全文获取类型
收费全文 | 903篇 |
免费 | 180篇 |
国内免费 | 251篇 |
专业分类
测绘学 | 25篇 |
大气科学 | 244篇 |
地球物理 | 368篇 |
地质学 | 402篇 |
海洋学 | 82篇 |
天文学 | 14篇 |
综合类 | 43篇 |
自然地理 | 156篇 |
出版年
2024年 | 5篇 |
2023年 | 13篇 |
2022年 | 19篇 |
2021年 | 33篇 |
2020年 | 24篇 |
2019年 | 30篇 |
2018年 | 23篇 |
2017年 | 40篇 |
2016年 | 33篇 |
2015年 | 37篇 |
2014年 | 57篇 |
2013年 | 73篇 |
2012年 | 71篇 |
2011年 | 53篇 |
2010年 | 47篇 |
2009年 | 53篇 |
2008年 | 69篇 |
2007年 | 75篇 |
2006年 | 47篇 |
2005年 | 40篇 |
2004年 | 45篇 |
2003年 | 34篇 |
2002年 | 46篇 |
2001年 | 32篇 |
2000年 | 39篇 |
1999年 | 31篇 |
1998年 | 44篇 |
1997年 | 23篇 |
1996年 | 25篇 |
1995年 | 18篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 23篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1978年 | 6篇 |
1977年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有1334条查询结果,搜索用时 662 毫秒
381.
梅岩辉 《物探化探计算技术》2007,(Z1)
根据重力位、重力异常、磁位和磁异常公式,应用泊松关系,通过严格的公式推导,给出了重力位、重力异常、磁位和磁异常之间的数学关系,从而使重磁异常正演计算表达式包含于简单的规则之中,揭示出均质多面体重磁异常正演理论的一致性。 相似文献
382.
Gravity data are the results of gravity force field interaction from all the underground sources. The objects of detection
are always submerged in the background field, and thus one of the crucial problems for gravity data interpretation is how
to improve the resolution of observed information. The wavelet transform operator has recently been introduced into the domain
fields both as a filter and as a powerful source analysis tool. This paper studied the effects of improving resolution of
gravity data with wavelet analysis and spectral method, and revealed the geometric characteristics of density heterogeneities
described by simple shaped sources. First, the basic theory of the multiscale wavelet analysis and its lifting scheme and
spectral method were introduced. With the experimental study on forward simulation of anomalies given by the superposition
of six objects and measured data in Songliao plain, Northeast China, the shape, size and depth of the buried objects were
estimated in the study. Also, the results were compared with those obtained by conventional techniques, which demonstrated
that this method greatly improves the resolution of gravity anomalies.
Translated from Progress in Geophysics, 2007, 22(1): 112–120 [译自: 地球物理学进展] 相似文献
383.
多代卫星测高数据联合平差及重力场反演 总被引:1,自引:0,他引:1
为了解决多代卫星测高数据之间的不协调问题,基于误差验后补偿理论,提出了将传统的交叉点平差整体解法简化为两步处理法,即首先使用条件平差法对交叉点观测方程进行平差计算,然后沿测高轨迹进行海面高滤波和推估。使用新方法可大大简化联合平差的计算过程,且有利于提高计算结果的稳定性和可靠性,对规则和不规则的区域网和全球网交叉点平差问题都同样适用。实际算例证明了新方法的有效性。 相似文献
384.
385.
Based on the NCAR/NCEP monthly and pentad reanalysis dataset of 1961-2003, the progress of seasonal evolution of the summer atmospheric circulation in the East Asia in July to August, including the advanced and delayed cases, and their relationships with the subseasonal processes over the western North Pacific are analyzed and compared with that of climatology. The results show that the progress of seasonal cycle is advanced about a month ahead of the climatological time when the convection during 20-29 July is active in the region of the subtropical West Pacific (15°-25°N, 150°-165°E), while it is delayed about one month when weaker convections appear in the same region. Instead, the relative active convection for the latter occurs in Pentad 46 (14-18 August). It is proved that the convective activities in the early July in the equatorial central and east Pacific, and then the convective anomalies in the subtropical western North Pacific can excite the formation of the acceleration and delay of the seasonal circulation evolution in the East Asia in the late summer. The preceding subseasonal processes over the western North Pacific, including the time-lag interactions among the active convection in the late June and early July, the Northwest Pacific anticyclone, the underlying sea surface temperature and low-level winds anomalies, and their relationships with the anomalous seasonal evolution of the summer atmospheric circulation in the East Asia in late July are also investigated. However, further study, especially the numerical experiments, is needed on the mechanism of the anomaly summer seasonal cycle in the East Asia and the Northwest Pacific. 相似文献
386.
ON WESTERLY WIND BURSTS IN EQUATORIAL WESTERN PACIFIC BEFORE AND DURING THE ONSET AND INITIAL DEVELOPMENT PHASES OF ENSO 下载免费PDF全文
By means of NCEP/NCAR reanalysis dataset,the origins of westerly wind anomalies at lowlevel over equatorial western Pacific Ocean before and during the onset and initial developmentphase of ENSO are explored.Evidences show that westerly anomalies in the equatorial westernPacific(140—180°E)are characterized by two remarkable enhancements in the spring and summerof the year when El Nine emerges.The enhancements are not only.to some extem.due to theeastward propagation of low-level westerlies in equatorial Indian Ocean.but also predominantlyresulting from Ihe intense convergence of the meridional wind from both hemispheres.Thelatitudinal convergence leads to the local intensification of zonal pressure gradient so as to cause thereinforcement and bursts of westerly wind over warm pool.Besides,by virtue of the effect ofearth rotation,the northeasterlies(southeasterlies)from the Northern(Southern)Hemisphereturn into northwesterlies(southwesterlies)progressively in the near-equatorial zone.whichdirectly strengthens the westerly velocity.Comparing the contributions of the meridional windfrom both hemispheres to westerly wind bursts,is seems that southeasterlies from the SouthernHemisphere are much stronger and more stable than northwesterlies of Northern Hemisphere.It isevident that the southeasterlies to the east of Australia originate from the southern mid-and highlatitudes and are in close association with the Southern Oscillation. 相似文献
387.
对张北6.2级和5.6级两次地震前安头屯井水位异常变化及表现特征进行分析、研究,从而认为该井对捕捉地震异常信息,特别是首都圈地区的监测预报有一定的使用价值. 相似文献
388.
Anita Mohan Bhola N. Dwivedi Enrico Landi 《Journal of Astrophysics and Astronomy》2000,21(3-4):407-411
Using spectra obtained from the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft
SOHO (Solar and Heliospheric Observatory), we investigate the height dependence of electron density, temperature and abundance
anomalies in the solar atmosphere. In particular, we present the behaviour of the solar FIP effect (the abundance enhancement
of elements with first ionization potential < 10 eV in the corona with respect to photospheric values) with height
above an active region observed at the solar limb, with emphasis on the so-called transition region lines. 相似文献
389.
In this paper the authors introduce a novel approach to stochastic image processing, denoted as Differential Markov Random Field (DMRF), which has been applied to gravity anomaly separation problems. The advantages of the method are that it introduces only little distortion into the shape of the original image and that it is not affected significantly by factors such as the overlap power spectra of regional and residual fields. Testing of the proposed meth using synthetic examples gave excellent results. 相似文献
390.