全文获取类型
收费全文 | 2493篇 |
免费 | 487篇 |
国内免费 | 574篇 |
专业分类
测绘学 | 158篇 |
大气科学 | 432篇 |
地球物理 | 548篇 |
地质学 | 1442篇 |
海洋学 | 224篇 |
天文学 | 223篇 |
综合类 | 264篇 |
自然地理 | 263篇 |
出版年
2024年 | 16篇 |
2023年 | 64篇 |
2022年 | 143篇 |
2021年 | 156篇 |
2020年 | 115篇 |
2019年 | 123篇 |
2018年 | 157篇 |
2017年 | 124篇 |
2016年 | 127篇 |
2015年 | 132篇 |
2014年 | 153篇 |
2013年 | 170篇 |
2012年 | 146篇 |
2011年 | 137篇 |
2010年 | 135篇 |
2009年 | 147篇 |
2008年 | 108篇 |
2007年 | 128篇 |
2006年 | 84篇 |
2005年 | 90篇 |
2004年 | 65篇 |
2003年 | 57篇 |
2002年 | 63篇 |
2001年 | 80篇 |
2000年 | 96篇 |
1999年 | 114篇 |
1998年 | 98篇 |
1997年 | 87篇 |
1996年 | 68篇 |
1995年 | 59篇 |
1994年 | 51篇 |
1993年 | 56篇 |
1992年 | 30篇 |
1991年 | 31篇 |
1990年 | 29篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1958年 | 5篇 |
排序方式: 共有3554条查询结果,搜索用时 13 毫秒
931.
柴达木盆地新构造运动与第四纪气田的形成 总被引:3,自引:0,他引:3
柴达木盆地第四纪坳陷形成于上新世晚期到全新世早期的新构造运动期,面积3.7万km2,是欧亚板块与印度板块相碰撞导致祁连山、昆仑山和阿尔金山逐渐上升,柴达木盆地东部相对下降的结果,坳陷内沉积物厚达3200m。 第四纪早期湖深水淡,晚期湖浅水咸。生气层由暗色泥质岩和碳质泥、页岩组成,厚约1500m。生气母质以腐殖型为主。天然气中CH4/C2H6+C3H8〉150,δ13C〈-60‰。天然气化学成分表明,其为成岩作用早期生物化学作用所形成。储层为细砂岩和粉砂岩,主要为湖滩相、小型河流三角洲相及筛积扇—泉水河—三角洲体系的水下部分。由于尚未充分压实,岩性疏松,孔隙度平均为32%,渗透率60.8~619μm2。盖层为湖相泥岩和含膏泥岩。天然气赋存于自生自储体系之中。主要生气凹陷及生气层殴控制天然气的分布,雁列式背斜带上的局部构造控制天然气的富集。 相似文献
932.
933.
934.
Liu Zhu Meng Jing Deng Zhu Lu Ping Guan Dabo Zhang Qiang He Kebin Gong Peng 《中国科学:地球科学(英文版)》2020,63(10):1577-1586
China-US trade holds great significance for the world's political and economic landscape. Since 2018, the US government has imposed additional tariffs on Chinese exports on the grounds of the US trade deficit with China. However, the transfer of pollutants embodied in trade and the differences in environmental costs between China and the US have not been widely recognized. In this study, we quantify the embodied carbon emissions(the "virtual" emissions associated with trade and consumption) in China-US trade by constructing a carbon dioxide emissions inventory and a multiregional input-output model.The study shows that the US benefits from a trade surplus of environmental costs by importing energy-intensive and pollutionintensive products from China, which increases China's environmental pollution and abatement costs. In 2017, 288 Mt CO_2 emissions were associated with products produced in China but finally consumed in the US, and only 46 Mt CO_2 were associated with the US products that were consumed in China. From this perspective, China-US trade results in a net transfer of 242 Mt CO_2 per year from the US to China, accounting for approximately 5% of the total CO_2 emissions in the US. More importantly, for Chinese products exported to the US, the carbon emissions embodied in one unit of economic value amount to 0.92 kg/$(RMB:USD=6.8:1), but for US products exported to China, the carbon emissions embodied in one unit of economic value amount to 0.53 kg/$, which means China will incur environmental costs that are 74% higher than those of the US while enjoying the same economic benefits. This environmental trade deficit has burdened China with higher environmental costs than economic benefits.To address this environmental trade deficit, China should actively promote further industrial upgrading and energy structure adjustment and increase investment in innovation and RD, thereby increasing the value added per unit of export products and reducing the environmental cost of producing export products. 相似文献
935.
It becomes increasingly important and challenging for nitrogen pollution prevention to identify key controls for spatial variability of nitrogen in groundwater that could be affected by multiple factors, including anthropogenic input, groundwater flow, and local geochemistry. This study characterized spatial variability of both nitrate and ammonium in the Pleistocene aquifer of central Yangtze River Basin and assessed the effect of various factors in controlling nitrate and ammonium levels based on multiple statistical approaches (correlation, geostatistics, multiple liner regression). The results indicate that nitrate is mostly influenced by Cl− that represents anthropogenic input, while Eh representing local redox state is a secondary variable influencing nitrate concentrations. The groundwater with elevated nitrate concentrations are estimated to occur mainly in areas with higher-permeability near-surface sediments which can facilitate more anthropogenic nitrate transport and less nitrate removal owing to more oxidized state. Ammonium is mostly correlated to Eh, followed by dissolved organic carbon (DOC), but only DOC improves significantly the accuracy of co-kriging prediction model. The groundwater with elevated ammonium concentrations are estimated to occur mainly in areas with more organic-rich sediments within or around the aquifer which can facilitate more ammonium release owing to natural organic matter consumption accompanying strong reducing conditions. The regional groundwater flow is not a factor significantly controlling nitrate or ammonium levels owing to flat topography and sluggish lateral flow. 相似文献
936.
Studia Geophysica et Geodaetica - Topographic effects on gravity field modeling are important for geodesy, geophysics and related geosciences. In this study we evaluate the gravitational effects of... 相似文献
937.
{{@ convertAbstractHtml(article.abstractinfoCn, "cn")}}
{{if article.graphicalAbstractinfoCn && article.graphicalAbstractinfoCn != ""}}{{@ article.graphicalAbstractinfoCn}}{{/if}} 相似文献
938.
考虑采砂影响的鄱阳湖丰水期悬浮泥沙浓度模拟 总被引:4,自引:1,他引:3
针对受采砂活动影响显著的鄱阳湖高浑浊水体,结合数值模拟和遥感技术,利用已有的鄱阳湖采砂区遥感监测结果,在构建的鄱阳湖水动力-悬浮泥沙输移模型中添加泥沙点源,对2011年7月1-31日采砂影响下的鄱阳湖丰水期悬浮泥沙浓度进行数值模拟.利用悬浮泥沙浓度实测数据和MODIS影像反演结果对模拟结果的有效验证表明,考虑采砂影响后,悬浮泥沙浓度模拟值与实测值具有强相关关系,确定性系数为0.831,均方根误差为15.5 mg/L,悬浮泥沙浓度空间分布趋势与遥感反演结果基本一致.模拟结果显示,采砂活动对鄱阳湖南部主湖区、河流入湖口影响较小,其主要影响由南向北,经棠荫以西和松门山岛以北航道、入江水道延伸到湖口区域,是鄱阳湖北湖区高浑浊水体形成的重要原因. 相似文献
939.
Feasibility of utilizing wavelet phase to map the CO2 plume at the Ketzin pilot site,Germany 下载免费PDF全文
Fei Huang Christopher Juhlin Li Han Daniel Sopher Monika Ivandic Ben Norden Wubing Deng Fengjiao Zhang Thomas Kempka Stefan Lüth 《Geophysical Prospecting》2017,65(2):523-543
Spectral decomposition is a powerful tool that can provide geological details dependent upon discrete frequencies. Complex spectral decomposition using inversion strategies differs from conventional spectral decomposition methods in that it produces not only frequency information but also wavelet phase information. This method was applied to a time‐lapse three‐dimensional seismic dataset in order to test the feasibility of using wavelet phase changes to detect and map injected carbon dioxide within the reservoir at the Ketzin carbon dioxide storage site, Germany. Simplified zero‐offset forward modelling was used to help verify the effectiveness of this technique and to better understand the wavelet phase response from the highly heterogeneous storage reservoir and carbon dioxide plume. Ambient noise and signal‐to‐noise ratios were calculated from the raw data to determine the extracted wavelet phase. Strong noise caused by rainfall and the assumed spatial distribution of sandstone channels in the reservoir could be correlated with phase anomalies. Qualitative and quantitative results indicate that the wavelet phase extracted by the complex spectral decomposition technique has great potential as a practical and feasible tool for carbon dioxide detection at the Ketzin pilot site. 相似文献
940.
Ocean Dynamics - A numerical model that solves 3D first-order Lagrangian residual velocity (uL) equations is established by modifying the HAMSOM model. With this model, uL is studied in a wide,... 相似文献