全文获取类型
收费全文 | 95417篇 |
免费 | 919篇 |
国内免费 | 1402篇 |
专业分类
测绘学 | 2991篇 |
大气科学 | 6066篇 |
地球物理 | 18695篇 |
地质学 | 37060篇 |
海洋学 | 7417篇 |
天文学 | 18946篇 |
综合类 | 2316篇 |
自然地理 | 4247篇 |
出版年
2022年 | 603篇 |
2021年 | 926篇 |
2020年 | 1017篇 |
2019年 | 1079篇 |
2018年 | 6812篇 |
2017年 | 5939篇 |
2016年 | 4836篇 |
2015年 | 1343篇 |
2014年 | 2292篇 |
2013年 | 3764篇 |
2012年 | 3414篇 |
2011年 | 5688篇 |
2010年 | 4792篇 |
2009年 | 5776篇 |
2008年 | 4924篇 |
2007年 | 5497篇 |
2006年 | 3039篇 |
2005年 | 2145篇 |
2004年 | 2272篇 |
2003年 | 2184篇 |
2002年 | 1953篇 |
2001年 | 1656篇 |
2000年 | 1497篇 |
1999年 | 1160篇 |
1998年 | 1219篇 |
1997年 | 1190篇 |
1996年 | 970篇 |
1995年 | 986篇 |
1994年 | 889篇 |
1993年 | 770篇 |
1992年 | 734篇 |
1991年 | 742篇 |
1990年 | 838篇 |
1989年 | 723篇 |
1988年 | 661篇 |
1987年 | 794篇 |
1986年 | 636篇 |
1985年 | 862篇 |
1984年 | 941篇 |
1983年 | 883篇 |
1982年 | 805篇 |
1981年 | 827篇 |
1980年 | 724篇 |
1979年 | 643篇 |
1978年 | 679篇 |
1977年 | 600篇 |
1976年 | 568篇 |
1975年 | 571篇 |
1974年 | 540篇 |
1973年 | 606篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
The first small active regions of the last two new cycles seem to be formed, in its very first, preparatory stage, close to the equator with uncertain magnetic orientation, and as secondary products at the periphery of equatorial `magnetic bubbles' of the new magnetic flux still belonging to the old cycle. At the real beginning of the new cycle, at the periphery of its higher-latitude `magnetic bubbles', the opposite applies to the secondary regions of the ending cycle. It seems that two modes of magnetic flux supply the visible layers of the photosphere during the cycle transition phase: the emergence of the magnetic flux from the depth of the convective zone, and the mutual interaction of the earlier emerging fluxes, or the action of the `local dynamo', giving rise to the new local magnetic field concentrations. 相似文献
122.
The population and distribution of carbon-oxidizing and sulfate-reducing bacteria in the soils of the Mozhaisk Reservoir are studied. 相似文献
123.
The eleventh list of faint late M and carbon type stars detected on the plates of the First Byurakan Spectral Survey in zone -7° -3° and covering about 1000 square degrees is presented. From 126 detected stars, 88 are newly discovered objects: they are 6 carbon stars, 8 carbon star candidates, and 74 M-type stars; among the latter 38 (26 PSC + 12 FSC) are unclassified IRAS sources, and one object is an unclassified ROSAT source. Distances to the 6 newly discovered early-type carbon stars are estimated. Equatorial coordinates, red magnitudes, and spectral classes determined from the Palomar E-charts are provided. The lack of optical counterparts on Palomar O and E maps for two detected late M-type stars indicates a large variability in brightnesses of these objects (amplitude not smaller than 7.0 magnitude). 相似文献
124.
125.
Studia Geophysica et Geodaetica - 相似文献
126.
N. V. Makarova V. M. Makeev T. V. Sukhanova P. S. Miklyaev A. L. Dorozhko I. V. Korobova 《Moscow University Geology Bulletin》2012,67(4):209-217
The neotectonic structures of the Lower Oka (Nizhneokskii) Region formed under different geodynamic conditions. This is attested by the morphology, orientation, internal structure, and jointing of the structures. The Oka-Tsna arc formed under the effect of tension from an inner source on the one hand and stress from the Alpian belt on the other hand. The latitudinally-oriented structures of the northwestern slope of the Tokmovo arc emerged as a result of uplift and widening. Both types of structure are combined within the limits of the Oka-Murom trough, which is a geodynamically active zone. 相似文献
127.
128.
129.
G. Ajeagah Aghaindum S. Foto Menbohan 《International Journal of Environmental Science and Technology》2012,9(4):655-660
The optimum period for ciliated protozoa colonizing of an artificial substrate, the polyurethane foams have been assessed in a tropical aquatic ecosystem, the Ekozoa stream of the Mfoundi River Basin in Yaounde (Cameroon). 5?days were calculated as the highest period for the biological indicators of pollution to optimally colonize the artificial substrate. This time interval is the same for all the sampling stations assessed from upstream to downstream and the various microhabitats along the water course. The statistical method applied is that of the completely randomized blocks. The colonization of the substrate increases from the first day to the fifth day, before decreasing to the tenth day. The statistical analysis of variance between the maximum day and the other sampling period was significant at 5?% while the calculation of the value between different points of the same station was not significant. The average number of ciliated protozoan ranges from 20 to 23, from upstream to downstream. 相似文献
130.
A model is proposed that shows the relation of the block structure of the crust and earthquake sources (Sadovskii, 1979; Rodionov, 1979, 1984, 1994; Bugaev, 1999, 2011, 2014, 2015). The model can formalize how to assess the prediction of seismic regime parameters depending on the elastic limit and conditions and rate of deformation of the Earth’s crust. The spent nuclear fuel repository site in Olkiluoto (Finland) and a site in the area of the Krasnoyarsk Mining and Chemical Combine are considered as examples. It is demonstrated that the parameters of the prediction graphs limit the location of the points of magnitude repeatability graphs calculated for a site based on samples of earthquakes in the area according to different authors. This makes it possible to recommend predictive assessment of seismic regime parameters for stability monitoring of the seismic regime and safety analysis of a geological environment’s insulation properties for waste sites from the results of seismological monitoring and high-precision observations of modern movements of the Earth’s crust. 相似文献