共查询到20条相似文献，搜索用时 93 毫秒
1.
中国是世界上水稻栽培的起源国,在中国广为栽种后,逐渐传播到世界各地。按照不同的方法,水稻可以分为籼稻和粳稻、早稻和中晚稻、糯稻和非糯稻。水稻所结稻枉去壳后称大米或米。世界上近一半人口,都以大米为食。由于东北地区土地肥沃,水质优良,生长期长,使东北大米的质量受到各地人民的欢迎。 相似文献
2.
红河油田位于鄂尔多斯盆地西缘天环拗陷南部,其主力开发层位为三叠系延长组长8油层组。储层岩石类型主要是岩屑长石砂岩,少数样品中为长石岩屑砂岩,粒度主要为细一中粒,以细粒为主。储层平均有效孔隙度为10.3%,平均有效渗透率0.27×10-3μm2,属于低孔特低渗储层。储层毛管压力曲线呈陡斜式分布,基本无平台发育,排驱压力较高,属于细喉型储层。依据物性和压汞曲线形态及参数特征,将储层毛细管压力曲线划分出三种类型,Ⅰ、Ⅱ类为有效储层,而Ⅲ类为无效储层。砂岩共有4种孔隙组合类型,其中以剩余原生粒间孔+次生粒间孔+粒内溶孔+铸模孔组合为主。 相似文献
3.
<正>0引言我国杂交粳稻的研究始于20世纪60年代,在滇型杂交粳稻的研究方面,从1965年发现败育株并育成我国第一个粳型不育系——红帽缨不育系(即滇型不育系)以来,迄今已育成10种不同细胞质类型的滇型不育系,先后组配成功粳型杂交组合"滇杂31"和"滇杂32"、"滇杂35"、"滇杂46"等,其中的部分组合在云南生态条件下屡创粳稻高产和超高产新纪录,在云南省、贵州省、四川省等地具有较好的推广价值。 相似文献
4.
5.
水稻在各个生育阶段会因不良环境条件,或栽培管理不当而引起种种生理障碍。常见的主要有烂秧、发僵、早穗、早衰、翘稻头以及空、秕粒等,每年天津市华明镇发现水稻存在生理障碍的面积约8000亩,不仅影响水稻正常生长,同时严重影响产量和品质。 相似文献
6.
海外研发主要包括“开发利用型”和“探索学习型”这两种类型,并且已有的研究多关注于发达经济体研发区位选择的影响因素,对于新兴经济体研发区位选择影响因素的关注较少。本文利用2002-2014年我国在“一带一路”沿线35个国家参与研发活动企业的数据,基于负二项回归面板模型,考察了国家距离对我国企业“开发利用型”海外研发区位选择的非线性影响。研究发现：总体上制度距离、经济距离与海外研发区位存在倒U型关系,而文化距离、地理距离分别与海外研发区位呈负向和正向关系;2002-2008年之前,文化距离、地理距离与海外研发投资区位呈正U型关系,制度距离与海外研发区位呈正向关系;2008年以后,文化距离、制度距离、经济距离均与海外研发区位存在倒U型关系,地理距离与海外研发区位呈负向关系。 相似文献
7.
8.
中国主要禾本科植物花的基本类型与系统分类 总被引：1，自引：0，他引：1
本文研究、分析了禾本科33个族、174个属(632种)的花的性状；讨论了重要性状演化
的趋势。根据花、尤其花中鳞被的比较形态，把禾本科植物的花概括为三大类型七个亚型：竹
型(包括真竹亚型，稻亚型、芦竹亚型、针茅亚型)、早熟禾型(含早熟禾亚型)和黍型(包括画眉
草亚型，真黍亚型)。其结果与花的基本类型相对应的大类群，以及与幼苗基本类型、颖果基本
类型相对应的大类群是一致的，即竹亚科、稻亚科、芦竹亚科、针茅亚科、早熟禾亚科、画眉草亚 科，黍亚科。 相似文献
9.
鸭稻共作对水稻植株生长性状与产量性状的影响 总被引：7，自引：0，他引：7
本研究通过大田小区对比实验,探讨了鸭稻共作对水稻植株生长性状与产量性状的影响效果。研究结果表明,鸭稻共作在一定程度上降低了水稻植株的高度和水稻地上部的生物量,但增大了水稻地下部的生物量和根冠比,有利于水稻地下部根系的发育,并在一定程度上增强了水稻的抗倒伏能力;同时,鸭稻共作能提高水稻中后期叶片的叶绿素a和叶绿素b的含量以及叶绿素a/b值,可防止水稻在后期的过早枯黄与衰败,从而增强水稻叶片光合作用的性能及其持续时间;鸭稻共作还能够促进水稻的有效分蘖,增加水稻的有效穗数和成穗率,减少空(秕)粒数,提高水稻的实粒数和结实率,从而有利于水稻产量的形成。这些研究结果可为鸭稻共作生态技术的生产实践与示范推广提供理论依据。 相似文献
10.
11.
《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
12.
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
13.
《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
14.
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
15.
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
16.
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
17.
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
18.
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
19.
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
20.
Prof. SUN Changpu from the CAS Institute of Theoretical Physics coworkers from University of Basel in Switzerland have worked out a way - at least in theory - to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams is similar to the famous Stern-Gerlach effect whereby a beam of atoms passing through a magnetic field is split in two according to the atoms' spin states 《中国科学院院刊(英文版)》2008,22(1):23-23
Prof. SUN Changpu from the CAS Institute of Theoretical Physics and coworkers from University of Basel in Switzerland have worked out a way --at least in theory --to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams and is similar to the famous Stern-Gerlach effect, whereby a beam of atoms passing through a magnetic field is split in two according to the atoms＇ spin states （Phys. Rev. Lett. 99 130403）. 相似文献