共查询到20条相似文献，搜索用时 62 毫秒
1.
详细介绍了旋风铣加工大规格螺纹孔的工艺及使用经验，如M105×4—6H，M90×4—6H公制螺纹孔及2-112″-UNC-2B英制螺纹孔的加工方法，同时给出了刀片消耗定额。 相似文献
2.
到目前为止,人们使用的发电装置或能量转换装置都是遵守能量守恒定律的。如图所示,该图由电动机、压杆、道轨、轮子、重物（发电机）构成,当拉力!"作用在轮子心部"时,拉力!"作的功为#$",根据理论力学知识有：滚阻力隅矩!"·%&'·!或!"&'·!(%且!"&)$",'&*,!、%、+的几何关系为!,&,%+-+,,当+远小于%时,!,!,%+。故#$"&)$"·!&!"·!&!·!"(,&!,·'(,%&'+&*+,即拉力!"所作的功转化为重物*的势能了。如果改变拉力点的位置,让拉力!作用在轮子的顶点.处,在!、%、'、+不变的情况下会出现超常现象。如图所示,在距轮子底部/点!处加一压杆… 相似文献
3.
姜春林 《科学学与科学技术管理》2002,23(10):5-8
对上世纪90年代以来我国出版的四部科学计量学著作<科学计量学--指标@模型@应用>、<科学计量研究方法论>、<科学技术指标与评价方法--科技计量学应用>和<科研评价与指标>进行了介绍和评论,在充分肯定我国科学计量学所取得成就的基础上,就制约我国科学计量学研究的若干因素做了简要分析. 相似文献
4.
案头不能没有它 总被引：23，自引：5，他引：18
梁光铁 《中国科技期刊研究》1998,9(1):38-25
从<科学引文索引>(SCI)、<工程索引>(EI)、<科学技术会议录索引>(ISTP)和我国1996年1227种科技期刊取得有关数据,按地区、学科、机构统计了1996年我国科技论文发表数和被国际、国内引用情况. 相似文献
5.
徐道一先生的<周易科学观>一书,据书评者说:“畅论了<周易>和现代自然科学的联系,综合会通了近十年国内外关于<周易>与现代自然科学的关系的各种论著,更提出了自己的独到见解,……可以说是十年来的科学观点研究<周易>的丰富成果的一次总结“.[徐道一1992,序]徐道一先生自己介绍:<周易科学观>的“第三、四、五章用大量、可靠的现代科学资料从天、地、生、数、理、化综合研究等方面来论述<周易>的一些基本概念“.[徐道一1992,前言]他认为:“从根本上看来,<周易>‘尽宇宙之妙,通天人之际‘“.[徐道一1992,2页]他更认为,正确区分东方科学技术的精华和糟粕的问题中,“核心问题之一是对<周易>的评价“.[徐道一1992,239页]…… 相似文献
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简要介绍了<中国植物志>、<中国动物志>和<中国孢子植物志>三部生物物种巨著的主要内容,其对于生物学、生物分类学和可持续性发展研究的重要价值,对于生物资源利用和保护的重要意义以及编研过程中取得的突破性成果. 相似文献
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王亚平 《内蒙古科技与经济》2011,(21):93-94
总结了识别U盘优劣的几种方法;使用U盘锁定计算机,以保证计算机系统安全;彻底查杀常见U盘病毒及借助软件对U盘文件进行加密等方法技巧。 相似文献
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近年来,英国图标书局(IconBooks)出版了一套系列丛书“后现代遭遇“(Postmodern Encounters).这套丛书中的每一册都以一位思想家的某个重要思想为主线,结合当代世界的一个特定文化现象,介绍和探讨所谓的“后现代社会“的特征.该丛书已经出版的分册有20余种,其中包括<乔姆斯基与全球化>、<道金斯与自私基因>、<德里达与历史的终结>、<海德格与纳粹>、<柏拉图与互联网>、<维特根斯坦与心理分析>等.该丛书宣称,它的每一本小册子“讨论一个处在当代思想的风尖浪口上的观念“,整套书是“塑造21世纪的大争论的小导引“.…… 相似文献
11.
瑞典皇家科学院2007年10月9日宣布，将2007年度诺贝尔物理学奖授予法国国家科学研究中心的阿尔贝·费尔和德国于利希研究中心的彼得·格林贝格尔，以表彰他们在19年前各自独立发现了巨磁电阻效应，为现代信息技术，特别是为人们今天能使用小型化、大容量的硬盘以及在各种磁性传感器和电子学新领域的发展中所作出的奠基性贡献。 相似文献
12.
马毓泉 《中国科学院研究生院学报》1951,1(1):5-19
Gentiana was originally proposed by Tournefort in 1700. Linnaeus adopted this generic name in his “Genera Plantarum” published in 1737. He divided the genus into seven groups on the basis of different shapes of corolla and forms of floral appendages. In his “Species Plantarum” he reorganized them into three artificial ones. Forty years later, Moench established a new genus, Gentianella under which he described G. tetrandra as the type of his new genus. In the view of identity of Gentianella tetrandra with Gentiana campestris L., it is evident that Gentianella represents only some plants formerly included in Gentiana at Linnaeus time. In 1796, Froelich’s monograph on Gentiana appeared. In his work four sections were represented and one of them was Crossopetalum. In 1845, Grisebach also published a monograph of Gentianaceae and recorded fifteen sections of which Amarella and Imaicola are two of his seven proposed ones. In 1888, Huxley studied the floral structure of Gentianaceae in relation with pollination mechanism and, accordingly, divided the family into two main groups, one with epipetalous glands, the other with glands at the base of the ovary. In each group, four types of flowers were found. He concluded that Gentiana was a complex genus on account of presence of four different types of flowers in this group, and suggested that many species of the genus should be separated out to form some smaller generic categories. Six years after, Kusnezow in his monograph divided Gentiana into two subgenera Eugentiana and Gentianella. In his system, subgenus Eugentiana consists of ten sections and the Gentianella, seven. He contributed much to the systematic treatment of Eugnetiana but little to that of Gentianella. He maintained the genus Gentiana in a broad sense. With increased knowledge of this group in the last thirty years, a number of botanists were able to make a clearer delimitation of true Gentiana and its allies and treated them in more natural way. Moench’s genus Gentianella was rerised. In 1936, H. Smith separated Megacodon from Gentianella as a genus. In the present paper, the writer suggests a generic name Gentianopsis for the section Crossopetalum in the same Genus.
This new genus is characterized by (1) its large and somewhat flattened ellipsoidal flower bud, (2) two dissimilar pairs of calyx lobes which are distichously imbricate in aestivation, (3) four triangular, ciflated intracalyx membranes at the base of and alternate with the calyx lobes, (4) distinct gynophore and (5) enlarged stigma. While in typical Gentianella represented by section Amarella, the flower buds are small and terete, a laciniate corona is usually present, and the calyx-lobes are leafy, lanceolate, imbricate, and not provided with intracalyx membrane.
Besides the morphological characters mentioned above, the anatomical structure of
the floral parts is also a significant generic criterion. In Gentianopsis, eight vascular
bundles are present in calyx, representing four dorsals and four fused ventrals. In each
corolla-lobe there are five bundles. In the body of ovary six bundles are present. The
ovule bearing surface is extensive covering nearly to entire surface of the ovary wall with
the exception of a narrow longitudinal zone along the dorsal bundle. In Gentianella,
calyx bundles are three in each lobe, without fusion of the ventrals. In each corolla-
lobe, the bundles are three instead of five as in Gentianopsis but the lateral ones branch
once dichotomously after entering the base of corolla. In the body of ovary only four
main bundles are present due to the fusion of smaller ventral ones. The placentation
is confined to the region of the ventral bundles.
Phylogenetically Gentianopsis and Gentianella may be regarded as closely reIated
and may represent branches of a common line with Gentianopsis standing at a lower
level, Gentianella being more advanced. In Gentianella the number of bundles in the
corolla segments and ovary wall are reduced by partial or complete fusion and the
distribution of ovules is confined only to the region of the ventral bundles. However,
in the calyx of Gentianopsis there is fusion of ventral bundles, whereas the correspound-
ing bundles in the Gentianella remain separate. The Gentianopsis-Gentianella line on
the one hand and the Gentiana line on the other may come again from a common
acestral stock. Gentiana possesses only three bundles in each corolla-lobe. A variety
of plicate between corolla lobes except in case of Gentiana lutea and intracalyx membrane
above the throat of calyx-tube are also the common structures in Gentiana. Thus the
pollination mechanism is highly specialized in the genus. As far as we know, in
Gentiana the glandular appendages usually exist at the base of ovary. If those nectarial
processes are correctly interpreted as the representatives of staminodes, gentiana would,
undoubtedly, be derived from an ancestral form with hypogynous diplostemonous
androecium, and bears no direct relationship to Gentianopsis or Gentianella in which the
glands are epipetalous. It may be reasonable to conclude the Gentiana and Gentianopsis-
Gentianella line are two parallel derivatives from a common ancestor which has the
floral characters of two series of hypogynous stamens. Gentianopsis and Gentianella may
represent branches of a common line with Gentianopsis standing at a lower level,
Gentianella being more advanced. Their relations may be diagrammed below:
Gentianopsis
Gentianella
Common ancestor
Gentiana
This new genus consists of fourteen species and two varieties in the world. Onlyeight species and two varieties are represented in China. They are G. barbara, G. barbatavar. sinensis, G. grandis, G. scabromanginata, G. paludosa, G. nana, G. longistyla,G. lutea, G. contorta, and G. contorta var. Wui. The species of present genus occur in the alpine regions of North Hemisphere. InChina t,hey are distributed in Kokonor, Kansu, Shensi, Shansi, Chahar, Hopei, Manchuria,Hupeh, Szechuan, Sikang, Tibet, and Yunnan. G. Yabei (Takeda et Hara) is foundin Japan, G. detonsa (Bott&) in North Europe, G. ciliata (Linn.) in South Europe,G. crinita (Froel.) G. procera (Holm.) and G. degans (A. Nels) in North America.G. barbata is the most widespreading species and reported in Sibiria and China.G. contorta (Royle) is a common plant in Himalayan mountaineous range, China andNorth part of India. The species and varieties cited in this paper are as follows:
t. Gentianopsis barbata (Froel.) comb. nov.
la. Gentianopsis barbata (Froel.) var. sinensis, var. nov.
2. Gentian opsis grandis (H. Sm.) comb. nov.
3. Gentianopsis scabromarginata (H. Sm.) comb. nov.
4. Gcntianopsis paludosa (Munro) comb. nov.
5. Gentianopsis nana sp. nov.
6. Gentianopsis longistyla, sp. nov.
7. Gentianopsis lutea, sp. nov. 相似文献
13.
自1989年至1992年对江西省九连山自然保护区的天然常绿阔叶林通过凋落物归还到枯枝落叶层的养分量进行了测定.凋落物的干重约为6.4t/hm2·a～8.8t/hm2·a,其中叶凋落物约为4.3t/hm2·a～4.7t/hm2·a.养分归还量氮、磷、钾、钠、钙和镁各为68kg/hm2·a～85kg/hm2·a,3.1kg/hm2·a～3.8kg/hm2·a,21kg/hm2·a～67kg/hm2·a,4.4kg/hm2·a～6.8kg/hm2·a,113kg/hm2·a～160kg/hm2·a和19kg/hm2·a～28kg/hm2·a.氮和磷的归还量小于而钙的归还量大于热带雨林. 相似文献
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中国近代科技奖励制度建立的曲折历程--专利性质的奖励制度 总被引：1，自引：0，他引：1
从洪仁玕<资政新篇>、百日维新<振兴工艺给奖章程程到的<暂行工艺品奖励章程>,在近代中国特殊的社会背景下,分析科技奖励制度在近代中国的引进与生长,并分析了这种政府设立奖励和主要以授予专利的奖励方式产生的原因. 相似文献
17.
赵延花 《内蒙古科技与经济》2005,(Z1):183-185
杨景贤是元末明初蒙古族戏曲家,他传世的作品主要有杂剧<西游记>、<刘行首>和八支散曲.关于他的作品,<录鬼簿>给予了很高的评价,认为是"出人头地",本文主要论其散曲,虽数量不多,但笔者认为这些作品在思想内容与艺术上与当时散曲名家相比亦不惶多让. 相似文献
18.
《中国科学院院刊》2014,29(6)
全球能源变革呼唤能源经济学创新 （何建坤,清华大学）
能源-环境-经济综合评估模型的发展趋势 （范英 朱磊,中国科学院科技政策与管理科学研究所）
大数据时代的能源金融 （郭剑锋 姬强,中国科学院科技政策与管理科学研究所）
应对能源和气候变化挑战： 政策导向型研究 （王 毅,中国科学院科技政策与管理科学研究所）
构建开放的国际原油交易平台 完善有效的能源市场体系 （褚玦海,上海期货交易所/上海国际能源交易中心）
非常规油气开发在美国的兴起对全球油气市场的影响 （乌米·伊力达尔,美国路易斯安那州立大学能源研究中心、尼日利亚哈科特港大学绿色能源研究所）
能源、市场和市场失灵 （阿多尼斯·雅筑,加拿大多伦多大学经济系） 相似文献
19.
杨更 《科技成果管理与研究》2006,(4):61-63
当前,我国正面临着"十一五"建设的重要攻坚阶段.科学技术一直是我国发展过程的关键因素.党中央高瞻远瞩,制订了"星火计划"、"火炬计划"以及"863计划"等重大科研发展计划,并取得了重要的科研成果.当前,国内外的科技环境已经发生了深刻的变化,许多国家为能在新一回合的科技竞争中取得优势,都纷纷制订了相应的科技发展计划.产学研结合有着特殊而重要的意义,鉴于我国的实际情况,结合发达国家的基本经验,本文以英国为研究对象,论述了英国在制定与实施重大科技计划的基本做法,对我国在制定重大科技计划时有一定的借鉴意义与参考价值. 相似文献
20.
图书目录在我国有着悠久的历史.作为我国现存最早的图书目录--<汉书@艺文志>是班固尊重刘歆的编目思想,以<七略>为根据而成的一部反映上古至两汉末年这一时期历史文献的重要参考资料,<汉书@艺文志>同时也保持了<七略>的基本内容. 相似文献