全文获取类型
收费全文 | 808篇 |
免费 | 14篇 |
国内免费 | 15篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 60篇 |
地球物理 | 170篇 |
地质学 | 386篇 |
海洋学 | 39篇 |
天文学 | 118篇 |
综合类 | 3篇 |
自然地理 | 38篇 |
出版年
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 13篇 |
2014年 | 25篇 |
2013年 | 37篇 |
2012年 | 28篇 |
2011年 | 24篇 |
2010年 | 31篇 |
2009年 | 36篇 |
2008年 | 27篇 |
2007年 | 41篇 |
2006年 | 32篇 |
2005年 | 25篇 |
2004年 | 27篇 |
2003年 | 29篇 |
2002年 | 30篇 |
2001年 | 26篇 |
2000年 | 16篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 25篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 19篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1966年 | 5篇 |
1958年 | 5篇 |
排序方式: 共有837条查询结果,搜索用时 0 毫秒
71.
Increases in human water consumption (HWC) and consequent degradation of the ecological environment are common in arid regions. Understanding the mechanisms behind these processes is important for sustainable development. Analyses of changes in HWC between alternating wet and dry periods are carried out in four arid inland basins in Central Asia and China (Syr Darya, Tarim, Heihe and Shulehe river basins). Based on runoff records, the presence of an asymmetric HWC response is proved (p < 0.01), with an increase in HWC during wet periods and a muted decrease during subsequent dry periods. This behaviour is interpreted by invoking theories from behavioural economics at the individual and community levels. A simple model based on these theories is shown to be able to reproduce the observed dynamics and is used to discuss the importance of strengthening institutional factors for water sustainability. 相似文献
72.
73.
74.
Dáithí Stone Maximilian Auffhammer Mark Carey Gerrit Hansen Christian Huggel Wolfgang Cramer David Lobell Ulf Molau Andrew Solow Lourdes Tibig Gary Yohe 《Climatic change》2013,118(2):381-395
Future scenarios of the energy system under greenhouse gas emission constraints depict dramatic growth in a range of energy technologies. Technological growth dynamics observed historically provide a useful comparator for these future trajectories. We find that historical time series data reveal a consistent relationship between how much a technology’s cumulative installed capacity grows, and how long this growth takes. This relationship between extent (how much) and duration (for how long) is consistent across both energy supply and end-use technologies, and both established and emerging technologies. We then develop and test an approach for using this historical relationship to assess technological trajectories in future scenarios. Our approach for “learning from the past” contributes to the assessment and verification of integrated assessment and energy-economic models used to generate quantitative scenarios. Using data on power generation technologies from two such models, we also find a consistent extent - duration relationship across both technologies and scenarios. This relationship describes future low carbon technological growth in the power sector which appears to be conservative relative to what has been evidenced historically. Specifically, future extents of capacity growth are comparatively low given the lengthy time duration of that growth. We treat this finding with caution due to the low number of data points. Yet it remains counter-intuitive given the extremely rapid growth rates of certain low carbon technologies under stringent emission constraints. We explore possible reasons for the apparent scenario conservatism, and find parametric or structural conservatism in the underlying models to be one possible explanation. 相似文献
75.
Wolfgang Kundt 《Planetary and Space Science》1983,31(11):1339-1343
The problem is discussed whether atmospheric superrotation is driven by internal or external torques. An integral constraint is derived which under certain conditions forbids geostrophic flow, and suggests corkscrew-shaped motion along zones of constant latitude. A momentum balance consideration restricts effective viscosities in the upper atmospheres to be much smaller than maximal eddy viscosity, perhaps as small as molecular viscosity. 相似文献
76.
The Austrian node of the Natural Resources Satellite Remote Sensing Cloud Service Platform was established in 2016 through a cooperation agreement between the Land Satellite Remote Sensing Application Center(LASAC),Ministry of Natural Resources of the Peoples Republic of China and the University of Vienna,Austria.Under this agreement panchromatic and multi-spectral data of the Chinese ZY-3 satellite are pushed to the server at the University of Vienna for use in education and research.So far,nearly 500 GB of data have been uploaded to the server.This technical note briefly introduces the ZY-3 system and illustrates the implementation of the agreement by the first China-Sat Workshop and several case studies.Some of them are already completed,others are still ongoing.They include a geometric accuracy validation of ZY-3 data,an animated visualization of image quick views on a spherical display to demonstrate the time series of the image coverage for Austria and Laos,and the use of ZY-3 data to study the spread of bark beetle in the province of Lower Austria.An accuracy study of DTMs from ZY-3 stereo data,as well as a land cover analysis and comparison of Austria with ZY-3 and other sensors are still ongoing. 相似文献
77.
Bruno Ribbat Wolfgang Roether Karl Otto Münnich 《Earth and Planetary Science Letters》1976,32(2):331-341
A14C balance for the Eastern Caribbean deep water indicates the average inflow of Atlantic water into the basin to be 2.3 × 105 m3/sec (±30%), or about 2–4 times the values estimated previously. The balance uses a model representation of the deep-water turnover, and is based on14C concentrations at a station in the Venezuelan Basin which average Δ14C= 89‰ below 800 m depth with a total range of only 9‰, as well as on a14C concentration of the Atlantic inflow of Δ14C= ?71%. as obtained from measurements outside the Antilles Arch. The turnover time of the basin water below 2500 m depth is 55 years, which corresponds to an average upwelling velocity at this depth of about 35 m/year. With such upwelling, the temperature profile below 1800 m (the depth of the sill determining the inflow of new water) requires a vertical eddy diffusivity of about 5 cm2/sec. The oxygen consumption, and silica and CO2 regeneration, rates below 2500 m depth are obtained as ?0.18, + 0.08, and + 0.2 μmole kg?1 yr?1, respectively. The CO2 regeneration has but a negligible effect on the14C balance. 相似文献
78.
79.
This review describes advances in radiative transfer theory since about 1985. We stress fundamental aspects and emphasize
modern methods for the numerical solution of the transfer equation for spatially multidimensional problems, for both unpolarized
and polarized radiation. We restrict the discussion to two-level atoms with noninverted populations for given temperature,
density and velocity fields.
Unfortunately this article was originally published with typesetter's errors: The correct publication date was 25 February
2006, not 3 January 2006. The content was not in the final form. The publishers wish to apologize for this mistake. The online
version of the original version can be found at /10.1007/s00159-005-0025-8. 相似文献
80.