全文获取类型
收费全文 | 329篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 19篇 |
地球物理 | 101篇 |
地质学 | 93篇 |
海洋学 | 23篇 |
天文学 | 69篇 |
综合类 | 1篇 |
自然地理 | 26篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 18篇 |
2015年 | 14篇 |
2014年 | 10篇 |
2013年 | 11篇 |
2012年 | 17篇 |
2011年 | 13篇 |
2010年 | 8篇 |
2009年 | 26篇 |
2008年 | 16篇 |
2007年 | 23篇 |
2006年 | 10篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 11篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 8篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1951年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有339条查询结果,搜索用时 15 毫秒
71.
Alberto?RenzulliEmail author Stefano?Del?Moro Michele?Menna Patrizia?Landi Marco?Piermattei 《Bulletin of Volcanology》2009,71(7):795-813
We describe the mineralogy, geochemistry, and mesomicrostructure of fresh subvolcanic blocks erupted during the 5 April 2003
paroxysm of Stromboli (Aeolian Islands, Italy). These blocks represent ∼50 vol.% of the total erupted ejecta and consist of
fine- to medium-grained basaltic lithotypes ranging from relatively homogeneous dolerites to strongly or poorly welded magmatic
breccias. The breccia components are represented by angular fragments of dolerites entrapped in a matrix of vesiculated (lava-like
to scoriae) crystal-rich (CR) basalt. All of the studied blocks are cognates with the CR basalt of the normal Strombolian
activity or lavas and they are often coated by a few-centimeter thick layer of crystal-poor (CP) basaltic pumice erupted during
the paroxysm. We suggest that they result from the rapid increase of pressure and related subvolcanic rock failure that occurred
shortly before the 5 April 2003 explosion, when the uppermost portion of the edifice inflated and suffered brecciation as
the result of the sudden rise of the gas-rich CP basalt that triggered the eruption. Dolerites and magmatic matrix of the
breccias show major and trace element compositions that match those of the CR basalts erupted during normal Strombolian activity
and effusive events at Stromboli volcano. Dolerites consist of (a) phenocrysts normally found in the CR basalts and (b) late-stage
magmatic minerals such as sanidine, An60-28 plagioclase, Fe–Mn-rich olivines (Fo68-48), phlogopite, apatite, and opaque mineral pairs (magnetite and ilmenite), most of which are never found both in lava flows
and scoriae erupted during the persistent explosive activity that characterizes typical Strombolian behavior. Subvolcanic
crystallization of the Stromboli CR magma, leading to slowly cooled equivalents of basalts, could result from transient drainage
of the magma from the summit craters to lower levels. Fingering and engulfing of the material that collapsed from the summit
crater floor into the shallow basaltic system during the late evening of 28 December 2002 coupled with the short break in
the summit persistent explosions between December 2002 and March 2003 permitted the CR magma pockets to solidify as dolerites,
which were confined to the uppermost portion of the system and thus not involved in the ongoing flank effusive activity. Crystal
size distribution of the basaltic blocks and crystallization of the finer-grained (<0.1 mm) mafic minerals of the dolerites
over a time interval of ∼100 days closely agrees with the above interpretation. Vesicle filling (miarolitic cavities) locally
found in some dolerites, with minerals deposited as vapor-phase crystallization is a result of continuous gas percolation
through the rocks of the uppermost portion of the volcanic system. Poorly welded magmatic breccias formed during syn-eruptive processes of 5 April 2003, when the paroxysm strongly shattered the shallow subvolcanic system and many dolerite
fragments were entrapped in the CR magma. In contrast, the high degree of welding between the dolerite clasts and the CR basaltic
matrix in the strongly welded magmatic breccias provides a snapshot of subvolcanic intrusions of the CR basalt into the dolerite
when, after a 2-month break in activity, CR magmas started to rise again to the summit craters. Blocks similar to these subvolcanic
ejecta of 5 April 2003 were also erupted during previous paroxysms (e.g., 1930) suggesting that changes in the usual Strombolian
activity (e.g., short breaks in the persistent mild explosions and/or flank effusive activity) lead to transient crystallization
of dolerites in the shallow plumbing system. 相似文献
72.
The effects of waterborne nitrite (3 mg/l NO2) on channel catfish were studied to evaluate changes in hematological parameters and phase I-II biotransformation in liver slices. Nitrite-exposed fish had significantly higher methemoglobin, blood and liver nitrite, and significantly lower pO2 than control fish. Total phase I-mediated metabolism of 7-ethoxycoumarin (EC) was not altered in nitrite-exposed fish compared with control fish (291 +/- 43 and 312 +/- 20 pmol/mg/h, respectively). However, phase II glucuronosyltransferase-mediated metabolism of 7-hydroxycoumarin (HC), both as a phase I metabolite of EC and as a parent substrate, was elevated in nitrite-exposed fish (204 +/- 17 and 1007 +/- 103 pmol/mg/h, respectively) as compared to control fish (149 +/- 14 and 735 +/- 87 pmol/mg/h) (P < 0.05). Sulfotransferase-mediated metabolism of HC (as a metabolite of EC and as a parent substrate) was not notably altered in nitrite-exposed fish (95 +/- 16 and 617 +/- 33 pmol/mg protein/h, respectively) as compared with control fish (118 +/- 24 and 575 +/- 55 pmol/mg/h, respectively). These studies indicate that in vivo nitrite exposure and associated changes in hematological parameters do not appear to affect hepatic phase I EC biotransformation in channel catfish. However, subtle but significant changes in phase II glucuronidation, but not sulfation activity, were observed. The mechanism of these alterations is unclear. However, the data suggest that environmentally realistic concentrations of nitrite may affect the dynamics of conjugative metabolism in exposed fish. 相似文献
73.
Phase diversity techniques are robust post-processing tools for image enhancement and correction of telescopic and atmospheric
induced aberrations. We present results obtained applying the Partitioned Phase-Diverse Speckle (PPDS) technique to images
acquired at THEMIS. We also present an image quality estimator based on image power spectrum content we developed in order
to automatically evaluate the results of large amount of data. 相似文献
74.
Inversion techniques of the radiative transfer equation for polarized light are presented as one of the best current procedures to infer the vector magnetic field, as well as other quantities governing the physical state of the atmospheric layers that photons are coming from. Several characteristics of the various available inversion procedures are pointed out. They are mostly based on the diagnostic contents of the spectral lines as well as on the main hypotheses assumed in these procedures. In particular, the role of gradients in the atmospheric quantities is emphasized as of paramount importance in any diagnostic analysis and, hence, in any interpretation of inversion results. 相似文献
75.
Strain rates and Euler poles for various subregions of the Alpine Mediterranean region were calculated by using global navigation satellite system data from permanent stations. The main scope of the study is to compare and analyze strain rate maps that were calculated using different approaches. This area presents a complex tectonic setting due to the interaction of the Eurasian and Nubian plates. The horizontal velocity gradient tensor was computed starting from a new set of site velocities determined by using continuous long-series geodetic data, state-of-the-art antenna calibrations and recomputed precise orbits. Geodesy provides velocities for a sparsely distributed, discrete number of sites, while deformation has a spatially continuous distribution. For this reason, the interpolation method and the geometric approach to the problem play a fundamental role in the estimation of the strain rate field. In the present study, principal deformation axes and principal angle were estimated by applying two different approaches: the Delaunay triangulation and a grid solution. Both methods produce results with broad coherence, providing new information about the deformation throughout the entire study area. Moreover, an evaluation and analysis of Euler poles related to the different velocity patterns, give complementary information to reconstruct the active deformation in the Mediterranean area. 相似文献
76.
77.
The Sierra de Cameros is an intracontinental orogen and represents the north‐western part of the Iberian Range in Northern Spain. It comprises a thick sequence of syn‐rift continental sediments (mainly sandstones and carbonates) deposited during lower Cretaceous times. A unique characteristic of the Sierra de Cameros in relation to the rest of the Iberian Range is the presence of low‐grade metamorphism in certain parts of the basin, an event that predates basin inversion. This paper describes the presence, textural relationships and geochemical aspects of authigenic and/or metamorphic monazite within different lithologies from the deepest parts of the basin. Sensitive high resolution ion microprobe (SHRIMP) U–Pb dating of monazite records the presence of two age populations: the first with 206Pb/238U ages ranging from 122 to 116 Ma which is considered as diagenetic in origin, whilst the second is dated at 99 ± 2 Ma and postdates the metamorphic climax. 相似文献
78.
N. Bucciantini E. Quataert B. D. Metzger T. A. Thompson J. Arons L. Del Zanna 《Monthly notices of the Royal Astronomical Society》2009,396(4):2038-2050
We use ideal axisymmetric relativistic magnetohydrodynamic simulations to calculate the spin-down of a newly formed millisecond, B ∼ 1015 G , magnetar and its interaction with the surrounding stellar envelope during a core-collapse supernova (SN) explosion. The mass, angular momentum and rotational energy lost by the neutron star are determined self-consistently given the thermal properties of the cooling neutron star's atmosphere and the wind's interaction with the surrounding star. The magnetar drives a relativistic magnetized wind into a cavity created by the outgoing SN shock. For high spin-down powers (∼1051 –1052 erg s−1 ) , the magnetar wind is superfast at almost all latitudes, while for lower spin-down powers (∼1050 erg s−1 ) , the wind is subfast but still super-Alfvénic. In all cases, the rates at which the neutron star loses mass, angular momentum and energy are very similar to the corresponding free wind values (≲30 per cent differences), in spite of the causal contact between the neutron star and the stellar envelope. In addition, in all cases that we consider, the magnetar drives a collimated (∼5–10°) relativistic jet out along the rotation axis of the star. Nearly all of the spin-down power of the neutron star escapes via this polar jet, rather than being transferred to the more spherical SN explosion. The properties of this relativistic jet and its expected late-time evolution in the magnetar model are broadly consistent with observations of long duration gamma-ray bursts (GRBs) and their associated broad-lined Type Ic SN. 相似文献
79.
In order to define adequate prevention measures and to manage landslide emergencies, real-time monitoring is required. This
paper presents two different applications of the remote sensing technique: the ground-based synthetic aperture radar interferometry,
here proposed as a monitoring and early warning support for slope instability. Data acquisitions carried out through a ground-based
synthetic aperture radar interferometer, operating in Ku band, installed in front of the observed slopes, are discussed. Two case studies, based on the use of the same apparatus
(formerly developed by the Joint Research Center of the European Commission and by Ellegi-LiSALab srl), are reported: the
first one concerns the monitoring of a large landslide, named Ruinon (Valfurva, Italy). The second one deals with the monitoring
of the NW unstable slope in the Stromboli island aimed to implementing an early warning system. Acquired interferometric data
are processed to provide displacements and velocity maps of the monitored area. The monitoring services ongoing on the Ruinon
landslide and on Stromboli demonstrate the capability of this technique to operate in different operative settings (i.e.,
different phenomena and geological framework) and for different aims (monitoring for prevention, early warning, and emergency
assessment). This methodology has also been proved by national and regional authorities of civil protection in order to provide
a real-time monitoring for emergency management. 相似文献
80.
Felipe García-Rodríguez Laura Del Puerto Carola Castieira Hugo Inda Roberto Bracco Peter Spechmann Burkhard Wilhelm Scharf 《Limnologica》2001,31(3)
Physical, chemical and biological data from a sedimentary profile of Rocha lagoon (Uruguay) are presented. Analyses of silica remains showed that opal phytoliths, diatoms, sponge spicules and chrysophyte cysts were the most important contributors to biogenic silica. Organic matter, total nitrogen and total phosphorus were used to infer past trophic development. Physical analysis of sediments allowed us to identify five lithological units related to sea level variation and climatic events. 相似文献