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本文对极地海洋病毒的国内外研究现状进行了扼要阐述,尤其是海冰融化对病毒的生态影响。内容包括极地海域的浮游病毒丰度、多样性及在碳循环中的作用研究,以及我国在极地科考中所进行的与浮游病毒相关的工作。并提出了今后在极地海域要解决的与病毒相关的科学问题。 相似文献
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Although tornadoes are microscale meteorological features, their occurrence is linked to the larger synoptic-scale environment. Most conceptual models of synoptic situations that give rise to tornadoes are based on conditions prevalent in the Great Plains of the United States. However, tornadoes develop in many different synoptic environments, particularly when they form beyond the boundaries of “Tornado Alley.” Tornado occurrences in the state of Virginia are identified from 1951 through 1992. Using upper air data for the nearest site and observation time, a synoptic classification is produced via application of principal components analysis and cluster analysis. The five resulting synoptic classes each exhibit distinctive thermodynamic and flow conditions that serve as air-mass paradigms for tornado occurrence in Virginia. The groups include thermodynamic/northwest flow air masses, a mixed thermodynamic/dynamic category, a polar front jet situation, cool season midlatitude cyclone events, and Great Plains type tornadic air masses. A sixth type, tornadoes spawned by tropical systems, is defined separately. A variety of indices have been developed by forecasters to provide information about the likelihood of severe weather and tornadic activity. The lifted index, K-index, Showalter index, SWEAT, Totals index, and a wind shear index are calculated for each tornado event. Analysis of variance indicates that most of these indices are statistically different between synoptic classes. These results suggest that the synoptic-scale mechanisms responsible for tornado occurrence in the mid-Atlantic states are quite variable. Enhanced predictive capability could be gained by considering the prevailing synoptic conditions associated with individual storms. [Key words: synoptic climatology, tornadoes, Virginia, classification, severe weather.] 相似文献
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Barry M. Moriarty 《The Professional geographer》1982,34(3):322-331
Geographers have become increasingly interested in who receives grants for basic research and why. Northeastern U.S. universities, and especially private universities in the Northeast, dominated those of all other regions in the number of proposals submitted to the Geography and Regional Science Program of the National Science Foundation as well as the number of funded projects and total awarded funds during the period 1979–1981. Successful grant applicants submitted proposals that demonstrated excellent potential to make a significant contribution towards improving the theoretical and methodological foundations of geography. 相似文献
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BY GREGORY C. WILES DAVID J. BARCLAY NICOLÁS E. YOUNG 《Geografiska Annaler: Series A, Physical Geography》2010,92(1):101-109
In Alaska, lichenometry continues to be an important technique for dating late Holocene moraines. Research completed during the 1970s through the early 1990s developed lichen dating curves for five regions in the Arctic and subarctic mountain ranges beyond altitudinal and latitudinal treelines. Although these dating curves are still in use across Alaska, little progress has been made in the past decade in updating or extending them or in developing new curves. Comparison of results from recent moraine-dating studies based on these five lichen dating curves with tree-ring based glacier histories from southern Alaska shows generally good agreement, albeit with greater scatter in the lichen-based ages. Cosmogenic surface-exposure dating of Holocene moraines has the potential to test some of the assumptions of the lichenometric technique and to facilitate the development of a new set of improved lichen dating curves for Alaska. 相似文献
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本文利用1984/85年我国首次南大洋考察带回的燐虾样品,采用氟试剂比色法,分析研究了南极大燐虾(Eunhausia Superba)的氟含量,结果表明:南极大燐虾含有很高的氟.虾壳含氟量最高,平均为4303mg/kgF;其次是头胸部,为1890mg/kaF;整体含氟量为1191mg/kgF;肌肉中最低,为370mg/kgF.雄性燐虾与雌性燐虾对氟的吸收和需求不同.冰冻贮存的大燐虾氟含量超出了美国食品药物管理局规定的二十多倍.新鲜脱壳虾肉氟含量只有60mg/kgF,是冰冻贮存燐虾肌肉氟含量的16%左右.富集氟是各种燐虾特有的生理功能,不仅南极燐虾有,其它海区的燐虾也有. 相似文献
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黑河下游干旱地区环境变化研究 总被引：16，自引：3，他引：16
额济纳旗绿洲是典型的干旱荒漠天然绿洲，是河西走廊及内陆地区的一道绿色屏障。通过对额济纳旗绿洲土地利用情况的遥感调查，证实了额济纳旗绿洲生态环境恶化的严重性。对处于干旱区的额济纳旗绿洲环境变化的研究，分析了干旱地区环境变化的因素，表明干旱区生态环境保护的必要性和迫切性。 相似文献
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The effect of distance upon agricultural production should be as apparent among primitive subsistence agriculturalists as in market-oriented societies. This analysis of yield variations among the Basotho of southern Africa attempts to determine the frictional effect of distance. The results show that distance does not explain variations in yield even when other physical factors are held constant. Perhaps such variables as household characteristics, not included in the analysis, would provide a better explanation. 相似文献
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资源型城市的可持续发展优化及案例研究 总被引：11，自引：1，他引：10
郑伯红 《云南地理环境研究》1999,11(1):51-56
资源型城市是伴随着资源开发而兴起的, 其发展前景受资源条件和社会经济的双重制约。通过分析资源型城市生命周期阶段的特征和问题, 提出了其可持续发展优化的方向为： 延长资源开发利用周期, 避免城市过早步入衰退期; 调整城市发展规划, 改变城市生命趋向; 同时进行行政区域调整, 转变城市职能。最后, 以湖南省冷水江市为例, 进行了实证分析。 相似文献
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刘奥东 《云南地理环境研究》2008,20(1):122-127
目前,乡村旅游得到了前所未有的发展,但其主要集中在经济发达城市的周边地区。该文旨在探讨象张家界这样不具备区位优势的中小型专业化旅游城市,如何发展独具特色的乡村旅游,并给出了一个参考思路,即依靠传统观光型旅游的带动。在这一思路指导下,对张家界的乡村旅游发展进行SWOT分析,提出了乡村旅游开发的宏观和微观建议。 相似文献
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广东封开的几种特色地貌 总被引：1，自引：0，他引：1
封开县有4种地貌属广东之最:①一石成山,几乎无缝隙的斑石;②贺江弯曲率为3,下切深度100～200 m的深切曲流;③动物化石十分丰富的河儿口黄岩洞,罗沙岩和峒中岩等溶洞;④阶地高度最大达76m的西江河流阶地.上述有较重要的科研、科普和旅游开发价值,要继续发掘,推动旅游事业进一步发展. 相似文献
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海南岛棕榈科植物研究 总被引：5，自引：0，他引：5
本文通过对海南岛棕榈科植物资源的调查研究，认为全岛共有棕榈科植物３２属６８种，其中天然分布的有１１属３２种，引种有２１属３６种，文中介绍了海南岛棕榈科植物的用途与天然分布，描述其生态特片，对如何开发利用与保护提出了具体的措施和途径。 相似文献
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资源最优空间配置的系统经济理论研究 总被引：3，自引：0，他引：3
本文不仅研究了包括生产、消费、资源的空间配置和空间位置差异的一般经济均衡条件,而且还以大系统多级递阶控制原理,建立了统一协调的系统经济数学模型。该模型深刻地揭示了生产、消费、资源的空间配置与空间位置差异之间的相互关系,同时也是区位论的一种理论模式。 相似文献
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县级山区月平均气温推算方法 总被引：12，自引：0，他引：12
本文根据山区月乎均气温形成的主要物理过程,提出以海拔高度、坡地太阳总辐射、地形动力因素为因子的新的月乎均气温推算方法,并以浙江龙泉山区为例进行拟合和计算。经检验,平均拟合误差为0.2℃,最大误差不超过0.4℃。 相似文献
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三江平原沼泽地碳循环初探 总被引：35，自引：1，他引：35
在三江平原多年考察与研究的基础上，通过典型沼泽的定位观测，估算了三江平原沼泽土壤中的碳储量，探讨了沼泽植物对大气ＣＯ２的固定，碳素自沼泽土壤向大气的转移，沼泽近地气层ＣＯ２流，以及沼泽植物－土壤－大气之间的碳素流动。 相似文献
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中国农业类型划分的初步研究 总被引：3，自引：2，他引：3
农业类型是系统反映农业分布差异特征的农业生产地域综合体。我国农业生产条件复杂,地域差异显著,类型分布多样。本文按照土地利用、产值结构、集约程度、产出效益、商品化特征和农业自然条件等方面的依据指标,将全国划分为12个一级类和122个二级型。 相似文献
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卢小丹 《云南地理环境研究》2008,20(Z1):106-109
采用常规气象资料和NCEP再分析资料,对桂西2008年5月29~30日一次大范围暴雨天气过程进行分析。结果发现,活跃的西南季风给桂西上空输送水汽和不稳定能量,是此次暴雨发生的突出特点;南支槽的东移、850hpa切变线南压、地面冷空气南下是暴雨产生的直接影响系统;水汽通量散度表示的水汽辐合区与暴雨中心较为对应,散度场、垂直速度场的相互配置,使暴雨系统加强,K指数、SI指数对暴雨发生有一定指示意义。 相似文献