全文获取类型
收费全文 | 64586篇 |
免费 | 836篇 |
国内免费 | 494篇 |
专业分类
测绘学 | 1481篇 |
大气科学 | 4457篇 |
地球物理 | 12961篇 |
地质学 | 22491篇 |
海洋学 | 5488篇 |
天文学 | 15315篇 |
综合类 | 140篇 |
自然地理 | 3583篇 |
出版年
2021年 | 529篇 |
2020年 | 617篇 |
2019年 | 619篇 |
2018年 | 1443篇 |
2017年 | 1309篇 |
2016年 | 1609篇 |
2015年 | 999篇 |
2014年 | 1595篇 |
2013年 | 3150篇 |
2012年 | 1848篇 |
2011年 | 2494篇 |
2010年 | 2220篇 |
2009年 | 3078篇 |
2008年 | 2615篇 |
2007年 | 2631篇 |
2006年 | 2423篇 |
2005年 | 1888篇 |
2004年 | 1901篇 |
2003年 | 1787篇 |
2002年 | 1700篇 |
2001年 | 1543篇 |
2000年 | 1453篇 |
1999年 | 1274篇 |
1998年 | 1297篇 |
1997年 | 1266篇 |
1996年 | 1039篇 |
1995年 | 1031篇 |
1994年 | 923篇 |
1993年 | 806篇 |
1992年 | 753篇 |
1991年 | 734篇 |
1990年 | 835篇 |
1989年 | 716篇 |
1988年 | 645篇 |
1987年 | 847篇 |
1986年 | 701篇 |
1985年 | 911篇 |
1984年 | 1007篇 |
1983年 | 951篇 |
1982年 | 856篇 |
1981年 | 856篇 |
1980年 | 759篇 |
1979年 | 721篇 |
1978年 | 747篇 |
1977年 | 667篇 |
1976年 | 654篇 |
1975年 | 651篇 |
1974年 | 604篇 |
1973年 | 634篇 |
1972年 | 402篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
Oceanology - Field observations were applied to study the macrophytobenthos of the Abrau Peninsula of the Black Sea and the effect of the two most common and largest species of brown algae of the... 相似文献
972.
Underwater Acoustic Communications Using Vertical Receiver Arrays in Ice-Covered Shallow-Water Areas
Oceanology - The feasibility of underwater acoustic communications in an ice-covered shallow-water area is demonstrated in a field experiment and by computer modeling. The advantages of vertical... 相似文献
973.
Kuzmenko N. V. Tsyrlin V. A. Pliss M. G. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(10):1271-1292
Izvestiya, Atmospheric and Oceanic Physics - It is known that in mammals living in climates other than tropical, hemoconcentration is usually observed in winter. The average modern person actively... 相似文献
974.
Summary Nickel-copper mineralization occurs near the base of a diorite intrusion close to its contact with hornfelsed Ordovician and Silurian shales and greywackes. The principal ore minerals are nickeline, gersdorffite, pyrrhotine, pentlandite and chalcopyrite with minor amounts of molybdenite, tellurobismutite, gold, sphalerite and argentopentlandite. Pyrite, marcasite, violarite and goethite also occur but are interpreted as later alteration products. Much of the pyrrhotine-rich mineralization at the base of the intrusion is in the form of blebs and interstitial aggregates with amphiboles, plagioclase feldspar, biotite, chlorite and quartz. Chalcopyrite-rich and nickeline-gersdorffite-rich mineralization occurs above this and immediately below unmineralized diorite in the form of patches, lenticular masses and stringers along joints and fractures.Whole rock and ore analyses and electron microprobe data on the silicates, sulphides and sulpharsenides are presented.The unmineralized diorite has low SiO2 and high MgO contents compared to typical diorites and relatively high Cr, Ni and Ti trace element values. In the mineralized diorite, platinum-group elements occur in very low concentrations in the pyrrhotineand chalcopyrite-rich assemblages but Pt, Pd and Au show significant enrichment in the nickeline-gersdorffite-rich mineralization.A magmatic origin for the mineralization is proposed rather than formation by hydrothermal solutions or metasomatism.
With 3 Figures 相似文献
Die nickel-kupfer vererzung von Talnotry, Newton Stewart, Schottland
Zusammenfassung Die Nickel-Kupfer Vererzung befindet sich im Kontaktbereich einer Dioritintrusion mit hornfelsdurchdrungenen silurischen und ordovizischen Grauwacken. Die am häufigsten auftretenden Erzmineralien sind Nickelin, Gersdorffit, Pyrrhotin, Pentlandit, und Chalcopyrit mit kleineren Mengen von Molybdenit, Tellurwismuth, Gold, Sphalerit und Argentopentlandit. Weiters treten als spätere Umwandlungsprodukte Pyrit, Markasit, Violarit und Goethit auf. Ein großer Teil der Pyrrhotin-reichen Vererzung am Fuße des eingedrungenen Diorits bildet fleckige, lückenfüllende Aggregate zwischen den Silikatphasen (Amphibol, Plagioklas, Biotit, Chlorit, Quarz). Die Chalcopyrit- und Nickelin-Gersdorffit-reiche Vererzung tritt zwischen dem unvererzten Diorit im Hangenden und der Pyrrhotin-reichen Vererzung im Liegenden als linsige, lappenartige Konzentration und entlang von Fugen und Brücken auf.Vollgesteins-Analysen sowie ausgewählte Erzanalysen und Mikrosondenergebnisse der Silikate, Sulfide und Sulfarsenide liegen vor.Im Unterschied zu den typischen Dioriten zeigt der unvererzte Diorit einen niedrigen SiO2 und hohen MgO Gehalt und relativ hohe Cr, Ni und Ti Spurenelementwerte. Die Platingruppenelemente sind in den Pyrrhotin- und Chalcopyrit-reichen Vererzungen nur schwach vertreten, jedoch sind Pt, Pd und An in der Gersdorffit-reichen Vererzung stark angereichert.Ein magmatischer Ursprung dieser Vererzung, im Gegensatz zu einer metasomatischen Entstehung oder Bildung aus hydrothermalen Lösungen wird vermutet.
With 3 Figures 相似文献
975.
976.
A. A. Zhamaletdinov A. N. Shevtsov E. P. Velikhov A. A. Skorokhodov V. E. Kolesnikov T. G. Korotkova P. A. Ryazantsev B. V. Efimov V. V. Kolobov M. B. Barannik P. I. Prokopchuk V. N. Selivanov Yu. A. Kopytenko E. A. Kopytenko V. S. Ismagilov M. S. Petrishchev P. A. Sergushin P. E. Tereshchenko B. V. Samsonov M. A. Birulya M. Yu. Smirnov T. Korja Yu. M. Yampolski A. V. Koloskov N. A. Baru S. V. Poljakov A. V. Shchennikov G. I. Druzhin W. Jozwiak J. Reda Yu. G. Shchors 《Izvestiya Atmospheric and Oceanic Physics》2015,51(8):826-857
977.
Guiomar Rotllant Carles G. Simeó Guillermo Guerao Marta Sastre Daniel F. R. Cleary Ricardo Calado Alicia Estévez 《Marine Ecology》2014,35(3):298-307
The spider crab Maja brachydactyla is an important commercial species in Europe and supports intensive fisheries in the NE Atlantic. A field survey was performed to assess long‐term and consecutive interannual (2005–2010) variation of the biochemical composition of newly hatched larvae of M. brachydactyla. Larval biochemical profiles differed significantly among years, with pronounced differences being recorded in 2010. Differences among batches of newly hatched larvae were mainly explained by the contribution of triacylglycerols and, to a lesser degree, by protein and lipid content. The use of different nutrition indices is discussed. The biochemical composition of newly hatched larvae from M. brachydactyla was highly variable, even though surveyed broodstock was obtained from the same local population and was always sampled during the same season. The unpredictable biochemical profiles of newly hatched larvae may condition their survival and recruitment. This largely overlooked aspect of larval variability should be considered in future fisheries management strategies and captive production of marine organisms that still rely on wild seeds. 相似文献
978.
Reservoir potential of Late Cretaceous terrestrial to shallow marine sandstones,Taranaki Basin,New Zealand 总被引:2,自引:0,他引:2
Late Cretaceous coals and coaly source rocks are the main source of hydrocarbons in the Taranaki Basin, yet to date there have not been any hydrocarbon discoveries within Cretaceous strata, and sandstone distribution and reservoir quality for this interval have been poorly understood. The Late Cretaceous sediments were deposited in several sub-basins across Taranaki, with their distribution largely determined by sediment supply, subsidence, and sea level change. In this study, we describe potential reservoir facies in well penetrations of Cretaceous strata in Taranaki, as well as from outcrop in northwest Nelson, on the southern edge of the basin. 相似文献
979.
Benoît Thibodeau Moritz F. Lehmann Jacqueline Kowarzyk Alfonso Mucci Yves Gélinas Denis Gilbert Roxane Maranger Mohammad Alkhatib 《Estuarine, Coastal and Shelf Science》2010
Water column concentrations and benthic fluxes of dissolved inorganic nitrogen (DIN) and oxygen (DO) were measured in the Gulf of St. Lawrence and the Upper and Lower St. Lawrence Estuary (USLE and LSLE, respectively) to assess the nitrogen (N) budget in the St. Lawrence (SL) system, as well as to elucidate the impact of bottom water hypoxia on fixed-N removal in the LSLE. A severe nitrate deficit, with respect to ambient phosphate concentrations (N*∼−10 μmol L−1), was observed within and in the vicinity of the hypoxic bottom water of the LSLE. Given that DO concentrations in the water column have remained above 50 μmol L−1, nitrate reduction in suboxic sediments, rather than in the water column, is most likely responsible for the removal of fixed N from the SL system. Net nitrate fluxes into the sediments, derived from pore water nitrate concentration gradients, ranged from 190 μmol m−2 d−1 in the hypoxic western LSLE to 100 μmol m−2 d−1 in the Gulf. The average total benthic nitrate reduction rate for the Laurentian Channel (LC) is on the order of 690 μmol m−2 d−1, with coupled nitrification-nitrate reduction accounting for more than 70%. Using average nitrate reduction rates derived from the observed water column nitrate deficit, the annual fixed-N elimination within the three main channels of the Gulf of St. Lawrence and LSLE was estimated at 411 × 106 t N, yielding an almost balanced N budget for the SL marine system. 相似文献
980.
This paper discusses the impact of local and national policies in the Philippines on the participation of indigenous peoples in relation to fisheries management. Specifically, this research focuses on the Tagbanua, an indigenous group in Coron Island, Palawan, on the western side of the Philippines. The struggle of the Tagbanua in reclaiming their ancestral title to the land and sea reflects broader moves toward self-determination, which is critical not only to their ancestral lands and waters, but also to their survival. Indigenous rights are essential in addressing social justice and in giving a greater voice that encourages indigenous peoples towards self-governing institutions and common management of resources. Significantly, the fundamental development of indigenous peoples lies in the recognition of their rights in their ancestral domain and the preservation of their culture, tradition, system, practices and their natural resources. This paper examines the Tagbanua experience, through a critical exploration of institutions and property rights, with attention to corresponding effects in reducing conflict with other stakeholders in the area, and in affecting the sustainability of fishery resources. 相似文献