全文获取类型
| 收费全文 | 378篇 |
| 免费 | 120篇 |
| 国内免费 | 145篇 |
专业分类
| 测绘学 | 9篇 |
| 大气科学 | 7篇 |
| 地球物理 | 28篇 |
| 地质学 | 472篇 |
| 海洋学 | 66篇 |
| 天文学 | 3篇 |
| 综合类 | 34篇 |
| 自然地理 | 24篇 |
出版年
| 2024年 | 6篇 |
| 2023年 | 20篇 |
| 2022年 | 20篇 |
| 2021年 | 25篇 |
| 2020年 | 22篇 |
| 2019年 | 19篇 |
| 2018年 | 39篇 |
| 2017年 | 14篇 |
| 2016年 | 19篇 |
| 2015年 | 22篇 |
| 2014年 | 30篇 |
| 2013年 | 20篇 |
| 2012年 | 38篇 |
| 2011年 | 26篇 |
| 2010年 | 23篇 |
| 2009年 | 11篇 |
| 2008年 | 24篇 |
| 2007年 | 20篇 |
| 2006年 | 18篇 |
| 2005年 | 32篇 |
| 2004年 | 20篇 |
| 2003年 | 16篇 |
| 2002年 | 43篇 |
| 2001年 | 18篇 |
| 2000年 | 11篇 |
| 1999年 | 15篇 |
| 1998年 | 10篇 |
| 1997年 | 19篇 |
| 1996年 | 11篇 |
| 1995年 | 8篇 |
| 1994年 | 11篇 |
| 1993年 | 4篇 |
| 1992年 | 3篇 |
| 1991年 | 4篇 |
| 1989年 | 1篇 |
| 1987年 | 1篇 |
排序方式： 共有643条查询结果，搜索用时 328 毫秒
101.
沉积物孔隙毛细管压力与甲烷水合物饱和度关系研究 总被引：1，自引：1，他引：0
To better understand the relationship between the pore capillary pressure and hydrate saturation in sediments, a new method was proposed. First, the phase equilibria of methane hydrate in fine-grained silica sands were measured. As to the equilibrium data, the pore capillary pressure and saturation of methane hydrate were calculated. The results showed that the phase equilibria of methane hydrates in fine-grained silica sands changed due to the depressed activity of pore water caused by the surface group and negatively charged characteristic of silica particles as well as the capillary pressure in small pores together. The capillary pressure increased with the increase of methane hydrate saturation due to the decrease of the available pore space. However, the capillary-saturation relationship could not yet be described quantitatively because of the stochastic habit of hydrate growth. 相似文献
102.
Utilizing Si, Fe and Mn concentrations within the end-member PACMANUS hydrothermal fluid, Si-Fe-MnH_2 O Pourbaix diagrams were constructed at 300°C and 25°C. The Pourbaix diagrams show that the main Si, Fe and Mn oxides species precipitating from the hydrothermal fluid were Si O_2, Fe(OH)_3, Fe_3(OH)_8, Mn_3O_4, and Mn_2O_3 at 25°C. During mixing of hydrothermal fluid with seawater, Si O_2 precipitated earlier than FeMn-oxyhydroxides because of the lower stability boundary. Then Fe(OH)_2 precipitated first, followed by Fe_3(OH)_8 and Fe(OH)_3, and last, small amounts of Mn_3O_4 and Mn_2O_3 precipitated. Fe(OH)_3 was readily deposited in alkaline solution with little influence by Eh. There were many Si-Fe-Mn-concentric particles in the polished sections of the massive precipitates collected from PACMANUS. In the concentric nucleus and ellipsoid, Si oxides precipitated first before the hydrothermal fluid had mixed with seawater. In the concentric nucleus, after the precipitation of Si oxides, the increase of p H and Eh promoted the precipitation of Mn oxides around the Si oxides. In the large ellipsoid, the precipitation of Fe was divided into two periods. In the early period, increase of p H value of hydrothermal fluid produced by low-temperature convection and an input of a small volume of seawater promoted a small amount of Fe(OH)_3 to precipitate in the Si-rich core. In the late period, after complete mixing with seawater and the resultant fluid was close to neutral or slightly alkaline in p H, Fe(OH)_3 was easily precipitated from the solution and distributed around the Si-rich core. 相似文献
103.
104.
This paper aims a review of the literature related to soil reinforcements to achieve lower soil thermal conductivity （2）. The use of various natural and synthetic fibers, polymers, geosynthetics, agricultural waste/materials, and nanoclays is discussed and existing prediction models that have been thought to affect low thermal conductivity are presented. 相似文献
105.
106.
107.
108.
109.
对煤和干酪根结构的认识得益于技术和方法的不断创新。基于各种方法,先后建立了多个煤和干酪根的结构模型,但至今没有得到普遍认可。原子力显微镜(AFM)可以实时、实空间、原位成像,可以观察单个原子层的局部表面结构,直接观察表面缺陷、表面重构、表面吸附体的形态和位置以及表面扩散等动态过程。在对图像的分析中,AFM超越了传统仪器单纯平面成像的功能,可提供样品表面动态三维图像和用于分析的定量化信息。通过纳米技术,实现了原子级的分辨率的观察,揭示了煤和干酪根聚集态分子和纳米级孔隙的形态、大小、结构及相互间的空间排列特征,显示出在煤和干酪根结构研究中的巨大潜力。纳米技术为煤和干酪根结构的基础研究工作拓展了新的途径,也为非常规油气的勘探开发和煤炭的二次转化研究提供了科学依据。 相似文献
110.