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81.
鱼类摄食生态研究的理论及方法   总被引:21,自引:1,他引:21  
窦硕增 《海洋与湖沼》1996,27(5):556-561
综合分析了鱼类摄食生态研究的理论,方法及其应用中的诸多问题:胃含物分析法,营养生境及食物重叠,食物链与食物网,营养结构与营养级,摄食器官的形态特征与摄食行为的关系,食物选择以及生理生太因子对鱼类摄食的影响;提出了食物排序的概念、优势度指数D及其判定公式,并以此比较客观地建立了摄食生态相似的鱼类群落主次食物的划分标准。  相似文献   
82.
Using radiosonde data and other related observations in the TOGA-COARE IOP(from November 1,1992 to February 28,1993),the microwave attenuation of non-precipitating clouds is investigated based on microwave radiative transfer model(MRTM) at the specific frequencies of 6.8,10.65,13.9,19.35,22.235,37.0,85.5 and 90.0 GHz.Besides,utilizing the data of the airborne radar and radiometer at 13.8 GHz in the IOP(Intensive Observation Period),vertical structure models for different types of precipitating clouds are obtained,and also the microwave attenuation of precipitating cloud is studied.Some statistical characteristics of 13.8 GHz microwave path integrated attenuation for stratiform and convective precipitating clouds are presented.The results given here are valuable for the spaceborne microwave remote sensing of precipitation,and the cloud and precipitation attenuation corrections in the spaceborne microwave remote sensing of earth surface over tropical ocean area.  相似文献   
83.
采用静态和动态计量方法分析2006~2015年海洋经济对沿海省(市、区)经济发展的影响程度并通过空间计量方法识别差异动因。研究发现:海洋经济对中国省域经济发展具有显著地影响,其中天津、上海、福建、山东、广东、海南海洋经济总量贡献率高于全国平均水平;省域海洋产业对区域经济影响度分异呈现省际绝对差异不断扩大、相对差异不断缩小,且具有显著的空间相关性;引起省域经济增长差异的海洋经济相关因素中,海洋第二产业、海洋进出口贸易额等起到正向促进作用(即拉大差异),且海洋第二产业结构具有显著的溢出效应。相关发现有助于中国沿海省(市、区)经济的协调发展和科学决策。  相似文献   
84.
Abstract Zinc (Zn) and copper (Cu) concentrations were determined in the tissues (muscle, stomach, liver, gills, skin, and gonads) of five commercial fish species (mullet Liza haematocheilus, flathead Platycephalus indicus, mackerel Scomberomorus niphonius, silver pomfret Pampus argenteus, and sea bass Lateolabrax japonicus) from Laizhou Bay in the Bohai Sea. Metal bioaccumulation was highest in the metabolically active tissues of the gonads and liver. Bioconcentration factors for Zn were higher in all tissues (gonads 44.35, stomach 7.73, gills 7.72, liver 5.61, skin 4.88, and muscle 1.63) than the corresponding values for Cu (gonads 3.50, stomach 3.00, gills 1.60, liver 5.43, skin 1.50, and muscle 0.93). Mackerel tissues accumulated metal to higher concentrations than did other fish species, but bioaccumulation levels were not significantly correlated with the trophic levels of the fish. Zn and Cu concentrations in the tissues were generally negatively correlated with fish length, except for a few tissues of sea bass. Risk assessment based on national and international permissible limits and provisional tolerances for weekly intake of Zn and Cu revealed that the concentrations of these two metals in muscle were relatively low and would not pose hazards to human health.  相似文献   
85.
利用常规气象观测数据、NCEP再分析资料和WRF4.0中尺度数值模式,对2019年12月8—15日新疆天山北坡出现的一次持续性大雾天气的成因进行分析。结果表明:此次大雾天气出现在500 hPa新疆脊控制、850 hPa暖中心维持、地面蒙古冷高压影响的环流背景下。雾开始和维持阶段,地面1 200 m存在逆温强度为0.9℃/100 m的强逆温层,为大雾的形成和维持提供了静力稳定条件;大雾一般出现在辐射降温最明显的傍晚前后;大雾天气出现后2 m气温和地面温度温差始终维持在5℃左右,地、气温差使地面积雪一直升华,为大雾天气持续提供了充足的水汽条件;近地层大气一直存在2.0 m/s以下的微风,形成的湍流维持了雾滴悬浮的平衡状态。当逆温层中上层出现6~10 m/s偏东风时,雾层厚度增加;中上层风速过大或地面~600 m风向一致时,雾减弱或消散。  相似文献   
86.
在野外地质和勘查资料分析的基础上,结合区域构造背景,论述了赵楼井田构造发育、组合及分布规律。研究表明:石炭-二叠纪成煤期后,多期性质、强度不同的构造作用相互叠加、改造,致使赵楼井田构造以断裂为主.褶皱发育次之。断裂构造主要有近NS、NW、NE及NNE向四组,其中以NE、NNE向为主,NW向断层组多为落差、延展长度都较小的断层。断裂以正断层为主,在剖面上主要表现为堑-垒构造组合,这种组合特征不仅使矿井构造更加复杂,而且使煤层的连续性受到破坏。井田东南部断层发育,断层叠加于早期的褶皱之上,破坏了褶皱的完整性.构成井田的构造复杂区。赵楼井田构造发育规律及成因机制的研究为今后矿井建设与生产提供了地质依据。  相似文献   
87.
北京城区近地面比湿和风场时空分布特征   总被引:5,自引:1,他引:5       下载免费PDF全文
利用2008—2012年北京城区平均5 km的高密度自动气象站逐时观测数据,分析了北京城区近地面比湿、风向和风速的时空精细分布特征,初步探究了城市下垫面对局地气象要素的影响机制。研究表明:夏季白天北京城区为干岛,冬季城区表现为弱湿岛特征。受城市效应的影响,北京城区与郊区比湿日变化有明显差异。近地面10 m风受到地形、城市和季节性盛行风的共同影响。当气流经过城区时有明显的绕流现象。夏季05:00—10:00 (北京时,下同),受山风、弱的夏季偏南风和城市热岛共同作用,气流向城市中心辐合。冬季15:00—19:00,受季节盛行风偏北气流和谷风偏南气流的共同作用,在城区形成一条西北—东南走向的辐合线。对风速研究发现:城市粗糙下垫面使北京城区风速减小,二环路和三环路之间存在一条“n”状的风速小值带。由此可见,除已开展较多研究的城市热岛效应外,北京城市效应对近地面湿度和风场亦有显著影响。  相似文献   
88.
GIS Web Services技术在地下水取水许可管理系统中的应用   总被引:1,自引:0,他引:1  
雷庆玲  窦炜 《北京测绘》2006,(1):9-12,21
主要以地下水取水许可管理系统为例研究和探讨了基于GISWebServices的分布式电子政务系统的设计与实现。该电子政务系统具有和GIS系统无缝集成的优点,可以实现跨平台和异构系统无缝集成,实现了分布式计算。  相似文献   
89.
In this paper, urban-rural temperature, relative humidity and vapour pressure differences at fixed hours in Beijing area were analyzed and compared. The data from one station with different observation surroundings and one rural station (0200, 0800, 1400 and 2000 hours local standard time (LST)) for the period 1971–2003 were used. The effect of urban on local temperature, relative humidity and vapour pressure were discussed. Results showed that the urban environment caused great increase in local temperature at 0200, 0800 and 2000 hours and small increase at 1400 hours. Also, the urban effect on humidity suggested that the urban environment can decrease relative humidity and vapour pressure at all fixed hours, while the urban-rural relative humidity differences are great at 2000 and 0200 hours and the urban-rural vapour pressure differences are great at 1400 and 2000 hours. The annual average temperature, relative humidity and vapour pressure difference between urban and rural are about 1.76°C, 6.3% and 1.5475 hpa during the period from 1981 to 1997, respectively. Results indicated that the urban effect on local temperature and humidity is significant in Beijing area.  相似文献   
90.
The Erlian Basin is located in the Central Asia-Mongolian fold belt between the Siberian and Sino-Korean Cratons. It is a Mesozoic continental rift basin composed of 52 individual fault-depressions. The main phase of rifting took place during the Early Cretaceous when a series of fluvial-lacustrine sediments were deposited. Each depression forms an independent sedimentary system and behaves as an independent petroleum system. Hydrocarbon source rocks are found in the upper Arshan and lower Tengger Formations. These are mainly type II source rocks and are mainly located in oil generation window at the present day. A series of oilfields and commercial oil flows have been found in the basin, highlighting its good petroleum potential. Many of these oils are heavy.Six oil samples from the Anan and ten from the Jirgalangtu Depressions have been subjected to routine geochemical analytical techniques in order to evaluate the origins. The methods used include gas chromatography of the saturated and aromatic hydrocarbon fractions, gas-chromatography-mass-spectrometry of the saturated hydrocarbon fraction and stable carbon isotope analyses. The trace metal elements of the biodegraded oils from the Jirgalangtu Depression were also analysed by atomic absorption spectroscopy.Two types of heavy oils : primary and biodegraded were identified on the basis of these data. The former includes both immature and mature heavy oils. A filtering-and-spill process was proposed to explain the origin of primary mature heavy oils (or tar-mat) in the Anan Depression. The biodegraded oils from the Jirgalangtu Depression were ranked and classified in terms of the degree of biodegradation, using a series of geochemical parameters based on the gas chromatographic concentrations and biomarker fingerprints of gas-chromatography-mass-spectrometry of the saturated hydrocarbon fraction. The relationship between oil saturation and porosity indicates that the heavy oils in the Jirgalangtu Depression were biodegraded after they accumulated.  相似文献   
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