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461.
湖泊沉积物氮磷内源负荷模拟 总被引:75,自引:1,他引:75
在对骆马湖沉积物及其间隙水物化性质、空间分布等分析基础上 ,在实验室控制的恒温静态条件下 ,模拟了软性富泥区柱状芯样在不同季节温度下的沉积物 水界面氮、磷交换过程。根据模拟不同温度下的柱状沉积物氮、磷释放速率及其代表时段下的物质释放量计算 ,以及应用孔隙水物质扩散模型进行的计算 ,全湖内源氮、磷负荷分别约为 ( 1 1 1 3.2± 71 .3)t/a和 ( 1 2 .5 0± 0 .95 )t/a,分别占骆马湖年氮、磷入湖量的 7.4%和 1 .2 %。沉积物中氮、磷含量差异大及铁含量较高可能是氮释放通量偏高和磷释放通量较小的主要因素。 相似文献
462.
近海沉积物中氮磷的生物地球化学研究进展 总被引:15,自引:0,他引:15
通过对国内外学者十几年来在近海沉积物氮磷地球化学方面研究工作的综述,阐明了该方面的最新进展。主要包括:沉积物中氮磷的形态及分布特点,各种形态间的分配关系,以及与氮磷迁移转化相关的循环过程。最后对该领域今后的发展方向进行展望。 相似文献
463.
条斑紫菜单细胞固体培养的初步研究 总被引:1,自引:0,他引:1
成熟条斑紫菜叶状体酶解后获得单细胞,分别培养于添加了不同浓度N,P营养盐的0.5%和10%的琼胶培养基上,观察细胞的分化发育情况。结果显示:(1)营养细胞大部分先发育为细胞团,细胞团放散孢子,再由孢子萌发形成小苗。其余营养细胞极性分裂形成正常细胞苗或带假根的形状不规则的片状体。孢子茁和营养细胞直接形成的幼苗生长到一定大小均可放散单孢子,单孢予能够正常萌发形成单孢子苗。(2)在0.5%的琼胶培养基上或较高浓度的营养盐中,细胞发育快。添加5mg/L NO3-N和0.5mg/L H2PO4—P营养盐不能满足细胞生长发育的需要,培育20d绝大部分仍为单细胞,不能形成正常幼苗。 相似文献
464.
There is great interest in modelling the export of nitrogen (N) and phosphorus (P) from agricultural fields because of ongoing challenges of eutrophication. However, the use of existing hydrochemistry models can be problematic in cold regions because models frequently employ incomplete or conceptually incorrect representations of the dominant cold regions hydrological processes and are overparameterized, often with insufficient data for validation. Here, a process‐based N model, WINTRA, which is coupled to a physically based cold regions hydrological model, was expanded to simulate P and account for overwinter soil nutrient biochemical cycling. An inverse modelling approach, using this model with consideration of parameter equifinality, was applied to an intensively monitored agricultural basin in Manitoba, Canada, to help identify the main climate, soil, and anthropogenic controls on nutrient export. Consistent with observations, the model results suggest that snow water equivalent, melt rate, snow cover depletion rate, and contributing area for run‐off generation determine the opportunity time and surface area for run‐off–soil interaction. These physical controls have not been addressed in existing models. Results also show that the time lag between the start of snowmelt and the arrival of peak nutrient concentration in run‐off increased with decreasing antecedent soil moisture content, highlighting potential implications of frozen soils on run‐off processes and hydrochemistry. The simulations showed TDP concentration peaks generally arriving earlier than NO3 but also decreasing faster afterwards, which suggests a significant contribution of plant residue Total dissolved Phosphorus (TDP) to early snowmelt run‐off. Antecedent fall tillage and fertilizer application increased TDP concentrations in spring snowmelt run‐off but did not consistently affect NO3 run‐off. In this case, the antecedent soil moisture content seemed to have had a dominant effect on overwinter soil N biogeochemical processes such as mineralization, which are often ignored in models. This work demonstrates both the need for better representation of cold regions processes in hydrochemical models and the model improvements that are possible if these are included. 相似文献
465.
466.
Response of Reactive Phosphorus Burial to the Sedimentary Transition from Cretaceous Black Shales to Oceanic Red Beds in Southern Tibet
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The mechanism of sedimentary transition from the Cretaceous black shales to the oceanic red beds is a new and important direction of Cretaceous research. Chemical sequential extraction is applied to study the burial records of reactive phosphorus in the black shale of the Gyabula Formation and oceanic red beds of the Chuangde Formation, Southern Tibet. Results indicate that the principal reactive phosphorus species is the authigenic and carbonate-associated phosphorus (CaP) in the Gyabula Formation and iron oxides-associated phosphorus (FeP) in the Chuangde Formation which accounts for more than half of their own total phosphorus content. While the authigenic and carbonate-associated phosphorus (CaP) is almost equal in the two Formations; the iron oxides-associated phosphorus is about 1.6 times higher in the Chuangde Formation than that in the Gyabula Formation resulting in a higher content of the total phosphorus in the Chuangde Formation. According to the observations on the marine phosphorus cycle in Modern Ocean, it is found that preferential burial and regeneration of reactive phosphorus corresponds to highly oxic and reducing conditions, respectively, leading to the different distribution of phosphorus in these two distinct type of marine sediments. It is the redox-sensitive behavior of phosphorus cycle to the different redox conditions in the ocean and the controlling effects of phosphorus to the marine production that stimulate the local sedimentary transition from the Cretaceous black shale to the oceanic red beds. 相似文献
467.
以上海市的枫泾镇(FJ)、松江新城(SJ)和朱家角镇(ZJJ)为例,研究了小城镇街道灰尘中氮磷的含量水平和分布特征,结果表明:小城镇街道灰尘中总无机氮的含量为11.9-1040.6μg/g,平均含量为117.5.μg/g;可溶磷的含量为15.8~65.8μg/g,平均含量为48.7μg/g;各小城镇街道灰尘中的氮磷含量表现为:FJ>ZJJ>SJ.各小城镇街道灰尘中氮磷含量的空同分布差异较大,位于城镇中心和风景区内采样点的氮磷含量明显较高,而城镇周边乡村地区含量较低.对各小城镇街道灰尘氮磷含量的季节变化分析表明,秋季小城镇街道灰尘中氮磷的含量明显高于冬季和夏季,温度、降雨量可能是其季节变化的主要影响因子. 相似文献
468.
Kunchithapadam Gopalan J. Douglas Macdougall Christopher Macisaac 《Geostandards and Geoanalytical Research》2007,31(3):227-236
For studies of mass-dependent fractionation of calcium isotopes in natural materials, the 48 Ca/42 Ca ratio is a superior choice to the conventionally measured 44 Ca/40 Ca ratio for two important reasons. These are (1) mass-dependent fractionation can be determined free from the effects of inherited or ingrown radiogenic 40 Ca and (2) this ratio increases the spread of measured isotopic masses by 50%, resulting in statistically better resolution of fractionation, assuming similar precision. A third, though strictly technical, advantage is the inherent ability of a mass spectrometer to measure ratios close to unity (48 Ca/42 Ca) more precisely than very small or large ratios (44 Ca/40 Ca). However, because of the very low natural abundance of both 48 Ca and 42 Ca, their ratio has been very difficult to measure, the only attempt so far being on a high mass resolution MC-ICP-MS with a precision of 0.33%. We report here determination of the 48 Ca/42 Ca ratio by the more commonly available and user-friendly multi-collector TIMS using a 43 Ca-46 Ca double-spike, with a significantly better precision of 0.18% (2s). The 48 Ca/40 Ca or 44 Ca/40 Ca ratio can also be measured in the same mass spectrometer run to provide complementary information on any radiogenic component. 相似文献
469.
Compared with the oceanic crust, knowledge about the formation of the continental crust (CC) is relatively poor. Although melting of subducted slabs in the early history of the Earth has been considered as the major way that shaped the chemical characteristics of the CC by most geologists, as the CC shares many characteristics with modern adakites, some geologists argued that Archean TTG was formed in the same way as modern arcs rather than slab melting, whereas others proposed that melting at the bottom of the thickened oceanic crust was more important. Recently,the debate is mainly focused on the unique subchondritic Nb/Ta value of the CC, and particularly, how Nb and Ta fractionated from each other and consequently how, in detail, the CC was built. 相似文献
470.
CHEN Chuanping MEI Bowen & CAO Yacheng . Jianghan Petroleum University Jingzhou China . Huazhong University of Science Technology Wuhan China . Nanjing Institute of Soil Science Chinese Academy of Sciences Nanjing China 《中国科学D辑(英文版)》2005,48(8):1211-1219
Nitrogen occupies a high content in crust and in atmospheric circle. It is one of the main elements in organism and an important element in sedimentary circle. Although nitrogen is little in crude oil, to a cer-tain degree, it influences the physical and chemical properties of oil, such as viscosity and density[1]. In reservoir the nitrogen-bearing compounds can form ion bonds or hydrogen bonds with substances on rock and form van der Vaals’ force among moleculae so they affect and alter the … 相似文献