全文获取类型
收费全文 | 419篇 |
免费 | 6篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 16篇 |
地球物理 | 81篇 |
地质学 | 197篇 |
海洋学 | 33篇 |
天文学 | 77篇 |
综合类 | 3篇 |
自然地理 | 18篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 29篇 |
2012年 | 19篇 |
2011年 | 29篇 |
2010年 | 28篇 |
2009年 | 33篇 |
2008年 | 26篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 16篇 |
2004年 | 22篇 |
2003年 | 20篇 |
2002年 | 18篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有436条查询结果,搜索用时 218 毫秒
181.
Volker?St?hleEmail author Rainer?Altherr Mario?Koch Lutz?Nasdala 《Contributions to Mineralogy and Petrology》2004,148(2):150-159
A dense (~3.34 g cm–3) garnet–sillimanite-rich metamorphic rock from the suevite breccia of the Ries impact crater was studied by scanning-electron microscopy and Raman microprobe spectroscopy. In the strongly shocked rock clast kyanite was formed from sillimanite under momentary high pressures of natural shock waves. Kyanite aggregates were found as thin (~0.3–2.0 m) seams along grain boundaries between, and fractures within, sillimanite grains. Within these seams kyanite c-axes are oriented perpendicular to original grain boundaries and fractures. In addition, larger (up to 10 m) isolated kyanite grains were rarely found within host sillimanite. Filamentary kyanite aggregates and isolated crystals typically show shrinkage cracks due to volume decrease (~10%). Locally, broad interstices between sillimanite crystals are filled with aluminosilicate glass containing a high volume fraction of sub-micrometer-sized euhedral crystals. The silica-rich glass suggests incongruent melting of sillimanite at local post-shock temperatures significantly higher than 1,300°C. The edges of adjacent sillimanite grains are thermally and chemically altered. The local generation of temperature spikes is attributed to strong shock wave interactions due to very high shock impedance contrasts. 相似文献
182.
Rainer?AltherrEmail author Gültekin?Topuz Horst?Marschall Thomas?Zack Thomas?Ludwig 《Contributions to Mineralogy and Petrology》2004,148(4):409-425
An undated high-pressure low-temperature tectonic mélange in the Elekda area (central Pontides, N Turkey) comprises blocks of MORB-derived lawsonite eclogite within a sheared serpentinite matrix. In their outer shells, some of the eclogite blocks contain large (up to 6 cm) tourmaline crystals. Prograde inclusions in poikiloblastic garnet from a well-preserved eclogite block are lawsonite, epidote/clinozoisite, omphacite, rutile, glaucophane, chlorite, Ba-bearing phengite, minor actinolite, winchite and quartz. In addition, glaucophane, lawsonite and rutile occur as inclusions in omphacite. These inclusion assemblages document the transition from a garnet-lawsonite-epidote-bearing blueschist to a lawsonite eclogite with the peak assemblage garnet + omphacite I + lawsonite + rutile. Peak metamorphic conditions are not well-constrained but are estimated approximately 400–430°C and >1.35 GPa, based on Fe–Mg exchange between garnet and omphacite and the coexistence of lawsonite + omphacite + rutile. During exhumation of the eclogite–serpentinite mélange in the hanging wall of a subduction system, infiltration of B-rich aqueous fluids into the rims of eclogite blocks caused retrogressive formation of abundant chlorite, titanite and albite, followed by growth of tourmaline at the expense of chlorite. At the same time, omphacite I (XJd=0.24–0.44) became unstable and partially replaced by omphacite II characterized by higher XJd (0.35–0.48), suggesting a relatively low silica activity in the infiltrating fluid. Apart from Fe-rich rims developed at the contact to chlorite, tourmaline crystals are nearly homogeneous. Their compositions correspond to Na-rich dravite, perhaps with a small amount of excess (tetrahedral) boron (~5.90 Si and 3.10 B cations per 31 anions). 11 B values range from –2.2 to +1.7. The infiltrating fluids were most probably derived from subducting altered oceanic crust and sediments. 相似文献
183.
184.
Trevor J McDougall Rainer Feistel 《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(12):1523-1535
The adiabatic lapse rate is commonly explained as being proportional to the work done on a fluid parcel as its volume changes in response to an increase in pressure. According to this explanation the adiabatic lapse rate would increase with both pressure and the fluid's compressibility, but this is not the case. Rather, the adiabatic lapse rate is proportional to the thermal expansion coefficient and is independent of the fluid's compressibility. Here we show that the adiabatic lapse rate is independent of the increase in the internal energy that a parcel experiences when it is compressed. We explain what is missing from the traditional explanation of the adiabatic lapse rate and we explore the thermodynamic cause of the adiabatic lapse rate. In particular, we seek to explain how the adiabatic lapse rate can be negative in cool fresh water. 相似文献
185.
Shiguo Wu Xiujuan Wang How Kin Wong Guangxue Zhang 《Marine Geophysical Researches》2007,28(2):127-138
The passive northern continental margin of the South China Sea is rich in gas hydrates, as inferred from the occurrence of
bottom-simulating reflectors (BSR) and from well logging data at Ocean Drilling Program (ODP) drill sites. Nonetheless, BSRs
on new 2D multichannel seismic reflection data from the area around the Dongsha Islands (the Dongsha Rise) are not ubiquitous.
They are confined to complex diapiric structures and active fault zones located between the Dongsha Rise and the surrounding
depressions, implying that gas hydrate occurrence is likewise limited to these areas. Most of the BSRs have low amplitude
and are therefore not clearly recognizable. Acoustic impedance provides information on rock properties and has been used to
estimate gas hydrate concentration. Gas hydrate-bearing sediments have acoustic impedance that is higher than that of the
surrounding sediments devoid of hydrates. Based on well logging data, the relationship between acoustic impedance and porosity
can be obtained by a linear regression, and the degree of gas hydrate saturation can be determined using Archie’s equation.
By applying these methods to multichannel seismic data and well logging data from the northern South China Sea, the gas hydrate
concentration is found to be 3–25% of the pore space at ODP Site 1148 depending on sub-surface depth, and is estimated to
be less than values of 5% estimated along seismic profile 0101. Our results suggest that saturation of gas hydrate in the
northern South China Sea is higher than that estimated from well resistivity log data in the gas hydrate stability zone, but
that free gas is scarce beneath this zone. It is probably the scarcity of free gas that is responsible for the low amplitudes
of the BSRs. 相似文献
186.
Numerical prediction experiment on Typhoon Maggie (9903) 总被引:3,自引:1,他引:3
Fong Soi Kun Wu Chisheng Hao I Pan Lam Kin Hang Ku Chi Meng Wang Anyu Lin Wenshi 《海洋学报(英文版)》2001,20(2):171-181
I~IOXTyphoon is a severe and diSaStrous weather phenomenon that affeCts the southeaSt COaStsregion of China. It causes Serious lOSS for the social eCOnondc development as well as the life andproperties Of PeOPle. Therefore, the enhancement to study on the artifice of monitoring, Prediction and public services of typhoon is an i~nent requirement for gove~t and Public.The concern is also a taSk of great Urgency to advanCe meteorolQgical sciences.Starting from the 1980' s, as the deve… 相似文献
187.
Hartmut Beurlen Marcelo R. R. Da Silva Rainer Thomas Dwight R. Soares Patrick Olivier 《Mineralium Deposita》2008,43(2):207-228
The Borborema Pegmatitic Province (BPP), northeastern Brazil, is historically important for tantalum mining and also famous
for top-quality specimens of exotic Nb–Ta oxides and, more recently, for the production of gem quality, turquoise blue, ‘Paraíba
Elbaite.’ With more than 750 registered mineralized rare-element granitic pegmatites, the BPP extends over an area of about
75 by 150 km in the eastern part of the Neoproterozoic Seridó Belt. The Late Cambrian pegmatites are mostly hosted by a sequence
of Neoproterozoic cordierite–sillimanite biotite schists of the Seridó Formation and quartzites and metaconglomerates of the
Equador Formation. The trace-element ratios in feldspar and micas allow to classify most pegmatites as belonging to the beryl–columbite
phosphate subtype. Electron microprobe analyses (EMPA) of columbite, tapiolite, niobian–tantalian rutile, ixiolite and wodginite
group minerals from 28 pegmatites in the BPP are used to evaluate the effectiveness of Nb–Ta oxide chemistry as a possible
exploration tool, to trace the degree of pegmatite fractionation and to classify the pegmatites. The columbite group mineral
composition allows to establish a compositional trend from manganoan ferrocolumbite to manganocolumbite and on to manganotantalite.
This trend is typical of complex spodumene- and/or lepidolite-subtype pegmatites. It clearly contrasts with another trend,
from ferrocolumbite through ferrotantalite to ferrowodginite and ferrotapiolite compositions, typical of pegmatites of the
beryl–columbite phosphate subtype. Large scatter and anomalous trends in zoned crystals partially overlap and conceal the
two main evolution patterns. This indicates that a large representative data set of heavy mineral concentrate samples, collected
systematically along cross-sections, would be necessary to predict the metallogenetic potential of individual pegmatites.
Other mineral species, e.g. garnets and/or tourmaline, with a more regular distribution than Nb–Ta oxides, would be more appropriate
and less expensive for routine exploration purposes. The currently available Nb–Ta oxide chemistry data suggest the potential
for highly fractionated Ta–Li–Cs pegmatites in the BPP, so far undiscovered, and encourages further, more detailed research. 相似文献
188.
189.
190.