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排序方式: 共有399条查询结果,搜索用时 31 毫秒
91.
Leila Moura Mark Gilmore Samantha K. Callear Tristan G. A. Youngs 《Molecular physics》2019,117(22):3364-3375
92.
Layer‐by‐layer assembly of readily detachable chitosan and poly(acrylic acid) polyelectrolyte multilayer films 下载免费PDF全文
Free‐standing layer‐by‐layer (LbL) assembled thin films have recently found utility in a broad range of applications. Previously reported free‐standing LbL films have generally required covalent modifications to improve aqueous stability and render these films suitable for biomedical applications. Here, we engineered chitosan and poly(acrylic acid) containing polyelectrolyte multilayer films, which are readily detached from hydrophilic silicon in aqueous conditions. These films demonstrate remarkable stability over 28 days in simulated in vivo conditions (pH 7.4, phosphate buffered saline at 37 °C) without the incorporation of any covalent crosslinking modifications. These films exhibit moduli (27–420 kPa) resembling that of many biological tissues including tendon, show high visible light transmittance of greater than 50%, and prevent fibronectin adsorption. The properties of this new detachable LbL film architecture indicate its promise for use in a variety of applications, particularly in medicine and biotechnology. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 127–131 相似文献
93.
Dr. Sumanta Banerjee Peter A. Macdonald Dr. Samantha A. Orr Dr. Alan R. Kennedy Alexander van Teijlingen Dr. Stuart D. Robertson Prof. Tell Tuttle Prof. Robert E. Mulvey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(55):e202201085
A series of group 1 hydrocarbon-soluble donor free aluminates [AM(tBuDHP)(TMP)Al(iBu)2] (AM=Li, Na, K, Rb) have been synthesised by combining an alkali metal dihydropyridyl unit [(2-tBuC5H5N)AM)] containing a surrogate hydride (sp3 C−H) with [(iBu)2Al(TMP)]. These aluminates have been characterised by X-ray crystallography and NMR spectroscopy. While the lithium aluminate forms a monomer, the heavier alkali metal aluminates exist as polymeric chains propagated by non-covalent interactions between the alkali metal cations and the alkyldihydropyridyl units. Solvates [(THF)Li(tBuDHP)(TMP)Al(iBu)2] and [(TMEDA)Na(tBuDHP)(TMP)Al(iBu)2] have also been crystallographically characterised. Theoretical calculations show how the dispersion forces tend to increase on moving from Li to Rb, as opposed to the electrostatic forces of stabilization, which are orders of magnitude more significant. Having unique structural features, these bimetallic compounds can be considered as starting points for exploring unique reactivity trends as alkali-metal-aluminium hydride surrog[ATES]. 相似文献
94.
Samantha J Cloake Her Shuang Toh Patricia T Lee Chris Salter Colin Johnston Richard G Compton 《ChemistryOpen》2015,4(1):22-26
The influence of nanoparticle aggregation on anodic stripping voltammetry is reported. Dopamine-capped silver nanoparticles were chosen as a model system, and melamine was used to induce aggregation in the nanoparticles. Through the anodic stripping of the silver nanoparticles that were aggregated to different extents, it was found that the peak area of the oxidative signal corresponding to the stripping of silver to silver(I) ions decreases with increasing aggregation. Aggregation causes incomplete stripping of the silver nanoparticles. Two possible mechanisms of ‘partial oxidation’ and ‘inactivation’ of the nanoparticles are proposed to account for this finding. Aggregation effects must be considered when anodic stripping voltammetry is used for nanoparticle detection and quantification. Hence, drop casting, which is known to lead to aggregation, is not encouraged for preparing electrodes for analytical purposes. 相似文献
95.
Amy R. Stefan Christopher R. Dockery Alexander A. Nieuwland Samantha N. Roberson Brittany M. Baguley James E. Hendrix Stephen L. Morgan 《Analytical and bioanalytical chemistry》2009,394(8):2077-2085
The extraction and separation of dyes present on textile fibers offers the possibility of enhanced discrimination between
forensic trace fiber evidence. An automated liquid sample handling workstation was programmed to deliver varying solvent combinations
to acid-dyed nylon samples, and the resulting extracts were analyzed by an ultraviolet/visible microplate reader to evaluate
extraction efficiencies at different experimental conditions. Combinatorial experiments using three-component mixture designs
varied three solvents (water, pyridine, and aqueous ammonia) and were employed at different extraction temperatures for various
extraction durations. The extraction efficiency as a function of the three solvents (pyridine/ammonia/water) was modeled and
used to define optimum conditions for the extraction of three subclasses of acid dyes (anthraquinone, azo, and metal complex)
from nylon fibers. The capillary electrophoresis analysis of acid dye extracts is demonstrated using an electrolyte solution
of 15 mM ammonium acetate in acetonitrile/water (40:60, v/v) at pH 9.3. Excellent separations and discriminating diode array spectra are obtained even for dyes of similar color.
Figure Capillary electropherogram of three acid dyes extracted from nylon 6,6 thread 相似文献
96.
2 + 4] and [4 + 2] cycloadditions of o-thioquinones with 1,3-dienes: a computational study 总被引:1,自引:0,他引:1
Contini A Leone S Menichetti S Viglianisi C Trimarco P 《The Journal of organic chemistry》2006,71(15):5507-5514
Cycloadditions of o-thioquinones (o-TQs) with 1,3-dienes could proceed via either a [2 + 4] or a [4 + 2] mechanism. Under kinetic control and with acyclic dienes the reaction affords the spiro cycloadducts 5deriving from the [2 + 4] path as the main products. Under thermodynamic control, or with cyclic dienes, the o-TQs behave as heterodienes to give the benzoxathiin derivatives 4, in most cases with complete regioselectivity. In the present computational study, DFT calculations were performed in order to achieve a deep understanding of both [2 + 4] and [4 + 2] paths. The reactions of three o-TQs with six 1,3-dienes were thoroughly investigated at the B3LYP/TZVP//B3LYP6-31G level, and the two reaction mechanisms were then compared, evidencing that [2 + 4] cycloadditions are kinetically favored, strongly asynchronous, or even unconcerted, while [4 + 2] reactions are thermodynamically favored, quite asynchronous, but undoubtedly concerted. Moreover, the observed regioselectivity was rationalized by mean of the FMO theory and by comparison of the activation energies for different pathways. 相似文献
97.
The structure and chemical states of the Sn/Ge(111) surface are characterized by x-ray standing waves combined with photoemission. For the room temperature square root 3xsquare root 3 phase two chemical components, approximately 0.4 eV apart, are observed for both Sn 3d and 4d core levels. Our model-independent, x-ray standing wave analysis shows unambiguously that the two components originate from Sn adatoms located at two different heights separated vertically by 0.23 A, in favor of a model composed of a fluctuating Sn layer. Contrary to the most accepted scenario, the stronger Sn 3d and 4d components, which appear at the lower binding-energy sides and account for 2/3 of the Sn adatoms, are identified to be associated with the higher Sn position, manifesting their filled valence state character. 相似文献
98.
99.
Atkinson SD Almond MJ Hollins P Jenkins SL 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(3):629-635
Infrared and Raman microspectroscopy have been used to follow the photodimerisation reactions of single crystals, the alpha- and beta-forms of trans-cinnamic acid. This approach allows the starting materials and products-alpha-truxillic acid that has Ci symmetry and beta-truxinic acid, which has Cs symmetry-to be identified. It also allows the topotactic nature of the reaction to be confirmed. Attempts to produce the poorly-defined unreactive gamma-form of trans-cinnamic acid resulted only in a mixture of the alpha- and beta-forms. The findings suggest a wide role for these spectroscopic methods in monitoring solid-state organic reactions. 相似文献
100.
Sindelar V Cejas MA Raymo FM Chen W Parker SE Kaifer AE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(23):7054-7059
The formation of a highly stable inclusion complex between 2,7-dimethyldiazapyrenium (Me(2)DAP(2+)) and the cucurbit[8]uril host (CB8) was demonstrated by X-ray crystallography; MALDI-TOF mass spectrometry; and (1)H NMR, electronic absorption, and emission spectroscopy. The equilibrium association constant was determined to be 8.9(+/-0.2)x10(5) L mol(-1) from UV-visible data and 8.4(+/-1.5) x 10(5) L mol(-1) from fluorescence data. The Me(2)DAP(2+).CB8 inclusion complex acted as a host to bind compounds containing aromatic pi-donor moieties (D), such as catechol and dopamine. This point was demonstrated by (1)H NMR spectroscopy, and electrochemical and emission measurements. Fluorescence detection of the Me(2)DAP(2+).D.CB8 ternary complexes was evident in aqueous solution and on the surface of silica particles, to which fluorescent diazapyrenium units had been covalently immobilized. 相似文献