全文获取类型
收费全文 | 155篇 |
免费 | 1篇 |
专业分类
大气科学 | 16篇 |
地球物理 | 20篇 |
地质学 | 63篇 |
海洋学 | 10篇 |
天文学 | 42篇 |
自然地理 | 5篇 |
出版年
2020年 | 2篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 3篇 |
2007年 | 9篇 |
2006年 | 9篇 |
2005年 | 6篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有156条查询结果,搜索用时 0 毫秒
91.
92.
93.
94.
95.
B. G. Katz 《水文研究》1989,3(2):185-202
During 1983 and 1984, wet precipitation was primarily a solution of dilute sulphuric acid, whereas calcium and bicarbonate were the major ions in springs and ground water in two small watersheds with a deciduous forest cover in central Maryland. Dominant ions in soil water were calcium, magnesium, and sulphate. The relative importance of mineral weathering reactions on the chemical composition of these subsurface waters was compared to the contribution from wet precipitation, biological processes, and road deicing salts. Mineral reaction models, developed from geochemical mass-balance relationships, involved reactions of primary and secondary minerals in metabasalt and metarhyolite with hydrogen ion. Geochemical weathering reactions account for the majority of total ion equivalents in soil water (46 per cent), springs (51 per cent), and ground water (68 to 77 per cent). The net contribution of total ion equivalents from biological processes was 20 and 16 per cent for soil water and springs, respectively, but less than 10 per cent for ground water. The contribution of total ion equivalents from deicing salts (10 to 20 per cent) was related to proximity to roads. Strong acids in precipitation contributed 44 per cent of the total amount of hydrogen ions involved in mineral-weathering reactions for ground water in contact with metarhyolite compared to 25 per cent for ground water in contact with metabasalt, a less resistant rock type to weathering. 相似文献
96.
97.
M.B. Katz 《Precambrian Research》1985,27(4):307-319
The Archaean—Proterozoic crust of many Precambrian terrains consists of two contrasting tectonic units: Archaean cratonic blocks made up of granite—greenstone terrains and Archaean—Proterozoic mobile zones, fold belts and orogens which separate and tend to surround and flow around the cratons. The cratons are relatively rigid blocks, but have a history of ductile and brittle deformations. The surrounding mobile belts are either high-strain, high-grade metamorphic belts or folded basins. Thus, the relatively rigid cratons are surrounded by more ductile zones of mobility. It is speculated that the Archaean cratons are originally separate, although neighbouring ensialic, polygonal miniplate blocks of a single continent which have moved relative to one another according to the mantle controls and the prevailing Eulerian poles, and this mutual jostling has progressively deformed their common boundaries. The deformed boundaries are now the sites of the surrounding ductile and higher strain mobile belts, which are persistent crustal defects, while the cratons represent the more rigid and lower strain cores and relicts, which have stabilized after the Archaean. The mega-scale relationships between the cratons and mobile belts (e.g., East Africa) are compared to the smaller scale micro—meso-scale porphyroclast-matrix structures found in augen gneisses and mylonites. These structural relationships are of vastly different magnitudes (108), but as there exists a continuum on all the intermediate scales they may all be related. Their geometric similarities are interpreted as having a common mechanical—rheological origin. 相似文献
98.
M. B. Katz 《Australian Journal of Earth Sciences》2013,60(1-2):247-248
A preliminary study of the host rock at the Harts Range ruby mine in the Arunta Block, central Australia, suggests that it is a layered anorthosite complex in contradiction of the metasedimentary, limestone‐terra rossa hypothesis of McColl & Warren (1979). The mineralogical, textural and structural evidence points to a meta‐igneous origin, and this compares well with other ruby‐bearing, Archaean, layered anorthosite complexes described from Greenland, India and elsewhere. This is the first report of a layered anorthosite in a high‐grade metamorphic terrain in the Australian Precambrian. 相似文献
99.
100.
The results of experiments on the hydrothermal dolomitization of calcite (between 252 and 295°C) and aragonite (at 252°C) by a 2 M CaCl2-MgCl2 aqueous solution are reported and discussed. Dolomitization of calcite proceeds via an intermediate high (ca. 35 mole %) magnesian calcite, whereas that of aragonite is carried out through the conversion of the reactant into a low (5.6 mole %) magnesian calcite which in turn transforms into a high (39.6 mole %) magnesian calcite. Both the intermediate phases and dolomite crystallize through a dissolution-precipitation reaction. The intermediate phases form under local equilibrium within a reaction zone surrounding the dissolving reactant grains. The volume of the reaction zone solution can be estimated from Sr2+ and Mg2+ partitioning equations. In the case of low magnesian calcite growing at the expense of aragonite at 252°C, the total volume of these zones is in the range of 2 × 10?5 to 2 × 10?4 1., out of 5 × 10?3 1., the volume of the bulk solution.The apparent activation energies for the initial crystallization of high magnesian calcite and dolomite are 48 and 49 kcal/mole, respectively.Calcite transforms completely into dolomite within 100 hr at 252°C. The overall reaction time is reduced to approximately 4 hr at 295°C. The transformation of aragonite to dolomite at 252°C occurs within 24 hr. The nature of the reactant dictates the relative rates of crystallization of the intermediate phases and dolomite. With calcite as reactant, dolomite growth is faster than that of magnesian calcite; this situation is reversed when aragonite is dolomitized.Coprecipitation of Sr2+ with dolomite is independent of temperature (within analytical error) between 252 and 295°C. Its partitioning, with respect to calcium, between dolomite and solution results in distribution coefficients in the range of 2.31 × 10?2 to 2.78 × 10?2. 相似文献