共查询到20条相似文献，搜索用时 531 毫秒
1.
黄宗捷 《成都信息工程学院学报》2002,17(2):116-121
大工业生产特有的生产资料是机器，而网络生产特有的生产资料却是网络，在网络生产条件下，知识和信息成为核心的生产要素，传统的生产函数发生变化，网络生产的边际收益递增。 相似文献
2.
祝卓 《中国地理科学(英文版)》1991,1(2):129-140
Cotton is the leading cash crop in China. The cotton sown area accounts for about 30per cent of the total sown area of all the various cash crops. It is the main material used in the textile industry in China. More than 95per cent of textile materials were cotton during the 1950s; and it still occupies 80per cent at present. There are some problems concerning rational location of cotton production in China. In order to solve the problems existing in civil cotton production and supply, in view of strategy, a number of cotton production bases must be selected and built step by step in a planned way. The location of cotton production should be adjusted progressively in accordance with the existing problems. The existing cotton production regions should be consolidated and improved. The cotton production region of the middle and lower reaches of the Huanghe River should be renewed quichly to make it become the largest stable and high-yield cotton preduction region. In the regions with suitable natural condi 相似文献
3.
The authors studied variations of temperature and salinity in seawater under sea ice using hydrologic data collected from
polynyas south of the St. Lawrence Island during March of 2008 and 2009. The results indicate that the high-salinity water
found during the cruises of 2008 and 2009 was due to the formation of polynyas. The salinity observed in 2008 was higher than
that in 2009 as a result of higher salt production in 2008. The spatial distributions of high-salinity cores differed between
the two cruises. In March 2008, a southeastward flow was formed under the persistent northerly wind in the observation region,
which transported the high-salinity water produced by the polynyas to the southeast. The similar flow, however, did not exist
in March 2009 because the northerly wind over the study area was interrupted by a southerly wind. Accordingly, the polynyas
and the high-salinity water produced by them existed for a short time. As a result, the high-salinity water in 2009 did not
spread very far, and stayed within the polynyas. In addition, during the 2009 cruise, two stages of observations in the polynyas
showed the core of high-salinity water was shifted to the southwest of the St. Lawrence Island. This result suggested that
a southwestward flow might have existed in the area at the onset of the northerly wind, which was consistent with the alongshore
and/or offshore flows caused by the northerly wind. 相似文献
4.
天然气水合物开采井眼出砂问题是当前水合物产业化急需突破的瓶颈之一,解决水合物开采时防砂与产能平衡问题是实现水合物安全高效、长期可控开采的关键.我国海域典型水合物储层属于弱固结的低渗泥质粉砂储层,其面临的防砂控泥与增产矛盾较为突出.厘清不同水合物储层和开采条件下的井眼出砂规律并揭示其机理,进而制定科学合理的防砂控泥措施以实现产能最大化是解决上述矛盾的途径所在.从理论分析、数值模拟、室内实验和现场试采4个角度介绍了世界范围内已开展的水合物出砂防砂情况,分析总结了水合物储层出砂影响因素及出砂机理,最后探讨了目前出砂研究存在的问题和挑战,并给出了相应的建议,旨在为后续水合物开采井眼出砂预测和防控研究提供思路和参考. 相似文献
5.
6.
Vishwambhar Prasad Sati 《山地科学学报》2005,2(4):319-328
Introduction In the Alakananda Basin, undulating terrain constitutes the most fragile elements of the ecosystem. Traditional economy rests on the terraced cultivation with extremely limited viability to expansion and modernization. Consequently, low economic return remains the characteristic feature of the agrarian landscape. It is the common experience that the ecological conditions of the basin are more suited to fruit cultivation rather than cereal farming (Atkinson 1889). Along with frui… 相似文献
7.
何险峰 《成都信息工程学院学报》1993,(4)
神经网络专家系统外壳软件,是用于帮助用户迅速开发直观图形解释的人工智能业务应用系统。它以直观的屏幕树图为媒介,实现了正、反向推理机、语义网络、神经元网络、框架结构、知识库管理和算术表达式树图等整体宏观统一;实现了专家系统与人工神经元网络、定性分析与定量计算的统一;无监督分类与监督分类的统一。因此,它的应用范围很广。 相似文献
8.
张永志 《大地测量与地球动力学》1992,(4)
本文根据一个非线性动力学模型,应用耗散结构理论和Lyapunov稳定性理论,讨论了震前地壳在与外界同时存在物质和能量交换时的动力学行为和超熵判据,并分析了拉仲试验过程中的超熵变化。对100km~3体积的弹性体,用地壳的实际参数进行了形变与震级的对应关系计算。最后,分析和讨论了青海省门源6.4级地震前地壳的超熵变化过程。 相似文献
9.
ZHU Luying ZHANG Xuecheng REN Xueying ZHU Qinghua 《中国海洋大学学报(英文版)》2008,7(1):83-88
The effects of temperature, initial pH, salinity of culture medium, and carbon and nitrogen sources on growth and docosahexaenoic acid （C22：6 n-3, DHA） production from Schizochytrium limacinum OUC88 were investigated in the present study. The results revealed that the optimal temperature, initial pH and salinity level of the medium for DHA production were 23 ℃, 7.0 and 18, respectively. Glucose was proved the best carbon source for the growth and DHA production from S. limacinum. Among the nitrogen sources tested, soybean cake hydrolysate, a cheap by-product, was found to be effective for the accumulation of DHA in S. limacinum cells. In addition, increasing the concentration of carbon sources in the medium caused a significant increase in cell biomass; however, accumulation of DHA in cells was mainly stimulated by the ratio of C/N in the medium. Under the optimal culture conditions, the maximum DHA yield achieved in flasks was 4.08 g L^-1 after 5 d of cultivation 相似文献
10.
Northeast region covers an area of 1.24 million km, making up 12.9% of the total area of China, with a population of 103 million, 9.9% of the total population of China. The grain commodity rate is over 35%. It is one of the very important regions of grain production in China. As population and grain demand unceasingly increase, the potential of grain production, and the commodity grain provided for the nation are the major problems about grain consumption and distribution in the future. And they directly affect the realization of national planning objective of grain production.The analysis of grain production conditions and history indicates that: 1) The increase of total grain output is mainly dependent on the increase of grain yield per unit area, but not the enlargement of grain sown area. 2) The factor to affect grain yield per unit area are materials input, correct policies, yearly climatic variation. 3) By the year 2000 and 2010 the total grain output in this region will be respectively 66.16-66.2 相似文献
11.
湛江沿海渔民转产转业的形成原因有:过度的近海捕捞,严重的海洋环境污染,近海的捕捞渔民的经济效益下降和作业渔场面积减少。存在的问题有:需转产转业的渔民数量大,支持转产转业的资金数量有限,渔民综合素质较低,退出捕捞行业的成本高。在此基础上提出了解决沿海捕捞渔民转产转业问题的措施有:政府出台相关的财政政策,积极发展海水养殖业,积极发展滨海旅游业与休闲渔业相结合,调整经济结构,加快工业化的进程。 相似文献
12.
本文报道了为改变我国华南沿海目前在半咸淡水塘中进行地播式裁培细基江篱繁枝变种单产低的状况而进行的不同水层夹苗栽培和施肥增产试验,证明了越靠近水面江篱藻体生长越快,越接近底部藻钵生长越差,提出如果在水塘中单纯裁培江篱则水塘深度应保持20～30厘米,如果水深超过1米以上,则应采用浮筏式夹苗栽培,并在水中混养鱼虾等。浸泡施肥试验证明,在短短的40天裁培过程施肥藻体比不施肥藻体增产23％,说明了施肥的重要性。 相似文献
13.
济宁煤田为鲁西地区的主要煤田之一,岱庄井田位于济宁煤田的中北部,总体呈向SE倾斜的单斜断块构造。岱庄井田内构造以断裂为主,NE向、近SN向和NW向3组断层互相交叉、切割,致使煤层错动,影响工作面和巷道的布置,造成煤炭资源的损失。该文通过对已有地质资料的分析研究,提出在今后生产过程中应采取探、采结合的方式查明断层的构造特征,以达到充分合理开发煤炭资源的目的。 相似文献
14.
煤田信息是一种活跃的、动态变化的、与空间位置密切相关的信息。信息的合理化管理直接影响到煤矿安全问题的预测和防治工作,其涉及的数据信息量十分巨大,基于煤田信息的特征和信息化的现状,结合地理信息系统技术、计算机技术、网络技术以及虚拟现实技术等关键技术开展"数字煤田"研究,能更好地实现煤田信息的一体化管理。本文借助山西数字煤田信息系统的设计思路,具体阐述其涉及到的关键技术和方法,希望对提高煤炭企业安全生产信息化水平,保证煤炭的安全生产和运营决策起到一定的指导意义。 相似文献
15.
Ｓｏｉｌｉｓａｎｅｐｉｇｅｎｅｔｉｃｓｐｈｅｒｅｈａｖｉｎｇｔｈｅｄｅｎｓｅｓｔｂｉｏｌｏｇｉｃａｌｍａｓａｎｄｔｈｅｈｉｇｈｅｓｔｂｉｏｌｏｇｉｃａｌｅｎｅｒｇｙ,ｗｈｉｃｈｉｓａｂａｓｅｍｅｎｔｐｒｏｖｉｄｉｎｇｔｈｅｐｌａｎｔｗｉｔｈｗａｔｅ... 相似文献
16.
This paper introduces the experiences and models of land resources use in China. They are: (1) to protect farmland is as the basic state policy; (2) to carry out land resources survey and land use planning; (3) establishing a resource-saving agricultural production system with land saving as its priority; (4) to develop agriculture in the whole territory and explore food resources; (5) improving eco-environment and protecting land resources; (6) population control'and moderate consumption to release the pressure on land resources; (7) the integrated development and experiment of the typical regions. 相似文献
17.
Pedogeochemistry of China is controlled by such factors as biology, climate, parent material, topography and anthropogenesis,
and the different geochemical types are formed under the different conditions of soil formation which have different abundance
levels of elements. The relationship between concentration of elements and plant growth and human health depends upon available
forms of element in soils. While the factors affecting element availability are soil pH and Eh, tillage and fertilization
by man besides element forms in soils. On the basis of pedogeochemical types and distribution, rational plantation and application
of fertilizer to soils will be of great significance for sustainable development of agricultural production. 相似文献
18.
In this paper,
the feed value of the larva of pinc tada fucata in the production of the fry of tiger
shrimp, Penaeus monodon, were studied. The mollusk larva were gained by inducing spawning
or artificial f ertilization of the eggs from living pearl oysters or discarded oyster
cadaver. Comparisons of the nutrition values of oyster larva and brine shrimp (Artemia
nauplii) for the larvae of Penaeus monodon were carried out. The results a re clear that
the zoaea survival rate in 5 days of tiger shrimp fed with oyster larva was higher than
with larva of brine shrimp the former was 69.8%～71.5% an d later was 64.0%～67.4%, the final survival rate of shrimp fry fed with
larva o f brine shrimp was 49.8%, the highest in the three testing groups. 相似文献
19.
近47年白银市气候变化及其对农业生产的影响分析 总被引：1，自引：0，他引：1
利用白银市4个代表站逐日平均气温、逐日地面最低温度，分别得到≥0℃初终日期、初终霜冻日期以及利用逐月平均气温、平均最高气温、平均最低气温和逐月降水资料，对白银市近47a的气候变化特征进行分析，同时分析了气候变化对农业生产的影响，为充分利用变化了的农业气候资源，减少不利因素带来的影响提出了对策和建议。 相似文献