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31.
In this study,new types of hybrid gold poly(methyl methacrylate) (PMMA) nanomaterials are synthesized.Both PMMA spheres coated with gold nanoparticles and gold nanoparticles coated with PMMA can be synthesized using different ratios of HAuCl4 and MMA precursors,by exposing the mixtures to hard X-ray synchrotron radiation without the use of a reducing agent.According to the photochemical mechanism,gold nanoparticles will precipitate from a solution of HAuCl4 on exposure to synchrotron radiation,followed by the synthesis of PMMA by the polymerization of MMA monomers.These reactions can result in the formation of two different types of new hybrid nanomaterials.When a 1:1 volume ratio of HAuCl4 to MMA is used,we obtain PMMA spheres coated with gold nanoparticles.When a 10:1 ratio of HAuCl4 and MMA is used,we obtain gold nanoparticles coated with PMMA.The hybrid gold/PMMA nanostructures are characterized by transmission electron microscopy,elemental analysis,dynamic-light scattering analysis,gel permeation chromatography and Raman spectroscopy.The hybrid nanomateriais have potential application in the fields of biosensors and drug delivery. 相似文献
32.
A Kuznetsova I Popova J T Yates M J Bronikowski C B Huffman J Liu R E Smalley H H Hwu J G Chen 《Journal of the American Chemical Society》2001,123(43):10699-10704
Single-walled nanotubes (SWNTs) produced by plasma laser vaporization (PLV) and containing oxidized surface functional groups have been studied for the first time with NEXAFS. Comparisons are made to SWNTs made by catalytic synthesis over Fe particles in high-pressure CO, called HiPco material. The results indicate that the acid purification and cutting of single-walled nanotubes with either HNO3/H2SO4 or H2O2/H2SO4 mixtures produces the oxidized groups (O/C = 5.5-6.7%), which exhibit both pi*(CO) and sigma*(CO) C K-edge NEXAFS resonances. This indicates that both carbonyl (C=O) and ether C-O-C functionalities are present. Upon heating in a vacuum to 500-600 K, the pi*(CO) resonances are observed to decrease in intensity; on heating to 1073 K, the sigma*(CO) resonances disappear as the C-O-C functional groups are decomposed. Raman spectral measurements indicate that the basic tubular structure of the SWNTs is not perturbed by heating to 1073 K, based on the invariance of the ring breathing modes upon heating. The NEXAFS studies agree well with infrared studies which show that carboxylic acid groups are thermally destroyed first, followed by the more difficult destruction of ether and quinone groups. Single-walled nanotubes produced by the HiPco process, and not treated with oxidizing acids, exhibit an O/C ratio of 1.9% and do not exhibit either pi*(CO) or sigma*(CO) resonances at the detection limit of NEXAFS. It is shown that heating (to 1073 K) of the PLV-SWNTs containing the functional groups produces C K-edge NEXAFS spectra very similar to those seen for the HiPco material. The NEXAFS spectra are calibrated against spectra measured for a number of fused-ring aromatic hydrocarbon molecules containing various types of oxidized functional groups present on the oxidized SWNTs. 相似文献
33.
34.
A new family of salt-containing, mixed-metal silicates (CU-14), Ba6Mn4Si12O34Cl3 (1) and Ba6Fe5Si11O34Cl3 (2), was synthesized via the BaCl2 salt-inclusion reaction. These compounds crystallize in the noncentrosymmetric (NCS) space group Pmc2(1) (No. 26), adopting 1 of the 10 NCS polar, nonchiral crystal classes, mm2 (C2v). The cell dimensions are a = 6.821(1) A, b = 9.620(2) A, c = 13.172(3) A, and V = 864.4(3) A3 for 1 and a = 6.878(1) A, b = 9.664(2) A, c = 13.098(3) A, and V = 870.6(3) A3 for 2. The structures form a composite framework made of the (M(4+x)Si(12-x)O34)9- (M = Mn, x = 0; M = Fe, x = 1) covalent oxide and (Ba6Cl3)9+ ionic chloride sublattices. The covalent framework exhibits a pseudo-one-dimensional channel where the extended barium chloride lattice (Ba3Cl1.5)(infinity) resides, and it consists of fused eight-membered meta-silicate rings propagating along [100] via sharing two opposite [Si2O7]6- units to form an acentric lattice. Single-crystal structure studies also reveal the ClBa4 unit adopting an interesting seesaw configuration, in which the lone pair electrons of chlorine preferentially face the oxide anions of the transition metal silicate channel, thus forming the observed polar frameworks. Similar to the synthesis of organic-inorganic hybrid materials, the salt-inclusion method facilitates a promising approach for the directed synthesis of special framework solids, including NCS compounds, via composite lattices. 相似文献
35.
The addition of reactive carbanions to tricarbonyl(η4-1,3-diene)iron(0) complexes proceeded at ?78 °C to give putative tricarbonyl(η1,η2-but-3-en-1-y1)iron(0) anion complexes and at 25 °C to produce postulated tricarbonyl(η3-allyl)iron(O) anion complexes; trapping of reactive intermediates with dioxygen produced γ,δ-unsaturated acids and allylic alcohols, respectively. 相似文献
36.
37.
Jyh-Chen Chen Gwo-Jiun Sheu Farn-Shiun Hwu Hsueh-I Chen Jinn-Kong Sheu Tsung-Xian Lee Ching-Cherng Sun 《Optical Review》2009,16(2):213-215
The effects of current distribution in LED chips on the electrical potential and optical light extraction efficiency are investigated
by a numerical simulation. The results show that when the resistivity of the current-spreading layer is decreased there is
current-crowding near the n-contact. On the other hand, when the resistivity in the current-spreading layer increases, there
is current-crowding near the p-contact. When the current is crowded near the n-contact due to less resistivity of the current-spreading
layer, the input power is lower because of the smaller series resistance in the chip, and the light extraction efficiency
is higher since the shadowing effect of the p-contact can be avoided. For L
p = 50 μm in this study, the light extraction efficiency at ρ
ITO = 0.1 × 10−3 Ω·cm is 1.4 times better than that when L
p = 100 μm, even though the driving voltage is raised 1.02 times. 相似文献
38.
The Characterization of Organic Modified Montmorillonite and Its Filled PMMA Nanocomposite 总被引:2,自引:0,他引:2
Z. Gao W. Xie J. M. Hwu L. Wells W.-P. Pan 《Journal of Thermal Analysis and Calorimetry》2001,64(2):467-475
Thermogravimetric analysis (TG) and Fourier transform infrared (FTIR)results of commercial montmorillonite were compared to
that exchanged with trimethyloctadecyl quaternary ammonium chloride (SCPX2048), both were treated up to500°C. The time-of-flight
mass spectrometer (TOF/MS) results of SCPX2048 trapped under300 and 500°C were compared with that of N,N,Ntrimethyl-1-dodecanammonium
chloride(A 18-50) trapped under 200 and 300°C. The degradation mechanism of organic modified montmorillonite was proposed.
PMMA-clay nanocomposite was synthesized through intercalation method and its properties were examined by both TG and DSC techniques.
The thermal stability and glass transition temperature of montmorillonite filled PMMA increase comparing with that of the
pure PMMA.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
39.
Pei‐Cheng Hsu Yu‐Sheng Chen Yeukuang Hwu J. H. Je G. Margaritondo Eng Soon Tok 《Journal of synchrotron radiation》2015,22(6):1524-1527
X‐ray irradiation is shown to trigger the deposition of Cu from solution, at room temperature, on a wide variety of insulating substrates: glass, passivated Si, TiN/Ti/SiO2/Si and photoresists like PMMA and SU‐8. The process is suitable for patterning and the products can be used as seeds for electroplating of thicker overlayers. 相似文献
40.
Growth mechanism of gold nanoparticles decorated on polystyrene spheres via self-regulated reduction
Chang-Pin Chang Chun-Chieh Tseng Jinn-Luh Ou Wen-Hwa Hwu Ming-Der Ger 《Colloid and polymer science》2010,288(4):395-403
Uniform polystyrene (PS) microspheres prepared for deposition of metallic nanoparticles were synthesized using the surfactant-free
emulsion polymerization based on styrene/potassium persulfate/water (St/KPS/H2O) system. Owing to the presence of sulfate groups, the PS microspheres can be utilized to reduce gold nanoparticles without
adding extra reducing agent into the mixture. The synthesis and characterization of metal-polystyrene nanocomposites are reported,
and a possible reduction mechanism is proposed: by heating the aqueous solution in the presence of metal ions and PS, the
sulfate chain end groups of the PS hydrolyzed and transformed to hydroxyl groups firstly. The hydroxyl groups function as
a reducing agent, and carboxylic groups provide a site to adsorb the gold nuclei. The Au nanoparticles grow in size with the
coalescence and dissolving of nuclei through the Ostwald ripening process. The PS microspheres and Au nanoparticles were characterized
by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray power
diffraction, and thermal gravimetric analysis. 相似文献