首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   101篇
  免费   0篇
测绘学   4篇
大气科学   3篇
地球物理   17篇
地质学   27篇
海洋学   9篇
天文学   37篇
自然地理   4篇
  2021年   1篇
  2020年   3篇
  2019年   2篇
  2018年   2篇
  2017年   5篇
  2016年   5篇
  2014年   1篇
  2013年   3篇
  2012年   6篇
  2011年   11篇
  2010年   6篇
  2009年   9篇
  2008年   3篇
  2007年   5篇
  2006年   9篇
  2005年   3篇
  2004年   5篇
  2003年   5篇
  2002年   1篇
  2001年   1篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1987年   1篇
  1984年   2篇
  1983年   3篇
排序方式: 共有101条查询结果,搜索用时 15 毫秒
41.
The use of geophysical methods in metrology is a significant tool within the wide research topic of landscape archaeology context. Since 2011, the Ancient Appia Landscapes Project aims to recognize dynamics, shapes and layout of the ancient settlement located along the Appia road east of Benevento, and cyclical elements and human activities that influenced the choice of landscapes. The integration of geophysical data with an archaeological infra-site analysis allowed us to investigate the area of Masseria Grasso, about 6 km from Benevento (Campania region, Italy). In this framework, an archaeogeophysical approach (Geomagnetic and Ground Penetrating Radar) was adopted for detecting anomalies potentially correlated with buried archaeological evidences. The geomagnetic results have given a wide knowledge of buried features in a large survey highlighting significant anomalies associated with the presence of buildings, roads and open spaces. These geophysical results permitted us to define the first archaeological excavations and, successively, a detailed Ground Penetrating Radar approach has been provided highlighting the rooms and paved spaces. The overlap between archaeological dataset and geophysical surveys has also allowed recognizing the path of the ancient Appia road near the city of Benevento and hypothesize the settlement organization of the investigated area, which has been identified with the ancient Nuceriola.  相似文献   
42.
We present an accurate characterization of the particle background behaviour on XMM-Newton based on the entire EPIC archive. This corresponds to the largest EPIC data set ever examined. Our results have been obtained thanks to the collaboration between the FP7 European program EXTraS and the ESA R&D ATHENA activity AREMBES. We used as a diagnostic an improved version of the diagnostic which compares the data collected in unexposed region of the detector with the region of the field of view in the EPIC-MOS. We will show that the in Field-of-View excess background is made up of two different components, one associated to flares produced by soft protons and the other one to a low-intensity background. Its origin needs to be further investigated.  相似文献   
43.
XMM-Newton is the direct precursor of the future ESA ATHENA mission. A study of its particle-induced background provides therefore significant insight for the ATHENA mission design. We make use of ~12 years of data, products from the third XMM-Newton catalog as well as FP7 EXTraS project to avoid celestial sources contamination and to disentangle the different components of the XMM-Newton particle-induced background. Within the ESA R&D AREMBES collaboration, we built new analysis pipelines to study the different components of this background: this covers time behavior as well as spectral and spatial characteristics.  相似文献   
44.
Results of observations of 14 asteroids are reported; all of them, except 181 Eucharis, have been previously observed at least once. V photoelectric lightcurves were obtained from September 1982 to June 1983 at the Astronomical Observatory of Torino and at the Astrophysical Observatory of Catania. Part of this program aims to obtain complete lightcurves and, when possible, phasecurve information and to determine amplitudes and V magnitudes at different longitudes for a selected group of asteriods, in order to enlarge the set of known rotational axis directions.  相似文献   
45.
Within the framework of a very long multifrequency campaign of coordinated, and very often simultaneous, observations of the transient X-ray/Be system A 0535+26/HDE 245770, we present a summary of this large collection of data taken with IUE and ASTRON satellites as well as with many ground-based telescopes in optical and IR regions.In this paper we emphasize the study of the physics and dynamics of the mass transfer at periastron and subsequent X-ray flaring, which is a typical problem of the X-ray/Be binary system class.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   
46.
Debris flows are among the most hazardous and unpredictable processes whose hazard evaluation requires an understanding of the processes that govern sediment supply, sediment bulking, flow volume, and deposition. In line with this challenge, we estimate the net soil redistribution rates in an area characterized by recurrent instability phenomena using 137Cs as a tracer for monitoring soil dynamics. An extension of this method by applying it to the case of major landslides is addressed. Specifically, surveys of soil 137Cs content at sites in the Pizzo d’Alvano massif (Italy), where a set of particularly damaging landslides occurred on 5–6 May 1998, are reported. Being this region prone to debris flows, two zero-order basins are examined, one of which experienced a landslide event. In that basin deposition is observed, whereas the other shows a net loss of soil. These results appear to be relevant, particularly because the rate of hollow filling could be correlated with the magnitude and/or frequency of debris flow occurrence or with some measure of the hazard presented by individual gullies.  相似文献   
47.
Evidences of landslide earthquake triggering due to self-excitation process   总被引:2,自引:0,他引:2  
The basin-like setting of stiff bedrock combined with pre-existing landslide masses can contribute to seismic amplifications in a wide frequency range (0–10 Hz) and induce a self-excitation process responsible for earthquake-triggered landsliding. Here, the self-excitation process is proposed to justify the far-field seismic trigger of the Cerda landslide (Sicily, Italy) which was reactivated by the 6th September 2002 Palermo earthquake (M s = 5.4), about 50 km far from the epicentre. The landslide caused damage to farm houses, roads and aqueducts, close to the village of Cerda, and involved about 40 × 106 m3 of clay shales; the first ground cracks due to the landslide movement formed about 30 min after the main shock. A stress–strain dynamic numerical modelling, performed by FDM code FLAC 5.0, supports the notion that the combination of local geological setting and earthquake frequency content played a fundamental role in the landslide reactivation. Since accelerometric records of the triggering event are not available, dynamic equivalent inputs have been used for the numerical modelling. These inputs can be regarded as representative for the local ground shaking, having a PGA value up to 0.2 m/s2, which is the maximum expected in 475 years, according to the Italian seismic hazard maps. A 2D numerical modelling of the seismic wave propagation in the Cerda landslide area was also performed; it pointed out amplification effects due to both the structural setting of the stiff bedrock (at about 1 Hz) and the pre-existing landslide mass (in the range 3–6 Hz). The frequency peaks of the resulting amplification functions (A(f)) fit well the H/V spectral ratios from ambient noise and the H/H spectral ratios to a reference station from earthquake records, obtained by in situ velocimetric measurements. Moreover, the Fourier spectra of earthquake accelerometric records, whose source and magnitude are consistent with the triggering event, show a main peak at about 1 Hz. This frequency value well fits the one amplified by the geological setting of the bedrock in correspondence with the landslide area, which is constituted of marly limestones and characterised by a basin-like geometry.  相似文献   
48.
We analyze tide gauge records at four stations of the ISPRA network located in the Adriatic Sea basin (Eastern Italy), namely, going from North to South: Trieste, Ancona, Ortona and Otranto. We use linear and nonlinear methods in the frequency and time domains, including spectral and Independent Component Analysis (ICA), inter-times occurrence, and phase space embedding dimension evaluation. We show that four tidal constituents can be extracted by ICA and interpreted as coherent self-sustained oscillations. Finally, we show that these constituents can be reproduced by adopting a simple nonlinear oscillatory model that generalizes classical Andronov oscillator with the inclusion of a time dependent pumping.  相似文献   
49.
The Tunnel Sealing Experiment (TSX) was a full‐scale in situ demonstration of technology for constructing nearly water tight‐seals in excavations through crystalline rock deep below the surface of the earth. The experiment has been carried out at Atomic Energy of Canada Limited's (AECL's) Underground Research Laboratory near Lac du Bonnet, Canada, in support of international programs for geologic disposal of radioactive waste. The TSX, with partners from Canada, Japan, France and the United States, was carried under conditions of high pressure (up to 4 MPa) and elevated temperature (up to 85°C). Comparing numerical model predictions with eight years of data collected from approximately 900 sensors was an important component of this experiment. Model of Transport In Fractured/porous Media (MOTIF), a finite element computer program developed by AECL for simulating fully coupled or uncoupled fluid flow, solute transport and heat transport, was used to model both the ambient temperature and heated phases of the TSX. The plan to heat the water in the TSX to 85°C was developed using model predictions and a comparison of simulated results with measurements during heating of the water in the TSX to about 50°C. The three‐dimensional MOTIF simulations were conducted in parallel with axisymmetric modelling using Fast Lagrangian Analysis of Continua (FLAC), which computed the heat loss from pipes that carried the heated water through the rock to and from the experiment. The numerical model was initially used to develop a plan for operation of the experiment heaters, and then subsequently used to predict temperatures and hydraulic heads in the TSX bulkhead seals and surrounding rock. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
50.
Interacting Binaries consist of a variety of stellar objects in different stages of evolution and those containing accreting compact objects still represent a major challenge to our understanding of not only close binary evolution but also of the chemical evolution of the Galaxy. These end-points of binary star evolution are ideal laboratories for the study of accretion and outflow processes, and provide insight on matter under extreme physical conditions. One of the key-questions of fundamental relevance is the nature of SN Ia progenitors. The study of accreting compact binary systems relies on observations over the entire electromagnetic spectrum and we outline here those unresolved questions for which access to the ultraviolet range is vital, as they cannot be addressed by observations in any other spectral region.An erratum to this article can be found at  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号