全文获取类型
收费全文 | 161篇 |
免费 | 11篇 |
国内免费 | 14篇 |
专业分类
测绘学 | 59篇 |
大气科学 | 22篇 |
地球物理 | 19篇 |
地质学 | 32篇 |
海洋学 | 13篇 |
天文学 | 17篇 |
综合类 | 14篇 |
自然地理 | 10篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 1篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 17篇 |
2013年 | 18篇 |
2012年 | 10篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有186条查询结果,搜索用时 296 毫秒
161.
用改进的SPEA求解轨道转移的时间-能量极小化问题 总被引:3,自引:0,他引:3
提出了改进的SPEA,这是一种多目标进化算法,适于求解大尺度空间的多目标优化的Pareto最优解,并应用于求解轨道转移的时间—能量极小化问题,计算结果表明算法的有效性。 相似文献
162.
针对航空磁测数据处理中存在的飞机在飞行高度上起伏变化的问题,传统的Taylor多项式模型在构建局域地磁场模型时,通常只选择平面经纬度方向坐标作为变量,而忽略了飞行高度的变化对建模结果的影响。这里引入顾及飞行高度变化影响的Taylor多项式方法构建地磁场模型,分别利用模拟和实测的航空磁测数据,研究了忽略和顾及飞行高度影响的Taylor多项式法;并分析了截断阶数与中误差的关系。从而得出顾及飞行高度影响的方法可以明显地提高建模的精度和改善模型的边界效应的结论。 相似文献
163.
近几年,进入公路勘察设计规范更新高峰期,鉴于规范颁布后即刻生效的特殊性,如何有效的解决新版规范的执行与传统设计思路的矛盾以及促进勘察设计工作的顺利进展是本文试图探讨的问题。 相似文献
164.
Framed by the UK Government’s efforts to combat social exclusion by encouraging a shift from welfare to work through (re)training, this paper explores the types of training courses being offered to and taken by women with young children in West London. Drawing upon qualitative research, the paper explores the actual and desired uptake of ‘body training’ courses among mothers, linked, in part, to the current ‘body work’ skills gap in the local economy. The encouragement given to women and the interest they have in engaging in ‘body training’ is, we suggest, linked to the discursive construction and performance of a highly feminised and, often, maternal identity, which emphasises women’s caring role and the caring self. By probing the body/training nexus through the motivations and choices of mothers in West London the paper raises questions about gender identity and stereotyping in relation to training-for-work policies and the role of training in (re)inforcing the woman-body coupling within Western dualistic thought. 相似文献
165.
166.
A total of 6085 adult Trichoptera (excluding Hydroptilidae) representing 12 families, 31 genera, and 56 species were collected by a combination of Malaise net and light trapping from July 1998 to July 1999 at three hill‐country sites of contrasting catchment land use (100% native forest, a pasture site with native forest headwaters, and 100% pasture) in the Waikato, northern New Zealand. Forty‐eight species of Trichoptera were collected from Malaise nets and 45 species from light traps. Eleven species of Trichoptera were only ever collected from the Malaise nets and seven species from only the light traps. At the native forest site, Malaise nets collected more species and taxa of conservation interest than did light traps, possibly reflecting diurnal activity or non‐attraction to light by some species. Several species of Trichoptera showed site specificity and most of these were found at the native forest site. Twenty‐eight species were active for at least 6 months of the year with at least four species active all year. A minimum overnight air temperature of at least 9°C was required to induce Trichoptera flight activity, but large‐scale flight activity may require temperatures greater than 14°C. Trichoptera with free‐living and net spinning larvae exhibited extended flight periods, and for three species examined there were bi‐modal activity peaks. Adult caddisflies with cased larvae which grazed on epilithic food resources generally had reduced flight periods and one species had a well‐defined, synchronous periodicity. These findings suggest flight periodicity may partly be a functional response to larval food availability. 相似文献
167.
生态环境脆弱区工程地质研究是工程地质学科必须面对的一个重要领域。作者指出,工程地质学应当夯实学科基础,吸取相关学科理论,重塑工程地质理论与实践,出精品工程,重视人才培养。 相似文献
168.
基于DEM的航空摄影技术设计方法 总被引:2,自引:0,他引:2
航空摄影是快速获取和更新基础地理信息的重要技术手段之一 ,其技术设计直接影响航摄成果直至最终航测成图的质量。本文通过分析目前航空摄影技术设计中存在的问题 ,提出了基于数字高程模型的计算机辅助航空摄影技术设计的方法。该方法以基础地理信息尤其是数字高程模型为数据支撑 ,利用 GIS的可视化技术和多源数据的整合能力 ,实现航空摄影的计算机辅助技术设计 ,旨在规范航空摄影技术设计工作 ,提高航空摄影技术设计水平和工作效率 ,确保航摄成果质量 相似文献
169.
本文结合杭州干部培训中心继续教育的实践,探讨了继续教育中开发科技人员创造力的途径。指出科技人员的继续教育要正确处理好传授知识和培养科研能力的关系,着眼于能力的培养。培训内容要注重先进性和实用性,注意学科间的交叉渗透。培训方法要采用有利于激发学员创造性思维的形式,在继续教育中建立起新型的创造教育的观念。 相似文献
170.
A random walk model to describe the dispersion of pollutants in shallow water is developed. By deriving the Fokker-Planck equation, the model is shown to be consistent with the two-dimensional advection-diffusion equation with space-varying dispersion coefficient and water depth. To improve the behaviour of the model shortly after the deployment of the pollutant, a random flight model is developed too. It is shown that over long simulation periods, this model is again consistent with the advection-diffusion equation. The various numerical aspects of the implementation of the stochastic models are discussed and finally a realistic application to predict the dispersion of a pollutant in the Eastern Scheldt estuary is described. 相似文献