全文获取类型
收费全文 | 5438篇 |
免费 | 1000篇 |
国内免费 | 1536篇 |
专业分类
测绘学 | 1032篇 |
大气科学 | 2464篇 |
地球物理 | 1234篇 |
地质学 | 788篇 |
海洋学 | 1157篇 |
天文学 | 272篇 |
综合类 | 388篇 |
自然地理 | 639篇 |
出版年
2024年 | 29篇 |
2023年 | 97篇 |
2022年 | 188篇 |
2021年 | 239篇 |
2020年 | 252篇 |
2019年 | 366篇 |
2018年 | 245篇 |
2017年 | 291篇 |
2016年 | 289篇 |
2015年 | 315篇 |
2014年 | 409篇 |
2013年 | 446篇 |
2012年 | 475篇 |
2011年 | 458篇 |
2010年 | 320篇 |
2009年 | 379篇 |
2008年 | 340篇 |
2007年 | 436篇 |
2006年 | 355篇 |
2005年 | 310篇 |
2004年 | 243篇 |
2003年 | 213篇 |
2002年 | 187篇 |
2001年 | 153篇 |
2000年 | 145篇 |
1999年 | 133篇 |
1998年 | 94篇 |
1997年 | 85篇 |
1996年 | 98篇 |
1995年 | 72篇 |
1994年 | 63篇 |
1993年 | 71篇 |
1992年 | 51篇 |
1991年 | 40篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有7974条查询结果,搜索用时 352 毫秒
201.
利用机载GNSS反射信号反演海面风速的研究 总被引:2,自引:0,他引:2
全球卫星导航定位系统的反射信号(GNSS-R)遥感技术作为一种新型的、低成本的、高机动性的海面微波遥感测风技术,与其他测风手段优势互补,可以增加测风手段的多样性,弥补局部测风手段不足的状况。研究了接收机在机载高度时,GPS反射信号功率理论模型四部分函数的性质,在此基础之上,数值模拟了机载高度下理论相关功率波形,基于海面风速对波形峰值与后沿的影响,提出了一种能够兼顾所有理论波形信息的二维插值风速反演方法。利用该方法,结合实测机载数据对海面风速进行反演,反演的风速均值与附近测站风速均值相差为1.4 m/s,与浮标数据相一致。 相似文献
202.
Evaluation of ENVISAT ASAR data for sea surface wind retrieval in Hong Kong coastal waters of China 总被引:2,自引:1,他引:1
The C-band wind speed retrieval models, CMOD4, CMOD - IFR2, and CMOD5 were applied to retrieval of sea surface wind speeds from ENVISAT (European environmental satellite) ASAR (advanced synthetic aperture radar) data in the coastal waters near Hong Kong during a period from October 2005 to July 2007. The retrieved wind speeds are evaluated by comparing with buoy measurements and the QuikSCAT (quick scatterometer) wind products. The results show that the CMOD4 model gives the best performance at wind speeds lower than 15 m/s. The correlation coefficients with buoy and QuikSCAT winds are 0.781 and 0.896, respectively. The root mean square errors are the same 1.74 m/s. Namely, the CMOD4 model is the best one for sea surface wind speed retrieval from ASAR data in the coastal waters near Hong Kong. 相似文献
203.
The variations of current circulation, salt intrusion, and vertical stratification under different river flow and wind conditions in the Pamlico River Estuary (PRE) were investigated in this paper using a three-dimensional numerical model. The model was calibrated and verified against water level variation, temperature, and salinity variations during 2003 and 2001, respectively. Eight sensitivity tests were conducted with different river flow and wind conditions specified in the model. Model results show that salinity intruded further upstream under scenarios with low flow, downriver local wind, and remote-wind-caused water level set-up conditions. In contrast, the responses of salinity stratification to different environmental forcing functions were different in different portions of the estuary. Salinity stratification was enhanced under high flow condition at the lower part of the estuary, under upriver wind near the river mouth, under downriver wind at the upstream to middle portion of the estuary, and under remote-wind-caused water level set-up condition at the majority of the estuary except near the river mouth. Model results also show that across-channel wind tended to reduce salt intrusion and salinity stratification in the PRE through increased vertical mixing. 相似文献
204.
In order to investigate the effect of wind input and whitecapping dissipation on the simulation of typhoon-waves, three experiments are conducted with the latest version of SWAN (Simulating WAves Nearshore) model. The three experiments adopt the Komen, Janssens, and Westhuysen expressions for wind input and whitecapping dissipation, respectively. Besides the above-mentioned source tems, other parameterization schemes in these experiments are the same. It shows that the experiment with the Westhuysen expression result in the least simulation errors while that with the Janssens expression has the most. The results from the experiments with Komen and Westhuysen expressions show that the differenees in significant wave height (SWH) have a good correlation with the differences in dissipation energy caused by whiteeapping. This indicates that the whitecapping dissipation source term plays an important role in the resultant differences of the simulated SWH between the two experiments. 相似文献
205.
206.
207.
208.
A real-time, event-triggered storm surge forecasting system for the state of North Carolina 总被引:3,自引:0,他引:3
A new real-time, event-triggered storm surge prediction system has been developed for the State of North Carolina to assist emergency managers, policy-makers and other government officials with evacuation planning, decision-making and resource deployment during tropical storm landfall and flood inundation events. The North Carolina Forecast System (NCFS) was designed and built to provide a rapid response assessment of hurricane threat, accomplished by driving a high-resolution, two-dimensional, depth-integrated version of the ADCIRC (Advanced Circulation) coastal ocean model with winds from a synthetic asymmetric gradient wind vortex. These parametric winds, calculated at exact finite-element mesh node locations and directly coupled to the ocean model at every time step, are generated from National Hurricane Center (NHC) forecast advisories the moment they are inserted into the real-time weather data stream, maximizing the number of hours of forecast utility. Tidal harmonic constituents are prescribed at the open water boundaries and applied as tidal potentials in the interior of the ocean model domain. A directional surface roughness parameterization that modulates the wind speed at a given location based on the types of land cover encountered upwind, a forest canopy sheltering effect, and a spatially varying distribution of Manning’s–n friction coefficient used for computing the bottom/channel bed friction are also included in the storm surge model. Comparisons of the simulated wind speeds and phases against their real meteorological counterparts, of model elevations against actual sea surface elevations measured by NOAA tide gauges along the NC coast, and of simulated depth-averaged current velocities against Acoustic Doppler Current Profiler (ADCP) data, indicate that this new system produces remarkably realistic predictions of winds and storm surge. 相似文献
209.
???????????????????????????????????????嶫?????????GPS????????????????????????????????λ??ó?????????β???????仯???????????2001???????8.1???????????β?????????д?????μ?仯????????仯?????????ж??????????С????????????????????????????????????????8.1????????????????????????????????о????????????????β???????п??????????????????? 相似文献
210.
����̨ˮ�¡�ˮ��쳣���봨8.0�������ϵ̽�� 总被引:1,自引:0,他引:1
刘冬英 《大地测量与地球动力学》2008,28(6):53-55
???????8.0???????????????????????????????н?1 800???????????????????o??????????????????????????????????????????????8.0???????й?? 相似文献