全文获取类型
收费全文 | 2962篇 |
免费 | 267篇 |
国内免费 | 416篇 |
专业分类
测绘学 | 620篇 |
大气科学 | 203篇 |
地球物理 | 195篇 |
地质学 | 1025篇 |
海洋学 | 332篇 |
天文学 | 15篇 |
综合类 | 219篇 |
自然地理 | 1036篇 |
出版年
2024年 | 8篇 |
2023年 | 44篇 |
2022年 | 124篇 |
2021年 | 113篇 |
2020年 | 109篇 |
2019年 | 148篇 |
2018年 | 99篇 |
2017年 | 151篇 |
2016年 | 159篇 |
2015年 | 120篇 |
2014年 | 182篇 |
2013年 | 239篇 |
2012年 | 172篇 |
2011年 | 159篇 |
2010年 | 151篇 |
2009年 | 134篇 |
2008年 | 170篇 |
2007年 | 176篇 |
2006年 | 158篇 |
2005年 | 126篇 |
2004年 | 111篇 |
2003年 | 84篇 |
2002年 | 80篇 |
2001年 | 81篇 |
2000年 | 77篇 |
1999年 | 70篇 |
1998年 | 65篇 |
1997年 | 41篇 |
1996年 | 36篇 |
1995年 | 30篇 |
1994年 | 37篇 |
1993年 | 41篇 |
1992年 | 22篇 |
1991年 | 33篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有3645条查询结果,搜索用时 140 毫秒
81.
Kate Kerkin 《The Australian geographer》2004,35(2):185-192
This paper shows how a critical approach to discourse sheds light on processes of spatial re-orderings. It uses a case study of urban planning in an area of street sex work to explore the ways in which various representations of prostitution can be used to inform planning decisions. Representations of sex worker identity also expose complex spatial and social geographies and evolving processes of marginalisation and exclusion. 相似文献
82.
本文首先揭示了建设信息化城市的原因所在;在此基础上,分别对如何实现城市信息化以及如何维持信息化城市的可持续发展进行了规划,并且指出,城市规划应当兼顾两者,不可偏废。 相似文献
83.
Marcus B. Lane 《The Australian geographer》2005,36(3):283-299
This paper tracks the changing role of public participation in planning thought. In doing so, the paper shows that the role of public participation in planning is largely determined by the nature of the planning enterprise being undertaken. The definition of the planning problem, the kinds of knowledge used in planning practice, and the conceptualisation of the planning and decision-making context are the important determinants of the extent of participation offered to the public. The paper therefore contributes to thinking about how to evaluate public participation by showing that it can only be understood in terms of the decision-making context in which it is embedded. Specifically, it makes little sense to evaluate public participation in terms that are not shared by the planning model itself 相似文献
84.
85.
A metamorphic petrological study, in conjunction with recent precise geochronometric data, revealed a complex P–T–t path for high-grade gneisses in a hitherto poorly understood sector of the Mesoproterozoic Maud Belt in East Antarctica. The Maud Belt is an extensive high-grade, polydeformed, metamorphic belt, which records two significant tectono-thermal episodes, once towards the end of the Mesoproterozoic and again towards the late Neoproterozoic/Cambrian. In contrast to previous models, most of the metamorphic mineral assemblages are related to a Pan-African tectono-thermal overprint, with only very few relics of late Mesoproterozoic granulite-facies mineral assemblages (M1) left in strain-protected domains. Petrological and mineral chemical evidence indicates a clockwise P–T–t path for the Pan-African orogeny. Peak metamorphic (M2b) conditions recorded by most rocks in the area (T = 709–785 °C and P = 7.0–9.5 kbar) during the Pan-African orogeny were attained subsequent to decompression from probably eclogite-facies metamorphic conditions (M2a).The new data acquired in this study, together with recent geochronological and geochemical data, permit the development of a geodynamic model for the Maud Belt that involves volcanic arc formation during the late Mesoproterozoic followed by extension at 1100 Ma and subsequent high-grade tectono-thermal reworking once during continent–continent collision at the end of the Mesoproterozoic (M1; 1090–1030 Ma) and again during the Pan-African orogeny (M2a, M2b) between 565 and 530 Ma. Post-peak metamorphic K-metasomatism under amphibolite-facies conditions (M2c) followed and is ascribed to post-orogenic bimodal magmatism between 500 and 480 Ma. 相似文献
86.
Extensive high-grade polydeformed metamorphic provinces surroundingArchaean cratonic nuclei in the East Antarctic Shield recordtwo tectono-thermal episodes in late Mesoproterozoic and lateNeoproterozoicCambrian times. In Western Dronning MaudLand, the high-grade Mesoproterozoic Maud Belt is juxtaposedagainst the Archaean Grunehogna Province and has traditionallybeen interpreted as a Grenvillian mobile belt that was thermallyoverprinted during the Early Palaeozoic. Integration of newUPb sensitive high-resolution ion microprobe and conventionalsingle zircon and monazite age data, and ArAr data onhornblende and biotite, with thermobarometric calculations onrocks from the H.U. Sverdrupfjella, northern Maud Belt, resultedin a more complex PTt evolution than previouslyassumed. A c. 540 Ma monazite, hosted by an upper ampibolite-faciesmineral assemblage defining a regionally dominant top-to-NWshear fabric, provides strong evidence for the penetrative deformationin the area being of Pan-African age and not of Grenvillianage as previously reported. Relics of an eclogite-facies garnetomphaciteassemblage within strain-protected mafic boudins indicate thatthe peak metamorphic conditions recorded by most rocks in thearea (T = 687758°C, P = 9·411·3kbar) were attained subsequent to decompression from P >12·9 kbar. By analogy with limited UPb singlezircon age data and on circumstantial textural grounds, thisearlier eclogite-facies metamorphism is ascribed to subductionand accretion around 565 Ma. Post-peak metamorphic K-metasomatismunder amphibolite-facies conditions is ascribed to the intrusionof post-orogenic granite at c. 480 Ma. The recognition of extensivePan-African tectonism in the Maud Belt casts doubts on previousRodinia reconstructions, in which this belt takes a pivotalposition between East Antarctica, the Kalahari Craton and Laurentia.Evidence of late Mesoproterozoic high-grade metamorphism duringthe formation of the Maud Belt exists in the form of c. 1035Ma zircon overgrowths that are probably related to relics ofgranulite-facies metamorphism recorded from other parts of theMaud Belt. The polymetamorphic rocks are largely derived froma c. 1140 Ma volcanic arc and 1072 ± 10 Ma granite. KEY WORDS: Maud Belt; Pan-African orogeny; geochronology; PTt path, East Antarctica 相似文献
87.
全生育期内作物需水量的研究是农业水资源有效利用和进行合理灌溉的重要依据。基于三江平原22个气象站点2000—2015年逐日气象观测资料及中国区域地面气象要素数据集,利用国际粮农组织 (FAO)Penman-Monteith模型和分段单值平均作物系数法,分别对三江平原水稻、玉米和大豆的作物需水量进行计算,分析作物需水量年际变化特征,采用通径分析法研究作物需水量的变化成因。结果表明:(1)三江平原16 a来年均参考作物蒸散量为537.4 mm,日均为 3.5 mm,呈波动减少趋势。(2)生长季内,水稻在分蘖期需水量最大,为177.1 mm,玉米在七叶期需水量最大,为99.7 mm,大豆在结荚期需水量最大,为96.1 mm;水稻、玉米和大豆的净灌溉需水量分别为195.4 mm、130.8 mm和72.2 mm,对灌溉的依赖程度水稻>玉米>大豆。(3)由通径分析结果可知,三江平原作物需水量的主要影响因素为净辐射、气温和日照时数。 相似文献
88.
Conditions of the prograde, peak‐pressure and part of the decompressional P–T path of two Precambrian eclogites in the eastern Sveconorwegian orogen have been determined using the pseudosection approach. Cores of garnet from a Fe–Ti‐rich eclogite record a first prograde and syn‐deformational stage along a Barrovian gradient from ~670 °C and 7 kbar to 710 °C and 8.5 kbar. Garnet rims grew during further burial to 16.5–19 kbar at ~850–900 °C, along a steep dP/dT gradient. The pseudosection model of a kyanite‐bearing eclogite sample of more magnesian bulk composition confirms the peak conditions. Matrix reequilibration associated with subsequent near‐isothermal decompression and partial exhumation produced plagioclase‐bearing symplectites replacing kyanite and clinopyroxene at an estimated 850–870 °C and 10–11 kbar. The validity of the pseudosections is discussed in detail. It is shown that in pseudosection modelling the fractionation of FeO in accessory sulphides may cause a significant shift of field boundaries (here displaced by up to 1.5 kbar and 70 °C) and must not be neglected. Fast burial, exhumation and subsequent cooling are supported by the steepness of both the prograde and the decompressional P–T paths as well as the preservation of garnet growth zoning and the symplectitic reaction textures. These features are compatible with deep tectonic burial of the eclogite‐bearing continental crust as part of the underthrusting plate (Eastern Segment, continent Baltica) in a collisional setting that led to an effectively doubled crustal thickness and subsequent exhumation of the eclogites through tectonic extrusion. Our results are in accordance with regional structural and petrological relationships, which demonstrate foreland‐vergent partial exhumation of the eclogite‐bearing nappe along a basal thrust zone and support a major collisional stage at c. 1 Ga. We argue that the similarities between Sveconorwegian and Himalayan eclogite occurrences emphasize the modern style of Grenvillian‐aged tectonics. 相似文献
89.
在全面推进生态文明建设背景下,急需建立适合中国国情的国土空间开发保护制度和国土空间规划体系,这是新时期建立空间治理体系的重要任务。在国务院新一轮的机构改革背景下,空间类规划的编制职能向自然资源部集中,急需探索和建立全国国土空间规划体系的总体框架和制度环境改革的推进路径。研究表明:国家国土空间规划体系的重建取决于三个方面,一是依赖于部门的职能整合,二是国土空间规划体系的整合与重构,三是依赖于制度环境改革。因此,在机构改革逐步完成的形势下,需要从国土空间规划体系重建与制度环境改革两个路径着手,从国家、省域、市县等层面阐述了中国国土空间规划体系的重建思路,构建五级四类、上下衔接、分级管理的国土空间规划体系。从确定国土空间开发保护制度、专业人才培养、规划资质管理、推进立法等几个方面推进制度环境改革。最后从推进国土空间规划立法、审批程序前置和推进相关法律法规修改完善等方面提出具体举措,以确立国土空间规划的法定地位与统领作用。结合新时期国土空间规划编制,提出了尽快出台国土空间规划编制办法和技术规程、重新调整中国国土空间规划编制的时序安排、加强技术队伍建设等若干建议。 相似文献
90.
A hydraulic invariance‐based methodology for the implementation of storm‐water release restrictions in urban land use master plans 下载免费PDF全文
Viviana Pappalardo Alberto Campisano Francesco Martinico Carlo Modica Luca Barbarossa 《水文研究》2017,31(23):4046-4055
A hydraulic invariance (HI)‐based methodology was developed as a tool to support implementation of storm flow control measures into land use master plans (LUMPs) for urban catchments. The methodology is based on the use of simple hydrologic analysis to compare predevelopment and postdevelopment catchment flow release scenarios. Differently from previous literature examples, for which the parcel scale is usually considered for the analysis, HI was pursued assuming the LUMP areas of transformation as the basic units for assigning storm water control measures in the form of flow release restrictions. The methodology was applied to a case study catchment in the southern part of the City of Catania (Italy), for which the LUMP re‐design has been recently proposed. Simulations were run based on the use of the EPA‐Storm Water Management Model and allowed deriving flow release restrictions in order to achieve HI at the subcatchment level for design events of different return period. 相似文献