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排序方式: 共有135条查询结果,搜索用时 15 毫秒
1.
Two types of optical current transducers (OCTs) have a bulk Faraday sensor inserted into the gap of an iron core and a porcelain
insulator with optical fiber. The sensor consists of Bi12SiO20 (BSO) single crystal, a polarizer, and an analyzer. The OCTs satisfied the target performance requirement for fault location
and metering and demonstrated maintained performance at some power utilities in Japan and the US. We have developed a fault
location system that immediately detects the fault current with the OCTs, there by locating the fault section. The OCT can
easily replace the existing support insulators for the disconnecting switch without any modifications to structure height
or bus-bar. For metering requiring 0.3% class accuracy, use of a BSO with right optical rotatory power combined with BSO with
left optical rotatory power results in a Faraday sensor with improved temperature characteristics. The OCT demonstrated 0.3%
class accuracy for metering described in the current transformer Specifications of IEEE C57–13, 1993. 相似文献
2.
The reaction of delta-silyl-gamma,delta-epoxypentanenitrile derivatives with a base and an alkylating agent affords delta-siloxy-gamma,delta-unsaturated pentanenitrile derivatives via a tandem process that involves the formation of the cyclopropane derivative by epoxy nitrile cyclization followed by Brook rearrangement and an anion-induced cleavage of the cyclopropane ring. 相似文献
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Manosroi A Jantrawut P Akazawa H Akihisa T Manosroi J 《Natural product research》2010,24(20):1915-1926
The aqueous extract of galls from Terminalia chebula Retz. (Combretaceae) was fractionated on Diaion and refractionated on octadecyl silica column. Six phenolic compounds were isolated and identified as gallic acid (1), punicalagin (2), isoterchebulin (3), 1,3,6-tri-O-galloyl-β-D-glucopyranose (4), chebulagic acid (5) and chebulinic acid (6). All of the compounds showed stronger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and melanin inhibitory activities than ascorbic acid, butylated hydroxytoluene, α-tocopherol, arbutin and kojic acid, the reference compounds. Gallic acid (1) exhibited inhibitory activity against nitric oxide production in lipopolysaccharide-activated macrophages. However, all isolated compounds exhibited less activity than the reference compounds in mushroom tyrosinase inhibition and human tumour cytotoxicity assays. This study has demonstrated that the phenolic compounds isolated from galls of T. chebula might contribute significantly due to their antioxidant and whitening activities. 相似文献
6.
Matsuoka H Shen JR Kawamori A Nishiyama K Ohba Y Yamauchi S 《Journal of the American Chemical Society》2011,133(12):4655-4660
The oxidation of a redox-active tyrosine residue Y(Z) in photosystem II (PSII) is coupled with proton transfer to a hydrogen-bonded D1-His190 residue. Because of the apparent proximity of Y(Z) to the water-oxidizing complex and its redox activity, it is believed that Y(Z) plays a significant role in water oxidation in PSII. We investigated the g-anisotropy of the tyrosine radical Y(Z)(?) to provide insight into the mechanism of Y(Z)(?) proton-coupled electron transfer in Mn-depleted PSII. The anisotropy was highly resolved by electron paramagnetic resonance spectroscopy at the W-band (94.9 GHz) using PSII single crystals. The g(X)-component along the phenolic C-O bond of Y(Z)(?) was calculated by density functional theory (DFT). It was concluded from the highly resolved g-anisotropy that Y(Z) loses a phenol proton to D1-His190 upon tyrosine oxidation, and D1-His190 redonates the same proton back to Y(Z)(?) upon reduction. 相似文献
7.
N. Iwasa T. Akazawa S. Ohyama K. Fujikawa N. Takezawa 《Reaction Kinetics and Catalysis Letters》1995,55(2):245-250
Pd/ZnO and Pt/ZnO exhibited high catalytic performance for the dehydrogenation of methanol to methyl formate upon the formation of PdZn and PtZn alloys. 相似文献
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Shima S Lyon EJ Thauer RK Mienert B Bill E 《Journal of the American Chemical Society》2005,127(29):10430-10435
The iron-sulfur cluster-free hydrogenase (Hmd) from methanogenic archaea harbors an iron-containing, light-sensitive cofactor of still unknown structure as prosthetic group. The enzyme is reversibly inhibited by CO and cyanide and is EPR silent. We report here on M?ssbauer spectra of the (57)Fe-labeled enzyme and of the isolated cofactor. The spectrum of the holoenzyme measured at 80 K revealed a doublet peak with an isomer shift delta = 0.06 mm.s(-)(1) and a quadrupole splitting of DeltaE(Q) = 0.65 mm.s(-)(1) (at pH 8.0). The signal intensity corresponded to the enzyme concentration assuming 1 Fe per mol active site. Upon addition of CO or cyanide to the enzyme, the isomer shift decreased to -0.03 mm.s(-)(1) and -0.00(1) mm.s(-)(1), and the quadrupole splitting increased to 1.38 mm.s(-)(1) and 1.75 mm.s(-)(1), respectively. The three spectra could be perfectly simulated assuming the presence of only one type of iron in Hmd. The low isomer shift is characteristic for Fe in a low oxidation state (0, +1, +2). When the spectra of the holoenzyme and of the CO- or cyanide-inhibited enzyme were measured at 4 K in a magnetic field of 4 and 7 T, the spectra obtained could be simulated assuming the presence of only the external magnetic field, which excludes that the iron in the active site of Hmd is Fe(I), high-spin Fe(0), or high-spin Fe(II). M?ssbauer spectra of the isolated Hmd cofactor are also reported. 相似文献
10.
(1,5-Cyclooctadiene) (4-substituted pyridinium 2-pyridylcarbonylmethylide)- rhodium(I) perchlorates, [Rh(COD)(C5H4NC(O)C?H+C5H4X-4)]ClO4 [COD = 1,5-cyclooctadiene; X = CH3C(O), CH3OC(O), C6H5, CH3, and H], have been prepared. They are shown to have the geometry with coordination by the pyridyl nitrogen and carbonyl oxygen atoms of the ylide ligands and to exhibit intramolecular rearrangement of coordinated COD in chloroform, methanol, and dimethyl sulphoxide based on IR and 1H NMR spectroscopies. Although the ylides have exhibited fluorescence bands due to an intramolecular charge-transfer transition and phosphorescence bands due to a carbonyl 3(n?π*) transition, the complexes have given emission bands due to the metal-to-ylide ligand charge-transfer transition. A.single crystal X-ray crystal structure has been determined for [Rh(COD)(C5H4NC(O)C?H+C5H4CH3-4)]ClO4. The crystals are monoclinic, space group P21/n with cell dimensions a = 14.887(3), b = 20.274(4), c = 6.966(1) Å, β = 96.13(1)°, and Z = 4. The structure has been refined by a block-diagonal least-squares method to final R = 0.060 for 2997 independent reflections with |Fo| > 3σ(F). The ylide carbon-pyridinium nitrogen bond distance is 1.420(10) Å. The bonded distances from rhodium to the midpoints of the double bonds of COD are 1.982(11) and 2.014(12) Å. 相似文献