全文获取类型
收费全文 | 1346篇 |
免费 | 195篇 |
国内免费 | 286篇 |
专业分类
测绘学 | 122篇 |
大气科学 | 68篇 |
地球物理 | 381篇 |
地质学 | 170篇 |
海洋学 | 823篇 |
天文学 | 27篇 |
综合类 | 190篇 |
自然地理 | 46篇 |
出版年
2024年 | 9篇 |
2023年 | 11篇 |
2022年 | 34篇 |
2021年 | 47篇 |
2020年 | 56篇 |
2019年 | 70篇 |
2018年 | 59篇 |
2017年 | 49篇 |
2016年 | 41篇 |
2015年 | 64篇 |
2014年 | 47篇 |
2013年 | 83篇 |
2012年 | 75篇 |
2011年 | 83篇 |
2010年 | 61篇 |
2009年 | 61篇 |
2008年 | 73篇 |
2007年 | 92篇 |
2006年 | 78篇 |
2005年 | 98篇 |
2004年 | 76篇 |
2003年 | 77篇 |
2002年 | 55篇 |
2001年 | 51篇 |
2000年 | 59篇 |
1999年 | 45篇 |
1998年 | 27篇 |
1997年 | 39篇 |
1996年 | 29篇 |
1995年 | 32篇 |
1994年 | 43篇 |
1993年 | 29篇 |
1992年 | 20篇 |
1991年 | 15篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1954年 | 1篇 |
排序方式: 共有1827条查询结果,搜索用时 15 毫秒
91.
TOPEX/POSEIDON altimeter data from October 1992 to June 2002 are used to calculate the global barotropic M2 tidal currents using long-term tidal harmonic analysis. The tides calculated agree well with ADCP data obtained from the South China Sea (SCS). The maximum tide velocities along the semi-major axis and semi-minor axis can be computed from the tidal ellipse. The global distribution of M2 internal tide vertical energy flux from the sea bottom is calculated based on a linear internal wave generation model. The global vertical energy flux of M2 internal tide is 0.96 TW, with 0.36 TW in the Pacific, 0.31 TW in the Atlantic and 0.29 TW in the Indian Ocean, obtained in this study. The total horizontal energy flux of M2 internal tide radiating into the open ocean from the lateral boundaries is 0.13 TW, with 0.06 TW in the Pacific, 0.04TW in the Atlantic, and 0.03 TW in the Indian Ocean. The result shows that the principal lunar semi-diurnal tide M2 provides enough energy to maintain the large-scale thermohaline circulation of the ocean. 相似文献
92.
93.
The diurnal cycle of the tropospheric zenith total delay (ZTD) is one of the most obvious signals for the various physical
processes relating to climate change on a short time scale. However, the observation of such ZTD oscillations on a global
scale with traditional techniques (e.g. radiosondes) is restricted due to limitations in spatial and temporal resolution.
Nowadays, the International GNSS Service (IGS) provides an important data source for investigating the diurnal and semidiurnal
cycles of ZTD and related climatic signals. In this paper, 10 years of ZTD data from 1997 to 2007 with a 2-hour temporal resolution
are derived from global positioning system (GPS) observations taken at 151 globally distributed IGS reference stations. These
time series are used to investigate diurnal and semidiurnal oscillations. Significant diurnal and semidiurnal oscillations
of ZTD are found for all GPS stations used in this study. The diurnal cycles (24 hours period) have amplitudes between 0.2
and 10.9 mm with an uncertainty of about 0.5 mm and the semidiurnal cycles (12 h period) have amplitudes between 0.1 and 4.3 mm
with an uncertainty of about 0.2 mm. The larger amplitudes of the diurnal and semidiurnal ZTD cycles are observed in the low-latitude
equatorial areas. The peak times of the diurnal cycles spread over the whole day, while the peak value of the semidiurnal
cycles occurs typically about local noon. These GPS-derived diurnal and semidiurnal ZTD signals are similar with the surface
pressure tides derived from surface synoptic pressure observations, indicating that atmospheric tides are the main driver
of the diurnal and semidiurnal ZTD variations. 相似文献
94.
The scarcity of tide gauges in a global scale and the variability of the tidal levels along contiguous coasts mainly due to changing hydrographic conditions make the determination of tidal levels, especially of the Mean Sea Level, not an easy task. Determination of such levels with a precision of about 10 cm, necessary for most coastal engineering works, is usually based on records of temporary tide gauges or on geomorphological techniques. In this paper we present an alternative approach permitting to accurately identify tidal levels with a precision suitable for civil engineering applications based on biological observations on rocky shores, including breakwaters and quays. More specifically, we present evidence that the biological zonation, i.e. the distribution of coastal species in well-defined sub-horizontal belts, is practically insensitive to seasonal and other small-scale fluctuations of the sea level and is clearly related to certain levels, mostly the Mean Low Water (MLW). This approach, somewhat similar to what has been used in the past (for instance for the determination of the geodetic vertical datum in the Republic of Venice, Italy, till approximately AD 1800), permits direct determination of the Mean Sea Level or of other tidal levels on the basis of biological observations without statistical analyses of tide-gauge records with an accuracy of 5–10 cm, especially in microtidal, low-energy coasts. 相似文献
95.
Hiroaki Sasaki Akihiko Tanaka Mitsunori Iwataki Yasuharu Touke Eko Siswanto Chun Knee Tan Joji Ishizaka 《Journal of Oceanography》2008,64(4):511-523
Remote sensing reflectance [R
rs(λ)] and absorption coefficients of red tides were measured in Isahaya Bay, southwestern Japan, to investigate differences in
the optical properties of red tide and non-red tide waters. We defined colored areas of the sea surface, visualized from shipboard,
as “red tides”. Peaks of the R
rs(λ) spectra of non-red tide waters were at 565 nm, while those of red tides shifted to longer wavelengths (589 nm). The spectral
shape of R
rs(λ) was close to that of the reciprocal of the total absorption coefficient [1/a(λ)], implying that the R
rs(λ) peak is determined by absorption. Absorption coefficients of phytoplankton [a
ph(λ)], non-pigment particles and colored dissolved organic matter increased with increasing chlorophyll a concentration (Chl a), and those coefficients were correlated with Chl a for both red tide and non-red tide waters. Using these relationships between absorption coefficients and Chl a, variation in the spectrum of 1/a(λ) as a function of Chl a was calculated. The peak of 1/a(λ) shifted to longer wavelengths with increasing Chl a. Furthermore, the relative contribution of a
ph(λ) to the total absorption in red tide water was significantly higher than in non-red tide water in the wavelength range 550–600
nm, including the peak. Our results show that the variation of a
ph(λ) with Chl a dominates the behavior of the R
rs(λ) peak, and utilization of R
rs(λ) peaks at 589 and 565 nm may be useful to discriminate between red tide and non-red tide waters by remote sensing. 相似文献
96.
VAV��ETERNA��ϫ���������ıȽϺ��о� 总被引:3,自引:3,他引:0
??VAV??ETERNA??????????????????????????????????????????????????????????????????????人???????????????з????????????, ??????VAV?????????????????ETERNAС,??????????????????????????????????????????????????????????VAV??ETERNA????????????? 相似文献
97.
利用双阳台水管观测资料检测地球自由振荡 总被引:2,自引:2,他引:0
基于双阳台水管倾斜仪的数字化观测资料,利用功率谱密度估计方法,在没有对资料进行去固体潮处理的情况下,准确获得了2004年12月26日苏门答腊大地震激发的0S3~0S31基频球型自由振荡。并与PREM模型的理论自由振荡周期进行了对比,发现实测振荡周期与PREM预测的振荡周期相吻合,除0S3、0S4振型的观测周期和PREM模型理论周期的相对误差大于0.3%外,其他振型的观测周期和PREM模型理论周期的相对误差大都集中在0.1%左右。同时还检测到了5个谐频球型振荡和8个环型振荡。 相似文献
98.
99.
100.
前人在讨论水深对内潮能通量影响的时候得出结论:有限深海洋中海面对内潮的反射使得正压潮向内潮的能量转化相比较无限深海的情况显著降低,对于选定的地形,在无限深海假定下得到的能通量是该地形上内潮能通量的上限。鉴于前人所研究的基本上都是平滑的地形,而实际的海洋地形总是比较粗糙的,本文探讨了粗糙地形上内潮能通量随水深的变化。选取了弦函数地形、随机白噪声地形、弦函数地形叠加在高斯地形之上、随机白噪声地形叠加在高斯地形之上和随机白噪声地形与弦函数地形同时叠加在高斯地形之上5种情况进行了研究,发现对于这5种情况,都存在海洋有限深时的能通量大于无限深假定时的能通量,这说明前人得出的"有限深海洋中海面对内潮的反射使得正压潮向内潮的能量转化相比较无限深海的情况显著降低"的结论对于粗糙地形并不适用。 相似文献