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排序方式: 共有1503条查询结果,搜索用时 31 毫秒
931.
Gross ecosystem product (GEP) is the gross value of all ecosystem products and services provided by ecosystems for human society. In practice, GEP measures the ecosystems' contributions to human well-being and constitutes one of the core issues in the construction of ecological civilization systems. Currently, GEP accounting faces a series of problems, such as the inconsistency of accounting subjects and a lack of accounting standards, the result of which is the non-reproducibility and weak applicability of accounting results. In this paper, mainstream models for ecosystem service valuation are summarized in a systematic manner. On this basis, eight basic principles are established for screening accounting indicators: biological productivity, human benefits, production territoriality, current increment, actual effectiveness, physical metrizability, data availability, and harmlessness. Next, a series of ecosystem service subjects are identified that need to be excluded from accounting, and the detailed reasons for their exclusion are presented. Finally, three ideas for improving GEP accounting are offered from the perspectives of the relationship between biological production and human production, the circulation-transport relationship and spatial differences, and harms to the ecosystem carrying capacity. The purpose is to provide positive considerations aimed at promoting the socio-economic applications of accounting and to contribute to the scientific quantification of the values of ecological products.  相似文献   
932.
牛翠祎 《地质与勘探》2014,50(Z1):1274-1281
本文以全国金矿矿产资源潜力评价成果为基础,从我部金矿勘查、利用情况对我国黄金矿产的资源现状进行了综合分析,总结了我国基础地质和矿产勘查的地质工作程度和近年来地质勘查进展,通过与国外勘查技术及勘查现状的对比分析,结合矿床发现的规律,分析了我国黄金资源潜力,为我国黄金矿产资源勘查工作部署提出了参考性建议。  相似文献   
933.
宣德环礁作为我国南海诸岛礁开发利用程度最高的岛礁之一, 其周围海域地质灾害对岛礁基础工程建设及人类活动具有重大危害。为适应南海岛礁可持续发展的需要, 文章采用广州海洋地质调查局2018年采集的单道地震数据, 对宣德环礁东部斜坡带海域灾害地质因素进行综合解释和分析。结果表明, 研究区主要发育有海底滑坡、海底陡坎和断层3类地质灾害。海底滑坡是研究区主要灾害地质因素, 规模大小不一, 海底陡坎和断层为次要地质灾害。海底陡坎根据成因可分为礁体陡坎和滑坡陡坎, 礁体陡坎为礁盘形成过程中受海平面上升控制形成, 滑坡陡坎为海底滑坡导致。通过分析认为陡峭的地形和峡谷水道的侵蚀搬运作用是研究区地质灾害发育的主控因素。这些地质灾害对海洋工程建设及管线铺设均有不利的影响, 应尽量避开。  相似文献   
934.
This paper presents a development of the extended Cellular Automata (CA), based on relational databases(RDB), to model dynamic interactions among spatial objects. The integration of Geographical Information System (GIS)and CA has the great advantage of simulating geographical processes. But standard CA has some restrictions in cellularshape and neighbourheod and neighbour rules, which restrict the CA‘s ability to simulate complex, real world environ-ments. This paper discusses a cell‘‘s spatial relation based on the spatial object‘s geometrical and non-geometrical characteris-tics, and extends the cell‘‘ s neighbour definition, and considers that the cell‘ s neighbour lies in the forms of not only spa-tial adjacency but also attribute correlation. This paper then puts forward that spatial relations between two different ceilscan be divided into three types, including spatial adjacency, neighbourheod and complicated separation. Based on tradition-al ideas, it is impossible to settle CA‘‘s restrictions completely. RDB-based CA is an academic experiment, in whichsome fields are designed to describe the essential information needed to define and select a cell‘‘s neighbour. The cultureinnovation diffusion system has multiple forms of space diffusion and inherited characteristics that the RDB-based CA iscapable of simulating more effectively. Finally this paper details a successful case study on the diffusion of fashion weartrends. Compared to the original CA, the RDB-based CA is a more natural and efficient representation of human knowl-edge over space, and is an effective tool in simulating complex systems that have multiple forms of spatial diffusion.  相似文献   
935.
通过对栖霞地区蓬莱群进行详细的生物地层工作,除采集到大量微古植物化石外,未发现任何无脊椎动物化石。因此,前人在该区蓬莱群中采到的所谓“腕足类”和“双壳类”化石应予否定。本文重新肯定了栖霞地区蓬莱群的时代属震旦纪.  相似文献   
936.
937.
Alpha-glucosidase inhibitors were screened from organic solvent extracts of macroalgae by a spectrophotometrical method with p-nitrophenyl-D-glucopyranosidase as the substrate. The result indicates that orgarlic crude extracts from some macroalgae such as Rhodomela confervoides (Huds.) Silva, Gracilaria textorii(Suringar) DeToni, Plocamium telfairiae Harv., Dictyopteris divaricata (Okam.) Okam, Ulval pertusa and Enteromorpha intestinalis (L.) Link et al. show strong inhibitory activity of alpha-glucosidase at concentration of 79.6 μg/ml.  相似文献   
938.
Soil organic carbon (SOC) was considered to be a key index in evaluation of soil degradation and soil C sequestration. To discuss the spatial-temporal dynamics of SOC in arable layer in reversed desertification area, a case study was conducted in Yulin City, Shaanxi Province, China. Data of SOC were based on general soil survey in 1982 and repeated soil sampling in 2003. Soil organic carbon content (SOCC) was determined by K2Cr3O2-FeSO4 titration method, and soil organic carbon density (SOCD) was calculated by arithmetic average and area weighted average method, respectively. On average, SOCC and SOCD of the arable layer in the study area from 1982 to 2003 had increased 0.5 Ig/kg and 0.16kg/m2, respectively. Considering main soil types, the widest distributed Arid-Sandic Entisols had lowest values and increments of SOCC and SOCD during the study period; while the second widest Los-Orthic Entisols had higher values and increments of SOCC and SOCD, compared to the mean values of the whole region. The results indicated that reversed desertification process was due to the modification of land use and management practices, such as natural vegetation recovery, planting grass, turning arable land to grassland, and soil and water conservation etc., which can improve SOCC and SOCD and thus enhance soil C sequestration.  相似文献   
939.
牛晓露  冯光英  刘飞  杨经绥 《地质学报》2022,96(8):2705-2724
板内玄武岩通常具有复杂的成分组成和成因过程。海南岛北部(简称“琼北”)自渐新世始逐渐发育了大量板内玄武岩,岩性跨度大,从石英拉斑玄武岩到橄榄拉斑玄武岩,再到碱性橄榄玄武岩和碧玄岩均有分布。对琼北晚新生代玄武岩虽已开展了广泛的研究,但“琼北晚新生代玄武岩的成分随时间演化规律”这一问题却未引起足够的关注。本文从晚更新世道堂组橄榄玄武岩入手,对其开展了细致的岩石学、矿物学和主微量及Sr- Nd- Pb同位素地球化学的研究;并结合文献中琼北其他时代(组)玄武岩的数据,阐述了琼北晚新生代玄武岩成分随时间演化的规律并对其成因进行了探讨。研究发现,自中—上新世到更新世再到全新世,琼北晚新生代玄武岩呈现从碱性玄武岩过渡到拉斑玄武岩再突变到碱性—强碱性系列的演化规律;中—上新世到更新世这一时期的碱性玄武岩和拉斑玄武岩可能形成于石榴子石二辉橄榄岩由低到高程度的部分熔融作用,而全新世碱性岩则更可能形成于石榴子石辉石岩的部分熔融。琼北晚新生代玄武岩的Sr- Nd- Pb同位素组成揭示其源区地幔以PREMA端元为主,但经历了来自古老陆壳的沉积物不同程度的改造作用。采用“海南地幔柱”模型可以较好地解释琼北晚新生代玄武岩的复杂组成和成因。  相似文献   
940.
设计并实现一款TJ-2型体积式应变仪故障检测装置。经测试,该装置可实现体应变仪主机和探头的分离检测,快速锁定故障源,提升仪器维修效率。  相似文献   
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