共查询到20条相似文献,搜索用时 15 毫秒
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通过对碘元素概念发展历程的考证可知,1813年,盖·吕萨克首次提出碘元素概念,但当时碘元素和碘单质概念界定不清。至道尔顿提出原子论,赋予碘元素新的含义,首次将碘原子和碘元素结合在一起。20世纪40年代,碘同位素的发现完善了碘元素概念,形成现代碘元素观念。在化学教育中,须让学生认识到碘元素概念的发展史不仅是元素概念的发展史,也是科学思想的演进史和科学方法的发展史。 相似文献
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在古代哲学中,水被视为一种物质本原.17世纪化学学科形成后,水被定义成一种化学元素.18世纪的化学革命中,水被发现是氢氧化合物.19世纪原子-分子论的创立,使水的概念得到微观表征.至20世纪,重水的发现和干水的发明使水的概念有了新的发展.总之,水的概念的发展史,反映了化学思想的发展和科学技术的进步,对化学研究和化学教育... 相似文献
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Raymond R. Myers 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):1133-1149
Dating from prehistory and Cro-Magnon man, coatings developed slowly from artistry to technology. Decorative values prevailed well past the Renaissance; the protective function of coatings emerged after the Industrial Revolution. Research in film-formers which converted coatings into a high-technology industry is summarized, and the stimulation provided by the need for coatings to comply with regulations is discussed. 相似文献
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通过对钾元素概念的发展史考证分析可知,钾是电化学兴起后最先发现的活泼金属。19世纪初,随着科学思想和实验条件的发展,通过电解法首次制取到钾的单质,但并未确定为元素。19世纪中期,对钾元素性质的实验验证和原子论的发展,使得钾元素的概念被确认。20世纪20年代,钾元素同位素的发现,形成了现代的钾元素概念。钾元素概念的发展史不仅是元素概念的发展史,也是科学方法的发展史与科学思想的演变史。 相似文献
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18世纪,发现氢气的卡文迪什认为该气体是水与燃素的化合物;但发现水的组成的拉瓦锡认为氢气是一种元素物质.到19世纪,原子分子论形成后,氢气被认为是由双原子分子构成的单质.20世纪30年代,氢同位素的发现使人们对氢元素概念有了新认识,并逐渐形成现代氢元素概念.氢元素概念的发展史不仅是元素概念的发展史,也是科学思想的演进史... 相似文献
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Scientific theory innovation needs scientists who have comprehensive critical thinking. Taking the history of science of phlogiston and periodic law of elements as an example, this paper expounds the role of the critical thinking skills and habits, and tries to develop the way for acquisition of critical thinking from the history of science. 相似文献
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沿循化学键发展史、创设实验和文献情境、分析实验数据,引导学生自主建构化学键的概念及其表征方式。研究结果表明:基于化学史和实验数据的教学不仅能帮助学生充分理解概念的含义,在学生构建概念并解释真实问题的过程中,还能发展学生宏微结合、证据推理、科学探究与社会责任的化学学科核心素养,认识化学研究的创新方法和研究结论的相对合理性。 相似文献
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A concept of a stereochemical system is presented based on a notion of chiral, achiral sets andon the fundamental triad of streochemistry: conformation, chirality, configuration. The interpretation of themathematical essence of the latter is performed by application of Ruch, Noether, and Goedel theorems. 相似文献
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Muhammad Modassar A. N. Ranjha Rabia Kanwal Bakhtawar Shafique Rai Naveed Arshad Shafeeqa Irfan Marek Kieliszek Przemysaw ukasz Kowalczewski Muhammad Irfan Muhammad Zubair Khalid Ume Roobab Rana Muhammad Aadil 《Molecules (Basel, Switzerland)》2021,26(16)
Different parts of a plant (seeds, fruits, flower, leaves, stem, and roots) contain numerous biologically active compounds called “phytoconstituents” that consist of phenolics, minerals, amino acids, and vitamins. The conventional techniques applied to extract these phytoconstituents have several drawbacks including poor performance, low yields, more solvent use, long processing time, and thermally degrading by-products. In contrast, modern and advanced extraction nonthermal technologies such as pulsed electric field (PEF) assist in easier and efficient identification, characterization, and analysis of bioactive ingredients. Other advantages of PEF include cost-efficacy, less time, and solvent consumption with improved yields. This review covers the applications of PEF to obtain bioactive components, essential oils, proteins, pectin, and other important materials from various parts of the plant. Numerous studies compiled in the current evaluation concluded PEF as the best solution to extract phytoconstituents used in the food and pharmaceutical industries. PEF-assisted extraction leads to a higher yield, utilizes less solvents and energy, and it saves a lot of time compared to traditional extraction methods. PEF extraction design should be safe and efficient enough to prevent the degradation of phytoconstituents and oils. 相似文献
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Geir Bjrklund Mariia Shanaida Roman Lysiuk Halyna Antonyak Ivan Klishch Volodymyr Shanaida Massimiliano Peana 《Molecules (Basel, Switzerland)》2022,27(19)
Aging is characterized by an imbalance between damage inflicted by reactive oxygen species (ROS) and the antioxidative defenses of the organism. As a significant nutritional factor, the trace element selenium (Se) may remodel gradual and spontaneous physiological changes caused by oxidative stress, potentially leading to disease prevention and healthy aging. Se is involved in improving antioxidant defense, immune functions, and metabolic homeostasis. An inadequate Se status may reduce human life expectancy by accelerating the aging process or increasing vulnerability to various disorders, including immunity dysfunction, and cancer risk. This review highlights the available studies on the effective role of Se in aging mechanisms and shows the potential clinical implications related to its consumption. The main sources of organic Se and the advantages of its nanoformulations were also discussed. 相似文献
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Prashant Gupta Bhagwan Toksha Mostafizur Rahaman 《Chemical record (New York, N.Y.)》2024,24(1):e202300295
The research in energy storage and conversion is playing a critical role in energy policy as the innovation and technological progress are essential for achieving the energy transition and climate neutrality goals. Hydrogen Fuel Cell technology is considered a strategic element in the pursuit of sustainable and clean energy solutions. This technology is increasingly gaining attention in recent years as a potential substitute to conventional non-renewable energy sources. Fuel cell technology can be employed for domestic/commercial use along with powering the transportation sector which currently employs the use of conventional battery systems. However, these systems pose severe limitations with respect to longer charging times and limited distance range. This review article aims at providing a comprehensive methodical overview of hydrogen-based fuel cell technology along with key concepts, present day scenarios, including overview of the market and industry trends, government policies and initiatives, along with major stakeholders involved in scaling up the technology for mass consumption. The outlook of fuel cells, including their capability to revolutionise the energy sector is discussed. The technological advancements and breakthroughs on the horizon along with the challenges and safety concerns related to the widespread acceptance of fuel cells are analysed. 相似文献
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Abstract A model for anisotropic phases in a random side-chain nematic copolymer is proposed and solved in the mean-field approximation. The main results of the calculation are the appearance of paranematic and nematic phases and a critical point, without the application of external electric or magnetic fields. 相似文献
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A model for anisotropic phases in a random side-chain nematic copolymer is proposed and solved in the mean-field approximation. The main results of the calculation are the appearance of paranematic and nematic phases and a critical point, without the application of external electric or magnetic fields. 相似文献
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《Fluid Phase Equilibria》2004,220(1):7-9
In a van der Waals model for a non-wetting confined fluid in a nanopore a shift in the critical temperature, with respect to the bulk value, is predicted. The agreement with experiment is good, giving that the characterization of fluids is done only by the Lennard–Jones potential parameters. The theory gives also a similar shift in the critical pressure. 相似文献