全文获取类型
收费全文 | 793篇 |
免费 | 153篇 |
国内免费 | 362篇 |
专业分类
大气科学 | 1篇 |
地球物理 | 90篇 |
地质学 | 1105篇 |
海洋学 | 16篇 |
天文学 | 1篇 |
综合类 | 72篇 |
自然地理 | 23篇 |
出版年
2023年 | 17篇 |
2022年 | 28篇 |
2021年 | 34篇 |
2020年 | 30篇 |
2019年 | 47篇 |
2018年 | 47篇 |
2017年 | 39篇 |
2016年 | 54篇 |
2015年 | 64篇 |
2014年 | 50篇 |
2013年 | 51篇 |
2012年 | 66篇 |
2011年 | 61篇 |
2010年 | 63篇 |
2009年 | 39篇 |
2008年 | 34篇 |
2007年 | 57篇 |
2006年 | 49篇 |
2005年 | 58篇 |
2004年 | 41篇 |
2003年 | 40篇 |
2002年 | 38篇 |
2001年 | 28篇 |
2000年 | 29篇 |
1999年 | 39篇 |
1998年 | 28篇 |
1997年 | 32篇 |
1996年 | 24篇 |
1995年 | 21篇 |
1994年 | 24篇 |
1993年 | 21篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1308条查询结果,搜索用时 218 毫秒
81.
系统研究了安家营子金矿区含金石英和无金石英的微量元素、流体包裹体、颜色、比重、发光、晶胞参数和红外光谱等标型特征,并依据所得数据对这两类石英进行了判别分析,提出了一系列的找矿标志。 相似文献
82.
利用x光电子能谱测试,发现金矿床石英中有负价氮的存在。这种氮的结合能为398eV士,该结合能氮的化合物有多种,氦均为负价态,其中有Si_3N_4Si的x光电子能谱有二个谱峰值:103.4eV和101.9eV,前者为siO_2的结合能,后者为Si_3N_4的结合能。N和Si的结合能均表明石英中有Si_3N_4为负三价态。石英中负价N可能为替代氧的类质同象成分。 相似文献
83.
泰山太古宙岩浆杂岩体的岩石化学和地球化学特征 总被引:1,自引:0,他引:1
本文将泰山岩浆杂岩分为两个成因系列,即:壳源深熔花岗岩系列,包括所有花岗岩;岩浆分异型闪长岩系列,包括所有闪长岩。 相似文献
84.
85.
石英裂变径迹蚀刻条件的对比实验研究 总被引:5,自引:0,他引:5
通过 40%的 HF溶液、KOH饱和溶液和 19 mol/L的 NaOH溶液这三种常用方法对大、小颗粒石英进行裂变径迹蚀刻实验的对比发现,用环氧树脂固定的小颗粒石英样品,不宜用 KOH饱和溶液(150 ℃)和 19 mol/L的 NaOH溶液(沸点,约 120 ℃)作为裂变径迹的蚀刻剂,宜用 40%的 HF溶液;三种方法均适宜于大颗粒石英,但不同的蚀刻方法蚀刻效率不同, 40%的 HF溶液(29 ℃)的蚀刻效率最高,且操作简单、安全性高.40%的 HF溶液最佳蚀刻时间为: 温度在 4 ℃左右(冬季)时为 40 min,温度在 29 ℃左右(夏季)时为 30 min,可在全年室内常温条件下操作. 相似文献
86.
Syntectonic plutons emplaced in shallow crust often contain intermediate-to low-temperature deformation microstructures but
lack a high-temperature, subsolidus deformation fabric, although the relict magmatic fabric is preserved. The Proterozoic
Vellaturu granite emplaced at the eastern margin of the northern Nallamalai fold belt, south India during the late phase of
regional deformation has a common occurrence of intermediate-to low-temperature deformation fabric, superimposed over magmatic
fabric with an internally complex pattern. But high-T subsolidus deformation microstructure and fabric are absent in this
pluton. The main crystal plastic deformation and fluid enhanced reaction softening was concentrated along the margin of the
granite body. Resulting granite mylonites show Y-maximum c-axis fabric in completely recrystallized quartz ribbonds, dynamic recrystallization of perthites, and myrmekite indicative
of fabric development under intermediate temperature (∼ 500–400°C). The weakly-deformed interior shows myrmekite, feldspar
microfracturing and limited bulging recrystallization of quartz. The abundance of prism subgrain boundaries is indicative
of continuing deformation through low-temperature (∼ 300°C). The relative rates of cooling influenced by advective heat transfer
and deformation of the pluton seem to control the overall subsolidus fabric development. The rapid advective heat transfer
from the interior in the early stages of subsolidus cooling was followed by slow cooling through intermediate temperature
window as a well-developed phyllosilicate rich mylonitic skin around the granite body slowed down conductive heat loss. Low-T
crystal plastic deformation of quartz was effected at a late stage of cooling and deformation of the shallow crustal granite
body emplaced within the greenschist facies Nallamlai rocks. 相似文献
87.
Qu JianJun Zhang KeCun Sun Bo Jiang ShengXiang Dong GuangRong Zu RuiPing Fang HaiYan 《中国科学D辑(英文版)》2007,50(9):1351-1358
The sound-producing mechanism of booming sand has long been a pending problem in the blown sand physics. Based on the earlier researches, the authors collected some silent sand samples from Teng- ger Desert, Australian Desert, Kuwait Desert, beaches of Hainan Island and Japanese coast as well as the soundless booming sand samples from the Mingsha Mountain in Dunhuang to make washing ex- periments. In the meantime the chemical corrosion experiment of glass micro-spheres, surface coating experiment and SEM examination were also conducted. The experimental results show that the sound production of booming sand seems to have nothing to do with the presence of SiO2 gel on the surface of sand grains and unrelated to the surface chemical composition of sand grains but is related to the resonance cavities formed by porous (pit-like) physical structure resulting from a number of factors such as wind erosion, water erosion, chemical corrosion and SiO2 gel deposition, etc. Its resonance mechanism is similar to that of Hemholz resonance cavity. Under the action of external forces, nu- merous spherical and sand grains with smooth surface and porous surface are set in motion and rub with each other to produce extremely weak vibration sound and then become audible sound by human ears through the magnification of surface cavity resonance. However the booming sands may lose their resonance mechanism and become silent sand due to the damping action caused by the invasion of finer particles such as dust and clay into surface holes of sand grains. Therefore, clearing away fine pollutants on the quartz grain surface is an effective way to make silent sand emit audible sound. 相似文献
88.
Recent developments in long term landform evolution modelling have created a new demand for quantitative salt weathering data, and in particular data describing the size distribution of the weathered rock fragments. To enable future development of rock breakdown models for use in landscape evolution and soil production models, laboratory work was undertaken to extend existing schist/salt weathering fragmentation studies to include an examination of the breakdown of sub‐millimetre quartz chlorite schist particles in a seasonally wet tropical climate. Laser particle sizing was used to assess the impact of different experimental procedures on the resulting particle size distribution. The results reveal that salt weathering under a range of realistic simulated tropical wet season conditions produces a significant degree of schist particle breakdown. The fragmentation of the schist is characterized by splitting of the larger fragments into mid‐sized product with finer material produced, possibly from the breakdown of mid‐sized fragments when weathering is more advanced. Salinity, the salt addition method and temperature were all found to affect weathering rates. Subtle differences in mineralogy also produce variations in weathering patterns and rates. It is also shown that an increase in drying temperature leads to accelerated weathering rates, however, the geometry of the fracture process is not significantly affected. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
89.
铜绿山铜铁矿床地质特征及岩浆岩与成矿关系探讨 总被引:10,自引:0,他引:10
铜绿山铜铁矿床位于鄂城-大幕山新华夏复合隆起带中部、阳新复式岩体西北端。矿体赋存于下三叠统大冶群第四至第七岩性段。矿床由12个矿体组成。矿区内岩浆活动频繁。通过对区内岩浆演化、岩石化学、岩性特征以及微量元素特征等方面系统研究,认为矿床成矿物源为铜绿山石英正长闪长玢岩岩体,含碱值偏高的中酸岩类是控制成矿元素富集及各类矿床组合的内在因素,岩浆的成矿专属性由岩浆本身特性决定。 相似文献
90.
通过对大别地区不同超高压岩石和同一超高压岩石中不同变形期次石英的变形特征的研究 ,探讨超高压岩石折返时的流变学特征和状态。运用野外构造解析、组构分析、透射电镜和应变分析发现 ,除榴辉岩中静态重结晶石英外 ,其它超高压岩石中石英均发生了强烈的塑性变形 ,波状消光、变形纹、变形条带等极为常见。石英石榴岩中石英交叉滑移位错的发育 ,说明经历了高温位错蠕变 ,其代表的差异应力为Δσ =78.92MPa。石英脉的变形是超高压岩石折返到中地壳以后的角闪岩相退变峰期产物 ,其差异应力为Δσ =2 5 .2MPa。超高压二云母片岩中石英典型的糜棱结构代表的差异应力为 :Δσ =5 9.6 1MPa。大别超高压岩石可能是在构造应力比较低的情况下区域隆升的结果 相似文献