全文获取类型
收费全文 | 1408篇 |
免费 | 165篇 |
国内免费 | 172篇 |
专业分类
测绘学 | 128篇 |
大气科学 | 111篇 |
地球物理 | 251篇 |
地质学 | 463篇 |
海洋学 | 195篇 |
天文学 | 44篇 |
综合类 | 112篇 |
自然地理 | 441篇 |
出版年
2024年 | 9篇 |
2023年 | 24篇 |
2022年 | 52篇 |
2021年 | 85篇 |
2020年 | 69篇 |
2019年 | 54篇 |
2018年 | 38篇 |
2017年 | 72篇 |
2016年 | 50篇 |
2015年 | 44篇 |
2014年 | 67篇 |
2013年 | 101篇 |
2012年 | 73篇 |
2011年 | 58篇 |
2010年 | 48篇 |
2009年 | 57篇 |
2008年 | 66篇 |
2007年 | 59篇 |
2006年 | 57篇 |
2005年 | 68篇 |
2004年 | 74篇 |
2003年 | 64篇 |
2002年 | 73篇 |
2001年 | 36篇 |
2000年 | 57篇 |
1999年 | 59篇 |
1998年 | 43篇 |
1997年 | 25篇 |
1996年 | 34篇 |
1995年 | 17篇 |
1994年 | 14篇 |
1993年 | 19篇 |
1992年 | 9篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1745条查询结果,搜索用时 218 毫秒
901.
The Lower Palaeozoic sequences of the Rügen boreholes are composed of pelitic-clastic sediments which range in age from the Cambro-Ordovician boundary to the Late Ordovician. Provenance studies have been carried out on Cambro-Ordovician sandstones from the Loissin borehole and on Middle-Upper Ordovician greywackes of the Rugen 5 borehole.The Loissin sandstones were deposited as turbidites and debris flows in an unstable sedimentary basin. They form immature arkoses and subarkoses with high matrix contents. Their debris derived from a polycyclic, sedimentary cratonic provenance and from a monocyclic magmatic provenance. This is reflected in the heavy mineral spectrum, which is dominated by an anhedral, coloured zircon fraction and a euhedral, transparent zircon fraction.The Middle-Upper Ordovician Rügen greywackes derived from proximal, high energy turbidites which were transported into a deep marine basin. They form homogeneous lithic arkoses and arkosic litharenites. Their debris derived from a composite provenance with an ultramafic-mafic, ophiolitic source, an acidic magmatic source and a heterogeneous sedimentary cratonic source.Although the Loissin sandstones probably originated in an intracratonic, rift-related sedimentary basin, the debris of the Rugen greywackes is regarded as derived from a heterogeneous active continental margin. Results and interpretations of the provenance study are discussed in the light of proposed Lower Palaeozoic palaeogeographic reconstructions. 相似文献
902.
地球化学的理论体系与方法论 总被引:3,自引:1,他引:3
Yu Chongwen 《地球科学》1986,(4)
本文根据地球化学作用与时-空结构辩证统一的观点提出地球化学的理论体系与方法论,认为地球化学体系应由地球化学系统的物质、地球化学作用、地球化学过程和地球化学场等四大部分所构成,其中以地球化学系统的物质为基础,而地球化学作用居于核心地位。地球化学作用与时-空结构的统一性应该作为一切地学研究的指导思想。作者指出,必须用系统思想和系统科学研究地球化学系统,应用不可逆过程热力学中的“耗散结构”(dissipativestructures)理论研究地球化学作用与时-空结构的内在联系。 相似文献
903.
904.
Subash Chandra V. A. Rao N. S. Krishnamurthy S. Dutta Shakeel Ahmed 《Hydrogeology Journal》2006,14(6):1042-1051
An integrated study was carried out to investigate the subsurface geological conditions in a hard rock environment, with the aim of identifying zones with groundwater resource potential. The study, in Bairasagara watershed, Karnataka, India, considered geomorphology, water level, resistivity imaging, self potential, total magnetic field and susceptibility. The signatures due to lineaments have been clearly identified and their role in groundwater movement has been documented. Synthetic simulation methods were used to model the electrical response of the lineament using finite differential modeling scheme. The inverted image of the field data is compared with the synthetic image and iteration were performed on the initial model until a best match was obtained resulting on the generation of the calibrated resistivity image of the subsurface. Resistivity imaging revealed that the dykes are weathered/fractured to a depth of 6–8 m and are compact at deeper levels, and that they behave as barriers to groundwater movement, yet facilitate a good groundwater potential zone on the upgradient side. The results of magnetic surveys were utilized in differentiating granites and dolerite dykes with an insignificant resistivity contrast. Geomorphological expression alone cannot reveal the groundwater potential associated with a lineament. However, characterizing the nature of the feature at depth with integrated geophysical methods provides essential information for assessing that potential.The online version of the original article can be found at 相似文献
905.
我国深层地热资源的认识与勘探方法建议 总被引:2,自引:0,他引:2
我国丰富的深层地热资源储量为加快深层勘探提供了基础,尽管目前深层地热勘探许与开发还存在着很多难度,但深层地热分布规律认识和回灌技术的日见成熟使加快深层地热勘探步伐成为可能。根据上述认识,提出了加强地热地质基础理论研究与勘探开发技术研究的目的与方法,以及进行地热资源勘查的地质调查、地球物理勘探、地热钻井工程及井试等技术方法。 相似文献
906.
The paper analyses a list of thirty-four Poles, listeners to the mineralogy lectures given by R.-J. Haüy at MNHN in Paris. These students played an important role in the history of Polish Earth Sciences (S. Staszic and F. Drzewiński), but also in other scientific fields (J. Markowski, I. Ab?amowicz, F. Drzewiński, M.A. Paw?owicz, J.K. Skrodzki, E.K. Nowicki), and even in political and cultural life of Poland (A. Downarowicz, J. Weyssenhoff, S. Plater, J. Bieliński, F. Potocki). This paper presents later relations between R.-J. Haüy and his Polish students. A possibility of the Poles' attendance to mineralogy lectures given at other Parisian scientific institutions, like the ‘École des mines’ and the ‘College de France’, is also discussed. To cite this article: R. Tarkowski, P. Daszkiewicz, C. R. Geoscience 338 (2006). 相似文献
907.
908.
909.
Good, bad or 'necessary evil'? Reinterpreting the colonial burning experiments in the savanna landscapes of West Africa 总被引:2,自引:0,他引:2
A simple ecological model underlies contemporary fire policy in many West African countries. The model holds that the timing (or seasonality) of annual savanna fires is a principal determinant of vegetation cover. The model's origin can be traced to the ideas held by influential colonial scientists who viewed anthropogenic fire as a prime force of regional environmental degradation. The main evidence in support of the model derives from the results of a series of long-term burning experiments carried out during last century. The experimental results have been repeatedly mapped onto fire policy often taking the form of a three-tiered model in which fire exclusion is considered the ultimate management objective, late dry-season fire is discouraged and early dry-season fire is allowed but only under specific, often state-controlled circumstances. This paper provides a critique of contemporary fire policy in the region and the fire ecology model on which it is based. Through an analysis of burn scars for the 2002–3 fire season generated from ETM+ imagery, the study documents the spatiotemporal pattern of burning for an area in southern Mali. It argues that current policy, which is informed by an a-spatial model, cannot adequately account for the critical pattern of burning that is characteristic of the region. A reinterpretation of the burning experiments is presented in light of four factors: empirical data; recent developments in patch-mosaic theory; historical evidence on the effects of fire suppression; and data on indigenous burning strategies, all of which suggest a need to reconsider current fire policy. 相似文献
910.
Garth A. Myers 《Singapore journal of tropical geography》2006,27(3):289-308
This paper uses a case study of Lusaka, Zambia, to interrogate several aspects of the literature on postcolonial geography. I deploy two concepts from African postcolonial studies – the idea of exclusionary democracy and the concept of the domestication of difference – and assess the continuity in their applicability to Lusaka. More specifically, I examine the contention that both the political and the planning dynamics of the last years of colonialism are foundational to state–society relationships in contemporary Lusaka. Distinguishing two spheres for in-depth discussion – urban government and housing policy – I concentrate on the final years of colonialism, moving through to the contemporary setting, to examine if the roots still show for the processes creating exclusionary democracy and domesticating difference. I also examine the ambivalent and incomplete character of those processes. I close with an assessment of the broader meaning inherent in understanding Lusaka in postcolonial terms. 相似文献