全文获取类型
收费全文 | 692篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 56篇 |
地球物理 | 166篇 |
地质学 | 271篇 |
海洋学 | 56篇 |
天文学 | 95篇 |
综合类 | 3篇 |
自然地理 | 54篇 |
出版年
2021年 | 7篇 |
2020年 | 7篇 |
2018年 | 11篇 |
2016年 | 12篇 |
2014年 | 17篇 |
2013年 | 25篇 |
2012年 | 20篇 |
2011年 | 20篇 |
2010年 | 13篇 |
2009年 | 29篇 |
2008年 | 30篇 |
2007年 | 24篇 |
2006年 | 32篇 |
2005年 | 24篇 |
2004年 | 25篇 |
2003年 | 15篇 |
2002年 | 23篇 |
2001年 | 19篇 |
2000年 | 8篇 |
1999年 | 14篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1972年 | 11篇 |
1970年 | 7篇 |
1968年 | 5篇 |
1964年 | 5篇 |
1959年 | 5篇 |
1955年 | 7篇 |
1954年 | 9篇 |
1952年 | 6篇 |
1950年 | 8篇 |
1948年 | 8篇 |
排序方式: 共有713条查询结果,搜索用时 15 毫秒
691.
692.
Karl Wolf 《Aquatic Sciences - Research Across Boundaries》1955,17(2):217-258
Ohne Zusammenfassung 相似文献
693.
Global changes in the marine environment and the continuing disposal of genotoxic xenobiotics are increasing the importance of environmental pollution monitoring and of biomonitoring programs. Current approaches focus on investigations at regional and local levels in an attempt to precisely define the nature and extent of any potential environmental crisis. We have initiated, for the first time, a long-term biomonitoring program focusing on the Croatian coast of the Adriatic Sea to contribute to a more detailed understanding of marine genotoxic effects using the mussels Mytilus galloprovincialis Lam., collected along the eastern Adriatic coast over a period of five years (1998-2002), as a key test organism. The integrity of DNA in its gill homogenate was examined by the Fast Micromethod. The strand scission factor (SSF) values, as a measure of DNA integrity, DNA damage or incomplete repair have been used for the ranking of sampling sites with respect to significant genotoxic stress due to the influence or effects of genotoxic xenobiotics. The region of Split (Kastela Bay) proved to be the area with the heaviest load of genotoxic agents. The investigation of harmful effects in the ecosystem based on biomonitoring of genetic and other agents, not only on local levels but also on a wider scale, is considered as an important step in marine environmental management. 相似文献
694.
695.
The Anglo-Australian Observatory 2dF facility 总被引:1,自引:0,他引:1
I. J. Lewis R. D. Cannon K. Taylor K. Glazebrook J. A. Bailey I. K. Baldry J. R. Barton T. J. Bridges G. B. Dalton T. J. Farrell P. M. Gray A. Lankshear C. McCowage I. R. Parry R. M. Sharples K. Shortridge G. A. Smith J. Stevenson J. O. Straede L. G. Waller J. D. Whittard J. K. Wilcox K. C. Willis 《Monthly notices of the Royal Astronomical Society》2002,333(2):279-299
696.
Matthew Colless Gavin Dalton Steve Maddox Will Sutherland Peder Norberg Shaun Cole Joss Bland-Hawthorn Terry Bridges Russell Cannon Chris Collins Warrick Couch Nicholas Cross Kathryn Deeley Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Darren Madgwick John A. Peacock Bruce A. Peterson Ian Price Mark Seaborne Keith Taylor 《Monthly notices of the Royal Astronomical Society》2001,328(4):1039-1063
697.
698.
The median values of the principal ionospheric quantities of the Venus dayside ionosphere are presented. The values are derived from the quantities measured by the Pioneer-Venus orbiter retarding potential analyzer over a period of two Earth yaers at solar cycle maximum. Quantities reported are total ion density, O+ density, O2+ density, sum density (NO+ + N2+ + CO+), CO2+ density, ion temperature, electron temperature, and plasma particle pressure. The data are organized to reveal altitude, solar zenith angle, solar longitude, and latitude dependences. The O+ density exhibits both a solar longitude and a latitude dependence which we suggest is caused by superrotation of the thermosphere and/or ionosphere. Asymmetry between the dawn and dusk terminator regions in the behavior of other quantities is also descibed. 相似文献
699.
Microscopic and spectroscopic studies were conducted to assess mineral transformation processes in aqueous suspensions of illite (Il), vermiculite (Vm) and montmorillonite (Mt) that were subjected to weathering in a simulated high-level radioactive tank waste leachate (0.05 m AlT, 2 m Na+, 1 m NO3−, pH ∼14, Cs+ and Sr2+ present as co-contaminants). Time series (0 to 369 d) experiments were conducted at 298 K, with initial [Cs]0 and [Sr]0 concentrations from 10−5 to 10− mol kg−. Incongruent clay dissolution resulted in an accumulation of secondary aluminosilicate precipitates identified as nitrate-sodalite, nitrate-cancrinite and zeolite X, by molecular spectroscopy and electron microscopy (XRD, IR, NMR, SEM-EDS and TEM-EDS). Contaminant fate was dependent on competing uptake to parent clays and weathering products. TEM-EDS results indicated that high Il affinity for Cs was due to adsorption at frayed edge sites. The Il system also comprised Sr-rich aluminous precipitates after 369 d reaction time. In Mt systems, Cs and Sr were co-precipitated into increasingly recalcitrant spheroidal precipitates over the course of the experiment, whereas contaminant association with montmorillonite platelets was less prevalent. In contrast, Cs and Sr were found in association with weathered Vm particles despite the formation of spheroidal aluminosilicate precipitates that were comparable to those formed from Mt dissolution. 相似文献
700.
Matt D. Anders Joel L. Pederson Tammy M. Rittenour Warren D. Sharp John C. Gosse Karl E. Karlstrom Laura J. Crossey Ronald J. Goble Lisa Stockli Guang Yang 《Quaternary Science Reviews》2005,24(23-24):2428-2448
We report new mapping, soils, survey, and geochronologic (luminescence, U-series, and cosmogenic-nuclide) data from Pleistocene deposits in the arid setting of eastern Grand Canyon. The result is a stratigraphic framework of inset fill gravels and associated terraces that provide a record of the responses of hillslopes, tributary streams, and the Colorado River to the last 400 kyr of glacial–interglacial climate change. The best-preserved last 80 kyr of this record indicates a stratigraphic–chronologic disconnect between both deposition and incision along the Colorado River versus along the trunks of local tributaries. For example, the Colorado River finished aggrading and had already begun incising before the main pulse of aggradation in the trunks of local catchments during Marine Isotope Stage 3, and then tributary incision followed during the millennial-scale fluctuations of the last glacial epoch, potentially concurrent with mainstem aggradation. The mainstem record appears to broadly correlate with regional paleoclimate and upstream geomorphic records and thus may be responding to climatic–hydrologic changes in its mountain headwaters, with aggradation beginning during full-glacial times and continuing into subsequent interglacials. The contrasting lag time in responses of the dryland catchments within Grand Canyon may be largely a function of the weathering-limited nature of hillslope sediment supply. 相似文献