首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   60篇
  免费   3篇
  国内免费   4篇
测绘学   1篇
大气科学   3篇
地球物理   8篇
地质学   24篇
海洋学   22篇
天文学   5篇
自然地理   4篇
  2022年   1篇
  2021年   1篇
  2019年   3篇
  2018年   8篇
  2017年   3篇
  2016年   1篇
  2015年   1篇
  2014年   1篇
  2013年   5篇
  2012年   3篇
  2011年   2篇
  2010年   4篇
  2009年   3篇
  2008年   3篇
  2007年   6篇
  2006年   2篇
  2005年   7篇
  2004年   1篇
  2003年   1篇
  2002年   3篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1997年   1篇
  1991年   1篇
  1988年   1篇
  1986年   1篇
排序方式: 共有67条查询结果,搜索用时 15 毫秒
51.
In order to determine the conditions of mineral formation, a suite of sodalite syenite samples was investigated from the differentiated complex and in part from the eudialyte lujavrite complex of the Lovozero alkaline massif. The compositions of major and accessory minerals were analyzed using an electron microprobe. Various mineral geothermometers (Bt-Cpx, Amph-Cpx, and Amph-Bt) were applied to estimate the temperature of formation of clinopyroxene-bearing assemblages from the sodalite syenites. The temperature varied from ~990 to 595–630°C, which reflects various stages of crystallization. The temperatures of formation of sodalite assemblages were estimated from the compositions of coexisting sodalite phases as 625–530°C and appeared to be in good agreement with estimates obtained by other mineral geothermometers. Based on the data on the composition and crystallization temperature of sodalites, the minimum concentration of salts (NaCl and Na2SO4) in the mineral-forming fluid was estimated as 10–20 wt % NaCl eq. for the two-sodalite assemblages and 1.5–3.0 wt % NaCl eq. for the nosean-bearing assemblages. The molar fraction of sulfur in the fluid was also estimated: 0.02 for the two-sodalite assemblages and 0.04–0.27 for the nosean-bearing assemblages.  相似文献   
52.
Korea’s domestic emissions trading scheme commenced in January 2015. It targeted mainly industrial and power sectors, and compelled companies to transform how they manage energy efficiency and mitigate GHGs. This study sets out to explore how Korean companies evaluated their allocation position and engaged in emissions trading in the first compliance period, and to identify their views on trading barriers and policy expectations at the start of emissions trading. Questionnaire surveys and on-site interviews targeting Korean companies under the Korean emissions trading scheme were conducted at the start of operations (February to March 2015) and after the first compliance year (May 2016), respectively. Actual operation results are observed and compared with the survey findings. This study extrapolates implications for policy and presents suggestions for the government and the target companies in terms of how to improve the current emissions trading scheme in order to further stimulate emissions trading.

POLICY RELEVANCE

This study attempts to bridge the gap between companies and government policy in operating the domestic emission trading scheme in Korea. Empirical results, based on analysis of company-level data, reveal how businesses perceive K-ETS and how this relates to the operating results, which saw only limited trading of surplus emissions taking place in the early phase. Key barriers to active trading identified in the study include supply–demand imbalance, policy uncertainty and lack of preparedness of companies over carbon pricing. These barriers could be addressed by improved transparency of allowance allocation methods, possibly restricting carry-over of surplus allowances, ending policy uncertainty and providing more information to companies that can support companies’ policy understanding of the carbon pricing based on the market mechanism. Targeted companies should proactively participate in emissions trading in the early phase, in order to learn from it and prepare for the future introduction of auctioning.  相似文献   

53.
Seasonal Variation of the Cheju Warm Current in the Northern East China Sea   总被引:1,自引:1,他引:1  
The Cheju Warm Current has been defined as a mean current that rounds Cheju-do clockwise, transporting warm and saline water to the western coastal area of Cheju-do and into the Cheju Strait in the northern East China Sea (Lie et al., 1998). Seasonal variation of the Cheju Warm Current and its relevant hydrographic structures were examined by analyzing CTD data and trajectories of satellite-tracked drifters. Analysis of a combined data set of CTD and drifters confirms the year-round existence of the Cheju Warm Current west of Cheju-do and in the Cheju Strait, with current speeds of 5 to 40 cm/s. Saline waters transported by the Cheju Warm Current are classified Cheju Warm Current water for water of salinity greater than 34.0 psu and modified Cheju Warm Current for water having salinity of 33.5–34.0 psu. In winter, Cheju Warm Current water appears in a relatively large area west of Cheju-do, bounded by a strong thermohaline front formed in a "" shape. In summer and autumn, the Cheju Warm Current water appears only in the lower layer, retreating to the western coastal area of Cheju-do in summer and to the eastern coastal area sometimes in autumn. The Cheju Warm Current is found to flow in the western channel of the Korea/Tsushima Strait after passing through the Cheju Strait, contributing significantly to the Tsushima Warm Current.  相似文献   
54.
Doklady Earth Sciences - In connection with the problem of the possibility of metamorphogenic formation of ore deposits, experimental modeling of the transport of components of sulfide ores in the...  相似文献   
55.
The static modeling and dynamic simulation are essential and critical processes in petroleum exploration and development. In this study, lithofacies models for Wabiskaw Member in Athabasca, Canada are generated by multipoint statistics(MPS) and then compared with the models built by sequential indicator simulation(SIS). Three training images(Tls) are selected from modern depositional environments;the Orinoco River Delta estuary, Cobequid bay-Salmon River estuary, and Danube River delta environment. In order to validate lithofacies models, average and variance of similarity in lithofacies are calculated through random and zonal blind-well tests.In random six-blind-well test, similarity average of MPS models is higher than that of SIS model. The Salmon MPS model closely resembles facies pattern of Wabiskaw Member in subsurface. Zonal blind-well tests show that successful lithofacies modeling for transitional depositional setting requires additional or proper zonation information on horizontal variation, vertical proportion, and secondary data.As Wabiskaw Member is frontier oilsands lease, it is impossible to evaluate the economics from production data or dynamic simulation. In this study, a dynamic steam assisted gravity drainage(SAGD)performance indicator(SPIDER) on the basis of reservoir characteristics is calculated to build 3 D reservoir model for the evaluation of the SAGD feasibility in Wabiskaw Member. SPIDER depends on reservoir properties, economic limit of steam-oil ratio, and bitumen price. Reservoir properties like porosity,permeability, and water saturation are measured from 13 cores and calculated from 201 well-logs. Three dimensional volumes of reservoir properties are constructed mostly based on relationships among properties. Finally, net present value(NPV) volume can be built by equation relating NPV and SPIDER. The economic area exceeding criterion of US$ 10,000 is identified, and the ranges of reservoir properties are estimated. NPV-volume-generation workflow from reservoir parameter to static model provides costand time-effective method to evaluate the oilsands SAGD project.  相似文献   
56.
We present observations of the extended dust structures near the orbits of three short-period comets: 2P/Encke, 22P/Kopff, and 65P/Gunn. The dust trails were originally discovered by the Infrared Astronomical Satellite (IRAS). Our observations were made using wide-field optical CCD cameras on the University of Hawaii 2.24-m telescope, the Canada-France-Hawaii 3.6-m telescope, and the Kiso 1.05-m Schmidt telescope. We compared the observed images with models and found that the extended structures seen around 2P/Encke and 22P/Kopff before perihelion passage were most likely “dust trails,” whereas images taken after perihelion passage show a high contamination by recently released particles (i.e., particles in Neck-Line structures are visible). We could not confirm the existence of a dust trail from 65P/Gunn within the field of view of the camera used. The effective sizes of the particles responsible for the scattered light were estimated at 1-100 mm (2P/Encke), 1-10 mm (22P/Kopff), and 100 μm-1 mm (65P/Gunn), respectively, which is consistent with previous studies of dust trails made with infrared space telescopes and optical telescopes. We evaluated the mass loss rates of these comets, averaged over their orbits, as reaching (2P/Encke), (22P/Kopff), and (65P/Gunn). These values are consistent with previous work. Therefore, the total amount of material ejected from these three comets is , which would contribute a considerable fraction of the lost within 1 AU that needs to be replaced if the zodiacal cloud is to be maintained in a steady state. We also found that the particles in the dust structures are significantly redder than the Sun and the zodiacal light, and might be redder than the average short-period comet nuclei. Specifically, the reflectivity gradients of 2P/Encke, 22P/Kopff, and 65P/Gunn are 13±7 (% 103 Å−1), 20±5 (% 103 Å−1), and 15±4 (% 103 Å−1), respectively. We examined the change in color with distance from the nucleus. No clear correlation was detected for 2P/Encke or 22P/Kopff to an accuracy of 3-11%, while the 65P/Gunn tail did show color variation, becoming redder with increasing distance from the nucleus. This dark red material, consisting of particles of sand-cobble size, has marginally escaped from the nuclei and will evolve into finer-grained interplanetary dust particles after subsequent collisions.  相似文献   
57.
We conducted testing to determine whether stipe length is a useful indicator of reproductive maturity in the kelp Ecklonia cava, a species that plays a pivotal role in ecosystem functioning and services in subtidal areas. Approximately 100 sporophytes with stipes of various lengths were collected during the fertile period (July–November, 2013). We investigated the relationships between stipe length and other morphological characteristics to determine whether stipe length could indicate the age of reproductive maturity. Primary blade length, longest blade length, thallus height, and total length showed significant relationships with stipe length. The length of the primary and longest blades gradually declined as stipe length increased above 125 mm. Zoosporangial sori were found on the blades of more than 70% of individuals with stipes longer than 125 mm, but on only 8% of individuals with stipes less than 125 mm long. Stipe length therefore seems to be an acceptable proxy for reproductive maturity. Another factor to consider, however, is that all specimens with zoosporangial sori, regardless of stipe length, had a dry weight of 80 g or more; thus, individual biomass may also be an important parameter influencing the initiation of reproduction.  相似文献   
58.
日本海的末次盛冰期   总被引:1,自引:0,他引:1  
日本海末次盛冰期的沉积层几乎都是以交替出现的深色纹层、浅色纹层状和均质沉积物为特征。根据日本海中部和南部两个岩心记录的末次盛冰期的沉积特征和表层海水温度变化,讨论了低海平面时期东亚季风对日本海沉积环境的控制作用。24.2~17.8 cal.kaBP,日本海南部纹层沉积的分布均对应了夏季风的相对增强,表明季风降水输入是引起该时期日本海底层水含氧量变化的主要原因。在夏季风的控制下,低盐富营养的东海沿岸水的强弱变化使冲绳海槽北部表层海水温度也在24.2~17.8 cal.kaBP期间出现低值并剧烈变化。30~24.2和17.8~15 cal.kaBP,受增强的冬季风(夏季风减弱)影响,日本海水体的流通性较强,底层水溶解氧含量相对较高。对23~17.5 cal.kaBP日本海的表层海水温度出现异常高值的原因存在很多争论,一般认为是由于季风降雨输入量大于蒸发量、表层水盐度普遍降低、水体出现密度分层、水层间的垂直交换受到限制所致。  相似文献   
59.
Doklady Earth Sciences - The solubility of phenakite in aluminosilicate melts of various alkalinity was studied experimentally at T = 1000°C and P = 1 kbar in dry conditions and in the...  相似文献   
60.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号