全文获取类型
收费全文 | 2380篇 |
免费 | 359篇 |
国内免费 | 558篇 |
专业分类
测绘学 | 102篇 |
大气科学 | 202篇 |
地球物理 | 740篇 |
地质学 | 1262篇 |
海洋学 | 450篇 |
天文学 | 156篇 |
综合类 | 81篇 |
自然地理 | 304篇 |
出版年
2024年 | 8篇 |
2023年 | 30篇 |
2022年 | 70篇 |
2021年 | 60篇 |
2020年 | 67篇 |
2019年 | 113篇 |
2018年 | 86篇 |
2017年 | 82篇 |
2016年 | 92篇 |
2015年 | 102篇 |
2014年 | 135篇 |
2013年 | 166篇 |
2012年 | 109篇 |
2011年 | 142篇 |
2010年 | 127篇 |
2009年 | 156篇 |
2008年 | 158篇 |
2007年 | 150篇 |
2006年 | 164篇 |
2005年 | 156篇 |
2004年 | 132篇 |
2003年 | 109篇 |
2002年 | 104篇 |
2001年 | 99篇 |
2000年 | 83篇 |
1999年 | 77篇 |
1998年 | 64篇 |
1997年 | 61篇 |
1996年 | 61篇 |
1995年 | 56篇 |
1994年 | 61篇 |
1993年 | 36篇 |
1992年 | 27篇 |
1991年 | 23篇 |
1990年 | 31篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有3297条查询结果,搜索用时 31 毫秒
101.
Magnetic properties of the profiles of polluted and non-polluted soils. A case study from Ukraine 总被引:7,自引:0,他引:7
102.
Underground coal and copper ore exploitation in two Polish mining regions causes mining tremors and a series of other negative phenomena in the environment. Although these tremors are strictly connected with human activity, they differ considerably from other paraseismic vibrations. The moment of their occurrence is not to be foreseen likewise for earthquakes. The main problem discussed in the paper was formulated as the neural network evaluation of a relation between mining tremor energies, epicentral distances and acceleration response spectra. Back-propagation neural networks with Resilient back-propagation learning method were used. Each input vector included information about the mining tremor energy and the epicentral distance. Values of acceleration response spectrum were expected as the outputs of neural networks. Neurally evaluated spectra were compared with spectra computed on the basis of experimental data. After the network is trained and tested, it can be used for mapping of new data of mining tremor energies and epicentral distances into the spectra. Then, what is the substantial advantage of neural approach, the prediction of acceleration response spectra can be performed without recording of surface vibrations. In the light of the results, it is visible that the presented way of computation of acceleration response spectra can be peculiarly applied to prognosis of mining tremors influences on structures. 相似文献
103.
Introduction Estimation of an attenuation relationship for strong ground motion parameters has been an interesting research subject in the field of engineering seismology and has played a very important role in seismic safety evaluation, seismic zoning, seismic hazard evaluation of major constructions, etc. At present, the generally used parameters include peak acceleration, peak velocity and elastic response spectrum. Such parameters mentioned above are essentially independent of the duration… 相似文献
104.
Characterizing the properties of dissolved organic matter isolated by XAD and C-18 solid phase extraction and ultrafiltration 总被引:1,自引:0,他引:1
105.
106.
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
107.
108.
Roger Guérin 《Hydrogeology Journal》2005,13(1):251-254
109.
A set of Pennsylvanian coals from the North American coal basins, ranging in vitrinite reflectance from 0.65% to 1.75%, was examined, with special emphasis on the optical properties of pseudovitrinite. The results suggest that pseudovitrinite originates from the same material as telocollinite. Slits in the pseudovitrinite seem to have originated in situ due to low-temperature oxidation of woody material; their opening might have been facilitated by devolatilization during coalification. The dominant orientation of the slits is perpendicular to bedding. The intensity and orientation of the slits in pseudovitrinite could be important factors in predicting coalbed gas extraction from coal. 相似文献
110.
地统计学方法在土壤学中的应用 总被引:24,自引:1,他引:24
地统计学目前在土壤科学中得到广泛的应用和发展,成为认识土壤特征的一个重要工具.地统计学的空间变异函数和克里格插值等方法是土壤性状分析的主要手段,空间变异函数主要用于描述土壤理化性状空间变异特性,不同的插值方法可优化田间试验设计和田间采样方案,克里格插值方法则特别适用于未测量点土壤属性值的估测等.近年插值方法又被广泛应用于确定区域土壤环境容量和土壤质量标准,随机模拟则用于对土壤特性进行不确定性估计等.因而,地统计学方法对我国大量土壤学资料的整合与分析具有极大的应用前景. 相似文献