全文获取类型
收费全文 | 1583篇 |
免费 | 354篇 |
国内免费 | 369篇 |
专业分类
航空 | 1734篇 |
航天技术 | 138篇 |
综合类 | 177篇 |
航天 | 257篇 |
出版年
2024年 | 7篇 |
2023年 | 41篇 |
2022年 | 69篇 |
2021年 | 99篇 |
2020年 | 82篇 |
2019年 | 59篇 |
2018年 | 61篇 |
2017年 | 117篇 |
2016年 | 135篇 |
2015年 | 93篇 |
2014年 | 81篇 |
2013年 | 75篇 |
2012年 | 123篇 |
2011年 | 149篇 |
2010年 | 65篇 |
2009年 | 115篇 |
2008年 | 87篇 |
2007年 | 107篇 |
2006年 | 105篇 |
2005年 | 51篇 |
2004年 | 74篇 |
2003年 | 58篇 |
2002年 | 45篇 |
2001年 | 49篇 |
2000年 | 52篇 |
1999年 | 40篇 |
1998年 | 57篇 |
1997年 | 42篇 |
1996年 | 25篇 |
1995年 | 22篇 |
1994年 | 18篇 |
1993年 | 25篇 |
1992年 | 13篇 |
1991年 | 23篇 |
1990年 | 20篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 1篇 |
排序方式: 共有2306条查询结果,搜索用时 765 毫秒
961.
962.
963.
964.
Aaron L. Gardony Tad T. Brunyé Caroline R. Mahoney Holly A. Taylor 《Spatial Cognition & Computation》2013,13(4):319-350
Abstract Research has demonstrated navigational aids impair spatial memory, but has not considered important spatial cognitive concepts. For example, impairment may stem from spatial perspective switches between route-based aids and survey-based memory assessments. Further, the verbal format of aid instructions may selectively interfere with verbal working memory (VWM). To address these potential explanations, participants navigated desktop virtual environments in a goal-directed manner. In each within-participants condition, participants either navigated with a verbal or tonal aid that presented mixed spatial perspective instructions or without aid. Both aids yielded slight navigational advantages and steep spatial memory costs despite their mixed perspective instructions. The equivalent impairment between information formats suggests navigational aids impair spatial memory by dividing attention rather than selective interference of VWM. 相似文献
965.
针对Turbo码译码过程需要占用大量存储资源的问题,在Max—Log-MAP算法的基础上介绍了一种节省存储资源的译码方法^[1]。通过逆运算在反向递推计算后向路径度量的过程中同时计算部分前向路径度量,节省了近50%前向路径度量的存储资源;通过使用一种性能良好的线性运算代替查表法求得Jacobian(雅可比)对数函数,避免了查找表资源的使用。在避免路径度量溢出进行的归一化操作中,采用了一种有效的方案,进一步节省了计算资源。实验表明,文章方法在有效节省存储资源的同时保证了良好的译码性能。 相似文献
966.
Nicholas A. Giudice Roberta L. Klatzky Jack M. Loomis 《Spatial Cognition & Computation》2013,13(4):287-304
Abstract Participants learned circular layouts of six objects presented haptically or visually, then indicated the direction from a start target to an end target of the same or different modality (intramodal versus intermodal). When objects from the two modalities were learned separately, superior performance for intramodal trials indicated a cost of switching between modalities. When a bimodal layout intermixing modalities was learned, intra- and intermodal trials did not differ reliably. These findings indicate that a spatial image, independent of input modality, can be formed when inputs are spatially and temporally congruent, but not when modalities are temporally segregated in learning. 相似文献
967.
968.
969.
利用硬件,尤其是集成电路来快速实现块匹配运动估计是现在运动图像处理研究的重点之一,而受到目前具体存储器带宽的限制,许多快速算法均无法实现。因此,如何降低对外部存储器带宽的需求直接影响到块匹配的硬件实现,本文首先分析了块匹配运动估计对存储器带宽的需求和数据读取的特点,并据此提出了一种数据复用技术。以少量本地片上存储器为代价大大降低了对外部存储器的带宽需求,利用普通的SDRAM即可快速实现高清晰图像的块匹配运动估计算法,并利用FPGA和普通SDRAM实现了整个运动估计算法。 相似文献
970.
Spatial short-term memory for single target positions is subject to distortions which depend on the spatial layout of visual landmarks. Here, participants had to reproduce the positions of briefly presented targets in the context of three-landmark configurations presented in various orientations. Symmetry properties of distortional patterns were determined by the intrinsic reference system of the landmark configuration as well as by the environment-or body-centered vertical axis. Symmetry was best about the cardinal axes of the landmark system irrespective of their orientation, but symmetry of non-cardinal axes was enhanced when these axes were aligned with the extrinsic vertical. Results are inconsistent with most current models of spatial memory distortions but in line with models explaining distortions in terms of attentional processes in topographical neuronal networks. 相似文献