全文获取类型
收费全文 | 4618篇 |
免费 | 1072篇 |
国内免费 | 1505篇 |
专业分类
测绘学 | 168篇 |
大气科学 | 10篇 |
地球物理 | 332篇 |
地质学 | 6106篇 |
海洋学 | 42篇 |
天文学 | 2篇 |
综合类 | 468篇 |
自然地理 | 67篇 |
出版年
2024年 | 64篇 |
2023年 | 157篇 |
2022年 | 185篇 |
2021年 | 213篇 |
2020年 | 199篇 |
2019年 | 272篇 |
2018年 | 179篇 |
2017年 | 191篇 |
2016年 | 311篇 |
2015年 | 291篇 |
2014年 | 477篇 |
2013年 | 304篇 |
2012年 | 343篇 |
2011年 | 382篇 |
2010年 | 373篇 |
2009年 | 354篇 |
2008年 | 305篇 |
2007年 | 331篇 |
2006年 | 325篇 |
2005年 | 227篇 |
2004年 | 204篇 |
2003年 | 198篇 |
2002年 | 172篇 |
2001年 | 182篇 |
2000年 | 151篇 |
1999年 | 144篇 |
1998年 | 119篇 |
1997年 | 108篇 |
1996年 | 84篇 |
1995年 | 67篇 |
1994年 | 69篇 |
1993年 | 47篇 |
1992年 | 51篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 12篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 5篇 |
1984年 | 11篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有7195条查询结果,搜索用时 15 毫秒
101.
102.
Mine ventilation planning in the 1980s 总被引:1,自引:0,他引:1
Malcolm J. Mcpherson 《Geotechnical and Geological Engineering》1984,2(3):185-227
Conclusions In this paper, the author has attempted to trace the development of mine ventilation planning from the traditional, manual and largely empirical methods of the past to the numerate computer-based techniques of the 1980s.The computer revolution has changed the face of many engineering disciplines, not least mine environmental engineering. Nevertheless, the mining industries of the world have not all been equally progressive in adapting to the flexibility, power and practical utilization of the new methodologies. It is, for example, incongruous that current textbooks on mine ventilation separate completely the topics of network analysis and ventilation planning with very little cross-referencing. Many of the current generation of mine ventilation engineers recognize the need to know about computers but find difficulty in translating this into their daily work. The growing availability of self-teaching, friendly software for personal microcomputers, coupled with interactive graphics, will assist greatly in promoting uncomplicated but powerful usage of computers.Young engineers now graduating from universities and colleges have been brought up in a computer-oriented environment and are competent in interacting with these machines. Indeed, they wonder how the job was ever done without magnetic data bases and high-speed computation aid. 相似文献
103.
胶莱盆地发育演化及其油气前景探讨 总被引:5,自引:0,他引:5
根据胶莱盆地区域地质特征,地球动力学背景及盆地中、新生代沉积特征分析,论述盆地的发育和演化阶段,并对胶莱盆地含油气前景进行探讨。 相似文献
104.
物探船拖缆姿态及拉力预报 总被引:1,自引:0,他引:1
针对海洋地震物探船布设探测网络实际工况的要求,提出一种拟合数值计算与模型实验结果预报拖缆姿态及拉力的方法,应用此方法进行多方案比较研究,获得优化的拖缆-扩展器-检测电缆组合探测系统。经海上拖航实验验证,此种预报方法查可行,预报精度完全能满足工程实用要求。 相似文献
105.
106.
孟恩陶勒盖大型银铅锌矿产于晚二叠世花岗岩杂岩体中心部位,矿床的主要容矿构造为一组沿东西向或近东西向展布向东收敛的脆性断裂带.成矿作用大致经历了4个阶段,形成了44条脉状矿体,按容矿构造分布划分为上、中、下3个矿脉群,其中主矿体9条,较大分支矿体9条,主矿体上下盘小矿体26条.矿床自下至上,具锌矿石-银铅锌矿石-银铅矿石的明显分带性.工业矿物主要为闪锌矿、方铅矿、深红银矿、黑硫银锡矿、自然银,主要有益组分为锌、铅、银,主要伴生有益组分有铟、镉、镓、铜、锡、金.矿床成因初步认为是裂隙充填脉状银铅锌多金属中温热液型,找矿标志明显. 相似文献
107.
爆破、矿震与地震的波谱差异 总被引:7,自引:3,他引:7
根据辽宁数字地震台网记录的爆破、矿震与地震的数字资料,采用波谱分析的方法,选取4个台站对其所在区域182个爆破、矿震与地震事件的记录,对比研究波谱特征,发现爆破、矿震与地震的纵横波拐角频率fc(P,S)及最大谱值等存在的差异。 相似文献
108.
109.
Schistose high-grade hematite orebodies (>64 wt % Fe) in the Iron Quadrangle, Minas Gerais, were formed in shear zones by hydrothermal alteration of the Paleoproterozoic Cauê BIF during the Transamazonian orogenesis. The ore is comprised of platy hematite (specularite) grains that define the foliation and overprint a relict banded martite-hematite fabric resembling, at first sight, a mylonite. The EBSD analyses of a m-scale schistose orebody from the Pau Branco mine show that specularite grew as elongated plates with the (00.1) plane parallel to the foliation. The population of the measured grain aspect ratio (GAR) is homogenous in different scales, and the longest axes of the crystals align with the stretching lineation (L//X) building continuous domains, or anastomose around stretched iron oxide aggregates and rootless fold hinges. The pole figure of the (00.1) plane shows usually a maximum centered on the pole of the foliation Z often elongated on a girdle perpendicular to the lineation L. The {10.4} pole figure has the configuration of a symmetric cleft girdle and the corresponding {11.0} and {10.0} pole figures present well developed girdles parallel to the foliation with an elongated maximum centered on X. Microstructures associated with crystal-plastic behavior and dynamic recrystallization are missing and the fabric of the orebody probably results from precipitation of strain-controlled oriented hematite plates and anisotropic syntaxial growth of favorably oriented grains with the intervention of hydrothermal fluids during Fe enrichment. The shear zone provided pathways for the percolation of mineralizing fluids under temperatures that varied from 140 to 350 °C or higher, under ductile or ductile–brittle conditions. The orthorhombic fabric and CPO (crystallographic preferred orientation) of the ore nevertheless contrast with the asymmetry of simple shear as observed in the torsion experiments by Siemes et al., 2010, Siemes et al., 2011, probably due to volume loss and possibly a flattening component of deformation in the ore zone. 相似文献
110.