全文获取类型
收费全文 | 258篇 |
免费 | 21篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 10篇 |
地球物理 | 106篇 |
地质学 | 104篇 |
海洋学 | 13篇 |
天文学 | 43篇 |
综合类 | 2篇 |
自然地理 | 2篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 20篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 12篇 |
2013年 | 14篇 |
2012年 | 11篇 |
2011年 | 19篇 |
2010年 | 19篇 |
2009年 | 18篇 |
2008年 | 11篇 |
2007年 | 14篇 |
2006年 | 3篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 12篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有282条查询结果,搜索用时 250 毫秒
191.
A hydrogeological study of the Nossana Spring (Val Seriana, Bergamo, Italy) is presented with the aim of assessing the spring’s depletion risk. In the last few years, the discharge of the Nossana Spring showed a decreasing trend, similar to the trend of many other springs in the Prealpine Region. The study was carried out using a groundwater flow model to simulate the depletion curve of the spring in different recharge conditions. The simulations have shown that the depletion curve of the Nossana Spring depends on the recharge during the previous season. As a result, a negative exponential relation giving the spring depletion curve as a function of the recharge was obtained. This relation was also used to statistically calculate the actual probability of the occurrence of a deficiency in water resources, which for the present day is equal to 2%. Finally, the effect of climate change was considered, showing in the next 100 years a flat decline of about 40% in the average spring discharge and a considerable shortening of the critical length (the time to reach the critical discharge at which supply problems occur) in the dry season, which will be halved by the end of the century. 相似文献
192.
Adriana Zingone Laurent Dubroca Daniele Iudicone Francesca Margiotta Federico Corato Maurizio Ribera d’Alcalà Vincenzo Saggiomo Diana Sarno 《Estuaries and Coasts》2010,33(2):342-361
The climatology and interannual variability of winter phytoplankton was analyzed at the Long Term Ecological Research Station
MareChiara (LTER-MC, Gulf of Naples, Mediterranean Sea) using data collected from 1985 to 2006. Background winter chlorophyll
values (0.2–0.5 μg chl a dm−3) were associated with the dominance of flagellates, dinoflagellates, and coccolithophores. Winter biomass increases (<5.47 μg
chl a dm−3) were often recorded until 2000, generally in association with low-salinity surface waters (37.3–37.9). These blooms were
most often caused by colonial diatoms such as Chaetoceros spp., Thalassiosira spp., and Leptocylindrus danicus. In recent years, we observed more modest and sporadic winter biomass increases, mainly caused by small flagellates and small
non-colonial diatoms. The resulting negative chl a trend over the time series was associated with positive surface salinity and negative nutrient trends. Physical and meteorological
conditions apparently exert a strict control on winter blooms, hence significant changes in winter productivity can be foreseen
under different climatic scenarios. 相似文献
193.
A numerical estimation is presented on the effects induced in an existing tunnel by the development of a fault from the deep
bedrock during a seismic event. The spreading of the fault within the alluvial deposit hosting the tunnel, and the consequent
effects on its permanent liner, are studied in static conditions through a series of elastic-plastic, plane strain finite
element analyses. They account for the reduction of the shear strength and stiffness characteristics of the faulting zone
with increasing irreversible strains. Even though the calculations require only “standard”, e.g. peak and residual, material
parameters it is shown that these properties can hardly be obtained for the alluvial deposit at hand. To overcome this drawback
a relatively large scale in-situ tests could be performed and its results could be interpreted through a suitable back analysis.
This would permit characterizing the numerical model to be subsequently adopted for the analysis of the faulting process. 相似文献
194.
Vincenzo Artale Sandro Calmanti Adriana Carillo Alessandro Dell’Aquila Marine Herrmann Giovanna Pisacane Paolo M. Ruti Gianmaria Sannino Maria Vittoria Struglia Filippo Giorgi Xunqiang Bi Jeremy S. Pal Sara Rauscher 《Climate Dynamics》2010,35(5):721-740
We present an atmosphere–ocean regional climate model for the Mediterranean basin, called the PROTHEUS system, composed by the regional climate model RegCM3 as the atmospheric component and by a regional configuration of the MITgcm model as the oceanic component. The model is applied to an area encompassing the Mediterranean Sea and compared to a stand-alone version of its atmospheric component. An assessment of the model performances is done by using available observational datasets. Despite a persistent bias, the PROTHEUS system is able to capture the inter-annual variability of seasonal sea surface temperature (SST) and also the fine scale spatio-temporal evolution of observed SST anomalies, with spatial correlation as high as 0.7 during summer. The close inspection of a 10-day strong wind event during the summer of 2000 proves the capability of the PROTHEUS system to correctly describe the daily evolution of SST under strong air–sea interaction conditions. As a consequence of the model’s skill in reproducing observed SST and wind fields, we expect a reliable estimation of air–sea fluxes. The model skill in reproducing climatological land surface fields is in line with that of state of the art regional climate models. 相似文献
195.
Vincenzo Ripepi 《Astrophysics and Space Science》2003,284(1):69-72
We present time series observations of the intermediate mass Pre-Main Sequence star H254 belonging to the young star cluster IC 348 and of the Herbig Ae star V351 Ori.Both these stars present light variation on short time scale (a few hours) typical of the Scuti pulsation. The new data are briefly described together with the plan for future observational campaigns on PMS Scuti stars. 相似文献
196.
S. Falsaperla S. Alparone S. D’Amico G. Grazia F. Ferrari H. Langer T. Sgroi S. Spampinato 《Pure and Applied Geophysics》2005,162(11):2111-2132
The July 17 – August 9, 2001 flank eruption of Mt. Etna was preceded and accompanied by remarkable changes in volcanic tremor.
Based on the records of stations belonging to the permanent seismic network deployed on the volcano, we analyze amplitude
and frequency content of the seismic signal. We find considerable changes in the volcanic tremor which mark the transition
to different styles of eruptive activity, e.g., lava fountains, phreatomagmatic activity, Strombolian explosions. In particular,
the frequency content of the signal decreases from 5 Hz to 3 Hz at our reference station ETF during episodes of lava fountains,
and further decreases at about 2 Hz throughout phases of intense lava emission. The frequency content and the ratios of the
signal amplitude allow us to distinguish three seismic sources, i.e., the peripheral dike which fed the eruption, the reservoir
which fed the lava fountains, and the central conduit. Based on the analysis of the amplitude decay of the signal, we highlight
the migration of the dike from a depth of ca. 5 km to about 1 km between July 10 and 12. After the onset of the effusive phase,
the distribution of the amplitude decay at our stations can be interpreted as the overall result of sources located within
the first half kilometer from the surface. Although on a qualitative basis, our findings shed some light on the complex feeding
system of Mt. Etna, and integrate other volcanological and geophysical studies which tackle the problem of magma replenishment
for the July–August, 2001 flank eruption. We conclude that volcanic tremor is fundamental in monitoring Mt. Etna, not only
as a marker of the different sources which act within the volcano edifice, but also of the diverse styles of eruptive activity.
An erratum to this article is available at . 相似文献
197.
Andrea Dini Gianfranco Di Vincenzo Giovanni Ruggieri Jeffrey Rayner Pierfranco Lattanzi 《Mineralium Deposita》2005,40(3):337-346
The Monte Ollasteddu deposit represents a major gold discovery in the Variscan basement of southeastern Sardinia. Gold occurs
in late-Variscan extensional brittle structures hosted by meta-volcanic, and subordinately meta-sedimentary, rocks. The vein
mineralogy is dominated by quartz; arsenopyrite is the main sulphide. Reconnaissance 40Ar–39Ar dating gives ages around ∼260 Ma on K-feldspar from mineralized veins, whereas metamorphic white mica from the host rock
gives ages clustering at ∼307 Ma. The best age estimate for biotite from a nearby leucogranite body is 286.3±2.2 Ma. The Pb
isotope signature of ore and gangue minerals is entirely consistent with literature data for Variscan deposits of Sardinia,
and for European Variscan gold deposits. Fluid inclusion data point to the presence of both CO2-bearing and CO2-free fluids, with homogenization temperatures ranging from 220 to 415°C, with low-to-moderate salinities (0.4–6.2 wt% NaCl
equivalent). Monte Ollasteddu shows several features similar to European Variscan gold deposits; however, the age of mineralization
might post-date granitoid intrusion by as much as 30 Ma, being instead coeval with very late calc-alkaline basaltic dykes,
marking the transition to a post-orogenic, pre-Tethyan geodynamic setting.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
198.
The paper deals with the proposal and the experimental validation of a novel dissipative bracing system for the seismic protection of structures; compared with other similar systems, it is characterized by smaller size and weight, which makes it easier to move and to install, as well as particularly suitable to be inserted in light‐framed structures (e.g. steel structures of industrial plants). The proposed system consists of an articulated quadrilateral with steel dissipaters inserted, to be connected by tendons to frame joints; the prototypes have been designed and realized for the seismic protection of a two‐storey, large‐scale, steel frame, specially designed for shaking‐table tests. The paper, after an illustration of the system, and of its design and behaviour, presents the shaking‐table tests carried out. The experimental results have fully validated the proposed system, showing its good performance in controlling the seismic response of framed structures. A numerical non‐linear model, set up and validated on the basis of the physical tests, has been used to help interpreting the experimental results, but also to perform parametrical studies for investigating the influence of the design parameters on the performance of the control system. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
199.
Several authors have claimed for correlations between surges (dark features) and various kinds of solar emissions (radio, microwave, X-ray). In this paper we propose a model to explain such correlations, in particular presenting the properties of the instabilities resulting from the coupling between material flow, connected to the appearance of a surge, and magnetic field topology. As a consequence of such instability a turbulent energy cascade to small characteristic lengths grows up. Depending of the relevant parameters of the surge (dark feature), different regimes can be found, producing different levels of electrons acceleration and mass motion deceleration. We try then to correlate the different developments of the instability with the behavior observed in type I and type III radio bursts related to surges.Proceedings of the Second CERSA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986. 相似文献
200.
Luciano Telesca Gerardo Colangelo Vincenzo Lapenna Maria Macchiato 《International Journal of Earth Sciences》2005,94(2):285-300
Fractal tools have been used to investigate the time dynamics of hourly self-potential data, recorded during the year 2001 by five geoelectrical stations located in one of the most seismic areas of southern Italy. Scaling behaviour has been revealed by means of different statistics: the Lomb Periodogram method, the Detrended Fluctuation Analysis, the Higuchi analysis and the mean distance spanned within the time L. The values of the scaling exponents estimated by means of these methods indicate that the temporal fluctuations of the geoelectrical signals are not typical of purely random stochastic processes (i.e. white noise), but evidence the presence of long-range correlations. Furthermore, it is found that these correlations are linear. 相似文献