全文获取类型
收费全文 | 2442篇 |
免费 | 132篇 |
国内免费 | 33篇 |
专业分类
测绘学 | 40篇 |
大气科学 | 252篇 |
地球物理 | 583篇 |
地质学 | 834篇 |
海洋学 | 174篇 |
天文学 | 483篇 |
综合类 | 5篇 |
自然地理 | 236篇 |
出版年
2022年 | 16篇 |
2021年 | 40篇 |
2020年 | 48篇 |
2019年 | 53篇 |
2018年 | 94篇 |
2017年 | 89篇 |
2016年 | 91篇 |
2015年 | 67篇 |
2014年 | 77篇 |
2013年 | 151篇 |
2012年 | 89篇 |
2011年 | 121篇 |
2010年 | 76篇 |
2009年 | 147篇 |
2008年 | 136篇 |
2007年 | 125篇 |
2006年 | 108篇 |
2005年 | 90篇 |
2004年 | 85篇 |
2003年 | 82篇 |
2002年 | 76篇 |
2001年 | 51篇 |
2000年 | 46篇 |
1999年 | 33篇 |
1998年 | 42篇 |
1997年 | 21篇 |
1996年 | 29篇 |
1995年 | 24篇 |
1994年 | 26篇 |
1993年 | 26篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 26篇 |
1985年 | 24篇 |
1984年 | 16篇 |
1983年 | 31篇 |
1982年 | 28篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 21篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 17篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1973年 | 13篇 |
排序方式: 共有2607条查询结果,搜索用时 12 毫秒
1.
2.
Shelf-mounted Ocean Thermal Energy Conversion (OTEC) plants require installation of cold-water pipes (CWP) on slopes of40deg to depths of 1000 m. In addition, tower platforms containing OTEC power systems may be located on lesser sloped terrain near shore and exposed to special environmental loading problems affecting foundation design. Shelf-mounted installations require careful attention to site selection and geotechnical considerations for foundation integrity on sloped surfaces. This paper primarily discusses research associated with cold-water pipe and foundation installations on steep slopes, although research continues on tower platforms located on the shelf. At least five nations are in various stages of development of OTEC systems for island applications. Each of their systems is either shelf mounted or land based and requires that a large diameter cold-water pipe be installed on a steep slope to provide cold water from 1000-m depths. In addition to the installation and deployment of the large cold-water pipe, the most significant problem is the design and installation of suitable foundations that will last for several decades. To date there is very little experience in the offshore industry for large installations on steep slopes. A major scale-model research project is underway on the slopes of the island of Hawaii. A section of pipe 2.4 m in diameter and 24 m long was installed using combination concrete foundations and joints. The pipe and foundations are fully instrumented to measure environmental loading forces due principally to currents and waves. Environmental measurements will also be taken in the test area. The measurement data will be used to validate available analytical models for subsequent use in aiding industry in providing more cost-effective designs for OTEC pipes and foundations. 相似文献
3.
4.
Angela C. Taylor 《New Astronomy Reviews》2003,47(11-12):925
We discuss two experiments – the Very Small Array (VSA) and the Arcminute MicroKelvin Imager (AMI) – and their prospects for observing the CMB at high angular multipoles. Whilst the VSA is primarily designed to observe primary anisotropies in the CMB, AMI is designed to image secondary anisotropies via the Sunyaev–Zel’dovich effect. The combined ℓ-range of these two instruments is between ℓ=150 and 10,000. 相似文献
5.
6.
Sarah Church Peter Ade James Bock Melanie Bowden John Carlstrom Ken Ganga Walter Gear James Hinderks Wayne Hu Brian Keating John Kovac Andrew Lange Eric Leitch Olivier Mallie Simon Melhuish Anthony Murphy Ben Rusholme Creidhe OSullivan Lucio Piccirillo Clem Pryke Andy Taylor Keith Thompson 《New Astronomy Reviews》2003,47(11-12):1083
QUEST on DASI is a ground-based, high-sensitivity, high-resolution (ℓmax2500) experiment designed to map CMB polarization at 100 and 150 GHz and to measure the power spectra from E-modes, B-modes from lensing of the CMB, and B-modes from primordial gravitational waves. The experiment comprises a 2.6 m Cassegrain optical system, equipped with an array of 62 polarization-sensitive bolometers (PSBs), located at the South Pole. The instrument is designed to minimize systematic effects; features include differencing of pairs of orthogonal PSBs within a single feed, a rotatable achromatic waveplate, and axisymmetric rotatable optics. In addition the South Pole location allows both repeatable and highly controlled observations. QUEST on DASI will commence operation in early 2005. 相似文献
7.
8.
We develop a general formalism for analysing parameter information from non-Gaussian cosmic fields. The method can be adapted to include the non-linear effects in galaxy redshift surveys, weak lensing surveys and cosmic velocity field surveys as part of parameter estimation. It can also be used as a test of non-Gaussianity of the cosmic microwave background. Generalizing maximum-likelihood analysis to second order, we calculate the non-linear Fisher information matrix and likelihood surfaces in parameter space. To this order we find that the information content is always increased by including non-linearity. Our methods are applied to a realistic model of a galaxy redshift survey, including non-linear evolution, galaxy bias, shot-noise and redshift-space distortions to second order. We find that including non-linearities allows all of the degeneracies between parameters to be lifted. Marginalized parameter uncertainties of a few per cent will then be obtainable using forthcoming galaxy redshift surveys. 相似文献
9.
When viewed from the air, Scottish ‘hummocky moraine’ can be resolved into a series of linear ridges that resemble those found at the margins of actively retreating glaciers today. Recent work has supported the interpretation of these linear ridges as ice-marginal landforms and the authors believe that the majority of ‘hummocky moraine’ deposits can be interpreted in this way. Consequently the pattern of deglaciation can be established fairly precisely from the pattern of linear ridges. This approach is applied to the landforms of the northern part of the Loch Lomond Stadial ice-field in order to reconstruct the regional pattern of deglaciation. This leads to important inferences about the significance of topographic control during deglaciation and more importantly it provides fresh insight into the environment of the British Isles during the Loch Lomond Stadial. 相似文献
10.