全文获取类型
收费全文 | 2433篇 |
免费 | 473篇 |
国内免费 | 848篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 1篇 |
地球物理 | 108篇 |
地质学 | 3356篇 |
海洋学 | 84篇 |
天文学 | 2篇 |
综合类 | 114篇 |
自然地理 | 83篇 |
出版年
2024年 | 7篇 |
2023年 | 34篇 |
2022年 | 90篇 |
2021年 | 120篇 |
2020年 | 106篇 |
2019年 | 149篇 |
2018年 | 122篇 |
2017年 | 87篇 |
2016年 | 149篇 |
2015年 | 116篇 |
2014年 | 230篇 |
2013年 | 140篇 |
2012年 | 199篇 |
2011年 | 164篇 |
2010年 | 134篇 |
2009年 | 124篇 |
2008年 | 154篇 |
2007年 | 157篇 |
2006年 | 145篇 |
2005年 | 179篇 |
2004年 | 144篇 |
2003年 | 129篇 |
2002年 | 113篇 |
2001年 | 96篇 |
2000年 | 109篇 |
1999年 | 95篇 |
1998年 | 96篇 |
1997年 | 82篇 |
1996年 | 65篇 |
1995年 | 43篇 |
1994年 | 36篇 |
1993年 | 35篇 |
1992年 | 37篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 3篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有3754条查询结果,搜索用时 125 毫秒
101.
In the geological evolution of the Tarim Basin, many transgressions and relictions happened. So there have been plentiful sources of salt. Moreover, because of uttermost drought, a lot of salt has been deposited. It is possible to find potash salt in this area. In our fieldwork, we have found salt and brine in western Tarim Basin. Based on a geological survey and the characteristics of sedimentary facies and paleogeography, this paper deals with the geochemical parameters and discusses the possibility of formation of potash salt in terms of the chemical analyses of samples collected from western Tarim Basin. Results of brine analysis lead to some conclusions: most of these salt brines have eluviated from very thick halite beds, mainly chloridetype salt and this kind of halite does not reach the stage of potash deposition in all aspects; WKSL (Wukeshalu) occupies a noticeable place, and we should attach importance to this district because there have been some indicators of the occurrence of potash deposits as viewed from the contents of Br and K. Finally, low Br contents are recognized in the Tarim Basin as a result of salt aggradation, and this point of view has been proved by the results of this experiment and the data available. It cannot depend upon the index of Br to judge the evolution stage of halite. We must look for other facies of potash except marine facies. 相似文献
102.
103.
区域化探数据处理的几种分形方法 总被引:20,自引:1,他引:20
地球化学变量兼有随机性、确定性和区域结构性的特征,传统的数学方法难以精确地描述地球化学变量的空间分布规律,而新兴的分形几何是刻画空间不规则形体的一种比较有效的工具,且分维值可以表征空间不规则形体的确定性本质。基于分形原理,提出含量-总量法、空间分形插值法和分形趋势面法3种新的分形技术,应用于区域化探数据处理。在几个典型矿区应用后发现,上述分形方法不仅可以有效地模拟地球化学变量的空间分布特征,而且在保留原始有效异常信息的基础上可以更合理地区分地球化学变量的背景与异常,具有发现和强化弱异常信息的重要功效。 相似文献
104.
105.
106.
Gudrun Richter Joachim Wassermann Martin Zimmer Matthias Ohrnberger 《Journal of Volcanology and Geothermal Research》2004,135(4):331-342
In this paper we present densely sampled fumarole temperature data, recorded continuously at a high-temperature fumarole of Mt. Merapi volcano (Indonesia). These temperature time series are correlated with continuous records of rainfall and seismic waveform data collected at the Indonesian–German multi-parameter monitoring network. The correlation analysis of fumarole temperature and precipitation data shows a clear influence of tropical rain events on fumarole temperature. In addition, there is some evidence that rainfall may influence seismicity rates, indicating interaction of meteoric water with the volcanic system. Knowledge about such interactions is important, as lava dome instabilities caused by heavy-precipitation events may result in pyroclastic flows. Apart from the strong external influences on fumarole temperature and seismicity rate, which may conceal smaller signals caused by volcanic degassing processes, the analysis of fumarole temperature and seismic data indicates a statistically significant correlation between a certain type of seismic activity and an increase in fumarole temperature. This certain type of seismic activity consists of a seismic cluster of several high-frequency transients and an ultra-long-period signal (<0.002 Hz), which are best observed using a broadband seismometer deployed at a distance of 600 m from the active lava dome. The corresponding change in fumarole temperature starts a few minutes after the ultra-long-period signal and simultaneously with the high-frequency seismic cluster. The change in fumarole temperature, an increase of 5 °C on average, resembles a smoothed step. Fifty-four occurrences of simultaneous high-frequency seismic cluster, ultra-long period signal and increase of fumarole temperature have been identified in the data set from August 2000 to January 2001. The observed signals appear to correspond to degassing processes in the summit region of Mt. Merapi. 相似文献
107.
108.
109.
区域地球化学数据的归一化处理及应用 总被引:11,自引:0,他引:11
介绍了一种简单的勘查地球化学数据调整方法———归一化,该方法采用各批或各区块差异数据的平均值或中位数的衬值乘以参照值以获得元素的视含量,用于调整不同分析批次之间的系统误差,或不同背景区数据的差异;用2个实例详细介绍了该方法的应用效果。 相似文献
110.