全文获取类型
收费全文 | 930篇 |
免费 | 25篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 89篇 |
地球物理 | 179篇 |
地质学 | 271篇 |
海洋学 | 80篇 |
天文学 | 226篇 |
自然地理 | 90篇 |
出版年
2020年 | 8篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 23篇 |
2014年 | 21篇 |
2013年 | 45篇 |
2012年 | 28篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 46篇 |
2008年 | 40篇 |
2007年 | 38篇 |
2006年 | 48篇 |
2005年 | 26篇 |
2004年 | 34篇 |
2003年 | 31篇 |
2002年 | 24篇 |
2001年 | 20篇 |
2000年 | 22篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 16篇 |
1993年 | 16篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 6篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 22篇 |
1982年 | 18篇 |
1981年 | 22篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1977年 | 13篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1971年 | 10篇 |
1969年 | 6篇 |
排序方式: 共有958条查询结果,搜索用时 15 毫秒
1.
We present solutions for the effective stress induced by gas flow through a porous solid into a borehole resulting from sudden pressure reduction. Tensile effective stress that exceeds the strength of the solid will lead to borehole failure. This has applications to the intentional creation of cavities, relevant to the efficient recovery of coalbed methane, and the avoidance of borehole stability problems in conventional gas production. 相似文献
2.
3.
4.
Barry Y. Welsh 《Astrophysics and Space Science》1983,90(2):437-444
High resolution optical observations (FWHM ~ 10–13 km s?1) of the I-S gas towards the early-type stars HD 164 794, HD 164816, and HD 165052 in the M8 Nebula are presented. A high velocity componentV LSR=?26 km s?1 has been detected in all 3 stars' spectra. A line profile fitting analysis has been carried out on the observed Caii and Nai absorption lines to determine cloud component column densities and to subsequently determine the physical and chemical conditions of the associated I-S gas. 相似文献
5.
Barry Wolf 《Pure and Applied Geophysics》1967,67(1):76-82
Summary A study is made of the scattered field which results when a Love wave is incident on a layer having an irregular surface. To obtain this solution a perturbation method is used. It is shown that the scattered field may be described by a superposition of Love waves and non-propagating disturbances. As an illustrative example, the result is applied to obtain the scattering by a triangular trough. 相似文献
6.
7.
Glutathione S-transferase activity was measured in the hepatic cytosol front Dissostichus mawsoni and Pagothenia borchgrevinki. Activity measures with 1-chloro-2,4-dinitrobenzene as substrate were 11·2 and 16·7 μmol/min/g tissue respectively. Little or no activity was detected when p-nitrobenzyl chloride or 3,4-dichloro-1-nitrobenzene were used as substrate. The hepatic glutathione S-transferases from D. mawsoni were partially purified using gel filtration and chromatofocusing. Three peaks of activity were resolved. The major isozyme (158-fold purification) eluting at pH7·1 appeared to be catalytically a homodimer. The isozyme was highly inhibited by triphenyltin chloride (IC50 = 0·1 μ) while inhibition constants for Cibicron Blue 3GA, bromosulphophalein and hematin were 1·1, 20 and 34 μ respectively. 相似文献
8.
9.
Bioerosion by chemosynthetic biological communities on Holocene submarine slide scars 总被引:1,自引:0,他引:1
Geomorphic, stratigraphic, and faunal observations of submarine slide scars that occur along the flanks of Monterey Canyon in 2.0–2.5 km water depths were made to identify the processes that continue to alter the surface of a submarine landslide scar after the initial slope failure. Deep-sea chemosynthetic biological communities and small caves are common on the sediment-free surfaces of the slide scars, especially along the headwall. The chemosynthetic organisms observed on slide scars in Monterey Canyon undergo a faunal succession based in part on their ability to maintain their access to the redox boundaries in the sediment on which they depend on as an energy source. By burrowing into the seafloor, these organisms are able to follow the retreating redox boundaries as geochemical re-equilibration occurs on the sole of the slide. As these organisms dig into the seafloor on the footwall, they often generate small caves and weaken the remaining seafloor. While chemosynthetic biological communities are typically used as indicators of fluid flow, these communities may be supported by methane and hydrogen sulfide that are diffusing out of the fresh seafloor exposed at the sole of the slide by the slope failure event. If so, these chemosynthetic biological communities may simply mark sites of recent seafloor exhumation, and are not reliable fluid seepage indicators. 相似文献
10.