全文获取类型
收费全文 | 375篇 |
免费 | 12篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 39篇 |
地球物理 | 111篇 |
地质学 | 114篇 |
海洋学 | 89篇 |
天文学 | 12篇 |
综合类 | 6篇 |
自然地理 | 12篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 16篇 |
2017年 | 15篇 |
2016年 | 26篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 30篇 |
2012年 | 24篇 |
2011年 | 25篇 |
2010年 | 26篇 |
2009年 | 19篇 |
2008年 | 23篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 22篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1998年 | 5篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1992年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1970年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1951年 | 4篇 |
1950年 | 1篇 |
1949年 | 2篇 |
1948年 | 3篇 |
排序方式: 共有396条查询结果,搜索用时 218 毫秒
71.
72.
73.
Abu Affan Joon-Baek Lee Jun -Teck Kim Young -Chan Choi Jong -Man Kim Jung -Goo Myoung 《Ocean Science Journal》2007,42(2):117-127
The dynamics of phytoplankton abundance with seasonal variation in physicochemical conditions were investigated monthly at
10 stations around the Chagwi-do off the west coast of Jeju Island, Korea, including inshore, middle shore, and offshore in
the marine ranching area from September 2004 to November 2005. Water temperature varied from 12.1 to 28.9°C (average 18.8°C),
and salinity from 28.9 to 34.9 psu (average 33.7 psu). The chlorophyll a concentration was 0.02-2.05 μg L1 (average 0.70 μg L1), and the maximum concentration occurred in the bottom layer in April. A total of 294 phytoplankton species belonging to
10 families was identified: 182 Bacillariophyceae, 52 Dinophyceae, 9 Chlorophyceae, 12 Cryptophyceae, 6 Chrysophyceae, 4 Dictyophyceae,
13 Euglenophyceae, 6 Prymnesiophyceae, 5 Prasinophyceae, and 5 Raphidophyceae. The standing crop was 2.21-48.69x104 cells L1 (average 9.23x 104 cells L1), and the maximum occurred in the bottom layer in April. Diatoms were most abundant throughout the year, followed by dinoflagellates
and phytoflagellates. A phytoplankton bloom occurred twice: once in spring, peaking in April, and once in autumn, peaking
in November. The spring bloom was represented by fourChaetoceros species andSkeletonema costatum; each contributed 10–20% of the total phytoplankton abundance. The autumn bloom comprised dinoflagellates, diatoms, and phytoflagellates,
of which dinoflagellates were predominant.Gymnodinium conicum, Prorocentrum micans, andP. triestinum each contributed over 10% of the total phytoplankton abundance. 相似文献
74.
Hoi-Soo Jung Young-Tak Ko Sang-Bum Chi Jai-Woon Moon 《Marine Georesources & Geotechnology》2001,19(3):167-180
Seafloor morphology and ferromanganese nodule occurrence were studied using a multibeam side scan sonar (SeaBeam, 2000) and a deep-sea camera system in the Korea Deep-sea Environmental Study (KODES) area, northeast equatorial Pacific. Seafloor morphology and nodule abundance are highly variable even in this small study area. The NNE-SSW oriented hills are parallel and about 100-200 m high. Valleys are very flat-floored, while hilltops are rugged with depressions of tens of meters. Cliffs to about 100 m bound the valleys and the hills. The study area can be classified into three types based both on nodule occurrence and seafloor morphology, mostly G- and B-types and some M-type. G-type is characterized by high nodule abundance, ubiquitous bioturbation, and flat seafloor morphology, while B-type is characterized by irregular-shaped nodules, variable nodule abundance, occurrence of giant nodules and sediment lumps, rugged bottom morphology with depressions, and white calcareous surface sediments. Medium nodule abundance and a generally flat seafloor characterize M-type. G-type occurs mostly in the valley regions, while B-type is on the hilltop areas. M-type is located between the hilltop and the valley. Tectonic movement of the Pacific plate resulted in the elongated abyssal hills and cliffs. The rugged morphology on hilltops resulted from erosion and redistribution of surface siliceous sediments on hilltops by bottom currents, outcropping of underlying calcareous sediments, and dissolution of the carbonate sediments by corrosive bottom water undersaturated with CaCO 3 . Sediment eroded from the hills, which is relatively young and organic-rich, is deposited in the valleys, and diagenetic metal supply to manganese nodules in the valley area is more active than on the hills. We suggest that tectonic movement ultimately constrains morphology, surface sediment facies, bottom currents and sediment redistribution, bioturbation, thickness of the sedimentary layer, and other conditions, which are all interrelated and control nodule occurrence. The best potential area for mining in the study area is the G-type valley zones with about 3-4 km width and NNW-SSE orientation. 相似文献
75.
Numerical flow analysis of single-stage ducted marine propulsor 总被引:1,自引:0,他引:1
The present work has solved 3D incompressible RANS equations on a rotating, non-orthogonal multi-blocked grid to efficiently analyze a ducted marine propulsor with rotor–stator interaction. To handle the interface boundary between a rotor and a stator, the sliding multi-block technique using the cubic spline interpolation and the bilinear interpolation was applied. To validate the present code, the flow of a single stage turbine flow was simulated. Time averaged pressure coefficients were compared with experiments and good agreements were obtained. After the code validation, the flowfield around a single-stage ducted marine propulsor having a single stage of rotor and stator was successfully simulated and the hydrodynamic performance coefficients were computed. 相似文献
76.
The geochemical and mineralogical characteristics of pre-Holocene core sediments from Haenam Bay, southwest coast of Korea,
were examined for post-depositional diagenetic changes and used to assess the provenance of fine-grained sediments in the
region. The geochemical and mineralogical compositions of the sediments vary very little with core depth (Holocene to pre-Holocene
age), except for the upper part of the pre-Holocene sedimentary layer. In this case, smectite and chlorite are depleted, presumably
due to intensive subaerial weathering and low pH conditions. Highly mobile elements (Ca, Mg, Na and K) were likely removed
with the breakdown of labile minerals, such as carbonate minerals, feldspar, and clay minerals, during subaerial exposure
of this layer, resulting in low weathering indices. In particular, the low smectite content (<5%) and low V/Al ratio (<13)
suggest that the Holocene and pre-Holocene sediments along the southwestern coast of Korea did not originate from mainland
China but rather mostly from the Korean Peninsula. This aspect has been a subject of debate since the mid-1970s. 相似文献
77.
The geochemical and mineralogical characteristics of pre-Holocene core sediments from Haenam Bay, southwest coast of Korea, were examined for post-depositional diagenetic changes and used to assess the provenance of fine-grained sediments in the region. The geochemical and mineralogical compositions of the sediments vary very little with core depth (Holocene to pre-Holocene age), except for the upper part of the pre-Holocene sedimentary layer. In this case, smectite and chlorite are depleted, presumably due to intensive subaerial weathering and low pH conditions. Highly mobile elements (Ca, Mg, Na and K) were likely removed with the breakdown of labile minerals, such as carbonate minerals, feldspar, and clay minerals, during subaerial exposure of this layer, resulting in low weathering indices. In particular, the low smectite content (<5%) and low V/Al ratio (<13) suggest that the Holocene and pre-Holocene sediments along the southwestern coast of Korea did not originate from mainland China but rather mostly from the Korean Peninsula. This aspect has been a subject of debate since the mid-1970s. 相似文献
78.
An analytical model with three sub-regions for m2 tide in the yellow sea and the East China Sea 总被引:1,自引:0,他引:1
In this study an analytical tide model of uniform width with three sub-regions is presented. The three-subregions model takes
into account step-like variations in depths in the direction of the channel as a way to examine the M2 tide of the East China Sea (ECS) as well as the Yellow Sea (YS). A modified Proudman radiation condition has been applied
at the northern open head, while the sea surface elevation is specified at the southern open boundary. It is seen that, due
to the presence of an abrupt change in depth, co-amplitude lines of the M2 tide are splitted to the east and west near the end of the ECS shelf region. Variations in depths, bottom friction and the
open head boundary conditions all contribute to the determination of formation of amphidromes as well as overall patterns
of M2 tidal distribution. It is seen that increasing water depth and bottom friction in the ECS shelf results in the westward shift
of the southern amphidrome. There is however no hint at all of the well-known degenerated tidal pattern being formed. It is
inferred that a lateral variation of water depth has to be somehow incorporated to represent the tidal patterns in ECS in
a realistic manner. Regarding the radiation factor introduced by Fang et al. (1991), use of a value larger than one, possibly
with a phase shift, appears to be a proper way of incorporating the reflected waves from the northern Yellow Sea (NYS). Key
words - analytical model, M2 tide, Kelvin wave, Yellow Sea, East China Sea 相似文献
79.
Hoi-Soo Jung Kap-Sik Jeong Yong-Shik Chu Sung-Hyun Park Ki-Hyune Kim 《Marine Georesources & Geotechnology》2001,19(3):181-195
Grain size and water content in box-core sediments from the Clarion-Clipperton fracture zone (C-C zone) in the northeast equatorial Pacific were analyzed in detail to understand the downcore variations across a hiatus between Quaternary and Tertiary layers. Grain-size distributions in the topmost core sediments show two modes: a coarse mode (peaked at 50 μm) and a fine mode (at 2-25 μm). The coarse mode disappears gradually with depth accompanied by the dissolution of siliceous fossil tests, whereas the fine mode coarsens due to the formation of authigenic minerals. Water content increases abruptly across a color boundary between an upper pale brown layer and a lower dark brown layer that is the hiatus between Quaternary and Tertiary layers. Abundant smectites and microvoid molds, which are created by the prolonged fossil dissolution in the underlying sediment, are attributed for the abrupt downcore variation of water content. Overall variations in grain size and water content in the topmost core sediments in the western C-C zone are possibly constrained by the dissolution of biogenic siliceous fossils. Variations in geotechnical properties related to these changes must be considered in the design of nodule collectors. 相似文献
80.
Benthic amphipod,Grandidierella japonica widely inhabits the Korean coastal waters and is developed as a standard test species for sediment toxicity tests. We exposedG . japonica to various pollutants including 4 kinds of inorganic metals (Ag, Cd, Cu and Hg), tributyltin [TBT], ammonia and 7 polycyclic
aromatic hydrocarbon (PAH) compounds (acenaphthene, chrysene, fluoranthene, fluorene, naphthalene, phenanthrene and pyrene)
to estimate the no observed effect concentration (NOEC) and the median lethal concentration (LC50) of each pollutant during
the 96-hour acute exposure. Among all tested pollutants, TBT was most toxic toG. japonica, and Hg was most toxic among inorganic metals. The toxicity of pyrene toG. japonica was greatest among PAH compounds, followed by fluoranthene, phenanathrene, acenaphthene, fluorene and naphthalene. The toxicity
of PAH compounds was closely related to their physico-chemical characteristics such as Kow and water solubility.G. japonica responded adequately to pollutant concentrations and exposure durations, and the sensitivity ofG. japonica to various inorganic and organic pollutants was generally comparable to other amphipods used as standard test species in
ecotoxicological studies, indicating this species can be applied in the assessment of environments polluted by various harmful
substances. 相似文献