全文获取类型
收费全文 | 133篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 17篇 |
地球物理 | 25篇 |
地质学 | 41篇 |
海洋学 | 15篇 |
天文学 | 23篇 |
自然地理 | 10篇 |
出版年
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 11篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 11篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 31 毫秒
61.
The recent assessment of the Mitchell Creek Landslide (MCL) in northern British Columbia is a good case history of engineering geomorphological analysis of a large landslide. It was completed using historic aerial photographs, with approximately 20-year time intervals dating back to the mid-twentieth century and field investigations completed between 2008 and 2014. The large bedrock slide initiated between 1956 and 1972 and continues to experience ongoing annual movements. Significant glacial downwasting and retreat has been observed in the photographic record, and it is hypothesized that alpine glaciation has contributed to development of the MCL. This paper documents four aspects of the engineering geomorphological assessment completed at the MCL: (i) topographic evolution, (ii) slope morphology, (iii) deformation features, and (iv) displacement behavior. Four distinct geomorphic zones have been defined at the MCL based on these analyses, controlled by different failure mechanisms. The extents of these zones have changed little over the documented history of the landslide, and rates of movement estimated from aerial photography have been consistent over the last 60 years. Retreat of the Mitchell Valley Glacier appears to have played an important role in landslide initiation, as the ice mass receded the kinematic freedom of the slope increased. This study of the initiation and development of the MCL demonstrates the capabilities of a multi-faceted approach to engineering geomorphology. The combination of historical aerial photographs with digital photogrammetric modeling and point cloud analysis techniques, and geomorphological mapping, allows for development of a robust understanding of landslide behavior. 相似文献
62.
Elisabetta Boaretto Charlotte Bryant Israel Carmi Gordon Cook Steinar Gulliksen Doug Harkness Jan Heinemeier John McClure Edward McGee Philip Naysmith Goran Possnert Marian Scott Hans van der Plicht Mark van Strydonck 《第四纪科学杂志》2002,17(7):633-637
Interlaboratory comparisons have been widely used in applied radiocarbon science. These are an important part of ongoing quality assurance (QA) programmes, which are vital to the appropriate interpretation of the evidence provided by the 14C record in Quaternary applications (including climate change and environmental reconstruction). International comparisons of laboratory performance are an essential component of the quality assurance process in radiocarbon dating. If the user community is to have confidence in radiocarbon results, it needs to be assured that laboratories world wide are producing measurements that are reliable and in accordance with ‘good practice’. The findings from the most recent (completed in 2001) and extensive (more than 90 participating laboratories) radiocarbon intercomparison (FIRI) are reported here. This study was designed (i) to assess comparability, or otherwise, of the results from different laboratories and (ii) to quantify the extent and possible causes of any interlaboratory variation. The results demonstrate that there are no significant differences amongst the main measurement techniques (gas proportional counting, liquid scintillation counting and accelerator mass spectrometry (AMS)) but there is evidence of small laboratory offsets relative to known age samples for some laboratories. There is also evidence in some cases of underestimation of measurement precision. Approximately 10% of all results were classified as extreme (outliers) and these results were generated by 14% of the laboratories. Overall, the evidence supports the fact that radiocarbon laboratories are generally accurate and precise but that, notwithstanding internal QA procedures, some problems still occur, which can best be detected by participation in independent intercomparisons such as FIRI, where the results allow individual laboratories to assess their performance and to take remedial measures where necessary. The results from FIRI are significant in that they show a broad measure of agreement between measurements made in different laboratories on a wide range of materials and they also demonstrate no statistically significant difference between measurements made by radiometric or AMS techniques. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
63.
Nancy Soontiens Susan E. Allen Doug Latornell Kate Le Souëf Idalia Machuca Jean-Philippe Paquin 《大气与海洋》2016,54(1):1-21
The Strait of Georgia is a large, semi-enclosed body of water between Vancouver Island and the mainland of British Columbia connected to the Pacific Ocean via Juan de Fuca Strait at the south and Johnstone Strait at the north. During the winter months, coastal communities along the Strait of Georgia are at risk of flooding caused by storm surges, a natural hazard that can occur when a strong storm coincides with high tide. This investigation produces storm surge hindcasts using a three-dimensional numerical ocean model for the Strait of Georgia and the surrounding bodies of water (Juan de Fuca Strait, Puget Sound, and Johnstone Strait) collectively known as the Salish Sea. The numerical model employs the Nucleus for European Modelling of the Ocean architecture in a regional configuration. The model is evaluated through comparisons of tidal elevation harmonics and storm surge with observations. Important forcing factors contributing to storm surges are assessed. It is shown that surges entering the domain from the Pacific Ocean make the most significant contribution to surge amplitude within the Strait of Georgia. Comparisons between simulations and high-resolution and low-resolution atmospheric forcing further emphasize that remote forcing is the dominant factor in surge amplitudes in this region. In addition, local wind patterns caused a slight increase in surge amplitude on the mainland side of the Strait of Georgia compared with Vancouver Island coastal areas during a major wind storm on 15 December 2006. Generally, surge amplitudes are found to be greater within the Strait of Georgia than in Juan de Fuca Strait. 相似文献
64.
65.
A technique is developed to separate the incident and reflected waves propagating on a known current in a laboratory wave–current flume by analyzing wave records measured at two or more locations using a least squares method. It can be applied to both regular and irregular waves. To examine its performance, numerical tests are made for waves propagating on quiescent or flowing water. In some cases, to represent the signal noise and measurement error, white noise is superimposed on the numerically generated wave signal. For all the cases, good agreement is observed between target and estimation. 相似文献
66.
Ken C. Macdonald Paul J. Fox Steve Miller Suzanne Carbotte Margo H. Edwards Mark Eisen Daniel J. Fornari Laura Perram Rob Pockalny Dan Scheirer Stacey Tighe Charles Weiland Doug Wilson 《Marine Geophysical Researches》1992,14(4):299-344
SeaMARC II and Sea Beam bathymetric data are combined to create a chart of the East Pacific Rise (EPR) from 8°N to 18°N reaching at least 1 Ma onto the rise flanks in most places. Based on these data as well as SeaMARC II side scan sonar mosaics we offer the following observations and conclusions. The EPR is segmented by ridge axis discontinuities such that the average segment lengths in the area are 360 km for first-order segments, 140 km for second-order segments, 52 km for third-order segments, and 13 km for fourth-order segments. All three first-order discontinuities are transform faults. Where the rise axis is a bathymetric high, second-order discontinuities are overlapping spreading centers (OSCs), usually with a distinctive 3:1 overlap to offset ratio. The off-axis discordant zones created by the OSCs are V-shaped in plan view indicating along axis migration at rates of 40–100 mm yr–1. The discordant zones consist of discrete abandoned ridge tips and overlap basins within a broad wake of anomalously deep bathymetry and high crustal magnetization. The discordant zones indicate that OSCs have commenced at different times and have migrated in different directions. This rules out any linkage between OSCs and a hot spot reference frame. The spacing of abandoned ridges indicates a recurrence interval for ridge abandonment of 20,000–200,000 yrs for OSCs with an average interval of approximately 100,000 yrs. Where the rise axis is a bathymetric low, the only second-order discontinuity mapped is a right-stepping jog in the axial rift valley. The discordant zone consists of a V-shaped wake of elongated deeps and interlocking ridges, similar to the wakes of second-order discontinuities on slow-spreading ridges. At the second-order segment level, long segments tend to lengthen at the expense of neighboring shorter segments. This can be understood if segments can be approximated by cracks, because the propagation force at a crack tip is directly proportional to crack length.There has been a counter-clockwise change in the direction of spreading on the EPR between 8 and 18° N during the last 1 Ma. The cumulative change has been 3°–6°, producing opening across the Orozco and Siqueiros transform faults and closing across the Clipperton transform. The instantaneous present-day Cocos-Pacific pole is located at approximately 38.4° N, 109.5° W with an angular rotation rate of 2.10° m.y.–1 This change in spreading direction explains the predominance of right-stepping discontinuities of orders 2–4 along the Siqueiros-Clipperton and Orozco-Rivera segments, but does not explain other aspects of segmentation which are thought to be linked to patterns of melt supply to the ridge axis.There are 23 significant seamount chains in the mapped area and most are created very near the spreading axis. Nearly all of the seamount chains have trends which fall between the absolute and relative plate motion vectors. 相似文献
67.
Philip E.BETT Adam A.SCAIFE Chaofan LI Chris HEWITT Nicola GOLDING Peiqun ZHANG Nick DUNSTONE Doug M.SMITH Hazel E.THORNTON Riyu LU Hong-Li REN 《大气科学进展》2018,35(8):918-926
The Yangtze River has been subject to heavy flooding throughout history,and in recent times severe floods such as those in 1998 have resulted in heavy loss of life and livelihoods.Dams along the river help to manage flood waters,and are important sources of electricity for the region.Being able to forecast high-impact events at long lead times therefore has enormous potential benefit.Recent improvements in seasonal forecasting mean that dynamical climate models can start to be used directly for operational services.The teleconnection from El Ni ?no to Yangtze River basin rainfall meant that the strong El Ni ?no in winter 2015/16 provided a valuable opportunity to test the application of a dynamical forecast system.This paper therefore presents a case study of a real-time seasonal forecast for the Yangtze River basin,building on previous work demonstrating the retrospective skill of such a forecast.A simple forecasting methodology is presented,in which the forecast probabilities are derived from the historical relationship between hindcast and observations.Its performance for2016 is discussed.The heavy rainfall in the May–June–July period was correctly forecast well in advance.August saw anomalously low rainfall,and the forecasts for the June–July–August period correctly showed closer to average levels.The forecasts contributed to the confidence of decision-makers across the Yangtze River basin.Trials of climate services such as this help to promote appropriate use of seasonal forecasts,and highlight areas for future improvements. 相似文献
68.
69.
Robert Wood Doug Johnson Simon Osborne Meinrat O. Andreae Brain Bandy Timothy S. Bates Colin O'Dowd Paul Glantz Kevin Noone Patricia K. Quinn Jochen Rudolph Karsten Suhre 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):401-422
Aircraft measurements are presented of the Lagrangian evolution of a marine boundary layer over a 30‐h period during the ACE‐2 field campaign. At the start of the observational period, a 500‐m deep polluted marine internal boundary layer (MIBL) was overlain by the remnants of a polluted continental boundary layer extending to around 2 km below a clean, dry free troposphere. The MIBL grew rapidly to a thickness of 900–1000 m in response to increasing sea surface temperatures. No significant aerosol spectral evolution was observed in the boundary layer. Low concentrations of SO2 were observed in the MIBL suggesting that the air mass contained relatively aged aerosol. Aerosol spectra show a broad mode with a modal diameter of around 0.1μm. The polluted layer between the MIBL and the unpolluted free troposphere was only weakly and intermittently turbulent which prevented significant entrainment of clean air into the polluted layer from aloft. The polluted layer depth was thus controlled mainly by subsidence which as a result becomes shallower, decreasing from over 2000 m to around 1200 m during the observational period. The aerosol characteristics of the polluted layer were similar to those in the MIBL and so although the MIBL entrained considerable amounts of air from above the MIBL the aerosol characteristics underwent no significant change. This has important implications for the rate at which a polluted continental air mass is converted to a clean marine one. The dataset should prove useful in the validation of the modelling of continental pollution outbreaks. 相似文献
70.
Three-dimensional slope stability analysis of South Peak, Crowsnest Pass, Alberta, Canada 总被引:2,自引:2,他引:0
Marc-Andr�� Brideau Andrea Pedrazzini Doug Stead Corey Froese Michel Jaboyedoff David van Zeyl 《Landslides》2011,8(2):139-158
South Peak is a 7-Mm3 potentially unstable rock mass located adjacent to the 1903 Frank Slide on Turtle Mountain, Alberta. This paper presents
three-dimensional numerical rock slope stability models and compares them with a previous conceptual slope instability model
based on discontinuity surfaces identified using an airborne LiDAR digital elevation model (DEM). Rock mass conditions at
South Peak are described using the Geological Strength Index and point load tests, whilst the mean discontinuity set orientations
and characteristics are based on approximately 500 field measurements. A kinematic analysis was first conducted to evaluate
probable simple discontinuity-controlled failure modes. The potential for wedge failure was further assessed by considering
the orientation of wedge intersections over the airborne LiDAR DEM and through a limit equilibrium combination analysis. Block
theory was used to evaluate the finiteness and removability of blocks in the rock mass. Finally, the complex interaction between
discontinuity sets and the topography within South Peak was investigated through three-dimensional distinct element models
using the code 3DEC. The influence of individual discontinuity sets, scale effects, friction angle and the persistence along
the discontinuity surfaces on the slope stability conditions were all investigated using this code. 相似文献