全文获取类型
收费全文 | 1692篇 |
免费 | 77篇 |
国内免费 | 32篇 |
专业分类
测绘学 | 40篇 |
大气科学 | 184篇 |
地球物理 | 398篇 |
地质学 | 628篇 |
海洋学 | 135篇 |
天文学 | 254篇 |
综合类 | 4篇 |
自然地理 | 158篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 30篇 |
2020年 | 33篇 |
2019年 | 22篇 |
2018年 | 48篇 |
2017年 | 43篇 |
2016年 | 74篇 |
2015年 | 45篇 |
2014年 | 67篇 |
2013年 | 114篇 |
2012年 | 54篇 |
2011年 | 100篇 |
2010年 | 84篇 |
2009年 | 96篇 |
2008年 | 94篇 |
2007年 | 100篇 |
2006年 | 99篇 |
2005年 | 63篇 |
2004年 | 67篇 |
2003年 | 52篇 |
2002年 | 53篇 |
2001年 | 43篇 |
2000年 | 33篇 |
1999年 | 36篇 |
1998年 | 26篇 |
1997年 | 19篇 |
1996年 | 20篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1993年 | 16篇 |
1992年 | 9篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 5篇 |
1987年 | 13篇 |
1986年 | 20篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1974年 | 8篇 |
1973年 | 6篇 |
排序方式: 共有1801条查询结果,搜索用时 93 毫秒
41.
This paper presents the experimental results of the mechanical production of silica and carbonate colloidal particles below 100 nm using two types of stirred bead mills (i.e., DCP Superflow 12 and PML H/V). It is shown that the stirred bead mill with very small beads can be used as an efficient equipment for the production of the colloidal particles in nanoscale from the feed materials of several microns in sizes at high energy consumptions. The DCP Superflow mill with high power densities is superior for the effective size reduction and production rate, compared to the conventional PML H/V mill with lower power densities. The smaller particles could be produced by the DCP Superflow mill at the same level of high energy inputs as from the PML H/V mill. The “grinding limit” for the processes in the mills has been discussed. 相似文献
42.
43.
44.
Susanne Skora Lukas P. Baumgartner Nancy J. Mahlen Clark M. Johnson Sébastien Pilet Eric Hellebrand 《Contributions to Mineralogy and Petrology》2006,152(6):703-720
Garnets from the Zermatt-Saas Fee eclogites contain narrow central peaks for Lu + Yb + Tm ± Er and at least one additional small peak towards the rim. The REE Sm + Eu + Gd + Tb ± Dy are depleted in the cores but show one prominent peak close to the rim. These patterns cannot be modeled using Rayleigh fractionation accompanied by mineral breakdown reactions. Instead, the patterns are well explained using a transient matrix diffusion model where REE uptake is limited by diffusion in the matrix surrounding the porphyroblast. Observed profiles are well matched if a roughly linear radius growth rate is used. The secondary peaks in the garnet profiles are interpreted to reflect thermally activated diffusion due to temperature increase during prograde metamorphism. The model predicts anomalously low 176Lu/177Hf and 147Sm/144Nd ratios in garnets where growth rates are fast compared to diffusion of the REE, and these results have important implications for Lu–Hf and Sm–Nd geochronology using garnet. 相似文献
45.
46.
Warren J. de Bruyn Mike Harvey Jill M. Cainey Eric S. Saltzman 《Journal of Atmospheric Chemistry》2002,41(2):189-209
Atmospheric dimethyl sulfide (DMS) and sulfur dioxide (SO2) concentrations were measured at Baring Head, New Zealandduring February and March 2000. Anti-correlated DMS and SO2 diurnalcycles, consistent with the photochemical production of SO2 from DMS, were observed in clean southerly air off the ocean. The data is used to infer a yield of SO2 from DMS oxidation. The estimated yields are highly dependent on assumptions about the DMS oxidation rate. Fitting the measured data in a photochemical box model using model-generated OH levels and the Hynes et al. (1986) DMS + OH rate constant suggests that theSO2 yield is 50–100%, similar to current estimates for the tropical Pacific.However, the observed amplitude of the DMS diurnal cycle suggests that the oxidation rate is higher than that used by the model, and therefore, that theSO2 yield is lower in the range of 20–40%. 相似文献
47.
R. Scott Anderson Mitchell J. Power Susan J. Smith Kathleen Springer Eric Scott 《Quaternary Research》2002,58(3):310
Analysis of a buried deposit in the Diamond Valley of southern California has revealed well-preserved pollen, wood, and diatom remains. Accelerator mass spectrometry dates of 41,200±2100 and 41,490±1380 14C yr B.P. place this deposit in marine isotope stage 3. Diatoms suggest a shallow lacustrine environment. Pollen data suggest that several plant communities were present near the site, with grassland, scrub, chaparral, forest, and riparian communities represented. Comparison with modern pollen suggests similarities with montane forests in the nearby San Bernardino and San Jacinto ranges, indicating vegetation lowering by at least 900 m elevation and temperatures 4°–5°C cooler than today. An increase in high-elevation conifer pollen documents climatic cooling near the profile top. Early-profile diatoms are typical of warm water with high alkalinity and conductivity, whereas later diatoms suggest a higher flow regime and input of cooler water into the system. We suggest that the sequence is part of the cooling phase of an interstadial Dansgaard–Oeschger cycle. Records of the middle Wisconsin period are rare in southern California, but the Diamond Valley site is similar to records from Tulare Lake in the San Joaquin Valley and the ODP Site 893A record from Santa Barbara Basin. It is probable that the Diamond Valley assemblage is a local expression of a vegetation type widespread in the ranges and basins of southwestern California during the middle Wisconsin. 相似文献
48.
49.
50.
Bergler Steffen Duveneck Eric Höcht German Zhang Yonghai Hubral Peter 《Studia Geophysica et Geodaetica》2002,46(2):165-175
The finite-offset (FO) common-reflection-surface (CRS) stack has been shown to be able to handle not only P-P or S-S but also arbitrarily converted reflections. It can provide different stack sections such as common-offset (CO), common-midpoint (CMP) and common-shot (CS) sections with significantly increased signal-to-noise ratio from the multi-coverage pre-stack seismic data in a data-driven way. It is our purpose in this paper to demonstrate the performance of the FO CRS stack on data involving converted waves in inhomogeneous layered media. In order to do this we apply the FO CRS stack for common-offset to a synthetic seismic data set involving P-P as well as P-S converted primary reflections. We show that the FO CRS stack yields convincing improvement of the image quality in the presence of noisy data and successfully extracts kinematic wavefield attributes useful for further analyses. The extracted emergence angle information is used to achieve a complete separation of the wavefield into its P-P and P-S wave components, given the FO CRS stacked horizontal and vertical component sections. 相似文献