全文获取类型
收费全文 | 2479篇 |
免费 | 115篇 |
国内免费 | 28篇 |
专业分类
测绘学 | 56篇 |
大气科学 | 231篇 |
地球物理 | 711篇 |
地质学 | 817篇 |
海洋学 | 279篇 |
天文学 | 337篇 |
综合类 | 40篇 |
自然地理 | 151篇 |
出版年
2021年 | 40篇 |
2020年 | 36篇 |
2019年 | 34篇 |
2018年 | 84篇 |
2017年 | 81篇 |
2016年 | 142篇 |
2015年 | 86篇 |
2014年 | 132篇 |
2013年 | 174篇 |
2012年 | 132篇 |
2011年 | 332篇 |
2010年 | 114篇 |
2009年 | 144篇 |
2008年 | 114篇 |
2007年 | 118篇 |
2006年 | 66篇 |
2005年 | 79篇 |
2004年 | 88篇 |
2003年 | 63篇 |
2002年 | 31篇 |
2001年 | 38篇 |
2000年 | 38篇 |
1999年 | 34篇 |
1998年 | 28篇 |
1997年 | 32篇 |
1996年 | 22篇 |
1995年 | 16篇 |
1994年 | 25篇 |
1993年 | 17篇 |
1992年 | 13篇 |
1991年 | 8篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 8篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1976年 | 5篇 |
1975年 | 11篇 |
1974年 | 14篇 |
1973年 | 8篇 |
1972年 | 10篇 |
1971年 | 7篇 |
1970年 | 7篇 |
排序方式: 共有2622条查询结果,搜索用时 31 毫秒
151.
Summary The convection in a rapidly rotating electrically conducting, fluid horizontal layer of non-constant stratification, permeated by an inhomogeneous magnetic field, is studied. In this connection, a temperature model of the layer is constructed, which creates a structure such that part of the layer is unstably and a part stably stratified. The results obtained are applied to the conditions in the fluid Earth's core.
¶rt;m u m aa mn¶rt; u¶rt;uma , m um nm mamuuau u a¶rt;um ¶rt;¶rt; aum n. uaa nu m mna ¶rt; nu¶rt;um uu ma mm, nu m am mamuuum mau, a am — mau. mam unm ¶rt; aaua n, nu¶rt;u u¶rt; ¶rt; u.相似文献
152.
J. Ricardo A. De França J. -M. Brustet J. Fontan 《Journal of Atmospheric Chemistry》1995,22(1-2):81-110
Remote sensing measurements provide a vauable means of determining the extent of burning areas and of estimating the overall distribution of pollutant sources (identified from experimental studies) in time and space. This distribution has to be taken into account in the boundary conditions of chemistry atmospheric models.Recent methods developed for the remote sensing of active fires in tropical or temperated forest zones, have been found to be completely inadequate for fire detection on West African savannas. In order to accurately estimate the active fire distribution in the function of different sorts of West African savannas (Sahelian, Sudanian and Guinean) and forests, a multispectral methodology has been developed based on NOAA/11-AVHRR satellite data, with the purpose of eliminating as much as possible the problems related to large surface heterogeneity, confusion and bias, produced by clouds, smoke, haze, background emissivities, etc.Unlike other methods, the results show that the multispectral method, in spite of its selectivity, provides realistic results, and does not under- or over-estimate the number of fires that can be sensed by the satellite. Consequently, this methodology is more appropriate than the simplest ones for a systematic sensing of this phenomenon. 相似文献
153.
Milan Burša 《Studia Geophysica et Geodaetica》1995,39(1):1-10
Summary The positions of the Lagrangian points of the Pluto-Charon system have been determined using the orthogonal system of cofocal ellipses-hyperbolas, the foci being situated at the centre of mass of the bodies. The tidal distortions of Pluto amount to 30 m, those of charon to 122 m. The tidal forces are believed to influence the figures of the bodies significantly. 相似文献
154.
Summary Formulae and numerical estimates are given for the non-periodical variations in the curvature of equipotential surfaces, horizontal forces and directions of the vertical, caused by the decrease in the second zonal geopotential harmonic, by the decrease in the angular velocity of the Earth's rotation and by secular polar motion.
am ¶rt; u ua a nu¶rt;uu uu uu nm, maua u u u ma, a u m aauunmuaa, u mu au u u ¶rt;uu n.相似文献
155.
一次梅雨锋低空急流形成的分析 总被引:5,自引:1,他引:5
对1979年6月24—25日的一次梅雨锋低空急流的形成进行了分析,它的形成是由于在300mb高空急流中心附近产生的地转不平衡,使急流入口区的右侧造成高空辐散的作用。当高空急流中心东移,急流入口区右侧的高空辐散区移到江淮流域上空,由此高空辐散引起对流层下部的质量调整,致使低空造成降压区与辐合。这降压区造成的变压风迭加到低空的西南气流上,沿通过该负变压区(或负变高区)中心的西南气流作为一条轴线,轴线的右侧变压风使西南风偏向低压一侧,从而使西南风的动能增加;轴线的左侧变压风使西南风偏向高压一侧,从而使西南风的动 相似文献
156.
157.
158.
Stable recurrent sunspot groups from the Greenwich data set which were identified in at least two subsequent solar rotations were traced and meridional motions were determined from the two central meridian passages. In total, 327 meridional velocities were calculated and the results for the northern and the southern solar hemisphere were compared. A dependence of the solar meridional velocity vectors on the development status, latitude and position respectively to the activity belt of sunspots is investigated. The results indicate that sunspot groups are moving on the average away from the center of activity. This was found for sunspot groups growing and decreasing in area. 相似文献
159.
Polycyclic aromatic hydrocarbons and their molecular diagnostic ratios in urban atmospheric respirable particulate matter 总被引:2,自引:5,他引:2
María del Rosario Sienra Nelson G. Rosazza Margarita Prndez 《Atmospheric Research》2005,75(4):267-281
Atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs) in Santiago de Chile city were evaluated to study particulate PAHs profiles during cold and spring weather periods. Urban atmospheric particulate matter PM10 was collected using High Volume PM10 samplers. Fifteen samples of 24 h during austral winter and 20 samples of 24 h during spring, 2000 were collected at two sampling sites (North–East and Central areas of the city) whose characteristics were representative of the prevailing conditions. Seventeen PAHs were quantified and total PAHs concentration ranged from 1.39 to 59.98 ng m−3, with a seasonal variation (winter vs. spring ratio) from 0.5 to 12.6 ng m−3. Molecular diagnostic ratios were used to characterize and identify PAHs emission sources such as combustion and biogenic emissions. Results showed that the major sources of respirable organic aerosol PM10 in Santiago are mobile and stationary ones. 相似文献
160.