全文获取类型
收费全文 | 48318篇 |
免费 | 936篇 |
国内免费 | 458篇 |
专业分类
测绘学 | 1266篇 |
大气科学 | 3388篇 |
地球物理 | 10041篇 |
地质学 | 17414篇 |
海洋学 | 3958篇 |
天文学 | 11053篇 |
综合类 | 204篇 |
自然地理 | 2388篇 |
出版年
2022年 | 319篇 |
2021年 | 516篇 |
2020年 | 562篇 |
2019年 | 564篇 |
2018年 | 1306篇 |
2017年 | 1194篇 |
2016年 | 1510篇 |
2015年 | 856篇 |
2014年 | 1502篇 |
2013年 | 2563篇 |
2012年 | 1556篇 |
2011年 | 1968篇 |
2010年 | 1780篇 |
2009年 | 2416篇 |
2008年 | 1982篇 |
2007年 | 1959篇 |
2006年 | 1821篇 |
2005年 | 1375篇 |
2004年 | 1339篇 |
2003年 | 1240篇 |
2002年 | 1181篇 |
2001年 | 1080篇 |
2000年 | 977篇 |
1999年 | 849篇 |
1998年 | 874篇 |
1997年 | 822篇 |
1996年 | 675篇 |
1995年 | 735篇 |
1994年 | 671篇 |
1993年 | 568篇 |
1992年 | 519篇 |
1991年 | 527篇 |
1990年 | 591篇 |
1989年 | 498篇 |
1988年 | 467篇 |
1987年 | 595篇 |
1986年 | 497篇 |
1985年 | 625篇 |
1984年 | 710篇 |
1983年 | 680篇 |
1982年 | 597篇 |
1981年 | 616篇 |
1980年 | 526篇 |
1979年 | 493篇 |
1978年 | 495篇 |
1977年 | 451篇 |
1976年 | 430篇 |
1975年 | 445篇 |
1974年 | 418篇 |
1973年 | 459篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
1.
Geomagnetism and Aeronomy - Additional horizontal traces of ground reflections were observed in a studied series of high-latitude, Kp sounding ionograms from the Interkosmos-19 satellite. The... 相似文献
2.
Motovilov Yu. G. Golosov S. D. Datsenko Yu. S. Zverev I. S. Puklakov V. V. Fashchevskaya T. B. 《Water Resources》2020,47(5):751-762
Water Resources - An Information–Modeling Complex has been developed for the information support of managerial decision making in the field of rational use, protection, and restoration of... 相似文献
3.
Natural Resources Research - Ecosystems and their services are essential to human well-being, but mining activities often cause adverse impacts on these services. Although impact of mining... 相似文献
4.
Natural Resources Research - Sand failure and production occurs when the formation stress exceeds the strength of the formation, which is derived majorly from the natural material that cements the... 相似文献
5.
Natural Resources Research - In the present study, ground subsidence in the Aliabad plain (central Iran) was investigated using differential synthetic aperture radar interferometry. The data used... 相似文献
6.
Ali Moamen Abdelmaksoud Ahmed Essa M. A. Abdelhady A. Darwish M. 《Natural Resources Research》2020,29(4):2575-2597
Natural Resources Research - Two main reservoirs are producing in Komombo Basin: the first one belongs to the C Member of the Six Hills Formation, and the second belongs to the Albian/Cenomanian... 相似文献
7.
Structure-specific selection of earthquake ground motions for the reliable design and assessment of structures 总被引:1,自引:1,他引:0
A decision support process is presented to accommodate selecting and scaling of earthquake motions as required for the time domain analysis of structures. Code-compatible suites of seismic motions are provided being, at the same time, prequalified through a multi-criterion approach to induce response parameters with reduced variability. The latter is imperative to increase the reliability of the average response values, normally required for the code-prescribed design verification of structures. Structural attributes like the dynamic characteristics as well as criteria related to variability of seismic motions and their compliance with a target spectrum are quantified through a newly introduced index, δ sv–sc , which aims to prioritize motions suites for response history analysis. To demonstrate the applicability of the procedure presented, the structural model of a multi-story building was subjected to numerous suites of motions that were highly ranked according to both the proposed approach (δ sv–sc ) and the conventional one (δ conv ), that is commonly used for earthquake records selection and scaling. The findings from numerous linear response history analyses reveal the superiority of the proposed multi-criterion approach, as it extensively reduces the intra-suite structural response variability and consequently, increases the reliability of the design values. The relation between the target reliability in assessing structural response and the size of the suite of motions selected was also investigated, further demonstrating the efficiency of the proposed selection procedure to achieve higher response reliability levels with smaller samples of ground motion. 相似文献
8.
Laurentiu Danciu Karin Şeşetyan Mine Demircioglu Levent Gülen Mehdi Zare Roberto Basili Ata Elias Shota Adamia Nino Tsereteli Hilal Yalçın Murat Utkucu Muhammad Asif Khan Mohammad Sayab Khaled Hessami Andrea N. Rovida Massimiliano Stucchi Jean-Pierre Burg Arkady Karakhanian Hektor Babayan Mher Avanesyan Tahir Mammadli Mahmood Al-Qaryouti Doğan Kalafat Otar Varazanashvili Mustafa Erdik Domenico Giardini 《Bulletin of Earthquake Engineering》2018,16(8):3465-3496
9.
S. Akkar T. Azak T. Çan U. Çeken M. B. Demircioğlu Tümsa T. Y. Duman M. Erdik S. Ergintav F. T. Kadirioğlu D. Kalafat Ö. Kale R. F. Kartal K. Kekovalı T. Kılıç S. Özalp S. Altuncu Poyraz K. Şeşetyan S. Tekin A. Yakut M. T. Yılmaz M. S. Yücemen Ö. Zülfikar 《Bulletin of Earthquake Engineering》2018,16(8):3197-3228
A review on the historical evolution of seismic hazard maps in Turkey is followed by summarizing the important aspects of the updated national probabilistic seismic hazard maps. Comparisons with the predecessor probabilistic seismic hazard maps as well as the implications on the national design codes conclude the paper. 相似文献
10.
Naveed Ahmad Asif Shahzad Qaisar Ali Muhammad Rizwan Akhtar Naeem Khan 《Bulletin of Earthquake Engineering》2018,16(10):4675-4703
Fragility functions are derived for low-rise code compliant & non-compliant special moment resisting frames (SMRFs). Non-compliant SMRFs those built in low strength concrete and lacking confining ties in joint panel zones, commonly found in developing countries. Shake table tests were performed on single-storey and two-storey 1:3 reduced scale representative frames to understand the damage mechanism and develop deformation-based damage scale. The non-compliant SMRF experienced column flexure cracking, longitudinal bar-slip in beam and observed with cover concrete spalling from the joint panels. The code compliant SMRF experienced flexure cracks in beam/column, and experienced joint cracking under extreme shaking. Numerical modeling technique is developed for inelastic modeling of reinforced concrete frame with beam bar-slip and joint damageability using SeismoStruct. Natural accelerograms were used to analyze the considered frames through incremental dynamic analyses in SeismoStruct. A probabilistic based approach was used to derive fragility functions for the considered frames. An example case study is presented for damageability evaluation of structures for earthquakes of various return periods (43, 72, 475, 2475 years). 相似文献