全文获取类型
收费全文 | 5186篇 |
免费 | 1291篇 |
国内免费 | 1682篇 |
专业分类
测绘学 | 73篇 |
大气科学 | 262篇 |
地球物理 | 939篇 |
地质学 | 5544篇 |
海洋学 | 816篇 |
天文学 | 64篇 |
综合类 | 269篇 |
自然地理 | 192篇 |
出版年
2024年 | 38篇 |
2023年 | 93篇 |
2022年 | 234篇 |
2021年 | 231篇 |
2020年 | 231篇 |
2019年 | 321篇 |
2018年 | 239篇 |
2017年 | 265篇 |
2016年 | 313篇 |
2015年 | 294篇 |
2014年 | 363篇 |
2013年 | 366篇 |
2012年 | 364篇 |
2011年 | 423篇 |
2010年 | 357篇 |
2009年 | 393篇 |
2008年 | 372篇 |
2007年 | 362篇 |
2006年 | 377篇 |
2005年 | 361篇 |
2004年 | 285篇 |
2003年 | 290篇 |
2002年 | 246篇 |
2001年 | 184篇 |
2000年 | 218篇 |
1999年 | 162篇 |
1998年 | 184篇 |
1997年 | 125篇 |
1996年 | 106篇 |
1995年 | 81篇 |
1994年 | 60篇 |
1993年 | 43篇 |
1992年 | 45篇 |
1991年 | 26篇 |
1990年 | 20篇 |
1989年 | 16篇 |
1988年 | 22篇 |
1987年 | 6篇 |
1986年 | 14篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有8159条查询结果,搜索用时 46 毫秒
211.
212.
Wei Dang Jin-Chuan Zhang Xuan Tang Xiao-Liang Wei Zhong-Ming Li Cheng-Hu Wang Qian Chen Chong Liu 《地学前缘(英文版)》2018,9(2):559-575
Measuring gas content is an essential step in estimating the commerciality of gas reserves. In this study,eight shale core samples from the Mouye-1 well were measured using a homemade patented gas desorption apparatus to determine their gas contents. Due to the air contamination that is introduced into the desorption canister, a mathematical method was devised to correct the gas quantity and quality.Compared to the chemical compositions of desorbed gas, the chemical compositions of residual gas are somewhat different. In residual gas, carbon dioxide and nitrogen record a slight increase, and propane is first observed. This phenomenon may be related to the exposure time during the transportation of shale samples from the drilling site to the laboratory, as well as the differences in the mass, size and adsorptivity of different gas molecules. In addition to a series of conventional methods, including the USBM direct method and the Amoco Curve Fit(ACF) method, which were used here for lost gas content estimation, a Modified Curve Fit(MCF) method, based on the 'bidisperse' diffusion model, was established to estimate lost gas content. By fitting the ACF and MCF models to gas desorption data, we determined that the MCF method could reasonably describe the gas desorption data over the entire time period, whereas the ACF method failed. The failure of the ACF method to describe the gas desorption process may be related to its restrictive assumption of a single pore size within shale samples. In comparison to the indirect method, this study demonstrates that none of the three methods studied in this investigation(USBM, ACF and MCF) could individually estimate the lost gas contents of all shale samples and that the proportion of free gas relative to total gas has a significant effect on the estimation accuracy of the selected method. When the ratio of free gas to total gas is lower than 45%, the USBM method is the best for estimating the lost gas content, whereas when the ratio ranges from 45% to 75% or is more than 75%, the ACF and MCF methods, are the best options respectively. 相似文献
213.
A digital geoelectric model of the Karaton-Sarkamys block located in the southern (Kazakhstan) part of the Caspian Depression has been developed on the basis of processing and interpretation of magnetotelluric sounding data. Geoelectric sections and structural maps of geoelectric layers have been constructed. It has been shown that magnetotelluric sounding combined with seismic and GIS data can be efficiently used to obtain additional information on the lithologic and reservoir properties of petroleum plays. 相似文献
214.
《China Geology》2018,1(3):346-353
There are plenty of Sinian and Cambrian potential shale gas resources in South China, which is characterized by high thermal evolution degrees, poor drilling performances and only occurs in local areas. Taking the principle “high to find low” is the key issue to achieving a breakthrough in older shale. China Geological Survey drilled in the periphery of the Proterozoic basement, i.e. the Huangling anticline, in the western Hubei, and Hannan paleocontinent in the southern Shanxi. It received high-quality gas-bearing shale with relatively low Ro in the in Lower Cambrian Niutitang formation and Sinian Doushantuo formation. Based on geological conditions of shale gas reservoirs in the Huangling anticline, this paper puts forward the new model named “Control over reservoirs by periphery of basement” about shale gas accumulation, suggesting that the shale deposited in a deepwater continental shelf in the periphery of the basement is characterized by shallow burial, a short burial time, stable tectonics, relatively low thermal evolution degrees, and shale gas reservoirs in a good condition. The shale of the Sinian-Cambrian strata deposited in deepwater continental shelves in the periphery of Chuanzhong paleo-uplift in Sichuan, Hannan paleocontinent in the southern Shanxi, Huangling anticline in western Hubei and Jiangnang-Xuefeng paleo-uplift in Hunan and Guizhou province have good shale gas exploration potential. 相似文献
215.
地热作为一种清洁能源,在我国经济发展与能源转型过程中正发挥着越来越重要的作用。“全国地热资源调查评价与勘查示范工程”自实施以来,主要开展了京津冀地区地热资源评价以及东南沿海和青藏高原东部干热岩的勘查等工作。这些工作的开展在获得一系列科研突破成果的同时,也解决了大量地热开发的工程问题,积累了大量成果和经验。该文对工程取得的进展及成果进行了总结,对工作开展中出现的问题进行了探讨,可用于指导我国地热资源勘查开发工作。 相似文献
216.
渝东北城口地区Y1井页岩有机地球化学特征及勘探前景 总被引:1,自引:0,他引:1
基于钻井资料,以总有机碳(TOC)、干酪根显微组分、等效镜质体反射率(Ro)及碳同位素等测试数据系统分析了渝东北城口地区Y1井五峰组—龙马溪组页岩的有机地球化学特征,利用页岩流体包裹体的显微特征、均一温度及激光拉曼数据深入分析了Y1井页岩气成藏特征。结果表明:Y1井上奥陶统五峰组—下志留统龙马溪组炭质页岩发育,TOC含量2%的富含有机质页岩厚度达83 m,干酪根类型以Ⅰ型干酪根为主,处于湿气生烃阶段。页岩裂缝脉体中大量烃包裹体和富含甲烷气体的含烃盐水包裹体证实城口地区五峰组—龙马溪组页岩发生了充足页岩气供给,具有高均一温度、高盐度的伴生盐水包裹体表明城口地区页岩气成藏时期的保存条件良好。这些Y1井页岩有机地球化学特征研究成果揭示了城口地区下古生界具备良好的页岩气勘探前景。 相似文献
217.
为缓解能源紧张,页岩气作为储量丰富的非常规能源在我国正大力开发,而我国页岩气开发起步较晚,受管理与技术限制,页岩气开发造成的综合环境影响问题还得不到有效解决。针对页岩气开发存在的环境问题,本文基于我国页岩气开发现状,借鉴美国页岩气开发的成功经验,从自然环境与人文环境两方面对页岩气开发综合环境影响因素进行分析,建立了页岩气开发综合环境影响评价指标体系;同时为降低评价过程主观因素的影响,简化评估过程,本文引入突变级数法建立了页岩气开发综合环境影响评估模型,运用数值替换方法区分页岩气开发综合环境影响等级。最后将评价体系与评估模型应用到实际案例中,得到的评价结果与实际情况基本符合,为页岩气开发项目的综合环境评价提供了很好的理论依据。 相似文献
218.
Y. Y. Huyan T. S. Liu F. J. Jiang X. Z. Chen X. Q. Ma 《Australian Journal of Earth Sciences》2018,65(6):863-875
Residual and movable porosity are significant parameters for characterising petrophysical properties, especially in tight reservoirs. Eight tight sandstone samples from the upper Paleozoic gas-bearing strata in the Kangning area, from the eastern margin of the Ordos Basin, were analysed using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), petrography, and porosity and permeability tests. The lithology and pore types were identified and classified using petrography and SEM. The residual and movable porosity were obtained with NMR. In addition, NMR was used to visualise pore structure and pore size distribution. The results suggest that the upper Paleozoic sandstones in the study area mainly comprise feldspathic litharenite and litharenite. The sandstone porosity and permeability are low, with means of 5.9% and 0.549 mD, respectively. Four pore types exist in the tight sandstones: residual primary pores, grain dissolution pores, micropores (clay-dominated) and microfractures. The T2 spectra under water-saturated conditions correlate with pore size and can be used to distinguish small and large pores based on the transverse relaxation time cutoff value of 10 ms, which corresponds to a pore diameter of 0.232 μm. Small pores account for 72% of the pores in the tight sandstones. The continuous bimodal T2 spectra suggest good connectivity between small and large pores, despite the low porosity and permeability. In this study, the movable porosity of the major tight sandstone gas reservoirs is higher than the residual porosity, which confirms the effective evaluation of movable porosity to tight sandstone reservoirs, based on NMR experiments. 相似文献
219.
塔里木溢流玄武岩火山通道的三维结构及其热成因气体释放 总被引:1,自引:1,他引:0
塔里木上奥陶统-志留系沉积地层中广泛发育早二叠世溢流玄武岩的火山通道相岩床-岩墙网络。三维地震数据解释结果显示,这些火山通道以平行围岩地层的岩床和斜切围岩地层的"碟状岩床"为主要特征。在玄武岩喷发过程中,火山通道岩浆的热量可以导致沉积围岩发生热接触变质并将沉积围岩中的有机质转化为"热成因气体"。在塔北英买2井区火山通道烘烤沉积围岩模型基础上,利用有限元热模拟方法确定了该区早二叠世玄武岩喷发时火山通道热烘烤影响范围随时间的变化。基于沉积围岩有机质丰度估算,该区热烘烤成因甲烷释放量可达11.3Gt(即113亿吨)。如果整个塔里木溢流玄武岩省具有与英买2地区相同的释放强度,则塔里木溢流玄武岩省活动期间释放的甲烷总量可达7062.5Gt,必然导致非常显著的环境效应。同时,玄武岩火山通道岩浆引起的热接触变质作用对已存在的油藏具有明显的破坏作用,塔里木盆地古生界总量约8~10Gt的油藏破坏和大量沥青的形成可能与此有关。 相似文献
220.