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排序方式: 共有393条查询结果,搜索用时 312 毫秒
161.
冬小麦产量性状的遗传研究   总被引:2,自引:0,他引:2  
在灌溉和雨养两种生长环境下,对小麦产量性状的配合力和遗传力进行了研究.结果表明,在两种生境下,产量性状的一般配合力均达到显著性差异,特殊配合力只有单株成穗与单株产量在雨养条件下不显著;各性状的遗传均以加性效应为主;其广义遗传力在两种条件下较一致,而狭义遗传力的大小则存在着差异性;不同亲本间及同一亲本不同性状或同一性状的遗传传递力的整齐度在灌溉条件下和雨养条件下相异.说明在不同生境中,产量性状的遗传存在着不同的遗传方式.表4参13  相似文献   
162.
AdiagnosticexperimentoftheinfluenceofCO_2onwinterwheatWangChunyi;BaiYueming;WenMin(ChineseAcadernyofMeteorologicalSciences,Be...  相似文献   
163.
Spatial patterns of various criteria air pollutants,like SO2, NO2, O3, and TSP were studied atShahdara National Ambient Air Quality Monitoring stationin Delhi (India) in July 1999. The minimum pollutantconcentrations were observed during morning hours,whereas the highest concentrations were found during thelate night hours, which seem to be related with thevehicular emission. Pre-monsoon daily ambient airquality spatial pattern was compared with the spatialpattern during initial and subsequent rain shower ofmonsoon. These spatial patterns were found to beessentially the same before and during rain, however asignificant decrease in SO2, NO2 and TSPconcentrations (40-45%) was observed after initial andsubsequent rains of the monsoon, demonstrating theimportance of rainfall in the scavenging of thesecriteria air pollutants.  相似文献   
164.
Analysis of summer and winter vegetable samples during 2002–2003 for pesticidal contamination was carried out on Gas Chromatograph-Electron Capture Detector with capillary columns. The contamination levels of winter vegetables (average concentration of 4.57, 6.80 and 5.47 ppb respectively for Lindane, Endosulphan and DDT) were found to be slightly higher than the summer vegetables (average concentration of 4.47, 3.14 and 2.82 ppb respectively for Lindane, Endosulphan and DDT). The concentration of these organochlorine pesticides in summer and winter vegetables were well below the established tolerances but continuous consumption of such vegetables even with moderate contamination level can accumulate in the receptor's body and may lead to chronic effects that could be fatal.  相似文献   
165.
Abstract: More than 85% of NO3? losses from watersheds in the northeastern United States are exported during winter months (October 1 to May 30). Interannual variability in NO3? loads to individual streams is closely related to interannual climatic variations, particularly during the winter. The objective of our study was to understand how climatic and hydrogeological factors influence NO3? dynamics in small watersheds during the winter. Physical parameters including snow depth, soil temperature, stream discharge, and water table elevation were monitored during the 2007‐2008 winter in two small catchments in the Adirondack Mountains, New York State. Snowpack persisted from mid‐December to mid‐April, insulating soils such that only two isolated instances of soil frost were observed during the study period. NO3? export during a mid‐winter rain‐on‐snowmelt event comprised between 8 and 16% of the total stream NO3? load for the four‐month winter study period. This can be compared with the NO3? exported during the final spring melt, which comprised between 38 and 45% of the total four‐month winter NO3? load. Our findings indicate that minor melt events were detectable with changes in soil temperature, streamflow, groundwater level, and snow depth. But, based on loading, these events were relatively minor contributors to winter NO3? loss. A warmer climate and fluctuating snowpack may result in more major mid‐winter melt events and greater NO3? export to surface waters.  相似文献   
166.
Abstract: Mid‐range streamflow predictions are extremely important for managing water resources. The ability to provide mid‐range (three to six months) streamflow forecasts enables considerable improvements in water resources system operations. The skill and economic value of such forecasts are of great interest. In this research, output from a general circulation model (GCM) is used to generate hydrologic input for mid‐range streamflow forecasts. Statistical procedures including: (1) transformation, (2) correction, (3) observation of ensemble average, (4) improvement of forecast, and (5) forecast skill test are conducted to minimize the error associated with different spatial resolution between the large‐scale GCM and the finer‐scale hydrologic model and to improve forecast skills. The accuracy of a streamflow forecast generated using a hydrologic model forced with GCM output for the basin was evaluated by forecast skill scores associated with the set of streamflow forecast values in a categorical forecast. Despite the generally low forecast skill score exhibited by the climate forecasting approach, precipitation forecast skill clearly improves when a conditional forecast is performed during the East Asia summer monsoon, June through August.  相似文献   
167.
自然景观遥感解译基础上的华中自然区划研究   总被引:3,自引:1,他引:2  
在自然景观类型的卫星图像解释和制图的基础上,通过对自然景观类型分布规律的定性分析和定量计算,自下而上归并与自上而下划分相结合,将华中地区划分为5个自然区、19个自然亚区和30个自然小区。  相似文献   
168.
对石笋多指标的研究有利于全面理解季风气候事件的变化特征和机制。以湖北永兴洞YX55石笋为研究对象,通过高精度U/Th定年和多指标分析重建了65~35 ka B.P.石笋灰度和稳定同位素的变化序列。在65~40 ka B.P.时段,石笋灰度、δ13C与δ18O都呈现出数个千年至亚千年尺度的变化,但δ13C变化幅度比δ18O小得多。这说明灰度和δ13C这类代表局域气候的指标,都响应于δ18O指示的Heinrich(H)事件和Dansgaard-Oeschger(DO)旋回,但响应的程度各不相同。H4期间,石笋δ13C和灰度呈现不一致变化:δ13C不像在其他H事件一样小幅振荡,而是大幅正偏(相当于其他H事件2~3倍);灰度则显示出和DO旋回一致的特征。这种δ13C/灰度与δ18O异常响应关系可能的机制是:H4期间季风强度急剧减弱,使得洞穴上覆土壤覆盖率大幅降低,从而削弱或阻止了土壤—岩溶系统的过滤能力,使石笋中杂质含量异常增加。  相似文献   
169.
There is a growing recognition that scientific and social conflict pervades invasive species management, but there is a need for empirical work that can help better understand these conflicts and how they can be addressed. We examined the tensions and conflicts facing invasive Asian carp management in Minnesota by conducting 16 in-depth interviews with state and federal agency officials, academics, and stakeholders. Interviewees discussed the tensions and conflicts they saw impacting management, their implications, and what could be done to address them. We found three key areas of conflict and tension in Asian carp management: 1) scientific uncertainty concerning the impacts of Asian carp and the efficacy and non-target effects of possible management actions; 2) social uncertainty concerning both the lack of societal agreement on how to respond to Asian carp and the need to avoid acting from apathy and/or fear; and 3) the desired approach to research and management – whether it is informed by “political need” or “biological reality”. Our study of these tensions and conflicts reveals their importance to Asian carp management and to invasive species management, more broadly. We conclude with a discussion of possible ways to address these areas of tension and conflict, including the potential of deliberative, participatory approaches to risk-related decision making and the need to productively engage with apathy and fear.  相似文献   
170.
This paper presents a review of energy use in 22 selected countries of Asia and estimates the anthropogenic emission of sulphur dioxide (SO2) for the selected countries, both at national and disaggregated sub-country regional levels. The paper also makes a comparative assessment of the Asian countries in terms of SO2emission intensity (i.e. emission per GDP), emission per capita and emission density (i.e. emission per unit area). Total SO2emission in the region was estimated to be about 38 million tons in 1990. Five countries, China, India, South Korea, Japan and Thailand, accounted for over 91% of the regional SO2emission. Coal use had the dominant share (81%) of the total emission from the region. Among the economic sectors, industry contributed the largest share (49%) to the total emissions of the selected countries as a whole, followed by the power sector (30%). These findings suggest the need for mitigation strategies focussed on the industry and power sectors of the major emitting countries in Asia.  相似文献   
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