全文获取类型
收费全文 | 1867篇 |
免费 | 363篇 |
国内免费 | 430篇 |
专业分类
测绘学 | 88篇 |
大气科学 | 472篇 |
地球物理 | 502篇 |
地质学 | 801篇 |
海洋学 | 269篇 |
天文学 | 122篇 |
综合类 | 205篇 |
自然地理 | 201篇 |
出版年
2024年 | 4篇 |
2023年 | 26篇 |
2022年 | 69篇 |
2021年 | 72篇 |
2020年 | 61篇 |
2019年 | 74篇 |
2018年 | 75篇 |
2017年 | 72篇 |
2016年 | 82篇 |
2015年 | 78篇 |
2014年 | 67篇 |
2013年 | 91篇 |
2012年 | 91篇 |
2011年 | 105篇 |
2010年 | 103篇 |
2009年 | 96篇 |
2008年 | 94篇 |
2007年 | 124篇 |
2006年 | 94篇 |
2005年 | 62篇 |
2004年 | 49篇 |
2003年 | 74篇 |
2002年 | 51篇 |
2001年 | 57篇 |
2000年 | 82篇 |
1999年 | 128篇 |
1998年 | 104篇 |
1997年 | 80篇 |
1996年 | 80篇 |
1995年 | 60篇 |
1994年 | 63篇 |
1993年 | 62篇 |
1992年 | 38篇 |
1991年 | 28篇 |
1990年 | 29篇 |
1989年 | 20篇 |
1988年 | 31篇 |
1987年 | 12篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有2660条查询结果,搜索用时 93 毫秒
61.
Chemical composition of upper crust in eastern China 总被引:4,自引:0,他引:4
In an area of 3.3×106 km2 within eastern China, 28 253 rock samples were collected systematically and combined into 2718 composite samples which were
analyzed by 15 reliable methods using national preliminary certified reference materials (CRMs) for data quality monitoring.
The average chemical compositions of the exposed crust, the sedimentary cover and the exposed basement as well as the upper
crust for 76 chemical elements in eastern China are given.
A key basic geology projcct supported by Ministry of Geology and Mineral Resources of China. 相似文献
62.
The paper introduces the horizontal crustal movement obtained from GPS observations in the regional networks (including the
basic network and the fiducial network) of the Crustal Movement Observation Network of China (CMONOC) carried out in 1999
and 2001. This paper is characterized by the acquisition of the horizontal displacement velocities during the period from
1999 to 2001 at the observation stations in the regional networks with datum definition of a group of stable stations with
small mutual displacements in east China. Based on the most detailed map of horizontal crustal movement in Chinese mainland,
the division of blocks, their displacements and deformations are studied. An approach to analysis of the intensity of the
horizontal crustal deformation is proposed. The general characteristics of the recent horizontal crustal movement in Chinese
mainland and that before the Kunlunshan earthquake of M=8.1 on November 14, 2001 are analyzed.
Foundation item: The National Development and Programming Project for Key Basic Research (95-13-03-07). 相似文献
63.
64.
65.
66.
67.
致密砂岩的形成机制及其地质意义——以塔里木盆地英南2井为例 总被引:7,自引:0,他引:7
砂质岩的孔隙和喉道被网格状粘土矿物和次生加大矿物充填成微细孔喉状结构时,形成具有较高毛细管压力的致密砂岩。它与地层水发生水锁效应,可大大降低渗透率,成为致密砂岩盖层。当含水饱和度在50%以下时,束缚水饱和度比较低,致密砂岩储层可以产气;当含水饱和度在50%~90%区间时,具有较高的束缚水饱和度,相对渗透率非常低,它既不能产气也不能产水,反映为渗透率瓶颈区(具有盖层性质);当含水饱和度大于90%以上时,致密砂岩储层仅微量产水。塔里木盆地英南2井侏罗系气藏盖层由致密砂岩构成,不含水时的气体渗透率在(0.027~0.081)×10-3μm2,不能构成封堵;当含水饱和度达到60%以上时,相对渗透率几乎为零,构成有效盖层。 相似文献
68.
Roger Guérin 《Hydrogeology Journal》2005,13(1):251-254
69.
70.
Hairu Li Gang Liu Ju Gu Hong Chen Hongqiang Shi Mohamed A. M. Abd Elbasit Feinan Hu 《水文研究》2021,35(2):e14060
Aggregate disintegration is a critical process in soil splash erosion. However, the effect of soil organic carbon (SOC) and its fractions on soil aggregates disintegration is still not clear. In this study, five soils with similar clay contents and different contents of SOC have been used. The effects of slaking and mechanical striking on splash erosion were distinguished by using deionized water and 95% ethanol as raindrops. The simulated rainfall experiments were carried out in four heights (0.5, 1.0, 1.5 and 2.0 m). The result indicated that the soil aggregate stability increased with the increases of SOC and light fraction organic carbon (LFOC). The relative slaking and the mechanical striking index increased with the decreases of SOC and LFOC. The reduction of macroaggregates in eroded soil gradually decreased with the increase of SOC and LFOC, especially in alcohol test. The amount of macroaggregates (>0.25 mm) in deionized water tests were significantly less than that in alcohol tests under the same rainfall heights. The contribution of slaking to splash erosion increased with the decrease of heavy fractions organic carbon. The contribution of mechanical striking was dominant when the rainfall kinetic energy increased to a range of threshold between 9 J m−2 mm−1 and 12 m−2 mm−1. This study could provide the scientific basis for deeply understanding the mechanism of soil aggregates disintegration and splash erosion. 相似文献