全文获取类型
收费全文 | 1251篇 |
免费 | 53篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 49篇 |
大气科学 | 102篇 |
地球物理 | 294篇 |
地质学 | 406篇 |
海洋学 | 101篇 |
天文学 | 198篇 |
综合类 | 13篇 |
自然地理 | 147篇 |
出版年
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 14篇 |
2019年 | 26篇 |
2018年 | 40篇 |
2017年 | 28篇 |
2016年 | 45篇 |
2015年 | 26篇 |
2014年 | 44篇 |
2013年 | 99篇 |
2012年 | 45篇 |
2011年 | 49篇 |
2010年 | 47篇 |
2009年 | 69篇 |
2008年 | 74篇 |
2007年 | 58篇 |
2006年 | 43篇 |
2005年 | 39篇 |
2004年 | 43篇 |
2003年 | 48篇 |
2002年 | 39篇 |
2001年 | 36篇 |
2000年 | 18篇 |
1999年 | 19篇 |
1998年 | 21篇 |
1997年 | 19篇 |
1996年 | 25篇 |
1995年 | 17篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 14篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1981年 | 6篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1969年 | 4篇 |
排序方式: 共有1310条查询结果,搜索用时 30 毫秒
91.
Mark S. T. Bukowinski Philip E. Wannamaker Manfred Koch Yukio Fujinawa Dr. Pradeep Talwani D. Möhlmann Andrew H. Knoll Lucia Lovison-Golob Krzysztof Haman Hanna Pawłowska Henryk Piwkowski Dr. Anthony Dore Nguyen Xuan Huy Edward R. Cook Jan Błecki Jacek Leliwa-Kopystynski Magdalena Sroczynska-Kozuchowska 《Pure and Applied Geophysics》1993,140(1):139-177
92.
The olivine phenocrysts of four basalts (12004, 12008, 12009 and 12022) are concentrically zoned and have core compositions about as magnesian as experimentally produced liquidas olivines, features which suggest fractional crystallization and absence of Fe-Mg reequilibration. In the magnesium- and olivine-rich granular basalt 12035, the olivines are either unzoned or are zoned toward adjacent grains and have compositions more iron-rich than either cumulus olivines or liquidus olivines (should the rock represent the composition of a melt), features which suggest extensive Fe-Mg re-equilibration. 相似文献
93.
Anthony Hall 《Contributions to Mineralogy and Petrology》1971,32(3):186-192
A comparison has been made between the average compositions of the granites in the Variscan, Caledonian, and Alpine orogenic belts of western Europe. Their respective compositions lie near the isobaric minima in the system Q-Or-Ab-H2O for successively higher water pressures, whereas metamorphic facies series indicate that the three orogenic belts developed under successively lower geothermal gradients. These relationships are consistent with an origin of the granitic magmas by partial melting in the crust. 相似文献
94.
95.
Anthony L. Turkevich 《Earth, Moon, and Planets》1973,8(3):365-367
The available data on the chemical composition of the lunar surface at eleven sites (3 Surveyor, 5 Apollo and 3 Luna) are used to estimate the amounts of principal chemical elements (those present in more than about 0.5% by atom) in average lunar surface material. The terrae of the Moon differ from the maria in having much less iron and titanium and appreciably more aluminum and calcium.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973. 相似文献
96.
A finite element model for the prediction of discrete fracture propagation in rock structures loaded in compression is presented. The model integrates any one of three theories for mixed-mode fracture initiation; it contains an energy balance algorithm for predicting crack increment length, and incorporates recent developments in finite element stress-intensity factor computation. The predictions of the model are compared with the observed fracture response of a real rock structure. Results show that the model accurately predicts both stable and unstable fracture progagations observed experimentally. 相似文献
97.
Anthony L. Turkevich 《Earth, Moon, and Planets》1972,5(3-4):411-421
The principal chemical element composition and inferred mineralogy of the powdered lunar surface material at seven mare and one terra sites on the Moon are compared. The mare compositions are all similar to one another and comparable to those of terrestrial ocean ridge basalts except in having higher titanium and much lower sodium contents than the latter. These analyses suggest that most, if not all, lunar maria have this chemical composition and are derived from rocks with an average density of 3.19 g cm–3. Mare Tranquillitatis differs from the other maria in having twice the titanium content of the others.The chemical composition of the single highland site studied (Surveyor 7) is distinctly different from that of any of the maria in having much lower amounts of titanium and iron and larger amounts of aluminium and calcium. Confirmation of these general characteristics of lunar highland material has come from recent observations by the Apollo 15 Orbiter. The inferred mineralogy is 45 mole percent high anorthite plagioclase and the parent rocks have an estimated density of 2.94 g cm–3. The Surveyor 7 chemical composition is the principal contributor to present estimates of the overall chemical composition of the lunar surface.Presented at the NATO Advanced Study Institute on Lunar Studies, Patras, Greece, September 14–25, 1971. This paper is an expanded and updated version of a paper presented at the Apollo 12 Lunar Science Conference, Houston, Texas, January 11–14, 1971, and published in the Proceedings of this Conference (Turkevich, 1971). 相似文献
98.
Owen R Buxton L Sarkis S Toaspern M Knap A Depledge M 《Marine pollution bulletin》2002,44(10):1010-1017
The use of sequential measurements of hemolymph cholinesterase activities as a non-invasive biomarker of seasonal organophosphate/carbamate exposure was investigated for the tropical scallop, Euvola (Pecten) ziczac. Overall activities of both acetylcholinesterase and butyrylcholinesterase were relatively high compared to studies with bivalve tissues. Acute in vivo experiments showed inhibition of hemolymph acetylcholinesterase activity at concentrations of the organophosphate insecticide chlorpyrifos of 0.1, 1 and 10 ng l(-1). Monthly sampling of hemolymph from scallops at two sites in Bermuda over a 15 month period showed seasonal acetylcholinesterase and butyrylcholinesterase inhibition. Direct and indirect evidence suggests that this inhibition did not relate to biochemical or physiological changes associated with gonad maturation and spawning, but rather reflected diffuse contamination of the marine environment by cholinesterase inhibitors or increased bioavailability of such inhibitors at these times. Repetitive sampling of scallop hemolymph for cholinesterase activities represents a rapid, sensitive and non-invasive method for assessing seasonal, sublethal pesticide exposure in these commercially important bivalves and suggests a wider use in marine pollution monitoring. 相似文献
99.
100.