全文获取类型
收费全文 | 234篇 |
免费 | 31篇 |
国内免费 | 60篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 5篇 |
地球物理 | 63篇 |
地质学 | 210篇 |
海洋学 | 23篇 |
天文学 | 1篇 |
综合类 | 10篇 |
自然地理 | 6篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 21篇 |
2013年 | 13篇 |
2012年 | 9篇 |
2011年 | 19篇 |
2010年 | 11篇 |
2009年 | 12篇 |
2008年 | 23篇 |
2007年 | 15篇 |
2006年 | 20篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 12篇 |
2002年 | 15篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 14篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有325条查询结果,搜索用时 15 毫秒
51.
火山玻璃风化层的透射电镜研究 总被引:2,自引:0,他引:2
利用透射电镜(TEM)和X射线能谱(EDX)研究了长白山天池火山1000年和4000年前两次大喷发产生的火山玻璃风化层特征.TEM分析显示,4000年前大喷发浮岩中的火山玻璃风化层平均厚度3.7 mm,1000年前大喷发浮岩中的火山玻璃风化层平均厚度为1.0 mm.EDX分析显示,两次大喷发浮岩中的火山玻璃风化层化学组成与火山玻璃相比富Al、Fe,而si减少.火山玻璃风化层富Al发生在Al的浓度较高的中到弱酸溶液中(pH=5~6),火山玻璃表面形成含有少量的非晶质的Al、Si、Fe物质,这些非品质的次生物质是火山玻璃风化早期阶段形成的.天池火山喷发物中火山玻璃的微观特征的差异可能与火山喷发年代和喷发后的环境有关,研究天池火山不同期次喷发物中火山玻璃的微观特征具有一定的理论和实际应用价值. 相似文献
52.
“新型玻璃”是最近软玉批发市场上出现频繁的一种冒仿软玉的产品,其特点是外观很像软玉,而且其红外图谱谱形极像软玉的,个别峰位基本吻合,这给软玉的快速鉴定带来了一定的迷惑性和风险。选取一批典型的“新型玻璃”进行常规宝石学测试和红外光谱测试等一系列宝石学研究。测试结果表明,虽然“新型玻璃”的红外图谱谱形极像软玉的,但是两者之间的性质还是有着明显的差别,依据现行国家标准,其鉴定名称可直接命名为“玻璃”;同时,对“新型玻璃”的快速鉴定提出了一些参考建议。 相似文献
53.
Kathryn A. Matthews Michael T. Murrell Steven J. Goldstein Andrew J. Nunn Deborah E. Norman 《Geostandards and Geoanalytical Research》2011,35(2):227-234
Here we report uranium and thorium isotopic ratios and elemental concentrations measured in solid reference materials from the USGS (BHVO‐2G, BCR‐2G, NKT‐1G), as well as those from the MPI‐DING series (T1‐G, ATHO‐G). Specifically created for microanalysis, these naturally‐sourced glasses were fused from rock powders. They cover a range of compositions, elemental concentrations and expected isotopic ratios. The U‐Th isotopic ratios of two powdered source materials (BCR‐2, BHVO‐2) were also characterised. These new measurements via multi‐collector thermal ionisation mass spectrometry and multi‐collector inductively coupled plasma‐mass spectrometry can now be used to assess the relative performance of techniques and facilitate comparison of U‐Th data amongst laboratories in the geoscience community for in situ and bulk analyses. 相似文献
54.
Pits in ocean basalt glass are often attributed to the activity of microorganisms, however, neither the mechanism of formation of pits in glass nor the involvement of microorganisms have been confirmed by experimentation. Experimental abiotic corrosion of basalt glass with 1% hydrofluoric acid (HF), a proxy for more slowly acting organic acids, produces pits that are similar in size, shape, and distribution to pits found in basalt glass collected from the ocean floor and basalt glass incubated with microorganisms. This pit formation by HF etching was demonstrated by comparing secondary electron images taken before and after the acid treatment. The formation of pits by abiotic corrosion of basalt glass is an alternate hypothesis for the origin of these features, and the interpretation of these features as biomarkers may require a resolution of these alternative hypotheses. 相似文献
55.
万红 《矿物岩石地球化学通报》1999,(4)
对红宝石的天然、合成、优化处理成因已有许多研究,其中有不少争议[1]。争议的焦点在于对其内含物(包裹体)的认识。因此,在鉴定工作中思路要宽,对内含物的一切可能成因要作全方位推断,然后一一甄别。1 测试样品及其一般宝石学特征1-1 测试样品本文测试样品为一条红宝石伴钻石手链,来自于广州市对一家有信誉的国营大公司的市场抽查。样品重7-54g,由10粒规格为5-1×4-2mm的椭圆形刻面红宝石及18粒圆形钻石组成,工艺精美,商家称为“镶嵌红宝石手链”。1-2 一般宝石学特征10粒红宝石颜色统一,为较均… 相似文献
56.
KoIKEDA DangFENG AkiraMIKUNI 《地学前缘》2005,12(1):206-213
概要介绍了一种无机聚合物———地质聚合物。首先对地质聚合物材料的制备过程作了介绍。根据原料的不同,地质聚合物材料的制备可以有两种途径:一种是以偏高岭石为基础原料,一种是以粉煤灰为主要原料。通常以硅酸钠水溶液作为单体硅源,氢氧化钠溶液作为碱激发剂以提高原料的溶出性。对某些在常温和低于100 ℃下制备的独石材料作了介绍。对煅烧高岭石,叶蜡石,粉煤灰和钢渣的溶出特性作了阐述。应用SEM EDX,对以粉煤灰为原料的地质聚合物材料的化学组成作了分析。最后对地质聚合物材料的经济性以及在环境保护等领域的应用前景,特别是在减少二氧化碳排放与废弃物处理方面的意义作了介绍。 相似文献
57.
58.
The precipitation/replacement of Ca‐phosphate is a complex process that commonly takes place during the early diagenesis in marine sediments. The unusual occurrence of shallow marine, early diagenetic phosphatic deposits associated with glassy tuffs in the Neogene Gaiman Formation, in the Chubut Province, Patagonia, Argentina, constitutes a good case example for the study of replacement and precipitation of Ca‐phosphate on an unstable substrate. Isocon diagrams illustrate that chemical changes during glass diagenesis include gains in loss on ignition and Ca, and losses of K. These changes are the result of glass hydration during sea water–glass interaction, together with adsorption and diffusion of ions into the bulk shard; combined, these represent an incipient process of volcanic glass replacement by Ca‐phosphate. Subsequent early diagenetic P enrichment in the pore solutions led to phosphate precipitation, associated with pitting on the glass shards and pumice. The associated development of a reactive surface promoted the incorporation of P and Ca into their margins. Lastly, precipitation of calcium phosphate filled the vesicles and other open cavities, inhibiting further glass dissolution. The high porosity and reactivity of the volcanic glass provided an appropriate substrate for phosphate precipitation, leading to the development of authigenic apatite concretions in the volcanic‐glass bearing strata of the Gaiman Formation. This research is of significance for those concerned with marine phosphatic deposits and sheds light on the processes of early diagenetic phosphate precipitation by replacement of an atypical, unstable substrate like hydrated volcanic glass. 相似文献
59.
The 1996 Eruption of Karymsky Volcano, Kamchatka: Historical Record of Basaltic Replenishment of an Andesite Reservoir 总被引:4,自引:0,他引:4
The simultaneous eruption in 1996 of andesite from Karymskyvolcano and of basalt from the Academy Nauk vent 6 km away appearsto provide a case of mafic recharge of an andesite reservoirfor which the time of recharge is exactly known and direct samplesof the recharging magma are available. The explosive phreato-magmaticeruption of basalt was terminated in less than 24 h, whereasandesite erupted continuously during the following 4 years.Detailed petrological study of volcanic ash, bombs and lavasof Karymsky andesite erupted during the period 19961999provides evidence for basaltic replenishment at the beginningof the eruptive cycle, as well as a record of compositionalvariations within the Karymsky magma reservoir induced by basalticrecharge. Shortly after the beginning of the eruption the compositionof the matrix glass of the Karymsky tephra became more maficand then, within 2 months, gradually returned to its originalstate and remained almost constant for the following 3 years.Further evidence for basaltic replenishment is provided by thepresence of xenocrysts of basaltic origin in the andesite ofKarymsky. A conspicuous portion of the plagioclase phenocrystsin the Karymsky andesite has calcic cores, with compositionsand textures resembling those of plagioclases in the AcademyNauk basalt. Similarly, the earlier portion of the andesiteof the eruption sequence contains rare olivines, which occuras resorbed cores in pyroxenes. The composition of the olivinematches that of olivines in the Academy Nauk basalt. The sequenceof events appears to be: (1) injection of basaltic magma intothe Karymsky chamber with immediate, compensating expulsionof pre-existing chamber magma from the Karymsky central vent;(2) direct mixing of basaltic and andesitic magmas with dispersalof phenocrysts associated with the basalt throughout the andesiteso that newly mixed magma appeared at the vent within 2 months;(3) re-establishment of thermal and chemical equilibrium withinthe reservoir involving crystallization in the new hybrid liquid,which returned the melt composition to normal,formed rims on inherited calcic plagioclase, and caused theresorption of dispersed olivine xenocrysts. Taken together,these findings indicate that the Karymsky magma reservoir wasrecharged by basalt at the onset of the 1996 eruptive cycle.The rapidity and thoroughness of mixing of the basalt with thepre-existing andesite probably reflects the modest contrastin temperature, viscosity, and density between the two magmas. KEY WORDS: Karymsky; Kamchatka; magma mixing; andesite; volcanic glass; plagioclase 相似文献
60.
在全球矿产勘查日益萎缩的今天,人们极为重视发展新一代大型矿床的勘探技术。澳大利亚最近开展了一项雄心勃勃的计划,即玻璃地球计划,目的是研制三维可视化和地质模拟等技术,使大陆表层一千米“像玻璃一样透明”。该计划以信息技术为核心,注重技术之间的综合。从中得到的启示是,应以提高精度为出发点,加强矿产勘查技术综合示范工作;以信息技术为核心,大力发展三维可视化技术和模拟技术;注重多部门的协作,发挥社会主义集中力量办大事的优越性。 相似文献