全文获取类型
收费全文 | 3641篇 |
免费 | 793篇 |
国内免费 | 1122篇 |
专业分类
测绘学 | 1450篇 |
大气科学 | 1867篇 |
地球物理 | 505篇 |
地质学 | 826篇 |
海洋学 | 337篇 |
天文学 | 86篇 |
综合类 | 320篇 |
自然地理 | 165篇 |
出版年
2024年 | 8篇 |
2023年 | 70篇 |
2022年 | 174篇 |
2021年 | 229篇 |
2020年 | 268篇 |
2019年 | 232篇 |
2018年 | 161篇 |
2017年 | 287篇 |
2016年 | 222篇 |
2015年 | 283篇 |
2014年 | 322篇 |
2013年 | 279篇 |
2012年 | 310篇 |
2011年 | 270篇 |
2010年 | 203篇 |
2009年 | 223篇 |
2008年 | 184篇 |
2007年 | 259篇 |
2006年 | 205篇 |
2005年 | 186篇 |
2004年 | 153篇 |
2003年 | 142篇 |
2002年 | 118篇 |
2001年 | 89篇 |
2000年 | 91篇 |
1999年 | 82篇 |
1998年 | 82篇 |
1997年 | 59篇 |
1996年 | 69篇 |
1995年 | 56篇 |
1994年 | 69篇 |
1993年 | 57篇 |
1992年 | 33篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1985年 | 2篇 |
1980年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有5556条查询结果,搜索用时 296 毫秒
91.
92.
93.
A new method is presented for the computation of the gravitational attraction of topographic masses when their height information is given on a regular grid. It is shown that the representation of the terrain relief by means of a bilinear surface not only offers a serious alternative to the polyhedra modeling, but also approaches even more smoothly the continuous reality. Inserting a bilinear approximation into the known scheme of deriving closed analytical expressions for the potential and its first-order derivatives for an arbitrarily shaped polyhedron leads to a one-dimensional integration with – apparently – no analytical solution. However, due to the high degree of smoothness of the integrand function, the numerical computation of this integral is very efficient. Numerical tests using synthetic data and a densely sampled digital terrain model in the Bavarian Alps prove that the new method is comparable to or even faster than a terrain modeling using polyhedra. 相似文献
94.
GPS与INSAR数据融合研究展望 总被引:9,自引:0,他引:9
分析了GPS与INSAR数据融合的必要性与可行性 ,讨论了GPS与INSAR数据融合存在的主要问题 ,进一步探讨了利用GPS数据改善INSAR相位解缠算法 ,利用GPS与INSAR数据融合建立水汽模型和大气层延迟误差改正模型 ,以及GPS高时间分辨率和高平面位置精度与INSAR高空间分辨率和高高程变形精度有效统一的问题。 相似文献
95.
湖南省2001年夏秋季对流云降水潜力数值模拟结果 总被引:5,自引:0,他引:5
应用对流云数值模式模拟了2001年7~9月湖南省三个探空站0000和1200(世界时)462个对流云降水算例.模拟结果表明(1)其中53天的198个算例属于有利人工增雨的天气形势,133个算例的可播度大于零,54个算例的增雨率大于零;(2)7~9月天气形势有利于人工增雨日的算例,对流云平均含水量为575万吨,平均降水效率11.4%;(3)8月降水潜力大于7月,9月降水潜力最小.这表明即使大旱的2001年湖南省夏秋季对流云仍然有一定的增雨潜力. 相似文献
96.
97.
A. Gelencsér A. Hoffer G. Kiss E. Tombácz R. Kurdi L. Bencze 《Journal of Atmospheric Chemistry》2003,45(1):25-33
Current climate models seem to underestimate the flux of solar energy absorbed by the global troposphere. All of these models are constrained with the assumption that cloud droplets consist of pure water. Here we demonstrate in a simple laboratory experiment that aromatic hydroxy-acids which are found in continental fine aerosol can react with hydroxyl radicals under typical conditions prevalent in cloud water influenced by biomass burning. The reactions yield colored organic species which do absorb solar radiation. We also suggest that the products of such reactions may be humic-like substances whose presence in continental aerosol has been confirmed but their source mechanisms are still much sought after. We also attempt to give a first order estimate of the enhancement of water absorption at a visible wavelength under atmospheric conditions. 相似文献
98.
99.
100.
The effect of elevated nitric acid concentrations on cloud particle number concentrations and sizes of mixed phase cirrus cloud (containing both supercooled liquid and frozen ice particles) is studied using a detailed multicomponent condensation model. Our model calculations suggest that high nitric acid volume mixing ratios (VMRs), corresponding to upper tropospheric measurements, can increase the ice crystal number concentrations substantially especially in the case of freezing of non-activated solution droplets (as opposed to freezing of supercooled cloud droplets). This is due to increased droplet sizes caused by nitric acid absorption and the resulting uptake of water. 相似文献