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991.
992.
沉积物-水界面的生物地球化学作用 总被引:18,自引:0,他引:18
沉积物-水界面是天然水体在物理、化学和生物特征等方面差异性最显著和负责水体和沉积物之间物质输送和交换的重要边界环境。对沉积物-水界面生物地球化学的定义、研究方法和它在水体微量物质循环中所起的作用、物质迁移方式、典型氧化还原敏感性元素转化反应(C、O、N)、界面扩散通量和表面扩散亚层的意义和估算等进行了讨论。 相似文献
993.
太湖水体生态环境历史演变 总被引:57,自引:15,他引:57
根据1950 ̄1995年期间对太湖水体进行的各次综合性研究结果分析:太湖水质和营养程度大致每10 ̄15年上升一个级别,近期变化尤为明显CODMn含量35年来增加了136%,总磷近年来以9.9%速度上升,浮游藻类80年代以来一直以蓝藻和硅藻占优势,但种群数趋于减少,细胞数据增,局部水域蓝藻水华频发;浮游动物和底栖动物中耐污染类增多,枝角类、桡足类和环节动物、节肢动物数量则降低;鱼类种群数减少,银鱼捕 相似文献
994.
浅型富营养湖泊的生态恢复——五里湖水生植被重建实验 总被引:26,自引:4,他引:26
依据浅型湖泊生态系统的多稳定态理论,在富营养湖泊治理过程中,当外来污染得到有效控制时,通过人工重建水生植被可以加速湖泊的生态恢复。在五里湖中,挺水植物和浮叶植物都能很好地生长,水底光照不足是沉水植物难以生长的主要原因。在自然条件下建成了永久性挺水植物群落和浮叶植物群落,在人工控制的围隔环境中改善了水底光照条件,建成了沉水植物群落。但这些沉水植物仍不能渡过夏季,主要原因是湖水过深和水温较高,降低水位和建造人工浅滩可为五里湖沉水植被恢复创造有利条件。本研究可为富营养水体的水质控制和植被恢复提供多种实用技术,但在水生植被的结构与环境功能等方面仍需开展深入的定量研究。 相似文献
995.
花岗岩裂隙水推荐配方稳定性模拟研究 总被引:1,自引:0,他引:1
在核废物深部地质处理科学过程中,提供一种长期稳定的模拟花岗岩裂隙,用以模拟试验是非常有必要的。本文主要依照中国辐射防护研究院推荐的模拟花岗岩裂隙水修正配方,引用地球化学模式程序对其溶液的稳定性进行模拟计算,探讨配方中所存在的问题。 相似文献
996.
It is necessary to understand the aquatic chemical characterstics of natural surface fresh water for water quality assessment.The chemical data from different kinds of water in the central Guizhou karst area showd that spring water from carbonate rock cracks(crack-water)is of neutrality or meta-alkalinity and [C] Ca II type.The amounts of all ions and the concentrations of HCO3^- and Ca^2 were higher in the autumn than in the spring,The crack-water was influenced by the infiltration of surface water in the process of erosion and /or trans-portation with decreasing HCO3 and increasing pH,SO4^2-,Cl^-,K^ and Na^ during running in a certain distance on the land surface .In particular,the chemical compositions of the waters at Tianxingqiao(upper-stream),Shuiliandong(mid-waterfall)and Luoshuitan(down-pool)near the Huangguoshu Waterfall were much different from those of the crack-water.The concentration of SO4^2-,Na^ ,Fe^3 and NO3^- varied closely with seasons.The CaCO3 deposited violently with CO2 release in the spring ,In Lake Hongfeng the HCO3^-/SO4^2- equivalent ratios were only 2.1-2.4 ,but Ca^2 /Mg^2 up to 2.4-4.2.The Cl^- concentration increased by a factor of 1 and Na^ by order of magnitude relative to the spring water.These indicated the increase in artificial pollutant discharge in the Lake Hongfeng watershed.In addition,Proewater in the soils covering carbonate rocks belongs to strongly mineralized water,The obvious differences in water quality were controlled by carbonate deposition,sulphate mineralization and nitrogen fixation as well as ammonification.It is indicated thaty the chemical compositions in the waters from the karst region were unstable and changeable. 相似文献
997.
998.
Precipitation of dolomite using sulphate-reducing bacteria from the Coorong Region, South Australia: significance and implications 总被引:9,自引:0,他引:9
Dolomite was successfully precipitated in culture experiments that simulated microbiogeochemical conditions prevailing during late stages of evaporation in ephemeral, hypersaline dolomitic lakes of the Coorong region, South Australia. Analyses of lake- and pore-water samples document rapid geochemical changes with time and depth in both dolomitic and non-dolomitic lakes. Extremely high sulphate and magnesium ion concentrations in lake waters decline rapidly with depth in pore waters throughout the sulphate-reduction zone, whereas carbonate concentrations in pore waters reach levels up to 100 times those of normal sea water. Ultimately, sulphate is totally consumed and no solid sulphate is recorded in the dolomitic lake sediments. ‘Most probable number’ calculations of lake sediment samples record the presence of large populations of sulphate-reducing bacteria, whereas sulphur-isotope analyses of lake-water samples indicate microbial fractionation in all the lakes studied. Viable populations of microbes from the lake sediments were cultured in anoxic conditions in the laboratory. Samples were then injected into vials containing sterilized clastic or carbonate grains, or glass beads, immersed in a solution that simulated the lake water. Falls in the levels of sulphate and rising pH in positive vials were interpreted as indicating active bacterial sulphate reduction accompanied by increased concentrations of carbonate. Within 2 months, sub-spherical, sub-micron-size crystals of dolomite identical to those of lake sediments were precipitated. It is concluded that bacterial sulphate reduction overcomes kinetic constraints on dolomite formation by removing sulphate and releasing magnesium and calcium ions from neutral ion pairs, and by generating elevated carbonate concentrations, in a hypersaline, strongly electrolytic solution. The results demonstrate that bacterial sulphate reduction controls dolomite precipitation in both the laboratory experiments and lake sediments. It is proposed that dolomite formation, through bacterial sulphate reduction, provides a process analogue applicable to thick platformal dolostones of the past, where benthic microbial communities were the sole or dominant colonizers of shallow marine environments. 相似文献
999.
1000.
扎龙湿地水环境与可持续发展 总被引:11,自引:2,他引:11
扎龙湿地水环境污染较重,主要表现为水体有机污染和富营养化,总氮、总磷、高锰酸盐指数超标率达100%。水质与水生生物评价结果表明,湿地水环境处于中、重度污染程度;其污染原因是生活污水、工业废水的排放和农药、化肥的施用等。扎龙湿地补给水量不足,年缺水约3亿m3,是扎龙湿地生存和发展的最突出隐患。从可持续发展的角度出发,提出了开展湿地宣传教育活动,建立科学的资源与环境生态水利体系,建立湿地水文监测系统等5条措施。 相似文献