首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   140篇
  免费   23篇
  国内免费   29篇
测绘学   1篇
地球物理   55篇
地质学   105篇
海洋学   10篇
天文学   1篇
综合类   9篇
自然地理   11篇
  2022年   3篇
  2021年   8篇
  2020年   7篇
  2019年   5篇
  2018年   5篇
  2017年   8篇
  2016年   4篇
  2015年   9篇
  2014年   9篇
  2013年   16篇
  2012年   3篇
  2011年   7篇
  2010年   9篇
  2009年   9篇
  2008年   12篇
  2007年   9篇
  2006年   10篇
  2005年   8篇
  2004年   4篇
  2003年   4篇
  2002年   9篇
  2001年   5篇
  2000年   4篇
  1999年   3篇
  1998年   4篇
  1996年   5篇
  1994年   3篇
  1993年   4篇
  1992年   4篇
  1990年   1篇
  1973年   1篇
排序方式: 共有192条查询结果,搜索用时 15 毫秒
51.
对山西4口水化学观测井(泉)及周边地表水进行水化学和氢氧同位素分析,利用Piper图、durov图、Na-K-Mg三角图等方法研究其水化学特征及成因,得出井(泉)水岩平衡程度、热储温度、地下水循环深度及地下水补给来源详情;分析了井(泉)水氡测项映震特征,应用水氡映震效果与水岩平衡程度、地下水循环深度表现出的特征,评价了地震监测效能。评价结果显示夏县井、奇村井优于临猗井,适于开展地震水化学观测;定襄泉应用该水化学方法评价尚存不足之处,需要探索适用于该类观测泉点的物理与化学相结合的评价方法。  相似文献   
52.
洪范池铁矿体赋存于太古宙泰山岩群山草峪组,矿体周围泉水众多,论证矿床开采疏排水能否对泉水产生影响具有重要意义。研究分析表明,朱砂洞组含水层及山草峪组风氧化带裂隙水是矿床充水的直接充水水源,矿床充水水文地质条件属简单类型。泉水出露于寒武纪张夏组含水层中,并且与山草峪组含水层间无水力联系。若张夏组含水层不与采区沟通,矿山生产疏排水不会对泉水产生明显的影响。  相似文献   
53.
Microbes are believed to play important roles in ecosystem function in many environments. The hot springs of Xiamen Island are close to the Xiamen Sea, and may have some characteristics different from those of inland hot springs. Microbes living in the hot springs of Xiamen may have new characteristics. However, little is known about microbial communities of hot springs close to the Xiamen Sea. A cuhure-dependent survey of microbial population in the Xiamen hot springs was pcrformed by using an approach combining total cellular protein profile identification and 16S rRNA gene sequencing. A total of 328 isolates of bacteria were obtained from liquid and sediment samples from the Xiamen hot springs, including neutrophilie thermophilic bacteria and moderately thermophilic acidophiles. Neutrophilic thermophilic bacteria, which grow at a temperature range of 55-90℃ including Rhodothermus marinus (Strain 1) , Thermus thermophilus (Strain 2), Thermus thiopara (Strain 3) , Geobacillus stearothermophilus(Strain 4) , Geobacillus thermoleovorans (Strain 5) , and Pseudomonas pseudoal-caligenes (Strain 6), were recovered by 2216E plates. Moderately thermophilic acidophiles, which can grow at temperatures above 50℃ and a pH range of 1. 8-3.5 such as Alicyclobacillus acidoterrestris (Strain 8) , Sul-fobacillus acidophilus (Strain 9), and Sulfobacillus thermosulfidooxidans (Strain 10), were isolated on selective solid medium containing sulfur and Fe2+. Among these strains, Rhodothermus marinus, Thermus thermophilus and Geobacillus stearothermophilus are not only thermophilcs, but also halophiles. One bacterium strain (Strain 6) shared 99% nucleotide sequence homology with Pseudomonas pseudoalcaligenes on the 16S rRNA gene se-quence, but was quite different from Pseudomonas pseudoalcaligenes in biological characteristics, suggesting that it may represent a novel thermophilic species. Results indicated that various species of neutrophilic thermophiles and moderately thermophilic acidophiles were widely distributed in the Xiamen hot springs and that Rhodother-mus marinus and Thermus thermophilus dominated the cultivable microbial community.  相似文献   
54.
Barite occurrences related to the Cenozoic (Late Alpine) low-temperature hydrothermal activity are present in the continental Ohře (Eger) Rift area. A specific, Ra-bearing type of barite has been known under the name “radiobarite” from this area since 1904. Revision of 12 localities revealed the presence of alleged radiobarite only in the Teplice (Lahošť–Jeníkov) and Karlovy Vary areas. Barite from other localities is radium-poor. Barite crystals showing concentric oscillation colour zoning totally prevail. Isomorphous substitution of Sr (X×10−1 to X×wt%), Ca (X×10−2 wt%) and Fe (X×10−1 wt%) for Ba was proved. Average SrO contents of 0.4 wt% are markedly exceeded in some samples from Lahošť–Jeníkov (max. 3.2 wt%) and Karlovy Vary (max. 4.9 wt%). Besides inclusions of stoichiometric iron disulphide, the same samples also contain iron disulphides with unusual high contents of Co (max. 12.2 wt%) and Ni (max. to 8.4 wt%). Specific activity of 238U in the studied barites is very low while that of 226Ra reaches 8 Bq/g in several samples. Therefore, 226Ra is not in equilibrium with its parent uranium. These “radiobarites” or their parts must be therefore relatively young, not older than 10–15 ka. Very low uranium contents (<0.4 ppm) were also confirmed by neutron activation analyses of barite samples.

Unit-cell dimensions refined from X-ray powder diffraction data do not show any systematic variation with the measured chemical composition. Their values agree with the data given in the literature. Reflection half-widths, however, seem to correlate with chemistry. Peaks are wider in samples from Lahošť–Jeníkov and Karlovy Vary.

Sulphur and oxygen stable isotope compositions of the Cenozoic barite mineralization of Teplice area are very uniform (δ34S values between 3.9‰ and 7.1‰ CDT, and δ18O values between 6.1‰ and 7.7‰ SMOW), while the barites of Děc˘ín area show more variable sulphur sources. Sulphate derived from sediments of the Tertiary Most Basin seems to dominate for the Teplice area, while Cretaceous sediments are a more probable sulphur source in the Děc˘ín area. Calculation of oxygen isotope composition of hydrothermal fluids based on fluid inclusion homogenization temperatures and barite δ18O data shows δ18Ofluid values in the range of meteoric waters or δ18O – shifted deep circulating meteoric or basinal waters.  相似文献   

55.
The recharge altitude estimation of thermal springs from northern and eastern Morocco using 18O and 2H contents requires the definition of regional isotopic altitudinal gradients (?0.25‰ for 100 m for the Rif and ?0.30‰ for the East) and the calculation of residence time using 14C. The altitudes of emergence vary widely between 170 and 1040 m under the altitude of the recharge areas. The 18O and 2H compositions of palaeowaters (>10000 yr BP) indicate two effects, altitude and palaeoclimate. To cite this article: A. Winckel et al., C. R. Geoscience 334 (2002) 469–474.  相似文献   
56.
郯庐断裂带温泉气体地球化学   总被引:3,自引:0,他引:3  
断裂构造带温气体成分及同位素组成特征直接指示断裂带的构造活动及水化学特征。郯庐断裂带温泉气体成分以N2为主(多数大于90%),CO2含量较低(多数小于1%)。δCco2在南北不同地段存在明显差异,北段为-5.8‰--7.8‰,CO2主要为岩石化学成因。而中段和南段δ^13Cco2均小于-10‰,CO2有机成因。^40Ar/^36Ar为295-363,其中较低者(300左右)主要来源于大气,较高者来自地壳岩石中^40K的衰变。本文研究成果不仅有助于探讨断裂带不同地段温泉气体的组成及其来源,而且有助于揭示郯庐断裂带构造-岩浆活动及水文地球化学特征。  相似文献   
57.
Recent studies have focused on the relationship between solute concentrations and discharge in streams, demonstrating that concentrations can vary little relative to changes in discharge (chemostatic behaviour). Chemostatic behaviour is dependent on catchment characteristics (e.g., lithology, geomorphology, and vegetation) and chemical characteristics of the solute (e.g., availability, reactivity, and mobility). An investigation of 3 springs and a stream near Los Alamos, NM, reveals that springs can behave in a chemostatic fashion as stream systems tend to do. Another unique finding of this study is that the anthropogenic contaminants barium and the high explosive RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine) can also behave chemostatically. The chemostatic behaviour of a contaminant has important implications for the residence time of contaminants in a system as well as having a major control on contaminant flux and mass transport. Redox (reduction–oxidation) and biogeochemically sensitive analytes (e.g., Fe, SO4, and NO3) display a combination of chemostatic and chemodynamic behaviour, showing the influence of temporally variable conditions on stream and spring chemistries.  相似文献   
58.
Despite its location in the rain shadow of the southern Sierra Nevada, the Panamint Range hosts a complex mountain groundwater system supporting numerous springs which have cultural, historical, and ecological importance. The sources of recharge that support these quintessential desert springs remain poorly quantified since very little hydrogeological research has been completed in the Panamint Range. Here we address the following questions: (i) what is the primary source of recharge that supports springs in the Panamint Range (snowmelt or rainfall), (ii) where is the recharge occurring (mountain-block, mountain-front, or mountain-system) and (iii) how much recharge occurs in the Panamint Range? We answer questions (i) and (ii) using stable isotopes measured in spring waters and precipitation, and question (iii) using a chloride mass-balance approach which is compared to a derivation of the Maxey–Eakin equation. Our dataset of the stable isotopic composition (δ18O and δ2H) of precipitation is short (1.5 years), but analyses on spring water samples indicate that high-elevation snowmelt is the dominant source of recharge for these springs, accounting for 57 (±9) to 79 (±12) percent of recharge. Recharge from rainfall is small but not insignificant. Mountain-block recharge is the dominant recharge mechanism. However, two basin springs emerging along the western mountain-front of the Panamint Range in Panamint Valley appear to be supported by mountain-front and mountain-system recharge, while Tule Spring (a basin spring emerging at the terminus of the bajada on the eastern side of the Panamint Range) appears to be supported by mountain-front recharge. Calculated recharge rates range from 19 mm year−1 (elevations < 1000 mrsl) to 388 mm year−1 (elevations > 1000 mrsl). The average annual recharge is approximately 91 mm year−1 (equivalent to 19.4 percent of total annual precipitation). We infer that the springs in the Panamint Range (and their associated ecosystems) are extremely vulnerable to changes in snow cover associated with climate change. They are heavily dependent on snowmelt recharge from a relatively thin annual snowpack. These findings have important implications for the vulnerability of desert springs worldwide.  相似文献   
59.
长白山火山区温泉温室气体排放通量研究   总被引:4,自引:3,他引:1  
温泉是深部岩浆活动在地表的直接表现,并且向大气圈排放大量的温室气体.然而,国内尚无火山区温泉排放的温室气体通量研究报道.我国长白山火山区水热活动强烈,主要有湖滨温泉带、聚龙温泉群、锦江温泉以及火山口外围的十八道沟温泉.本文利用数字皂膜流量计测量温泉气体排放通量,并结合前人对长白山火山区温泉气体成分的研究成果,估算了研究区温泉所排放的温室气体通量.结果表明,长白山火山区温泉排放的CO2通量为6.9×104t·a-1,CH4排放通量为428.44t·a-1,与意大利Pantelleria Island火山区温泉排放的温室气体通量规模相当.本文的测试结果表明:数字皂膜流量计在火山区温室气体排放通量估算研究中的应用是可行的.  相似文献   
60.
搭格架温泉水化学特征及其约束因素研究   总被引:1,自引:0,他引:1  
搭格架地热区温泉水DJ1-DJ116号样品于2009年采集,阳离子及微量元素含量采用ICP-OES法测试,Cl-含量采用滴定法测试,其余阴离子含量采用紫外-可见光分光光度法测试。通过对温泉水化学指标的分析,研究温泉的水化学特征及约束因素。其温泉水化学类型为HCO3-Na型,平均矿化度为1 524 mg/L,具有较高的Na/Cl值,温泉水演化程度较高,为完全平衡水,热储中的水岩反应达到了平衡状态.温泉水中PO2极低,PCO2较高;大部分温泉水中玉髓、石英和无定形态SiO2三种硅质热液矿物的饱和度指数大于0。K-Na温标计算热储平均平衡温度为251.36℃;泉水中的Na+、K+离子活度主要受到钠、钾长石的约束。微量元素组合表现出花岗岩源的特征。总体上搭格架地热区温泉水化学特征受到区域地质背景的约束。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号