全文获取类型
收费全文 | 772篇 |
免费 | 132篇 |
国内免费 | 200篇 |
专业分类
测绘学 | 31篇 |
大气科学 | 170篇 |
地球物理 | 168篇 |
地质学 | 355篇 |
海洋学 | 99篇 |
天文学 | 80篇 |
综合类 | 111篇 |
自然地理 | 90篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 52篇 |
2021年 | 38篇 |
2020年 | 26篇 |
2019年 | 38篇 |
2018年 | 51篇 |
2017年 | 58篇 |
2016年 | 48篇 |
2015年 | 23篇 |
2014年 | 40篇 |
2013年 | 39篇 |
2012年 | 45篇 |
2011年 | 52篇 |
2010年 | 46篇 |
2009年 | 52篇 |
2008年 | 35篇 |
2007年 | 44篇 |
2006年 | 24篇 |
2005年 | 26篇 |
2004年 | 22篇 |
2003年 | 20篇 |
2002年 | 32篇 |
2001年 | 18篇 |
2000年 | 20篇 |
1999年 | 34篇 |
1998年 | 32篇 |
1997年 | 25篇 |
1996年 | 19篇 |
1995年 | 7篇 |
1994年 | 21篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1980年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有1104条查询结果,搜索用时 15 毫秒
51.
Liu Hongbing Kong Xiangru Xiaobing Ma Wang Qianshen Yan Yongli Yan Yafen Yang Zhiqiang 《中国科学D辑(英文版)》2001,44(1):64-76
Chemical reactions of plagioclase, biotite and their single minerals, as well as a mineral mixture of (plagioclase+biotite+quartz),
with KCl and (KCl+KHCO3) solutions were carried out at 150–400°C and 50–80 MPa. Experiments show that alkaline fluid promotes plagioclase’s changing
into potash feldspar, while acid fluid helps plagioclase, potash feldspar and biotite alteration form chlorite and sericite.
After chemical reaction the acidity-alkalinity of solutions often changes reversely. It was observed that gold dissolved from
the tube wall and recrystallized on the surfaces of biotite and pyrite. Therefore the transportation and enrichment of gold
are related to the elementary effect of the fluid-mineral interfaces. Fe3+-Fe2+, as an oxidition-reduction agent, and volatile components Cl- and CO2 play important roles in the reaction process 相似文献
52.
孔秋雁 《CT理论与应用研究》1996,5(2):30-31
CT球管耙偏移是较为少见的,本文以GE sytec 2000i为例,详细描述了由此引起的扫描停止,机器伪影等现象及分析、处理过程,并通过与管衰老相比较。进一步述了两者的共同点及在图像质量,管电流稳定性,检测过程等方面的区别,最后总结出一套检测与判断耙心偏移的方法。 相似文献
53.
54.
55.
56.
Using a model of relativistic collision between two media and based on the theory of shock waves in an ideal relativistic fluid, we calculate in detail, the main parameters at the Initial stage of the formation of radio component sources, including the separation velocity and the travelling speed of the shock. The evolution of the hot spot as it moved from within the galaxy to a quasi-steady state in the intergalactic space is discussed qualitatively. Lastly, the parameters in the quasi-steady state are approximately evaluated using the formulae for strong shocks. The results obtained are in overall agreement with observations. 相似文献
57.
58.
红阳煤田的岩煤层对比 总被引:1,自引:0,他引:1
采用岩相旋回法、标志层法和煤岩层组合特征等多种方法,对红阳煤田的岩煤层进行综合对比,认为该煤系沉积稳定,标志层明显,易于辨认及对比,岩性、岩相变化有一定规律可循,具有比较明显的旋回结构,煤层层位在旋回上有一定的分布规律,为一套海陆交互相滨海平原型沉积。 相似文献
59.
This paper presents a new perturbation solution of the non-linear Boussinesq equation for one-dimensional tidal groundwater flow in a coastal unconfined aquifer. Built upon the work of Parlange et al. [Parlange, J.-Y., Stagnitti, F., Starr, J.L., Braddock, R.D., 1984. Free-surface flow in porous media and periodic solution of the shallow-flow approximation, J. Hydrol., 70, 251–263], the solution adopts a new perturbation parameter that is by definition less than unit, and thus is applicable to a wider range of physical conditions within the constraint of the Boussinesq approximation. This approach avoids a secular term in the third-order perturbation equation of Parlange et al. (1984), enabling the derivation of the third- and higher-order solutions. In comparison with a numerical (“exact”) solution, the new perturbation solution is shown to be slightly more accurate than that of Parlange et al. (1984) with the second-order approximation. The obtained third-order solution exhibits considerable improvement in accuracy. In relatively simple analytical forms, the present perturbation solution will help to understand better the non-linear characteristics of tidal water table fluctuations in as modeled by the non-linear Boussinesq equation coastal unconfined aquifers. 相似文献
60.