全文获取类型
收费全文 | 122篇 |
免费 | 3篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 7篇 |
地球物理 | 20篇 |
地质学 | 28篇 |
海洋学 | 48篇 |
天文学 | 22篇 |
自然地理 | 4篇 |
出版年
2020年 | 3篇 |
2019年 | 2篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有130条查询结果,搜索用时 31 毫秒
81.
82.
The collapse of marginally Jeans-unstable primordial gas clouds in the presence of a UV radiation field is discussed. Assuming that the dynamical collapse proceeds approximately in an isothermal self-similar fashion, we investigate the thermal evolution of the collapsing central core until H2 cooling dominates photoheating and the temperature drops to below 104 K. Consequently, the mass of the cooled core is evaluated as M cool =3.6×106 M⊙ ( I 21 /1)−0.32 . This scale depends only on the incident UV intensity, and provides a lower limit to the mass of collapsed objects in the UV radiation field. 相似文献
83.
Masayuki Uesugi Motoo Ito Hikaru Yabuta Hiroshi Naraoka Fumio Kitajima Yoshinori Takano Hajime Mita Yoko Kebukawa Aiko Nakato Yuzuru Karouji 《Meteoritics & planetary science》2019,54(3):638-666
Carbonaceous materials in the sample catcher of the Hayabusa spacecraft were assigned as category 3 particles. We investigated the category 3 particles with a suite of in situ microanalytical methods. Possible contaminants collected from the cleanrooms of the spacecraft assembly and extraterrestrial sample curation center (ESCuC) were also analyzed in the same manner as category 3 particles for comparison. Our data were integrated with those of the preliminary examination team for category 3 particles. Possible origins for the category 3 particles include contamination before and after the operation of the Hayabusa spacecraft. 相似文献
84.
Putth Songsangjinda Osamu Matsuda Tamiji Yamamoto Narasimmalu Rajendran Hajime Maeda 《Journal of Oceanography》2000,56(2):223-231
The predominance of bivalves affects the cycle of materials in the coastal ecosystem. In the present study, the role of suspended oyster culture on the nitrogen cycle was demonstrated for the northern Hiroshima Bay. The nitrogen cycle was considered as two systems, (1) the primary production (PP) system and (2) the oyster culture (OC) system. The results show that about 26% of N productivity was supplied to process by cultured oysters in the OC system. This process varies seasonally due to the seasonal variations of PON, physiological activities and biomass of oysters. The N processing rates were found to be high in summer and low in winter. The biodeposition and excretion of N in the OC system are 3.0 and 2.1 ton N d–1, while the natural sedimentation rate and N regeneration in the PP system are 8.3 and 18.0 ton N d–1, which indicates that the PP system is a major system regenerating N in the water column. The release of total dissolved N from the bottom to the water column is about 8.3 ton N d–1. The amount of N harvested as oyster product was about 1.3 ton N d–1, which is about 10% of daily N loading in north Hiroshima Bay. According to the N cycle developed in the present study, the results suggest the significant role of suspended oyster culture on the nitrogen cycle in Hiroshima Bay. In addition, our results indicate that oyster production was efficiently harvested, suggesting that oyster culture could probably be used as a tool to remove N from Hiroshima Bay. 相似文献
85.
This study examines the effects of tides on surges, wave setups and waves, in terms of tidal amplitudes and phases, by using a coupled numerical model of Surge, WAve and Tide (called as SuWAT). The SuWAT model, composed of depth integrated nonlinear shallow water equations and Simulating WAves Nearshore (SWAN) model, is able to simultaneously run with an arbitrary number of nested domains by using the Message Passing Interface. The results for an idealized case indicate that surge and wave setup are increased in the phase of low water and decreased in the high water phase; on the other hand, waves change in a reverse manner. Such changes are enhanced by large tidal variations. The conventional method (e.g., surge plus tide independently) has the possibility of overestimation for the total water level. The hindcast results for Typhoon Ewiniar in 2006 show that the run with tides is more accurate 10% than that without tides in coastal areas of Korea. The nested scheme improves the accuracy up to 40% for the prediction of water levels in the simulations. It is shown that the present coupled model, SuWAT, is capable of predicting both water levels and waves under storm events with reasonable accuracy against the observations. 相似文献
86.
87.
Evaluation of various satellite sensors for waterline extraction in a coral reef environment: Majuro Atoll, Marshall Islands 总被引:4,自引:0,他引:4
Hiroya Yamano Hiroto Shimazaki Tsuneo Matsunaga Albon Ishoda Caleb McClennen Hiromune Yokoki Kazuhiko Fujita Yoko Osawa Hajime Kayanne 《Geomorphology》2006,82(3-4):398-411
The ability of five satellite sensor bands (IKONOS band 4, Terra ASTER bands 3 and 4, and Landsat ETM+ bands 4 and 5) was examined to extract the waterline at coral reef coasts (Majuro Atoll, Marshall Islands) using different wavelength regions (near infrared [NIR] and shortwave infrared [SWIR]) and different spatial resolutions (4, 15, and 30 m). After performing georeferencing and normalization of the images, density slicing was used to extract the waterline. Comparisons of extracted waterline positions with ground-level data for eight transects and global positioning system (GPS) tracks of the island shorelines showed that NIR bands were superior to SWIR bands because of the characteristics of the coral reef coasts, including a lack of foam and suspended sediments (which can affect the NIR wavelength region, if present) and the presence of remnant water on reef flats during low tide (which can affect the SWIR wavelength region). A linear relationship was found between the estimation errors of waterline positions and the spatial resolutions of the NIR sensors. Analysis on estimation errors and image costs showed that Terra ASTER band 3 was the most cost-effective sensor for extracting waterlines with reasonable accuracy. The results serve as general guidelines for using satellite-derived data to estimate intertidal topography and detect and monitor shorelines in coral reef environments. 相似文献
88.
The Models-3 Community Multi-scale Air Quality modeling system (CMAQ) coupled with the Regional Atmospheric Modeling System
(RAMS) is used to simulate three-dimensional concentration distributions of hydroxyl (OH) and hydroperoxyl (HO2) radicals over the western Pacific Ocean during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) field
campaign. Modeled values of OH and HO2 and their closely related chemical species and photolysis rates are compared with observational data collected onboard the
DC-8 aircraft. Comparison shows that the model reasonably reproduced these observed values over a broad range of conditions
with an overall tendency to overestimate the measured OH and HO2 by a factor of 1.56 and 1.24, respectively. A case study of OH, HO2 and their closely related chemical species and photolysis rates along the DC-8 flights 11 and 12 conducted on 17–18 March
2001 shows that the model reproduces the temporal and spatial variations reasonable well, and produces more reliable OH and
HO2 concentrations in the polluted environment than in the clean marine boundary layer. 相似文献
89.
Toru Yada Tomoki Nakamura Noriko Matsumoto Hajime Hiyagon Naoji Sugiura Nobuo Takaoka 《Geochimica et cosmochimica acta》2005,69(24):5789-5804
Bulk chemical compositions and oxygen isotopic compositions were analyzed for 48 stony cosmic spherules (melted micrometeorites) collected from the Antarctic ice sheet using electron- and ion-microprobes. No clear correlation was found between their isotopic compositions and textures. The oxygen isotopic compositions showed an extremely wide range from −28‰ to +93‰ in δ18O and from −21‰ to +13‰ in Δ17O. In δ18O-δ17O space, most samples (38 out of 48) plot close to the terrestrial fractionation line, but 7 samples plot along the carbonaceous chondrite anhydrous mineral (CCAM) line. Three samples plot well above the terrestrial fractionation line. One of these has a Δ17O of +13‰, the largest value ever found in solar system materials. One possible precursor for this spherule could be 16O-poor planetary material that is still unknown as a meteorite. The majority of the remaining spherules are thought to be related to carbonaceous chondrites. 相似文献
90.
Atsushi Noda Hajime Katayama Tsumoru Sagayama Kazuya Suga Yasuhito Uchida Kenji Satake Kohei Abe Yukinobu Okamura 《Sedimentary Geology》2007,200(3-4):314-327
A combined approach of field geology and numerical simulation was conducted for evaluating the tsunami impacts on the shelf sediments. The 2003 Tokachi-oki earthquake, M 8.0, that occurred on 25 September 2003 off southeastern Hokkaido, northern Japan, generated a locally destructive tsunami. Maximum run-up height of the tsunami waves reached 4 m above sea level. In order to estimate the tsunami impacts on shallow marine sediments, we compared pre- and post-tsunami marine sediments in water depths of 38–112 m in terms of grain size, sedimentary structure, and microfossil content. Decreases of fine fractions, especially finer than very fine sand, which led to coarsen the mean grain size, were detected in the inner shelf of the northern part of the study area. Foraminiferal assemblages also changed in the coarsened sediments. On the other hand, the other shelf sediments largely unchanged or slightly fined. We also simulated the tsunami wave velocity and direction, and grain size entrained by the modeled tsunami. The numerical simulation resulted in that the 2003 tsunami could transport very fine sand in water depths shallower than 45–95 m at the northern part of the study area. This is comparable with the actual grain-size changes after the tsunami had passed. However, some storms and tidal currents might also be possible to stir the surface sediments after the pre-tsunami survey, so we could not conclude that the grain-size changes had been caused only by the tsunami. Nevertheless, a combined approach of sampling and modeling was powerful for estimating the tsunami impacts under the sea. 相似文献