共查询到19条相似文献，搜索用时 78 毫秒
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本文对国产棕榈藤3属21种茎的表皮组织进行了系统的比较观察,首次报道了棕榈藤茎表皮细
胞的排列式样,并结合表皮细胞类型和气孔、“反射体”的有无等特征,将国产棕榈藤茎的表皮组织划分
为3种类型3种亚型。(1)钩叶藤型:表皮细胞为长方形,细胞交错排列呈砖墙状。(2)黄藤型:表皮细
胞为不规则的四边形,细胞排列呈不规则网状,如龟背。(3)省藤型:A亚型,表皮细胞六边形,细胞排列
呈网状,气孔平列型或四轮列型;B亚型,表皮细胞四边形,细胞交错排列呈砖墙状,细胞长轴平行于茎轴,气孔梭状四轮列型;C亚型,表皮细胞四边形,垂周壁呈波浪状,细胞交错排列如砖墙状,细胞的长轴.平行于茎轴。本文还讨论了棕榈藤茎表皮组织的特征及其在分类上的意义。 相似文献
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The present paper reports the first record of the genus Hymenopyramis in China.
H. cana is a new record on Hainan Island of Guangdong Province. It grows in deciduous mon-
soon forests or shrubby savanna (western Hainan) at 50 to 150 m alt. 相似文献
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藤山柳属Clematoclethra(猕猴桃科)是中国特有属之一。本文作者研究了该属植物的
外部形态，统计了473张标本，结合地理分布，得出本属是一个单种属，并且是一个多型种的结
论。此种分为4个亚种。这与中国植物志的作者将本属分为20种和4变种不同。 本文作者
虽强调标本室分类是生物系统学研究的基础，是必不可少的一步，但这种分类，其方法上必须
根据大量标本，从研究性状变异开始，然后确定各分类群的划分和等级，最后才根据植物命名
法规的模式方法，给予它们正确名称。作者还根据本属的姊妹群猕猴桃属和它们的外类群水 东哥属的地理分布，推断本属是一个新特有属。 相似文献
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夏念和 《中国科学院研究生院学报》1992,30(5):471-472
Based on the study of Chinese specimens, Pyrularia bullata Tam, P.
inermis Chien and P. sinensis Wu are recognized as new synonyms of P. edulis
( Wall. ) A. DC. Dendrotrophe frutescens( Champ. ex Benth. ) Danser var.subquinquenervia(Tam )Tam is reduced to D. frutescens (Champ. ex Benth. ) Denser. 相似文献
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陈伟球 《中国科学院研究生院学报》1990,28(4):299-306
This paper presents an introduction to the materials for Chinese Galium
Linn. (Rubiaceae). Thirteen species and eight varieties are recorded in the paper.
Among these, two species and two varieties are new, eleven species and five varietiesare new to China, and one variety is a new grade. 相似文献
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本文通过形态学和植物化学的比较研究探讨了鹅绒藤类群的分类等级问题。 化学资料表明，广义鹅绒藤属的地梢瓜组含有萝藦科中甚为独特的黄酮醇成分，而未检出普遍存在于这一类群的C21甾体化合物。 作者认为黄酮醇是新等级地梢瓜属的特征成分。 通过对狭义鹅绒藤属、白前属、地梢瓜属、隔山消属和杯冠藤属的分析，认为隔山消组和杯冠藤组也应恢复其属级地位。 相似文献
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Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
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A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
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Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
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Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
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Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
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Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
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Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
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《中国科学院院刊(英文版)》2014,(3)
<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence 相似文献
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Chinese Scientists Use Earth Observation Technologies to Study and Protect Wild Camels 总被引：1，自引：0，他引：1
《中国科学院院刊(英文版)》2014,(3):267-268
<正>Chinese scientists plan to apply Earth Observation technologies to protect the critically endangered wild camels(Camelus ferus).With the help of remote sensing,satellite positioning,geographical information system and wireless sensors networks,they will be able to access the distribution and population of the wild camels and protect their habitats.The project will be carried out by the International Research Center for Wild Camel Conservation,which was jointly established earlier this year by the Institute of Remote Sensing and Digital Earth(RADI)of the Chinese 相似文献