全文获取类型
收费全文 | 1384篇 |
免费 | 249篇 |
国内免费 | 354篇 |
专业分类
测绘学 | 49篇 |
大气科学 | 216篇 |
地球物理 | 331篇 |
地质学 | 851篇 |
海洋学 | 168篇 |
天文学 | 61篇 |
综合类 | 172篇 |
自然地理 | 139篇 |
出版年
2024年 | 7篇 |
2023年 | 28篇 |
2022年 | 60篇 |
2021年 | 58篇 |
2020年 | 47篇 |
2019年 | 80篇 |
2018年 | 78篇 |
2017年 | 65篇 |
2016年 | 72篇 |
2015年 | 61篇 |
2014年 | 67篇 |
2013年 | 67篇 |
2012年 | 68篇 |
2011年 | 94篇 |
2010年 | 77篇 |
2009年 | 85篇 |
2008年 | 70篇 |
2007年 | 69篇 |
2006年 | 61篇 |
2005年 | 50篇 |
2004年 | 42篇 |
2003年 | 32篇 |
2002年 | 40篇 |
2001年 | 40篇 |
2000年 | 57篇 |
1999年 | 83篇 |
1998年 | 59篇 |
1997年 | 61篇 |
1996年 | 49篇 |
1995年 | 54篇 |
1994年 | 45篇 |
1993年 | 45篇 |
1992年 | 17篇 |
1991年 | 21篇 |
1990年 | 21篇 |
1989年 | 10篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1965年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有1987条查询结果,搜索用时 31 毫秒
911.
Seismic imaging quality is critical to describing reservoirs. There are many methods that can improve imaging quality; some rely on advanced processing means, whereas others rely on changing the field acquisition methods. However, most of the acquisition methods focus on improving imaging by using infill shots without considering the target-layer illumination energy. Moreover, total infill shooting greatly increases the acquisition cost. In this paper, we present a new method for maximizing the contribution to the target shadow area illumination by automatic local infill shooting. Thus, we designed 2D and 3D models and obtained the depth migration section by forward modeling, infill shots, depth migration, etc. The model results also show that by choosing the most appropriate number of shot points, we can enhance the shadow area energy and improve the target-layer imaging quality at low cost. 相似文献
912.
论述2008年5月12日四川汶川Ms8.0地震和2010年4月14日青海玉树Ms7.1地震前震中附近中小地震和地球自转季节性变化的关系,介绍1970年以来中国大陆其他14例M≥7.0地震震例.研究发现,在强震前几年时间内,震中附近地区的中小地震有偏向发生于地球自转速率季节性变化加速或者减速某一阶段的现象.该结果对深入认识地震与地球自转之间的关系具有一定启示意义,对地震预测具有一定指导意义. 相似文献
913.
基于移动平台地震速报短信客户端(EQSMS)的设计与实现 总被引:1,自引:0,他引:1
侯建民 《地震地磁观测与研究》2013,34(3)
通过地震速报短信客户端软件(EQSMS),当用户收到速报短信后即可实时查看速报震中的矢量地理信息、卫星影像信息和震中距等数据,便于应急人员对灾害评估和应急救援等及早做出反应和工作部署. 相似文献
914.
915.
916.
917.
Kai Hou Hui Qian Qiying Zhang Tao Lin Yao Chen Yuting Zhang Wengang Qu 《地球表面变化过程与地形》2020,45(4):862-876
Permeability differences in multi-cycle loess–paleosol aeolian sediments, which are still poorly understood, have the potential to significantly improve our understanding of climatic change during the glacial–interglacial periods of the Quaternary. In this study, the permeability of a well-preserved and continuous loess–paleosol sequence in the South Jingyang Plateau was investigated. Weathering intensity was inferred using a series of climate proxies including grain-size distribution, magnetic susceptibility and mineralogy. The results of laboratory tests showed that the average saturated hydraulic conductivity of loess layers is higher than that of paleosol layers. Also, clear differences between loess and paleosol were found in terms of depth variations of the vertical and horizontal saturated hydraulic conductivities. Differences in loess–paleosol were also found for other proxies for pedogenic weathering [i.e. clay content, sand content, Kd value (ratio of coarse silt to clay), magnetic susceptibility, dolomite content and the ratios of hornblende/illite and hornblende/chlorite]. Our results showed a high permeability of loess layers associated with weak pedogenic weathering during cold/dry paleoclimatic conditions in glacial stages. On the contrary, paleosol layers developed in a warm/humid climate during the interglacial stages experienced strong pedogenic weathering that resulted in lower permeability. Based on these results, we construct a connection between Quaternary climate change theory and the modern hydrological system. This provides a scientific basis for investigating the distribution and pollution of groundwater resources in the local region. © 2020 John Wiley & Sons, Ltd. 相似文献
918.
Using interpolation and averaging methods, we analyzed the sea surface wind data obtained from December 1992 to November 2008 by the scatterometers ERS-1, ERS-2, and QuikSCAT in the area of 2°N–39 °N, 105°E–130°E, and we reported the monthly mean distributions of the sea surface wind field. A vector empirical orthogonal function (VEOF) method was employed to study the data and three temporal and spatial patterns were obtained. The first interannual VEOF accounts for 26% of the interannual variance and displays the interannual variability of the East Asian monsoon. The second interannual VEOF accounts for 21% of the variance and reflects the response of China sea winds to El Niño events. The temporal mode of VEOF-2 is in good agreement with the curve of the Niño 3.4 index with a four-month lag. The spatial mode of VEOF-2 indicates that four months after an El Niño event, the southwesterly anomalous winds over the northern South China Sea, the East China Sea, the Yellow Sea, and the Bohai Sea can weaken the prevailing winds in winter, and can strengthen the prevailing winds in summer. The third interannual VEOF accounts for 10% of the variance and also reflects the influence of the ENSO events to China Sea winds. The temporal mode of VEOF-3 is similar to the curve of the Southern Oscillation Index. The spatial mode of VEOF-3 shows that the northeasterly anomalous winds over the South China Sea and the southern part of the East China Sea can weaken the prevailing winds, and southwesterly anomalous winds over the northern part of the East China Sea, the Yellow Sea, and the Bohai Sea can strengthen the prevailing winds when El Niño occurs in winter. If El Niño happens in summer, the reverse is true. 相似文献
919.
GPS����վˮƽλ�Ʒ�������Է��� 总被引:1,自引:0,他引:1
GPSλ?????в???????????????????б??????????????????仯?????????????????????????????????????, ???????????????????????????????????????????м?????п??幹??????????????з????????????????????????????????????????????GPS????е????仯???????????????????????????????Ч????????????????е??????????????????????? 相似文献
920.