全文获取类型
收费全文 | 1843篇 |
免费 | 378篇 |
国内免费 | 607篇 |
专业分类
测绘学 | 151篇 |
大气科学 | 14篇 |
地球物理 | 605篇 |
地质学 | 1705篇 |
海洋学 | 105篇 |
天文学 | 17篇 |
综合类 | 123篇 |
自然地理 | 108篇 |
出版年
2024年 | 10篇 |
2023年 | 33篇 |
2022年 | 50篇 |
2021年 | 77篇 |
2020年 | 83篇 |
2019年 | 93篇 |
2018年 | 73篇 |
2017年 | 88篇 |
2016年 | 95篇 |
2015年 | 118篇 |
2014年 | 161篇 |
2013年 | 128篇 |
2012年 | 118篇 |
2011年 | 149篇 |
2010年 | 123篇 |
2009年 | 170篇 |
2008年 | 167篇 |
2007年 | 150篇 |
2006年 | 150篇 |
2005年 | 108篇 |
2004年 | 115篇 |
2003年 | 104篇 |
2002年 | 65篇 |
2001年 | 56篇 |
2000年 | 59篇 |
1999年 | 44篇 |
1998年 | 50篇 |
1997年 | 41篇 |
1996年 | 37篇 |
1995年 | 22篇 |
1994年 | 27篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1983年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有2828条查询结果,搜索用时 15 毫秒
21.
兖州矿区煤中某些微量元素的赋存状态研究 总被引:6,自引:8,他引:6
微量元素的赋存状态决定其在煤的加工利用过程中释放的难易程度和毒性,弄清其在煤中的赋存状态,对准确评价元素的工艺性能、环境影响、作为副产品的可能性以及在地质意义上都是十分重要的。分析了微量元素在煤中的有机亲合性,采用数理统计方法,求得了微量元素与煤中有机显微组分、三态硫、灰分之间的相关性,并在浮沉实验的基础上,分析了微量元素的存在状态,通过研究向知,Ge、Ga、U、V、Cu、Th、Pb和Zn主要以无机态存在于煤中,F和Cl可能以有机态存在为主,As无机态和有机态存在的机率相似。 相似文献
22.
《The Professional geographer》2003,55(2):285-287
Patrick McCully. New York: Blackwell Publishing, 2001. ill and 416 pp., diags., notes, apps., and index. $69.95 cloth (ISBN 1856499014), $25.00 paper (ISBN 1856499022). Reviewed by Patrick H. Buckley, Department of Environmental Studies, Policy, Planning, Education, and Geography, Western Washington University, Bellingham, WA. 相似文献
23.
深圳市地质灾害及防治技术 总被引:3,自引:0,他引:3
张玉芳 《中国地质灾害与防治学报》2003,14(4):105-107,111
深圳市是一座新兴的海滨城市,市区东部与西部以花岗岩为主,中部以古老的变质岩为主,部分地区分布有砂岩、泥岩及变质的板岩、粉砂岩,深圳大断裂是区内主要的构造形迹。滑坡地质灾害主要分布在中部。在花岗岩地区主要变形为岩质高边坡崩塌、落石、坍塌等坡面变形;在变质岩、砂岩、泥岩地区发生多处滑坡。地质构造与地质灾害关系密切,深圳大断裂两侧为地质灾害多发区。防治边坡变形的工程措施即桩排、连续墙、基础为桩,锚杆框架;预应力锚索、预应力锚索框架护坡、预应力锚索抗滑桩,设置多级平台减载及琉干排水措施。深圳采用的治理地质灾害的工程措施经过多年的使用达到预期效果,但在上世纪90年代初完成的工程很少考虑工程措施与城市的景观协调。90年代后期已经考虑了工程完成后对城市环境的影响。因此采用防护措施以锚杆框架、预应力锚索框架工程为主,框架间植草,既有利于边坡稳定又有利于美化环境。 相似文献
24.
张发林 《地质灾害与环境保护》2003,14(1):11-14
通过对金风口片区地表的调查,分析了地面降沉、塌陷的原因;研究了塌陷对水源的影响;总结了水源干枯的规律及影响因素;并提出了防治的办法及合理化建议。 相似文献
25.
南京市玄武湖水下交通隧道环境地质评价 总被引:3,自引:0,他引:3
玄武湖地下交通隧道既在城市,又在水下,环境地质条件极为复杂,是一种脆弱环境下的典型的地质工程。本文对玄武湖地下交通隧道的环境地质条件特别是水文地质条件进行了评价,预测了可能出现的如水污染、地面沉降、地面塌陷、巷道突水等环境地质问题,并提出了相应的防治对策。 相似文献
26.
Decoupled seismic analysis of an earth dam 总被引:2,自引:0,他引:2
The seismic stability of an earth dam is evaluated via the decoupled displacement analysis using the accelerograms obtained by ground response analysis to compute the earthquake-induced displacements. The response analysis of the dam is carried out under both 1D and 2D conditions, incorporating the non-linear soil behaviour through the equivalent linear method. Ten artificial and five real accelerograms were used as input motions and four different depths were assumed for the bedrock.1D and 2D response analyses were in a fair agreement with the exception of the top third of the dam where only a 2D modelling of the problem could ensure that the acceleration field is properly described. The acceleration amplification ratio obtained in the 2D analyses was equal to about 2 in all the cases considered, consistently with data from real case histories.The maximum permanent displacements computed by the sliding block analysis were small, being less than 10% of the service freeboard; a satisfactory performance of the dam can then be envisaged for any of the seismic scenarios considered in the analyses. 相似文献
27.
This paper proposes a simple lattice model for collapse analysis of RC bridges subjected to earthquakes by using the extended distinct element method (EDEM). In the model, a concrete element consists of lumped masses connected to one another by springs, and a reinforcement bar is represented by a discrete model or an integrated model. The proposed lattice model is simple but its parameters are reasonably defined. It has fewer element nodes and connecting springs, which will be of benefit by shortening the CPU time. The processes to determine the initial stiffness of concrete and steel springs, the parameters of the constitutive model and the fracture criteria for springs are described. A re‐contact spring model is also proposed to simulate the re‐contact of the concrete after fracture of springs; and a general grid searching method is used to decrease the CPU time for judging re‐contact after fracture. The lattice model is assessed by numerical simulations and experiments. As an application, a damaged single‐column pier subjected to the Kobe Earthquake in 1995 is analysed by EDEM with the proposed model. The simulation results indicate that the proposed model predicts well qualitatively the collapse process of RC bridges. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
28.
本文系统研究了小浪底工程的岩体的强度特征,采用了室内试验,野外结构面统计,工程地质类比法、模型试验法和Hoek Brown的经验法,估算了工程岩体的力学指标,指出了上述各种方法中所存在的不足,认为在工程实践中,应尽可能使用多种估计方法,交叉校核所得参数,以提高参数的可靠性,保证工程的安全,节约投资。 相似文献
29.
We approach the reconstruction of the recent structural evolution of Stromboli volcano (Italy) and the analysis of the interplay between tectonics, gravity and volcanic deformation. By tying together structural, lithostratigraphic and rock mechanics data, we establish that since 100 ka BP, the edifice has faulted and jointed mainly along NE-striking planes. Faults mostly dip to the NW with normal displacement. Taking also into account the presence of a NW-trending regional least principal stress and of tectonic earthquake hypocenters inside the cone, we suggest that this fracturing can be related to the transmission of tectonic forces from the basement to the cone. Dyking concentrated along a main NE-trending weakness zone (NEZ) across the volcano summit, resembling a volcanic rift, whose geometry is governed by the tectonic field. In the past 13 ka, Stromboli experienced a reorganisation of the strain field, which was linked with the development of four sector collapses affecting the NW flank, alternating with growth phases. The tectonic strain field interplayed with dyking and fracturing related to unbuttressing along the collapse shoulders. We propose that tectonics control the geometry of dykes inside the cone and that these, in turn, contribute to destabilise the cone flanks. 相似文献
30.