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生物技术——基因工程、细胞工程、酶工程和发酵工程,正广泛应用于农业领域:动植物良种培育、快速繁殖、动植物保护、固氮基因工程和土壤改善,以及农产品的深层次加工,并取得了明显的经济效益。生物技术是第二次绿色革命的先导技术,其应用于农业的特点和优势是:开发的层次深,应用的领域广,产出的效益高。 相似文献
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J.L Moilliet 《Endeavour》1985,9(3):129-131
James Keir, the 250th anniversary of whose birth falls this year, was very typical of the leading natural philosophers of his day. A member of the well-known Lunar Society of Birmingham he was not only very familiar with the theoretical chemistry of his time — though his reputation suffered because he clung to the phlogiston theory long after it had been exploded by Lavoisier — but was also a successful manufacturing chemist. Additionally he had wide literary interests and was active in the Whig politics of his day and a supporter of Joseph Priestley. 相似文献
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P.N. Thompson 《Endeavour》1978,2(2):93-97
With growing concern for adequate sources of energy in the future there has been a revival of interest in the underground gasification of coal. This article describes current activity in this field and discusses the technological and economic factors involved. It concludes that although this means of utilising coal is only marginally attractive at present, it could yet prove valuable—especially for exploiting very deep coal seams, as in Belgium—in changing economic circumstances. 相似文献
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Hermann Schildknecht 《Endeavour》1984,8(3):113-117
It is a matter of common experience that certain plants react by movement—often surprisingly rapid—to physical stimuli. These movements are the result of turgor changes in the cells concerned and these are triggered by chemical messengers known as turgorins. This article reviews recent developments in this field and shows that these highly active plant hormones have relatively simple structures. 相似文献
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Gilbert Shama 《Endeavour》2019,43(1-2):11-16
Richard Julius Petri’s status as inventor of the culture dish that bears his name has been subject to a number of challenges over the years. Both those bacteriologists who claimed self-recognition for the invention, and those to whom it was attributed by their various advocates were all contemporaries of Petri. The evidence assembled here indicates that no single individual—including Petri—ought to be accorded credit for the inception of that shallow, circular, covered culture dish which, it transpires, is a simultaneous invention made by half a dozen bacteriologists active in the mid-1880s and ultimately owes its emergence to the prevailing bacteriological zeitgeist. 相似文献
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三种数值方法在几种六道木分类中的应用 总被引：1，自引：0，他引：1
In the last 10—20 years there has bee n increasing awareness of the problem con-
cerning the aims and practices of taxonomy. In particular, there has been growing
interest in the development of numerical methods in biological taxonomy as an aid to
making systematics a quantitative science, a step which comes in time to almost every
scientific discipline.
Numerical taxonomy is the evaluation by numerical methods of the affinity or
similarity between taxonomic units and the employment of these affinities in erecting
a hierarchic order of taxa. The present rapid development of these ideas is presuma-
bly a result of the development of computer techniques.
Numerical taxonomic approach has been applied to the studies of entomology and
microbiology in China to some extent since 1975. But so far it hasn’t been commonly
used in botany. The present report is a preliminary study on 9 spp. of the genus
Abelia. A set of binary data with 54 characters is used for computing association
coefficient; and a set of quantitative data with 47 characters for distance coefficient
and correlation coefficient. For the mathematical models were chosen the non-metric
simple matching association coefficient, the geometrical distance of Riemannian space
and correlation coefficient. Computational procedures are stepwise presented in detail
and computer programmes are written in the background of Algol-60 language. Cluster analysis is compared with simple linkage, average linkage and multi-correlation.
The results of DC and CC for 9 spp. of Abelia agree closely with the traditional
taxonomy, because the data we collected mainly come from morphological characters.
It would seem that the results of quantita tive data are more appropriate for seed
plants. It is, therefore, postulated that our programes are complementary and very
useful to a wide range of classification entities, such as microbes, animals and plants
in present situation in China.
In conclusion, a comparison between the conventional taxonomy and numerical
taxonomy has been made, and a brief discussion of three problems, i.e. the monothetic
versus polythetic, divisive versus agglomerative, weighting versus unweighting.
相似文献
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K Simkiss 《Endeavour》1979,3(1):2-6
With the exception of sodium, potassium, and calcium relatively little is known of the cellular control of metal ions. Nevertheless, this is demonstrably very important, because a large number of metals—iron, copper, and manganese, for example—are essential constituents of enzyme systems. Provision must be made, therefore, for them to be stored in anticipation of demand but in a form that neutralises their toxic properties. Equally, mechanisms must exist to eliminate excessive amounts of metal ions. 相似文献
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Bairj Donabedian Associate Professor 《The Information Society》2013,29(3):121-135
In the reconciliation of rational-choice and social-influence approaches to media choice offered here, the choice process is decomposed into two subprocesses. In the first subprocess—that of rational choice—decisional ambiguity frustrates complete optimization. Optimization is partial, yielding a set of effectively interchangeable media alternatives over which the user is indecisive. In the second subprocess—that of social influence—imitation, deference, and other cues act on the set of interchangeables, yielding a single ultimate choice. If in the social-influence subprocess there are benefits to coordinating with others, group choice crystallizes around a single media alternative. If these benefits are absent, individual choice remains idiosyncratic, with each decision maker making random choices within the set of interchangeables. In organizational life, media choice transpires sequentially, with each choice conditioning a succeeding one. In its dynamic form, the present model explicitly incorporates such sequential environments: The twofold choice process transpires iteratively within individual decision sites (in the multiple purchasing decisions of a committee, for example) and sequentially across decision sites (from committee to individual, for example). The model generates considerable empirical implications. As decisional ambiguity grows, the rational-choice component of the choice process shrinks, implying upper-bound conditions for the explanatory power of rational-choice statistical models. 相似文献
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Harbans Lai Rajesh Pandey S. K. Aggarwal 《Indian journal of clinical biochemistry : IJCB》2000,15(1):158-168
The past two decades have witnessed new facets in vitamin D metabolism. Free vitamin D3 till now considered to be limited to animal sources, has been shown to occur in plants. Further, the extrarenal synthesis of active vitamin D3 or calcitriol has been documented in physiological as well as in certain pathological conditions. At the cellular level, calcitriol acts through a dual mechanism. The genomic pathway involves the vitamin D receptor (VDR) which is of ubiquitous distribution and linked with various diseases. Besides, a nongenomic VDR—independent pathway also exists. The biological effects of calcitriol can no longer be dismissed by merely referring to calcium/bone homeostasis. It enhances the perinatal growth and suppresses the abnormal growth, as well. The effects on the endocrine, immune, cardiovascular, reproductive and nervous systems have also been characterized. It is compelling to believe that calcitriol and/or its analogues will find extensive applications at least in the treatment of osteoporosis, perinatal growth retardation, neoplasia, psoriasis, insulin resistance and transplantation. 相似文献
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本研究通过1980—2005年颁布的287项政策及2006—2008年间为了实施《国家中长期科学和技术发展规划纲要(2006—2020年)》(简称"中长期规划")制定的79项促进自主创新政策主体结构的分析,阐明在不同的战略情景下中国创新政策主体合作结构的演进过程.研究结果表明:随着创新战略的转变,中国创新政策主体正逐渐脱离单一机构制订模式,多机构合作出台政策的数量在显著增加,创新政策出台更具有系统性和一致性,组织机构之间的协调性增强. 相似文献
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Jean J Fried 《Endeavour》1985,9(3):112-116
Because it is generally freely and plentifully available in temperate regions the importance of water tends to be under-rated. In reality, it is fundamental to the economic strength of all countries and ensuring adequate supplies in face of growing needs is of paramount importance. A comprehensive review of the water resources of the European Community reveals that while there are many regional differences — especially in the degree of dependence on ground, as opposed to surface, water — overall supplies are adequate, but only if very carefully managed. 相似文献
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为提升台湾科技产业,争取高科技及精密工业投资,因而位于台湾台南沿海过去为传统引海水制盐的基地被规划成为科技工业区,希望藉由便捷之交通网及整体景观设计,开创南台湾工业区之新形象.基地原为南部重要之制盐场区,引进海水之渠道沿岸着生茂密之红树林植物,除保护坡岸外,更孕育多样化之河口生态体系;现虽因制盐工业式微,然既有滩地仍有大量水鸟聚集,开发单位希望复育当地堤岸既有之榄李及五梨跤等红树林植物,塑造地方特色,并达成开发与保护生物多样性之双赢目的.红树林生育于河海交会之感朝河段,环境较为特殊,因而适生植物之器官、生理及繁殖均经演化以适应环境特质,因此红树林育苗及栽植工作需考量生存之环境特质为,有别于一般绿化工程,本研究控制灌溉方式,调节感潮水位及水份盐度,以达理想之复育存活率.现有基地基础盐化情况严重,为避免盐分随水分回渗至土壤层,因而复育区栽植基础以及回填土均加以处理,并定时监测土壤盐度,以确保栽植成功.复育工程自育苗、栽种、抚育历时五年,景观亦由灰白之盐山盐田改变为绿意盎然之红树林绿带,除提高土地利用之加值作用外,亦达成建设农渔业生态环境优美化及生态环境保育之双重目的. 相似文献
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This research has investigated the feasibility of using a distance measure, called the Bayesian distance, for automatic sequential document classification. It has been shown that by observing the variation of this distance measure as keywords are extracted sequentially from a document, the occurrence of noisy keywords may be detected. This property of the distance measure has been utilized to design a sequential classification algorithm which works in two phases. In the first phase keywords extracted from a document are partitioned into two groups—the good keyword group and the noisy keyword group. In the second phase these two groups of keywords are analyzed separately to assign primary and secondary classes to a document. The algorithm has been applied to several data bases of documents and very encouraging results have been obtained. 相似文献
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社会呼吁、专家呐喊,为了给孩子＂减负＂绞尽了脑汁,可是效果不佳,甚至有愈减愈重的趋势。真正要减负,学校要做什么？学校校长要做什么？本文从三个方面谈谈小学生＂减负＂校长应该做些什么？校长要明确小学生＂减负＂的重要意义;加强教师队伍建设,为＂减负＂奠定基础;强化课程意识,规范＂减负＂行为。 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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《教育概论》作为建构教育专业学生基础框架的必读书是非常有必要的,叶澜教授对于教育定义、教育要素、教育与社会与人发展之间的关系均有自己独特的、客观的见解。该书通过总-分-总的整体结构,深刻阐释了客观实在的＂教育＂定义、教育具体的主客体关系和教育两大功能的关系,为读者提供了一幅教育学基础框架的严谨图谱。 相似文献
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Pyungho Kim 《The Information Society》2013,29(1):41-44
The spectacular growth of the Internet in Korea has propelled her to the very top of the international rankings based on technology peneration statistics. The resulting international attention and national pride have fostered the notion of “Korea—a strong Internet nation.” The ready embrace of this idea by officials and the public at large has made a critical evaluation almost an anathema. This article reviews the published critiques, which have been rare and scattered, and opens up the “what next” question for an unbounded discussion. 相似文献