全文获取类型
收费全文 | 377篇 |
免费 | 19篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 24篇 |
地球物理 | 78篇 |
地质学 | 175篇 |
海洋学 | 14篇 |
天文学 | 67篇 |
综合类 | 5篇 |
自然地理 | 26篇 |
出版年
2023年 | 1篇 |
2022年 | 11篇 |
2021年 | 18篇 |
2020年 | 16篇 |
2019年 | 17篇 |
2018年 | 32篇 |
2017年 | 45篇 |
2016年 | 47篇 |
2015年 | 16篇 |
2014年 | 32篇 |
2013年 | 31篇 |
2012年 | 23篇 |
2011年 | 22篇 |
2010年 | 12篇 |
2009年 | 17篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 3篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有405条查询结果,搜索用时 31 毫秒
21.
Farrokhzad Farzad MotahariTabari SeyedArmin Abdolghafoorkashani Hamid Tavakoli Hamidreza 《Geotechnical and Geological Engineering》2021,39(6):4071-4091
Geotechnical and Geological Engineering - Soil nailing is an in-situ soil reinforcement technique that is used to enhance the stability of land slopes, retaining walls and excavations. This... 相似文献
22.
Zekri Hamid Cohen David R. Mokhtari Ahmad Reza Esmaeili Abbas 《Natural Resources Research》2019,28(3):849-865
Natural Resources Research - Machine learning (ML) schemes can enhance success in geochemical prospectivity mapping. This study has examined the effectiveness of several feature extraction or... 相似文献
23.
Sustainable development is a vital and challenging factor for managing urban growth smartly. This factor contains three main components, namely economic growth, ecological protection and social justice. Green Transit-Oriented Development (GTOD) is a consummate planning approach in line with those components. Implementation of GTOD in an urban area is underpinned by its quantification. Therefore, a quantitative spatial index based on several indicators related to TOD and Green urbanism concepts should be developed. In this study, Geo-spatial Information Science and hierarchical fuzzy inference system (HFIS) were employed to calculate the indicators and aggregate them, respectively. In order to showcase the feasibility of the proposed method, it was implemented in a case study area in the City of Tehran, Iran. The result of this method is an integrated spatial GTOD index, which measures the neighbourhoods’ GTOD levels. These measurements specify weaknesses and strengths of neighbourhoods’ factors. Therefore, this index helps decision-makers to plan neighbourhoods based on land use and public transit views. Additionally, the HFIS method helps decision-makers to consider criteria and indicators with their inherent uncertainties and aggregate them with much fewer rules. For evaluating the results, the developed GTOD index was assessed with municipal action planning and attraction maps. According to the outcomes of the assessment, it is concluded that the proposed method is adequately robust and efficient for smart and sustainable urban planning. 相似文献
24.
Ding-ding Du Cheng-jun Zhang Muhammad Saleem Mughal Xiao-yu Wang Dembele Blaise Jun-ping Gao Yuan Ma Xin-rong Luo 《山地科学学报》2018,15(3):532-547
The Northern Qaidam Basin is located at the northeastern part of the Qinghai-Tibetan Plateau. It contains very thick Cenozoic terrestrial clastic sediments, which records the formation of the northern Qaidam Basin due to compressional deformation during the Indo-Asian collision. In this paper, we used detrital apatite fission-track thermochronology, including 4 sandstones and 2 conglomerates samples from the Lulehe section, to reveal the Cenozoic evolution of the northern Qaidam Basin. Fission-track dating indicated the source region of the Lulehe section has experienced important cooling and uplifting in the Late Cretaceous (at ~85.1 Ma and ~65 Ma) and the Eocene (~52 Ma), respectively. The AFT age distribution on the section suggested that the provenance of Lulehe section sediments were mainly derived from the south Qilian Shan (Qilian Mountains) and Altun Shan (Altun Mountains), and two significantly provenance changes may occur at 43.4-46.1 Ma and ~37.8 Ma, respectively. The results may have strong constrains on the Cenozoic deformation and tectonic evolution of the northern Qaidam Basin and Qinghai-Tibet Plateau. 相似文献
25.
Electrostatic solitary waves and double layers (DLs) formed by the coupled ion acoustic (IA) and drift waves have been investigated in non-uniform plasma using \(q\)-nonextensive distribution function for the electrons and assuming ions to be cold \(T_{i}< T_{e}\). It is found that both compressive and rarefactive nonlinear structures (solitary waves and DLs) are possible in such a system. The steeper gradients are supportive for compressive solitary (and double layers) and destructive for rarefactive ones. The \(q\)-nonextensivity parameter \(q\) and the magnitudes of gradient scale lengths of density and temperature have significant effects on the amplitude of the double layers (and double layers) as well as on the speed of these structures. This theoretical model is general which has been applied here to the \(F\)-region ionosphere for illustration. 相似文献
26.
Linjie Chen Amin Aminaei Leonid I. Gurvits Marc Klein Wolt Hamid Reza Pourshaghaghi Yihua Yan Heino Falcke 《Experimental Astronomy》2018,45(2):231-253
In radio astronomy, the Ultra-Long Wavelengths (ULW) regime of longer than 10 m (frequencies below 30 MHz), remains the last virtually unexplored window of the celestial electromagnetic spectrum. The strength of the science case for extending radio astronomy into the ULW window is growing. However, the opaqueness of the Earth’s ionosphere makes ULW observations by ground-based facilities practically impossible. Furthermore, the ULW spectrum is full of anthropogenic radio frequency interference (RFI). The only radical solution for both problems is in placing an ULW astronomy facility in space. We present a concept of a key element of a space-borne ULW array facility, an antenna that addresses radio astronomical specifications. A tripole–type antenna and amplifier are analysed as a solution for ULW implementation. A receiver system with a low power dissipation is discussed as well. The active antenna is optimized to operate at the noise level defined by the celestial emission in the frequency band 1 ? 30 MHz. Field experiments with a prototype tripole antenna enabled estimates of the system noise temperature. They indicated that the proposed concept meets the requirements of a space-borne ULW array facility. 相似文献
27.
Abdel Hamid Bakhit 《GeoJournal》1994,34(3):253-255
The failure of some individuals and groups to command adequate food can be accounted for through the analysis of the interplay of three mechanisms, namely food availability, food affordability and food accessibility. In Khartoum, as the case is in many other state-capitals, availability of food is not a major constraint in the dynamics of the food system. Of more significance for the configuration of the space of vulnerability are the processes related to affordability and accessibility, which combine to configurate the space of vulnerability. Occupation, place of residence, ethnic belonging and, of late, political allegiance define to a large extent the location of people in this space. 相似文献
28.
29.
30.