全文获取类型
收费全文 | 523篇 |
免费 | 21篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 41篇 |
大气科学 | 37篇 |
地球物理 | 139篇 |
地质学 | 143篇 |
海洋学 | 77篇 |
天文学 | 64篇 |
综合类 | 3篇 |
自然地理 | 47篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 21篇 |
2013年 | 25篇 |
2012年 | 19篇 |
2011年 | 26篇 |
2010年 | 27篇 |
2009年 | 45篇 |
2008年 | 22篇 |
2007年 | 29篇 |
2006年 | 34篇 |
2005年 | 13篇 |
2004年 | 15篇 |
2003年 | 21篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有551条查询结果,搜索用时 15 毫秒
541.
Amy M. GAFFNEY Lars E. BORG Yemane ASMEROM Charles K. SHEARER Paul V. BURGER 《Meteoritics & planetary science》2011,46(1):35-52
Abstract– To better determine the effects of impact‐related processes on radiometric chronometers in meteorites, we undertook an isotopic study of experimentally shocked and heated samples of lunar basalt 10017. Shock experiments at 55 GPa were completed on one subsample, and a second subsample was heated in an evacuated quartz tube at 1000 °C for 170 h. A third subsample was maintained as a control. Samarium‐neodymium, Rb‐Sr, 238U‐206Pb, and 206Pb‐207Pb isotopic analyses were completed on mineral fractions (leached and unleached), leached whole rocks, and complementary acid leachates. Disturbance in the shocked and heated samples was evaluated through comparison of their isochron diagrams with those of the control sample. The Sm‐Nd isotope system was the least disturbed, the Rb‐Sr isotope system was more disturbed, and the 238U‐206Pb and 206Pb‐207Pb isotope systems were the most disturbed by shock and annealing. Samples that experienced extended heating demonstrated greater isotopic disturbances than shocked samples. In some cases, the true crystallization age was preserved, and in others, age information was degraded or destroyed. In no case did the experiments generate isochrons that maintained linearity while being rotated or completely reset. Although our results show that neither experimental shock nor thermal metamorphism alone can account for the discordant ages represented by different isotope systems in some Martian meteorites, we postulate that shock metamorphism may render a meteorite more susceptible than its unshocked counterpart to subsequent disturbance during extended impact‐related heating or aqueous alteration. The combination of these processes may result in the disparate chronometric information preserved in some meteorites. 相似文献
542.
Asplin Lars Albretsen Jon Johnsen Ingrid Askeland Sandvik Anne Dagrun 《Ocean Dynamics》2020,70(8):1151-1167
Ocean Dynamics - Norway has complicated dynamics in the coastal ocean and in the fjords. In this area is also the largest salmon aquaculture industry in the world. The salmon industry is valuable... 相似文献
543.
Goodliff Michael Bruening Thorger Schwichtenberg Fabian Li Xin Lindenthal Anja Lorkowski Ina Nerger Lars 《Ocean Dynamics》2019,69(10):1217-1237
Ocean Dynamics - Satellite data of both physical properties as well as ocean colour can be assimilated into coupled ocean-biogeochemical models with the aim to improve the model state. The physical... 相似文献
544.
1INTRODUCTIONReservoirsedimentationisrecognizedasoneofthemainproblemsafectingtheeconomicsofmanywaterresourcesprojects.Manmad... 相似文献
545.
Karina Hjelmervik Nils Melsom Kristensen André Staalstrøm Lars Petter Røed 《Ocean Dynamics》2017,67(7):949-958
To model currents in a fjord accurate tidal forcing is of extreme importance. Due to complex topography with narrow and shallow straits, the tides in the innermost parts of a fjord are both shifted in phase and altered in amplitude compared to the tides in the open water outside the fjord. Commonly, coastal tide information extracted from global or regional models is used on the boundary of the fjord model. Since tides vary over short distances in shallower waters close to the coast, the global and regional tidal forcings are usually too coarse to achieve sufficiently accurate tides in fjords. We present a straightforward method to remedy this problem by simply adjusting the tides to fit the observed tides at the entrance of the fjord. To evaluate the method, we present results from the Oslofjord, Norway. A model for the fjord is first run using raw tidal forcing on its open boundary. By comparing modelled and observed time series of water level at a tidal gauge station close to the open boundary of the model, a factor for the amplitude and a shift in phase are computed. The amplitude factor and the phase shift are then applied to produce adjusted tidal forcing at the open boundary. Next, we rerun the fjord model using the adjusted tidal forcing. The results from the two runs are then compared to independent observations inside the fjord in terms of amplitude and phases of the various tidal components, the total tidal water level, and the depth integrated tidal currents. The results show improvements in the modelled tides in both the outer, and more importantly, the inner parts of the fjord. 相似文献
546.
547.
548.
A strict formula for geoid-to-quasigeoid separation 总被引:3,自引:2,他引:1
Lars E. Sjöberg 《Journal of Geodesy》2010,84(11):699-702
The paper presented by Flury and Rummel (J Geod 83:829–847, 2009) discusses an important topographic correction to the traditional
formula for the quasigeoid-to-geoid separation. Nevertheless, as their formula is approximate, the reader may ask for its
relation to the strict one (defined as the one consistent with Bruns’s formula and the boundary condition of physical geodesy),
which is now derived. Although the result formally differs from that of Flury and Rummel, we show that the two formulas agree
to the centimetre level all over the Earth. We also discuss the practical computation of the topographic correction. 相似文献
549.
GNSS processing at CODE: status report 总被引:26,自引:19,他引:7
Rolf Dach Elmar Brockmann Stefan Schaer Gerhard Beutler Michael Meindl Lars Prange Heike Bock Adrian Jäggi Luca Ostini 《Journal of Geodesy》2009,83(3-4):353-365
Since May 2003, the Center for Orbit Determination in Europe (CODE), one of the analysis centers of the International GNSS Service, has generated GPS and GLONASS products in a rigorous combined multi-system processing scheme, which promises the best possible consistency of the orbits of both systems. The resulting products, in particular the satellite orbits and clocks, are easily accessible by the user community. In the first part of this article, we focus on the generation of the combined global products at CODE, where we put emphasis not only on accuracy, but also on completeness. We study the impact of GLONASS on the CODE products, and the benefit of using them. Last, but not least, we introduce AGNES (Automated GNSS Network for Switzerland), a regional tracking network of small extensions (roughly 400 km East–West, 200 km North–South), which consequently tracks all GNSS satellites and analyzes their measurements using the CODE products. 相似文献
550.
Michael B.W. Fyhn Lars H. Nielsen Lars O. Boldreel Le D. Thang Jørgen Bojesen-Koefoed Henrik I. Petersen Nguyen T. Huyen Nguyen A. Duc Nguyen T. Dau Anders Mathiesen Ian Reid Dang T. Huong Hoang A. Tuan Le V. Hien Hans P. Nytoft Ioannis Abatzis 《Marine and Petroleum Geology》2009
Seismic stratigraphic and structural analyses of the northwest Phu Khanh Basin, offshore Central Vietnam, based on 2-D seismic data, indicate that the initial rifting began during the latest Cretaceous? or Palaeogene controlled by left-lateral transtension along the East Vietnam Boundary Fault Zone (EVBFZ) and northwest–southeast directed extension east of the EVBFZ. Rifting stopped due to transpression during middle Oligocene times but resumed by left-lateral transtension during the Late Oligocene. Thick sequences of lacustrine and alluvial sediments were deposited during the Palaeogene rift periods. The Late Oligocene rifting ended due to inversion, triggered by right-lateral wrenching near the Palaeogene–Neogene boundary. Following the onset of this inversion regional uplift and volcanism took place in the southern half of the study area and contemporaneous subsidence and transgression took place farther north, leading to widespread carbonate deposition. As the right-lateral wrenching decreased during the early Neogene, thermal subsidence and siliciclastic sedimentation became dominant, resulting in the buildup and southward propagation of the shelf slope. Sediment accumulation and subsidence rates increased after the Middle Miocene times due to eastward tilting of Central Vietnam and the adjacent offshore area. 相似文献