全文获取类型
收费全文 | 83篇 |
免费 | 6篇 |
专业分类
化学 | 69篇 |
力学 | 2篇 |
数学 | 6篇 |
物理学 | 12篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 7篇 |
2012年 | 7篇 |
2011年 | 15篇 |
2010年 | 5篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2000年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1993年 | 2篇 |
1985年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有89条查询结果,搜索用时 46 毫秒
41.
42.
Sergey Chernyy Jyoti P. Mahalik Rajeev Kumar Jacob Judas Kain Kirkensgaard Matthias M. L. Arras Hyeyoung Kim Lars Schulte Sokol Ndoni Gregory S. Smith Kell Mortensen Bobby G. Sumpter Thomas P. Russell Kristoffer Almdal 《Journal of polymer science. Part A, Polymer chemistry》2018,56(22):1491-1504
Fundamental understanding of microphase separation in ABC miktoarm copolymers is vital to access a plethora of nonconventional morphologies. Miktoarm stars based on poly(cis 1,4-isoprene) (I), poly(styrene) (S), and poly(2-vinylpyridine) (V) are model systems, which allow systematic studies of the effects of composition, chemical microstructure, and temperature on the thermodynamics of microphase separation. Eleven ISV-x (I:S:V = 1:1:x, v:v:v) miktoarm copolymers were synthesized by anionic polymerization affording well-defined copolymers with a variable V arm. Equilibrium bulk morphologies of all samples, as evidenced by small-angle X-ray scattering, transmission electron microscopy (TEM), and self-consistent field theory, showed a systematic transition from lamellae (x ≈ 0–0.2) to [8.8.4] tiling (x ≈ 0.6–0.9) to cylinders in undulating lamellae (x ≈ 2–4) and, finally, to hexagonally packed core–shell cylinders (x ≈ 5–8). Chemical microstructure of the I arm [poly(cis 1,4-isoprene)] versus poly(3,4-isoprene) is shown to play important role in affecting morphological behavior. To reconcile differences between ISV-x star morphologies reported in the literature and those reported herein, even for the same composition, effects of the microstructure of I arm on the Flory–Huggins parameter between I and V arms were taken into account in a qualitative manner. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1491–1504 相似文献
43.
44.
Jan Ilavsky Kristoffer K. Stokes Michael C. Berg Randy A. Mrozek Joseph L. Lenhart Frederick L. Beyer Jan W. Andzelm 《Journal of Polymer Science.Polymer Physics》2011,49(20):1479-1491
Dynamic density functional theory calculations were performed for thermoplastic elastomer gels composed of an ABA triblock copolymer immersed in a B‐attractive solvent. The triblock copolymer model was parameterized for poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS), while the solvent model was parameterized for the hydrocarbon oil tetradecane. The effect of the solvent concentration and S‐EB interaction on the morphology was investigated, where complementary experimental data was used to validate results at χABN ≈ 100. Agreement was observed at solvent volume fractions of 0.2, 0.4, and 0.6, which correspond to the cylindrical, spherical, and spherical phases, respectively. Qualitative agreement was observed for 0.8 volume fraction solvent, where a core‐shell spherical micelle morphology was found. For a 50/50 vol % mixture of polymer/solvent, the effect of solvent molecular weight on the morphology was considered, where a transition between micro and macrophase separation was predicted at a critical solvent molecular weight. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1479–1491, 2011 相似文献
45.
Fredrik Wernersson Brodin Kristoffer Lund Harald Brelid Hans Theliander 《Cellulose (London, England)》2012,19(4):1413-1423
This research aims to develop new materials based on renewable resources that can fulfill the functions necessary in the absorption core of a disposable diaper. Absorbent foam was recently produced from softwood kraft pulp by TEMPO oxidation, disintegration and freeze drying. In this study, the TEMPO-oxidized MFC was mixed with pulp fibres, thus forming a cellulosic composite, in an attempt to improve the mechanical stability of the freeze-dried absorbent material. The fibres were added in different amounts and the freeze-dried materials were evaluated for their absorption and retention properties. The results of this study suggest that the composite material has a better mechanical stability than the absorbent foam without fibres. It was shown that using spruce CTMP fibres in the composite resulted in better absorption and retention capacities than in a composite with softwood kraft pulp fibres. The higher stiffness of the CTMP fibres is a probable explanation for this difference. For the composite material with CTMP fibres, liquid porosimetry showed that pore size distribution was more or less retained when put under load. Furthermore, it was seen that the retention properties reached a maximum around 85 % CTMP fibres and 15 % TEMPO-oxidized MFC. In the centrifuge retention test, the retention of the TEMPO-oxidized MFC in the composite material reached about the same capacity as conventional superabsorbent polymers. 相似文献
46.
Lunøe K Martínez-Sierra JG Gammelgaard B Alonso JI 《Analytical and bioanalytical chemistry》2012,402(9):2749-2763
The analytical methodology for the in vivo study of selenium metabolism using two enriched selenium isotopes has been modified, allowing for the internal correction
of spectral interferences and mass bias both for total selenium and speciation analysis. The method is based on the combination
of an already described dual-isotope procedure with a new data treatment strategy based on multiple linear regression. A metabolic
enriched isotope (77Se) is given orally to the test subject and a second isotope (74Se) is employed for quantification. In our approach, all possible polyatomic interferences occurring in the measurement of
the isotope composition of selenium by collision cell quadrupole ICP-MS are taken into account and their relative contribution
calculated by multiple linear regression after minimisation of the residuals. As a result, all spectral interferences and
mass bias are corrected internally allowing the fast and independent quantification of natural abundance selenium (natSe) and enriched 77Se. In this sense, the calculation of the tracer/tracee ratio in each sample is straightforward. The method has been applied
to study the time-related tissue incorporation of 77Se in male Wistar rats while maintaining the natSe steady-state conditions. Additionally, metabolically relevant information such as selenoprotein synthesis and selenium
elimination in urine could be studied using the proposed methodology. In this case, serum proteins were separated by affinity
chromatography while reverse phase was employed for urine metabolites. In both cases, 74Se was used as a post-column isotope dilution spike. The application of multiple linear regression to the whole chromatogram
allowed us to calculate the contribution of bromine hydride, selenium hydride, argon polyatomics and mass bias on the observed
selenium isotope patterns. By minimising the square sum of residuals for the whole chromatogram, internal correction of spectral
interferences and mass bias could be accomplished. As a result, the tracer/tracee ratio could be calculated for each selenium-containing
species and a time relationship for synthesis and degradation established. Both selenite and selenized yeast labelled with
77Se were employed for comparative purposes. 相似文献
47.
Susanta Mitra Afshin Ghanbari-Siahkali Helle Kem Rehmeier Kristoffer Almdal 《Polymer Degradation and Stability》2006,91(1):69-80
The time-dependent chemical degradation of accelerated sulphur cured ethylene propylene diene rubber containing 5-ethylidene-2-norbornene as diene in an acidic environment (20% Cr/H2SO4) was investigated. Two different rubbers with a similar ethylene to propylene ratio and diene content but with a significant difference in molar mass and level of long chain branching were used in the study. The molecular mechanisms of the chemical degradation occurring at the surface were determined using surface analysis (X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy). The results reveal formation of several oxygenated species on the surface as a consequence of the acid attack. Furthermore, the crosslink sites of the exposed rubber samples are also found vulnerable to hydrolytic attack as evidenced by the decrease in crosslink density. The extent of surface degradation was strong enough to affect the bulk mechanical properties. Changes in mechanical properties were also monitored through determining retention in tensile strength, (%) elongation at break, modulus at 50% elongation, and change in micro-hardness. A negative correlation is also established between retention in modulus at 50% elongation and decrease in crosslink density. Scanning electron microscopy reveals the topographical damage at the surface due to the aqueous acid induced chemical degradation. The results indicate that the chemical degradation proceeds mainly via hydrolysis of crosslinks but upon prolonged exposure, the oxygenated species tend to combine with each other. The effect of molar mass and level of long chain branching also influences the chemical degradation. 相似文献
48.
Hideyuki Tatsuno Kasper S. Kjær Kristjan Kunnus Tobias C. B. Harlang Cornelia Timm Meiyuan Guo Pavel Chàbera Lisa A. Fredin Robert W. Hartsock Marco E. Reinhard Sergey Koroidov Lin Li Amy A. Cordones Olga Gordivska Om Prakash Yizhu Liu Mads G. Laursen Elisa Biasin Frederik B. Hansen Peter Vester Morten Christensen Kristoffer Haldrup Zoltán Németh Dorottya Sárosiné Szemes Éva Bajnóczi György Vankó Tim B. Van Driel Roberto Alonso-Mori James M. Glownia Silke Nelson Marcin Sikorski Henrik T. Lemke Dimosthenis Sokaras Sophie E. Canton Asmus O. Dohn Klaus B. Møller Martin M. Nielsen Kelly J. Gaffney Kenneth Wärnmark Villy Sundström Petter Persson Jens Uhlig 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):372-380
Iron N-heterocyclic carbene (NHC) complexes have received a great deal of attention recently because of their growing potential as light sensitizers or photocatalysts. We present a sub-ps X-ray spectroscopy study of an FeIINHC complex that identifies and quantifies the states involved in the deactivation cascade after light absorption. Excited molecules relax back to the ground state along two pathways: After population of a hot 3MLCT state, from the initially excited 1MLCT state, 30 % of the molecules undergo ultrafast (150 fs) relaxation to the 3MC state, in competition with vibrational relaxation and cooling to the relaxed 3MLCT state. The relaxed 3MLCT state then decays much more slowly (7.6 ps) to the 3MC state. The 3MC state is rapidly (2.2 ps) deactivated to the ground state. The 5MC state is not involved in the deactivation pathway. The ultrafast partial deactivation of the 3MLCT state constitutes a loss channel from the point of view of photochemical efficiency and highlights the necessity to screen transition-metal complexes for similar ultrafast decays to optimize photochemical performance. 相似文献
49.
Wouter Boomsma Jes Frellsen Tim Harder Sandro Bottaro Kristoffer E. Johansson Pengfei Tian Kasper Stovgaard Christian Andreetta Simon Olsson Jan B. Valentin Lubomir D. Antonov Anders S. Christensen Mikael Borg Jan H. Jensen Kresten Lindorff‐Larsen Jesper Ferkinghoff‐Borg Thomas Hamelryck 《Journal of computational chemistry》2013,34(19):1697-1705
We present a new software framework for Markov chain Monte Carlo sampling for simulation, prediction, and inference of protein structure. The software package contains implementations of recent advances in Monte Carlo methodology, such as efficient local updates and sampling from probabilistic models of local protein structure. These models form a probabilistic alternative to the widely used fragment and rotamer libraries. Combined with an easily extendible software architecture, this makes PHAISTOS well suited for Bayesian inference of protein structure from sequence and/or experimental data. Currently, two force‐fields are available within the framework: PROFASI and OPLS‐AA/L, the latter including the generalized Born surface area solvent model. A flexible command‐line and configuration‐file interface allows users quickly to set up simulations with the desired configuration. PHAISTOS is released under the GNU General Public License v3.0. Source code and documentation are freely available from http://phaistos.sourceforge.net . The software is implemented in C++ and has been tested on Linux and OSX platforms. © 2013 Wiley Periodicals, Inc. 相似文献
50.