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141.
云南兰坪白秧坪铜钴多金属矿集区矿石中石英的40Ar-39Ar快中子活化年龄谱呈马鞍形,坪年龄为56.53±0.43Ma,最小视年龄为55.52±1.78Ma,等时线年龄为55.90±0.29Ma,三者在误差范围内一致(1σ)。40Ar/36Ar初始值为294.7±1.14,与尼尔值(295.5±5)十分接近,坪年龄和等时线年龄均可作为石英的形成时代。因此,55.90~56.53Ma(喜马拉雅早期)代表了矿床的成矿年龄。 相似文献
142.
Genetic types of diamond mineralization 总被引:1,自引:0,他引:1
A. A. Marakushev Sang Longkang You Zhendong I. A. Zotov N. N. Pertsev N. A. Paneyakh 《中国地球化学学报》1998,17(1):12-28
The paper describes the proposed models of diamond formation both in meteorites and in kimberlite and lamproite bodies, metamorphic
complexes and explosive-ring structures (“astroblemes”). The diamond distribution in meteorites (chondrites, iron meteorites
and ureilites) is restricted to taenite-kamasite phase. The diamond generation here is tied up with the first stage of evolution
of the planets. This stage is characterized by high pressure of hydrogen, leading to the formation of the planet envelope.
The second stage of planet evolution began with the progressive impoverishment of their atmospheres in hydrogen due to its
predominant emission into the space and to progressive development of oxidative conditions. The model appears to have proved
the relict nature of diamond mineralization in meteorites.
Diamond and other high-pressure minerals (its “satellites”) were crystallized without any exception in the early intratelluric
stages of peridotite and eclogite-pyroxenite magma evolution just before the magma intrusion into the higher levels of the
mantle and crust where diamond is not thermodynamically stable. The ultramafic intrusive bodies (bearing rich relict diamonds)
in the base of a platform appear to be the substrata for the formation of kimberlite-lamproite magma chambers as a result
of magmatic replacement. The model explains the polyfacial nature of diamondiferous eclogites, pyroxenites and peridotites
and discusses the process of inheritance of their diamond mineralization by kimberlites and lamproites.
Diamond productivity of metamorphic complexes is originated by the inheritance of their diamonds from the above-mentioned
primary diamondiferous rocks. Large diamondiferous explosive-ring structures were formed by high-energy endogenic explosions
of fluid which came from the Earth’s core. This high energy differs endogenic impactogenesis from explosive volcanism. It
proceeds at very high temperature to create diaplectic glasses (monomineral pseudomorphs) —the product of isochoric melting,
at the pressure high enough for the stable formation of very high-density minerals (coesite, stishovite, diamond, lonsdaleit,
and chaoite).
The research project was financially supported by the Russian Foundation of Fundamental Sciences (93-05-8566, 96-05-64307,
and 96-05-00026c0) and China National Natural Science Foundation (No.49794041, No.49611121831). 相似文献
143.
144.
The objective of this study is to investigate the effect of boundary element details of structural walls on their deformation capacities. Structural walls considered in this study have different sectional shapes and/or transverse reinforcement content at the boundaries of the walls (called boundary element details hereafter). Four full‐scale wall specimens (3000mm (hw)×1500mm (lw)×200mm (T)) were fabricated and tested. Three specimens are rectangular in section and the other specimen has a barbell‐shaped cross‐section (a wall with boundary columns). The rectangular wall specimens are reinforced according to the common practice used for reinforced concrete residence buildings in Korea and Chile. In this study, the primary variable for these rectangular specimens is the content of transverse reinforcement to confine the boundary elements of a wall. The barbell‐shaped specimen was designed in compliance with ACI 318‐95. The response of the barbell‐shaped specimen is compared with those of other rectangular specimens. The effective aspect ratio of the specimens is set to two in this study. Based on the experimental results, it is found that the deformation capacities of walls, which are represented by displacement ductility, drift ratio and energy dissipation capacities, are affected by the boundary element details. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
145.
西藏尼洋河水环境特征多元统计分析 总被引:2,自引:1,他引:1
自2008年11月到2009年10月按照月份监测西藏林芝地区尼洋河水环境特征.结果显示,根据Pearson相关性矩阵,可将尼洋河26项理化指标分为3大类,分别是低度相关性理化指标、中度相关性理化指标和高度相关性理化因子.析因分析显示,可将26项理化指标分为4大类,第1类为尼洋河水体常规的理化指标、第2类为尼洋河水体硬度相关指标、第3类为海拔及第4类为影响水生生物生长的水质理化指标.PCA分析发现,平水期、丰水期以及枯水期水环境特征明显不同,以上3期各自聚为一类,而尼洋河沿程方面,水环境特征则不存在差异.构建了尼洋河海拔、底层水温与相关理化因子的一元回归方程.建议加强对尼洋河水环境的监测工作,积极推进尼洋河水域生态环境的可持续发展进程. 相似文献
146.
The genetic diversity and differentiation of four Zostera marina populations along the southern coast of Korea were estimated using random amplified polymorphic DNA (RAPD) markers to determine the effects of natural and anthropogenic stresses and reproductive strategy on within‐population genetic diversity. The mean number of alleles and gene diversities, indicating population genetic diversity, was highest in the Z. marina population that was exposed to repeated environmental disturbances, and lowest in the most undisturbed population. The higher genetic diversity in the disturbed population was associated with a higher contribution of sexual reproduction to population persistence. This suggests that both the level of disturbances and the reproductive strategy for population persistence contributed significantly to population genetic diversity at the study sites. According to the analysis of molecular variance (AMOVA), 76% genetic variation was attributable to differences among individuals within populations. The observed genetic differentiation (FST = 0.241) among Z. marina populations at the study sites appeared to result from reduced meadow size, increased genetic drift, and a high incidence of asexual reproduction. Increased population genetic diversity can enhance resistance and resilience to environmental disturbances; thus, this investigation of seagrass population genetics provides valuable new insights for the conservation, management, and restoration of seagrass habitats. 相似文献
147.
Acta Geotechnica - Previously, in situ tests have been conducted in cold regions since infrastructures such as pipelines have been actively built on frozen ground. However, the engineering... 相似文献
148.
以中华鳖4个种群80个个体(太湖种群、日本品系种群、台湾引进种群和"清溪乌鳖"种群)肌肉基因组DNA为模板,利用已知酪氨酸酶(Tyrosinase,TYR)基因部分序列设计合成特异引物进行PCR扩增,克隆并测定了TYR基因的核苷酸序列.扩增所得的696bp序列中共有13个多态性核苷酸位点.中华鳖体色变异种群的3个个体均在第186核苷酸位点出现相同的变异.以此设计酶切位点,选用SmaI内切酶进行RFLP,结果显示80个中华鳖个体的TYR基因存在多态性.AA型基因除在中华鳖体色变异种群内未发现外,其余三个种群内的频率大小顺序为日本品系种群(60%)>台湾引进种群(30%)>太湖种群(20%),以省外品种为丰富;AB基因型频率大小顺序为"清溪乌鳖"种群(70%)>台湾引进种群(50%)>太湖种群(40%)>日本品系种群(30%). 相似文献
149.
New radiometric dating of the dykes from the Hurd Peninsula, Livingston Island, South Shetland Islands 总被引:1,自引:0,他引:1
Fifteen new K–Ar ages in the range of 79–31 Ma are partially confirmed by three 40Ar/39Ar plateaus and isochron data of 64.9±0.4, 55.5±0.1 and 52.8±0.6 Ma. The new geochronological data reveal a much more detailed picture of the subduction imprint in the Hurd Peninsula. Using cutting relationships, the dyke emplacement history is divided into four episodes. The Late Cretaceous–Paleocene dykes in the range of 80–60 Ma are related to the main magmatism in Livingston Island and most likely reflect the final stages of subduction of the proto-Pacific oceanic crust. The Early Eocene dykes (56–52 Ma) fill the gap in volcanic activity 70–50 Ma ago. They are the only magmatic event manifested at this time in the region. The 45–42 Ma dykes may be related to the intrusion of the Barnard Point tonalite. Three samples of Oligocene age appear to represent the last igneous activities on the Hurd Peninsula prior to the opening of the Bransfield Strait. 相似文献
150.