全文获取类型
收费全文 | 93篇 |
免费 | 16篇 |
国内免费 | 17篇 |
专业分类
大气科学 | 3篇 |
地球物理 | 29篇 |
地质学 | 65篇 |
海洋学 | 6篇 |
天文学 | 14篇 |
综合类 | 2篇 |
自然地理 | 7篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 5篇 |
2012年 | 6篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 7篇 |
2006年 | 9篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有126条查询结果,搜索用时 15 毫秒
91.
The majority of geomorphological papers about Dartmoor have been essentially speculative, particularly when discussing weathering processes and the evolution of the Dartmoor landscape. In contrast, this article presents a synthesis of several experimental investigations aimed at studying the chemical weathering of Dartmoor granite through the systematic analysis of soil and water samples. This involved the computation of a geochemical budget to determine the amount of erosion in the catchment, as well as more detailed mineralogical investigations within a soil profile. The annual output of solutes due to weathering was 116 kg ha?1 a?1 of which the majority was silica (93 kg ha?1 a?1). From an examination of the soil mineralogy, it was calculated that these solutes were derived from the dissolution of approximately 200 kg ha?1 a?1 plagioclase, 90 kg ha?1 a?1 biotite, and 40 kg ha?1 a?1 orthoclase. As well as the weathering of granite, there was also the production of kaolinite (150 kg ha?1 a?1) and gibbsite (0.02 kg ha?1 a?1). Analysis of the soil water chemistry confirmed that kaolinite was the stable mineral phase in the regolith, although in areas where interflow was the dominant mode of water movement, the solute composition was in equilibrium with both kaolinite and gibbsite. Examination of the clay mineralogy confirmed these results. The microtexture of quartz grains was examined by the scanning electron microscope as another means of investigating the hydrochemical environment in the soil. Silica was found precipitated on all the grains examined but the maximum amount occurred in the Bs horizon. This evidence showed that, firstly, the dissolution of aluminosilicate minerals is greater than that calculated by the chemical budget and, secondly, that models of granite weathering must take localized weathering in the soil profile into account. The final part of the paper highlights the limitations of calculating denudation rates for an entire catchment and stresses the need to consider weathering as a highly localized phenomenon, particularly where there are high volumes of interflow at hill crest sites. Observations on granite decomposition in the future should be quantitative in approach and be related to the local site conditions. 相似文献
92.
93.
94.
Mahmoud Ghazavi 《Geotechnical and Geological Engineering》2004,22(3):401-416
Waste materials such as waste tires, rubbers, and plastic materials are normally produced in every society, entering the environment
and causing serious problems. These problems may be somehow reduced by finding applications for them in engineering, for example,
as lightweight materials for backfill in geotechnical projects. To this aim, this paper demonstrates how shear strength characteristics
of sand mixed with various percentages of waste garden hose grains are altered. A relatively, uniform sand has been mixed
with waste hose grains in loose and slightly compacted states. Waste hose grains were prepared with special popular machinery
in a local area. Various sand-rubber mixtures having 0%, 10%, 15%, 20%, 50%, 70%, and 100% waste hose particles by weight
were chosen. The rubber grains were distributed in the sand such that uniform mixtures are obtained. In order to compare the
shear strength of different sand-rubber samples, two compaction states were considered. The results show that the influencing
parameters on shear strength characteristics of sand-rubber mixtures are normal stress, mixture unit weight, and rubber content.
With the selected waste hose particles, compaction states, and rubber contents, the initial friction angle φ1 does not change significantly. However, an apparent cohesion appears in the mixtures. From environmental point of view and
due to lightweight material for the sand-waste hose particles, it may be useful to use such materials in corresponding geotechnical
projects.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
95.
Infrared stimulated luminescence (IRSL) and post-IR IRSL are applied to small aliquots and single grains to determine the equivalent dose (De) of eleven alluvial and fluvial sediment samples collected in the Pativilca valley, Central Peru at ca. 10°S latitude. Small aliquot De distributions are rather symmetric and display over-dispersion values between 15 and 46%. Small aliquot g-values range between 4 and 8% per decade for the IRSL and 1 and 2% per decade for the post-IR IRSL signal. The single grain De distributions are highly over-dispersed with some of them skewed to higher doses, implying partial bleaching; this is especially true for the post-IR IRSL. Measurements of a modern analog reveal that residuals due to partial bleaching are present in both the IRSL as well as the post-IR IRSL signal. The g-values of individual grains exhibit a wide range with high individual uncertainties and might contribute significantly to the spread of the single grain De values, at least for the IRSL data. Electron Microprobe Analysis performed on single grains reveal that a varying K-content can be excluded as the origin of over-dispersion. Final ages for the different approaches are calculated using the Central Age Model and the Minimum Age Model (MAM). The samples are grouped into well-beached, potentially well-bleached and partially bleached according to the evaluation of the single grain distributions and the agreement of age estimates between methods. The application of the MAM to the single grain data resulted in consistent age estimates for both the fading corrected IRSL and the post-IR IRSL ages, and suggests that both approaches are suitable for dating these samples. 相似文献
96.
对采自Faulty Towers(47°57.447'N,129°6.568'W)硫化物烟囱群一个不再活动的烟囱体硫化物开展了详细的矿物学和地球化学研究。样品从外壁往内壁方向可划分为4个矿物组合带,分别为重晶石-无定形硅-铁氧羟化物带;白铁矿-黄铁矿-无定形硅-重晶石带;白铁矿-黄铁矿-闪锌矿-纤锌矿带;纤锌矿-黄铜矿-白铁矿带。从底部到顶部,样品通道形态主要有3种:不规则、不连续的多通道;椭圆形单通道;封闭的通道。矿物学研究证实,烟囱体以低温矿物组合白铁矿、纤锌矿为主,高温矿物黄铜矿少见,仅局限分布在流体通道附近。210Pb定年结果表明,烟囱壁形成经历较短时间(约3 a),而通道的闭合则经历了相对长的过程(约17 a)。结合矿物学研究,最终恢复了整个尖塔结构的生长历史。 相似文献
97.
We report investigations of the optically stimulated luminescence (OSL) signals of sedimentary quartz from different regions of Asia, Africa, Europe and North America using a single-aliquot regenerative-dose (SAR) procedure. We show that variations in the shape of dose response curves (DRCs), or growth curves, of the test dose sensitivity-corrected OSL signals among single aliquots composed of multiple grains can be greatly reduced by normalising the DRCs using one of the regenerative dose OSL signals. We refer to this regenerative-dose normalisation procedure as ‘re-normalisation’. We find a common re-normalised DRC extends to doses of ∼250 Gy for samples that differ significantly in terms of geological provenance, sedimentary context and depositional age. This feature permits the development of a ‘global standardised growth curve’ (gSGC) for OSL signals from single aliquots of quartz. The equivalent dose (De) of an aliquot can be estimated from the natural signal, one regenerative dose signal and their corresponding test dose signals. For the variety of samples investigated, we find that De estimates obtained from the gSGC are consistent with those obtained using full SAR procedures for doses of up to ∼250 Gy. Use of the gSGC for single aliquots would greatly reduce the time required to estimate the De values of older samples and for a large number of aliquots. 相似文献
98.
This paper is a redevelopment result of liftoff rates of saltating sand grains based on our previous work.Aeolian sand flow is a complex multi-phase flow because of a special two-phase gas-solid flow near ground surface.Despite extensive research on the movement of blowing sand,no model fully characterizes aeolian sand flow,and large differences often exist between simulations of aeolian sand movement and field observations.One key problem is a few of sufficient research on liftoff rates of saltating sand g... 相似文献
99.
Ooid grainstone/packstone carbonate facies of the Dalan, Kangan, and Arab formations are the main hydrocarbon reservoirs in the Persian Gulf. Based on detailed petrographic and petrophysical analyses,sedimentological and mineralogical features of the Permian to Late Cretaceous carbonate and iron-rich coated grains from Zagros and the Persian Gulf were investigated. Frequent ooids in these formations indicate a high-energy environment and a wave-dominated shallow carbonate platform. Because of wi... 相似文献
100.
青岛近海魁蚶群体等位基因酶遗传变异研究 总被引:7,自引:1,他引:7
采用淀粉凝胶电泳技术研究了青岛近海魁蚶自然群体的等位基因酶遗传变异。在十种等位基因酶中共检测到了二十二个基因座位,多态位点比例为45.5%,位点有效等位基因数分布从1.000~2.469(平均值1.415),位点杂合度观察值分布为0.000~0.595(平均杂合度0.105±0.023),在六个基因座位上存在相当明显的杂合子缺失现象。文中讨论了杂合子缺失的原因。 相似文献