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191.
正As a kind of rare metals,rubidium is often used to prepare special glass,photomultiplier tubes,thermoelectric converter,organic catalysts and antidepressants.Rubidium forms no minerals of its own,hence,it often coexists with 相似文献
192.
正Massive nitrate deposits have been discovered in the Turpan-Hami basin in northwestern China.Previously,large ore grade nitrate minerals were thought only to exist in the Atacama Desert in northern Chile.Estimates of the 相似文献
193.
探讨了各种类型的表面活性剂对Sc-铜铁试剂体系的增敏效应;观察到在pH9.0的NH_4OH-NH_4Cl缓冲介质中,溴化十四烷基三甲铵使该体系催化波灵敏度提高了25倍。峰电位在-1.50V(us.Ag/AgCl),峰高与Sc浓度在2~40ng/ml呈线性关系,检出限1ng/ml;用拟定的方法测定了岩石样品中的痕量Sc;并对其极谱性质和表面活性剂增敏机理进行了探讨。 相似文献
194.
研究了用钼酸铵浸渍处理石墨管、石墨炉原子吸比法测定镓、铟和铊的最挂条件。实验证明,采用硝酸—氢氟酸—硫酸体系溶解样品,涂钼石墨管直接测定样品中的镓、铟和铊,能有效地避免它们在原子化之前以氧化物形式挥发的损失,减少了测定干扰,提高测定的灵敏度。对6个地质标样的测定结果是满意的。木法对镓、铟和铊的检测下限分别为0.9×10 ̄(-11)g,1.7×10 ̄(-11)g和6.2×10 ̄(-11)g;相对标准偏差分别为1.4%、4.8%和3.0%。 相似文献
195.
通过测定土壤中铵态氮和硝态氮的含量,能够为农业领域土壤精准施肥和土壤的环境保护提供重要参考。目前基于分光光度法的土壤中铵态氮和硝态氮的分析方法容易受到提取试液颜色、浑浊度、其他共存离子等干扰不能直接测定,必须进行脱色等前处理操作,费时耗力。因此,本文建立了一次性同时浸提,不经脱色处理,采用气相分子吸收光谱法测定农田土壤中铵态氮和硝态氮含量的方法。利用该方法测定农田土壤中铵态氮和硝态氮,避免了繁琐的显色反应过程,一个批次样品(50个)的分析流程仅需5h。在0.10~2.00mg/L(铵态氮)和0.20~4.00mg/L(硝态氮)浓度范围内,工作曲线线性良好;方法检出限分别为0.013mg/kg及0.002mg/kg;相对标准偏差(RSD)<1%;加标回收率为96.3%~100.7%。较之基于传统分光光度法的国家标准方法,本方法在检出限、精密度和回收率等指标方面均有显著改善,能够满足农田土壤中铵态氮和硝态氮的批量精准分析需求。 相似文献
196.
棕色碳是一类重要的吸光性有机气溶胶,对全球辐射强迫有重要贡献。其化学成分和形成机制是地球科学研究的前沿和难点。模拟实验结果表明,羰基化合物和还原性氮的液相反应产物在近紫外波段具有较强的吸光性,且化学成分复杂,难以分离和鉴定。本研究回顾了基于实验室羰基化合物和还原性氮的反应速率、反应机制,以及反应产物中吸光组分的化学成分和光学性质;总结了反应条件(反应物种类、浓度、溶液酸度、温度和相对湿度)对反应速率和吸光组分形成的影响;并指出了外场观测和模型研究对这一贡献认识的不足。 相似文献
197.
温度的变化能够改变水体的环境,引起周围环境中的离子吸附解吸作用的变化。不同于其他土壤,砂土的保水保肥能力更差,砂土地区一旦发生氨氮(NH4+-N)污染,情况会更加严重和突出。为防治砂土地区N H4+-N污染提供理论依据与技术支持,通过N H4+-N的静态吸附试验,研究不同温度条件下N H4+N在粗砂、中砂、细砂中的吸附转化特征,得到如下结论: 在试验设置的温度区间内,总的趋势是温度越低,砂土对N H4+-N的吸附量越高,表明温度升高对N H4+-N的吸附有抑制作用,这主要是因为吸附过程中会产生弱放热效应,进而降低渗滤介质对N H4+N的平衡吸附量; 在25~30 ℃区间内存在硝化与反硝化作用的临界温度,当温度低于临界温度时,N H4+-N吸附量的减少主要是由于发生了硝化反应,当温度高于临界温度时,N H4+-N的吸附量减少主要是由于发生了反硝化反应。 相似文献
198.
A laboratory incubation experiment was established to examine the impacts of nitrate and ammonium nitrogen additions on soil microbial attributes of a subtropical Pinus elliottii forest ecosystem in southern China. Soils were subjected to three different treatments: the control with no nitrogen addition (CK), the ammonium nitrogen addition (NH4+-N), and the nitrate nitrogen addition (NO3--N). Samples from bulk and two different size fractions (macroaggregate (>250 μm) and microaggregate (53-250 μm)) were analyzed for soil properties, enzyme activities and microbial communities on day 7 and 15 of the incubation. Our study demonstrated that NH4+-N had a greater influence on soil microbial activities than NO3--N. NH4+-N additions resulted in significant increases in β-1,4-glucosidase (βG) and β-1,4-N-acetyl glucosaminidase (NAG) enzyme activities in bulk, macroaggregate and microaggregate soils after 7 and 15 days incubation. NO3--N additions only significantly increased in βG and NAG enzyme activities in bulk, macroaggregate soils after 7 and 15 days incubation, but not in microaggregate. All NH4+-N and NO3--N additions resulted in significant increases in gram-positive bacterial PLFAs in microaggregates. Only a significant correlation between soil nutrient contents and enzyme activities in macroaggregates was founded, which suggests that the soil aggregation structure played an important role in the determining enzyme activities. 相似文献
199.
200.
In‐lake retention of inorganic nitrogen species (nitrate and ammonium) was estimated from mass balances in five acid‐sensitive lakes in southern Norway and eight in southern Ontario, Canada, to evaluate an empirical in‐lake N retention (RN) model. This model is included in the First‐order Acidity Balance (FAB) model, which currently is used for calculation of critical acid loads and exceedances in many countries. To estimate in‐lake RN, the FAB model uses a recommended mass transfer coefficient (SN) of 5 m year−1, which mainly is derived from NO3− mass balances in Canadian lakes. To date, the in‐lake RN model has not been evaluated for large parts of Europe. At the Norwegian study sites receiving the highest N deposition (>120 meq m−2 year−1) the net in‐lake retention of inorganic N (TIN) exceeded the corresponding terrestrial retention by a factor of 1·1–2·6. Despite differences in N loading and hydrology at the Norwegian and Canadian sites, both the mean mass transfer coefficients for NO3− (SNO3; 6·5 versus 5·6 m year−1) and TIN (STIN; 7·9 versus 7·0 m year−1) were of comparable magnitude. Both mean values and ranges of SNO3 suggest that the default SN value presently recommended for FAB model applications seems valid over a large range in N inputs and areal water loads (qs). However, owing to the relatively few data available for lakes with high qs values (15–150 m year−1), it is recommended that more lakes within this range be included in future studies to obtain a more precise prediction of in‐lake N retention over a wide qs gradient. Also, when considering that the FAB model treats all inorganic N leaching from a catchment as NO3−, it seems reasonable to use a default STIN value instead of just SNO3 when estimating in‐lake RN. In that case, the in‐lake RN presently calculated by the FAB model might be slightly underestimated. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献