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1.
钠离子在人体生理与病理上起着关键性的作用,特别是在神经传导、肌肉与心脏收缩、电解质平衡、阳离子运输和细胞容积等方面都发挥着至关重要的功能。因此,开发用于细胞中钠离子三维动态成像的双光子荧光探针显得尤为重要。以苯并15-冠-5和双氰基二苯代乙烯分别作为钠离子受体与双光子荧光团开发出探针DNa,对DNa的结构进行了表征鉴定。探针DNa具有诸如小的分子尺寸、大的双光子吸收截面(δTPA, 1054 GM)、极好的光稳定性、适宜的水溶性和优良的细胞渗透性等优点. DNa对Na 显示了优良的专一选择性,不受其它离子的干扰,对Na 的解离常数Kd = 23 ? 2 mmol?L-1。DNa能用于细胞中Na 的三维成像,是一个性能优良的双光子荧光探针。  相似文献   
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The compact, robust nature of the CMOS solid-state photomultiplier (SSPM) allows the creation of small, low-power scintillation-based radiation measurement devices. Monitoring space radiation including solar protons and secondary neutrons generated from high-energy protons impinging on spacecraft is required to determine the dose to astronauts. Small size and highly integrated design are desired to minimize consumption of payload resources.RMD is developing prototype radiation measurement and personal dosimeter devices using emerging scintillation materials coupled to CMOS SSPM’s for multiple applications. Spectroscopic measurements of high-energy protons and gamma-rays using tissue-equivalent, inorganic scintillators coupled to SSPM devices demonstrate the ability of an SSPM device to monitor the dose from proton and heavy ion particles, providing real time feedback to astronauts. Measurement of the dose from secondary neutrons introduces additional challenges due to the need to discriminate neutrons from other particle types and to accurately determine their energy deposition. We present strategies for measuring neutron signatures and assessing neutron dose including simulations of relevant environments and detector materials.  相似文献   
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本文通过元素分析,IR谱及MS谱等方法研究了TBP—正十二烷体系中酸性强络合辐解产物的性质和结构。用同位素示踪方法对长链酸性磷酸酯的生成机理进行了探讨并找到了能抑制长链酸性磷酸酯的有效的抑制剂。  相似文献   
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分别以甲氧基作为给电子基团、溴作为吸电子基团,设计并合成了一系列三苯胺基二苯乙烯衍生物.用红外光谱、核磁共振谱及元素分析对其化学结构进行了表征.通过紫外-可见吸收光谱和循环伏安法研究了其能带结构.以三苯胺基二苯乙烯衍生物作为电荷传输层、TiOPc作为光生层,制备了双层光电导体,研究了给/吸电子基团取代对光导性能的影响.  相似文献   
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The highly efficient process of cis to trans isomerization of stilbene photocatalyzed with diphenyldiselenide inn-hexane solution with quantum yield up to 3500 has been studied. The rate constant of stilbene isomerization catalyzed with PhSe radical, the quantum yield of diphenyldiselenide dissociation and the rate constant of PhSe radicals recombination have been obtained in the temperature region from 288 to 323 K. Oxygen has been found to inhibit the isomerization at high stilbene concentration.  相似文献   
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Two novel tetramethyl stilbene-based novolac (II and IV) were synthesized from 2,6-dimethyl phenol and chloroacetaldehyde dimethylacetal or chloroacetone, and then the resulted novolacs were epoxidized to tetramethyl stilbene-based epoxy resins (III and V). The proposed structures were confirmed by FTIR, elemental analysis, mass spectra, NMR spectra and epoxy equivalent weight titration. The synthesized tetramethyl stilbene-based epoxy resins were cured with 4,4-diaminodiphenyl methane (DDM) and 4,4-diaminodiphenyl sulfone (DDS). Thermal properties of cured epoxy resins were studied using dynamic mechanical analyzer, differential scanning calorimeter, thermal expansion analyzer and thermal gravimetric analyzer (TGA). These data were compared with that of the commercial tetramethyl biphenol (TMBP) epoxy system. According to the experimental data, the order of Tg for cured epoxy system is III>TMBP>V. The order of moisture absorption for cured epoxy system is V<III<TMBP. According to TGA, the 5% degradation temperatures in nitrogen atmosphere were in the range 370-377 and 397-412 °C for DDM and DDS curing systems, respectively. In air atmosphere, the 5% degradation temperatures were in the range 372-385 and 410-411 °C for DDM and DDS curing systems, respectively. The CTE is in inverse order with Tg, therefore, III/DDS<TMBP/DDS<V/DDS.  相似文献   
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Five peanut (Arachis hypogaea L.) genotypes with diverse antioxidant capacity were quantitatively profiled for p-coumaric acid, salicylic acid, resveratrol, and daidzein. The co-eluting compounds, caffeic/vanillic acid and ferulic/sinapic acid, were quantified on caffeic acid equivalent and ferulic acid equivalent bases, respectively. The HPLC analysis established significant genotypic differences (P < 0.05) in free and total phytochemical composition and also demonstrated the importance of the bound (e.g., conjugated and matrix-embedded) fraction. Specifically, the study suggested that 77–93% of the p-coumaric acid, 44–53% of the ferulic/sinapic acid, 71–89% of the salicylic acid, 59–68% of the resveratrol, and 89–97% of the daidzein in raw peanut kernels were present in bound forms. D147-p8-6F and Sutherland were sister-lines (derived from the same F2 plant) that had high foliar disease tolerance, high antioxidant capacity, and similar phytochemical profiles, which was consistent with associations between phytoalexin production and genetically determined disease resistance made by previous researchers. Principal components analysis linked high antioxidant capacity with a combination of phytochemicals that were not directly correlated in bivariate analysis (e.g., resveratrol was negatively correlated with caffeic/vanillic and p-coumaric acid) and that were not delineated by genotype.  相似文献   
9.
Direct detection of fast neutrons using organic scintillators is one alternative to moderated thermal neutron detectors deployed to detect fission neutrons—a relevant question in light of dwindling 3He supplies. Recent developments in materials science have demonstrated the capability to grow larger crystals in reasonable times. In light of these developments, this study compares the relative performance of a 3He-based neutron module from a commercially available portal monitor with a theoretical organic scintillator of similar overall size. Stilbene serves as a benchmark with its performance estimated from a combination of energy deposition modeled by radiation transport calculations and an assumption of the lowest neutron energy at which pulse shape discrimination can effectively separate neutron and gamma-ray events. Before intrinsic detection efficiencies on par with moderated detector systems can be achieved, the results point to the need for further advances including significant increases in detector size, especially thickness, and/or lower pulse shape discrimination thresholds.  相似文献   
10.
Grape calli systems were used to study the relationships between stilbene production and: (1) four grape genotypes, (2) leaf, berry exocarp and seed tissues and (3) UV-C irradiation. All explants could be de-differentiated. However, subsequent callus growth depended mainly on genotype and tissue type. Non-embryogenic callus accumulated more resveratrols and piceids and had a higher growth index than pro-embryogenic and embryogenic calli. UV-C irradiation for 20 min was most efficient in promoting both the accumulation of resveratrols and piceids and callus growth index. There was dynamic production of resveratrols and piceids in UV-C-irradiated leaf-derived calli over a 72 h period, with optimum harvest time for the highest total stilbene content at 48 h. Accumulation of stilbenes in UV-C-irradiated calli depended upon genetic background and tissue type, with higher stilbene contents in two interspecific root stocks and leaf or exocarp explants.  相似文献   
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