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排序方式: 共有245条查询结果,搜索用时 62 毫秒
191.
Aidan J. Quinn 《Surface science》2007,601(13):2740-2745
We review our recent progress on probing the electronic properties of self-assembled arrays of ligand-stabilized gold nanocrystals via charge transport measurements on both laterally- and vertically-contacted arrays. We show that the electronic properties of these assemblies can be manipulated through experimental control of the nanocrystal diameter, the array formation conditions and the nature of the protecting ligand. 相似文献
192.
Elastically Flexible Crystals have Disparate Mechanisms of Molecular Movement Induced by Strain and Heat 下载免费PDF全文
Dr. Aidan J. Brock Jacob J. Whittaker Joshua A. Powell Dr. Michael C. Pfrunder Dr. Arnaud Grosjean Prof. Simon Parsons Prof. John C. McMurtrie Prof. Jack K. Clegg 《Angewandte Chemie (International ed. in English)》2018,57(35):11325-11328
Elastically flexible crystals form an emerging class of materials that exhibit a range of notable properties. The mechanism of thermal expansion in flexible crystals of bis(acetylacetonato)copper(II) is compared with the mechanism of molecular motion induced by bending and it is demonstrated that the two mechanisms are distinct. Upon bending, individual molecules within the crystal structure reversibly rotate, while thermal expansion results predominantly in an increase in intermolecular separations with only minor changes to molecular orientation through rotation. 相似文献
193.
194.
The synthesis and characterisation of a series of [RuII(bpy)2L] and [Ir(ppy)2L] complexes containing ligands L with the potential to engage in triple hydrogen bonding interactions is described. L1 and L2 comprise pyridyl triazole chelating units with pendant diaminotriazine units, capable of donor‐acceptor‐donor (DAD) hydrogen bonding, while L3 and L4 contain ADA hydrogen bonding units proximal to N^N and N^O cleating sites, respectively. X‐ray crystallography shows the L1 and L2 containing RuII complexes to assemble via hydrogen bonding dimers, while [RuII(bpy)2L 4 ] assembles via extended hydrogen bonding motifs to form one dimensional chains. By contrast, the expected hydrogen bonding patterns are not observed for the RuII and IrIII complexes of L3 . Spectroscopic studies show that the absorption spectra of the complexes result from combinations of MLCT and LLCT transitions. The L1 and L2 complexes of IrIII and RuII complexes are emissive in the solid state and it seems likely that hydrogen bonding to complementary species may facilitate tuning of their 3ILCT emission. Low frequency Raman spectra provide further evidence for ordered interactions in the solid state for the L4 complexes, consistent with the results from X‐ray crystallography. 相似文献
195.
Aidan P. Cooney Michael R. Crampton Michael Jones Peter Golding 《Journal of heterocyclic chemistry》1987,24(4):1163-1167
[15N4]-Hexamethylenetetramine (Hexamine), and [15N4]-3,7-diacetyl-1,3,5,7-tetraazabicyclo[3.3.1]nonane(DAPT) have been prepared starting from 15NH3. Synthetic acetolysis reactions were performed using mixtures of pure [15N4]- and [14N4]-compounds and the destination of the nitrogen isotopes in the products was determined mass spectrometrically. The results show that relatively little isotopic mixing occurs in the acetolysis of hexamine to DAPT though the formation of some products with isotopic composition [14N315N1] and [14N115N3] indicates limited ring cleavage. However the more severe conditions used in the formation of 1,3,5-triacetyl-1,3,5-triazacyclohexane (TRAT) give rise to considerable isotopic scrambling. The acetolysis of DAPT to give 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane occurs by selective cleavage of the methylene bridge. 相似文献
196.
Bioinspired growth of crystalline carbonate apatite on biodegradable polymer substrata 总被引:12,自引:0,他引:12
Mineralization in biological systems is a widespread, yet incompletely understood phenomenon involving complex interactions at the biomacromolecule-mineral nucleus interface. This study was aimed at understanding and controlling mineral formation in a poly(alpha-hydroxy ester) model system, to gain insight into biological mineralization processes and to develop biomaterials for orthopaedic tissue regeneration. We specifically hypothesized that providing a high surface density of anionic functional groups would enhance nucleation and growth of bonelike mineral following exposure to simulated body fluids (SBF). Polymer surface functionalization was achieved via hydrolysis of 85:15 poly(lactide-co-glycolide) (PLG) films. This treatment led to an increase in surface carboxylic acid and hydroxyl groups, resulting in a substantial increase in polymer surface energy from 42 to 49 dynes/cm2. Treated polymers exhibited a 3-fold increase in heterogeneous mineral grown and growth of a continuous mineral film on the polymer surface. The mineral grown on PLG surfaces is a carbonate apatite, the major mineral component of vertebrate bone tissue. Mineral crystal size and morphology were dependent on the solution characteristics but unaffected by the degree of surface prehydrolysis. The mechanism of heterogeneous carbonate apatite growth was examined via ion binding assays, which indicated that calcium binding is mediated independently by the presence of soluble phosphate counterions and surface functional groups. These findings indicate that poly(alpha-hydroxy ester) materials can be readily mineralized using a biomimetic process, and that the impetus for mineral nucleation in this system appears more complicated than the simple electrostatic interactions proposed in previous biomineralization theory. 相似文献
197.
One‐Step Microfluidic Fabrication of Polyelectrolyte Microcapsules in Aqueous Conditions for Protein Release 下载免费PDF全文
Dr. Liyuan Zhang Dr. Li‐Heng Cai Dr. Philipp S. Lienemann Dr. Torsten Rossow Dr. Ingmar Polenz Queralt Vallmajo‐Martin Dr. Martin Ehrbar Dr. Hui Na Dr. David J. Mooney Dr. David A. Weitz 《Angewandte Chemie (International ed. in English)》2016,55(43):13470-13474
We report a microfluidic approach for one‐step fabrication of polyelectrolyte microcapsules in aqueous conditions. Using two immiscible aqueous polymer solutions, we generate transient water‐in‐water‐in‐water double emulsion droplets and use them as templates to fabricate polyelectrolyte microcapsules. The capsule shell is formed by the complexation of oppositely charged polyelectrolytes at the immiscible interface. We find that attractive electrostatic interactions can significantly prolong the release of charged molecules. Moreover, we demonstrate the application of these microcapsules in encapsulation and release of proteins without impairing their biological activities. Our platform should benefit a wide range of applications that require encapsulation and sustained release of molecules in aqueous environments. 相似文献
198.
Timothy I. Mattox James P. Larentzos Stan G. Moore Christopher P. Stone Daniel A. Ibanez Aidan P. Thompson 《Molecular physics》2018,116(15-16):2061-2069
ABSTRACTSimulating energetic materials with complex microstructure is a grand challenge, where until recently, an inherent gap in computational capabilities had existed in modelling grain-scale effects at the microscale. We have enabled a critical capability in modelling the multiscale nature of the energy release and propagation mechanisms in advanced energetic materials by implementing, in the widely used LAMMPS molecular dynamics (MD) package, several novel coarse-graining techniques that also treat chemical reactivity. Our innovative algorithmic developments rooted within the dissipative particle dynamics framework, along with performance optimisations and application of acceleration technologies, have enabled extensions in both the length and time scales far beyond those ever realised by atomistic reactive MD simulations. In this paper, we demonstrate these advances by modelling a shockwave propagating through a microstructured material and comparing performance with the state-of-the-art in atomistic reactive MD techniques. As a result of this work, unparalleled explorations in energetic materials research are now possible. 相似文献
199.
Oguz Kagan Coskun Saudagar Dongare Brian Doherty Aidan Klemm Mark Tuckerman Burcu Gurkan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202312163
Electrochemical CO2 reduction (CO2RR) on copper (Cu) shows promise for higher-value products beyond CO. However, challenges such as the limited CO2 solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion-CO2 adducts and a hydrogen bond donor (HBD) upon CO2 absorption to modulate CO2RR on Cu in a non-aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface-enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum-mechanical/molecular mechanics (IC-QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO2 availability, reduced overpotential, and suppressed HER where C4 products are obtained. This study deepens the understanding of electrolyte effects in CO2RR and the role of IL ions towards electrocatalytic microenvironment design. 相似文献
200.
Nihal Engin Vrana Yurong Liu Garret Brian McGuinness Paul Aidan Cahill 《Macromolecular Symposia》2008,269(1):106-110
In this study, PVA/Chitosan hydrogels were fabricated by freeze/thaw cycles and further crosslinking with a KOH/Na2SO4 coagulation bath and the effect of freeze/thaw cycle number on cell behaviour was evaluated. The surface of the hydrogels were further modified with Collagen type I adsorption and seeded with bovine aortic vascular smooth muscle and endothelial cells. Increasing the number of freeze/thaw cycles resulted in a marked change in surface morphology, hydrophilicity and protein adsorption. Collagen coating caused an increase in initial attachment and proliferation. We concluded that hydrogels that have undergone 3 freeze/thaw cycles were optimum for cell attachment both in the presence and the absence of coating. 相似文献