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   249篇
  免费   9篇
  国内免费   30篇
测绘学   9篇
大气科学   11篇
地球物理   57篇
地质学   124篇
海洋学   38篇
综合类   7篇
自然地理   42篇
  2022年   1篇
  2021年   2篇
  2020年   4篇
  2019年   9篇
  2018年   7篇
  2017年   13篇
  2016年   16篇
  2015年   4篇
  2014年   9篇
  2013年   14篇
  2012年   6篇
  2011年   8篇
  2010年   8篇
  2009年   18篇
  2008年   16篇
  2007年   22篇
  2006年   24篇
  2005年   24篇
  2004年   16篇
  2003年   14篇
  2002年   12篇
  2001年   10篇
  2000年   8篇
  1999年   5篇
  1998年   7篇
  1997年   3篇
  1996年   2篇
  1995年   1篇
  1994年   3篇
  1993年   1篇
  1992年   1篇
排序方式: 共有288条查询结果,搜索用时 15 毫秒
131.
《Urban geography》2013,34(8):1163-1191
Although theoretical studies have contended that telecommuting could cause residential relocation to peripheral areas, empirical evidence regarding this argument is scant and inconclusive. Moreover, previous studies have given little consideration to telecommuters' job locations. Using data from the 2006 Seoul Metropolitan Area Household Travel Survey, this study investigates the relationships between telecommuting and residential location, considering job location. Regression results suggest that telecommuter households are indeed more likely to reside in outlying areas, consistent with theory. However, this does not necessarily mean that telecommuting facilitates living in outlying areas, nor, conversely, that long commutes stimulate telecommuting: causality cannot be established with these data. But contrary to both hypotheses, the result partially arises from the fact that firms allowing telecommuting also tend to be located in peripheral areas, with telecommuters having shorter commute distances compared to office workers. Consequently, issues regarding telesprawl need to be discussed considering the distribution of telecommuting-conducive occupations.  相似文献   
132.
Gwang H.  Lee  Dae C.  Kim  Mi K.  Park  Soo C.  Park  Han J.  Kim  Hyeong T.  Jou  Boo K.  Khim 《Island Arc》2010,19(1):71-85
The Korea Strait shelf mud (KSSM) (Nakdong River subaqueous delta) is the most conspicuous Holocene sedimentary feature in the inner shelf off southeast Korea. Analysis of multi-channel sparker profiles and 14C ages of sediment cores reveals that the KSSM consists of three seismic units at the depocenter (>60 m thick): (i) the thin transgressive bottom (> ca 8000 cal bp ); (ii) thick (>40 m) obliquely progradational middle ( ca 8000– ca 2600 cal bp ); and (iii) thin transgressive top ( ca 2600 cal bp –present) units. The relative base level, predicted from the internal reflection pattern of the KSSM, remained significantly deeper (up to >70 m) than global sealevel during much of the Holocene. The apparent gradual drop (∼20 m) of the relative base level during the deposition of the middle unit, followed by a rise, further suggests that base level does not conform to sealevel and is more sensitive than the relative sealevel is to the local oceanographic regime and processes.  相似文献   
133.
韩国农业和渔业遗产系统的保护与管理(英文)   总被引:2,自引:0,他引:2  
农业和渔业社区,除食物生产这一基本功能之外,其生物多样性及历史、文化功能正在日益引起人们的兴趣。一直以来,农业遗产系统及韩国重要农业遗产系统的发展都是大韩国民国中央政府的关键目标。在农业遗产系统发展的大前提下,一旦遗产受到损坏,假定其恢复及技术转让变得不可能,则需要开展针对其保护管理的详细研究。作者分析了几个由地方政府上报的韩国重要农业遗产系统实践案例,主要目标是确认每个案例的独特性,同时考量遗产性质、遗产面临的威胁,以及当前保护措施。作者发现,最常见的威胁是,由于农业环境的变化,维护遗产的种群在减少。相应地,每处遗产地都把大力发展当地旅游活动作为解决措施,但当前围绕旅游业制定的管理计划可能导致遗产地受到进一步的损害。作者根据分析,提出未来规划三大重要方面:加深对遗产的理解和认识;要有足够的空间来维护遗产的特性;要有新的产业计划以维持生产活动。这些建议将确保遗产保护和自然环境保护,以及通过生物多样性来确保农业和渔业社区获得有益养护。  相似文献   
134.
This study assessed the levels of marine debris pollution and identified its main sources in Korea. The surveys were bimonthly conducted by NGO leaders and volunteers on 20 beaches from March 2008 to November 2009. The quantities of marine debris were estimated at 480.9 (±267.7) count  100 m−1 for number, 86.5 (±78.6) kg  100 m−1 for weight, and 0.48 (±0.38) m3  100 m−1 for volume. The level of marine debris pollution on the Korean beaches was comparable to that in the coastal areas of the North Atlantic ocean and South Africa. Plastics and styrofoam occupied the majority of debris composition in terms of number (66.7%) and volume (62.3%). The main sources of debris were fishing activities including commercial fisheries and marine aquaculture (51.3%). Especially styrofoam buoy from aquaculture was the biggest contributor to marine debris pollution on these beaches.  相似文献   
135.
Fogs observed over Incheon international airport (IIA) in the west coast of Korea from January 2002 to August 2006 are classified into categories of coastal fog, cold sea fog, and warm sea fog based on the areal extent of the fogs and the difference between the air temperature (T) and the SST, i.e., cold sea fog if TSST = T-SST>0oC and warm sea fog if TSST <0oC. The numbers of coastal, cold, and warm sea fog cases are 64, 26, and 9. Coastal fogs form most frequently in winter, while cold sea fogs occur mostly in summer and warm sea fogs are observed from January to May but not in November and December. On average the air gets colder by 1.6oC during the three hours leading up to the coastal fog formation, and an additional cooling of 1.1oC occurs during the fog. The change in the dew point temperature (Td) is minimal except during the fog (0.6oC). Decreases in T for the cold and warm sea fogs are relatively smaller. The average Td is higher than SST during the cold sea fog periods but this Td is more than 4oC higher than that for the corresponding non-fog days, suggesting that cold sea fogs be formed by the cooling of already humid air (i.e., Td>SST). Increases of Td are significant during the warm sea fog periods (1.4oC), implying that efficient moisture supply is essential to warm sea fog formation. Four major synoptic patterns are identified in association with the observed fogs. The most frequent is a north Pacific high that accounts for 38% of cases. Surface or upper inversions are present in 77%, 69%, and 81% of the fog periods for coastal, cold, and warm sea fogs, respectively.  相似文献   
136.
The surface and upper-level features associated with a sharp drop of wintertime daily temperature over South Korea is investigated in this study. This sharp drop in daily temperature is called a cold surge and is one of the most hazardous weather phenomena in East Asian winters. An upper-level baroclinic wave of 60°wavelength propagating eastward at a phase speed of 12°longitude per day across the continent of northern China from the west of Lake Baikal toward the eastern coast of China causes the outbreak of cold air over South Korea. The cooling associated with the upper-level baroclinic wave is found at all altitudes under the geopotential height-fall center near the tropopause. The development in the ridge seems to derive the early evolution of the eastward-propagating sinusoidal wave, whereas the trough is connected directly with the tropospheric temperature-drop. An enhancement of the wintertime East Asian jet stream after the outbreak of a cold surge is a response to the steep temperature gradient associated with the developing baroclinic wave.  相似文献   
137.
The East Sea (Japan Sea) is a semi-enclosed back-arc basin that is thought to preserve a significant record of tectonic evolution and paleo-climatic changes of Eastern Asia during the Neogene. We use here 2-D regional multi-channel seismic reflection profiles and borehole data from Expedition 346 of the Integrated Ocean Drilling Program (IODP) to provide new constraints on the geological history of the Eastern South Korea Plateau (ESKP). The ESKP represents a structurally-complex basement high in the southwestern East Sea which formed during rifting of the back-arc basin. Our new observations show that the ESKP is composed of numerous horsts and grabens controlled by NE-trending normal faults. The acoustic basement is blanketed by Oligocene to recent sediments that have preferentially accumulated in topographic lows (up to 1.5 km thick) and have been cored during Expedition 346 at Site U1430 close to the southern margin of the ESKP. Seismic profiles in the ESKP reveal three units separated by regional unconformities. These seismic units closely correspond to IODP lithostratigraphic units defined at Site U1430, where biostratigraphic data can be used to constrain the timing of three main evolutionary stages of the ESKP. Stage 1 was related to rifting in the late Oligocene and middle Miocene, terminated by a regional uplift leading to an erosional phase in the middle Miocene. Stage 2 was associated with subsidence in the middle and late Miocene and uplift and accompanying erosion or non-deposition in the latest late Miocene. Stage 3 (Pliocene to present) recorded overall uniform hemipelagic-pelagic subsidence of the ESKP with short-lived tectonically-induced uplifts in the late middle Miocene and latest Miocene-early Pliocene. The three stages of evolution of the ESKP closely correlate to sedimentary changes since the Oligocene and suggest a direct control of regional/local tectonics on sedimentation patterns in the southwestern East Sea, with secondary influence of regional climatic and paleo-oceanographic processes.  相似文献   
138.
The purpose of this article is to analyze the legal status of fisheries in the East China Sea (ECS) pursuant to these fisheries agreements, focusing on the legal issues of the Current Fishing Pattern Zone (CFPZ) which is provided for in the Fisheries Agreement between Korea and China. The CFPZ is a zone or area in which Korean and Chinese fishing patterns that existed before the agreement are respected. Although the legal status of fisheries in the CFPZ appears to be very simple, it is in fact very complex due to the overlapping jurisdictions of Korea, China and Japan. Therefore, the fisheries regime is rather vulnerable with the possibility of increasing legal conflicts. However, it is noteworthy that fisheries conflicts come up rarely in these relevant waters. This article explores the bilateral fisheries agreements and EEZ laws of the respective states, and thereafter deals with the legal issues that arise in the execution of these agreements regarding the area of overlapping waters.  相似文献   
139.
Yun-Ho Song  Man Sik Choi   《Chemical Geology》2009,266(3-4):337-351
To investigate the distribution pattern and controlling factors of rare earth elements (REEs) in riverine sediments, river mouth sediments were collected at five geographically different rivers around the Yellow Sea. Two- (1 M HCl leached and residual fractions) and five-step sequential extraction schemes (the SEDEX method) were applied to size-separated sediments < 20 µm. For the total REE composition, patterns normalized relative to the upper continental crust (UCC) showed light REE (LREE) and middle (MREE) enrichments in the Korean river sediments and MREE enrichment in the Chinese river sediments. LREE and MREE enrichments in 1 M HCl leached fractions played a major role in the distribution patterns of the total compositions in all the river sediments. About half of LREE enrichment in Korean river sediments was explained by the residual fraction. Comparison of the REE composition with major elements (Al, Fe, Ca, P) in each fraction of the SEDEX scheme revealed that MREE enrichment could be explained by reactive iron minerals, including goethite and hematite, although REE/Fe ratios showed different trends among the rivers due to different major REE-host iron minerals. After extracting reactive irons, authigenic phosphate, and carbonate, the sequential 1 M HCl fraction indicated that LREE enrichment in Korean river sediments may have originated from clay minerals, such as chlorite. These observations suggest that LREE enrichment may be a good tracer, while MREE enrichment should be used cautiously considering diagenetic modification, when using the REE composition to identify the sources of terrestrial materials.  相似文献   
140.
Gold mineralization of the Seolhwa mine occurs in a single stage of massive quartz veins which filled the north‐east‐trending fault shear zones in the Jurassic granitoid of 161 Ma within the Gyeonggi Massif. The vein quartz contains three main types of fluid inclusions at 25°C: (i) aqueous type I inclusions (0–15 wt.% NaCl) containing small amounts of CO2; (ii) gas‐rich (more than 70 vol. %), vapor‐homogenizing, aqueous type II inclusions; and (iii) low‐salinity (less than 5 wt.% NaCl), liquid CO2‐bearing, type III inclusions. The H2O‐CO2‐CH4‐N2‐NaCl inclusions represent immiscible fluids trapped earlier along the solvus curve in the temperature range 250–430°C at pressures of ~1 kb. Detailed fluid inclusion chronologies suggest a progressive decrease in pressure during the mineralization. Aqueous inclusion fluids represent either later fluids evolved through extensive fluid unmixing from a homogeneous H2O‐CO2‐CH4‐N2‐NaCl fluid due to decreases in temperature and pressure, or the influence of deep circulated meteoric waters. Initial fluids were homogeneous H2O‐CO2‐CH4‐N2‐NaCl fluids as follows: 250° to 430°C, 16–62 mol% CO2, 5–14 mol% CH4, 0.06–0.31 mol% N2 and salinities of 0.4–4.9 wt.% NaCl. The T‐X data for the Seolhwa mine suggest that the hydrothermal system has been probably located nearer to the granitic melt, which facilitated the CH4 formation and resulted in a reduced fluid state indicated by the predominance of pyrrhotite. Measured and calculated isotopic compositions of the hydrothermal fluids [δ18O = 5.3–6.5‰; δD =?69 to ?84‰] provide evidence of the CH4‐H2O equilibria and further indicate that the auriferous fluids were magmatically derived. Both the dominance of δ34S values of sulfides close to the meteoric reference (?0.6–1.4‰; δ34SΣS values of 0.3–1.1‰) and the available δ13C data (?4‰) are consistent with their deep igneous source. The Seolhwa mine was probably formed by extensive fracturing and veining due to the thermal expansion of water derived from the Jurassic granitoid melt.  相似文献   
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