全文获取类型
收费全文 | 1428篇 |
免费 | 81篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 26篇 |
大气科学 | 107篇 |
地球物理 | 372篇 |
地质学 | 522篇 |
海洋学 | 123篇 |
天文学 | 233篇 |
综合类 | 12篇 |
自然地理 | 131篇 |
出版年
2023年 | 9篇 |
2022年 | 5篇 |
2021年 | 28篇 |
2020年 | 24篇 |
2019年 | 23篇 |
2018年 | 47篇 |
2017年 | 44篇 |
2016年 | 49篇 |
2015年 | 45篇 |
2014年 | 61篇 |
2013年 | 101篇 |
2012年 | 58篇 |
2011年 | 87篇 |
2010年 | 72篇 |
2009年 | 102篇 |
2008年 | 79篇 |
2007年 | 63篇 |
2006年 | 62篇 |
2005年 | 59篇 |
2004年 | 53篇 |
2003年 | 45篇 |
2002年 | 58篇 |
2001年 | 21篇 |
2000年 | 19篇 |
1999年 | 21篇 |
1998年 | 21篇 |
1997年 | 18篇 |
1996年 | 27篇 |
1995年 | 18篇 |
1994年 | 14篇 |
1993年 | 3篇 |
1992年 | 20篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有1526条查询结果,搜索用时 31 毫秒
861.
862.
Cosmogenic radionuclide (CRN) exposure ages provide evidence for the limited extent of last glacial maximum glaciers in the Tanggula Shan, central Tibetan Plateau. The most extensive advances occurred during or before marine oxygen isotope stage 6 (MIS-6) based on previous CRN exposure ages. The second most extensive advance occurred during or before MIS-4 based on previous ages and new ages of 41,400 ± 4300, and 66,800 ± 7100 10Be yr. A MIS-2 advance of less than 3 km occurred between 31,900 ± 3400 and 16,000 ± 1700 10Be yr. 相似文献
863.
Why rehabilitate urban river systems? 总被引:2,自引:0,他引:2
This paper addresses the philosophical question: 'why rehabilitate urban river systems?' within an Australian context. Rehabilitation of river systems has become an important objective of many local, state and national governments around the world, who allocate substantial investment into various river projects. An understanding of the various factors influencing stream condition and potential rehabilitation options is essential in order to determine how the process is undertaken, and how success is measured. This paper examines the triple bottom line (economic, social and environmental) factors that influence decisionmaking with respect to urban stream rehabilitation and management and considers their relative value and importance. 相似文献
864.
Instream, overbank and cut riverbank exposures along the East Branch of the Finniss River downstream of Rum Jungle Mine, Northern Territory have been analysed for their total metal concentrations using instrumental neutron activation analysis (INAA). Concentration values for the < 62.5 μm and bulk sample fractions are compared to Australian sediment quality guidelines values (ANZECC/ARMCANZ, 2000). The results reveal that channel and overbank environments are contaminated with heavy metals, with many samples exceeding the low and high sediment guidelines values. The < 62.5 μm fraction is consistently more contaminated than bulk samples as are instream environments compared to adjacent overbank environments. Metal concentrations are strongly correlated to sediment pH and Fe values, suggesting that these variables are significant in controlling the spatial distribution of sediment-associated metals. The strong positive correlation between sediment-associated metals and Fe is probably related to the process of metal sequestration by Fe (and Mn) oxyhydroxides. The spatial distribution of sediment-associated metals downstream of the Rum Jungle Mine site does not display a simple distance–metal concentration decay pattern. It is suggested that the non-uniform spatial distribution of sediment-associated metals is a function of local, reach-scale variations in channel geometry and geomorphology, which control sediment storage and transfer patterns. In cut riverbank exposures the vertical of metals distribution is non-uniform and probably reflects differential metal mobility. Despite rehabilitation of the mine site in the 1980s, the elevated sediment-associated metal concentrations that remain within the East Branch of the Finniss River system are likely to render the system contaminated for the foreseeable future and limit the potential for the full recovery of aquatic and terrestrial flora and fauna. 相似文献
865.
A continuous 36 year long record of semi-monthly temperature profiles from the central Strait of Georgia, British Columbia is used to examine low frequency variability and trends through the water column. Decomposition of temperature anomalies into empirical orthogonal functions shows that the dominant mode accounts for 78% of the variance, while the principal component associated with this mode (PC1) is dominated by fluctuations on interannual time scales. To relate the variability within the Strait to that occurring over the northeast Pacific, PC1 is compared with anomalies in local air temperature, sea surface temperatures off the west coast of Vancouver Island, and upper ocean temperatures along Line-P. These comparisons suggest that much of the interannual variability observed in the Strait of Georgia occurs in response to large-scale atmospheric forcing over the northeast Pacific. However, following tropical El Niño events there are significant anomalies associated with processes occurring along the coastal oceanic wave guide. The strongest event in the entire record, the remarkable negative temperature anomaly of winter 1978/1979, appears to be associated with a deep water intrusion that was forced locally. 相似文献
866.
867.
Yann Leredde Cléa Denamiel Elena Brambilla Christine Lauer-Leredde Frédéric Bouchette Patrick Marsaleix 《Continental Shelf Research》2007
The Gulf of Aigues-Mortes (NW Mediterranean Sea) is a midshelf zone whose scale is an intermediate between the nearshore scale (0–10 m depth) and the coastal scale (including the whole continental shelf). Its hydrodynamics is investigated for the first time. ADCP, CTD and thermosalinograph data were collected during three short cruises (HYGAM; March 6–7, 20–21, April 5–6, 2005). They were scheduled approximately every 15 days to sample the gulf circulation under different weather conditions. Moreover, the cruise data were used to validate the Symphonie model, a 3D primitive equations circulation model. The circulation features displayed by in situ data were well reproduced by Symphonie. A downscaling modelling approach was implemented, the largest scale being obtained by the replay of the MFSTEP regional model of the North-Western Mediterranean Sea. 相似文献
868.
The dynamo explanation of Mercury's magnetic field leads to constraints on the thermal evolution of the planet. A heat-source density at least comparable to the Earth's mantle-wide average must have been retained throughout Mercury's mantle, if the core is still molten, and if Mercury's mantle possesses rheological properties similar to those of the Earth's upper mantle. 相似文献
869.
K. A. Papp K. A. Innanen A. T. Patrick 《Celestial Mechanics and Dynamical Astronomy》1978,18(3):277-286
The relative merits of five algorithms for numerical orbit computation in galaxy models are discussed. Each method has its peculiar advantages; the choice of algorithm depends mainly on the complexity of the force equations and the required accuracy.Centre for Research in Experimental Space Science. 相似文献
870.
Impact of a sea breeze on the boundary-layer dynamics and the atmospheric stratification in a coastal area of the North Sea 总被引:1,自引:0,他引:1
Charles Talbot Patrick Augustin Céline Leroy Véronique Willart Hervé Delbarre Georgui Khomenko 《Boundary-Layer Meteorology》2007,125(1):133-154
In-situ sodar and lidar measurements were coupled with numerical simulations for studying a sea-breeze event in a flat coastal
area of the North Sea. The study’s aims included the recognition of the dynamics of a sea-breeze structure, and its effects
on the lower troposphere stratification and the three-dimensional (3D) pollutant distribution. A sea breeze was observed with
ground-based remote sensing instruments and analysed by means of numerical simulations using the 3D non-hydrostatic atmospheric
model Meso-NH. The vertical structure of the lower troposphere was experimentally determined from the lidar and sodar measurements,
while numerical simulations focused on the propagation of the sea breeze inland. The sea-breeze front, the headwind, the thermal
internal boundary layer, the gravity current and the sea-breeze circulation were observed and analysed. The development of
a late stratification was also observed by the lidar and simulated by the model, suggesting the formation of a stable multilayered
structure. The transport of passive tracers inside the sea breeze and their redistribution above the gravity current was simulated
too. Numerical modelling showed that local pollutants may travel backward to the sea above the gravity current at relatively
low speed due to the shearing between the landward gravity current and the seaward synoptic wind. Such dynamic conditions
may enhance an accumulation of pollutants above coastal industrial areas. 相似文献