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排序方式: 共有222条查询结果,搜索用时 515 毫秒
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Guowei Wang Xiaoshan Fan Bin Hu Yannan Zhang Junlian Huang 《Macromolecular rapid communications》2011,32(20):1658-1663
The eight‐shaped poly(ethylene oxide) (PEO) is synthesized by a combination of Glaser coupling with ring‐opening polymerization (ROP). Firstly, the star‐shaped (PEO‐OH) 4 is synthesized by ROP of ethylene oxide (EO) using pentaerythritol as an initiator and diphenylmethyl potassium (DPMK) as a deprotonated agent, and then the alkyne group is introduced onto the PEO arm‐end to give (PEO‐Alkyne) 4 in a NaH/tetrahydrofuran (THF) system. The intramolecular cyclization is carried out by a Glaser coupling reaction in a pyridine/CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) system at room temperature in an air atmosphere, and eight‐shaped PEO was formed with high efficiency (almost 100%). The target polymers and intermediates were well characterized by SEC, MALDI‐TOF MS, 1H NMR and FT‐IR in detail.
23.
Stirring-induced solution grown fibrillar crystals of polyethylene have been obtained from solution in Decalin. The crystals were examined by electron microscopy, and their melting and annealing behavior as well as their response to attack by fuming nitric acid were investigated. Crystals formed at lower temperatures exhibit the morphology and properties of conventional shish kebabs. Crystals formed at higher temperatures have a ribbonlike morphology and exhibit different properties from those of conventional shish kebabs. 相似文献
24.
Kamlesh Pandey Mrigank Mauli Dwivedi Mridula Tripathi Markandey Singh S. L. Agrawal 《Ionics》2008,14(6):515-523
Development and characterisation of polyethylene oxide (PEO)-based nanocomposite polymer electrolytes comprising of (PEO-SiO2): NH4SCN is reported. For synthesis of the said electrolyte, polyethylene oxide has been taken as polymer host and NH4SCN as an ionic charge supplier. Sol–gel-derived silica powder of nano dimension has been used as ceramic filler for development
of nanocomposite electrolytes. The maximum conductivity of electrolyte ∼2.0 × 10−6 S/cm is observed for samples containing 30 wt.% silica. The temperature dependence of conductivity seems to follow an Arrhenius-type,
thermally activated process over a limited temperature range. 相似文献
25.
Yogesh Patil George Zapsas Yves Gnanou Nikos Hadjichristidis 《Journal of polymer science. Part A, Polymer chemistry》2020,58(1):163-171
This study presents the synthesis and properties of linear PVDF-based amphiphilic triblock terpolymers with PS and PEO, [PVDF-b-PS-b-PEO], by adopting a procedure that involves: (a) iodine-transfer polymerization (ITP) of VDF with 1-iodoperfluorohexane (C6F13I) serving as chain-transfer agent (CTA) to afford C6F13-PVDF-I, (b) ITP of styrene with the C6F13-PVDF-I macromolecular-CTA to obtain C6F13-PVDF-b-PS-I diblock copolymer, (c) end-group exchange from iodo- to azido-group by nucleophilic substitution reaction with NaN3, and (d) copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkyne-terminated PEO to achieve C6F13-PVDF-b-PS-b-PEO triblock terpolymers. The 1H and 19F NMR spectroscopy confirmed the presence of all blocks, while gel permeation chromatography traces showed the living nature of ITP technique. The self-assembly of these terpolymers was investigated in films (atomic force microscopy and DSC), as well as in aqueous and organic solvents (DLS). The analysis of crystalline phases based on the FTIR spectroscopy indicated the conversion of PVDF α-phase into α + β-phases and β + γ-phases upon the incorporation of PS and PEO blocks, respectively. The synthesized amphiphilic copolymers were evaluated (fluorescence spectroscopy) as carriers of small hydrophobic molecules in water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 163–171 相似文献
26.
采用聚氧化乙烯(PEO)、丁二腈和高氯酸锂(LiClO4)的复合电解质体系, 制备了一系列不同配比的PEO/SN/LiClO4复合电解质, 对其室温电性能和相态结构进行了表征, 并探讨了相态结构对室温电导率的影响. 相似文献
27.
The FT‐IR spectra of poly(ethylene oxide) (PEO)‐based gel polymer electrolytes (GPEs), PEO‐NaSCN‐propylene carbonate (PC) and PEO‐NaSCN‐ethylene carbonate (EC), were measured at room temperature. Along with the FT‐IR spectra of NaSCN‐PC, PEO‐PC, and PEO‐EC, the interactions in the GPEs and the plasticizations of PC and EC are revealed. It is shown that the coordination of ether oxygen in PEO with NaSCN is the preferential solvation, whereas the interactions of PC and EC with NaSCN are relatively weak in the GPEs. However, both PC and EC play an important role in inhibiting the formation of crystalline complexes and high ionic aggregations, in addition to the ability of transformation of PEO from crystal to amorphism. It is further observed that EC exhibits the stronger ability to transform PEO crystalline into amorphism than PC when the plasticizer content in PEO is more than 25%, and also the far stronger ability to decompose the crystalline complexes, in particular, in polymer electrolytes with high salt content. 相似文献
28.
利用固体NMR 研究了高度结晶的聚氧乙烯(PEO)/六氟磷酸钠(NaPF6)(按照氧钠摩尔比8∶1 描述为PEO8∶NaPF6,分子量Mw = 1 000 和6 000 g/mol)固体聚电解质晶区链段的结构和运动.对于纯PEO 来说,晶区链段的构象交换或大角度再取向促使其13C 粉末线形从低温的非轴对称(δ33 <δ22 <δ11)变成高温的轴对称线形(δ11 =δ22 >δ33).通过变温的13C 粉末线形和243 K 下的二维交换谱,PEO8∶NaPF6 晶区链段同样存在大角度再取向,且开启温度也很低(~243 K)与PEO 接近.这种长程的运动使得PEO8∶NaPF6 从低温的类轴对称(δ33 <δ22 <δ11)变成高温的轴对称线形(δ33 >δ22 =δ11),高温线形是PEO 高温线形的翻转.与其它PEO/Na(Li)固体聚电解质不同,PEO8∶NaPF6 中晶区链段与Na+络合后仍具有很高的运动性(与纯PEO 链段的运动性相当),这种高分子链段和Na+协同运动促使Na+沿PEO 分子链轴向迁移,提高电导率. 相似文献
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30.
梳型聚合物在固液界面吸附形态的Monte Carlo模拟 总被引:1,自引:0,他引:1
采用Monte Carlo模拟方法对PAA/PEO梳型聚合物在固液界面吸附形态进行了模拟,得到了聚合物在液相中聚集形态以及在固液界面上吸附形态的瞬时构型,同时获得了聚合物的吸附层厚度、均方回转半径和吸附在固液界面的各种链段数等微观信息. 结果证实:随着聚合物的接枝数Np增大,聚合物在液相中的扩散系数逐渐降低、相对粘度逐渐增大;当Np≥6时,羧基阴离子基团置于吸附层最外围,吸附层厚度近似等于PEO侧链长度,聚合物在固体表面形成空间排斥为主、静电排斥为辅的吸附状态;吸附聚合物分子密度过低或过高均不能起到良好的空间屏蔽或阻隔效应;吸附在固体粒子表面聚合物应该具有适宜的吸附-脱附自平衡能力. 相似文献