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141.
The effect of axial ligands on the reactivity of high-valent iron(IV) oxo-porphyrins (Compound I) was investigated using the B3LYP hybrid density functional method. We studied alkane hydroxylation using four models: Compound I with thiolate, imidazole, phenolate, and chloride anions as axial ligands. The first three ligands were employed as models for cysteinate, histidine, and tyrosinate, respectively. Our calculations show that anionic ligands and neutral ligands favor different electronic states for stationary points in the reaction coordinate, and the calculated energy barrier and energy of several reaction intermediates show similar values. A remarkable effect of axial ligands was found in the final product release step. Our calculations show that the thiolate ligand weakens a bond between heme and an alcohol. In contrast, the imidazole ligand significantly increases the interaction between heme and an alcohol, which causes the catalytic cycle to be less efficient. 相似文献
142.
JiHyeon Hwang Youngson Choe Joona Bang Anzar Khan 《Journal of polymer science. Part A, Polymer chemistry》2017,55(20):3381-3386
Proton transfer polymerization through thiol‐epoxy “click” reaction between commercially available and hydrophilic di‐thiol and di‐epoxide monomers is carried out under ambient conditions to furnish water‐soluble polymers. The hydrophilicity of monomers permitted use of aqueous tetrahydrofuran as the reaction medium. A high polarity of this solvent system in turn allowed for using a mild catalyst such as triethylamine for a successful polymerization process. The overall simplicity of the system translated into a simple mixing of monomers and isolation of the reactive polymers in an effortless manner and on any scale required. The structure of the resulting polymers and the extent of di‐sulfide defects are studied with the help of 13C‐ and 1H‐NMR spectroscopy. Finally, reactivity of the synthesized polymers is examined through post‐polymerization modification reaction at the backbone sulfur atoms through oxidation reaction. The practicality, modularity, further functionalizability, and water solubility aspects of the described family of new poly(β‐hydroxythio‐ether)s is anticipated to accelerate investigations into their potential utility in bio‐relevant applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3381–3386 相似文献
143.
Sang‐Soo Lee Junkyung Kim Min Park Soonho Lim Chul Rim Choe 《Journal of Polymer Science.Polymer Physics》2001,39(21):2589-2597
For the poly(butylene terephthalate) (PBT)/poly(ethylene terephthalate) blend system, the addition of a barium sulfate (BaSO4) particle, the surface of which was modified with a titanate coupling agent, suppressed the transesterification reaction. The polyester chain ends, considered one of the main sites of transesterification reactions, were blocked through a chemical reaction with the surface hydroxyl groups of the BaSO4 particle; a block copolymer‐like architecture was obtained with a BaSO4 linkage. The formation of the block copolymer‐like structure for the polyesters stuck to the BaSO4 particle facilitated crystallization by providing a crystallization nucleus without a significant transesterification reaction, resulting in higher mechanical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2589–2597, 2001 相似文献
144.
We consider asymptotic behavior of Leray’s solution which expresses axis-symmetric incompressible Navier–Stokes flow past
an axis-symmetric body. When the velocity at infinity is prescribed to be nonzero constant, Leray’s solution is known to have
optimum decay rate, which is in the class of physically reasonable solution. When the velocity at infinity is prescribed to
be zero, the decay rate at infinity has been shown under certain restrictions such as smallness on the data. Here we find
an explicit decay rate when the flow is axis-symmetric by decoupling the axial velocity and the horizontal velocities.
The first author was supported by KRF-2006-312-C00466. The second author was supported by KRF-2006-531-C00009. 相似文献
145.
We have examined the unusual behavior of wave propagation in the BrO3
- - 1,4- cyclohexanedione - ferroin reaction system. Two patterns of traveling wave have been induced spontaneously with long
time lag in the reaction process. A new wave has been induced as a concentric pattern after an initially induced wave has
disappeared. The initially induced wave shows an irregular spiral pattern with a high wave frequency. The two waves show very
different behavior in the pattern and in other wave characteristics as well. We compared the behavior of the two waves and
suggested an appropriate reaction process for unusual behavior of wave propagation in the system by considering the reaction
intermediates of the organic compounds.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
146.
Siwon Jang Sang Gon Lee Chang Hwy Lim Hyun Ok Kim Sang Yeol Kim Seung Hun Lee Joohwan Hong Juhyeok Jang Taemin Jeon Myung Kook Moon Wonho Choe 《Current Applied Physics》2013,13(5):819-825
An advanced tangential X-ray pinhole camera (TXPC) has been developed for KSTAR by utilizing a 2-D duplex multi-wire proportional counter (MWPC) detector. The KSTAR MWPC employs a 2-D parallel type readout system for high temporal resolution and adopts a duplex type for the capability of electron temperature measurement via the multi-color method. This paper presents the performance test result of the developed MWPC system utilizing a Fe-55 X-ray source. As a preliminary experimental result from the 2012 KSTAR campaign, the clear presentation of sawtooth activities and its frequency change, and 2-D plasma images during the vertical disruption event are given. 相似文献
147.
Charles Kung Jeff Hixon Sung Choe Kevin Marks Stefan Gross Erin Murphy Byron DeLaBarre Giovanni Cianchetta Shalini Sethumadhavan Xiling Wang Shunqi Yan Yi Gao Cheng Fang Wentao Wei Fan Jiang Shaohui Wang Kevin Qian Jeff Saunders Ed Driggers Hin Koon Woo Lenny Dang 《Chemistry & biology》2012,19(9):1187-1198
148.
Sang‐Soo Lee Choon Soo Lee Myong‐Hoon Kim Seung Yup Kwak Min Park Soonho Lim Chul Rim Choe Junkyung Kim 《Journal of Polymer Science.Polymer Physics》2001,39(20):2430-2435
In the melt intercalation of cation‐exchange clay, mixtures of montmorillonite and poly(styrene‐co‐acrylonitrile) (SAN) with various acrylonitrile contents were studied to examine the effect of specific interaction. When organic molecules with hydroxyl groups were used as intercalants for the clay, the amount of SAN penetrating the gallery of the layered structure of the clay and the corresponding increase in the gallery height occurred at a much higher rate because of the attractive specific interaction between acrylonitrile groups and polar groups on the clay surface. However, there was a limit to the increase in the gallery height, and the tendency for the gallery height to increase with the acrylonitrile group content disappeared when the acrylonitrile content was greater than 30 wt %, implying that excessive attractive interaction on the clay surfaces and polymer molecules glued the two adjacent silicate layers together; consequently, the increase in the gallery height could not be accomplished. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2430–2435, 2001 相似文献
149.
In this article, we derive the L2 spatial decay rate of a weak solution of the incompressible flow in the half space. When the half space (or some other fluid region with boundary) is concerned, pressure estimate is main obstacle since we do not have enough information of the pressure on the boundary. In this paper, we give an idea which does not require any pressure information on the boundary, and we hope that our idea could be applied to other problems such as exterior domain problem. 相似文献
150.
Optimized 2DE sample preparation protocols that maximize total protein recovery are fundamental to improving proteome capture and increasing the utility of 2DE, which is in part limited by inadequate recovery of proteins with diverse physicochemical properties. Maintaining protein solubility is an important factor for protein recovery, but the multitude of solubility-enhancing agents and the relatively low-throughput nature of 2DE limit the systematic study of sample preparation. In this work, design of experiment (DOE) approaches are used to optimize protein recovery by altering the levels of four solubility-enhancing agents (urea, DTT, CHAPS, and SDS) in the initial suspension solution. Protein recovery is quantified by a total protein concentration assay, which is demonstrated to be representative of SDS-PAGE and 2DE recovery. DOE methodologies are presented as relatively high-throughput procedures for optimizing 2DE sample preparation parameters for a variety of sample types. Optimal suspension solution compositions are shown to vary across a model protein solution (no urea or DTT), Chinese hamster ovary (CHO) cell lysate (8 M urea, ≥2% CHAPS, ≥32.5 mM DTT), and Escherichia coli cell lysate (8 M urea, 4% CHAPS, 65 mM DTT), with optimized conditions increasing 2DE protein recovery at least 50% compared to suboptimal conditions. 相似文献