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   225篇
  免费   21篇
  国内免费   3篇
测绘学   1篇
大气科学   8篇
地球物理   86篇
地质学   100篇
海洋学   14篇
天文学   36篇
综合类   2篇
自然地理   2篇
  2024年   1篇
  2022年   2篇
  2021年   3篇
  2020年   10篇
  2019年   9篇
  2018年   8篇
  2017年   19篇
  2016年   12篇
  2015年   13篇
  2014年   11篇
  2013年   13篇
  2012年   11篇
  2011年   19篇
  2010年   16篇
  2009年   17篇
  2008年   11篇
  2007年   12篇
  2006年   2篇
  2005年   8篇
  2004年   7篇
  2003年   5篇
  2002年   10篇
  2001年   2篇
  2000年   2篇
  1999年   2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
  1973年   1篇
  1958年   1篇
排序方式: 共有249条查询结果,搜索用时 15 毫秒
141.
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   
142.
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   
143.
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   
144.
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   
145.
Results of a research carried out on the lavas from Campi Flegrei and Somma-Vesuvius volcanic districts are reported here. The lavas have been widely employed, since Roman age, in several important monumental buildings of the Campania region, mainly in the town of Naples and in its province. They are classified as trachytes (Campi Flegrei products), tephri-phonolites and phono-tephrites (Somma-Vesuvius complex) from a petrographical point of view. Sampling was carried out from well-known exploitation districts. A substantial chemical difference between the products of the two sectors was confirmed, while petrophysical characterization evidenced similarity among the two different materials, although some differences were recorded even in samples coming from the same exploitation site.  相似文献   
146.
Archaeological and instrumental data indicate that the southern sector of the volcanic island of Lipari has been subsiding for the last 2100 years due to isostatic and tectonic factors, at variable rates of up to ~11 mm a?1. Based on this data, a detailed marine flooding scenario for 2100 AD is provided for the bay of Marina Lunga in the eastern part of the island from (1) an ultra‐high‐resolution Digital Terrain and Marine Model (DTMM) generated from multibeam bathymetry (MB) and Unmanned Aerial Vehicles (UAV), (2) the rate of land subsidence from Global Positioning System (GPS) data and (3) the regional sea‐level projections of the International Panel on Climate Change (IPCC). When land subsidence is considered, the upper bound of sea‐level rise is estimated at 1.36 m and 1.60 m for RCP4.5 and RCP8.5 climate change scenarios, respectively. Here, we show the expected impact of marine flooding at Lipari for the next 85 years and discuss the hazard implications for the population living along the shore.  相似文献   
147.
148.
Recent transportation infrastructure works in Naples, Italy, provided important discoveries related to the production of pottery in the Hellenistic workshop area of Piazza Nicola Amore. A minero‐petrographic investigation was conducted on 35 samples belonging to the widespread Campana A ware and production indicators (clayey raw materials, unfired Graeco‐Italic amphorae, kiln wastes, workshop tools). Additional analysis was conducted on black‐glaze and common ware samples for comparison. The analyses reveal compositional and technological homogeneity of Campana A ware. Samples are characterized by low CaO content with evidence of both volcanic and sedimentary components, suggesting that different clay sources were properly mixed to prepare a standard recipe. Production indicators, black‐glaze and common wares, have a composition well consistent with the calcareous clays from the island of Ischia. Leucite‐ and garnet‐bearing temper from the Somma Volcano were used for the preparation of coarse‐grained pastes, unfired Graeco‐Italic amphorae, and clayey raw materials, thus suggesting that they represented the clay sources for amphorae production. Our results reveal new technological and socioeconomic aspects of Hellenistic pottery production in the Bay of Naples, in particular for the Campana A ware, now representing a new reference group: Neapolis.  相似文献   
149.
Structural engineering problems are always affected by many sources of uncertainty, such as aleatory of material properties, applied loads and earthquake intensity, therefore, seismic assessment of structures should be based on probabilistic methods. Since PBSD (Performance‐based Seismic Design) philosophy was formulated, many researches have been conducted in this field in order to develop simple and accurate procedures for evaluating structural reliability. An important contribution has been provided by Jalayer and Cornell, who have developed a closed‐form expression to evaluate the mean annual frequency of exceeding a defined limit state. In this paper, by assuming the record‐to‐record variability as the only source of uncertainty, the seismic reliability of concentrically braced frames designed according to traditional and innovative methodologies is investigated, and a comparison between their performances is presented. In particular, two design methodologies have been applied: Eurocode 8 provisions and a new design methodology based on a rigorous application of ‘capacity design’ criteria. The innovative reduced section solution strategy, based on the reduction of cross sections at bracing member ends, has also been analysed. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
150.
The Philippines is highly susceptible to both geophysical and climate-related disasters. This article explores Filipinos knowledge and perception of climate change and their association with what action Filipinos take to prepare for rapid onset natural hazards such as typhoons. Data for this study were collected from a nationally representative random survey of 5,184 adults conducted between March and April of 2017. Filipinos self-report relatively low levels of knowledge of climate change and cited increased temperatures, shifts in seasons, and heavier rains as the most likely consequences. Levels of disaster preparedness in the Philippines differ widely by region. Although most Filipinos perceive that natural hazards are a risk to them, only a third of Filipinos undertake measures to prepare for disasters. Filipinos who perceive climate-related changes directly impacting their households report taking greater action to prepare for disasters. Filipinos who believe they have been directly impacted by climate-related changes are also more likely to prepare for disasters, take planning actions, and undertake material actions to prepare, such as dwelling improvements. Other factors associated with disaster preparedness include gender, membership in an association, wealth, risk perception, and prior exposure to and losses due to disasters. The findings imply that, while posing different challenges and requiring different responses, adaptation to climate change and disaster preparedness are inherently associated and potentially mutually reinforcing. Policies and programs would arguably benefit from a more unified intervention framework that links climate change adaptation and disaster preparedness.  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