全文获取类型
收费全文 | 97篇 |
免费 | 27篇 |
国内免费 | 67篇 |
专业分类
地球物理 | 6篇 |
地质学 | 168篇 |
海洋学 | 1篇 |
综合类 | 3篇 |
自然地理 | 13篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 13篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 9篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 9篇 |
2008年 | 10篇 |
2007年 | 4篇 |
2006年 | 8篇 |
2005年 | 12篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有191条查询结果,搜索用时 15 毫秒
61.
深圳不同类型农民工聚居区的社会融合及影响因素 总被引:1,自引:1,他引:0
选取深圳罗芳村、共乐村、清湖村分别作为无依托缘聚型农民工聚居区(增长型)、半依托混居型(稳定型)、完全依托混居型(减少型)代表,对其社会融合的现状及影响因素进行了探讨,得出以下研究发现:① 整体而言,社会融合度由高至低分别为无依托缘聚型、半依托混居型、完全依托混居型聚居区。② 不同维度社会融合方面,无依托缘聚型在社区融合、社交融合及心理融合维度上最高;半依托混居型在社区融合、文化融合及经济融合维度上较高;完全依托混居型在社区融合和经济融合维度上最低。③ 社会融合的影响因素主要有社区支持度、职业技能、在深家庭规模、在深居住时间和年龄。就不同维度而言,社区融合、经济融合、社交融合、文化融合和心理融合最重要的影响因素分别是社区支持度、职业技能、职业技能、性别、社区支持度。④ 从不同类型聚居区的影响因素来看,无依托缘聚型主要受到婚姻、社区支持度、社区功能和年龄(负)的影响;半依托混居型主要受到职业技能、社区支持度和性别的影响;完全依托混居型则主要受到社区支持度和在深居住时间的影响。 相似文献
62.
63.
XIAO Yuanfu SUN Yan LU Yan WEN Chunqi WANG JiangzhenDepartment of Geology Chengdu Institute of Technology Shilidian Chengdu Sichuan Zhu Xiling 《《地质学报》英文版》1998,72(3):308-313
Zinccopperite (tentatively named) is a rare native alloy mineral discovered in quartz monzonite-porphyry in the Xifanping area, Yanyuan County, Sichuan Province. It is a new variety of zinc-copper alloy mineral found for the first time in the porphyry-copper deposit in China. Its intergrown minerals are K-feldspar (mainly perthite), albite-oligoclase, quartz and biotite; and the associated minerals include pyrite and chalcopyrite. It is characterized by a golden reflection colour, being isotropic (isometric), with the grain size ranging from 10 to 50 μm, microhardness VHN10= 190 kg/mm2, and reflectance RVis= 67.97%. Electron microprobe (Model JXA-733) analysis shows Cu = 59.15%-62.55% and Zn= 36.32%-39.85%. The crystallochemical formula is Cu6.27-7.0Zn4.0, simplified as Cu7Zn4. 相似文献
64.
《International Geology Review》2012,54(7):795-820
ABSTRACTThe magmatic generation for the Late Triassic–Early Jurassic (~215–200 Ma) and Early Cretaceous–Late Cretaceous (~108–79 Ma) post-collisional granites in the Sanjiang Tethys orogeny remain enigmatic. The Xiuwacu complex, located in the southern Yidun Terrane, consists of biotite granite with a weight mean 206Pb/238U age of 199.8 ± 2.5 Ma, aplite granite of 108.2 ± 2.3 Ma, monzogranite porphyry of 80.8 ± 1.0 Ma, and diorite enclaves of 79.2 ± 0.9 Ma and 77.9 ± 0.8 Ma. The Late Triassic biotite granites show I-type granite affinities, with high SiO2 contents, high Mg# values, high zircon δ18O values, and negative whole-rock ?Nd(t) values, indicating a predominant ancient crustal source with the input of juvenile materials. Their fractionated REE patterns and concave-upward middle-to-heavy REE patterns require garnet-bearing amphibolite as the melt source. The Cretaceous highly fractionated aplite granites and monzogranite porphyries have relatively high SiO2 contents, high (Na2O + K2O)/CaO ratios, high zircon δ18O values, and enriched whole-rock Sr–Nd isotopic signatures, suggesting that their parent magmas were likely originated from the ancient middle- to lower crust. Their significant negative Eu anomalies and obvious depletions in Nb, Sr, and Ti demonstrate that the Cretaceous granitic magmas had experienced more fractionation than the Late Triassic felsic magmas. The Late Cretaceous diorite enclaves show low SiO2 contents, high Mg# values, and high zircon δ18O values, suggesting that they were probably derived from the partial melting of subcontinental lithospheric mantle enriched by the Late Triassic subduction. The Late Triassic–Early Jurassic and Early Cretaceous–Late Cretaceous magmatism witnessed the post-collisional setting and intraplate extensional setting in response to the slab break-off and lithospheric-scale transtensional faulting, respectively. The partial melting of subduction-modified lithospheric mantle or/and residual sulphide cumulates within the lower crust during the origination of Late Cretaceous magmas could have provided metals for the formation of Xiuwacu deposit. 相似文献
65.
Evidence of Magma Mixing in the 'Daly Gap' of Alkaline Suites: a Case Study from the Enclaves of Pantelleria (Italy) 总被引:4,自引:0,他引:4
The island of Pantelleria consists of trachytes, pantelleritesand minor mildly alkaline basalts. Rocks of intermediate composition(falling in the so-called Daly Gap) such as mugearites,benmoreites and mafic trachytes occur only in the form of enclavesin trachytes and pantellerites inside the main caldera of theisland (Caldera Cinque Denti), which collapsedduring the Green Tuff ignimbrite eruption at 50ka. The enclaves include volcanic, subvolcanic and intrusiverock types. The enclaves in host trachyte contain traces ofglass; devitrified glass occurs within enclaves in host pantellerites.Minerals in the enclaves show regular compositional variationswith whole-rock silica content. Glass present in the medium-grainedsamples is interpreted to be the result of incipient melting.The major and trace element compositions of the enclaves showregular and linear variations between an evolved mafic magma(hawaiite) and a felsic end-member similar to the GreenTuff trachyte. Fractional crystallization modelling ofcompatible and incompatible trace elements (V, Ni, Zr, La, Sm,Lu, Nb, Y, Th) does not reproduce the observed trends. Rocksof intermediate composition within the Daly Gapcan be explained only by magma mixing between an already differentiatedmafic magma (hawaiite) and an anorthoclase-rich trachytic meltin the lower and higher parts, respectively, of a stratifiedmagmatic chamber. Medium-grained enclaves are interpreted asthe result of fragmentation of solidified mixing layers in theroof of the magma chamber during the eruption of the GreenTuff, when the collapse of the caldera took place. Diffusioncalculations suggest a residence time of <5 days for theenclaves in their host magmas. KEY WORDS: Daly Gap; enclaves; magma mixing; Pantelleria 相似文献
66.
67.
民国29~35年(1940~1946年),国民政府对川黔交界地区的插花地进行了清理拨正。清理拨正可大别为两个阶段:一是川黔两省自行清理拨正(1940~1944年),二是内政部主持下的清理拨正(1945~1946年)。清理拨正成效较为明显,不仅进行了实地会勘,而且形成了会议决议,川黔交界地区8县17乡镇的33个插花地问题... 相似文献
68.
69.
《Urban geography》2013,34(7):609-639
This case study applies the segment approach to investigate community sense of place for a small-town tourism business district (TBD). A stratified random sample of residents from Galena, Illinois (population 3,647), is analyzed to identify personal values and behaviors most closely associated with sense of place for downtown. Despite Galena's extreme orientation to tourism, natives and middle-class newcomers generally were found to be equally, and highly, involved with their TBD. Consequently, respondents claimed sentiments of "at-homeness" (or sense of place) for downtown regardless of their duration of residence. However, natives and newcomers collectively valued downtown for different reasons. One implication is that sense of place for downtown can translate into local agency-based projects and interest groups that promote or oppose the transformation of place. In turn, community cohesiveness can be threatened through the process of transforming a historic downtown into a TBD. [Key words: tourism business district (TBD), sense of place, downtown redevelopment, main street, small town.] 相似文献
70.
Mark P. Hampton 《Singapore journal of tropical geography》2010,31(2):239-253
Cross‐border tourism is often proposed by governments as an incentive for economic growth, but critics have suggested that its impacts are, in fact, overplayed. This paper presents research in the Indonesia‐Malaysia‐Singapore Growth Triangle (IMS‐GT). It examines the broad economic impacts of Singaporean cross‐border tourism on local host communities in two locations: Kukup, a traditional Malaysian fishing village in Johor, southern Peninsular Malaysia, and Bintan in Riau Islands Province in western Indonesia. The study found that cross‐border tourism generated income, employment and some local economic linkages. In Kukup clear economic benefits with increased income and employment were unevenly distributed between ethnic groups. The Bintan enclave development had some linkages to the island economy but was reliant on immigrant labour. Cross‐border ethnic ties, particularly Chinese, also played an important role in the growth of tourism in the IMS‐GT. The paper shows that cross‐border tourism can be a useful addition to more conventional forms of international tourism within national tourism planning and could lead to significant economic benefits for local communities. 相似文献