全文获取类型
| 收费全文 | 361篇 |
| 免费 | 136篇 |
| 国内免费 | 75篇 |
专业分类
| 测绘学 | 21篇 |
| 大气科学 | 142篇 |
| 地球物理 | 222篇 |
| 地质学 | 103篇 |
| 海洋学 | 46篇 |
| 天文学 | 4篇 |
| 综合类 | 10篇 |
| 自然地理 | 24篇 |
出版年
| 2023年 | 1篇 |
| 2022年 | 10篇 |
| 2021年 | 9篇 |
| 2020年 | 18篇 |
| 2019年 | 26篇 |
| 2018年 | 22篇 |
| 2017年 | 16篇 |
| 2016年 | 25篇 |
| 2015年 | 11篇 |
| 2014年 | 19篇 |
| 2013年 | 38篇 |
| 2012年 | 22篇 |
| 2011年 | 34篇 |
| 2010年 | 26篇 |
| 2009年 | 28篇 |
| 2008年 | 14篇 |
| 2007年 | 15篇 |
| 2006年 | 21篇 |
| 2005年 | 21篇 |
| 2004年 | 18篇 |
| 2003年 | 18篇 |
| 2002年 | 10篇 |
| 2001年 | 15篇 |
| 2000年 | 9篇 |
| 1999年 | 9篇 |
| 1998年 | 12篇 |
| 1997年 | 13篇 |
| 1996年 | 12篇 |
| 1995年 | 17篇 |
| 1994年 | 4篇 |
| 1993年 | 14篇 |
| 1992年 | 10篇 |
| 1991年 | 9篇 |
| 1990年 | 8篇 |
| 1989年 | 7篇 |
| 1988年 | 4篇 |
| 1987年 | 2篇 |
| 1984年 | 1篇 |
| 1983年 | 2篇 |
| 1978年 | 2篇 |
排序方式： 共有572条查询结果，搜索用时 15 毫秒
101.
102.
亚洲特提斯域岩相古地理与油气聚集地质特征 总被引：7，自引：1，他引：6
亚洲特提斯域油气在地理上主要分布于西亚段南带,其次为西亚段北带、东南亚段中带,再次为中亚段。对古、中、新特提斯域的岩相古地理特征作了分析研究,并编制了相关的岩相古地理图。认为油气分布在盆地类型上主要与前陆盆地、克拉通边缘盆地相关,盆地形态主要与台地、环形坳陷、线形坳陷等沉积—构造环境相关,其成烃物质的沉积-构造环境多位于古赤道与45°古纬度之间。提出盆地保存是盆地油气评价的先决条件。指出了亚洲特提斯域南带、中带和北带的油气勘探新领域。 相似文献
103.
104.
Abstract The acceptability of zero potential vorticity models as approximations for natural systems of small, but finite, potential vorticity is studied for bounded frontal flows of arbitrary profile. It is demonstrated that all (infinitely) long-wave solutions of the zero potential vorticity front are asymptotic limits for some (not necessarily long-wave) solutions of the small potential vorticity front. In contrast, for downstream-varying solutions there is no simple way of demonstrating this property. These findings suggest that the use of zero potential vorticity models should be carefully examined in other, non-frontal, problems as well. Finally we show that the longwave solutions of the zero potential vorticity flow are at most neutral (quasi-stable). 相似文献
105.
We conducted an analysis of heavy metals content, including As, Cd, Cr, Cu, Hg, Pb, and Zn in sediments from aquatic ecosystems in China measured in recent publications. Then, we evaluated the extent of heavy metal pollution in these ecosystems in seven different industrial districts in China (Dongbei, Huabei, Huazhong, Huanan, Huaxik, Xibei, and Huadong) with the potential ecological risk index. We found that Cd was the most concentrated pollutant, followed by Hg and As, while Cr, Cu, Pb, Zn were found in low concentrations in sediments from all types of aquatic ecosystem in China. Sediments collected from all seven industrial districts were heavily polluted, and the sequence, from most to least polluted was Dongbei>Huabei>Huazhong>Huanan>Huaxi>Xibei>Huadong. All four types of aquatic ecosystem were found to be seriously polluted and the sequence, from most to least polluted was: river>sea>lake>wetland. Specifically, Cd and Hg were the most serious pollutants in all four aquatic ecosystems, and As was also a serious pollutant in rivers. For the seven industrial districts studied the sea was the most polluted ecosystem in Dongbei, the river was the most polluted ecosystem in Huabei, Huanan, Huazhong, and the lake was the most polluted in Huadong, Huaxi, and Xibei. 相似文献
106.
The paper shows techniques for the determination of structured motion parameters from range camera image sequences. The core contribution of the work presented here is the development of an integrated least squares 3D tracking approach based on amplitude and range image sequences to calculate dense 3D motion vector fields. Geometric primitives of a human body model are fitted to time series of range camera point clouds using these vector fields as additional information. Body poses and motion information for individual body parts are derived from the model fit. On the basis of these pose and motion parameters, critical body postures are detected. The primary aim of the study is to automate ergonomic studies for risk assessments regulated by law, identifying harmful movements and awkward body postures in a workplace. 相似文献
107.
利用贵州省安顺市2015—2019年大气污染物资料和气象资料,分析安顺市空气质量特征和主要大气污染物特征,通过TrajStat软件中HYSPLIT模型的后向轨迹模式,结合GDAS气象数据、PM2.5浓度,分析不同季节输送途径及其污染轨迹,采用潜在源贡献作用和浓度权重轨迹分析方法,分析研究期内所有PM2.5污染日（PM2.5日浓度高于75 μg·m-3）输送轨迹垂直与水平方向分布特征。结果表明: PM2.5是安顺城区主要大气污染物,冬季输送污染轨迹占比较大,输送方向主要为贵州东北方向、偏南方向; 污染日PM2.5输送路径以贵州东北方向近距离输送为主,该类轨迹基本分布在880—980 hPa高度; 潜在源高值区主要集中在贵阳整个地区、毕节织金县、黔西市、金沙县等,高贡献值区主要集中在安顺紫云县、镇宁县、毕节织金县、大方县等。 相似文献
108.
Yunjun Yao Shunlin Liang Qiming Qin Kaicun Wang Shaohua Zhao 《International Journal of Applied Earth Observation and Geoinformation》2011
The latent heat of evapotranspiration (ET) plays an important role in the assessment of drought severity as one sensitive indicator of land drought status. A simple and accurate method of estimating global ET for the monitoring of global land surface droughts from remote sensing data is essential. The objective of this research is to develop a hybrid ET model by introducing empirical coefficients based on a simple linear two-source land ET model, and to then use this model to calculate the Evaporative Drought Index (EDI) based on the actual estimated ET and the potential ET in order to characterize global surface drought conditions. This is done using the Global Energy and Water Cycle Experiment (GEWEX) Surface Radiation Budget (SRB) products, AVHRR-NDVI products from the Global Inventory Modeling and Mapping Studies (GIMMS) group, and National Centers for Environmental Prediction Reanalysis-2 (NCEP-2) datasets. We randomly divided 22 flux towers into two groups and performed a series of cross-validations using ground measurements collected from the corresponding flux towers. The validation results from the second group of flux towers using the data from the first group for calibration show that the daily bias varies from −6.72 W/m2 to 12.95 W/m2 and the average monthly bias is −1.73 W/m2. Similarly, the validation results of the first group of flux towers using data from second group for calibration show that the daily bias varies from −12.91 W/m2 to 10.26 W/m2 and the average monthly bias is −3.59 W/m2. To evaluate the reliability of the hybrid ET model on a global scale, we compared the estimated ET from the GEWEX, AVHRR-GIMMS-NDVI, and NECP-2 datasets with the latent heat flux from the Global Soil Wetness Project-2 (GSWP-2) datasets. We found both of them to be in good agreement, which further supports the validity of our model's global ET estimation. Significantly, the patterns of monthly EDI anomalies have a good spatial and temporal correlation with the Palmer Drought Severity Index (PDSI) anomalies from January 1984 to December 2002, which indicates that the method can be used to accurately monitor long-term global land surface drought. 相似文献
109.
110.
