全文获取类型
收费全文 | 4786篇 |
免费 | 1005篇 |
国内免费 | 1327篇 |
专业分类
测绘学 | 608篇 |
大气科学 | 911篇 |
地球物理 | 985篇 |
地质学 | 2682篇 |
海洋学 | 628篇 |
天文学 | 98篇 |
综合类 | 484篇 |
自然地理 | 722篇 |
出版年
2024年 | 31篇 |
2023年 | 87篇 |
2022年 | 298篇 |
2021年 | 363篇 |
2020年 | 286篇 |
2019年 | 385篇 |
2018年 | 323篇 |
2017年 | 286篇 |
2016年 | 320篇 |
2015年 | 305篇 |
2014年 | 322篇 |
2013年 | 382篇 |
2012年 | 391篇 |
2011年 | 360篇 |
2010年 | 345篇 |
2009年 | 302篇 |
2008年 | 300篇 |
2007年 | 258篇 |
2006年 | 251篇 |
2005年 | 201篇 |
2004年 | 170篇 |
2003年 | 124篇 |
2002年 | 209篇 |
2001年 | 151篇 |
2000年 | 121篇 |
1999年 | 103篇 |
1998年 | 74篇 |
1997年 | 60篇 |
1996年 | 63篇 |
1995年 | 55篇 |
1994年 | 43篇 |
1993年 | 28篇 |
1992年 | 29篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1957年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有7118条查询结果,搜索用时 125 毫秒
111.
112.
On August 5, 2001, Shanghai was struck by a torrential rainfall due to the passage of a tropical depression (TD). The rainfall intensity has been the strongest in recent 50 years. In this paper, a set of mesoscale re-analyses data and the planetary boundary layer observation from a wind profiler are used to understand the possible mechanism of such a heavy rain. Results show that the outburst of a southerly jet in the lower atmosphere triggered the explosive development of cyclonically vertical vorticity in the region with steep potential temperature surfaces in front of the TD; while the cyclonic vorticity increased notably at higher levels due to the small atmospheric vertical stability of westerly currents in the vicinity of Shanghai. The simultaneous sharp development of cyclonic vorticity at different levels should be the main cause for the torrential rainfall. 相似文献
113.
Based on the inversion method of 2D velocity structure and interface, the crustal velocity structures of P-wave and S-wave along the profile L1 are determined simultaneously with deep seismic sounding data in Changbaishan Tianchi volcanic region, and then its Poisson's ratio is obtained. Calculated results show that this technique overcomes some defects of traditional forward calculation method, and it is also very effective to determine Poisson's ratio distribution of deep seismic sounding profile, especially useful for study on volcanic magma and crustal fault zone. Study result indicates that there is an abnormally high Poisson's ratio body that is about 30 km wide and 12 km high in the low velocity region under Tianchi crater. Its value of Poisson's ratio is 8% higher than that of surrounding medium and it should be the magma chamber formed from melted rock with high temperature. There is a high Poisson's ratio zone ranging from magma chamber to the top of crust, which may be the uprise passage of hot substance. The lower part with high Poisson's ratio, which stretches downward to Moho, is possibly the extrusion way of hot substance from the uppermost mantle. The conclusions above are consistent with the study results of both tomographic determination of 3D crustal structure and magnetotelluric survey in this region. 相似文献
114.
115.
Sedimentation rates in the Wanggang salt marshes, Jiangsu 总被引:1,自引:0,他引:1
WANGAijun GAOShu JIAJianjun PANShaoming 《地理学报(英文版)》2005,15(2):199-209
1 IntroductionLand-ocean interaction in coastalzone is one of the key m atters of the International G eosphereand Biosphere Program (IG BP). The key problem s of the second phase in the next decadeinclude the m aterial cycle, the system evolution process … 相似文献
116.
Jia Xia 《Engineering Geology》2005,78(3-4):209-214
The ancient gravel stratum near Nanjing, China, is a major stratum of Cenozoic age along the middle–lower reaches of the Yangtze River. This paper first presents a typical geological profile and material composition of the ancient gravel stratum, and then discusses its geologic origin, soil–rock-forming processes, engineering mechanical properties, and their relations. These analyses are useful for city planning, geotechnical engineering, construction, and characterization of the geological environment in the Nanjing area. 相似文献
117.
118.
晚新生代温泉沉积盆地,是青藏高原腹地在南北向挤压、东西向伸展的构造背景下,沿南北向边界走滑断层,经边界正断层和内部张剪断层的进一步发展而形成的近南北向单断单剪楔形半地堑活动沉积盆地。它可能代表了晚新生代青藏高原第三期强烈挤压隆升事件,是侧向向东剪切挤出的结果。笔者以盆地充填序列和TL、ESR测年资料为主要依据,推测唐古拉山在30 0~2 5 0ka前后全面进入冰冻圈;而以温泉活动沉积盆地为代表的中更新世晚期(2 2 4 .0~1 5 0 .2ka)的冰碛 冰水堆积则对应于青藏高原第三期隆升的断陷盆地发育阶段;中更新世晚期—晚更新世中期(1 4 4 .0~5 6ka)为湖相沉积;晚更新世中期至今(35~0ka)对应于高原缓慢隆升与夷平发育阶段。长江溯源在35ka切割通天河盆地,形成通天河;而在1 6ka侵蚀切穿雁石坪 温泉兵站峡谷,形成布曲河。 相似文献
119.
Zizhen Jin Qiudong Zhao Xiang Qin Jingtian Zhang Hui Zhang Jia Qin Yu Qin Hongyuan Li Jizu Chen Yushuo Liu Yanzhao Li Lihui Wang 《水文研究》2021,35(10):e14392
Quantifying the impact of landscape on hydrological variables is essential for the sustainable development of water resources. Understanding how landscape changes influence hydrological variables will greatly enhance the understanding of hydrological processes. Important vegetation parameters are considered in this study by using remote sensing data and VIC-CAS model to analyse the impact of landscape changes on hydrology in upper reaches of the Shule River Basin (URSLB). The results show there are differences in the runoff generation of landscape both in space and time. With increasing altitude, the runoff yields increased, with approximately 79.9% of the total runoff generated in the high mountains (4200–5900 m), and mainly consumed in the mid-low mountain region. Glacier landscape produced the largest runoff yields (24.9% of the total runoff), followed by low-coverage grassland (LG; 22.5%), alpine cold desert (AL; 19.6%), mid-coverage grassland (MG; 15.6%), bare land (12.5%), high-coverage grassland (HG; 4.5%) and shrubbery (0.4%). The relative capacity of runoff generation by landscapes, from high to low, was the glaciers, AL, LG, HG, MG, shrubbery and bare land. Furthermore, changes in landscapes cause hydrological variables changes, including evapotranspiration, runoff and baseflow. The study revealed that HG, MG, and bare land have a positive impact on evapotranspiration and a negative impact on runoff and baseflow, whereas AL and LG have a positive impact on runoff and baseflow and a negative impact on evapotranspiration. In contrast, glaciers have a positive impact on runoff. After the simulation in four vegetation scenarios, we concluded that the runoff regulation ability of grassland is greater than that of bare land. The grassland landscape is essential since it reduced the flood peak and conserved the soil and water. 相似文献
120.