全文获取类型
收费全文 | 119篇 |
免费 | 9篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 26篇 |
地球物理 | 37篇 |
地质学 | 41篇 |
海洋学 | 6篇 |
天文学 | 10篇 |
综合类 | 1篇 |
自然地理 | 6篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 5篇 |
2012年 | 9篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
1999年 | 2篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有128条查询结果,搜索用时 15 毫秒
51.
52.
Ivana Conceição de Araújo Pinho Johildo Salomão Figueiredo Barbosa Angela Beatriz de Menezes Leal Hervé Martin Jean-Jacques Peucat 《Journal of South American Earth Sciences》2011,31(2-3):312-323
The studied tonalitic and trondhjemitic granulites are located in the SSE granulitic domain of the São Francisco craton, Bahia, Brazil, where they represent most of the southern part of the Archean and Paleoproterozoic Itabuna-Salvador-Curaçá Block (ISCB). Chemically, the tonalitic and trondhjemitic granulites belong to a low-K calc-alkaline suite; their REE patterns are steep with strong LREE/HREE fractionation and no significant Eu anomaly. Garnet-bearing mafic granulites that occur as enclaves in the tonalitic and trondhjemitic granulites were derived from basalts and/or gabbros of tholeiitic affinity. Geochemical modelling showed that the tonalitic and trondhjemitic granulites were produced by moderate fractional crystallization of an assemblage of hornblende and plagioclase, with subordinate amounts of magnetite, apatite, allanite and zircon. The garnet-bearing mafic granulites would be the source of the magmas that generated these rocks. Partial melting left a residue made up of plagioclase, garnet, orthopyroxene and hornblende. 相似文献
53.
54.
Finding which triangle in a planar or 2.5D triangle mesh contains a query point (so-called point location problem) is a frequent task in geosciences, especially when working with triangulated irregular network models. Usually, a large number of point locations has to be performed, and so there is a need for fast algorithms having minimal additional memory requirements and resistant to changes in the triangulation. So-called walking algorithms offer low complexity, easy implementation, and negligible additional memory requirements, which makes them suitable for such applications. In this article, we focus on these algorithms, summarize, and compare them with regard to their use in geosciences. Since such a summary has not been done yet, our article should serve those who are dealing with this problem in their application to decide which algorithm would be the best for their solution. Moreover, the influence of the triangulation type on the number of the visited triangles is discussed. 相似文献
55.
Fausto Grassa Giorgio Capasso Rocco Favara Salvatore Inguaggiato 《Pure and Applied Geophysics》2006,163(4):781-807
Hydrochemical (major and some minor constituents), stable isotope ( and , δ13CTDIC total dissolved inorganic carbon) and dissolved gas composition have been determined on 33 thermal discharges located throughout
Sicily (Italy) and its adjacent islands. On the basis of major ion contents, four main water types have been distinguished:
(1) a Na-Cl type; (2) a Ca-Mg > Na-SO4-Cl type; (3) a Ca-Mg-HCO3 type and (4) a Na-HCO3 type water. Most waters are meteoric in origin or resulting from mixing between meteoric water and heavy-isotope end members.
In some samples, δ18O values reflect the effects of equilibrium processes between thermal waters and rocks (positive 18O-shift) or thermal waters and CO2 (negative 18O-shift). Dissolved gas composition indicates the occurrence of gas/water interaction processes in thermal aquifers. N2/O2 ratios higher than air-saturated water (ASW), suggest the presence of geochemical processes responsible for dissolved oxygen
consumption. High CO2 contents (more than 3000 cc/litre STP) dissolved in the thermal waters indicate the presence of an external source of carbon
dioxide-rich gas. TDIC content and δ13CTDIC show very large ranges from 4.6 to 145.3 mmol/Kg and from –10.0‰ and 2.8‰, respectively. Calculated values indicate the significant
contribution from a deep source of carbon dioxide inorganic in origin. Interaction with Mediterranean magmatic CO2 characterized by heavier carbon isotope ratios ( value from -3 to 0‰ vs V-PDB (CAPASSO et al., 1997, GIAMMANCO et al., 1998; INGUAGGIATO et al., 2000) with respect to MORB value and/or input of CO2-derived from thermal decomposition of marine carbonates have been inferred. 相似文献
56.
Marco Mucciarelli Marcello Bianca Rocco Ditommaso Marco Vona Maria Rosaria Gallipoli Alessandro Giocoli Sabatino Piscitelli Enzo Rizzo Matteo Picozzi 《Bulletin of Earthquake Engineering》2011,9(3):825-840
In San Gregorio (L’Aquila, Italy) a three-story, reinforced concrete (RC) building had the first floor collapsed following
the earthquake of April 6, 2009. The remaining two stories fell with a displacement in the horizontal projection of about
70 cm. This unusual behaviour is made more puzzling by the fact that buildings located at a short distance and with similar
features had little or no damage reported. To understand the causes of the collapse we performed strong motion recordings,
microtremor measurements, a detailed geological survey, a high-resolution geo-electrical tomography, a borehole with a down-hole
test. On the building we performed a geometrical survey and laboratory tests on concrete cores. The acceleration and noise
recordings have shown a high amplification with uphill-downhill direction. The geological survey has revealed the presence
of co-seismic fractures on stiff soils. Geo-electrical tomography has shown an unexpected, strong discontinuity just below
the building. Taking advantage of excavations in adjacent lots, we have highlighted rare cataclastic decimetric bands with
a very low resistance material incorporated in well-stratified calcarenites. The same soft material has been founded in the
borehole down to 17 m from ground level, showing a shear wave velocity that starts at 250 m/s, increases with depth and has
an abrupt transition in calcarenites at 1,150 m/s. The surface geophysical measurements in the vicinity of the site have not
shown similar situations, with flat HVSR curves as expected for a rock outcrop, except for a lateral extension of the soft
zone. The analysis on the quality of the building materials has yielded values higher than average for the age and type of
construction, and no special design or construction deficiencies have been observed. A strong, peculiar site effect thus appears
to be the most likely cause of the damage observed. 相似文献
57.
Jakub Jirásek Lada Hýlová Martin Sivek Janusz Jureczka Karel Martínek Ivana Sýkorová Mark Schmitz 《International Journal of Earth Sciences》2013,102(4):989-1006
The Main Ostrava Whetstone (MOW) is an important lithostratigraphic horizon of the Late Carboniferous sedimentary fill of the late Palaeozoic foreland Upper Silesian Basin. It is the largest and best-identified volcanogenic horizon in the basin, reaching thicknesses of 15.3 m and occupying an area of ca 2,973 km2 and a volume after lithification of 9.24 km3. It consists of volcanic materials transported to the basin probably by an aeolian process. Just after sedimentation, these materials were redeposited a short distance away in a shallow water environment. Granularity corresponds to a range from argillaceous siltstones to fine-grained sandstones. The components are dominated by glass shards replaced by clay minerals (mixed illite–smectite structures) in addition to quartz of volcanogenic and terrigenous origins. Sanidine and a plagioclase close to albite are also present. The sedimentary structures, micro-structures and composition of the MOW indicate variable and dynamic hydrodynamic conditions. The MOW represents a series of flooding events, which could be connected with unusual rainfall. Such major flooding events were most likely induced by volcanic eruptions. The available drill-core log data were used to construct a digital model of the whetstone, which showed an east–west zonality in the thicknesses, with the majority being synsedimentary. CA-TIMS U–Pb dating the volcanogenic zircons yields an age of 327.35 ± 0.15 Ma. The source location of the volcanogenic material is not clear; however, it is presumed to have been located in the west of the Upper Silesian Basin. 相似文献
58.
Aridity in Vojvodina, Serbia 总被引:2,自引:1,他引:1
Ivana Hrnjak Tin Lukić Milivoj B. Gavrilov Slobodan B. Marković Miroslava Unkašević Ivana Tošić 《Theoretical and Applied Climatology》2014,115(1-2):323-332
For investigating aridity in Vojvodina, two parameters were used: the De Martonne aridity index and the Pinna combinative index. These indices were chosen as the most suitable for the analysis of climate in Vojvodina (a region in northern part of Serbia). Also, these indices were calculated from data obtained from 10 meteorological stations for the period from 1949 to 2006. The spatial distribution of the annual and seasonal De Martonne and the Pinna combinative indices as well as the mean monthly values of the De Martonne index and aridity trends of these indices are presented. There were two, four, and five types of climate on a yearly, seasonal, and monthly basis in Vojvodina, according to the De Martonne climate classification which consists of a total of seven types. In addition, semi-humid and humid climate types were represented in the region, on a yearly basis. The winter season was dominated by wetter types of climate, while the summer season was characterized by drier ones. During the spring and autumn seasons, there were types of climate which range between both aforementioned types. Two out of three climate types, which can be identified using the Pinna combinative index, were registered in Vojvodina region. The most dominant climate type was the semidry Mediterranean with formal Mediterranean vegetation, while the humid type was only identified in one small part of southwestern Vojvodina. The calculated values of both aridity indices showed that there were no annual trends. Therefore, it can be considered that there were no recent aridity changes during the observed period. For paleoclimate, the general story is more complex. The lack of aridity trends in the recent period from 1949 to 2006 supports the fact that Vojvodina has very well preserved loess–palaeosol sequences from the Middle and Late Pleistocene, which indicates that crucial point for their preservation was caused by the weak aridity variability in the region. 相似文献
59.
60.
Monitoring the structural dynamic response of a masonry tower: comparing classical and time-frequency analyses 总被引:2,自引:2,他引:0
Rocco Ditommaso Marco Mucciarelli Stefano Parolai Matteo Picozzi 《Bulletin of Earthquake Engineering》2012,10(4):1221-1235
The monitoring of the evolution of structural dynamic response under transient loads must be carried out to understand the physical behaviour of building subjected to earthquake ground motion, as well as to calibrate numerical models simulating their dynamic behaviour. Fourier analysis is one of the most used tools for estimating the dynamic characteristics of a system. However, the intrinsic assumption of stationarity of the signal imposes severe limitations upon its application to transient earthquake signals or when the dynamic characteristics of systems change over time (e.g., when the frequency of vibration of a structure decreases due to damage). Some of these limitations could be overcome by using the Short Time Fourier Transform (STFT). However, the width of the moving window adopted for the analysis has to be fixed as a function of the minimum frequency of interest, using the best compromise between resolution in both the time and frequency domains. Several other techniques for time-frequency analysis of seismic signals recorded in buildings have been recently proposed. These techniques are more suitable than the STFT for the application described above, although they also present drawbacks that should be taken into account while interpreting the results. In this study, we characterize the dynamic behaviour of the Falkenhof Tower (Potsdam, Germany) while forced by ambient noise and vibrations produced by an explosion. We compare the results obtained by standard frequency domain analysis with those derived by different time-frequency methods. In particular, the results obtained by the standard Transfer Function method, Horizontal to Vertical Spectral Ratio (HVSR), Short Time Fourier Transform (STFT), Empirical Mode Decomposition (EMD) and S-Transform are discussed while most of the techniques provide similar results, the EMD analyses suffer some problems derived from the mode mixing in most of the Intrinsic Mode Functions (IMFs). 相似文献