全文获取类型
收费全文 | 15509篇 |
免费 | 3371篇 |
国内免费 | 7136篇 |
专业分类
测绘学 | 291篇 |
大气科学 | 297篇 |
地球物理 | 775篇 |
地质学 | 21701篇 |
海洋学 | 584篇 |
天文学 | 150篇 |
综合类 | 1380篇 |
自然地理 | 838篇 |
出版年
2024年 | 76篇 |
2023年 | 324篇 |
2022年 | 589篇 |
2021年 | 719篇 |
2020年 | 648篇 |
2019年 | 767篇 |
2018年 | 670篇 |
2017年 | 815篇 |
2016年 | 934篇 |
2015年 | 901篇 |
2014年 | 1254篇 |
2013年 | 1114篇 |
2012年 | 1275篇 |
2011年 | 1205篇 |
2010年 | 1140篇 |
2009年 | 991篇 |
2008年 | 933篇 |
2007年 | 1048篇 |
2006年 | 956篇 |
2005年 | 877篇 |
2004年 | 877篇 |
2003年 | 757篇 |
2002年 | 751篇 |
2001年 | 825篇 |
2000年 | 778篇 |
1999年 | 749篇 |
1998年 | 696篇 |
1997年 | 663篇 |
1996年 | 605篇 |
1995年 | 469篇 |
1994年 | 408篇 |
1993年 | 307篇 |
1992年 | 266篇 |
1991年 | 205篇 |
1990年 | 126篇 |
1989年 | 111篇 |
1988年 | 75篇 |
1987年 | 55篇 |
1986年 | 25篇 |
1985年 | 18篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1972年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
茅排金矿床属中-低温硫化物金矿床,矿体的分布严格受断裂构造控制.通过应用不同的物探方法来寻找控矿断裂,从而达到间接地寻找矿体分布的目的,取得了较好的效果。 相似文献
13.
四川石棉大水沟独立碲矿床堪称世界首例,其矿体两侧的围岩蚀变较窄,且蚀变带与矿脉及未蚀变岩呈清楚而截然的接触关系。主要围岩蚀变为白云石化、白(绢)云母化、云英岩化及电气石化等。这些蚀变作用分别发生于177.7~165.1Ma和91.71~80.19Ma。蚀变作用过程中SiO2大量析出,Al2O3、TiO2、CaO、MgO、K2O、H2O、CO2、Fe2O3、MnO则有不同程度地带入。与此同时,REE在此过程中包集体迁出,Te、Bi、AS等元素的含量则决定于蚀变作用及其强度,而与原岩无关。 相似文献
14.
A new species,Clathrocorys gracilis nov. spec. of Tripocyrtidae (Radiolarians: Nassellaria) from surface water in northern South China Sea, is described in this
paper. The new species has four radial beams arising from the cephalic base centre, each foot with cup-shaped structure and
ramified bar in the proximal section (near cephalic base), and each wing with a large mesh in the middle, a medium mesh and
a small mesh on each side respectively.
Project supported by the NSFC (No. 40276044) and the Chinese Academy of Sciences (No. KSCX2-SW-101B). 相似文献
15.
Tanlu Fault Zone (TFZ) is a large NE trending deep fracture system in East China and is about 2500 km long. It extends from the south of Lujiang to Tancheng, and passes through the Bohai Sea and continues to the north, where it branches into Yilan ?Shulan Fault and Dunhua ?Mishan Fault. TFZ is a long lasting huge deep - rooted lithospherical fault system with different characteristics in different parts and at different periods of its evolution. TFZ also controls the distribution and occur-rences of many superlarge, large, middle and small sized gold ore deposits, e. g. Jiapigou, Haigou, Xiaoxihancha and Ciwei-gou gold deposits in Northeast China; Linglong, Jiaojia, Sanshandao, Taishang, Xincheng, Rushan, and Pengjiakuang gold deposits in Jiaodong Peninsula of Shandong Province; and Guilaizhuang and Yinan in Western Shandong Province. 相似文献
16.
本文简述了沙柳河南区有色金属矿床的基本特征。通过对成矿热液及成矿物质的来源与性质的研究,认为该矿床的成因类型为火山沉积—接触交代改造叠加型,进而探讨了该矿床的成矿模式。 相似文献
17.
An inescapable consequence of the metamorphism of greenstone belt sequences is the release of a large volume of metamorphic fluid of low salinity with chemical characteristics controlled by the mineral assemblages involved in the devolatilization reactions. For mafic and ultramafic sequences, the composition of fluids released at upper greenschist to lower amphibolite facies conditions for the necessary relatively hot geotherm corresponds to those inferred for greenstone gold deposits (XCO2= 0.2–0.3). This result follows from the calculation of mineral equilibria in the model system CaO–MgO–FeO–Al2O3–SiO2–H2O–CO2, using a new, expanded, internally consistent dataset. Greenstone metamorphism cannot have involved much crustal over-thickening, because very shallow levels of greenstone belts are preserved. Such orogeny can be accounted for if compressive deformation of the crust is accompanied by thinning of the mantle lithosphere. In this case, the observed metamorphism, which was contemporaneous with deformation, is of the low-P high-T type. For this type of metamorphism, the metamorphic peak should have occurred earlier at deeper levels in the crust; i.e. the piezothermal array should be of the ‘deeper-earlier’type. However, at shallow crustal levels, the piezothermal array is likely to have been of ‘deeper-later’type, as a consequence of erosion. Thus, while the lower crust reached maximum temperatures, and partially melted to produce the observed granites, mid-crustal levels were releasing fluids prograde into shallow crustal levels that were already retrograde. We propose that these fluids are responsible for the gold mineralization. Thus, the contemporaneity of igneous activity and gold mineralization is a natural consequence of the thermal evolution, and does not mean that the mineralization has to be a consequence of igneous processes. Upward migration of metamorphic fluid, via appropriate structurally controlled pathways, will bring the fluid into contact with mineral assemblages that have equilibrated with a fluid with significantly lower XCO2. These assemblages are therefore grossly out of equilibrium with the fluid. In the case of infiltrated metabasic rocks, intense carbonation and sulphidation is predicted. If, as seems reasonable, gold is mobilized by the fluid generated by devolatilization, then the combination of processes proposed, most of which are an inevitable consequence of the metamorphism, leads to the formation of greenstone gold deposits predominantly from metamorphic fluids. 相似文献
18.
19.
IntroductionThe area of eastern Liaoning is an importantmetal and nonmetal metallogenetic district in China,and the Liaohe group is one of the most importantstrata that hosts Pb, Zn, Au, B and Mg etcstratabound deposits. Up to now many geo1ogistssuch as Z… 相似文献
20.