全文获取类型
收费全文 | 357篇 |
免费 | 47篇 |
国内免费 | 178篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 8篇 |
地球物理 | 16篇 |
地质学 | 480篇 |
海洋学 | 35篇 |
综合类 | 33篇 |
自然地理 | 8篇 |
出版年
2024年 | 3篇 |
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 19篇 |
2015年 | 13篇 |
2014年 | 25篇 |
2013年 | 20篇 |
2012年 | 17篇 |
2011年 | 28篇 |
2010年 | 23篇 |
2009年 | 22篇 |
2008年 | 16篇 |
2007年 | 27篇 |
2006年 | 26篇 |
2005年 | 26篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 23篇 |
2000年 | 18篇 |
1999年 | 22篇 |
1998年 | 15篇 |
1997年 | 27篇 |
1996年 | 18篇 |
1995年 | 18篇 |
1994年 | 17篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有582条查询结果,搜索用时 171 毫秒
521.
522.
The Haenam–Jindo area, located on the southwestern margin of the Korean Peninsula, was the site of vigorous volcanic activity during the Late Cretaceous and Early Tertiary periods. Large parts of the area record strong hydrothermal alteration, and there exist many clay–alunite and gold–silver deposits. We undertook potassium–argon (K–Ar) age dating of five mineral samples (including adularia, sericite and alunite) from the Eunsan, Moisan and Gasado epithermal gold–silver deposits in this area. The purities of the samples were confirmed by X‐ray diffraction analysis. The K–Ar ages of adularia from the Eunsan deposit and adularia and sericite from the Moisan deposit (related to gold–silver mineralization) are 75.0 ± 1.6, 74.7 ± 1.6 and 75.1 ± 1.6 Ma, respectively. The similarity of these ages, combined with the close proximity and similar geochemical characteristics of the deposits, indicates that the mineralization occurred as part of a single hydrothermal system. The K–Ar ages of alunite at the surface and adularia at depth within the Gasado deposit are 82.2 ± 1.9 and 70.7 ± 1.9 Ma, respectively, revealing that the clay–alunite and gold–silver mineralization formed at different ages. K–Ar age data indicate that the gold–silver mineralization in this area occurred mainly at 75–70 Ma, resulting from hydrothermal activity in the Haenam–Jindo area (82–70 Ma). This is the first time that the mineralization of precious metals in Korea has been identified during this period. 相似文献
523.
广西河池北香银多金属矿床同沉积断层的厘定及其发现意义 总被引:2,自引:1,他引:1
广西河池北香银多金属矿床已经进行了20多年的找矿勘探,基本探明了1~6号脉状矿体,但在找矿理论、矿床资源量上均未能取得实质性的突破,矿床资源也因此未能获得开发利用.通过工作,在矿区内发现了一组具有长期持续活动并控制着矿区内的沉积作用和后期构造活动特征的北西向同沉积断层,已知矿体的产状、空间分布均明显受到该同沉积断层的控制,因此该组构造具有控岩控矿特征.对比显示本矿区同沉积断层与大厂矿田的同沉积构造及其控矿特征具有相似性,在该组同沉积断层的上盘尤其与南北向、北东向构造交汇的部位是成矿的有利地段,脉状矿体的下部可能存在层状矿体.该组同沉积断层的发现开拓了北香地区找矿思路,为今后找矿勘探指明了方向. 相似文献
524.
老和尚帽预查区位于桐柏地区围山城金银成矿带以南,老湾金矿带以北,圈有大量1∶ 1万土壤地球化学衬值异常.在大调查桐柏地区银多金属调查评价项目中,以桐柏地区已探明银资源储量的8个矿床、矿点形成的银(衬值)异常为模型单元,采用矿床模型法,建立预测模型;然后对老和尚帽预查区40个预测单元(衬值综合异常)进行资源定量预测与靶区定位预测,确定了8个找矿靶区.经对确定的靶区进行初步查证,发现了矿体和矿化体,取得了一定找矿效果. 相似文献
525.
526.
枪口南银多金属矿床地处东昆仑多金属成矿带东段,枪口—哈龙休玛海西-燕山期铁、银、铅、锌、铜、金、钼成矿亚带部分,成矿地质条件优越。枪口南银多金属矿区目前已圈定9条矿化带,21个矿体,主要矿种有金、银、铜、铅、锌、钼等,矿石类型主要为构造热液(脉)型铜铅锌银矿石、构造蚀变岩型金矿石。枪口南矿区构造-岩浆活动强烈,印支期—燕山期构造岩浆活动为矿区成矿提供了热源、成矿物质,区内NE向断裂控制区内金、铜、铅锌等矿体的产出,NW向断裂组控制着区内金、银矿(化)体。NW向断裂组,是区内重要控矿构造;区内中部发现的Ⅳ号含矿斑岩体,具有斑岩型矿床蚀变特征,显示其具有斑岩成矿条件。枪口南银多金属矿床成因有构造热液(脉)型、构造蚀变岩型和斑岩型。 相似文献
527.
莫河下拉银多金属矿床是青海省东昆仑成矿带上近些年新发现的矿床。笔者对矿区平硐口花岗斑岩进行了LA-ICP-MS锆石U--Pb测年和岩石地球化学特征研究,以期揭示岩体的成岩时代、岩浆源区和形成的构造背景。锆石测年结果显示岩体形成于古生代晚泥盆世(371.6±2.9Ma)。元素地球化学特征表现为高硅、高碱、富铁铝、相对富钾和贫钙镁的特征;微量元素表现为明显富集Rb、Th、La、Ce、Nd、Zr、Sm和Gd等元素,强烈亏损Ba、Sr、P、Ti等元素、相对亏损Nb和Ta的特征;稀土元素表现为轻稀土元素(LREE)明显富集和Eu的强烈负异常。综合研究认为,矿区平硐口花岗斑岩的成因类型为A2型花岗岩,形成物质来源主要为部分熔融的长英质地壳,形成的大地构造背景为晚泥盆世万宝沟大洋玄武岩高原和苦海古陆拼贴到柴达木地块南缘后的后碰撞伸展环境。 相似文献
528.
Several techniques are available to examine the isotopic composition of historic lake waters, providing data that can subsequently
be used to examine environmental changes. A recently-developed technique is the stable oxygen isotope analysis of subfossil
chironomid (Diptera: Chironomidae) head capsules (mostly chitin) preserved in lake sediments. This technique involves a high
Temperature Conversion Elemental Analyzer (TC/EA), which has been a relatively recent addition to the suite of online peripherals
for analyzing the stable isotopic composition of organic samples. The highly precise and accurate 18O/16O and D/H measurements obtainable using the TC/EA with samples in the microgram range make this instrumentation suitable for
studying geochemical and biological processes. Preparation of organic samples for isotopic analysis typically requires first
weighing each sample into silver/tin capsules. These capsules can introduce oxygen and hydrogen contamination (a “blank effect”),
which is especially problematic for analysis of small organic samples (e.g. less than 100 μg). Here we tested tin and silver
capsules from two manufacturers and a range of sizes to assess contamination to small organic samples on the TC/EA. We also
assessed how a method for cleaning silver capsules affected our analysis of commercial chitin. In general, capsules made of
silver have less detectible oxygen than those made of tin, and capsules from the two manufacturers varied in their detectible
oxygen. There was no detectable H contamination from silver capsules. In addition to our empirical findings, we present a
model demonstrating the influence that contaminant oxygen can have on the δ18O of small organic samples. Sample mass becomes an important issue for such analyses. In light of our findings, we recommend
a minimum sample mass ≥50 μg (approximately 120 whole chironomid head capsules) on a TC/EA-IRMS (Deltaplus XP system). Finally, we present a detailed protocol for preparing and transferring chironomid head capsules into silver capsules
that minimizes the influence of contaminant oxygen. This protocol provides the paleo-community with another potential method
for reconstructing paleoenvironments. 相似文献
529.
夏塞银多金属矿床中硫化物和硫盐系列矿物特征及其意义 总被引:4,自引:1,他引:3
夏塞矿主档是大型的热液脉型银多金属矿床,通过对大量矿石光(薄)片观察和电子探针分析表明,除主要(方铅矿、富铁闪锌矿)和次要(黄铁矿、毒砂、磁黄铁矿、黄铜矿等)硫化物外,硫盐毓硫物十分发育,主要有Cu-Sb-Ag硫盐(黝铜矿、含银黝铜矿和银黝铜矿)、Sb-Ag硫盐(深红银矿、辉锑银矿)、Pb-Sb硫盐(脆硫锑铅矿、硫锑铅矿)和Bi-Pb硫盐(斜方辉饿铅矿)。此外,尚有少(微)量黄锡矿、锡石、自然饿和银金矿等。银的硫盐硫物和硫化物(辉银矿)乃是获得银的主要工业矿物,这些硫盐毓矿物常与硫化物伴生,多沿方铅矿、富铁闪锌矿、黄铁矿等的解理、裂隙或粒间产出,这些研究结果不仅有助于了解矿化作用过程,而且为矿床评价,组分综合利用和选冶提供重要依据。 相似文献
530.