类
化学 | 242篇 |
晶体学 | 2篇 |
力学 | 1篇 |
物理学 | 14篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 14篇 |
2012年 | 11篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 13篇 |
2008年 | 26篇 |
2007年 | 18篇 |
2006年 | 16篇 |
2005年 | 17篇 |
2004年 | 10篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 16篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有259条查询结果,搜索用时 15 毫秒
71.
B. Mahltig J.-F. Gohy R. Jérôme C. Bellmann M. Stamm 《Colloid and polymer science》2000,278(6):502-508
The adsorption of the diblock polyampholyte poly (methacrylic acid)-block-poly((dimethylamino)ethyl methacrylate) from aqueous solution on silicon substrates was investigated as a function of polymer
concentration and pH. Dynamic light scattering and electrokinetic measurements were used to characterize the polyampholyte
in solution. The amount of polymer adsorbed was determined by ellipsometry and lateral structures of the polymer layer were
investigated by scanning force microscopy. The amount of polymer adsorbed was found to be strongly influenced by the pH of
the polymer solution, while the size of the polyampholyte micelles adsorbed on the surface was hardly affected by pH during
adsorption. From investigations by scanning force microscopy well-seperated micelles were seen in the dried monolayers adsorbed
directly from solution. The structures at the surface are correlated to structures in solution, and the adsorbed amount depends
on the relative charge of the micelles and the surface.
Received: 13 September 1999 Accepted in revised form: 8 December 1999 相似文献
72.
73.
Some surfactant solutions have been observed to exhibit a strong drag reduction behavior in turbulent flow. This effect is generally believed to result from the formation of large cylindrical micelles or micellar structures. To characterize and understand better these fluids, we have studied the transient rheological properties of an efficient drag-reducing aqueous solution: tris (2-hydroxyethyl) tallowalkyl ammonium acetate (TTAA) with added sodium salicylate (NaSal) as counter ion. For a 5/5 mM equimolar TTAA/NaSal solution, there is no measurable first normal stress difference (N
1) immediately after the inception of shear, but N
1 begins to increase after a well-defined induction time — presumably as shear-induced structures (SIS) are formed — and it finally reaches a fluctuating plateau region where its average value is two orders of magnitude larger than that of the shear stress. The SIS buildup times obtained by first normal stress measurements were approximately inversely proportional to the shear rate, which is consistent with a kinetic process during which individual micelles are incorporated through shear into large micellar structures. The SIS buildup after a strong preshear and the relaxation processes after flow cessation were also studied and quantified with first normal stress difference measurements. The SIS buildup times and final state were also found to be highly dependent on flow geometry. With an increase in gap between parallel plates, for example, the SIS buildup times decreased, whereas the plateau viscosity increased. 相似文献
74.
《Journal of Dispersion Science and Technology》2013,34(5):673-681
Abstract Diffusion coefficients of different aggregates in aqueous solutions formed by an amphiphilic block copolymer, Pluronic F127 (F127), were determined by cyclic voltammetry, and the critical micelle concentration (CMC, 4.31 × 10?4 mol L?1) of F127 was obtained. The added n‐butanol facilitates the formation of micelles from the monomers of F127 and makes the critical micelle temperature (CMT) of F127 solutions decrease. The diffusion coefficient of the F127 micelles decreases relatively fast at first with increasing n‐butanol and then the decreasing trend slows after the solubilization of n‐butanol in micelles reaches maximum. 相似文献
75.
采用可逆-加成-断裂链转移自由基聚合(RAFT)技术合成了两亲性嵌段共聚物聚苯乙烯-b-聚甲基丙烯酸聚乙二醇单甲醚-b-聚苯乙烯(PSt-b-POEOMA-b-PSt),通过FT-IR、1 HNMR、GPC确定共聚物的结构。将三个具有不同嵌段比的共聚物在水溶液中自组装,通过透射电子显微镜(TEM)观察得到的胶束的形貌,发现随着亲水性嵌段的比例减小,胶束的直径略微减小。通过透析方法,以共聚物作为载体,负载维生素E,TEM观察载药胶束的形貌,仍然为核-壳状的球形胶束。差示扫描量热仪(DSC)测试共聚物载药胶束前后的热性能,发现药物分子在载入内核的过程中,聚苯乙烯的玻璃化转变温度(Tg)有所降低。通过紫外(UV)分析计算得出共聚物的药物负载量(DLC)为70%~80%。 相似文献
76.
The Effect of Sodium Dodecylbenzenesulfonate (SDBS) Micelles on a BelousovZhabotinsky Oscillating System Catalyzed with a Tetraazamacrocyclic Copper(II) Complex
下载免费PDF全文
![点击此处可从《Helvetica chimica acta》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yang‐Yang Chen Gang Hu Yu‐Qin Nian Meng‐Shuo Li Ji‐Mei Song Lin Hu 《Helvetica chimica acta》2014,97(2):237-244
This article deals with the influence of micelles of the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) on the Belousov? Zhabotinsky (B? Z) oscillating reaction catalyzed by a tetraazamacrocyclic copper(II) complex [CuL](ClO4)2, an enzyme‐like catalyst (L=5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradeca‐4,11‐diene). Unlike the classical B? Z oscillator in which malonic acid is usually used as a substrate, malic acid (an intermediate in the Krebs cycle) is involved in this oscillating system. Experiments reveal that formation of the SDBS micelles markedly affects the behavior of the oscillating reaction. It is found that there is a linear relationship between the change in the oscillation amplitude (ΔA) and the concentration of SDBS, whereas the change in the oscillation period (ΔT) is linearly proportional to the SDBS concentration. The most likely mechanism that involves the formation of the SDBS micelles and the effects of the micelles on the oscillating chemical system can be rationalized by assuming that the SDBS micelles are so negatively charged that they attract more [CuL]3+ than [CuL]2+. This hypothesis was confirmed by UV/VIS spectrophotometric measurements of a constant concentration of [CuL](ClO4)2 in different concentrations of SDBS; as the SDBS concentration increased, the absorbance of [CuL](ClO4)2 increased, while the maximum absorption wavelength for [CuL](ClO4)2 remained at 502 nm. 相似文献
77.
Tao Wan Denghui Wang Junyan Hu Zhiling Zhou Haibo Zhang Daolu Bu 《Journal of Dispersion Science and Technology》2014,35(1):7-13
The effect of the addition of sodium 4-styrenesulfonate (SSS) and KNO3 as well as temperature and shear rate on the structural transition of aqueous micellar solutions of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) was studied by viscosity. The effect of hydrocarbons on viscoelastic CTAB solutions was also examined. Possible mechanism for formation of CTAB wormlike micelles in the presence of sodium 4-styrenesulfonate (SSS) and KNO3 was discussed. The rapid increase in the apparent viscosity of CTAB solutions on the addition of SSS and KNO3 was due to the transition in micellar shape from spheres to wormlike ones. The rheological properties of CTAB solutions fit Maxwell model at low shear frequency. AFM image indicated a structure of transient network of CTAB/SSS/KNO3/H2O solution. 相似文献
78.
Fluid-like colloidal structures are key components in nature's own functional materials and important for various applications. For instance, self-assembled structures are formed spontaneously by amphiphilic molecules in solvent, tailored by directional noncovalent intermolecular forces. These structures form the framework of cells defining their geometry and microenvironments for chemical reactions, for maintaining concentration gradients, and for nutrient exchange. Knowledge on the mechanisms at play that underlie the self-assembly of amphiphilic molecules into nanostructures in aqueous and nonaqueous solvents and their dispersion into particles can have direct implications for the rational design of new advanced and nature-inspired materials. These colloidal materials could help to deliver drug molecules and nutrients in a tailored manner to the body, or act as sustainable solvents for chemical or biotechnological processes. This contribution summarizes the recent progress in understanding the self-assembly structure formation in polar and nonpolar solvents and discusses the advances in hierarchically organized systems. Furthermore, it discusses challenges in the characterization of structure and dynamics in these biomimetic materials and highlights selected applications in the fields of drug delivery, food, and biotechnology. 相似文献
79.
Protolytic equilibria taking place in aqueous solutions of sodium deoxycholate (DCNa) have been studied at 25°C using 0.5M NaCl as ionic medium. Electromotive force measurements of a galvanic cell were carried out by means of a glass electrode.The reagent necessary to change the acidity of the solutions was produced in situ by supplying a constant small current.Solubility and acid constant of deoxycholic acid (HDC) have been determined for the chosen experimental conditions. Experimental data obtained in less acid solutions have been explained by assuming the presence of the species H(DC)2. The relative stability constant has been determined. At higher deoxycholate concentration the presence of a polymeric micellar species has been assumed.
Symbols H analytical excess of hydrogenions, if negative it corresponds to OH–; - h free concentration of hydrogen ions; - A total concentration of deoxycholate; - a free concentration of deoxycholate; - K a acid constant of deoxycholic acid (HDC) defined as follows: [HDC]K a =ha; - q,p stability constant of a speciesH p (DC) q defined as follows: [H p (DC) q ]= q,p h p a q ; - C 0 solubility of HDC; - formation function representing the average number of H+ bonded to deoxycholate. 相似文献
Protolytische Gleichgewichte in wäßrigen Natriumdesoxycholat-Lösungen
Zusammenfassung Die Protonierung von Natrium-Desoxycholat (DCNa) in wäßrigen Lösungen mit 0.5M NaCl wurde bei 25°C mit Hilfe von E.M.K. Messungen mit einer Glaselektrode untersucht.Das notwendige Reagens für die Umwandlung der Säure in den untersuchten Lösungen wurde in situ durch einen konstanten schwachen Strom erzeugt.Löslichkeit und Dissoziationkonstante von Desoxycholsäure (HDC) wurden unter den gewählten experimentellen Bedingungen bestimmt. Die experimentellen Daten in schwach sauren Lösungen konnten mit der Annahme der Existenz von H(DC)2 erklärt werden. Die entsprechende Konstante wurde bestimmt. Zur Erklärung der Daten in stärker konzentrierten Lösungen von Desoxycholat ist die Annahme einer polynuklearen Spezies nötig.
Symbols H analytical excess of hydrogenions, if negative it corresponds to OH–; - h free concentration of hydrogen ions; - A total concentration of deoxycholate; - a free concentration of deoxycholate; - K a acid constant of deoxycholic acid (HDC) defined as follows: [HDC]K a =ha; - q,p stability constant of a speciesH p (DC) q defined as follows: [H p (DC) q ]= q,p h p a q ; - C 0 solubility of HDC; - formation function representing the average number of H+ bonded to deoxycholate. 相似文献
80.
两亲性壳聚糖衍生物的合成及其自聚集现象 总被引:1,自引:0,他引:1
以壳聚糖为主链, 聚乙二醇单甲醚为亲水性链段, 癸二酸为疏水链段, 合成了一系列两亲性壳聚糖衍生物. 通过FTIR, 1H NMR和X射线粉末衍射等手段对壳聚糖衍生物进行了结构表征, 由元素分析方法计算出衍生物的取代度. 采用直接溶解法制备了壳聚糖衍生物的空白胶束, 通过透射电子显微镜(TEM)观察了胶束的形态. 由动态光散射(DLS)测定了胶束的粒径及分布, 并以芘为分子探针, 通过荧光光谱法测定了壳聚糖衍生物的临界聚集浓度(CAC). 研究结果表明, 壳聚糖主链上疏水链段的取代度越大, 其衍生物的临界聚集浓度越低, 相同浓度下的胶束的粒径也越小. 相似文献