全文获取类型
收费全文 | 4827篇 |
免费 | 1087篇 |
国内免费 | 2492篇 |
专业分类
测绘学 | 247篇 |
大气科学 | 471篇 |
地球物理 | 1415篇 |
地质学 | 4678篇 |
海洋学 | 566篇 |
天文学 | 173篇 |
综合类 | 650篇 |
自然地理 | 206篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 13篇 |
2016年 | 16篇 |
2015年 | 42篇 |
2014年 | 10篇 |
2013年 | 39篇 |
2012年 | 22篇 |
2011年 | 491篇 |
2010年 | 300篇 |
2009年 | 460篇 |
2008年 | 141篇 |
2007年 | 297篇 |
2006年 | 515篇 |
2005年 | 580篇 |
2004年 | 1150篇 |
2003年 | 739篇 |
2002年 | 507篇 |
2001年 | 396篇 |
2000年 | 261篇 |
1999年 | 246篇 |
1998年 | 302篇 |
1997年 | 271篇 |
1996年 | 178篇 |
1995年 | 143篇 |
1994年 | 119篇 |
1993年 | 314篇 |
1992年 | 287篇 |
1991年 | 139篇 |
1990年 | 39篇 |
1989年 | 67篇 |
1988年 | 20篇 |
1987年 | 55篇 |
1986年 | 28篇 |
1978年 | 7篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1950年 | 8篇 |
1943年 | 7篇 |
1940年 | 9篇 |
1937年 | 15篇 |
1934年 | 6篇 |
1933年 | 13篇 |
1928年 | 6篇 |
1927年 | 5篇 |
1924年 | 9篇 |
排序方式: 共有8406条查询结果,搜索用时 78 毫秒
651.
Ding Tiping Liu Yushan Wan Defang Liu Zhijian Li Jincheng Zhang Guilan Institute of Mineral Deposits Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》1992,66(3):271-282
Experiments for oxygen isotope exchange between ferberite and water were carried out and the followingequation on oxygen isotope fractionation between ferberite and water against temperature was obtained:Combining this equation with the equation of Clayton et al. (1972) on oxygen isotope fractionation be-tween quartz and water, an equation on oxygen isotope fractionation between quartz and ferberite was ob-tained:The Bigeleison-Mayer function method was used to calculate the oxygen isotope fractionation betweenquartz and ferberite. The theoretical curve obtained agrees with the experimental calibration results quite wellin the temperature range of study.The above calibrated equation has been used in 5 world famous tungsten deposits to determine their tem-peratures of formation. The results show that the temperature range for an idividual deposit determined by thisgeothermometer agrees with those obtained from fluid inclusion determination and other isotopegeothermometers. 相似文献
652.
Li Peiying Cheng Zhenbo Lu Houyuan Liu Guohai First Institute of Oceanography SOA Qingdao Shandong Liaoning Teachers University Dalian Liaoning Liu Linqun 《《地质学报》英文版》1992,66(3):311-325
This Paper discusses the origin of the Coastal Zone Loess on the Liaodong Peninsula, Liaoning Province.The loess is composed mainly of proximal materials transported by low-altitude air flow and less commonly ofinland distal materials carried by high-altitude air flow. The main provenance is the Liaodong Bay. When thesea level declined during glacial period, the bottoms of the Liaodong Bay and Bohai Sea emerged, wheredesertization occurred. As a result, submarine sediments were transported by strong northwesterly winds to theeastern coastal zone of the peninsula and deposited there. These materials mixed with the windblown dust car-ried by atmospheric circulation from the interior of the continent, forming the loess. 相似文献
653.
Xu Ruisong Guangzhou New Technology Institute of Geology Academia Sinica Jiang Minxi 《《地质学报》英文版》1992,66(4)
The vegetation has been poisoned by gold in the western Guangdong-Hainan region. The gold content ofthe leaves there is as high as 10-1961 times the abundance, the chlorophyll content is 10%-30% lower thanthat of the vegetation in metamorphic terrains and 10%-20% higher than that in granite terrains, and thecarotenoid content is 10%-44% lower than the background value. The water content of leaves is 10% to 20%lower than the background value. The cells of leaves are deformed and broken. The leaf surface shows colourspots and becomes yellow or dark green. The spectral reflectance of the leaf surface is 5%-30% higher than thebackground value: the spectral shape has shifted 5-15 nm to the short wavelength. The gray scales of eanopyon images of Landsat TM and airborne imaging scanner (AIS) are 10%-100% higher than the backgroundvalues. On Landsat TM and AIS false colour images, plants poisoned by gold display a yellow color, whichdisinguishes them from background plants. According to the spectral and image features of goldbiogeochemical effects, the author has constructed a gold information system and expert prediction system,and thus two gold target areas and two gold prospect areas have been identified rapidly, economically andaccurately in the western Guangdong-Hainan region which is extensively covered by vegetation. 相似文献
654.
This tutorial paper presents a simplified view of one of the more recently published multivariatecalibration methods particularly suited to dealing with non-linear data sets.The method is referred toas MARS and stands for multivariate adaptive regression splines.Simple examples are provided toexplain the workings of the method. 相似文献
655.
近年来随着航空磁测精度的提高,磁场信息量的增加,磁场规律性更为突出。航磁在研究区域深断裂构造的地质效果比较显著,特别是通过对航磁异常进行垂向导数、方向滤波等项数据处理,使航磁异常在断裂上显示更加清晰。本文通过航磁推测深断裂的研究,来探讨其与铀矿化的关系。 相似文献
656.
657.
658.
659.
里特曼因数共有40个,实际上不敷使用,可运用里特曼稳定矿物组成原理来计算矿物换算因数,同理,还可计算出火成岩岩石密度的近似值。增补两个矿物换算因数:高岭石1.02;硬石膏1.19。 相似文献
660.