全文获取类型
收费全文 | 223篇 |
免费 | 29篇 |
国内免费 | 29篇 |
专业分类
测绘学 | 27篇 |
大气科学 | 7篇 |
地球物理 | 57篇 |
地质学 | 85篇 |
海洋学 | 9篇 |
天文学 | 4篇 |
综合类 | 23篇 |
自然地理 | 69篇 |
出版年
2023年 | 1篇 |
2022年 | 13篇 |
2021年 | 10篇 |
2020年 | 7篇 |
2019年 | 15篇 |
2018年 | 12篇 |
2017年 | 16篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 21篇 |
2012年 | 13篇 |
2011年 | 18篇 |
2010年 | 11篇 |
2009年 | 5篇 |
2008年 | 11篇 |
2007年 | 13篇 |
2006年 | 17篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有281条查询结果,搜索用时 953 毫秒
161.
A. Lougear M. Grodzicki C. Bertoldi A. X. Trautwein K. Steiner G. Amthauer 《Physics and Chemistry of Minerals》2000,27(4):258-269
The different Fe2+ lattice sites in iron-rich chlorites have been characterized by Mössbauer spectroscopy and molecular orbital calculations in local density approximation. The Mössbauer measurements were recorded at 77?K within a small velocity range (±3.5?mm?s?1) to provide high energy resolution. Additionally, measurements were recorded in a wider velocity range (±10.5?mm?s?1) at temperatures of 140, 200, and 250?K in an applied field (7?T) parallel to the γ-beam. The zero-field spectra were analyzed with discrete Lorentzian-shaped quadrupole doublets to account for the Fe2+ sites M1, M2, and M3 and with a quadrupole distribution for Fe3+ sites. Such a procedure is justified by the results obtained from MO calculations, which reveal that different anion (OH?) distributions in the first coordination sphere of M1, M2, and M3 positions have more influence on the Fe2+ quadrupole splitting than cationic disorder. The spectra recorded in applied field were analyzed in the spin-Hamiltonian approximation, yielding a negative sign for the electric field gradient (efg) of Fe2+ in the M1, M2, and M3 positions. The results of the MO calculations are in quantitative agreement with experiment and reveal that differences in the quadrupole splittings (ΔE Q ), their temperature dependence and in the isomer shifts (δ) of Fe2+ in M1, M2, and M3 positions can theoretically by justified. Therefore, the combined Mössbauer and MO investigation shows that the three Fe2+ lattice sites in the chlorites investigated here can be discriminated according to their ΔE Q -δ parameter pairs. With the calculated average iron-oxygen bond strength, the MO study provides an explanation for the observed trend that the population of the three lattice sites by Fe2+ increases according to the relation M1?相似文献
162.
163.
164.
165.
166.
Minha Choi 《水文研究》2012,26(4):597-603
In the past few decades, there have been great developments in remotely sensed soil moisture, with validation efforts using land surface models (LSMs) and ground‐based measurements, because soil moisture information is essential to understanding complex land surface–atmosphere interactions. However, the validation of remotely sensed soil moisture has been very limited because of the scarcity of the ground measurements in Korea. This study validated Advanced Microwave Scanning Radiometer E (AMSR‐E) soil moisture data with the Common Land Model (CLM), one of the most widely used LSMs, and ground‐based measurements at two Korean regional flux monitoring network sites. There was reasonable agreement regarding the different soil moisture products for monitoring temporal trends except National Snow and Ice Data Centre (NSIDC) AMSR‐E soil moisture, albeit there were essential comparison limitations by different spatial scales and soil depths. The AMSR‐E soil moisture data published by the National Aeronautics and Space Administration and Vrije Universiteit Amsterdam (VUA) showed potential to replicate temporal variability patterns (root‐mean‐square errors = 0·10–0·14 m3 m?3 and wet BIAS = 0·09 ? 0·04 m3 m?3) with the CLM and ground‐based measurements. However, the NSIDC AMSR‐E soil moisture was problematic because of the extremely low temporal variability and the VUA AMSR‐E soil moisture was relatively inaccurate in Gwangneung site characterized by complex geophysical conditions. Additional evaluations should be required to facilitate the use of recent and forthcoming remotely sensed soil moisture data from Soil Moisture and Ocean Salinity and Soil Moisture Active and Passive missions at representative future validation sites. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
167.
Analysis of meteorological conditions for the base of marine sports in the 26th Summer Universiade in Shenzhen in 2011 总被引:1,自引:1,他引:0
Based on the real-time wind direction and speed data from an automatic meteorological monitoring network in Shenzhen, the wind characteristics of Jue Diao Sha maritime area are analyzed. As indicated in the results, the wind speed of this area is higher than that over the land, the average wind speed is above 3 m/s and the probability for the maximum wind speed to drop below 20 m/s is above 90%. Moreover, the probability for the hourly swing angle of wind direction to become less than 50o is above 80%, suggesting that the wind conditions in the Jue Diao Sha area could meet the requirements of the sporting events. According to the numerical simulation, this area is the best selected site among three candidates. Furthermore, the characteristics of daily land and sea breezes are such that it is suggested the game will be best carried out from 1000 to 1700 Beijing Standard Time. 相似文献
168.
研究具有代表性的Kostzadinov and Yamazaki液化识别方法的可行性,特别是对软土和液化场地的识别能力.选择包含了13个软土场地的52个场地实际地震纪录,分析结果表明,该方法识别成功率随场地类别变软而显著降低,对中硬、中软和软土非液化场地成功率分别为100%、70.6%和46.2%,对液化场地成功率为6... 相似文献
169.
考古学发现江准东部已有十多处新石器文化遗址,形成了有区域特征的文化序列.分别为龙虬庄文化(7 000? 6 300~5 500 aBP)、大汶口文化(5 500~4 600 aBP)和龙山(岳石)文化(4 300~3 450 aBP).在中全新世适宜期,受气候、长江、淮河三角洲的发育和海面变化的共同作用,江淮东部约7 ... 相似文献
170.
位于黄河中游的河东地区作为早期国家文明起源、发展的重要地区,其文化遗址的分布特征可以印证我国早期文明的演进趋势。以河东地区2070处早期文化遗址为研究对象,运用GIS空间分析法,分析其时空分布规律及其地理环境影响因素。结果表明:(1)旧石器时代文化遗址主要分布在海拔较高的山地中,且无明显聚集特征。(2)新石器时代,文化遗址的分布向中部平坦、水源充足的运汾盆地转移。(3)夏商周时期,文化遗址的分布在运汾盆地内进一步发展,且出现由政治因素导向的显著性集聚特征。这一演变规律反映了早期人类从自然散聚到有组织集聚的文明演变过程。 相似文献