全文获取类型
收费全文 | 214篇 |
免费 | 8篇 |
国内免费 | 3篇 |
学科分类
地球科学 | 225篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 14篇 |
2013年 | 13篇 |
2012年 | 8篇 |
2011年 | 15篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 14篇 |
2007年 | 4篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有225条查询结果,搜索用时 0 毫秒
1.
In situ strength measurements on natural upper-mantle minerals 总被引:1,自引:0,他引:1
Junji Yamamoto Jun-ichi Ando Hiroyuki Kagi Toru Inoue Akihiro Yamada Daisuke Yamazaki Tetsuo Irifune 《Physics and Chemistry of Minerals》2008,35(5):249-257
Using in situ strength measurements at pressures up to 10 GPa and at room temperature, 400, 600, and 700°C, we examined rheological
properties of olivine, orthopyroxene, and chromian-spinel contained in a mantle-derived xenolith. Mineral strengths were estimated
using widths of X-ray diffraction peaks as a function of pressure, temperature, and time. Differential stresses of all minerals
increase with increasing pressure, but they decrease with increasing temperature because of elastic strain on compression
and stress relaxation during heating. During compression at room temperature, all minerals deform plastically at differential
stress of 4–6 GPa. During subsequent heating, thermally induced yielding is observed in olivine at 600°C. Neither orthopyroxene
nor spinel shows complete stress relaxation, but both retain some stress even at 700°C. The strength of the minerals decreases
in the order of chromian-spinel ≈ orthopyroxene > olivine for these conditions. This order of strength is consistent with
the residual pressure of fluid inclusions in mantle xenoliths. 相似文献
2.
Previous studies have shown that metal partitioned to a subcellular compartment containing trophically available metal (TAM) is readily available to predators and may be enhanced by increased binding of metal to heat-stable proteins (HSP - e.g., metallothioneins). The aim of the current investigation was to determine the influence of TAM on the trophic transfer of Cd along an experimental, three-level food chain: Artemia franciscana (brine shrimp)-->Palaemonetes pugio (grass shrimp)-->Fundulus heteroclitus (mummichog). P. pugio were fed for 7 days on A. franciscana exposed to Cd in solution (including (109)Cd as radiotracer) and subjected to subcellular fractionation or fed to F. heteroclitus. An HSP-driven increase in the percentage of Cd associated with TAM (TAM-Cd%) in A. franciscana exposed to 1 muM Cd resulted in a bioenhancement (i.e., a greater than linear increase with respect to A. franciscana exposure) of Cd trophic transfer to P. pugio. Increased dietary Cd exposure did not affect TAM-Cd% in P. pugio nor trophic transfer to F. heteroclitus. 相似文献
3.
Alper Baba 《Environmental Geology》2002,41(8):916-921
4.
A model for the stress‐dependent elastic wave velocity response of fractured rock mass is proposed based on experimental evidence of stress‐dependent fracture normal and shear stiffness. Previously proposed models and previous experimental studies on stress‐dependent fracture stiffness have been reviewed to provide a basis for the new model. Most of the existing stress‐dependent elastic wave velocity models are empirical, with model parameters that do not have clear physical meanings. To propose the new model, the rock mass is assumed to have randomly oriented microscopic fractures. In addition, the characteristic length of microfractures is assumed to be sufficiently short compared to the rock mass dimensions. The macroscopic stress‐dependent elastic wave velocity response is assumed to be attributed to the stress dependency of fracture stiffness. The stress‐dependent fracture normal stiffness is defined as a generalized power law function of effective normal stress, which is a modification of the Goodman's model. On the other hand, the stress dependency of fracture shear stiffness is modeled as a linear function of normal stress based on experimental data. Ultrasonic wave velocity responses of a dry core sample of Berea sandstone were tested at effective stresses ranging from 2 to 55 MPa. Visual observation of thin sections obtained from the Berea sandstone confirms that the assumptions made for microstructure of rock mass model are appropriate. It is shown that the model can describe the stress‐dependent ultrasonic wave velocity responses of dry Berea sandstone with a set of reasonable material parameter values. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
5.
A garnet-omphacite-kyanite-coesite geothermobarometer is constructed to estimate the peak metamorphic pressure of ultrahigh-pressure
(UHP) eclogites. For this we use a quaternary regular solution model for garnet, and propose a new model for sodic pyroxene
that assumes double site solid-solution (Na,Ca)M2(Al,Fe3+,Fe2+,Mg)M1Si2O6, where cations in the M2- and the M1-sites mix randomly but with inter-site interactions, not only between nearest neighboring
cations but also between next nearest neighboring cations. In the new model, overall excess interaction parameters are quantitatively
deduced from the previous experimental data and critical temperature, and the activity of the jadeite component agrees reasonably
with that based on the Landau theory. Furthermore, the relations of the calculated order parameter to temperature and composition
are consistent with other experimental works. These facts support the usefulness of the new model. Application of our geothermobarometer
to kyanite eclogite gave metamorphic conditions around 3.4 GPa and 800 ∘C for both samples from the Dora Maira Massif, Western Alps, and from Rongcheng County, in the Su-Lu region of eastern China.
Received: 30 December 1996 / Accepted: 25 August 1997 相似文献
6.
Hydrogeochemical and isotopic composition of a low-temperature geothermal source in northwest Turkey: case study of Kirkgecit geothermal area 总被引:1,自引:1,他引:1
Chemical and isotopic compositions of three hot springs and one cold spring in the Kirkgecit geothermal field, located 15 km
southwest of Canakkale-Biga in the northwest of Turkey, were monitored five times during 2005 and 2007. The physico-chemical
characteristics of the hot springs are average discharge 3–3.5 L/s, surface temperature 45–52°C, pH 8.9–9.3, and electrical
conductivity (EC) 620–698 μS/cm. The cold spring has a temperature of 12–13°C, pH 7.5–8.3, and EC 653–675 μS/cm. The hot waters
are Na-SO4 type, whereas the cold water is Ca-HCO3 type. Chemical geothermometers suggest that the reservoir temperature is around 80–100°C. The isotopic data (oxygen-18, deuterium
and tritium) indicate that the thermal waters are formed by local recharge and deep circulation of meteoric waters. 相似文献
7.
8.
The tectono-thermal history of the Lewisian Complex in South Harris (South Harris Complex) was inferred from its geologic and metamorphic characteristics. The lithological assemblages and geochemical features of the complex suggest that its precursory rocks were composed of the subduction-related accretionary complex formed in the palaeo convergent margin. The complex has suffered the ultra-high temperature (UHT) metamorphism that was contemporaneous with the igneous activity to make the South Harris Igneous Complex (SHIC) and the subsequent continent-continent collisional activity. A similar complex recording the geological processes of the subduction, the UHT metamorphism and the collision has been recognized in the Lapland-Kola belt and New Quebec in the Palaeoproterozoic. This suggests an assembly of micro-continents to form the Palaeoproterozoic supercontinent in the North Atlantic region. 相似文献
9.
Noble gases were measured both in bulk samples (stepped pyrolysis and total extraction) and in a HF/HCl residue (stepped pyrolysis and combustion) from the Klein Glacier (KLE) 98300 EH3 chondrite. Like the bulk meteorite and as seen in previous studies of bulk type 3 E chondrites (“sub-Q”), the acid residue contains elementally fractionated primordial noble gases. As we show here, isotopically these are like those in phase-Q of primitive meteorites, but elementally they are heavily fractionated relative to these. The observed noble gases are different from “normal” Q noble gases also with respect to release patterns, which are similar to those of Ar-rich noble gases in anhydrous carbonaceous chondrites and unequilibrated ordinary chondrites (with also similar isotopic compositions). While we cannot completely rule out a role for parent body processes such as thermal and shock metamorphism (including a later thermal event) in creating the fractionated elemental compositions, parent body processes in general seem not be able to account for the distinct release patterns from those of normal Q noble gases. The fractionated gases may have originated from ion implantation from a nebular plasma as has been suggested for other types of primordial noble gases, including Q, Ar-rich, and ureilite noble gases. With solar starting composition, the corresponding effective electron temperature is about 5000 K. This is lower than inferred for other primordial noble gases (10,000-6000 K). Thus, if ion implantation from a solar composition reservoir was a common process for the acquisition of primordial gas, electron temperatures in the early solar system must have varied spatially or temporally between 10,000 and 5000 K.Neon and xenon isotopic ratios of the residue suggest the presence of presolar silicon carbide and diamond in abundances lower than in the Qingzhen EH3 and Indarch EH4 chondrites. Parent body processes including thermal and shock metamorphism and a late thermal event also cannot be responsible for the low abundances of presolar grains. KLE 98300 may have started out with smaller amounts of presolar grains than Qingzhen and Indarch. 相似文献
10.
Intracellular partitioning of trace metals is critical to metal tolerance in aquatic organisms and may also influence metal trophic transfer in ecosystems. In this study, we tested the relevance of metal (Cd, Cu, Pb, and Zn) intracellular partitioning in prey as an indicator of metal trophic availability to benthic forage fish, mummichogs (Fundulus heteroclitus), in chronically metal-polluted salt marshes in New York, USA. Two common prey of mummichogs in the study area, Palaemonetes pugio and Nereis acuminata, generally stored increasingly higher proportions of non-essential metals (particularly Pb) in insoluble (less trophically available) cellular components, as the whole body burdens increased. In contrast, intracellular partitioning of essential metals (Cu and Zn) in invertebrate prey varied relatively little among sites. Differential Cd and Pb intracellular partitioning patterns within P. pugio among sites were significantly associated with Cd and Pb whole body burdens in mummichogs, respectively (i.e., prey-driven bioreduction of metals), while bioaccumulation of Cu and Zn in mummichogs was similar among populations. The findings in this study suggest that metal intracellular partitioning within prey may be partially responsible for metal trophic availability to a predator in metal-polluted habitats, while there was also evidence that some predator-dependent processes may offset differential trophic availabilities from prey. 相似文献