全文获取类型
收费全文 | 132篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 3篇 |
地球物理 | 41篇 |
地质学 | 66篇 |
海洋学 | 4篇 |
天文学 | 18篇 |
自然地理 | 5篇 |
出版年
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1998年 | 5篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有139条查询结果,搜索用时 125 毫秒
1.
The inception and growth of the active Carpino-Le Piane Basin Fault System (CLPBFS; central-southern Apennines, Italy) was analysed with respect to the neighbouring Isernia and Surrounding (ISFS) and Boiano Basin (BBFS) extensional Fault Systems. 39Ar–40Ar dating showed that the BBFS was already active 649 ± 21 ka bp and that the ISFS was active at least 476 ±10 ka bp , whereas the activity of the CLPBFS started certainly later than 253 ± 22 ka bp , and very probably as recently as <28 ka bp . These ages, combined with structural data (geometry and kinematics of the fault systems), indicate that the inception and development of the CLPBFS could be strictly related to the stress changes caused by earthquakes occurring on the BBFS. 相似文献
2.
Hydrogeochemical investigations and groundwater provinces of the Friuli Venezia Giulia Plain aquifers,northeastern Italy 总被引:2,自引:0,他引:2
Water resources are a key factor, particularly for the planning of the sustainable regional development of agriculture, as
well as for socio-economic development in general. A hydrochemical investigation was conducted in the Friuli Venezia Giulia
aquifer systems to identify groundwater evolution, recharge and extent of pollution. Temperature, pH, electric conductivity,
total dissolved solids, alkalinity, total hardness, SAR, Ca2+, Na+, K+, Mg2+, Cl−, SO4
2−, NO3
−, HCO3
−
, water quality and type, saturation indexes and the environmental stable isotope δ18O were determined in 149 sampling stations. The pattern of geochemical and oxygen stable isotope variations suggests that
the sub-surface groundwater (from phreatic and shallow confined aquifers) is being recharged by modern precipitations and
local river infiltrations. Four hydrogeological provinces have been recognised and mapped in the Friuli Venezia Giulia Plain
having similar geochemical signatures. These provinces have different degrees of vulnerability to contamination. The deep
confined groundwater samples are significantly less impacted by surface activities; and it appears that these important water
resources have very low recharge rates and would, therefore, be severely impacted by overabstraction. 相似文献
3.
Rosa Nappi Giuliana Alessio Giovanni Bronzino Carlo Terranova Giuseppe Vilardo 《Natural Hazards》2008,45(1):73-85
In this article the implementation and potential of the Seismotectonic Information System of the Campania Region (SISCam)
are described, in particular an application of this Web-based GIS system to the seismotectonic analysis of the Sannio area
(Southern Apennines) is performed. WEB-GIS technologies greatly contribute to both the environmental monitoring and the disaster
management of areas affected by high natural risks. Specifically the SISCam system has been developed with the aim of providing
easy access and fast diffusion, through Internet technology, of the most significant geological, geophysical, and territorial
data relative to the Campania Region. The Sannio area has been selected as our application example because it is among the
most active seismic regions in Italy. This portion of the Southern Apennines which was hit by the June 5, 1688 strong earthquake
(M
W = 6.7, CPTI 1999) and by some low- and moderate-energy seismic sequences (1990–1992, 1997), is characterized by a complex
inherited tectonic setting and low-tectonic deformation rates that hide the seismogenic sources position. Since this case
study turned out to be complicated, the use of the SIScam WEB-GIS has become indispensable because it allowed us to visualize,
integrate and analyze all the data available, in order to obtain an accurate and direct picture of the seismotectonic setting
of the area. Moreover, a different approach of data analysis was necessary, due to the lack of up-to-date neotectonic and
structural data; therefore, the operation of this GIS system enabled us to process and generate some original informative
layers, through image analysis, such as new structural lineaments represented on a map of the potential active faults of the
area, which has been the final result of our application, as a contribution to new knowledge about the local seismic risk
parameters. 相似文献
4.
5.
L. Bassani R. C. Butler A. J. Dean G. Di Cocco A. Della Ventura F. Perotti G. Villa 《Astrophysics and Space Science》1982,82(2):311-316
During a balloon flight in September 1979 of the MISO low-energy -ray telescope, the BL Lac-object MkN 501 was studied in the hard X-ray range above 30 keV and in the low energy -ray range up to 19 MeV. No statistically significant X- and -ray fluxes were detected. The implications of the upper limits obtained are discussed in the light of the relativistic jet theories recently proposed. 相似文献
6.
Holocene climate variability in Sicily from a discontinuous stalagmite record and the Mesolithic to Neolithic transition 总被引:2,自引:0,他引:2
Silvia Frisia Andrea Borsato Augusto Mangini Christoph Sptl Giuliana Madonia Ugo Sauro 《Quaternary Research》2006,66(3):388-400
Fabric and stable isotopic composition of a Holocene stalagmite (CR1) from a cave in northern Sicily record changes in paleorainfall in the early Holocene. High δ13C stable isotope values in the calcite deposited from ca. 8500 to ca. 7500 yr ago are interpreted as reflecting periods of high rainfall. The wet phase was interrupted by two periods of multi-century duration characterized by relatively cool and dry winters centered at ca. 8200 and ca. 7500 yr ago, highlighted by low δ13C and δ18O values. A high variability of δ13C values is recorded from ca. 7500 to ca. 6500 yr ago and indicates that the transition from a pluvial early Holocene to the present-day climate conditions was punctuated by decadal-scale periods of relatively dry winters. In northern Sicily, the traditional elements of the Neolithic appear at ca. 7700 yr ago. It is possible that changes in rainfall influenced the passage from hunter-gathering to farming and sheep-herding economies. 相似文献
7.
Laura Federico Giovanni Capponi Laura Crispini Marco Scambelluri Igor M. Villa 《Earth and Planetary Science Letters》2005,240(3-4):668-680
We present 39Ar–40Ar dating of phengite, muscovite and paragonite from a set of mafic and metasedimentary rocks sampled from the high-pressure (HP) metaophiolites of the Voltri Group (Western Alps) and from clasts in the basal layer conglomerates from the Tertiary molasse which overlie the high-pressure basement. The white mica-bearing rocks display peak eclogitic and blueschist-facies parageneses, locally showing complex greenschist-facies replacement textures. The internal discordance of age spectra is proportional to the chemical complexity of the micas. High-Si phengites from eclogite clasts record a 39Ar–40Ar age of ca. 49 Ma for the eclogite stage and ca. 43 Ma for the blueschist retrogression; phengites from a blueschist basement sample yield an age of ca. 40 Ma; low-Si muscovite from a metasediment dates the formation of the greenschist paragenesis at ca. 33 Ma. Our data indicate that the analyzed samples reached high-pressure conditions at different times over a time-span of c.a. 10 Ma. Subduction was continuing during exhumation and blueschist retrograde re-equilibration of higher-pressure, eclogite-facies rocks. This process kept the isotherms depressed, allowing the older HP-rocks to escape thermal re-equilibration. Our results, added to literature data, fit a tectonic model of a subduction–exhumation cycle, with different tectonic slices subducted at different times from Early Eocene until the Eocene–Oligocene boundary. 相似文献
8.
José M. Carcione Davide Gei Giuliana Rossi Gianni Madrussani 《Geophysical Prospecting》2005,53(6):803-810
We estimate the concentration of gas hydrate and free gas at an area located to the north of the Knipovich Ridge (western Svalbard margin). The method is based on P-wave velocities computed by reflection tomography applied to multicomponent ocean-bottom seismometer data. The tomographic velocity field is fitted to theoretical velocities obtained from a poro-elastic model based on a Biot-type approach (the interaction between the rock frame, gas hydrate and fluid is modelled from first physical principles). We obtain average hydrate concentrations of 7% and maximum free-gas saturations of 0.4% and 9%, depending on the saturation model. 相似文献
9.
Roberto Villa Verde 《地震工程与结构动力学》1991,20(3):223-241
Presented herein are the results of a study carried out to investigate the prevalent factors that contributed to the collapse of the upper floors of a large number of buildings during the earthquake of September 19, 1985, in Mexico City. The study involves the review of the available data from such collapses, the identification of common characteristics among the buildings that suffered such type of collapse, the design of a typical 10-storey reinforced concrete frame structure according to the 1976 Mexico City building code, and the non-linear analysis of one of its frames under one of the accelerograms from the earthquake. It is found that in many cases the upper floor collapses might have occurred because the large accelerations and long duration of the earthquake induced in the failed buildings the formation of plastic hinges at their upper columns, and because these plastic hinges in turn induced the lateral instability of the affected storeys and the ones above them. It is also found that in some structures this failure mechanism can occur after plastic hinges are formed in most of their beams, and that it may result from the consequent elongation of their natural periods, their response in a second or third mode and in resonance with the ground motion that excites them, and their vibration in a mode not considered to be the predominant one in their design. 相似文献
10.
Ar analyses are reported for five coarse-grained, Ca-Al-rich inclusions from the Allende meteorite. The samples were neutron-irradiated in individual evacuated ampoules, and the Ar gas in the ampoules as well as the samples was analyzed. A large fraction (up to 60%) of the39Ar from39K (n, p) reactions was lost out of the inclusions into the ampoules. The39Ar losses resulted in substantial increases in the apparent40Ar-39Ar ages of the samples.39Ar recoil loss during neutron-irradiation is a major effect and must be accounted for in40Ar-39Ar dating. All of the Allende inclusions studied contained substantial trapped36Ar. The origin of the trapped36Ar is unknown, and the possible presence of trapped40Ar cannot be excluded. Ar measurements on Allende inclusions which have yielded anomalously old ages must be re-examined in the context of39Ar recoil loss and possible contributions of trapped40Ar. Allende inclusions appear on both accounts to be poor candidates to search for relicts of presolar materials with well-defined K/Ar ages. 相似文献