全文获取类型
收费全文 | 7468篇 |
免费 | 1176篇 |
国内免费 | 1908篇 |
专业分类
测绘学 | 423篇 |
大气科学 | 2034篇 |
地球物理 | 1849篇 |
地质学 | 3400篇 |
海洋学 | 984篇 |
天文学 | 365篇 |
综合类 | 711篇 |
自然地理 | 786篇 |
出版年
2024年 | 15篇 |
2023年 | 82篇 |
2022年 | 288篇 |
2021年 | 323篇 |
2020年 | 260篇 |
2019年 | 335篇 |
2018年 | 359篇 |
2017年 | 314篇 |
2016年 | 414篇 |
2015年 | 348篇 |
2014年 | 404篇 |
2013年 | 450篇 |
2012年 | 348篇 |
2011年 | 377篇 |
2010年 | 347篇 |
2009年 | 419篇 |
2008年 | 331篇 |
2007年 | 307篇 |
2006年 | 281篇 |
2005年 | 281篇 |
2004年 | 209篇 |
2003年 | 239篇 |
2002年 | 206篇 |
2001年 | 228篇 |
2000年 | 284篇 |
1999年 | 429篇 |
1998年 | 329篇 |
1997年 | 333篇 |
1996年 | 327篇 |
1995年 | 279篇 |
1994年 | 229篇 |
1993年 | 206篇 |
1992年 | 163篇 |
1991年 | 137篇 |
1990年 | 118篇 |
1989年 | 120篇 |
1988年 | 105篇 |
1987年 | 56篇 |
1986年 | 58篇 |
1985年 | 44篇 |
1984年 | 42篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 24篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1976年 | 6篇 |
1973年 | 7篇 |
1958年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 861 毫秒
191.
192.
山西奇村地热田的勘察与研究 总被引:2,自引:0,他引:2
通过近期对山西省忻州市奇村地热田进行的实地物化探勘察发现:地下热水的分布范围内视电阻率普遍偏低,且水温愈高,视电阻率愈低,在α 卡异常处均有地下热水存在。该地热田的热水分布区内的隔水层和盖层为亚粘土,粘土层。基地下热水的水化学类型为氯化物硫酸钠型及氯化钠型,热田热水赋存和滞留于浅层次生热储内。 相似文献
193.
194.
In this paper, we study the relationship between Neogene volcanism and Holocene earthquakes in the Tanlu fault, eastern China. We find that fault segments through which Neogene and Quaternary magma have extruded do not show Holocene slip because they are covered by unfaulted basalts. In contrast, fault branches that are away from the Quaternary volcanic centers display Quaternary faulting and are responsible for earthquakes as recorded both historically and geomorphologically. Therefore, magma intrusion appears to modify fault activity in two different ways: (1) within the faults, the cooling magma serves as a cohesion or barrier, welding the faults so that they become stronger in resisting slip; (2) beneath the faults, the upwelling magma promotes slip of faults above the magma body, and hence generation of earthquakes. Physically, the first case results from contraction of the cooling magma, which causes a relative increase in fault-normal stress so that the fault failure resistance is enhanced. The second case results from the upward dynamic force and the heat brought in by the magma body, both of which cause the effective fault-normal stress to decrease so that the fault failure resistance is reduced. That could explain why earthquakes occur on faults bypassing the volcanic centers as typified in the Yishu fault zone and in the regions where heat flows are relatively high as shown in the Bohai Bay area. 相似文献
195.
介绍了安阳电厂冷却塔碎石桩复合地基静载、动力触探、瑞利波法系列原位试验。根据试验结果,对冷却塔地基加固与改良效果及施工质量进行了评价。 相似文献
196.
本文对Ni40Mn30Fe30合金与在不同焙烧温度下得到的含水叶蜡,在高温超高压下的反应进行了实验研究,温度测至1420℃,压是至5.5GPa,研究了该反应的物质-化学机制,以及反应速率与温度,压力,含水量等参数的关系,对高压下物质迁移运动的固有特征进行了探讨。 相似文献
197.
is paper is concerned with the geochemical features of major elements,transition metal elements,large ion lithophile elements,rare-earth elements and Sr isotopes in alkaline-ul-trabasic rocks in the Jijie complex of Lufeng,Yunnan Province,which is located in southern Sichuan-Yunnan rift zone,one of Luoci alkaline-ultrabasic complexes in central Ynnnan,Moreover,its origin pertaining primary magma,magma soure region,fractional crystallization,etc.are also discussed in the present paper. 相似文献
198.
199.
200.
Screening Effect of the Diffusive Boundary Layer in Sediments of Lake Aha in the Suburbs of Guiyang City,Guizhou Province 总被引:6,自引:0,他引:6
The redox cycle of iron and manganese is a major geochemica process at the boundary layers of lake sediments.Lake Aha,which lies in the suburbs of Guiyang City,Guizhou Province,China,is a medium-sized artificial reservoir with seasonally anoxic hypolimnion,Long-term sedimentary accumulation of iron and manganese resulted in their enrichment in the upper sediments,In the anoxic season,Fe^2 and Mn^2 ,formed by diological oxidation,would diffuse up to overlying waters from sediments.However,the concentration of oxidation,would diffuse up to overlying waters from sediments,However,the concentration of Fe^2 increased later and decreased earlier than that of Mn^2 .Generally,sulfate reduction occurred at 6 cm below the sediment-water interface.Whereas,in the anoxic season.the reduction reached upper sediments,inhibiting the release of Fe^2 ,The Fe concentration of anoxic water is quickly decreased from high to low as a result of reduction of the suplhur system. 相似文献