全文获取类型
收费全文 | 10693篇 |
免费 | 2540篇 |
国内免费 | 5984篇 |
专业分类
测绘学 | 40篇 |
大气科学 | 2篇 |
地球物理 | 264篇 |
地质学 | 17675篇 |
海洋学 | 160篇 |
综合类 | 942篇 |
自然地理 | 134篇 |
出版年
2024年 | 75篇 |
2023年 | 262篇 |
2022年 | 413篇 |
2021年 | 506篇 |
2020年 | 438篇 |
2019年 | 564篇 |
2018年 | 494篇 |
2017年 | 639篇 |
2016年 | 758篇 |
2015年 | 701篇 |
2014年 | 1010篇 |
2013年 | 824篇 |
2012年 | 1061篇 |
2011年 | 957篇 |
2010年 | 908篇 |
2009年 | 768篇 |
2008年 | 696篇 |
2007年 | 771篇 |
2006年 | 716篇 |
2005年 | 631篇 |
2004年 | 629篇 |
2003年 | 562篇 |
2002年 | 522篇 |
2001年 | 560篇 |
2000年 | 540篇 |
1999年 | 499篇 |
1998年 | 482篇 |
1997年 | 458篇 |
1996年 | 421篇 |
1995年 | 329篇 |
1994年 | 256篇 |
1993年 | 192篇 |
1992年 | 170篇 |
1991年 | 130篇 |
1990年 | 79篇 |
1989年 | 73篇 |
1988年 | 50篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 12篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
381.
An experimental study on reduction of U (Ⅵ) by anaerobic bacteria, Shewane//a putrefaciens, is first reported here in China. The experimental conditions were: 35℃ and pH =7.0-7.4, corresponding to a physicochemical environments in which the sandstone-hosted interlayer oxidation-zone type uranium deposit formed in Northwest China's Xinjiang. Bacteria adopted in the present experiment, Shewanella putrefaciens, occur extensively in natural environment. Our study shows that nano-crystal precipitates of uraninite quickly occurred on the surface of the cells within one week. It was found that the pitchblende was characterized by a random arrangement of uraninite nanocrystals (2-4 nm) in it, significantly different from natural pitchblende in which uraninite nanocrystals are arranged in order. Finally, a possible mechanism of uranium biomineralization by microorganisms in the deposits is discussed. Our investigation may supply a technical train of thoughts for bioremediation of nuclear-contaminated water environments and for underground dissolving extraction of the sandstone-hosted uranium ores. 相似文献
382.
东坡矿田与千里山岩体有关的铅锌矿床深部锡资源潜力及找矿方向 总被引:1,自引:0,他引:1
东坡矿田内与千里山岩体有关的铅锌矿产资源已近枯竭,必须对这些矿区的深部进行成矿预测,寻找可接替矿产资源.根据近年来该区深部找矿的新进展,在分析矿田成矿地质背景、矿床分布规律、航磁及化探异常的基础上,运用成矿指数对比法进行成矿预测.研究结果表明,在柴山、东坡山和天鹅塘-南风坳3个铅锌矿区的深部具有较大的锡资源找矿潜力. 相似文献
383.
384.
山东省泰安朱家庄自然硫矿床,赋存于鲁西断隆古近纪汶东陆相盆地。自然硫矿层在汶口组二段上亚段,泥质灰岩-含泥灰岩-含云灰岩-石膏岩韵律层中的白云岩-石膏岩层段发育。自然硫以胶态、晶态、土态3种形态产出,可划分为顺层型、准顺层型、斑杂型及不顺层型4大类10余种矿石类型。从矿区去膏化作用普遍、自然硫与石膏-硬石膏分别富集轻-重同位素的特征、油气显示明显及地下水主要径流方向自然硫矿化最强等各种证据,表明该矿属生物后生成因的矿床。 相似文献
385.
386.
387.
Microorganisms in the lateritic profiles of the Lianxian gold deposit in Guangdong were cultured, isolated and identified. The microorganisms include bacteria such as Bacillus, Enterobacter, Pseudomonas, Lactobacillus, Actinetobacter, Aeromona, Listeria, Agrobacteriura, Cotyttebacteriurn, and Moraxella, fungi such as Penicillium, Alter naria, Cladosporium, Saccharcornyces, Mucor, and the chemoautotrophic Thiobacillu.~. It is shown in a leaching experiment that the microorganisms can accelerate the leaching of Cu, Cd, Zn, and that the G- bacteria are most efficient for leaching Cu, Zn and the G^ bacteria are better for leaching Cd. 相似文献
388.
A simulated experimental reduction of U^v1 and the synthesis of uraninite by a sulfate-reducing bacteria,Desulfovibrio desulfuricans DSM 642, are first reported. The simulated physicochemical experimental conditions were:35℃, pH=7.0-7.4, corresponding to the environments of formation of the sandstone-hosted interlayer oxidation-zone type uranium deposits in Xinjiang, NW China. Uraninite was formed on the surface of the host bacteria after a one-week‘s incubation. Therefore, sulfate-reducing bacteria, which existed extensively in Jurassic sandstone-producing environments,might have participated in the biomineralization of this uranium deposit. There is an important difference in the orderdisorder of the crystalline structure between the uraninite produced by Desulfovibrio desulfuricans and naturally occurring uraninite. Long time and slow precipitation and growth of uraninite in the geological environment might have resulted in larger uraninite crystals, with uraninite nanocrystals arranged in order, whereas the experimentally produced uraninite is composed of unordered uraninite nanocrystals which, in contrast, result from the short time span of formation and rapid precipitation and growth of uraninite. The discovery has important implications for understanding genetic significance in mineralogy, and also indicates that in-situ bioremediation of U-contaminated environments and use of biotechnology in the treatment of radioactive liquid waste is being contemplated. 相似文献
389.
Primary Ore Mineral Assemblage and Fluid Inclusion Study of the Batu Hijau Porphyry Cu-Au Deposit, Sumbawa, Indonesia 总被引:3,自引:0,他引:3
Abstract. The Batu Hijau porphyry Cu‐Au deposit, Sumbawa Island, Indonesia, is associated with a tonalitic intrusive complex. The temperature‐pressure condition of mineralization at the Batu Hijau deposit is discussed on the basis of fluid inclusion microthermometry. Then, the initial Cu‐Fe sulfide mineral assemblage is discussed. Bornite and chalcopyrite are major copper ore minerals associated with quartz veinlets. The quartz veinlets have been classified into ‘A’ veinlets associated with bornite, digenite, chalcocite and chalcopyrite, ‘B’ veinlets having chalcopyrite bornite along vuggy center‐line, rare ‘C’ chalcopyrite‐quartz veinlets, and late ‘D’ veinlets consisting of massive pyrite and quartz (Clode et al., 1999). Copper and gold mineralization is associated with abundant ‘A’ quartz veinlets. Abundant fluid inclusions are found in veinlet quartz consisting mainly of gas‐rich inclusions and polyphase inclusions throughout the veinlet types. The hydrothermal activity occurred in temperature‐pressure conditions of aqueous fluid immiscibility into hypersaline brine and dilute vapor. The halite dissolution (Tm[halite]) and liquid‐vapor homogenization (Th) temperatures of the polyphase inclusions in veinlet quartz range from 270 to 472d?C and from 280 to 454d?C, respectively. The estimated salinity ranges from 36 to 47 wt% (NaCl equiv.). The apparent pressures lower than 300 bars are estimated to have been along the liquid‐vapor‐halite curve for the fluid inclusions having the Th lower than the Tm that trapped the brine saturated with halite, or at slightly higher pressure relative to liquid‐vapor‐halite curve for the fluid inclusions having the Th higher than the Tm that trapped the brine unsaturated with halite. The actual temperature and pressure during the hydrothermal activity at the Batu Hijau deposit are estimated to have been around 300d?C and 50 bars. At such temperature‐pressure conditions, the principal and initial Cu‐Fe sulfide mineral assemblages are thought to be chalcopyrite + bornite solid solution (bnss) for the chalcopyrite‐bearing assemblage, and chalcocite‐digenite solid solution and bnss for the chalcopyrite‐free assemblage. 相似文献
390.
Akira Imai 《Resource Geology》2005,55(2):73-90
Abstract. Evolution of hydrothermal system from initial porphyry Cu mineralization to overlapping epithermal system at the Dizon porphyry Cu‐Au deposit in western central Luzon, Zambales, Philippines, is documented in terms of mineral paragen‐esis, fluid inclusion petrography and microthermometry, and sulfur isotope systematics. The paragenetic stages throughout the deposit are summarized as follows; 1) stockwork amethystic quartz veinlets associated with chalcopyrite, bornite, magnetite and Au enveloped by chlorite alteration overprinting biotite alteration, 2) stockwork quartz veinlets with chalcopyrite and pyrite associated with Au and chalcopyrite and pyrite stringers in sericite alteration, 3) stringer quartz veinlets associated with molybdenite in sericite alteration, and 4) WNW‐trending quartz veins associated with sphalerite and galena at deeper part, while enargite and stibnite at shallower levels associated with advanced argillic alteration. Chalcopyrite and bornite associated with magnetite in quartz veinlet stockwork (stage 1) have precipitated initially as intermediate solid solution (iss) and bornite solid solution (bnss), respectively. Fluid inclusions in the stockwork veinlet quartz consist of gas‐rich inclusions and polyphase inclusions. Halite in polyphase inclusions dissolves at temperatures ranging from 360d?C to >500d?C but liquid (brine) and gas (vapor) do not homogenize at <500d?C. The maximum pressure and minimum temperature during the deposition of iss and bnss with stockwork quartz veinlets are estimated to be 460 bars and 500d?C. Fluid inclusions in veinlet stockwork quartz enveloped in sericite alteration (stage 2) consist mainly of gas‐rich inclusions and polyphase inclusions. In addition to the possible presence of saturated NaCl crystals at the time of entrapment of fluid inclusions that exhibit the liquid‐vapor homogenization temperatures lower than the halite dissolution temperatures in some samples, wide range of temperatures of halite dissolution and liquid‐vapor homogenization of polyphase inclusions from 230d?C to >500d?C and from 270d?C to >500d?C, respectively, suggests heterogeneous entrapment of gaseous vapor and hypersaline brine. The minimum pressure and temperature are estimated to be about 25 bars and 245d?C. Fluid inclusions in veinlet quartz associated with molybdenite (stage 3) are dominated by gas‐rich inclusions accompanied with minor liquid‐rich inclusions that homogenize at temperatures between 350d?C and 490d?C. Fluid inclusions in vuggy veinlet quartz associated with stibnite (stage 4) consist mainly of gas‐rich inclusions with subordinate polyphase inclusions that do not homogenize below 500d?C. Fluid inclusions in veinlet quartz associated with galena and sphalerite (stage 4) are composed of liquid‐rich two‐phase inclusions, and they homogenize into liquid phase at temperatures ranging widely from 190d?C to 300d?C (suggesting boiling) and the salinity ranges from 1.0 wt% to 3.4 wt% NaCl equivalent. A pressure of about 15 bars is estimated for the dilute aqueous solution of 190d?C from which veinlet quartz associated with galena and sphalerite precipitated. In addition to a change in temperature‐pressure regime from lithostatic pressure during the deposition of iss and bnss with stockwork quartz veinlets to hydrostatic pressure during fracture‐controlled quartz veinlet associated with galena and sphalerite, a decrease in pressure is supposed to have occurred due to unroofing or removal of the overlying piles during the temperature decrease in the evolution of hydrothermal system. The majority of the sulfur isotopic composition of sulfides ranges from ±0 % to +5 %. Sulfur originated from an iso‐topically uniform and homogeneous source, and the mineralization occurred in a single hydrothermal system. 相似文献