全文获取类型
收费全文 | 2747篇 |
免费 | 601篇 |
国内免费 | 717篇 |
专业分类
测绘学 | 214篇 |
大气科学 | 594篇 |
地球物理 | 647篇 |
地质学 | 1285篇 |
海洋学 | 455篇 |
天文学 | 92篇 |
综合类 | 352篇 |
自然地理 | 426篇 |
出版年
2024年 | 6篇 |
2023年 | 49篇 |
2022年 | 144篇 |
2021年 | 192篇 |
2020年 | 170篇 |
2019年 | 169篇 |
2018年 | 190篇 |
2017年 | 168篇 |
2016年 | 197篇 |
2015年 | 145篇 |
2014年 | 205篇 |
2013年 | 165篇 |
2012年 | 134篇 |
2011年 | 170篇 |
2010年 | 164篇 |
2009年 | 193篇 |
2008年 | 167篇 |
2007年 | 136篇 |
2006年 | 110篇 |
2005年 | 88篇 |
2004年 | 77篇 |
2003年 | 94篇 |
2002年 | 80篇 |
2001年 | 86篇 |
2000年 | 87篇 |
1999年 | 100篇 |
1998年 | 87篇 |
1997年 | 88篇 |
1996年 | 67篇 |
1995年 | 69篇 |
1994年 | 47篇 |
1993年 | 48篇 |
1992年 | 41篇 |
1991年 | 31篇 |
1990年 | 18篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1962年 | 1篇 |
1958年 | 5篇 |
1957年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有4065条查询结果,搜索用时 31 毫秒
71.
随着我国海洋强国发展战略的不断推进,海洋与陆地、内河领域的资源整治融合、信息共享共建需求日益增加.本文围绕"大交通"海事地理信息应用服务需求,以地理信息资源整合为核心,以应用服务为主线,深入开展了海陆河要素语义关联数据整合与治理技术、海陆河一体化地理信息数据资源池建设技术、无缝衔接海陆河一体可视化表达技术,海图地图服务快速更新等关键技术研究,解决了数据不一致、地图服务更新机制缺乏、数据资源分散等问题,实现了基于网络环境的全国"海陆河"地理数据资源的互联互通和开放共享,提高了我国的水陆"大交通"一体化的服务能力,促进了我国海洋海事行业发展. 相似文献
72.
73.
新乡市浅层地下水水环境特征 总被引:1,自引:0,他引:1
田良河 《地质灾害与环境保护》2011,22(3):105-109
为有效防治地下水污染,分析新乡浅表地层岩性、含水组空间分布及其水化学的类型分带和特征.在此基础上综合评价浅层地下水质量,发现新乡市浅层地下水质量污染普遍超标,建成区及周围地下水质量为Ⅴ类以上,其他地区达到Ⅳ类以上. 相似文献
74.
75.
A passive seismic experiment across the Longmenshan (LMS) fault belt had been conducted between August 2006 and July 2007 for the understanding of geodynamic process between the Eastern Tibet and Sichuan basin. We herein collected 3677 first P arrival times with high precision from seismograms of 288 teleseismic events so as to reconstruct the upper mantle velocity structure. Our results show that the depth of the Lithosphere–asthenosphere boundary (LAB) changes from 70 km beneath Eastern Tibet to about 110 km beneath Longquanshan, Sichuan Basin, which is consistent with the receiver function imaging results. The very thin mantle part of the lithosphere beneath Eastern Tibet may suggest the lithosphere delamination due to strong interaction between the Tibetan eastward escaping flow and the rigid resisting Sichuan basin, which can be further supported by the existences of two high-velocity anomalies beneath LAB in our imaging result. We also find there are two related low-velocity anomalies beneath the LMS fault belt, which may indicate magmatic upwelling from lithosphere delamination and account for the origin of tremendous energy needed by the devastating Wenchuan earthquake. 相似文献
76.
77.
Guifang Yang Xujiao Zhang Mingzhong Tian Yamin Ping Anze Chen Zhiliang Ge Zhiyun Ni Zhen Yang 《Environmental Earth Sciences》2011,64(3):671-683
The Zhangjiajie Sandstone Peak Forest Geopark (Zhangjiajie World Geopark) of northwest Hunan, China hosts a well-preserved
sequence of fluvial terraces and karst caves. In this contribution, a comparative study of fluvial terraces with karst caves
along the middle-lower Suoxi River in Zhangjiajie World Geopark is presented to improve the understanding of the development
of striking sandstone landscape in the upper Suoxi River. By integrating geomorphological, sedimentological, and geochronological
techniques, the possible correlation between fluvial terraces and karst caves, as well as their climatic and tectonic implications
is investigated. The available electron spin resonance and thermo-luminescence numerical ages coupled with morphostratigraphic
analysis indicate that aggradation of fluvial terrace levels occurred at ca. 347 ± 34 ka (T4), 104.45 ± 8.88 to 117.62 ± 9.99 ka (T3), 60.95 ± 5.18 ka (T2), and Holocene (T1), followed by the stream incision. Fluvial terrace levels (T4 to T1) correlate morphologically with the karst cave levels (L1 to L4), yet the proposed chronology for the fluvial terrace levels is a bit later than the chronological data obtained from karst
caves. In northwest Hunan, where a unique sandstone peak forest landscape was extensively developed, the fluvial terrace sequences
as well as the cave systems are the important archives for studying the evolution of the sandstone landscape. The beginning
of the sandstone landscape development must be earlier than the aggradation of the fluvial terrace T4, allowing this unique landscape to occur in the Middle Pleistocene. 相似文献
78.
79.
Dissolved fluorescent organic matter was measured using fluorescence excitation-emission matrix spectroscopy at three temporal points during a Synechococcus bloom after diatom bloom dispersion in spring, 2007. Carbohydrate and dissolved organic carbon were also analyzed. The relationship between organic matter and red tide succession was examined. The results show that after the diatom bloom, tyrosine-like fluorescence B intensity was very high within the water column and exhibited a negative correlation wi... 相似文献
80.
In this study,the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) is used to simulate Typhoon Mindulle (2004) at high resolution (3-km grid size).The data from measurements show that in the upper atmosphere the existence of an upper jet is important to the transition cyclone.When Mindulle moved to the area of the upper jet entrance,where high-altitude divergence existed, the pumping of the high-altitude divergence would enhance the vertical motion and low-level cyclone convergence. The enhanced vertical motion was confirmed by the simulation results and indicated that the existence of upper divergence enhanced the vertical motion which was favorable for the maintenance of Typhoon Mindulle.The process of extratropical transition (ET) and re-intensification always accompanies the process of cold air invasion. This process enhances the baroclinicity of the atmosphere and the formation of front at high altitudes, which converts baroclinic potential energy into kinetic energy and strengthens the cyclone vortex.The distributions of equivalent potential temperature (θe) and temperature anomalies show that the warm-core of the typhoon at the tropopause aids the re-intensification of the system. As the typhoon reenters the ocean, latent heat flux (LHF) increases in the north and west and the strong reflectivity and vertical motion occur in the east and southeast,and the west.With the re-intensification of the typhoon the wind field evolves from an oval to a circle at the lower atmosphere, the area coverage by high winds increases, and the distribution of the tangential wind shows an asymmetric pattern. 相似文献