全文获取类型
收费全文 | 4615篇 |
免费 | 104篇 |
国内免费 | 168篇 |
专业分类
测绘学 | 95篇 |
大气科学 | 395篇 |
地球物理 | 844篇 |
地质学 | 2325篇 |
海洋学 | 423篇 |
天文学 | 517篇 |
综合类 | 97篇 |
自然地理 | 191篇 |
出版年
2023年 | 6篇 |
2022年 | 63篇 |
2021年 | 85篇 |
2020年 | 94篇 |
2019年 | 123篇 |
2018年 | 263篇 |
2017年 | 266篇 |
2016年 | 280篇 |
2015年 | 148篇 |
2014年 | 289篇 |
2013年 | 355篇 |
2012年 | 354篇 |
2011年 | 371篇 |
2010年 | 370篇 |
2009年 | 309篇 |
2008年 | 286篇 |
2007年 | 296篇 |
2006年 | 239篇 |
2005年 | 117篇 |
2004年 | 63篇 |
2003年 | 73篇 |
2002年 | 85篇 |
2001年 | 79篇 |
2000年 | 50篇 |
1999年 | 33篇 |
1998年 | 16篇 |
1997年 | 24篇 |
1996年 | 12篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1972年 | 3篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1958年 | 3篇 |
排序方式: 共有4887条查询结果,搜索用时 31 毫秒
251.
Geomagnetic factor of Dst variations in the selective generation of ionospheric characteristic waves
HF Waves of rotating polarization have been experimentally studied on the Magadan-Petropavlovsk-Kamchatskii path. It has been obtained that the degree of suppression of one of the characteristic waves during the selective polarization generation depends on the Dst value and sign. It has been established that changes in the amplitude ratio of the signals received from the antennas of clockwise and counterclockwise polarization are maximal at a quiet geomagnetic field when Dst is positive. Under the conditions of medium disturbance of the geomagnetic field and small-scale negative Dst values, it has not been ruled out that the second characteristic wave can be observed at a receiving point in the case when one of the characteristic waves is generated. Selective polarization generation of one of the characteristic waves can be mainly masked by an increase in small-scale irregularities of ionospheric plasma. 相似文献
252.
The aim of this paper is to evaluate current knowledge and uncertainties associated with the impact of increasing greenhouse
gas and aerosol concentrations on the West African monsoon. For this purpose, coupled and time-slice simulations are used.
A global measure of the monsoon changes is defined in order to avoid regional biases and to try and obtain significant results.
The position and width of the monsoon in latitude are the main focuses. There is almost no agreement between the Coupled General
Circulation models from the Coupled models Inter-Comparison project—Phase II in regard to the impact of climate change on
the monsoon. Moreover, very simple discriminations between the models seem inappropriate to get a better signal. The role
of the different forcings in time-slice simulations is then investigated. The sea surface temperature (SST) and particularly
the pattern of the SST are shown to be the most important forcing. This accounts for the diversity of the results either from
the coupled or the forced simulations with different SST changes. With a fixed SST, but of a smaller magnitude in AMJ, there
are still uncertainties, coming first from the Atmospheric General Circulation models and the way they balance greenhouse
gas and global SST increase. Finally the uncertainty due to the Land Surface models (LSMs) is not negligible. The greenhouse
gas and the LSMs are shown to have more impact in August, when the monsoon is at its highest latitude on the continent. 相似文献
253.
N. R. Bigil’deeva A. P. Makhinya I. A. Usatova D. A. Makhinya V. N. Petkevich 《Russian Meteorology and Hydrology》2007,32(11):694-697
Some results of use of snow survey monitoring data within the system of the Privolzhie Administration for Hydrometeorological Service for studying the degree of snow cover pollution and mapping pollution distribution in several urban and rural areas of the Samara region are considered. 相似文献
254.
Recent Progress in the Impact of the Tibetan Plateau on Climate in China 总被引:14,自引:0,他引:14
Studies of the impacts of the Tibetan Plateau (TP) on climate in China in the last four years are reviewed. It is reported that temperature and precipitation over the TP have increased during recent decades. From satellite data analysis, it is demonstrated that most of the precipitation over the TP is from deep convection clouds. Moreover, the huge TP mechanical forcing and extraordinary elevated thermal forcing impose remarkable impacts upon local circulation and global climate. In winter and spring, stream flow is deflected by a large obstacle and appears as an asymmetric dipole, making East Asia much colder than mid Asia in winter and forming persistent rainfall in late winter and early spring over South China. In late spring, TP heating contributes to the establishment and intensification of the South Asian high and the abrupt seasonal transition of the surrounding circulations. In summer, TP heating in conjunction with the TP air pump cause the deviating stream field to resemble a cyclonic spiral, converging towards and rising over the TP. Therefore, the prominent Asian monsoon climate over East Asia and the dry climate over mid Asia in summer are forced by both TP local forcing and Eurasian continental forcing.
Due to the longer memory of snow and soil moisture, the TP thermal status both in summer and in late winter and spring can influence the variation of Eastern Asian summer rainfall. A combined index using both snow cover over the TP and the ENSO index in winter shows a better seasonal forecast.
On the other hand, strong sensible heating over the Tibetan Plateau in spring contributes significantly to anchor the earliest Asian monsoon being over the eastern Bay of Bengal (BOB) and the western Indochina peninsula. Qualitative prediction of the BOB monsoon onset was attempted by using the sign of meridional temperature gradient in March in the upper troposphere, or at 400 hPa over the TP. It is also demonstrated by a numerical experiment and theoretical study that the heating over the TP lea 相似文献
Due to the longer memory of snow and soil moisture, the TP thermal status both in summer and in late winter and spring can influence the variation of Eastern Asian summer rainfall. A combined index using both snow cover over the TP and the ENSO index in winter shows a better seasonal forecast.
On the other hand, strong sensible heating over the Tibetan Plateau in spring contributes significantly to anchor the earliest Asian monsoon being over the eastern Bay of Bengal (BOB) and the western Indochina peninsula. Qualitative prediction of the BOB monsoon onset was attempted by using the sign of meridional temperature gradient in March in the upper troposphere, or at 400 hPa over the TP. It is also demonstrated by a numerical experiment and theoretical study that the heating over the TP lea 相似文献
255.
256.
257.
258.
259.
260.