全文获取类型
收费全文 | 7540篇 |
免费 | 1436篇 |
国内免费 | 2279篇 |
专业分类
测绘学 | 943篇 |
大气科学 | 2092篇 |
地球物理 | 1764篇 |
地质学 | 2830篇 |
海洋学 | 1653篇 |
天文学 | 356篇 |
综合类 | 497篇 |
自然地理 | 1120篇 |
出版年
2024年 | 58篇 |
2023年 | 147篇 |
2022年 | 282篇 |
2021年 | 385篇 |
2020年 | 379篇 |
2019年 | 443篇 |
2018年 | 386篇 |
2017年 | 406篇 |
2016年 | 391篇 |
2015年 | 412篇 |
2014年 | 505篇 |
2013年 | 602篇 |
2012年 | 492篇 |
2011年 | 478篇 |
2010年 | 437篇 |
2009年 | 551篇 |
2008年 | 525篇 |
2007年 | 563篇 |
2006年 | 509篇 |
2005年 | 432篇 |
2004年 | 408篇 |
2003年 | 317篇 |
2002年 | 319篇 |
2001年 | 254篇 |
2000年 | 232篇 |
1999年 | 206篇 |
1998年 | 175篇 |
1997年 | 168篇 |
1996年 | 163篇 |
1995年 | 109篇 |
1994年 | 96篇 |
1993年 | 98篇 |
1992年 | 82篇 |
1991年 | 56篇 |
1990年 | 52篇 |
1989年 | 30篇 |
1988年 | 26篇 |
1987年 | 21篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Co-seismic ground deformation and source parameters of Mani M7.9 earthquake inferred from spaceborne D-InSAR observation data 总被引:4,自引:0,他引:4
SHAN Xinjian MA Jin WANG Changlin LIU Jiahang SONG Xiaoyu & ZHANG Guifang .Institute of Geology Laboratory of Tectonophysics China Seismological Bureau Beijing China .Institute of Remote Sensing Application Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2004,47(6):481-488
In recent ten years, Differential Interferometric Synthetic Aperture Radar (D-InSAR) has become a major technique of space-based geodesy together with GPS, VLBI and SLR. Interferometric Synthetic Aper-ture Radar (InSAR) has many advantages, such as all-weather, all-time, strong stability and dynamic survey property, and no requirements for ground sta-tions. In particular, the surveying results by InSAR can cover a large range of the ground deformation field in succession and has gr… 相似文献
992.
太行山前平原非河道条件下地下调蓄功能实验研究--以滹沱河冲洪积平原为例 总被引:5,自引:0,他引:5
摘要:通过实验研究探讨了太行山前平原地下调蓄能力,实验研究表明,在汇水坑渗、井灌和引水渠渗条件下,太行山前冲洪积平原地下调蓄功能不仅与地表积水深度、入渗时间有关,而且还与汇水总量的多少有关。单位时间渗漏量的大小与地表蓄水深度呈正相关关系。地表蓄水深度愈大,单位时间渗漏量愈大;累计渗漏量随着入渗时间的延长而增加,渗漏速率随着累计渗漏量的增加而减小。采用井灌方式进行地下调蓄的关键,是选择具有强渗透性的层位。 相似文献
993.
南海北部一百万年以来的表层古生产力变化:来自ODP1144站的蛋白石记录 总被引:7,自引:1,他引:6
通过南海北部ODP 1144站蛋白石含量测定及其堆积速率的计算,并结合氧同位素记录等相关资料,获得南海北部1050ka以来高分辨率的表层古生产力变化与冰期旋回和东亚季风的关系。约900ka以来,蛋白石含量及其堆积速率较900ka以前明显增加,反映了“中更新世革命”事件之后,全球气候变冷,并导致表层生产力的提高。由于第四纪冰期旋回中的冬、夏季风的加强,加上1144站特殊的地理位置,使该站在冰期时表层生产力增加,间冰期时表层生产力降低。浮游有孔虫氧同位素记录与蛋白石含量及其堆积速率的时间序列频谱分析结果显示,三者均出现了相对应的偏心率周期、斜率周期和岁差周期,说明该站表层生产力的变化主要受地球轨道周期的驱动。 相似文献
994.
995.
Brian P. Reen David R. Stauffer Kenneth J. Davis Ankur R. Desai 《Boundary-Layer Meteorology》2006,120(2):275-314
The importance of soil moisture inputs and improved model physics in the prediction of the daytime boundary-layer structure during the Southern Great Plains Hydrology Experiment 1997 (SGP97) is investigated using the non-hydrostatic fifth-generation Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model MM5. This is Part II of a two-part study examining the relationship of surface heterogeneity to observed boundary-layer structure. Part I focuses on observations and utilizes a simple model while Part II uses observations and MM5 modelling. Soil moisture inputs tested include a lookup table based on soil type and season, output from an offline land-surface model (LSM) forced by atmospheric observations, and high-resolution ( 800 m) airborne microwave remotely sensed data. Model physics improvements are investigated by comparing an LSM directly coupled with the MM5 to a simpler force-restore method at the surface. The scale of land surface heterogeneities is compared to the scale of their effects on boundary-layer structure.The use of more detailed soil moisture fields allowed the MM5 to better represent the large-scale (hundreds of km) and small-scale (tens of km) horizontal gradients in surface-layer weather and, to a lesser degree, the atmospheric boundary-layer (ABL) height, which was evaluated against observations measured by differential absorption lidar (DIAL). The benefits of coupling an LSM to the MM5 were not readily evident in this summertime case, with the model having particular difficulty simulating the timing of maximum surface fluxes while underestimating the depth of the mixed layer. 相似文献
996.
We examine hypotheses for the formation of light-toned layered deposits in Juventae Chasma using a combination of data from Mars Global Surveyor's Mars Orbiter Camera (MOC), Mars Orbiter Laser Altimeter (MOLA), and Thermal Emission Spectrometer (TES), as well as Mars Odyssey's Thermal Emission Imaging System (THEMIS). We divide Juventae Chasma into geomorphic units of (i) chasm wall rock, (ii) heavily cratered hummocky terrain, (iii) a mobile and largely crater-free sand sheet on the chasm floor, (iv) light-toned layered outcrop (LLO) material, and (v) chaotic terrain. Using surface temperatures derived from THEMIS infrared data and slopes from MOLA, we derive maps of thermal inertia, which are consistent with the geomorphic units that we identify. LLO thermal inertias range from ∼400 to 850 J m−2 K−1 s−1/2. Light-toned layered outcrops are distributed over a remarkably wide elevation range () from the chasm floor to the adjacent plateau surface. Geomorphic features, the absence of small craters, and high thermal inertia show that the LLOs are composed of sedimentary rock that is eroding relatively rapidly in the present epoch. We also present evidence for exhumation of LLO material from the west wall of the chasm, within chaotic and hummocky terrains, and within a small depression in the adjacent plateau. The data imply that at least some of the LLO material was deposited long before the adjacent Hesperian plateau basalts, and that Juventae Chasma underwent, and may still be undergoing, enlargement along its west wall due to wall rock collapse, chaotic terrain evolution, and exposure and removal of LLO material. The new data allow us to reassess possible origins of the LLOs. Gypsum, one of the minerals reported elsewhere as found in Juventae Chasma LLO material, forms only at low temperatures () and thus excludes a volcanic origin. Instead, the data are consistent with either multiple occurrences of lacustrine or airfall deposition over an extended period of time prior to emplacement of Hesperian lava flows on the plateau above the chasm. 相似文献
997.
998.
999.
1000.