全文获取类型
收费全文 | 148篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 128篇 |
数学 | 3篇 |
物理学 | 26篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 16篇 |
2007年 | 10篇 |
2006年 | 22篇 |
2005年 | 14篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有157条查询结果,搜索用时 15 毫秒
41.
Gijs M. ter Huurne Ghislaine Vantomme Bart W. L. van den Bersselaar Bala N. S. Thota Ilja K. Voets Anja R. A. Palmans E. W. Meijer 《Journal of polymer science. Part A, Polymer chemistry》2019,57(3):411-421
The supramolecular folding of amphiphilic heterograft copolymers equipped with dendritic pendants is investigated using a combination of proton nuclear magnetic resonance (1H NMR) spectroscopy, small‐angle X‐ray scattering, and circular dichroism spectroscopy. Hereto, the linear poly(ethylene glycol) pendants normally used to convey water compatibility are partially substituted with branched analogues. For one set of copolymers, second‐generation polyglycerol dendrons are directly attached to the polymer backbone, while for the other a hydrophilic linker is placed in between. The results show that the branching of the hydrophilic pendants affects the local structure of the folded copolymer but does not influence the overall conformation and single‐chain character of the folded copolymers in solution. All copolymers fold into 4–5 nm single‐chain polymeric nanoparticles with a very compact spherical morphology, independent of the dendritic content of the copolymer. Intriguingly, the incorporation of the dendritic pendants affects the formation of a structured interior even at low incorporation ratios. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 411–421 相似文献
42.
Anderson KE Siepmann JI McMurry PH VandeVondele J 《Journal of the American Chemical Society》2008,130(43):14144-14147
Sulfuric acid and water clusters are important for new particle formation in the atmosphere. Recent experimental studies demonstrate that critical clusters in diverse atmospheric environments contain two acid molecules and may also include additional N-containing molecules (i.e., a base). We use first-principles molecular dynamics simulations to show that the presence of two sulfuric acid molecules in (H2SO4)m x base x (H2O)6 clusters is always sufficient to form a double ion, whereas a single acid molecule, even in the presence of a base, is not. 相似文献
43.
Wells NP McGrath MJ Siepmann JI Underwood DF Blank DA 《The journal of physical chemistry. A》2008,112(12):2511-2514
The time dependent change in the intermolecular response of solvent molecules following photoexcitation of Coumarin 102 (C102) has been measured in acetonitrile-water binary mixtures. Experiments were performed on mixtures of composition x(CH3CN) = 0.25, 0.50, 0.75, and 1.00. At low water concentrations (x(H2O) < or = 0.25) the solvent response is consistent with previous measurements probing dipolar solvation. With increasing water concentration (x(H2O) > or = 0.50) an additional response is found subsequent to dipolar solvation, exhibited as a rapid gain in the solvent's polarizability on a approximately 250 fs time scale. Monte Carlo simulations of the C102:binary mixture system were performed to quantify the number of hydrogen-bonding interactions between C102 and water. These simulations indicate that the probability of the C102 solute being hydrogen bound with two water molecules, both as donors at the carbonyl site, increases in a correlated fashion with the amplitude of the additional response in the measurements. We conclude that excitation of C102 simultaneously weakens and strengthens hydrogen bonding in complexes with two inequivalently bound waters. 相似文献
44.
Anderson KE Grauvilardell LC Hirschmann MM Siepmann JI 《The journal of physical chemistry. B》2008,112(41):13015-13021
The effect of pressure on structure and water speciation in hydrated liquid silica is examined over a range of temperatures and compositions. The Feuston-Garofalini (FG) potential is used in isobaric-isothermal Monte Carlo simulations carried out at four pressures (0.25, 1.0, 2.5, and 10 GPa) for seven temperatures (2000 < or = T < or= 9000 K) and five compositions (0.0 < or = x_w < or = 0.4). The FG potential yields a stable melt phase for p > or = 1.0 GPa and/or x_w < or = 0.1 for all temperatures. The volume minimum seen in previous simulations of pure and hydrated liquid silica using the FG potential persists up to 2.5 GPa but is no longer evident at 10 GPa. This is correlated with gradual structural changes of the liquid up to 2.5 GPa and with more significant changes at 10 GPa. Even at high overall concentrations of water (x_w = 0.4), only about 2% of oxygen atoms are present as molecular water species at the lowest temperature. This percentage decreases with increasing pressure and temperature. 相似文献
45.
Dr. Meijia Li Dr. Liqi Qiu Dr. Ilja Popovs Dr. Weiwei Yang Dr. Alexander S. Ivanov Dr. Takeshi Kobayashi Dr. Bishnu P. Thapaliya Dr. Debabrata Moitra Xinbin Yu Dr. Zili Wu Dr. Zhenzhen Yang Dr. Sheng Dai 《Angewandte Chemie (International ed. in English)》2023,62(28):e202302684
Boron-enriched scaffolds have demonstrated unique features and promising performance in the field of catalysis towards the activation of small gas molecules. However, there is still a lack of facile approaches capable of achieving high B doping and abundant porous channels in the targeted catalysts. Herein, construction of boron- and nitrogen-enriched nanoporous π-conjugated networks (BN-NCNs) was achieved via a facile ionothermal polymerization procedure with hexaazatriphenylenehexacarbonitrile [HAT(CN)6] sodium borohydride as the starting materials. The as-produced BN-NCN scaffolds were featured by high heteroatoms doping (B up to 23 wt. % and N: up to 17 wt. %) and permanent porosity (surface area up to 759 m2 g−1 mainly contributed by micropores). With the unsaturated bonded B species acting as the active Lewis acid sites and defected N species acting as the active Lewis base sites, those BN-NCNs delivered attractive catalytic performance towards H2 activation/dissociation in both gaseous and liquid phase, acting as efficient metal-free heterogeneous frustrated Lewis pairs (FLPs) catalysts in hydrogenation procedures. 相似文献
46.
Erkan Y Czolkos I Jesorka A Wilhelmsson LM Orwar O 《Langmuir : the ACS journal of surfaces and colloids》2007,23(10):5259-5263
We introduce a rapid, simple one-step procedure for the high-yield immobilization of cholesteryl-tetraethyleneglycol-modified oligonucleotides (chol-DNA) at hydrophobic sites made of SU-8 photoresist. Topographic structures of SU-8 were microfabricated on microscope glass coverslips sputtered with a Ti/Au layer. Upon application, chol-DNA adsorbed to the SU-8 structures from solution, leaving the surrounding gold surface free of chol-DNA. chol-DNA immobilization is complete within 15 min and yields a surface coverage in the range of 20-95 pmol/cm(2), which corresponds to a film density of 10(12)-10(13) molecules/cm(2). chol-DNA immobilization is stable and can be sustained despite rinsing, drying, dry storage for several hours, and rehydration of chips. Furthermore, complementary DNA in solution hybridizes efficiently to immobilized chol-DNA. 相似文献
47.
Jie Liu Maaike J. G. Schotman Marco M. R. M. Hendrix Xianwen Lou Patricia P. Marín San Román Ilja K. Voets Rint P. Sijbesma 《Journal of polymer science. Part A, Polymer chemistry》2021,59(12):1162-1170
We report on the self-assembly in water of a set of bis-urea amphiphiles. A range of techniques, including dynamic light scattering, Cryo-TEM, SAXS, and MS are used to study the effect of structural variation on the morphology of the assemblies. The length, dispersity, and end-group of the ethylene glycol hydrophilic part of the molecule, as well as of the alkyl chain length are varied to tailor the morphology towards soluble wormlike micelles. Slight modification on molecular structures gave a large difference in self-assembly behavior in water, giving guidelines for the design of rodlike supramolecular fibers with novel functionalities, such as strain-stiffening and bioactivity. 相似文献
48.
Victorio Saez Talens Dr. Pablo Englebienne Dr. Thuat T. Trinh Willem E. M. Noteborn Dr. Ilja K. Voets Dr. Roxanne E. Kieltyka 《Angewandte Chemie (International ed. in English)》2015,54(36):10502-10506
The synergy of aromatic gain and hydrogen bonding in a supramolecular polymer is explored. Partially aromatic bis(squaramide) bolaamphiphiles were designed to self‐assemble through a combination of hydrophobic, hydrogen‐bonding, and aromatic effects into stiff, high‐aspect‐ratio fibers. UV and IR spectroscopy show electron delocalization and geometric changes within the squaramide ring indicative of strong hydrogen bonding and aromatic gain of the monomer units. The aromatic contribution to the interaction energy was further supported computationally by nucleus‐independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) indices, demonstrating greater aromatic character upon polymerization: at least 30 % in a pentamer. The aromatic gain–hydrogen bonding synergy results in a significant increase in thermodynamic stability and a striking difference in aggregate morphology of the bis(squaramide) bolamphiphile compared to isosteres that cannot engage in this effect. 相似文献
49.
Molecular simulations of water/acetonitrile and water/methanol mobile phases in contact with a C(18) stationary phase were carried out to examine the molecular-level effects of mobile phase composition on structure and retention in reversed-phase liquid chromatography. The simulations indicate that increases in the fraction of organic modifier increase the amount of solvent penetration into the stationary phase and that this intercalated solvent increases chain alignment. This effect is slightly more apparent for acetonitrile containing solvents. The retention mechanism of alkane solutes showed contributions from both partitioning and adsorption. Despite changes in chain structure and solvation, the molecular mechanism of retention for alkane solutes was not affected by solvent composition. The mechanism of retention for alcohol solutes was primarily adsorption at the interface between the mobile and stationary phase, but there were also contributions from interactions with surface silanols. The interaction between the solute and surface silanols become very important at high concentrations of acetonitrile. 相似文献
50.
M Lemmers E Spruijt S Akerboom IK Voets AC van Aelst MA Cohen Stuart J van der Gucht 《Langmuir : the ACS journal of surfaces and colloids》2012,28(33):12311-12318
We have prepared an aqueous physical gel consisting of negatively charged silica nanoparticles bridged by ABA triblock copolymers, in which the A blocks are positively charged and the B block is neutral and water-soluble. Irreversible aggregation of the silica nanoparticles was prevented by precoating them with a neutral hydrophilic polymer. Both the elastic plateau modulus and the relaxation time increase slowly as the gel ages, indicating an increase both in the number of active bridges and in the strength with which the end blocks are adsorbed. The rate of this aging process can be increased significantly by applying a small shear stress to the sample. Our results indicate that charge-driven bridging of nanoparticles by triblock copolymers is a promising strategy for thickening of aqueous particle containing materials, such as water-based coatings. 相似文献