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排序方式: 共有232条查询结果,搜索用时 218 毫秒
171.
Geophysical surveys were carried out in an arsenic contaminated area, in the Ron Phibun District in southern Thailand. Here, tin and associated minerals, i.e. arsenopyrite and pyrite, have been extracted from granites and natural processes and the mining activities led to arsenic contamination in the environment. Electrical resistivity and self-potential (SP) were used to define the distribution of arsenic contamination in the groundwater. Resistivities of 25–100 Ωm and a positive SP anomaly of 66.0 mV were observed in an area where the arsenic content in auger water at 3.5–5.0 m depths was high, 0.5–5.0 mg/l. Integrated interpretation of resistivity, seismic refraction, GPR and gravity data gave a clear image of subsurface shallow structures (< 30 m depths). There was a good correlation between the resistivity and the gravity data. A subsurface rise was found, which possibly acts as a naturally buried dam, separating a high-contaminated area from a low contaminated area. 相似文献
172.
顾及交通时态属性的最优路径算法与实现 总被引:5,自引:0,他引:5
GIS软件中最优路径分析多不考虑交通时态属性信息,而是将交通网抽象为理想化的、纯数学上的点一线网络“图”结构,导致结果与实际不符,实用性较差。文中结合交通时态属性信息,探讨一种实用的快速计算最优路径的模式和方法。 相似文献
173.
Direct and indirect methods for groundwater investigations: A case-study of MRS and VES in the southern part of Sweden 总被引:1,自引:0,他引:1
Magnetic Resonance Sounding (MRS) has been successfully tested for detecting groundwater in two areas in southern Sweden. Measurements of Schlumberger VES have been conducted in the same place as the MRS and the results are generally consistent. Low resistivity layers interpreted as clay are sometimes identified close to the surface. The MRS result in site 2 is a good example of signals penetrating through the clay and deeper aquifer still being detected. The MRS data suggest aquifers that are not only hosted in soft sediment materials (moraine, sand, and mixed materials), but hosted in basement rocks. Based on the MRS and borehole pumping test data, the results agree with yield, average water content and subsurface geological data. 相似文献
174.
作物水分利用效率是评价农业用水效率的重要指标,由于气候差异,采用作物水分利用效率评价不同区域的用水效率可能存在一定误差,尚缺乏深入研究。基于潜在水分利用效率指标和气象数据,计算了2014年中国小麦、玉米和水稻在充分灌溉条件下的潜在水分利用效率,分析了区域气候差异对作物水分利用效率的影响,提出了相对水分利用效率和理论节水潜力的概念和计算方法,并进行了实例研究。结果表明:各类作物在不同站点的潜在水分利用效率的标准差为0.49~1.01 kg/m3,多数作物潜在水分利用效率的空间差异大于实际水分利用效率的空间差异;主要作物的平均相对水分利用效率为50.7%,其理论节水潜力为884.8~4 064.5 m3/hm2;作物水分利用效率和广义节水潜力指标可能高估或低估作物的用水效率和节水潜力。研究认为在比较区域间作物的水分利用效率时不能忽略气候差异的影响;由于考虑了区域气候差异,相对水分利用效率和理论节水潜力指标更合理。 相似文献
175.
176.
ke V. Rosn Beda A. Hofmann Moritz von Sivers Marc Schumann 《Meteoritics & planetary science》2020,55(1):149-163
Radionuclide activities were measured in the low‐background gamma‐ray spectrometry facility GeMSE in eight meteorite falls (Lost City, Tamdakht, Huaxi, Boumdeid, Xining, Kamargaon, Degtevo, and Ouidiyat Sbaa) and two finds (SaU 606 and Mürtschenstock) to evaluate the use of radionuclides for terrestrial age estimates. Results indicate that these meteorites were all derived from small‐ (r < 25 cm) to medium‐sized (r < 65 cm) meteoroids. Short‐lived 48V (t1/2 = 16.0 d) and 51Cr (t1/2 = 27.7 d) were only detected in Oudiyat Sbaa (EH), while 7Be (t1/2 = 53.1 d) was also detected in Degtevo (H) and Kamargaon (L), in agreement with reported fall dates. The 22Na/26Al activity ratio in Huaxi agrees with the previously reported short cosmic‐ray exposure age of this meteorite while 22Na/26Al in Kamargaon likely records a complex exposure history. Bayesian statistical analysis verifies the detection of very low activities of 44Ti (t1/2 = 60 a) in the relatively large H chondrites (>100 g) Degtevo, Huaxi, Tamdakht, Lost City, and SaU 606. Additionally, large samples from Oudiyat Sbaa (EH) and Kamargaon (L) gave positive detections. For H chondrite target compositions, detected 44Ti(Fe+Ni)/26Al averaged 0.055 ± 0.013. Activities of 22Na and 54Mn in SaU 606 show that this meteorite fell between July and September 2012, making SaU 606 the second recent fall from Oman identified using gamma‐ray spectrometry. The upper activity limit of 22Na in the Mürtschenstock meteorite shows that it fell prior to 1999 and is not related to a bolide observation in 2015. Mürtschenstock shows 137Cs ~10× higher than previously determined in Oman meteorites, likely due to Chernobyl fallout. 相似文献
177.
分流河道特征及其识别方法:以东营凹陷东部地区为例 总被引:9,自引:0,他引:9
东营凹陷东部地区分流河道沉积物以砂岩,粉砂岩为主,夹泥岩薄层,分选性较好,砂岩层理发育,横剖面上分流河道顶平底凸的透镜状,在平面上呈树枝形的扇状分布,分流河道的储集体主要有心滩和边滩交错叠置构成,厚度一般为2-10m,分流河道储集体的测井相特征在自然电位曲线上反映明显,可以划分为光滑柱状,齿形柱状,齿形漏斗状-齿形钟状和光滑卵状,分别代表河道中心,中心偏边部,接近边部及河道边部,分流河道储集体在地震反射外形呈透镜状,地震反射连续性差,中振幅,上超充填特征明显。 相似文献
178.
东天山土屋特大型斑岩铜矿成矿地质特征与矿床对比 总被引:24,自引:1,他引:24
土屋特大型斑岩铜矿位于东天山吐鲁番-哈密陆块南部边缘岛弧环境中。多期岩浆活动和矿化是铜金属超常堆集的主要因素。海底火山活动和热泉沸腾逸散造就了铜金属的预富集(矿源层),闪长玢岩和斜长花岗斑岩的侵位和叠加矿化使铜金属进一步富化和最终成矿,以细碧角斑质为主的火山岩喷发于潮坪-滨海环境,闪长玢岩、斜长花岗斑岩形成于较强的氧化环境;强还原示踪矿物黄铁矿含量较少。矿石的低品位、矿石的结构构造、蚀变特征以及矿石建造具典型斑岩矿床特征;矿石高品位、矿床形成较低温度及大量硅化蚀变又表现为某些热液矿床特征(次火山岩热液)。典型斑岩铜矿床、次火山热液矿床、土屋铜矿床对比,土屋铜矿床矿床类型仍不失为斑岩型铜矿,并具有自身特征。 相似文献
179.
180.