全文获取类型
收费全文 | 83596篇 |
免费 | 1218篇 |
国内免费 | 761篇 |
专业分类
测绘学 | 2102篇 |
大气科学 | 5779篇 |
地球物理 | 16026篇 |
地质学 | 29872篇 |
海洋学 | 7625篇 |
天文学 | 19372篇 |
综合类 | 260篇 |
自然地理 | 4539篇 |
出版年
2022年 | 527篇 |
2021年 | 906篇 |
2020年 | 999篇 |
2019年 | 1101篇 |
2018年 | 2235篇 |
2017年 | 2187篇 |
2016年 | 2599篇 |
2015年 | 1411篇 |
2014年 | 2495篇 |
2013年 | 4263篇 |
2012年 | 2701篇 |
2011年 | 3518篇 |
2010年 | 3130篇 |
2009年 | 3960篇 |
2008年 | 3504篇 |
2007年 | 3579篇 |
2006年 | 3318篇 |
2005年 | 2424篇 |
2004年 | 2463篇 |
2003年 | 2409篇 |
2002年 | 2245篇 |
2001年 | 1958篇 |
2000年 | 1809篇 |
1999年 | 1562篇 |
1998年 | 1605篇 |
1997年 | 1521篇 |
1996年 | 1300篇 |
1995年 | 1256篇 |
1994年 | 1105篇 |
1993年 | 994篇 |
1992年 | 937篇 |
1991年 | 945篇 |
1990年 | 990篇 |
1989年 | 830篇 |
1988年 | 814篇 |
1987年 | 868篇 |
1986年 | 840篇 |
1985年 | 1059篇 |
1984年 | 1144篇 |
1983年 | 1072篇 |
1982年 | 994篇 |
1981年 | 900篇 |
1980年 | 854篇 |
1979年 | 835篇 |
1978年 | 802篇 |
1977年 | 709篇 |
1976年 | 656篇 |
1975年 | 669篇 |
1974年 | 621篇 |
1973年 | 666篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
K. Satish Kumar K. N. S. S. S. Srinivas V. Pradeep Kumar P. Prabhakara Prasad T. Seshunarayana 《Journal of the Geological Society of India》2018,91(2):174-180
High ground magnetic anomalies are observed at western basin of the Sandur schist belt (SSB) near Muraripura village, Karnataka. Sources for these anomalies are inferred due to presence of exposed banded iron formations hosted by metabasalts, arenaous and argillaceous rocks associated with the Donimali Formation of the schist belt. Two varieties of BIF bands are observed in the study area viz. Band 1 and Band 2. The bands 1 and 2 are displaced by lateral strike-slip fault. Band 1 is dominantly composed of banded iron formation, rich in iron ore minerals and silica chert. Band 2 is largely composed of ferruginous quartzite and quartz arenites. Qualitative analysis of the magnetic data indicates that the study area can be divided into three lithologically important BIF/BQ formations. Spectral and quantitative analysis of the magnetic data indicates, the average depth of band 1 is 70 m and band 2 is 130 m. The magnetic data results are well correlated with chemical analysis of borehole and surface rock samples data. 相似文献
992.
Damage and destruction to schools from climate-related disasters can have significant and lasting impacts on curriculum and educational programs, educational attainment, and future income-earning potential of affected students. As such, assessing the potential impact of hazards is crucial to the ability of individuals, households, and communities to respond to natural disasters, extreme events, and economic crises. Yet, few studies have focused on assessing the vulnerability of schools in coastal regions of the USA. Using Hurricane Ike’s tropical storm wind swath in the State of Texas as our study area, we: (1) assessed the spatial distribution patterns of school closures and (2) tested the relationship between school closure and vulnerability factors (namely physical exposure and school demographics) using zero-inflated negative binomial regression models. The regression results show that higher probabilities of hurricane strikes, more urbanized school districts, and school districts located in coastal counties on the right side of Ike’s path have significant positive associations with an increase in the number of school closure days. Socioeconomic characteristics were not significantly associated with the number of days closed, with the exception of proportion of Hispanic youth in schools, a result which is not supported by the social vulnerability literature. At a practical level, understanding how hurricanes may adversely impact schools is important for developing appropriate preparedness, mitigation, recovery, and adaptation strategies. For example, school districts on the right side of the hurricane track can plan in advance for potential damage and destruction. The ability of a community to respond to future natural disasters, extreme events, and economic crises depends in part on mitigating these adverse effects. 相似文献
993.
Windblown dust originating in China and Mongolia causes health effects and agricultural damage in its source areas and causes Asian dust events in Japan. An early warning system that could be combined with weather forecasts would be helpful in preventing serious damage. However, it is difficult to specify source areas of dust with current dust modeling systems because land surface information, including vegetation coverage and land surface soil water content, is inadequate. To find and monitor dust source regions, a semi-real-time dust erodibility map was developed based on MODIS satellite data that focuses particularly on the threshold wind speed in a target area of northeast Asia including China and Mongolia (35°–50°N, 75°–120°E). The mapping system incorporates satellite data on snow cover, areas of frozen soil, surface soil water content, and vegetation cover. 相似文献
994.
The complex geological environment due to active tectonics and varied lithology with multiple phases of deformation and metamorphism led to a rugged topography and large destabilization of slopes in the Himalayan region. However, the ever-rising activities due to various ongoing developmental and urbanization processes in the region are contributing to instability of slopes. The significant number of causalities and massive economic loss is deliberately endangering Himalayan ecosystem due to landslide-related phenomena. Transportation corridors within Himalayan terrain experience frequent landslides, particularly the sections manifested by debris slopes. From several decades, the national highway-58, in Uttarakhand, Himalayas, has been endangered due to diverse and incessant slope failures. The present investigation demonstrates the stability appraisal along the strategic transportation corridor. These studies incorporate the various issues and causes pertaining to debris slides from Rishikesh to Devprayag, Uttarakhand. The numerical simulation assessment was undertaken by deterministic and sensitivity analyses by conventional limit equilibrium methods which is being augmented by much advanced and robust finite element tool. Factor of safety for each slope was determined, and correspondingly, best efficient slope stabilization remedies were proposed to enhance the stability of slopes. It is recommended that such strategic slope stability assessment should be performed within different vulnerable sections of the Himalayas and likewise regions for fruitful and sustainable step toward disaster mitigation. 相似文献
995.
The automatic extraction of information content from remotely sensed data is always challenging. We suggest a novel fusion approach to improve the extraction of this information from mono-satellite images. A Worldview-2 (WV-2) pan-sharpened image and a 1/5000-scaled topographic vector map (TOPO5000) were used as the sample data. Firstly, the buildings and roads were manually extracted from WV-2 to point out the maximum extractable information content. Subsequently, object-based automatic extractions were performed. After achieving two-dimensional results, a normalized digital surface model (nDSM) was generated from the underlying digital aerial photos of TOPO5000, and the automatic extraction was repeated by fusion with the nDSM to include individual object heights as an additional band for classification. The contribution was tested by precision, completeness and overall quality. Novel fusion technique increased the success of automatic extraction by 7% for the number of buildings and by 23% for the length of roads. 相似文献
996.
GeoJournal - The purpose of this research is to examine the correlation between the bioenergy industry and economic outgrowth. This study investigates the growth hypothesis within the setting of... 相似文献
997.
Fokin P. A. Zakrevskaya E. Yu. Sahakyan L. G. Grigoryan T. E. 《Lithology and Mineral Resources》2021,56(5):438-459
Lithology and Mineral Resources - Nummulite facies are known to be a good indicator of Eocene shallow-water paleoenvironments. Nummulitic limestones are widespread in the Lower Eocene of... 相似文献
998.
Lithology and Mineral Resources - Upper Paleozoic sections in Taimyr comprise genetic rock complexes of different zones: deep-water shelf; offshore transition zone; shoals, deltas, and beaches of... 相似文献
999.
1000.
Trifonov V. G. Sokolov S. Yu. Bachmanov D. M. Sokolov S. A. Trikhunkov Ya. I. 《Geotectonics》2021,55(3):334-360
Geotectonics - Studies carried out by the authors show that the uplift of Central Asia situated between the eastern Alpine–Himalayan and western Altai–Stanovoy orogenic belts formed in... 相似文献