全文获取类型
收费全文 | 208篇 |
免费 | 65篇 |
国内免费 | 82篇 |
专业分类
测绘学 | 48篇 |
大气科学 | 98篇 |
地球物理 | 51篇 |
地质学 | 69篇 |
海洋学 | 32篇 |
天文学 | 9篇 |
综合类 | 19篇 |
自然地理 | 29篇 |
出版年
2024年 | 4篇 |
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 22篇 |
2012年 | 21篇 |
2011年 | 23篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 14篇 |
2007年 | 11篇 |
2006年 | 14篇 |
2005年 | 13篇 |
2004年 | 15篇 |
2003年 | 8篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 17篇 |
1999年 | 6篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 2篇 |
排序方式: 共有355条查询结果,搜索用时 15 毫秒
91.
对目前比较流行的GPS模块的输出数据进行测量,利用误差理论与数据处理方法对数据进行处理,并用灵图地图对所测数据的准确性进行判断,将处理后的数据与实际里程进行转换,得出实际里程误差。对误差原因进行了分析。结果表明:该分析方法正确,GPS模块所测数据可靠,为今后进行GPS接收机的研制工作积累了经验。 相似文献
92.
93.
Relationship Between an Abrupt Drought-Flood Transition over Mid-Low Reaches of the Yangtze River in 2011 and the Intraseasonal Oscillation over Mid-High Latitudes of East Asia
下载免费PDF全文
![点击此处可从《Acta Meteorologica Sinica》网站下载免费的PDF全文](/ch/ext_images/free.gif)
NCEP/NCAR daily reanalysis data and Chinese daily gridded precipitation data are used to study the relationship between an aprupt drought-flood transition over the mid-low reaches of the Yangtze River in 2011 and the intraseasonal oscillation (ISO; 30-60 days) in the mid-high latitude meridional circulation of the upper troposphere over East Asia. The abrupt transition from drought to flood occurs in early June. The first two recovered fields of the complex empirical orthogonal function show that northward-propagating westerlies from low latitudes converge with southward-propagating westerlies from high latitudes over the mid-low reaches of the Yangtze River (MLRYR) in mid-late May. The timing of this convergence corresponds to the flood period in early-mid June. The ISO index is significantly and positively correlated with rainfall over the MLRYR. During the dry phase (before the transition), the upper troposphere over the MLRYR is characterized by cyclonic flow, easterly winds, and convergence. The regional circulation is dominated by a wave train with a cyclone over east of Lake Baikal, an anticyclone over northern China, and a cyclone over the MLRYR. During the wet phase, the situation is reversed. The configuration of the wave train during the dry phase favors the southward propagation of westerly wind disturbances, while the configuration of the wave train during the wet phase favors the development and maintenance of a pumping effect and sustained ascending motions over the MLRYR. 相似文献
94.
Soil respiration is CO2 evolution process from soil to atmosphere, mainly produced by soil micro-organism and plant roots. It is affected not only
by biological factors (vegetation, micro-organism, etc.) and environmental factors (temperature, moisture, pH, etc.), but
also more and more strongly by man-made factors. Based on literature survey, main factors affecting soil respiration were
reviewed. The relationship of soil respiration to latitude and to mean annual temperature were analyzed by using the data
measured from forest vegetation in the world. As a result, soil respiration rate decreased exponentially with an increase
of latitude, and increased with increasing temperature. Following the relationship between soil respiration and temperature,
Q10 value (law of Van Hoff) was obtained as 1.57 in the global scale.
This project was supported by National Natural Science Foundation of China to FJY (No. 3940003). 相似文献
95.
为研究利用数字天顶摄影定位方法测定地球自转参数的可行性,结合数字天顶摄影定位原理及时空基准转换差异,详细分析多台站地球自转参数测定及单台站UT1-UTC测定原理,并推导给出相关数学模型。模拟仿真及实测验证结果表明,采用目前高精度天顶摄影定位系统(精度0.05″),通过全国范围内的合理布站,可实现UT1-UTC参数±5 ms、极移参数±0.06″的测量精度。单台站UT1-UTC实测精度为5~8 ms,可满足特定军事工程需求,同时可为多台站联合解算ERP参数提供数据支撑。研究成果可为我国开展地球自转参数测定提供理论参考。 相似文献
96.
本文在简述非差非组合理论模型以及参数估计的基础上,结合IGS/MGEX精密轨道和精密钟差等产品,对地处低纬度高海拔的云南地区进行了BDS/GPS/GLONASS系统非差非组合PPP性能分析。通过试验研究分析得出,在该地区单系统定位模式下可视卫星数为BDS>GPS>GLONASS;组合模式下,BDS系统与其他系统的可视卫星数基本都大于GPS跟GLONASS系统组合,可视卫星数依次为GRC>GC>RC>GR,PDOP值依次为GR>RC>GC>GRC。其中,组合模式下可视卫星数基本是单系统可视卫星数的2~3倍,表明在低纬度高海拔地区BDS系统的贡献大于其他两系统。多系统组合能够获得更好的卫星几何构型,较单系统有显著的优越性。在定位精度上,7种组合模式下定位精度基本能达到厘米至毫米级。 相似文献
97.
98.
1INTRODUCTIONTropicalcyclones(tobedesignatedTChereafter)actwithsignificantlatitudinaldifference[1],someofwhichhavebeenwelldocumented.Forinstance,TCisavortexsystemthatformsandmaintainswiththesupportofsomeextentofCoriolisforce,whichisweakinareasneartheequator(southof4N)andenableslittleTCactivity[2].AsTCismainlysuppliedbylatentheating,higherSSTissuretobeadvantageoustothegenerationanddevelopmentofTC;thesummertimeSSTdecreaseswithincreasinglatitudeinthenorthwesternPacific[3],beingnear26.… 相似文献
99.
Joaquim Alves Gaspar 《The Cartographic journal》2013,50(4):318-324
In this paper, the results of a cartometric analysis of a number of Portuguese and Spanish charts of the sixteenth and seventeenth centuries are presented and conclusions are drawn concerning the length of the degree of latitude adopted in the Iberian nautical cartography of the Renaissance. Under the light of what we know about the navigational and charting methods of the time, a new interpretation of the textual and cartographic sources is proposed. Rather than being the result of technical considerations or precise measurements, the adoption of the various standards during this long period appears to be no more than the echoes of the traditional models of the Earth and of the political disputes between Portugal and Spain. 相似文献
100.