全文获取类型
收费全文 | 548篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 20篇 |
大气科学 | 20篇 |
地球物理 | 143篇 |
地质学 | 152篇 |
海洋学 | 73篇 |
天文学 | 82篇 |
综合类 | 1篇 |
自然地理 | 72篇 |
出版年
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 32篇 |
2012年 | 12篇 |
2011年 | 29篇 |
2010年 | 16篇 |
2009年 | 15篇 |
2008年 | 19篇 |
2007年 | 16篇 |
2006年 | 18篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 24篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 17篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1988年 | 4篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 10篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1968年 | 5篇 |
1948年 | 3篇 |
排序方式: 共有563条查询结果,搜索用时 46 毫秒
1.
Craig E. Divine Jesse Wright Michelle Crimi J.F. Devlin Michael Lubrecht Jack Wang Jeff McDonough Michael Kladias Jesse Hinkle Allison Cormican Trevor Osorno Blossom N. Nzeribe Fiona Laramay Daniel Ombalski Kathleen Gerber Hunter Anderson 《Ground Water Monitoring & Remediation》2020,40(3):42-54
The horizontal reactive media treatment well (HRX Well®) uses directionally drilled horizontal wells filled with a treatment media to induce flow-focusing behavior created by the well-to-aquifer permeability contrast to passively capture proportionally large volumes of groundwater. Groundwater is treated in situ as it flows through the HRX Well and downgradient portions of the aquifer are cleaned via elution as these zones are flushed with clean water discharging from the HRX Well. The HRX Well concept is particularly well suited for sites where long-term mass discharge control is a primary performance objective. This concept is appropriate for recalcitrant and difficult-to-treat constituents, including chlorinated solvents, per- and polyfluoroalkyl substances (PFAS), 1,4-dioxane, and metals. A full-scale HRX Well was installed and operated to treat trichloroethene (TCE) with zero valent iron (ZVI). The model-predicted enhanced flow through the HRX Well (compared to the flow in and equivalent cross-sectional area orthogonal to flow in the natural formation before HRX Well installation) and treatment zone width was consistent with flows and widths estimated independently by point velocity probe (PVP) testing, HRX Well tracer testing, and observed treatment in downgradient monitoring wells. The actual average capture zone width was estimated to be between 45 and 69 feet. Total TCE mass discharge reduction was maintained through the duration of the performance monitoring period and exceeded 99.99% (%). Decreases in TCE concentrations were observed at all four downgradient monitoring wells within the treatment zone (ranging from 50 to 74% at day 436), and the first arrival of treated water was consistent with model predictions. The field demonstration confirmed the HRX Well technology is best suited for long-term mass discharge control, can be installed under active infrastructure, requires limited ongoing operation and maintenance, and has low life cycle energy and water requirements. 相似文献
2.
Rachel E. Adams Ayumi Hyodo Toby SantaMaria Cynthia L. Wright Thomas W. Boutton Jason B. West 《水文研究》2020,34(4):991-1003
Questions persist about interpreting isotope ratios of bound and mobile soil water pools, particularly relative to clay content and extraction conditions. Interactions between pools and resulting extracted water isotope composition are presumably related to soil texture, yet few studies have manipulated the bound pool to understand its influence on soil water processes. Using a series of drying and spiking experiments, we effectively labelled bound and mobile water pools in soils with varying clay content. Soils were first vacuum dried to remove residual water, which was then replaced with heavy isotope-enriched water prior to oven drying and spiking with heavy isotope-depleted water. Water was extracted via centrifugation or cryogenic vacuum distillation (at four temperatures) and analysed for oxygen and hydrogen isotope ratios via isotope ratio mass spectrometry. Water from centrifuged samples fell along a mixing line between the two added waters but was more enriched in heavy isotopes than the depleted label, demonstrating that despite oven drying, a residual pool remains and mixes with the mobile water. Soils with higher clay + silt content appeared to have a larger bound pool. Water from vacuum distillation samples have a significant temperature effect, with high temperature extractions yielding progressively more heavy isotope-enriched values, suggesting that Rayleigh fractionation occurred at low temperatures in the vacuum line. By distinctly labelling bound and mobile soil water pools, we detected interactions between the two that were dependent on soil texture. Although neither extraction method appeared to completely extract the combined bound and mobile (total water) pool, centrifugation and high temperature cryogenic vacuum distillations were comparable for both δ2H and δ18O of soil water isotope ratios. 相似文献
3.
Willie Jamaal Wright 《The Professional geographer》2019,71(1):172-178
This article is a discussion and critique of public intellectualism in the present. Rather than reify a self-aggrandized form of public intellectualism within academia that centers individualized intellectual development and that encourages a greater flow of findings outward to communities, I highlight black women public intellectuals who have used their skills, talents, and station within the university and society in novel ways. Moreover, I suggest that scholars take seriously the questions, research methods, and analyses emerging from the general public, particularly from within communal and political organizations. These encouragements are illustrated by highlighting three political education workshops that have been developed across the United States. 相似文献
4.
Jaume Vergés Yohann Poprawski Ylènia Almar Peter A. Drzewiecki Mar Moragas Telm Bover-Arnal Chiara Macchiavelli Wayne Wright Grégoire Messager Jean-Christophe Embry David Hunt 《Basin Research》2020,32(6):1653-1684
Integration of extensive fieldwork, remote sensing mapping and 3D models from high-quality drone photographs relates tectonics and sedimentation to define the Jurassic–early Albian diapiric evolution of the N–S Miravete anticline, the NW-SE Castel de Cabra anticline and the NW-SE Cañada Vellida ridge in the Maestrat Basin (Iberian Ranges, Spain). The pre shortening diapiric structures are defined by well-exposed and unambiguous halokinetic geometries such as hooks and flaps, salt walls and collapse normal faults. These were developed on Triassic salt-bearing deposits, previously misinterpreted because they were hidden and overprinted by the Alpine shortening. The Miravete anticline grew during the Jurassic and Early Cretaceous and was rejuvenated during Cenozoic shortening. Its evolution is separated into four halokinetic stages, including the latest Alpine compression. Regionally, the well-exposed Castel de Cabra salt anticline and Cañada Vellida salt wall confirm the widespread Jurassic and Early Cretaceous diapiric evolution of the Maestrat Basin. The NE flank of the Cañada Vellida salt wall is characterized by hook patterns and by a 500-m-long thin Upper Jurassic carbonates defining an upturned flap, inferred as the roof of the salt wall before NE-directed salt extrusion. A regional E-W cross section through the Ababuj, Miravete and Cañada-Benatanduz anticlines shows typical geometries of salt-related rift basins, partly decoupled from basement faults. These structures could form a broader diapiric region still to be investigated. In this section, the Camarillas and Fortanete minibasins displayed well-developed bowl geometries at the onset of shortening. The most active period of diapiric growth in the Maestrat Basin occurred during the Early Cretaceous, which is also recorded in the Eastern Betics, Asturias and Basque-Cantabrian basins. This period coincides with the peak of eastward drift of the Iberian microplate, with speeds of 20 mm/year. The transtensional regime is interpreted to have played a role in diapiric development. 相似文献
5.
6.
N.J. Hogancamp V.P. Wright 《Proceedings of the Geologists' Association. Geologists' Association》2021,132(1):93-101
A revised age provided by conodonts from the Gilwern Oolite of the Clydach area of South Wales allows a clearer understanding of the palaeohydrology, palaeoclimatic history and diagenesis of previously correlated oolitic units. Earlier uncertainty over the apparent sub-regional differences in climate during the early Visean (Chadian—Arundian) lowstand is resolved. Previously a humid interval evidenced by prominent palaeo-epikarst capping the Gilwern Oolite along the northern outcrops of the South Wales synclinorium, was not recognized in what were regarded as correlative outcrops in the Chadian Gully Oolite in the southern part of the synclinorium. Conodont dating now shows that the Gilwern Oolite is much older (Courceyan) than the Chadian Gully Oolite, and during the prolonged exposure of the former there was an interval of weathering under a humid climate. This also explains the contrast between the diagenesis seen between the Gilwern and Gully oolites, which are no longer seen as correlatives. 相似文献
7.
A suite of deep‐sea cores were collected along transects up to 100 km across the fore‐arc and back‐arc regions of the predominantly submarine Kermadec arc near Raoul and Macauley islands, southwest Pacific. The cores reveal a macroscopic tephra record extending back >50 ka. This is a significant addition to the dated record of volcanism, previously restricted to fragmented late Holocene records exposed on the two islands. The 27 macroscopic tephra layers display a wide compositional diversity in glass (~50–78 wt% SiO2). Many tephra layers comprise silicic shards with a subordinate mafic shard population. This could arise from magma mingling and may reflect mafic triggering of the silicic eruptions. Broadly, the glass compositions can be distinguished on diverging high‐K and low‐K trends, most likely arising from different source volcanoes. This distinction is also reflected in the tephra records exposed on Raoul (low‐K) and Macauley (high‐K) islands, the likely source areas. Heterogeneous tephra comprising shards of both high‐ and low‐K affinity, silicic and mafic compositions, and more homogeneous tephra with subordinate outlier shard compositions, are best explained by post‐depositional mixing of separate eruption deposits or contemporaneous eruptions. Evidently, the slow sedimentation rates of the calcareous oozes (~101–102 mm ka?1) were insufficient to adequately separate and preserve closely spaced eruption deposits. This exemplifies the difficulty in assessing eruption frequencies and magmatic trends, and erecting a tephrostratigraphy, using geochemical fingerprinting in such environments. Despite these difficulties, the ca. 5.7 ka Sandy Bay Tephra erupted from Macauley Island can be correlated over a distance of >100 km, extending east and west of the island, showing that the mostly submerged volcanoes are capable of wide tephra dispersal. Hence there is potential for developing chronostratigraphies for the southwest Pacific beyond the region covered by the extensive rhyolite marker beds from the Taupo Volcanic Zone. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
8.
Erodibility of low‐compaction steep‐sloped reclaimed surface mine lands in the southern Appalachian region,USA 下载免费PDF全文
The use of loose spoils on steep slopes for surface coal mining reclamation sites has been promoted by the US Department of Interior, Office of Surface Mining for the establishment of native forest, as prescribed by the Forest Reclamation Approach (FRA). Although low‐compaction spoils improve tree survival and growth, erodibility on steep slopes was suspected to increase. This study quantified a combined KC factor (combining the effects of the soil erodibility K factor and cover management C) for low compaction, steep‐sloped (>20°) reclaimed mine lands in the Appalachian region, USA. The combined KC factor was used because standard Unit Plot conditions required to separate these factors, per Revised Universal Soil Loss Equation (RUSLE) experimental protocols, were not followed explicitly. Three active coal mining sites in the Appalachian region of East Tennessee, each containing four replicate field plots, were monitored for rainfall and sediment yields during a 14‐month period beginning June 2009. Average cumulative erosivity for the study sites during the monitoring period was measured as 5248.9 MJ·mm·ha?1·h?1. The KC ranged between 0.001 and 0.05 t·ha·h·ha?1·MJ?1·mm?1, with the highest values occurring immediately following reclamation site construction as rills developed (June – August 2009). The KC for two study sites with about an 18–20 mm spoil D84 were above 0.01 t·ha·h·ha?1·MJ?1·mm?1 during rill development, and below 0.003 t·ha·h·ha?1·MJ?1·mm?1 after August 2009 for the post‐rill development period. The KC values for one site with a 40 mm spoil D84 were never above 0.008 t·ha·h·ha?1·MJ?1·mm?1 and also on average were lower, being more similar to the other two sites after the rill development period. Based on an initial KC factor (Ke) measured during the first few storm events, the average C factor (Ce) was estimated as 0.58 for the rill development period and 0.13 for the post‐rill development period. It appears that larger size fractions of spoils influence KC and Ce factors on low‐compaction steep slopes reclamation sites. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
9.
10.