全文获取类型
收费全文 | 2478篇 |
免费 | 516篇 |
国内免费 | 593篇 |
专业分类
测绘学 | 24篇 |
地球物理 | 810篇 |
地质学 | 2421篇 |
海洋学 | 90篇 |
天文学 | 8篇 |
综合类 | 102篇 |
自然地理 | 132篇 |
出版年
2024年 | 6篇 |
2023年 | 30篇 |
2022年 | 61篇 |
2021年 | 61篇 |
2020年 | 92篇 |
2019年 | 140篇 |
2018年 | 92篇 |
2017年 | 98篇 |
2016年 | 137篇 |
2015年 | 112篇 |
2014年 | 166篇 |
2013年 | 127篇 |
2012年 | 123篇 |
2011年 | 181篇 |
2010年 | 113篇 |
2009年 | 169篇 |
2008年 | 179篇 |
2007年 | 155篇 |
2006年 | 166篇 |
2005年 | 120篇 |
2004年 | 112篇 |
2003年 | 123篇 |
2002年 | 96篇 |
2001年 | 95篇 |
2000年 | 84篇 |
1999年 | 83篇 |
1998年 | 81篇 |
1997年 | 67篇 |
1996年 | 63篇 |
1995年 | 63篇 |
1994年 | 71篇 |
1993年 | 61篇 |
1992年 | 46篇 |
1991年 | 34篇 |
1990年 | 39篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 16篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1979年 | 1篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有3587条查询结果,搜索用时 141 毫秒
981.
龙脖河铜矿区(北段)岩浆岩及矿化 总被引:3,自引:0,他引:3
龙脖河铜矿产于中三叠统个旧组灰岩及其下伏地层中下三叠统火山岩建造中。矿床的形成与以红河断裂和阿龙古断裂为界的深海红河裂陷槽海相火山活动及后期的热液蚀变关系密切,矿化受地层、火山活动构造控制。富钠细碧角斑岩、火山碎屑岩、基性侵入岩为该区的主要岩浆岩类型。上述不同岩浆岩均有矿化产出,本文就区内岩浆岩的特征及其与矿化的关系作一简略的探讨。 相似文献
982.
983.
通过对地球自转速率变化推动构造运动的可能性以及地球自转角速度变化的原因和依据的讨论,提出地球自转惯性力差是决定板块相对运动趋势的主要动力学因素之一,揭示了加速期和减速期经、纬向构造之间的分布规律性,认为经、纬向构造之间的耦合关系是一种客观存在,同步耦合断裂就是由地球自转速率变化所反映的动力学状态决定的。同时,笔者对同步耦合断裂概念及耦合区构造组合的研究意义进行了探讨。 相似文献
984.
RobertD.JACOBI 《《地质学报》英文版》2003,77(4):491-503
2-D and 3-D densities of fractures are commonly used in mining safety design, natural gas and oil production in fractured reservoirs, and the characterization of subsurface flow and transportation systems in fractured rocks. However, many field data sets are collected in 1-D frequency (f) (e.g., scanlines and borehole data). We have developed an ARC/ INFO-based technology to calculate fracture frequency and densities for a given fracture network. A series of numerical simulations are performed in order to determine the optimal orientation of a scanline, along which the maximum fracture frequency of a fracture network can be obtained. We calculated the frequency (f) and densities (both D1 and D2) of 36 natural fracture trace maps, and investigated the statistical relationship between fracture frequency and fracture density D1, i.e. D1=1.340f+ 0.034. We derived analytical solutions for converting dimensional density (D1) to non-dimensional densities (D2 and D3) assuming that fracture length distribution f 相似文献
985.
在岩石边坡上采用持铁丝网喷粉植草新技术,以达到边坡防护,同时又起到了美化环境的效果,与往常的砌体护坡护面相比较,具有造价低、故果好、应用广泛等优点,这种技术适用于公路土建项目的岩石迫坡改造与防护上,同时还可用于城市建设中的大开挖边坡治理,采石场迫坡综合改造,这方面巳在湖南、广东等地区得到一定的应用,在当今日益重视环境保护的国内国际形势下,这种喷粉植草技术是值得普及推广的. 相似文献
986.
Rockfalls occur often along the state road SS241 Val d'Ega in the Val d'Ega Valley (South Tyrol, Italy). In order to protect the road and the traffic, stabilization works are necessary. Detailed geological and geomorphologic mapping along structural and geomechanic sections was carried out, and experimental rockfall trails were examined on the slope above the state road between km 3.550 and 3.830. Rockfall simulation, rock mass classification and an interpretation of field data, especially concerning joints, wrapped up the investigations. They helped find the specific need for stabilization work and its positioning along the slope. The stabilization works were completed on February 2002. Another important aspect concerns ongoing geotechnical investigations and stabilization works urgently realised during autumn 1999.
This paper is a practical approach in solving rockfall problems along public roads. It should be considered as a workbook for university personnel and also for professional geologists. 相似文献
987.
A Methodology for Reliability-Based Design of Rock Slopes 总被引:10,自引:0,他引:10
Summary A reliability-based methodology for the design of rock slopes, that can easily be implemented by the practicing engineers
is proposed. The advanced first-order second-moment (AFOSM) method is adopted as the reliability assessment model and its
application is illustrated for the case of plane failure. A model is developed within the framework of first-order second-moment
approach to analyze the uncertainties underlying the in situ shear strength properties of rock discontinuities. Here, particular
emphasis is given on the assessment of uncertainties related to the shear characteristics of clean, unfilled rock discontinuities
under low normal stress levels. An extensive literature survey on the shear characteristics of discontinuities is carried
out in order to collect data for the quantification of uncertainties. The data extracted from this literature survey are classified
and reprocessed so that they can be utilized in the uncertainty analysis model. A user friendly software called ROCKREL is
developed to carry out the numerical computations and to make the proposed design format more practical.
Received April 16, 2001; accepted June 10, 2002; Published online November 19, 2002
Authors' address: Prof. Celal Karpuz, Middle East Technical University, Faculty of Engineering, Department of Mining Engineering, 06531 Ankara,
Turkey; e-mail: karpuz @metu.edu.tr 相似文献
988.
989.
990.
根据湖南地层发育情况,依国际地层划分标准和中国地层指南要求,将湖南省境内原震旦纪早世划归新元古代南华纪,地层系统可分为3个相区。综合已有同位素测年数据,初步建立起南华纪年代构造格架,确立南华纪底界年龄为800Ma左右,顶界年龄为700Ma左右. 相似文献