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1.
新技术、新材料、新产业的蓬勃发展将对关键金属矿产需求产生深远影响,探讨技术进步如何影响关键金属矿产需求,从而确保关键金属矿产安全,对中国经济迈上高质量发展阶段和实现低碳转型具有一定现实意义。本文对技术进步与关键金属需求关系的文献展开了系统梳理,发现：随着资源安全成为国家重要需求问题,技术进步与关键金属需求预测研究逐渐成为热点,但现有文献量化研究较少且缺乏系统性,鉴于技术进步测度和数据获取等难点,需求预测结果的精准性有待进一步提高。本文提炼了技术进步作用于关键金属需求的3条微观影响机制,即技术进步—经济增长—关键金属、技术进步—产业结构—关键金属、技术进步—替代循环—关键金属,为后续研究提供整体分析框架;提出该领域后续研究重点,即重点关注低碳技术-关键金属、战略新兴产业-关键金属耦合问题,同时解决技术进步在理论模型和计量模型中的测度问题,推进新技术革命背景下关键金属需求预测分析框架的构建。 相似文献
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Heavy metal ions released into various water systems have a severe impact on the environment and human beings, and excess exposure to toxic metal ions through drinking water poses high risks to human health and causes life-threatening diseases. Thus, there is high demand for the development of a rapid, low-cost, and sensitive method for detection of metal ions in water. We present a portable analytical system for colorimetric detection of lead (Pb2+) and aluminum (Al3+) ions in water based on gold nanoparticle probes and lab-on-a-chip instrumentation. The colorimetric detection of metal ions is conducted via single-step assays with low limits of detection (LODs) and high selectivity. We design a custom-made microwell plate and a handheld colorimetric reader for implementing the assays and quantifying the signal readout. The calibration experiments demonstrate that this portable system provides LODs of 30 ppb for Pb2+ and 89 ppb for Al3+, both comparable to bench-top analytical spectrometers. It promises an effective platform for metal ion analysis in a more economical and convenient way, which is particularly useful for water quality monitoring in field and resource-poor settings. 相似文献
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科技资源配置的新问题和对策分析 总被引：11，自引：1，他引：10
国家科技资源配置存在急点、难点、热点、疼点,创新成效差,统筹乏力,资金投入不足,存在科技体制障碍。科技资金投入要建立制度保障,国家财政科技经费拨款占国家财政总支出的比例要达到5.5%左右,要建立对企业R&D投入冲抵所得税的税收制度。国家创新体系建设要有统筹管理部门,国家科技计划要统筹管理,突出重点,釆用基金制度管理国家科技计划,政府职能部门应从项目的直接管理中解放出来。 相似文献
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各门课程教学模式的存在是必然的构思提出,初中思想品德课也不例外,而问题在于要如何创新教学模式。本文提出的是分、合、勾连有思想品德课创新教学模式。 相似文献
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要培养中职学生的创新精神和实践能力,就必须转变中职英语教学观念,充分发挥学生的主体地位。在教师的引导下,让学生自己去发现问题、研究问题、探求知识。培养学生创新能力可分为＂五步骤＂,即＂打基础＂——＂走新路＂——＂梳通道＂——＂攀高峰＂——＂拓阵地＂循序渐进的五个环节。其中＂打基础＂是前提,＂梳通道＂是关键。 相似文献
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应用人口流动理论和经济增长理论,分析了西部地区的多数小城镇由于存在机制缺陷———缺乏增长点,所以,与城市相比较并不具有聚集人口的拉力优势。因此,西部地区的小城镇建设必须因地制宜,合理定位。 相似文献
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Jiongzhao Li Weicheng Cao Yufei Shu Haibing Zhang Xudong Qian Xueqian Kong Linjun Wang Xiaogang Peng 《国家科学评论(英文版)》2022,9(2)
High-quality colloidal nanocrystals are commonly synthesized in hydrocarbon solvents with alkanoates as the most common organic ligand. Water molecules with an approximately equal number of surface alkanoate ligands are identified at the inorganic–organic interface for all types of colloidal nanocrystals studied, and investigated quantitatively using CdSe nanocrystals as the model system. Carboxylate ligands are coordinated to the surface metal ions and the first monolayer of water molecules is found to bond to the carboxylate groups of alkanoate ligands through hydrogen bonds. Additional monolayer(s) of water molecules can further be adsorbed through hydrogen bonds to the first monolayer of water molecules. The nearly ideal environment for hydrogen bonding at the inorganic–organic interface of alkanoate-coated nanocrystals helps to rapidly and stably enrich the interface-bonded water molecules, most of which are difficult to remove through vacuum treatment, thermal annealing and chemical drying. The water-enriched structure of the inorganic–organic interface of high-quality colloidal nanocrystals must be taken into account in order to understand the synthesis, processing and properties of these novel materials. 相似文献
9.
Anita McConnell 《Endeavour》1983,7(1):25-30
Oceanography is necessarily a three-dimensional science, for the open surface of the sea conceals tremendous variations in depth and marked differences in temperature, salinity, and water movement, all of which are critical for marine life. Today the major research programmes study the oceans in four dimensions, since changes with time—daily, seasonal, and year-to-year—are no less important than those in space. Oceanography and meteorology have much in common: the temperature and movement of air and water cannot be directly seen from the ground or sea level, but must be investigated by means of specialised instruments whose readings can be brought back to the observer. 相似文献
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近几年的高考作文是考后人们热议的话题,然而当冷静下来去认真分析,不难发现高分甚至满分作文多为议论类文章。究其原因,大致可以归为三点：议论类文章庞大的内容体系;议论角度的独特性;论点引人思考的幽深性。那么,在这里我提出一点大胆的想法——把考场作文＂交给＂议论文。从学生的角度考虑,写好议论文首先要认清议论文的丰富性,其次要积淀议论文的厚度。 相似文献
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本文分析提出了"现代信息人"的概念及其特征,明确了现代信息人"主动学习,善于交流;自我超越,健康向上;自主开放,融合共生;系统思维,切实行动;挑战极限,全面发展"的一般标准及其内涵,在此基础上,探讨了争做现代信息人必须"修炼志气、修炼大气、修炼正气、修炼朝气、修炼才气、修炼灵气"的实践路径和具体要求。 相似文献
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The present-day guidlines for thesaurus design recommend the two different strategies—the committee and empirical approaches—for identifying candidate terms. An argument is made that the basis for the recommendation is the assumption that the knowledge based on the consensus of experts of a field is different from the knowledge expressed in the literature of that field. An experiment was conducted to test the validity of this assumption. The finding that the two strategies failed to generate the two significantly different lists of terms challenges the validity of the assumption and raises several important questions to the theorists who write the guidelines for thesaurus design and to those who must put the guidelines into practice for design of a thesaurus. 相似文献
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John Zeleny 《Journal of The Franklin Institute》1932,214(5):513-532
A criticism by Loeb and Bradbury of my interpretation of the experimental results of that part of a previous paper which dealt with the aging of negative ions in commercial nitrogen is shown to be invalidated by a mistake in their analysis and by assumptions which do not represent facts with sufficient accuracy. A more extended analysis of the previous work and new evidence which is given confirm the correctness of the former contention that the negative ions in question changed in size with age. The lateral spread, owing to diffusion, of a stream of electrons in this nitrogen at atmospheric pressure, when moving in an electric field of about 100 volts/cm., was found to be very nearly the same as that for positive ions under like conditions. The average energy losses of the electrons at collision with the molecules must therefore have nearly balanced the gains from the electric field and hence were greater than would result from purely elastic collisions. The experimental results indicate that in fields down to at least 20 volts/cm. nearly all of the attachment of electrons to molecules in the gas used occurred close to the place of their liberation. 相似文献
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报道了酸性过氧化氢在一些金属离子存在时与碱溶液发生的化学发光反应.对影响化学发光的因素以及金属离子的作用进行了试验和讨论. 相似文献
16.
Effect of magnesium ions on the binding of bilirubin to erythrocytes of different mammalian species, namely, human, buffalo,
goat and sheep was studied. Increase in the concentration of magnesium ions led to a gradual increase in the erythrocyte-bound
bilirubin in both human and buffalo erythrocytes whereas in sheep and goat erythrocytes, the pronounced increase was found
beyond 2.0 and 2.7 mM MgCl2 concentrations respectively. Percentage increase in erythrocyte-bound bilirubin was found highest in human erythrocytes followed
by buffalo and sheep erythrocytes and minimum in goat erythrocytes. These differences in the binding of bilirubin to different
mammalian erythrocytes can be attributed to the differential shielding effect of metal ions which involves the masking of
negatively charged phosphate of phospholipids found on the erythrocyte surface. 相似文献
17.
Erik P. Bucy 《The Information Society》2013,29(5):373-383
Interactivity has been identified as a core concept of new media, yet despite nearly three decades of study and analysis, we scarcely know what interactivity is, let alone what it does, and have scant insight into the conditions in which interactive processes are likely to be consequential for members of a social system. This article attempts to address this deficiency by critiquing three self-defeating tendencies and an erroneous assumption of interactivity research, then proposes four basic propositions around which systematic knowledge regarding interactivity in society may be built. In the spirit of bridging mass and interpersonal processes, a model of interactivity is proposed to initiate discussion about the concept as a cross-level and multivalent phenomenon—one with both positive and negative consequences—and to spur more socially relevant research. For interactivity to succeed as a concept, it must have some meaningful social and psychological relevance beyond its technical status as a property of media systems or message exchanges. 相似文献
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作为一个重要的教学手段,语法翻译法在外语教学中发挥了不可否认的积极作用。它的运用不仅由主观因素——教师的积极的态度所决定,也由客观因素——学校教科书大纲和考试大纲要求来决定。有人认为,语法翻译法必须满足教学和学习的过程,只有在这样的情况下,我们才可以正确地处理语义、词汇、句法和修辞的问题,并最终用这种方法提高语言学习者的能力。 相似文献
19.
《Research Policy》2023,52(7):104791
This paper introduces a newly digitized, open-access version of the Food and Drug Administration’s “Orange Book”—a linkage between approved small-molecule drugs and the patents that protect them. The Orange Book also reports any applicable regulatory exclusivity that prevents competitive entry. We summarize the Orange Book’s coverage and discuss the opportunities and challenges associated with using these data for research. Empirical validations against various administrative datasets suggest that Orange Book records are, largely, complete and accurate. We conclude with a specific use case—calculating legal exclusivity periods for drugs—to highlight the types of choices that researchers must make when using this resource. 相似文献
20.
CMC聚合物对重金属离子的吸附性能 总被引：2，自引：0，他引：2
通过正交试验得出制备羧甲基纤维素(CMC)聚合物的最佳工艺条件:丙烯酸(AA)/羧甲基纤维素=10,引发剂(硫酸铵)和交联剂(N,N'-亚甲基双丙烯酰胺)用量分别为单体的0.0014倍和0.0015倍.吸胀平衡后,将CMC聚合物在400~450℃下完全灰化16h,消解并用火焰原子吸收法测定聚合物对Zn2+、Cu2+、Pb2+、Cd2+、Cr2+、Ni2+和Mn2+的吸附性能.结果表明,CMC聚合物对重金属离子具有一定的吸附能力,其吸附量随着溶液pH值和重金属离子质量浓度的增加而增大,当pH为9时达到最大;并且CMC聚合物对Pb2+和Cu2+的吸附量要大于其他金属离子. 相似文献