全文获取类型
收费全文 | 71162篇 |
免费 | 879篇 |
国内免费 | 600篇 |
专业分类
测绘学 | 1943篇 |
大气科学 | 5125篇 |
地球物理 | 12723篇 |
地质学 | 27835篇 |
海洋学 | 6035篇 |
天文学 | 15592篇 |
综合类 | 308篇 |
自然地理 | 3080篇 |
出版年
2022年 | 365篇 |
2021年 | 616篇 |
2020年 | 658篇 |
2019年 | 704篇 |
2018年 | 3943篇 |
2017年 | 3650篇 |
2016年 | 3108篇 |
2015年 | 1076篇 |
2014年 | 1774篇 |
2013年 | 2868篇 |
2012年 | 2720篇 |
2011年 | 4609篇 |
2010年 | 4081篇 |
2009年 | 4775篇 |
2008年 | 3939篇 |
2007年 | 4577篇 |
2006年 | 2227篇 |
2005年 | 2012篇 |
2004年 | 1941篇 |
2003年 | 1886篇 |
2002年 | 1694篇 |
2001年 | 1316篇 |
2000年 | 1195篇 |
1999年 | 924篇 |
1998年 | 977篇 |
1997年 | 885篇 |
1996年 | 739篇 |
1995年 | 774篇 |
1994年 | 673篇 |
1993年 | 597篇 |
1992年 | 578篇 |
1991年 | 585篇 |
1990年 | 613篇 |
1989年 | 477篇 |
1988年 | 494篇 |
1987年 | 519篇 |
1986年 | 476篇 |
1985年 | 602篇 |
1984年 | 666篇 |
1983年 | 584篇 |
1982年 | 552篇 |
1981年 | 508篇 |
1980年 | 484篇 |
1979年 | 469篇 |
1978年 | 456篇 |
1977年 | 366篇 |
1976年 | 344篇 |
1975年 | 356篇 |
1974年 | 301篇 |
1973年 | 342篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Geomagnetism and Aeronomy - It is possible that the radially independent, spatial-spectral components of the energy and power of the potential part of the main geomagnetic field were determined and... 相似文献
42.
Piret Cécile Dissanayake Nadun Gierke John S. Fornberg Bengt 《Mathematical Geosciences》2020,52(4):477-497
Mathematical Geosciences - A robust, high order modeling approach is introduced, based on the finite difference-based radial basis functions method, for solving the groundwater flow equation in the... 相似文献
43.
Volkov A. V. Galyamov A. L. Savchuk Yu. S. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(12):1528-1536
Izvestiya, Atmospheric and Oceanic Physics - Gravimetric data obtained by the GOCE spacecraft contributes to the development of global models of the deep structure of the Earth’s crust and... 相似文献
44.
Vajapeyam S. Srinivasan Hugo M. de Alcântara Carlos de O. Galvão Ulisses A. Bezerra John E. de Brito Leite Cunha 《水文研究》2021,35(5):e14194
Catchments have highly variable yields of runoff and soil erosion. The size, land use and the surface cover play a significant role and influence the catchment response and parameter values of simulation models. Two experimental basins—the Cariri basins—were equipped in a semi-arid region of Brazil, for obtaining runoff and sediment yield at different catchment scales, as well as, to evaluate the influence of the land use and surface cover. In the first basin, located in the municipality of Sumé, the field studies were carried out at two different scales: four micro-catchments with an area of around 0.5 ha and nine standard Wischmeier-type erosion plots of 100 m2. The experimental units had varied vegetation and management. They were subjected only to natural rainfall events, and were monitored from 1982 to 1991. The total runoff and total sediment yield were determined for each of the events. The installations in the second basin, in the municipality of São João do Cariri, from 1999, include two erosion plots, three micro-catchments, and two sub-catchments of a small basin. These basins are still being monitored for runoff and sediment production. Among the micro-catchments two are nested to detect any scale effect at the micro-catchment level. Nearly 600 events of precipitation, that produced runoff in at least one of the experimental units, have been registered. These data have been used to evaluate the influence of various factors, including cultivation practices and to calibrate hydrological models for plots and micro-catchments. Parameters have been tested by means of cross validations among micro-catchments and sub-catchments. The data sets are made available to all the catchment hydrology researchers and others at https://doi.org/10.5281/zenodo.4690886 . 相似文献
45.
The existence and linear stability of the planar equilibrium points for photogravitational elliptical restricted three body problem is investigated in this paper. Assuming that the primaries, one of which is radiating are rotating in an elliptical orbit around their common center of mass. The effect of the radiation pressure, forces due to stellar wind and Poynting–Robertson drag on the dust particles are considered. The location of the five equilibrium points are found using analytical methods. It is observed that the collinear equilibrium points L1, L2 and L3 do not lie on the line joining the primaries but are shifted along the y-coordinate. The instability of the libration points due to the presence of the drag forces is demonstrated by Lyapunov’s first method of stability. 相似文献
46.
47.
48.
A. A. Melkumyan A. V. Belov M. A. Abunina A. A. Abunin E. A. Eroshenko V. A. Oleneva V. G. Yanke 《Geomagnetism and Aeronomy》2018,58(2):154-168
The IZMIRAN database of Forbush effects and interplanetary disturbances was used to study features of the action of high-speed solar wind streams from coronal holes on cosmic rays. Three hundred and fifty Forbush effects created by coronal holes without other actions were distinguished. The mean values and distributions have been found for different characteristics of events from this group and compared with all Forbush effects and Forbush effects caused by coronal ejections. Despite the great differences in high-speed streams from coronal holes, this group turned out to be more compact and uniform as compared to events related to coronal ejections. Regression dependences and correlation relations between different parameters of events for the studied groups have been obtained. It has been shown that Forbush effects caused by coronal ejections depend considerably more strongly on the characteristics of interplanetary disturbances as compared to Forbush effects related to coronal holes. This suggests a significant difference between the modulation mechanisms of Forbush effects of different types and corroborates earlier conclusions based on indirect data. 相似文献
49.
A.?B.?AndreevEmail author V.?M.?Somsikov S.?N.?Mukasheva V.?I.?Kapytin K.?A.?Nurgalieva 《Geomagnetism and Aeronomy》2018,58(1):106-112
The effects of atmospheric nonequilibrium in the generation of wave perturbations due to the solar radiation flux are studied. Equations of nonequilibrium thermodynamics are used to perform an assessment of the channels of solar energy transformation into the atmosphere for different altitudes. As a result of calculations of the dispersion relation for a nonequilibrium atmosphere, we consider how the flux of solar radiation changes the spectrum of natural atmospheric oscillations at different altitudes and for different solar activities. A qualitative relation between the results of wave spectra calculations and the data of ionosphere dynamics observations for different intensities of the solar radiation flux has been established. 相似文献
50.
M.?B.?KrainevEmail author G.?A.?Bazilevskaya M.?S.?Kalinin A.?K.?Svirzhevskaya N.?S.?Svirzhevskii 《Geomagnetism and Aeronomy》2018,58(2):169-177
During the prolonged and deep minimum of solar activity between cycles 23 and 24, an unusual behavior of the heliospheric characteristics and increased intensity of galactic cosmic rays (GCRs) near the Earth’s orbit were observed. The maximum of the current solar cycle 24 is lower than the previous one, and the decline in solar and, therefore, heliospheric activity is expected to continue in the next cycle. In these conditions, it is important for an understanding of the process of GCR modulation in the heliosphere, as well as for applied purposes (evaluation of the radiation safety of planned space flights, etc.), to estimate quantitatively the possible GCR characteristics near the Earth in the upcoming solar minimum (~2019–2020). Our estimation is based on the prediction of the heliospheric characteristics that are important for cosmic ray modulation, as well as on numeric calculations of GCR intensity. Additionally, we consider the distribution of the intensity and other GCR characteristics in the heliosphere and discuss the intercycle variations in the GCR characteristics that are integral for the whole heliosphere (total energy, mean energy, and charge). 相似文献