全文获取类型
收费全文 | 1669篇 |
免费 | 96篇 |
国内免费 | 98篇 |
专业分类
测绘学 | 73篇 |
大气科学 | 69篇 |
地球物理 | 331篇 |
地质学 | 1053篇 |
海洋学 | 105篇 |
天文学 | 99篇 |
综合类 | 45篇 |
自然地理 | 88篇 |
出版年
2023年 | 7篇 |
2022年 | 22篇 |
2021年 | 38篇 |
2020年 | 47篇 |
2019年 | 35篇 |
2018年 | 131篇 |
2017年 | 113篇 |
2016年 | 126篇 |
2015年 | 73篇 |
2014年 | 111篇 |
2013年 | 186篇 |
2012年 | 74篇 |
2011年 | 96篇 |
2010年 | 71篇 |
2009年 | 73篇 |
2008年 | 43篇 |
2007年 | 35篇 |
2006年 | 44篇 |
2005年 | 32篇 |
2004年 | 43篇 |
2003年 | 67篇 |
2002年 | 116篇 |
2001年 | 83篇 |
2000年 | 38篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 14篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有1863条查询结果,搜索用时 125 毫秒
141.
鄯科 1井是吐鲁番—哈密盆地台北凹陷首次钻穿三叠系的一口科学探索井 ,并首次在三叠系发现轻质油流。文内以鄯科 1井为例 ,运用孢粉组合、岩性组合、地震剖面、倾角测井、无机元素、地球化学等多种方法从不同侧面分析了鄯科 1井三叠系内部地层重复的现象 ,这些方法有机的结合和相互的补充打破了单一方法进行地层划分的旧模式 ,初步进行了多方法交互使用进行地质分层的尝试 ,从而有效地消除了地层划分与对比中的多解性 ,使地层划分更可靠 ,相信这些方法的交互使用在其他地区和单井的地层划分对比中也同样有较好的使用价值 相似文献
142.
143.
氢化物发生—原子荧光光谱法测定煤样中的硒 总被引:6,自引:2,他引:6
采用氢化物发生原子荧光光谱法测定了煤样中的总Se。煤样选用高压闷罐强酸消解的方法进行处理,所得消解液经6mol/L HCl将Se(Ⅵ)还原为Se(Ⅳ),然后进行测定。标准工作曲线的线性范围为0-400μg/L Se,检测限为0.4μg/L Se。用标准参考物质煤飞灰对方法进行了验证,所得总Se含量与标准值相符,对ω为10^-6级Se的4次测定,RSD≤4.5%。 相似文献
144.
从新疆和硕县南山金矿床地质特征和地球化学特征的入手,分析其独特的控矿地质因素,提出了矿床的地质、地球化学找矿标志。 相似文献
145.
146.
Khouloud Gader Ahlem Gara Marnik Vanclooster Slaheddine Khlifi Mohamed Slimani 《水文科学杂志》2020,65(8):1300-1315
ABSTRACT Predicting the impacts of climate change on water resources remains a challenging task and requires a good understanding of the dynamics of the forcing terms in the past. In this study, the variability of precipitation and drought patterns is studied over the Mediterranean catchment of the Medjerda in Tunisia based on an observed rainfall dataset collected at 41 raingauges during the period 1973–2012. The standardized precipitation index and the aridity index were used to characterize drought variability. Multivariate and geostatistical techniques were further employed to identify the spatial variability of annual rainfall. The results show that the Medjerda is marked by a significant spatio-temporal variability of drought, with varying extreme wet and dry events. Four regions with distinct rainfall regimes are identified by utilizing the K-means cluster analysis. A principal component analysis identifies the variables that are responsible for the relationships between precipitation and drought variability. 相似文献
147.
The present study deals with tectonomagmatic evolution of the collision-related leucogranite located near the northwest corner of exposed basement in Sinai, Egypt. The area is composed of: (1) a gabbroic complex; (2) amphibolite; (3) post-orogenic leucogranite; (4) Feiran gneisses. The amphibolite and gabbroic suites, generated in an island arc environment, have a high Fe-tholeiitic affinity and were derived from two independent magmas. On the basis of rare earth element (REE) patterns, the gabbroic melts could have been generated from a garnet- and amphibole-bearing, enriched mantle, and were subsequently modified by fractional crystallization of pyroxene and amphibole with minor plagioclase, whereas the amphibolite melts could be derived from garnet-free depleted mantle.The leucogranite has high Al2O3 content (>13 wt%), alumina saturation index (ASI) mostly >1, and normative corundum, indicating a peraluminous nature. Chondrite-normalized REE patterns for the leucogranite show light REE enrichment (La/SmN=2.7–4.86), general flattening of the heavy REE (Gd/LuN=1.2–2), and negative europium (Eu) anomalies (Eu/Eu*=0.24–0.47). The peraluminous nature and enrichment of the incompatible elements (K, Rb, Ba and Th) in the leucogranite strongly suggest derivation from a crustal source. The most probable source for the leucogranite magmas is represented by the adjacent Feiran gneisses, which could have generated the leucogranite by dehydration melting under water-undersaturated conditions. It appears likely that the restite unmixing model is responsible for the chemical variations within the leucogranite. In accordance with this model, the chemical variation of the leucogranite can be attributed to varying degrees of separation of restitic material from the melt during its emplacement and solidification and fractional crystallization could have played a minor role during magma ascent through the crust. 相似文献
148.
149.
Hydro-mechanical evaluation of stabilized mine tailings 总被引:3,自引:0,他引:3
150.