全文获取类型
收费全文 | 292篇 |
免费 | 30篇 |
国内免费 | 50篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 108篇 |
地球物理 | 63篇 |
地质学 | 110篇 |
海洋学 | 26篇 |
天文学 | 41篇 |
综合类 | 4篇 |
自然地理 | 7篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 14篇 |
2012年 | 12篇 |
2011年 | 17篇 |
2010年 | 17篇 |
2009年 | 15篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 17篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 8篇 |
2002年 | 16篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 16篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 3篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有372条查询结果,搜索用时 0 毫秒
231.
John T. Wasson William V. Boynton Chen-Lin Chou Philip A. Baedecker 《Earth, Moon, and Planets》1975,13(1-3):121-141
Siderophilic element/Ir ratios are higher in mature lunar soils from highlands sites than in those from mare sites. We infer that the population of materials responsible for the early intense bombardment of the Moon had high ratios, and that the population responsible for the essentially constant flux has low ratios. No group of chondrites has siderophile/Ir ratios identical to those in the mare or highlands soils; CM chondrites are the most similar, and CM-like materials may account for a major fraction of Earth-crossing materials during the past 3.7 b.y.Siderophile/Ir ratios may be used to determine the amount of highlands regolith in soils or breccias from the mare-highlands interface areas (Apollo 15 and 17), and to infer the time of formation of highlands breccias whose sideropbiles originated in mature soils. Arguments are summarized against the viewpoint that the siderophiles in most highlands breccias originated in basin-forming projectiles. Differences in mature soil siderophile concentrations at Apollo 14 and 16 indicate a substantially greater concentration at the latter site immediately following the Imbrium event.Siderophile concentrations are used to estimate mean regolith depths at the landing sites; as relative values these are more precise than estimates based on seismic or crater observations. The longlived flux is calculated to be 2.9 g cm–2 b.y.–1 averaged over the past 3.7 b.y. A consideration of the relationship between mass fluence and time indicates that the mass flux decreased with a half-life of about 40 m.y. immediately following the Imbrium event. 相似文献
232.
233.
AN ATMOSPHERIC MOTION EQUATION BUILT ON THE CONSERVATIVE RELATIONSHIP OF THE ANGULAR MOMENTUM EXCHANGE BETWEEN THE SOLID EARTH AND THE ATMOSPHERE ON SEASONAL-ANNUAL TIMESCALE* 下载免费PDF全文
Within the seasonal-annual timeseale,there exists an angular momentum conservative exchange relationship between the solid earth and the atmosphere,and their angular momentum exchange not only can cause variations in length-of-day(LOD) but also can express anomalies in atmospheric general circulation.Therefore,their angular momentum exchange mechanism should be introduced into the general circulation model.Considering the angular momentum anomalous exchange caused by the air-earth interface friction effect,a whole-layer atmospheric motion equation is derived in this paper including the earth spin anomalous friction force parameterized by using the change in the earth rotation rate.Through analysing the equation,it shows that the magnitude of the earth spin anomalous friction force is the same as that of Coriolis force on seasonal-annual timescale. 相似文献
234.
235.
236.
Carbonate chemistry and projected future changes in pH and CaCO3 saturation state of the South China Sea 总被引:3,自引:0,他引:3
Chen-Tung Arthur Chen Shu-Lun Wang Wen-Chen Chou David D. Sheu 《Marine Chemistry》2006,101(3-4):277-305
To study the dissolved carbonate system in the South China Sea (SCS) and to understand the water mass exchange between the SCS and the West Philippine Sea (WPS), pH, total alkalinity and total CO2 were measured aboard the R/V Ocean Researcher 1. Because of the sill that separates these two seas in the Luzon Strait with a maximum depth of 2200 m, the SCS Deep Water has characteristics similar to those of water at about 2200 m in the WPS. The minimum pH and the maxima of normalized alkalinity and total CO2 commonly found in the open oceans at mid-depth also prevail in the WPS but are, however, very weak in the SCS. Rivers and inflows from Kuroshio Surface and Deep Waters through the Luzon Strait as well as those through the Mindoro Strait transport carbon to the SCS year-round. Meanwhile, the outflowing Taiwan Strait water as well as the SCS Surface and Intermediate Waters of the Luzon Strait transports carbon out of the SCS year-round. The Sunda Shelf is also a channel for carbon transport into the SCS in the wet season and out of the SCS in the dry season.fCO2 data and mass balance calculations indicate that the SCS is a weak CO2 source in the wet season but an even weaker CO2 sink in the dry season. With these facts taken together, the SCS is likely a very weak CO2 source. Anthropogenic CO2 penetrates to about 1500 m in depth in the SCS, and the entire SCS contains 0.60 ± 0.15 × 1015 g of excess carbon. Typical profiles of pH as well as the degree of saturation of each of calcite and aragonite in 1850 and 1997 are presented, and those for 2050 AD are projected. The maximum decrease in pH is estimated to be 0.16 pH units in the surface layer when the amount of CO2 is doubled. It is anticipated that aragonite in the upper continental slope will likely start to dissolve, thereby neutralizing excess CO2 by around 2050 AD. This paper is unique in that it presents the results of the first attempt ever to estimate the past, present and future physico-chemical properties of the world's largest marginal sea. 相似文献
237.
Spatial form of urbanization,sustainability and fragmented landownership: the example of Ilan in Taiwan’s urbanization 总被引:1,自引:0,他引:1
As a part of the inevitable process of industrialization, urbanization and its associated spatial forms generally have a substantial effect on sustainability. This paper considers the spatial form and sustainability of urbanization by evaluating the interaction between land-use planning, urban regimes and the fragmented structure of land ownership. This paper conceptualizes the structure of landownership as an institution that affects the form of spatial development and thereby determines the spatial implications of urban sprawl on sustainability. With reference to the Ilan experience of urbanizing Taiwan, it shows that the development of spatial form and sustainability is the product of planning institution and urban regime mobilization, and it reflects the institutional impact of a fragmented landownership structure. The conclusion also discusses policy implications. 相似文献
238.
John C. Jackson J. Wright Horton Jr. I‐Ming Chou Harvey E. Belkin 《Meteoritics & planetary science》2016,51(5):946-965
The occurrence of coesite in suevites from the Chesapeake Bay impact structure is confirmed within a variety of textural domains in situ by Raman spectroscopy for the first time and in mechanically separated grains by X‐ray diffraction. Microtextures of coesite identified in situ investigated under transmitted light and by scanning electron microscope reveal coesite as micrometer‐sized grains (1–3 μm) within amorphous silica of impact‐melt clasts and as submicrometer‐sized grains and polycrystalline aggregates within shocked quartz grains. Coesite‐bearing quartz grains are present both idiomorphically with original grain margins intact and as highly strained grains that underwent shock‐produced plastic deformation. Coesite commonly occurs in plastically deformed quartz grains within domains that appear brown (toasted) in transmitted light and rarely within quartz of spheroidal texture. The coesite likely developed by a mechanism of solid‐state transformation from precursor quartz. Raman spectroscopy also showed a series of unidentified peaks associated with shocked quartz grains that likely represent unidentified silica phases, possibly including a moganite‐like phase that has not previously been associated with coesite. 相似文献
239.
Xiaolin Wang I.-Ming Chou Robert C. Burruss Yucai Song 《Geochimica et cosmochimica acta》2011,75(14):4080-4093
Raman spectroscopy is a powerful method for the determination of CO2 densities in fluid inclusions, especially for those with small size and/or low fluid density. The relationship between CO2 Fermi diad split (Δ, cm−1) and CO2 density (ρ, g/cm3) has been documented by several previous studies. However, significant discrepancies exist among these studies mainly because of inconsistent calibration procedures and lack of measurements for CO2 fluids having densities between 0.21 and 0.75 g/cm3, where liquid and vapor phases coexist near room temperature.In this study, a high-pressure optical cell and fused silica capillary capsules were used to prepare pure CO2 samples with densities between 0.0472 and 1.0060 g/cm3. The measured CO2 Fermi diad splits were calibrated with two well established Raman bands of benzonitrile at 1192.6 and 1598.9 cm−1. The relationship between the CO2 Fermi diad split and density can be represented by: ρ = 47513.64243 − 1374.824414 × Δ + 13.25586152 × Δ2 − 0.04258891551 × Δ3 (r2 = 0.99835, σ = 0.0253 g/cm3), and this relationship was tested by synthetic fluid inclusions and natural CO2-rich fluid inclusions. The effects of temperature and the presence of H2O and CH4 on this relationship were also examined. 相似文献
240.
Jing Peng Wenjie Dong Wenping Yuan Jieming Chou Yong Zhang Juan Li 《Theoretical and Applied Climatology》2013,111(3-4):483-495
Numerous studies have shown that increased atmospheric CO2 concentration is one of the most important factors altering land water balance. In this study, we investigated the effects of increased CO2 on global land water balance using the dataset released by the Coupled Model Intercomparison Project Phase 5 derived from the Canadian Centre for Climate Modelling and Analysis second-generation Earth System Model. The results suggested that the radiative effect of CO2 was much greater than the physiological effect on the water balance. At the model experiment only integrating CO2 radiative effect, the precipitation, evapotranspiration (ET) and runoff had significantly increased by 0.37, 0.12 and 0.31 mm year?2, respectively. Increases of ET and runoff caused a significant decrease of soil water storage by 0.05 mm year?2. However, the results showed increases of runoff and decreases of precipitation and ET in response to the CO2 fertilisation effect, which resulted into a small, non-significant decrease in the land water budget. In the Northern Hemisphere, especially on the coasts of Greenland, Northern Asia and Alaska, there were obvious decreases of soil water responding to the CO2 radiative effect. This trend could result from increased ice–snow melting as a consequence of warmer surface temperature. Although the evidence suggested that variations in soil moisture and snow cover and vegetation feedback made an important contribution to the variations in the land water budget, the effect of other factors, such as aerosols, should not be ignored, implying that more efforts are needed to investigate the effects of these factors on the hydrological cycle and land water balance. 相似文献