全文获取类型
收费全文 | 73898篇 |
免费 | 1526篇 |
国内免费 | 619篇 |
专业分类
测绘学 | 1806篇 |
大气科学 | 5577篇 |
地球物理 | 15094篇 |
地质学 | 24983篇 |
海洋学 | 6901篇 |
天文学 | 16329篇 |
综合类 | 192篇 |
自然地理 | 5161篇 |
出版年
2022年 | 947篇 |
2021年 | 1425篇 |
2020年 | 1486篇 |
2019年 | 1580篇 |
2018年 | 1366篇 |
2017年 | 1177篇 |
2016年 | 1443篇 |
2015年 | 1101篇 |
2014年 | 1454篇 |
2013年 | 3342篇 |
2012年 | 1566篇 |
2011年 | 2476篇 |
2010年 | 2129篇 |
2009年 | 3156篇 |
2008年 | 2764篇 |
2007年 | 2511篇 |
2006年 | 2570篇 |
2005年 | 2220篇 |
2004年 | 2471篇 |
2003年 | 2339篇 |
2002年 | 2268篇 |
2001年 | 2014篇 |
2000年 | 1797篇 |
1999年 | 1548篇 |
1998年 | 1588篇 |
1997年 | 1570篇 |
1996年 | 1195篇 |
1995年 | 1234篇 |
1994年 | 1127篇 |
1993年 | 1010篇 |
1992年 | 979篇 |
1991年 | 848篇 |
1990年 | 1031篇 |
1989年 | 885篇 |
1988年 | 796篇 |
1987年 | 943篇 |
1986年 | 883篇 |
1985年 | 1038篇 |
1984年 | 1217篇 |
1983年 | 1169篇 |
1982年 | 1020篇 |
1981年 | 1004篇 |
1980年 | 849篇 |
1979年 | 824篇 |
1978年 | 879篇 |
1977年 | 802篇 |
1976年 | 747篇 |
1975年 | 703篇 |
1974年 | 757篇 |
1973年 | 747篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
21.
Tumbure Akinson Bretherton Mike R. Bishop Peter Hedley Mike J. 《Natural Resources Research》2020,29(3):1561-1570
Natural Resources Research - The physical and chemical characteristics of mined phosphate rock will vary temporally as the location and nature of the ore body changes and as the type of equipment... 相似文献
22.
Xiang Jie Xiao Keyan Carranza Emmanuel John M. Chen Jianping Li Shi 《Natural Resources Research》2020,29(1):395-414
Natural Resources Research - In the past few decades, a variety of data-driven predictive modeling techniques has led to a dramatic advancement in mineral prospectivity mapping (MPM). The random... 相似文献
23.
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
24.
Yu Xinran Ahmadinia Masoud Shariatipour Seyed M. Lawton Don Osadetz Kirk Saeedfar Amin 《Natural Resources Research》2020,29(4):2735-2752
Natural Resources Research - Carbon capture and storage is part of Canada’s climate change action plan to reduce greenhouse gas emissions. The Containment and Monitoring Institute Field... 相似文献
25.
Natural Resources Research - Borehole-controlled one-dimensional geo-electric data were integrated with water samples obtained from boreholes drilled near the vertical electrical sounding at 12... 相似文献
26.
Structural irregularity in new buildings is sometimes desired for aesthetic reasons. Often it is unavoidable due to different uses in adjacent spaces within the building. The seismic behaviour of irregular structures is harder to predict than that of regular buildings. More comprehensive analysis techniques are often required to achieve adequate accuracy. Designing irregular structures poses additional challenges as the structural characteristics are unknown. There is a lack of practical design methods that reliably produce economic and seismically robust design solutions for highly irregular RC structures. This paper presents an extension of the Effective Modal Design (EMD) method from asymmetric-plan RC wall buildings to vertically setback asymmetric-plan RC wall buildings. EMD is a generalization of the Direct Displacement-Based Design method for highly irregular ductile uncoupled RC wall structures. EMD reverse engineers a multi-degree of freedom Equivalent Linear System to produce the most economic design solution that achieves the target performance levels. The utility of EMD is verified for a wide range of setback asymmetric-plan reinforced concrete wall structures using nonlinear time history analysis of reasonably realistic 3D structural models. Advantages of EMD include explicit consideration of nonlinear, torsional and ‘higher mode’ effects. The method produces capacity-designed design actions for all reinforced concrete walls in the seismic structural system. EMD only requires three response spectrum type analyses. It does not require time history analysis or pushover analysis. EMD is a practical seismic design method for generally irregular RC wall buildings that uses analysis techniques that most engineering practitioners are familiar and confident with. It was found that for over 95% of the structures considered, EMD achieved critical mean peak responses between ??20 and +?15% of the target response values, with a median of ??5%. This significant improvement in design accuracy and reliability (compared to traditional force based design) was achieved at the relatively small additional computational effort of two Response Spectrum Analyses. This demonstrates the value that the proposed Effective Modal Design method adds to the current spectrum of seismic design methods for irregular ductile RC wall structures. 相似文献
27.
Ruth M. K. Plets S. Louise Callard J. Andrew G. Cooper Joseph T. Kelley Daniel F. Belknap Robin J. Edwards Antony J. Long Rory J. Quinn Derek W. T. Jackson 《第四纪科学杂志》2019,34(4-5):285-298
The interplay of eustatic and isostatic factors causes complex relative sea‐level (RSL) histories, particularly in paraglacial settings. In this context the past record of RSL is important in understanding ice‐sheet history, earth rheology and resulting glacio‐isostatic adjustment. Field data to develop sea‐level reconstructions are often limited to shallow depths and uncertainty exists as to the veracity of modelled sea‐level curves. We use seismic stratigraphy, 39 vibrocores and 26 radiocarbon dates to investigate the deglacial history of Belfast Lough, Northern Ireland, and reconstruct past RSL. A typical sequence of till, glacimarine and Holocene sediments is preserved. Two sea‐level lowstands (both max. ?40 m) are recorded at c. 13.5 and 11.5k cal a bp . Each is followed by a rapid transgression and subsequent periods of RSL stability. The first transgression coincides temporally with a late stage of Meltwater Pulse 1a and the RSL stability occurred between c. 13.0 and c. 12.2k cal a bp (Younger Dryas). The second still/slowstand occurred between c. 10.3 and c. 11.5k cal a bp . Our data provide constraints on the direction and timing of RSL change during deglaciation. Application of the Depth of Closure concept adds an error term to sea‐level reconstructions based on seismic stratigraphic reconstructions. 相似文献
28.
29.
Markov M. G. Markova I. A. Jarillo G. F. Ronquillo Pervago E. V. 《Izvestiya Physics of the Solid Earth》2020,56(3):357-363
Izvestiya, Physics of the Solid Earth - The problem of calculating the reflection and transmission coefficients of elastic P-wave incident from a porous half-space onto a fluid-filled crack is... 相似文献
30.
Michael C. Leaf Jessica S. A. Gay Matthew J. Newbould Owen R. Hewitt Steven L. Rogers 《Geology Today》2020,36(2):75-80
Algae is an informal term used to describe a broad group of simple organisms from the plant kingdom. The organisms included within this grouping are aquatic photosynthetic biota with an extensive range of life habits and forms. These organisms range from micron-sized unicellular forms to giant seaweeds and kelps, which can grow to several metres long. Both benthic and planktonic modes of life are known and display a wide variety of life cycles. 相似文献