全文获取类型
收费全文 | 2004篇 |
免费 | 688篇 |
国内免费 | 908篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 1791篇 |
地球物理 | 227篇 |
地质学 | 627篇 |
海洋学 | 374篇 |
天文学 | 12篇 |
综合类 | 118篇 |
自然地理 | 436篇 |
出版年
2024年 | 15篇 |
2023年 | 48篇 |
2022年 | 115篇 |
2021年 | 136篇 |
2020年 | 137篇 |
2019年 | 156篇 |
2018年 | 137篇 |
2017年 | 128篇 |
2016年 | 123篇 |
2015年 | 141篇 |
2014年 | 201篇 |
2013年 | 190篇 |
2012年 | 203篇 |
2011年 | 182篇 |
2010年 | 163篇 |
2009年 | 180篇 |
2008年 | 154篇 |
2007年 | 178篇 |
2006年 | 148篇 |
2005年 | 127篇 |
2004年 | 103篇 |
2003年 | 95篇 |
2002年 | 80篇 |
2001年 | 61篇 |
2000年 | 63篇 |
1999年 | 39篇 |
1998年 | 48篇 |
1997年 | 43篇 |
1996年 | 38篇 |
1995年 | 46篇 |
1994年 | 31篇 |
1993年 | 22篇 |
1992年 | 23篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有3600条查询结果,搜索用时 15 毫秒
61.
正Acta Geographica Sinica ISSN0375-5444 CN11-1856/P Acta Geologica Sichuan ISSN1006-0995 CN51-1273/P Acta Geologica Sinica ISSN0001-5717 CN11-1951/P Acta Geologica Sinica(English Edition)ISSN1000-9515 CN11-2001/P Acta Geoscientica Sinica ISSN1006-3021 CN11-3474/P Acta Micropalaeontologica Sinica ISSN1000-0674 CN32-1189/Q 相似文献
62.
Potential seasonal calibration for palaeoenvironmental reconstruction using skeletal microstructures and strontium measurements from the cold‐water coral Lophelia pertusa 下载免费PDF全文
63.
2015年台风“彩虹”过境后下山冷急流引起的南海北部海域异常海面降温 总被引:1,自引:0,他引:1
This study deals with a unusual cooling event after Typhoon Mujigea passed over the northern South China Sea(SCS) in October 2015. We analyze the satellite sea surface temperature(SST) time series from October 3 to 18,2015 and find that the cooling process in the coastal ocean had two different stages. The first stage occurred immediately after typhoon passage on October 3, and reached a maximum SST drop of –2℃ on October 7 as the usual cold wake after typhoon. The second stage or the unusual extended cooling event occurred after 7d of the typhoon passage, and lasted for 5d from October 10 to 15. The maximum SST cooling was –4℃ and occurred after 12d of typhoon passage. The mechanism analysis results indicate that after landing and moving northwestward to the Yunnan-Guizhou Plateau(YGP), Typhoon Mujigea(2015) met the westerly wind front on October 5. The lowpressure and positive-vorticity disturbances to the front triggered meridional air flow and low-pressure trough,thus induced a katabatic cold jet downward from the Qinghai-Tibet Plateau(QTP) passing through the YGP to the northwestern SCS. The second cooling reached the maximum SST drop 4d later after the maximum air temperature drop of –9℃ on October 11. The simultaneous air temperature and SST observations at three coastal stations reveal that it is this katabatic cold jet intrusion to lead the unusual SST cooling event. 相似文献
64.
Remote estimation of terrestrial evapotranspiration by Landsat 5 TM and the SEBAL model in cold and high‐altitude regions: a case study of the upper reach of the Shule River Basin,China 下载免费PDF全文
Evapotranspiration (ET) is an important expenditure in water and energy balances, especially on cold and high‐altitude land surfaces. Daily ET of the upper reach of the Shule River Basin was estimated using Landsat 5 TM data and the Surface Energy Balance Algorithm for Land (SEBAL) model. Based on observations made at the Suli station, the algorithms of land surface temperature and soil heat flux in SEBAL were modified. Land surface temperature was retrieved and compared with ground truth via three methods: the radiative transfer equation method, the mono‐window algorithm, and the single‐channel method. We selected the best of these methods, mono‐window algorithm, for estimating ET. The average error of daily ET estimated by the modified SEBAL model and measured by the eddy covariance system was 16.4%, with a root‐mean‐square error of 0.52 mm d?1. The estimated ET means were 3.09, 2.48, and 1.48 mm d?1 on June 9 (DOY 160), June 25 (DOY 176), and July 27 (DOY 208) of the year 2010, respectively. The average estimated ET on the glacier surface of all days was more than 3 mm d?1, a measurement that is difficult to capture in‐situ and has rarely been reported. This study will improve the understanding of water balance in cold, high‐altitude regions. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
65.
66.
67.
利用定性与定量分析手段,研究了川东北地区各类海相烃源岩中的单质硫及其地球化学特征。定性分析表明,该区海相烃源岩中的单质硫具有八硫环状结构和六硫状环结构两种晶体构型,由S8和S6两种同素异形体组成,其中S8具有相对较高的丰度。定量分析表明,该区海相烃源岩中的单质硫含量为0.91×10-6~375.88×10-6,具有很宽的分布范围,并且随着烃源岩分布区域、地层时代以及岩性的不同而发生明显变化,表现出强烈的非均质性分布特征。该区海相烃源岩中单质硫含量与有机碳含量之间存在正相关关系,说明单质硫主要发育在富有机质沉积的层段中。通过单质硫含量与总硫含量对比分析,间接证明了川东北地区各类海相烃源岩中赋存有丰富的有机含硫化合物。 相似文献
68.
鄂尔多斯盆地东北部构造热演化史的磷灰石裂变径迹分析 总被引:3,自引:0,他引:3
运用磷灰石裂变径迹(AFT)分析的构造热年代学研究方法,系统探讨鄂尔多斯盆地东北部不同区段中新生代以来的热演化历史,为盆地东北部石油和天然气等多种沉积能源矿产的勘探预测提供新的约束条件。模拟结果表明:盆地东北部经历了250~150 Ma缓慢埋藏增温过程,平均增温速率为0.9℃/Ma;150~120 Ma为快速增温阶段,平均增温速率高达2.1℃/Ma,地层温度达到最高,且均大于130℃。之后不同区段经历差异降温过程:北缘露头区经历了120~65 Ma快速降温,平均冷却速率约1.3℃/Ma;65~10 Ma缓慢降温,平均冷却速率约为0.4℃/Ma。南缘露头区及盆地沉降区则经历了120~30 Ma缓慢降温,平均冷却速率约为0.9℃/Ma;30~10 Ma快速降温,平均冷却速率约为1.5℃/Ma。10 Ma以来,盆地东北部整体抬升冷却,平均冷却速率约6.5℃/Ma。分析结果认为燕山中期构造热事件之最高热增温作用的关键时刻为(120±10)Ma,促成鄂尔多斯盆地东北部主要烃源岩层系的成熟生烃和大规模油气成藏。在后期的差异抬升冷却过程中,北缘露头区在65 Ma±通过了110℃等温面,南缘露头区及盆地的沉降区在30 Ma±通过了110℃等温面,有利于相邻地区原生油气藏的积聚和保存,古近纪晚期(30 Ma)尤其是新近纪晚期近10 Ma以来的强烈构造抬升作用有可能是引发原生油气藏调整—改造和次生成藏的关键因素。 相似文献
69.
70.
Employing the Unit Soil Carbon Amount (USCA) approach, soil carbon storage was calculated across the Northeast Plain of China based on the Multi-purpose Regional Geochemical Survey conducted in 2004 – 2006 (MRGS). The results indicated that the soil organic carbon (SOC) storage in topsoil (0 – 0.2 m), subsoil (0 – 1 m) and deep soil (0 – 1.8 m) was 768.1 Mt, 2978.4 Mt and 3729.2 Mt with densities of 3327.8 t/km2, 12,904.7 t/km2 and 16,157.5 t/km2, respectively. These values were consistent with national averages, whereas the soil carbon densities showed a clear increasing trend from the southern area of the Northeast Plain (Liaoning), to the middle (Jilin) and the northern Plain (Heilongjiang) — particularly in terms of topsoil carbon density, which increased from 2284.2, to 3436.7 and 3861.5 t/km2, respectively. In comparison to carbon data obtained from the Second National Soil Survey in 1984 – 1986 (SNSS), the topsoil SOC storage values from the MRGS were found to have decreased by 320.59 Mt (29.4%), with an average annual decline of 16.0 Mt (l.73%) over the 20 years. In the southern, middle and northern areas of the plain, soil carbon densities decreased by 1060.6 t/km2, 1646.4 t/km2 and 1300.2 t/km2, respectively, with an average value of 1389.0 t/km2 for the whole plain. These findings indicate that the decrease in soil carbon density varied according to the different ecosystems and land use types. Therefore, ratios of soil carbon density were calculated in order to study the carbon dynamic balance between ecosystems, and to further explore distribution characteristics, as well as the sequestration potential of SOC. 相似文献