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1.
Dynamic behaviour of river colloidal and dissolved organic matter through cross-flow ultrafiltration system 总被引:1,自引:0,他引:1
Through cross-flow filtration (CFF) with a 1-kDa regenerated cellulose Pellicon 2 module, the ultrafiltration characteristics of river organic matter from Longford Stream, UK, were investigated. The concentration of organic carbon (OC) in the retentate in the Longford Stream samples increased substantially with the concentration factor (cf), reaching approximately 40 mg/L at cf 15. The results of dissolved organic carbon (DOC) and colloidal organic carbon (COC) analysis, tracking the isolation of colloids from river waters, show that 2 mg/L of COC was present in those samples and good OC mass balance (77-101%) was achieved. Fluorescence measurements were carried out for the investigation of retentate and permeate behaviour of coloured dissolved organic materials (CDOM). The concentrations of CDOM in both the retentate and permeate increased with increasing cf, although CDOM were significantly more concentrated in the retentate. The permeation model expressing the correlation between log[CDOM] in the permeate and logcf was able to describe the permeation behaviour of CDOM in the river water with regression coefficients (r(2)) of 0.94 and 0.98. Dry weight analysis indicated that the levels of organic colloidal particles were from 49 to 71%, and between 29 and 51% of colloidal particles present were inorganic. COC as a percentage of DOC was found to be 10-16% for Longford Stream samples. 相似文献
2.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Lisheng D Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Shuchen Z Zhong Yuanyuan 《Physical review letters》1993,71(21):3417-3420
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Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Dai Lisheng Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Zheng Shuchen Zhong Yuanyuan 《Physical review letters》1993,71(14):2172-2175
4.
Teixeira-Neto É Leite CA Cardoso AH Medeiros da Silva MC Braga M Galembeck F 《Journal of colloid and interface science》2000,231(1):182-189
Poly(styrene-co-acrylamide) (PS-AAM) latex was prepared, fractionated by sedimentation under gravity, and characterized by PCS, infrared spectra, secondary and backscattered electron imaging in the scanning electron microscope, and electron spectroscopy imaging in an analytical transmission electron microscope. Three latex fractions were obtained. The lower fraction was opalescent and its particles were the more uniform, concerning size, chemical composition, and topochemical features. This lower fraction was still further fractionated by zonal centrifugation in a density gradient, yielding two fractions with similar macrocrystal-forming abilities but different sizes and chemical compositions. These results confirm those previously obtained for the PS-HEMA latex. Copyright 2000 Academic Press. 相似文献
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A method for the simultaneous measurement of trace amounts of phenolic xenoestrogens, such as 2,4-dichlorophenol (2,4-DCP), 4-tert-butyl-phenol (BP), 4-tert-octylphenol (OP), 4-nonylphenol (NP), pentachlorophenol (PCP) and bisphenol A (BPA), in water samples was developed using stir bar sorptive extraction (SBSE) with in situ derivatization followed by thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS) analysis. The conditions for derivatization with acetic acid anhydride were investigated. A polydimethylsiloxane (PDMS)-coated stir bar and derivatization reagents were added to 10 ml of water sample and stirring was commenced for 10-180 min at room temperature (25 degrees C) in a headspace vial. Then, the extract was analyzed by TD-GC-MS. The optimum time for SBSE with in situ derivatization was 90 min. The detection limits of 2,4-DCP, BP, OP, NP, PCP and BPA were 2, 1, 0.5, 5, 2 and 2 pg ml(-1), respectively. The method showed good linearity over the concentration ranges of 10, 5, 2, 20, 10 and 10-1000 pg ml(-1) for 2,4-DCP, BP, OP, NP, PCP and BPA, respectively, and the correlation coefficients were higher than 0.99. The average recoveries of those compounds in river water samples were equal to or higher than 93.9% (R.S.D. <7.2%) with correction using the added surrogate standards. This simple, accurate, sensitive and selective method can be used in the determination of trace amounts of phenolic xenoestrogens in river water samples. 相似文献
8.
Dipl.‐Ing. Birgit Wilding Dr. Margit Winkler Dr. Barbara Petschacher Dr. Regina Kratzer Dr. Sigrid Egger Dr. Georg Steinkellner Dr. Andrzej Lyskowski Prof. Bernd Nidetzky Prof. Karl Gruber Prof. Norbert Klempier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7007-7012
Nitrile reductase QueF catalyzes the reduction of 2‐amino‐5‐cyanopyrrolo[2,3‐d]pyrimidin‐4‐one (preQ0) to 2‐amino‐5‐aminomethylpyrrolo[2,3‐d]pyrimidin‐4‐one (preQ1) in the biosynthetic pathway of the hypermodified nucleoside queuosine. It is the only enzyme known to catalyze a reduction of a nitrile to its corresponding primary amine and could therefore expand the toolbox of biocatalytic reactions of nitriles. To evaluate this new oxidoreductase for application in biocatalytic reactions, investigation of its substrate scope is prerequisite. We report here an investigation of the active site binding properties and the substrate scope of nitrile reductase QueF from Escherichia coli. Screenings with simple nitrile structures revealed high substrate specificity. Consequently, binding interactions of the substrate to the active site were identified based on a new homology model of E. coli QueF and modeled complex structures of the natural and non‐natural substrates. Various structural analogues of the natural substrate preQ0 were synthesized and screened with wild‐type QueF from E. coli and several active site mutants. Two amino acid residues Cys190 and Asp197 were shown to play an essential role in the catalytic mechanism. Three non‐natural substrates were identified and compared to the natural substrate regarding their specific activities by using wild‐type and mutant nitrile reductase. 相似文献
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We have studied the potential degradation of poly(lactic acid)-based fabrics treated with commercial softeners and stored under two sets of conditions for one year. Initial wet-processing caused a fall in molecular weight of about 28%, irrespective of after-treatment. Storage at 40 °C and 80% RH produced further degradation which, with few exceptions, was aggravated by the presence of softeners. Ultimately, all samples degraded beyond the point of commercial usefulness. No clear distinction could be made between the effects of softeners having differing compositions. In contrast, fabrics stored under milder conditions of 23 °C and 50% RH showed no significant time-dependent polymer degradation, irrespective of the treatment applied. There were slight changes in tensile properties and some evidence of physical structural effects having occurred, which we attribute to physical aging. However, we do not believe these to be so serious as to call into question the long-term viability of PLA-based textile products. 相似文献