全文获取类型
收费全文 | 1345篇 |
免费 | 49篇 |
国内免费 | 25篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 114篇 |
地球物理 | 274篇 |
地质学 | 495篇 |
海洋学 | 119篇 |
天文学 | 214篇 |
综合类 | 14篇 |
自然地理 | 165篇 |
出版年
2023年 | 7篇 |
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 34篇 |
2017年 | 20篇 |
2016年 | 23篇 |
2015年 | 39篇 |
2014年 | 40篇 |
2013年 | 82篇 |
2012年 | 49篇 |
2011年 | 83篇 |
2010年 | 54篇 |
2009年 | 68篇 |
2008年 | 58篇 |
2007年 | 76篇 |
2006年 | 58篇 |
2005年 | 46篇 |
2004年 | 37篇 |
2003年 | 33篇 |
2002年 | 40篇 |
2001年 | 22篇 |
2000年 | 32篇 |
1999年 | 25篇 |
1998年 | 20篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 14篇 |
1994年 | 22篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 27篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 13篇 |
1974年 | 7篇 |
1973年 | 11篇 |
排序方式: 共有1419条查询结果,搜索用时 15 毫秒
951.
Anaerobic Biodegradation of MTBE at a Gasoline Spill Site 总被引:4,自引:0,他引:4
952.
Cross-matching with interpreted warping of 3D streamer and 3D ocean-bottom-cable data at Valhall for time-lapse assessment 总被引:1,自引:0,他引:1
Stephen A. Hall Colin MacBeth Olav I. Barkved Philip Wild 《Geophysical Prospecting》2005,53(2):283-297
Legacy streamer data and newer 3D ocean‐bottom‐cable data are cross‐matched and analysed for time‐lapse analysis of geomechanical changes due to production in the Valhall Field. The issues relating to time‐lapse analysis using two such distinctly different data sets are addressed to provide an optimal cross‐matching workflow that includes 3D warping. Additionally an assessment of the differences between the imaging using single‐azimuth streamer and multi‐azimuth ocean‐bottom‐cable data is provided. The 3D warping utilized in the cross‐matching procedure is sensitive to acquisition and processing differences but is also found to provide valuable insight into the geometrical changes that occur in the subsurface due to production. As such, this work also provides a demonstration of the use of high‐resolution 3D interpreted warping to resolve the 3D heterogeneity of the compaction and subsidence. This is an important tool for Valhall, and possibly other fields, where compaction and subsidence (and monitoring thereof) are key factors in the reservoir management since the predominant observed production‐induced changes are compaction of the soft, high‐porosity chalk reservoir, due to pore‐pressure reduction, and the resultant overburden subsidence. Such reservoir compaction could have significant implications for production by changing permeabilities and production rates. Furthermore the subsidence effects could impact upon subsea installations and well‐bore stability. Geomechanical studies that have previously been used to model such subsidence and compaction are only constrained by observed surface displacements and measured reservoir pressure changes, with the geological overburden being largely neglected. The approaches suggested herein provide the potential for monitoring and assessment in three dimensions, including the probable heterogeneity and shearing, that is needed for full understanding of reservoir compaction and the resultant effects on the overburden to, for example, mitigate well‐bore failures. 相似文献
953.
954.
955.
The misorientation index: Development of a new method for calculating the strength of lattice-preferred orientation 总被引:5,自引:4,他引:5
Using orientation data from experimentally deformed olivine, we explore some practical problems with the J-index, a commonly applied measure of fabric strength. We show that the J-index is highly dependent on several factors, including the number of discrete data in the orientation distribution function (ODF), and arbitrary numerical parameters specified for its calculation. Because of this non-uniqueness, we conclude that the J-index is difficult to interpret and should only be applied with caution. As an alternative to the J-index, we propose a new measure of fabric strength that is based on the distribution of uncorrelated misorientation angles. This “M-index” is shown to be insensitive to the parameters specified for its calculation. For typical deformed olivine samples, we show that 150 discrete data are adequate to quantify fabric strength using the M-index technique. The M-index correlates well with seismic anisotropy, particularly for materials of the same fabric type. Therefore, we conclude that the M-index technique is well-suited for the quantification of fabric strength and the comparison of like materials. 相似文献
956.
Using Field-Portable XRF to Assess Geochemical Variations Within and Between Dolerite Outcrops of Preseli, South Wales 总被引:1,自引:0,他引:1
Michael C. Jones Olwen Williams-Thorpe Philip J. Potts Peter C. Webb 《Geostandards and Geoanalytical Research》2005,29(3):251-269
Eight dolerite outcrops in Preseli, south Wales were measured in situ using field-portable XRF analysis, in order to compare two different analysis ("sampling") strategies, and to investigate geochemical variability within and between outcrops. A sampling strategy of two (neighbouring but independent) measurements at each of a maximal number of locations dispersed over an outcrop was the more effective in indicating the overall chemical variance of that outcrop. Analysis of variance indicated that much of the observed variance within individual outcrops stems from real geochemical variability rather than from sampling and analytical factors. Standard ANOVA F tests showed that several of the studied outcrops are heterogeneous at the 5% significance level for one or more elements. Geochemical distinctions between some outcrops were demonstrated using discriminant analysis. PXRF analysis offers an alternative approach to conventional characterisation of outcrops, which is often based on laboratory analysis of small numbers of samples. However, PXRF data are affected by rock weathering and may require correction for this if they are to be compared with analyses of fresh rock. 相似文献
957.
A micro-seismic field experiment has been carried out in the Marmara Searegion. The analysis of the events before and after the August 17, 1999Izmit (Turkey) earthquake has been completed. 1446 events have beenwell located out of a total of 3165 recorded within the period from July15 to November 2, 1999. 67% of the aftershocks with magnitudegreater than 4 have occurred within the first 6 days after the main-shock. Earthquakes of the Izmit sequence are distributed in the first 15 km of theearth crust, but major events are located in between 5 km and 15 kmdepth. The seismicity pattern defines a rupture plane extending for about150 km in an E-W direction. The rupture is extremely linear butsegmented, and its complexity increases towards the western endmanifesting bifurcation. A stress analysis has been carried out both at thewestern end and all along the aftershock zone. 96 selected aftershocks,registered between August 21 and October 22, were chosen in order tocompute their focal mechanisms and obtain information about the stressregime after the Izmit earthquake. Strike-slip and normal faultingmechanisms are dominant. The numerous strike-slip mechanisms arecompatible with a dextral motion on an EW oriented vertical fault plane. The best stress tensor solution shows a regime in extension with awell-defined 3 axis oriented approximately N35°. 相似文献
958.
Prediction of diffusion coefficients in porous media using tortuosity factors based on interfacial areas 总被引:1,自引:0,他引:1
Determination of aqueous phase diffusion coefficients of solutes through porous media is essential for understanding and modeling contaminant transport. Prediction of diffusion coefficients in both saturated and unsaturated zones requires knowledge of tortuosity and constrictivity factors. No methods are available for the direct measurement of these factors, which are empirical in their definition. In this paper, a new definition for the tortuosity factor is proposed, as the real to ideal interfacial area ratio. We define the tortuosity factor for saturated porous media (tau5) as the ratio S/S(o) (specific surface of real porous medium to that of an idealized capillary bundle). For unsaturated media, tortuosity factor (tau(a)) is defined as a(aw)/a(aw),o (ratio of the specific air-water interfacial area of real and the corresponding idealized porous medium). This tortuosity factor is suitably measured using sorptive tracers (e.g., nitrogen adsorption method) for saturated media and interfacial tracers for unsaturated media. A model based on this new definition of tortuosity factors, termed the interfacial area ratio (IAR) model, is presented for the prediction of diffusion coefficients as a function of the degree of water saturation. Diffusion coefficients and diffusive resistances measured in a number of saturated and unsaturated granular porous media, for solutes in dilute aqueous solutions, agree well with the predictions of the IAR model. A comparison of permeability of saturated sands estimated based on tau(s) and the same based on the Kozeny-Carman equation confirm the usefulness of the tau(s) parameter as a measure of tortuosity. 相似文献
959.
960.