全文获取类型
收费全文 | 5377篇 |
免费 | 231篇 |
国内免费 | 92篇 |
专业分类
测绘学 | 177篇 |
大气科学 | 615篇 |
地球物理 | 1448篇 |
地质学 | 2302篇 |
海洋学 | 220篇 |
天文学 | 680篇 |
综合类 | 82篇 |
自然地理 | 176篇 |
出版年
2022年 | 43篇 |
2021年 | 84篇 |
2020年 | 66篇 |
2019年 | 40篇 |
2018年 | 173篇 |
2017年 | 167篇 |
2016年 | 247篇 |
2015年 | 175篇 |
2014年 | 264篇 |
2013年 | 315篇 |
2012年 | 260篇 |
2011年 | 208篇 |
2010年 | 252篇 |
2009年 | 271篇 |
2008年 | 213篇 |
2007年 | 180篇 |
2006年 | 135篇 |
2005年 | 137篇 |
2004年 | 101篇 |
2003年 | 99篇 |
2002年 | 108篇 |
2001年 | 109篇 |
2000年 | 94篇 |
1999年 | 88篇 |
1998年 | 104篇 |
1997年 | 76篇 |
1996年 | 92篇 |
1995年 | 73篇 |
1994年 | 69篇 |
1993年 | 53篇 |
1992年 | 39篇 |
1991年 | 43篇 |
1990年 | 49篇 |
1989年 | 45篇 |
1988年 | 32篇 |
1987年 | 48篇 |
1986年 | 42篇 |
1985年 | 37篇 |
1984年 | 50篇 |
1983年 | 59篇 |
1982年 | 45篇 |
1981年 | 42篇 |
1980年 | 44篇 |
1979年 | 51篇 |
1978年 | 50篇 |
1977年 | 41篇 |
1976年 | 36篇 |
1975年 | 51篇 |
1974年 | 42篇 |
1973年 | 39篇 |
排序方式: 共有5700条查询结果,搜索用时 15 毫秒
91.
92.
93.
Christof Müller Bernd Milkereit Thomas Bohlen Friedrich Theilen 《Geophysical Prospecting》2002,50(5):517-526
The use of Boomer sources for 3D seismic imaging of shallow marine structures was investigated in a feasibility study. Boomers show sufficient stability to be used in multichannel seismic surveys. The acquisition of a high-frequency, densely sampled seismic data volume was successfully performed in the Baltic Sea. A Pleistocene fluvial channel system and shallow gas accumulations were revealed beneath the unconsolidated sediments which constitute the sea-floor in the southern Kiel Bay. 相似文献
94.
95.
Mantle Convection Modeling with Viscoelastic/Brittle Lithosphere: Numerical Methodology and Plate Tectonic Modeling 总被引:1,自引:0,他引:1
--The earth's tectonic plates are strong, viscoelastic shells which make up the outermost part of a thermally convecting, predominantly viscous layer. Brittle failure of the lithosphere occurs when stresses are high. In order to build a realistic simulation of the planet's evolution, the complete viscoelastic/brittle convection system needs to be considered. A particle-in-cell finite element method is demonstrated which can simulate very large deformation viscoelasticity with a strain-dependent yield stress. This is applied to a plate-deformation problem. Numerical accuracy is demonstrated relative to analytic benchmarks, and the characteristics of the method are discussed. 相似文献
96.
97.
The bulk composition of organic matter and saturated and aromatic hydrocarbons extracted from 16 samples collected from two Kuperschiefer profiles in the Rudna mine,Southwest Poland has been analyzed to study the role of organic matter during base metal enrichment in the Kupferschiefer shale.The results indicated that the extract yields and saturated hydrocarbon yields decreased with increasing base metal contents.GC and GC/MS analyses indicated that n -alkanes and alkylated aromatic compounds were depleted and may have served as hydrogen donators for thermochemical sulfate reduction.The enrichment of base metal is closely connected with the destruction of hydrocarbons. 相似文献
98.
An Mw based earthquake Catalogue for central, northern and northwestern Europe using a hierarchy of magnitude conversions 总被引:3,自引:1,他引:3
Data from 25 local catalogues and 30special studies of earthquakes in central,northern and northwestern Europe have beenincorporated into a Databank. The dataprocessing includes discriminating eventtypes, eliminating fake events and dupletsand converting different magnitudes andintensities to Mw if this is not givenby the original source. The magnitudeconversion is a key task of the study andimplies establishment of regressionequations where no local relations exist.The Catalogue contains tectonic events fromthe Databank within the area44°N–72°N,25°W–32°E and the time period1300–1993. The lower magnitude level forthe Catalogue entries is setat Mw == 3.50. The area covered by thedifferent catalogues are associated withpolygons. Within each polygon only datafrom one or a small number of the localcatalogues, supplemented by data fromspecial studies, enter the Catalogue. Ifthere are two or more such catalogues orstudies providing a solution for an event,a priority algorithm selects one entry forthe Catalogue. Then Mw is calculatedfrom one of the magnitude types, or frommacroseismic data, given by the selectedentry according to another priority scheme.The origin time, location, Mw magnitude and reference are specified for eachentry of the Catalogue. So is theepicentral intensity, I0, if providedby the original source. Following thesecriteria, a total of about 5,000earthquakes constitute the Catalogue.Although originally derived for the purposeof seismic hazard calculation within GSHAP,the Catalogue provides a data base for manytypes of seismicity and seismic hazardstudies. 相似文献
99.
Rare earth patterns of surface and groundwaters near big cities often show anthropogenic Gd (Gdant) anomalies in addition to geogenic Ce and Y anomalies. The Gdant anomaly is caused by very stable organic complexes, one of which is gadopentetic acid, Gd‐DTPA. Derivatives of this and similar compounds are used as contrast agents in magnetic resonance imaging (MRI) of the human blood system. The organic Gd complexes are stable enough to pass nearly unaffected through sewage treatment plants and are, thereafter, discharged into surface water systems. Water of the rapidly flowing Isarco/Eisack and Adige/Etsch rivers (Provinces of Trento and Bolzano/Bozen, NE Italy) and their tributaries show remarkable variations in anthropogenic Gd contents (Gdant). Low Gdant values are found on Monday and Tuesday, whereas high values are observed during the remaining weekdays. Reliable Gdant balances are calculated for the river system at the confluence of the Adige and its tributaries. At two places local decrease of Gdant indicates exfiltration of groundwater. It is demonstrated that Gdant can be used as a reliably conservative tracer to study the water budget in rapidly flowing alpine river systems. The studied different river waters show considerable negative Ce and positive Y anomalies. Negative Ce anomalies are caused by scavenging of Ce(III) by FeO(OH) precipitates and subsequent oxidation to CeO2. Y anomalies are attributed to less sorption of Y than REE onto particulate matter. Thus, Y moves faster than REE. Both, Ce and Y anomalies, are of geogenic origin. 相似文献
100.
In Italy, the horizontal stress directions are well constrained in many regions, but the tectonic regime is not well known because the stress magnitudes are unknown. Our intention is to improve the knowledge of crustal stress in Italy, both at shallow depth and in low seismicity areas. Therefore, we inferred the tectonic regime from the comparison between the depth of breakout occurrence and the physical properties of the rocks in 20 boreholes. The critical value of the maximum horizontal stress, for which the effective tangential stress at the borehole wall overcomes the rock strength to form breakouts, could be computed from rock strength and density. Comparing the theoretical stress distributions for different tectonic regimes with the depth distribution of breakout occurrence, it is possible to infer the tectonic regime that fits best to the breakout depth distribution. We investigated boreholes up to 6 km deep located in different tectonic environments over the Italian peninsula: the Po Plain, the Apenninic chain, the Adriatic foredeep and the Tyrrhenian Quaternary volcanic region. These wells are characterised by breakout data of good quality (A, B and C, according to World Stress Map quality ranking system). The results are in general agreement with the style of faulting derived from earthquake focal mechanisms and other stress indicators. Our results show a predominance of a normal faulting (NF) regime in the inner Apennines and both normal faulting and strike–slip faulting (SS) style in the surrounding regions, possibly also associated with changes in the tectonic regime with depth. 相似文献