全文获取类型
收费全文 | 101篇 |
免费 | 0篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 4篇 |
地球物理 | 32篇 |
地质学 | 23篇 |
海洋学 | 3篇 |
天文学 | 31篇 |
自然地理 | 7篇 |
出版年
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2013年 | 1篇 |
2012年 | 2篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 6篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2000年 | 4篇 |
1998年 | 1篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 3篇 |
排序方式: 共有101条查询结果,搜索用时 15 毫秒
1.
Predation is likely the primary source of mortality for juvenile penaeid shrimp and, therefore, a key factor driving their population dynamics. We sampled juvenile penaeids and their potential predators in a salt marsh from July to August 2012 to examine the impact of these predators and possible size-selective predation on the shrimp population. We quantified predator impact using the frequency of occurrence (FO) index and a relative predation index (RPI) that accounts for predator abundance and the number of shrimp consumed per individual predator. Size selectivity was assessed by comparing the size distribution of shrimp in the study area to the size distribution of shrimp removed from predator stomachs. Two penaeid species, white shrimp Litopenaeus setiferus and brown shrimp Farfantepenaeus aztecus, were collected, and most (86%) were juvenile white shrimp ≤?12 mm carapace length. Spotted seatrout Cynoscion nebulosus, which consumed relatively large shrimp, was the most important predator based on the FO index. Bay whiff Citharichthys spilopterus, which ate the smallest shrimp, was the most important predator based on the RPI. The size distribution of shrimp removed from predator stomachs differed from those collected in the study area; the smallest shrimp were disproportionally more abundant in predator stomachs. Using the RPI, we identified some potentially important predators (e.g., bay whiff) that may impact shrimp populations by consuming the smallest shrimp in estuarine nurseries. Our approach could be useful for examining predator impacts on other populations of juvenile penaeids and more generally for any prey consumed by fish predators. 相似文献
2.
Graham Ryder Douglas B. Stoeser Ursula B. Marvin Janice F. Bower John A. Wood 《Earth, Moon, and Planets》1975,14(3-4):327-357
Boulder 1, Station 2, Apollo 17 is a stratified boulder containing dark clasts and dark-rimmed light clasts set in a light-gray friable matrix. The gray to black clasts (GCBx and BCBx) are multigenerational, competent, high-grade metamorphic, and partially melted breccias. They contain a diverse suite of lithic clasts which are mainly ANT varieties, but include granites, basaltic-textured olivine basalts, troctolitic and spinel troctolitic basalts, and unusual lithologies such as KREEP norite, ilmenite (KREEP) microgabbro, and the Civet Cat norite, which is believed to be a plutonic differentiate. The GCBxs and BCBxs are variable in composition, averaging a moderately KREEPy olivine norite. The matrix consists of mineral fragments derived from the observed lithologies plus variable amounts of a component, unobserved as a clast-type, that approximates a KREEP basalt in composition, as well as mineral fragments of unknown derivation. The high-temperature GCBxs cooled substantially before their incorporation into the friable matrix of Boulder 1. The light friable matrix (LFBx) is texturally distinct from the competent breccia clasts and, apart from the abundant ANT clasts, contains clasts of a KREEPy basalt that is not observed in the competent breccias. The LFBx lacks such lithologies as the granites and the Civet Cat norite observed in the competent breccias and in detail is a distinct chemical as well as textural entity. We interpret the LFBx matrix as Serenitatis ejecta deposited in the South Massif, and the GCBx clasts as remnants of an ejecta blanket produced by an earlier impact. The source terrain for the Serenitatis impact consisted of the competent breccias, crustal ANT lithologies, and the KREEPy basalts, attesting to substantial lunar activity prior to the impact. The age of the older breccias suggests that the Serenitatis event is younger than 4.01±0.03 b.y. 相似文献
3.
87Sr/86Sr ratios of 15 samples of basalt dredged from Loihi Seamount range from 0.70334 to 0.70368. The basalt types range from tholeiite to basanite in composition and can be divided into six groups on the basis of abundances of K2O, Na2O, Rb and Sr and 87Sr/86Sr ratio. The isotopic data require that the various basalt types be derived from source regions differing in Sr isotopic composition. The Loihi basalts may be produced by mixing of isotopically distinct sources, but the tholeiites and alkalic basalts from Loihi do not show a well-developed inverse trend between Rb/Sr and 87Sr/86Sr that is characteristic of the later stages of Hawaiian volcanoes such as Haleakala and Koolau. 相似文献
4.
5.
Yousif K. Kharaka Evangelos Kakouros James J. Thordsen Gil Ambats Marvin M. Abbott 《Applied Geochemistry》2007
For the last 5 a, the authors have been investigating the transport, fate, natural attenuation and ecosystem impacts of inorganic and organic compounds in releases of produced water and associated hydrocarbons at the Osage-Skiatook Petroleum Environmental Research (OSPER) “A” and “B” sites, located in NE Oklahoma. Approximately 1.0 ha of land at OSPER “B”, located within the active Branstetter lease, is visibly affected by salt scarring, tree kills, soil salinization, and brine and petroleum contamination. Site “B” includes an active production tank battery and adjacent large brine pit, two injection well sites, one with an adjacent small pit, and an abandoned brine pit and tank battery site. Oil production in this lease started in 1938, and currently there are 10 wells that produce 0.2–0.5 m3/d (1–3 bbl/d) oil, and 8–16 m3/d (50–100 bbl/d) brine. Geochemical data from nearby oil wells show that the produced water source is a Na–Ca–Cl brine (∼150,000 mg/L TDS), with high Mg, but low SO4 and dissolved organic concentrations. Groundwater impacts are being investigated by detailed chemical analyses of water from repeated sampling of 41 boreholes, 1–71 m deep. The most important results at OSPER “B” are: (1) significant amounts of produced water from the two active brine pits percolate into the surficial rocks and flow towards the adjacent Skiatook reservoir, but only minor amounts of liquid petroleum leave the brine pits; (2) produced-water brine and minor dissolved organics have penetrated the thick (3–7 m) shale and siltstone units resulting in the formation of three interconnected plumes of high-salinity water (5000–30,000 mg/L TDS) that extend towards the Skiatook reservoir from the two active and one abandoned brine pits; and (3) groundwater from the deep section of only one well, BR-01 located 330 m upslope and west of the site, appear not to be impacted by petroleum operations. 相似文献
6.
Age of amphibolites associated with alpine peridotites in the Dinaride ophiolite zone,Yugoslavia 总被引:1,自引:0,他引:1
Marvin A. Lanphere Robert G. Coleman Steven Karamata Jakob Pamić 《Earth and Planetary Science Letters》1975,26(3):271-276
Amphibolites associated with alpine peridotites in the Central Ophiolite zone in Yugoslavia have K-Ar ages of 160–170 m.y. These amphibolites and associated peridotites underwent deep-seated metamorphism prior to tectonic emplacement into the sedimentary-volcanic assemblage of the Dinarides. The alpine peridotites and associated local rocks of the ophiolite suite are interpreted as Jurassic oceanic crust and upper mantle. 相似文献
7.
8.
Swan Island is a Honduran possession in the western Caribbean, located on the southeastern side of the Cayman Trench. Two sedimentary assemblages are found on the island: an older bedded sequence of mid-Tertiary age (Aquitanian or Burdigalian) and a younger sedimentary sequence of Late Pleistocene age. The older sequence is composed of a series of calcarenites, calcilutites, and siliciclastic mudstones; capping these are cliff-forming reefal carbonates of the younger sequence.The rocks of the older bedded sequence accumulated in deep water. Sedimentation consisted of a constant rain of pyroclastic debris interrupted by the episodic introduction of upslope carbonate material by turbidity currents. Uplift and deformation of this sequence was initiated sometime after the Early Miocene. By the Late Pleistocene, uplift had brought the rocks into water depths conducive to coral growth. Pleistocene sedimentation on the island was controlled by the interaction between tectonic uplift and eustatic sea-level changes. The primary controlling force on the tectonic history of the island is its proximity to the boundary between the North American and Caribbean plates. 相似文献
9.
10.
Nathalie Dubois Love Råman Vinnå Marvin Rabold Michael Hilbe Flavio S. Anselmetti Alfred Wüest Laetitia Meuriot Alice Jeannet Stéphanie Girardclos 《Sedimentology》2020,67(2):971-990
River engineering projects are developing rapidly across the globe, drastically modifying water courses and sediment transfer. Investigation of the impact of engineering works focuses usually on short-term impacts, thus a longer-term perspective is still missing on the effects that such projects have. The ‘Jura Water Corrections’ – the largest river engineering project ever undertaken in Switzerland – radically modified the hydrological system of Lake Biel in the 19th and 20th Century. The deviation of the Aare River into Lake Biel more than 140 years ago, in 1878, thus represents an ideal case study to investigate the long-term sedimentological impacts of such large-scale river rerouting. Sediment cores, along with new high-resolution bathymetric and seismic reflection datasets were acquired in Lake Biel to document the consequences of the Jura Water Corrections on the sedimentation history of Lake Biel. Numerous subaquatic mass transport structures were detected on all of the slopes of the lake. Notably, a relatively large mass transport complex (0·86 km2) was observed on the eastern shore, along the path of the Aare River intrusion. The large amount of sediment delivered by the Aare River since its deviation into the lake likely caused sediment overloading resulting in subaquatic mass transport. Alternatively, the dumping since 1963 in a subaquatic landfill of material excavated during the second phase of river engineering, when the channels flowing into and out of Lake Biel were widened and deepened, might have triggered the largest mass transport, dated to 1964 or 1965. Additional potential triggers include two nearby small earthquakes in 1964 and 1965 (MW 3·9 and 3·2, respectively). The data for this study indicate that relatively large mass transports have become recurrent in Lake Biel following the deviation of the Aare River, thus modifying hazard frequency for the neighbouring communities and infrastructure. 相似文献