全文获取类型
收费全文 | 351篇 |
免费 | 21篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 53篇 |
地球物理 | 92篇 |
地质学 | 92篇 |
海洋学 | 81篇 |
天文学 | 20篇 |
综合类 | 8篇 |
自然地理 | 15篇 |
出版年
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 13篇 |
2014年 | 10篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 20篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 24篇 |
2007年 | 22篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1959年 | 1篇 |
1954年 | 1篇 |
1953年 | 1篇 |
1942年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有384条查询结果,搜索用时 15 毫秒
351.
352.
A wave transformation model (RIDE) was enhanced to include the process of wave breaking energy dissipation in addition to water wave refraction, diffraction, reflection, shoaling, bottom friction, and harbor resonance. The Gaussian Elimination with partial Pivoting (GEP) method for a banded matrix equation and a newly developed bookkeeping procedure were used to solve the elliptic equation. Because the bookkeeping procedure changes the large computer memory requirements into a large hard-disk-size requirement with a minimum number of disk I/O, the simple and robust GEP method can be used in personal computers to handle realistic applications. The computing time is roughly proportional to N1.7, where N is the number of grid points in the computing domain. Because the GEP method is capable of solving many wave conditions together (limited by having the same wave period, no bottom friction and no breaking), this model is very efficient compared to iteration methods when simulating some of the wave transformation process. 相似文献
353.
The accuracy of predicting wave transformation in the nearshore is very important to wave hydrodynamics, sediment transport and design of coastal structures. An efficient numerical model based on the time-dependent mild-slope equation is presented in this paper for the estimation of wave deformation across the surf zone. This model incorporates an approximate nonlinear shoaling formula and an energy dissipation factor due to wave breaking to improve the accuracy of the calculation of wave height deformation prior to wave breaking and also in the surf zone. The model also computes the location of first wave breaking, wave recovery and second wave breaking, if physical condition permits. Good agreement is found upon comparison with experimental data over several one-dimensional beach profiles, including uniform slope, bar and step profiles. 相似文献
354.
An investigation on internal solitary waves in a two-layer fluid: Propagation and reflection from steep slopes 总被引:2,自引:0,他引:2
Chen-Yuan Chen John Rong-Chung Hsu Min-Hung Cheng Hsin-Hsun Chen Ching-Feng Kuo 《Ocean Engineering》2007,34(1):171-184
Experimental investigations on internal solitary wave (ISW) propagation and their reflection from a smooth uniform slope were conducted in a two-layered fluid system with a free surface. A 12-meter-long wave flume was in use which incorporated with: (1) a movable vertical gate for generating ISW; (2) six ultrasonic probes for measuring the fluctuation of an ISW; and (3) a steep uniform slope (from one of θ=30°, 50°, 60°, 90°, 120° and 130°) much greater than those ever published in the literature. This paper presents the wave profile properties of the ISW recorded in the flume and their nonlinear features in comparison with the existing Korteweg de Vries (KdV) and modified Korteweg-de Vries (MKdV) theories. Experimental results show that the KdV theory is suitable for most small-amplituded ISWs and MKdV theory is appropriate for the reflected ISWs from various uniform slopes. In addition, both the amplitude-based reflection coefficient and reflected energy approach a constant value asymptotically when plotted against the slope and the characteristic length ratio, respectively. The reflected wave amplitudes calculated from experimental data agree well with those reported elsewhere. The optimum reflection coefficient is found within the limit of 0.85 for wave amplitude, among the test runs from steep normal slope of 30° to inverse angle of 130°, and around 0.75 for the reflected wave energy, produced by an ISW on a vertical wall. 相似文献
355.
HSU HouTse 《中国科学D辑(英文版)》2007,50(6):918-926
According to the features of spatial spectrum of the dynamic ocean topography (DOT),wavelet filter is proposed to reduce short-wavelength and noise signals in DOT. The surface geostrophic currents calculated from the DOT models filtered by wavelet filter in global and Kuroshio regions show more detailed information than those from the DOT models filtered by Gaussian filter. Based on a satellite gravity field model (CG01C) and a gravity field model (EGM96),combining an altimetry-derived mean sea surface height model (KMSS04),two mean DOT models are estimated. The short-wavelength and noise signals of these two DOT models are removed by using wavelet filter,and the DOT models asso-ciated global mean surface geostrophic current fields are calculated separately. Comparison of the surface geostrophic currents from CG01C and EGM96 model in global,Kuroshio and equatorial Pacific regions with that from oceanography,and comparison of influences of the two gravity models errors on the precision of the surface geostrophic currents velocity show that the accuracy of CG01C model has been greatly improved over pre-existing models at long wavelengths. At large and middle scale,the surface geostrophic current from satellite gravity and satellite altimetry agrees well with that from oceanography,which indicates that ocean currents detected by satellite measurement have reached relatively high precision. 相似文献
356.
Sumatra-Andaman Large Earthquake on Dec. 26, 2004 generated not only the Indian Ocean Tsunami but also the Earth’s free oscillations
(EFO). The signals of Earth’s free oscillations were perfectly recorded by the superconducting gravimeter C0-32 at Wuhan station
in China. After the pre-treatment and spectral analysis on the observational data from Wuhan station, we obtained more than
ninety EFO modes including 42 fundamental modes, 2 radial modes and 49 harmonic modes. On the basis of the discussions on
some observed harmonic modes and abnormal splitting phenomena, we considered that the real rigidity might be lower than the
theoretical prediction of PREM model in the inner core and however the anisotropy of compressive wave was brightly higher
than the present estimations in the inner core. This suggested that the anisotropy of the inner core could be much more complicated
than our present understanding, and there might be some new geophysical phenomena in the formation process of the inner core.
Supported jointly by the National Natural Science Foundation of China (Grant Nos. 40404005 and 40374029) and the Excellent
Prize of President Scholarship and Hundred Talents Program of the Chinese Academy of Sciences 相似文献
357.
358.
Sun, climate, hunger, and mass migration 总被引:9,自引:1,他引:8
Kenneth J. Hsu 《中国科学D辑(英文版)》1998,41(5):449-472
Paleoclimatic studies indicate four epochs of global cooling during the last 4 000 years, i. e. during the few centuries before
and after 2000 BC, 800 BC, 400 AD, and 1 600 AD; the quasiperiodicity corresponds to cyclic variation of solar activity. Global
temperature changes influenced regional precipitation patterns: Northern Europe was wetter while the middle- and low-latitude
lands were more arid during colder epochs. Both sets of cold climatical conditions were unfavorable for agricultural production.
Historical records show that large demographic movements in history took place because of crop failures and mass starvation,
rather than escaping from war zones. The “wandering” of the Germanic tribes during the first two or three centuries of the
Christian Era is one example. Whereas the accelerated release of carbon dioxide from the burning of fossil fuels is ultimately
to cause global warming, historical evidence indicates, however, that global warming has been on the whole a blessing to mankind.
Global cooling, on the other hand, has curtailed agricultural production and has led to famines and mass migrations of people.
Perhaps the most important task at the present is not so much computer-modelling of greenhouse effect on global climate, but
water-management and agricultural researches to insure food-supply for an everincreasing world population. 相似文献
359.
He-Ping Sun Gerhard Jentzsch Jian-Qiao Xu Hou-Ze Hsu Xiao-Dong Chen Jiang-Cun Zhou 《Journal of Geodynamics》2004,38(3-5):451
The long series tidal gravity observations from 1997 to 2002 recorded with C032 superconducting gravimeter (SG) at station Wuhan/China are used in order to study the Earth's geodynamics. The tidal gravity parameters are determined precisely using Eterna software package after careful data pre-processing. The Earth's free core nutation (FCN) resonant parameters (eigenperiods, quality factors and resonant strengths) are determined accurately. The results show the determined eigenperiod to be 431.0 sidereal days with an accuracy of ±1.81%, the quality factor is a negative one as of −7002, and the resonance strength can be explained by the elastic property of the Earth's mantle. The discrepancy of the eigenperiods when using various ocean models can amount to ±1.8%. The 30 sidereal days difference between the determined eigenperiod in this paper and the one in theoretical computation given by Wahr and Bergen can be explained by the real dynamic ellipticity of the Earth's liquid core, i.e., it is about 5% larger than the one under the hydrostatic equilibrium assumption. 相似文献
360.
能量在大气中是一个主要的因素,大气中一切的现象之所以能发生,都是因为大气有适当的能量的供给和变化。大气中能量的式样很多,不同式样的能力有不同的重要性,研究各种式样的能力的多寡和它的变化是很有意义的,因为大气环流 相似文献