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81.
82.
S. A. Hsu 《Boundary-Layer Meteorology》1979,16(3):93-98
Variation exists in the maximum mixing height (MMH) across the coastal zone because of major differences in heat capacity
between land and sea. By assuming that synoptic and microscale effects are all small as compared to the contribution from
mesoscale temperature differences, a model is proposed to explain this variation. The model states that the variation of the
MMH across the coastal zone is due primarily and is linearly proportional to the difference in maximum temperature between
land and sea. Since the MMH is one of the most important parameters in the computation of distribution and concentration of
aerosols, water vapor, and pollutants, a simple equation is also provided for the operational forecasting of the MMH or the
mixing height over the sea. All inputs into the equation are routinely available. The model has been verified by available
data and a relevant field experiment. 相似文献
83.
Precise tidal gravity recorded with superconducting gravimeters at stations Wuhan (China) and Kyoto (Japan) 总被引:9,自引:0,他引:9
Three long series of tidal gravity observations, totalizing approximately 24 years and recorded with three superconducting
gravimeters, T004, T008, and T009, at stations Wuhan (China) and Kyoto (Japan), are studied. The tidal amplitude factors and
phase differences are determined precisely using Eterna and Nsv techniques. The precision of the main tidal amplitudes is
at the same level of 0.01 μGal. The atmospheric gravity signals are corrected using the coefficients determined with a regression
method between tidal gravity residual and station air pressure. The oceanic gravity signals are modeled based on five global
oceanic models. It is found that the oceanic models developed by the analysis of measurements from Topex/Poseidon altimeters
have the best fit to the superconducting gravimeter measurements, since the observed residuals and the discrepancies between
the amplitude factors and the theoretical tidal models are reduced more significantly. The long-period gravity variations
are dominated by the non-linear drift phenomena of the instruments, and the short-term variations in gravity are due to the
background noise at the stations.
Received: 20 January 2000 / Accepted: 15 September 2000 相似文献
84.
The drop structure will fail as a result of local scoring downstream. This paper discusses the influence of a drop structures’ upstream slope to local scour. Empirical equations of the scour hole were developed by laboratory experiment, theoretical assumptions, and regression analysis. These equations include the maximum scour depth and length during the scouring period, the maximum equilibrium scour depth and length, and the unit width scour rate. The four channel slopes (0%, 2%, 4%, and 6%) before the drop structure has been included in the analysis. A series of laboratory experiments were conducted to obtain 48 groups of experiments and 419 scour hole profiles during the scouring period. The material used in the scour section is uniform non-cohesive and with a median diameter of d 50 = 0.5 mm. The results have been used to develop empirical equations via regression analysis to determine the coefficients of theoretical equations. The high correlation coefficient indicates that the equations developed in this study are suitable for verifying the characteristics of a scour hole at drop structure in the sloped channel. The semi-empirical equation is more accurate than the empirical equation. Compared to a horizontal channel, a sloped channel tends to cause a greater equilibrium maximum scour length, shorter equilibrium maximum scour depth, and faster unit-wide scour rate. 相似文献
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The current low-cost global navigation satellite systems (GNSS) receiver cannot calculate satisfactory positioning results for pedestrian applications in urban areas with dense buildings due to multipath and non-line-of-sight effects. We develop a rectified positioning method using a basic three-dimensional city building model and ray-tracing simulation to mitigate the signal reflection effects. This proposed method is achieved by implementing a particle filter to distribute possible position candidates. The likelihood of each candidate is evaluated based on the similarity between the pseudorange measurement and simulated pseudorange of the candidate. Finally, the expectation of all the candidates is the rectified positioning of the proposed map method. The proposed method will serve as one sensor of an integrated system in the future. For this purpose, we successfully define a positioning accuracy based on the distribution of the candidates and their pseudorange similarity. The real data are recorded at an urban canyon environment in the Chiyoda district of Tokyo using a commercial grade u-blox GNSS receiver. Both static and dynamic tests were performed. With the aid of GLONASS and QZSS, it is shown that the proposed method can achieve a 4.4-m 1σ positioning error in the tested urban canyon area. 相似文献
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作者为明瞭中国温带风暴及台风雨量分布之情形及其与路径之关系,特取民国二十四年夏季(六月至八月)经过中国本部之温带风暴及登陆之台风,逐一分别检讨。先作各日上午六时之风暴路径图,然 相似文献