全文获取类型
收费全文 | 4366篇 |
免费 | 177篇 |
国内免费 | 21篇 |
专业分类
测绘学 | 129篇 |
大气科学 | 308篇 |
地球物理 | 1741篇 |
地质学 | 1432篇 |
海洋学 | 220篇 |
天文学 | 528篇 |
综合类 | 24篇 |
自然地理 | 182篇 |
出版年
2022年 | 33篇 |
2021年 | 92篇 |
2020年 | 89篇 |
2019年 | 59篇 |
2018年 | 196篇 |
2017年 | 186篇 |
2016年 | 284篇 |
2015年 | 209篇 |
2014年 | 247篇 |
2013年 | 302篇 |
2012年 | 245篇 |
2011年 | 236篇 |
2010年 | 194篇 |
2009年 | 192篇 |
2008年 | 168篇 |
2007年 | 134篇 |
2006年 | 130篇 |
2005年 | 88篇 |
2004年 | 105篇 |
2003年 | 79篇 |
2002年 | 70篇 |
2001年 | 77篇 |
2000年 | 47篇 |
1999年 | 42篇 |
1998年 | 69篇 |
1997年 | 53篇 |
1996年 | 34篇 |
1995年 | 29篇 |
1994年 | 41篇 |
1993年 | 32篇 |
1992年 | 40篇 |
1991年 | 33篇 |
1990年 | 48篇 |
1989年 | 35篇 |
1988年 | 24篇 |
1987年 | 29篇 |
1986年 | 30篇 |
1984年 | 28篇 |
1983年 | 23篇 |
1982年 | 27篇 |
1981年 | 25篇 |
1980年 | 24篇 |
1979年 | 26篇 |
1978年 | 24篇 |
1977年 | 25篇 |
1976年 | 26篇 |
1975年 | 23篇 |
1974年 | 24篇 |
1973年 | 29篇 |
1971年 | 36篇 |
排序方式: 共有4564条查询结果,搜索用时 15 毫秒
241.
Bouri Djamel Eddine Brahimi Abdelkader Krim Abdallah Arab Ahmed Najser Jan Mašín David 《Geotechnical and Geological Engineering》2022,40(4):1675-1692
Geotechnical and Geological Engineering - This paper presents a study on Chlef sand to examine the effect of fines content (Fc), relative density (RD) and initial conditions on the compressibility... 相似文献
242.
Rainfall thresholds for the triggering of landslides considering previous soil moisture conditions (Asturias,NW Spain) 总被引:1,自引:0,他引:1
Pablo Valenzuela María José Domínguez-Cuesta Manuel Antonio Mora García Montserrat Jiménez-Sánchez 《Landslides》2018,15(2):273-282
Given its geological and climatic conditions and its rugged orography, Asturias is one of the most landslide prone areas in the North of Spain. Most of the landslides occur during intense rainfall episodes. Thus, precipitation is considered the main triggering factor in the study area, reaching average annual values of 960 mm. Two main precipitation patterns are frequent: (i) long-lasting periods of moderate rainfall during autumn and winter and (ii) heavy short rainfall episodes during spring and early summer. In the present work, soil moisture conditions in the locations of 84 landslides are analysed during two rainfall episodes, which represent the most common precipitation patterns: October–November 2008 and June 2010. Empirical data allowed the definition of available water capacity percentages of 99–100% as critical soil moisture conditions for the landslide triggering. Intensity-duration rainfall thresholds were calculated for each episode, considering the periods with sustained high soil moisture levels before the occurrence of each analysed landslide event. For this purpose, data from daily water balance models and weather stations were used. An inverse relationship between the duration of the precipitation and its intensity, consistent with published intensity-duration thresholds, was observed, showing relevant seasonal differences. 相似文献
243.
The CO2-rich thermal groundwater in the Betic Cordilleras in Spain has been studied with regard to the geological and hydrogeological
setting, physical and chemical characteristics, and 13C-isotope content. The study area is about 60 km northeast of Almería city, in southeastern Spain. The thermomineral waters
are plentiful and are related to regional geothermal anomalies. Temperatures of 20 −41°C, high bicarbonate concentrations
(183–1824 mg/L), and high amounts of PCO2 (<1.1 bar) characterize the groundwater. CO2 spatial variations are related to proximity to the Carboneras, Palomares, and Guadalentín fault systems, which may be the
surface representation of the zone of crustal thinning and magmatism. δ
13C values probably indicate a deep source for the CO2, either the mantle or perhaps carbonate rocks in the metamorphic substratum. The high amount of CO2 in the groundwater causes problems in wells and severely restricts water usage. The hydrothermal features of this area are
probably related to neotectonic activity.
Received, September 1998/Revised, June 1999, September 1999/Accepted, December 1999 相似文献
244.
M. S. Barbano J. J. Egozcue M. García Fernández A. Kijko J. Lapajne D. Mayer-Rosa V. Schenk Z. Schenková D. Slejko G. Zonno 《Natural Hazards》1989,2(3-4):217-228
The working group on Test Regions for Evaluation of Methods for Seismic Hazard Assessment in Europe (TERESA), consisted of 15 members from 10 different European countries. Methods and experience gathered in these countries have been compared and discussed for two test areas in Europe: the Sannio-Matese region, Southern Italy, with high seismic activity, and the border region between Belgium, The Netherlands, and Federal Republic of Germany, with low activity.This paper summarizes the results for one of the test areas, Sannio-Matese. Most of the participants used statistical procedures to assess earthquake hazard, receiving results in terms of probability of occurrence for intensity as the ground-motion parameter. It was found that careful preparation of input data and parameters is the major influencing factor, therefore most of the efforts of the working group was devoted to this task.The scatter of the obtained results of the group is considerable, mainly because of the uncertainties in the data and the subjectiveness involved in the procedures. For better control of both factors, more objective methods have to be developed. 相似文献
245.
Theo de Crook Vladimír Schenk M. S. Barbano F. Colombo J. J. Egozcue M. García-Fernández P. Kottnauer G. Leydecker F. Mantlík Z. Schenková G. Zonno 《Natural Hazards》1989,2(3-4):229-236
The algorithms to evaluate seismic hazard, used and/or developed by five teams participating in the TERESA project, applied to the low seismicity area Belgium, The Netherlands and NW Germany are compared. The main differences in the results can be explained by the majority criterion of Egozcue et al. (1989), the differences in the upper bound and zonification and, in some cases, by a higher attenuation. 相似文献
246.
Catalina Gómez-Espinosa F. Raúl Gío-Argáez Ester A. Farinati Salvador Aliotta Sergio Adrian Salgado-Souto 《Arabian Journal of Geosciences》2018,11(8):188
This study presents both qualitative and quantitative data regarding marine mollusk (gastropods and bivalves) shell bioerosion and encrustation based on death assemblages obtained from a recent supratidal environment in Playa Norte, Veracruz State. The objectives of this study were to assess the nature of bioerosion and encrustation processes and to investigate the role of these taphonomic features contributing to the deterioration of natural shell accumulations within a tropical siliciclastic tidal environment. The assemblage comprises 31 species: 13 gastropods and 18 bivalves. The bioerosion and encrustation degrees were low to moderate for both types. The most abundant traces were predatory gastropod structures (Oichnus paraboloides and O. simplex), whereas sponge borings (Entobia isp.), polychaete dwellings (Caulostrepsis taeniola), and echinoid raspings (Gnatichnus isp.) were less frequent. The encrusting organisms include polychaete serpulids, bryozoans, and rare foraminifers (Homotrema rubrum). Because of the low bioerosion and encrustation degrees occurring in this area, accumulation is expected to predominate over biotic destruction. As deposition conditions (richly fossiliferous carbonate sandstone beds) were similar to those prevailing in the Tuxpan Formation during the Miocene (Langhian), it is suggested that this study provides an equivalent reference to interpret mollusk fossil assemblages located in this site. 相似文献
247.
248.
The region known as Pampa Plain, in Argentina, is a vast area characterized by slopes of less than 0.05%. The surface sediment is silty sand, mainly Aeolian, referred to as Pampean Loess, which is a phreatic aquifer unit of utmost importance for the water supply of the region. On account of the slight gradient, hydrogeological analyses using only hydraulic measurements are difficult to perform, often leading to confusing results. Thus, the study presented relies on hydrochemical modeling and isotopic determinations as well. The study area comprises three catchments in the inter-mountainous area corresponding to El Moro, Tamangueyú and Seco creeks, and covering 2,570 km2 in the province of Buenos Aires. Measurements of piezometric levels and samples of groundwater, surface water and rainwater were carried out between January and March 2005. Major ion results were analyzed by means of hydrochemical graphs and hydrogeochemical modelling using NETPATH. The resulting data show that it is possible to identify local changes in recharge, flow direction and stream/groundwater relationship by using hydrochemical and isotopic information, which may become a useful and more precise tool for the study of particularly flat landscapes. 相似文献
249.
250.
Slope movements together with intensive river erosion and the following accumulation are the leading processes in the landscape evolution in the area of Machu Picchu village (former Aguas Calientes), which is located close to the Machu Picchu Sanctuary. Debris flows affect not only the bottoms of valleys or canyons, but also debris fans at the termini of the drainage basins, which are heavily inhabited at some places. The most recent event in the Machu Picchu village occurred in April 2004, but several others were documented in a broader area in the last 50 years. The field inspections at Machu Picchu (May and September 2004; June and September 2005) together with oral testimony revealed the nature and behavior of the debris flow. Machu Picchu village can be assessed as a zone with high landslide risk in relation to its urban development. Despite that, the village recorded a rapid growth (threefold population increase) without urban control within the past two decades. Precipitation, which is the main triggering factor of the debris flows, and natural hazard management of the Machu Picchu village are discussed in this paper. 相似文献