全文获取类型
收费全文 | 51192篇 |
免费 | 421篇 |
国内免费 | 317篇 |
专业分类
测绘学 | 995篇 |
大气科学 | 2572篇 |
地球物理 | 9814篇 |
地质学 | 19547篇 |
海洋学 | 4855篇 |
天文学 | 12251篇 |
综合类 | 131篇 |
自然地理 | 1765篇 |
出版年
2022年 | 577篇 |
2021年 | 858篇 |
2020年 | 896篇 |
2019年 | 1005篇 |
2018年 | 2103篇 |
2017年 | 1914篇 |
2016年 | 2044篇 |
2015年 | 836篇 |
2014年 | 1827篇 |
2013年 | 2793篇 |
2012年 | 2078篇 |
2011年 | 2469篇 |
2010年 | 2318篇 |
2009年 | 2686篇 |
2008年 | 2358篇 |
2007年 | 2622篇 |
2006年 | 2301篇 |
2005年 | 1299篇 |
2004年 | 1214篇 |
2003年 | 1195篇 |
2002年 | 1159篇 |
2001年 | 1130篇 |
2000年 | 936篇 |
1999年 | 694篇 |
1998年 | 706篇 |
1997年 | 735篇 |
1996年 | 549篇 |
1995年 | 573篇 |
1994年 | 535篇 |
1993年 | 434篇 |
1992年 | 449篇 |
1991年 | 428篇 |
1990年 | 479篇 |
1989年 | 421篇 |
1988年 | 388篇 |
1987年 | 409篇 |
1986年 | 336篇 |
1985年 | 463篇 |
1984年 | 468篇 |
1983年 | 453篇 |
1982年 | 432篇 |
1981年 | 387篇 |
1980年 | 395篇 |
1979年 | 347篇 |
1978年 | 378篇 |
1977年 | 320篇 |
1976年 | 287篇 |
1975年 | 293篇 |
1974年 | 274篇 |
1973年 | 344篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
The population and distribution of carbon-oxidizing and sulfate-reducing bacteria in the soils of the Mozhaisk Reservoir are studied. 相似文献
82.
The distribution of sites where globular clusters have crossed the Galactic disk during the last 100 million years has been analyzed using the most recent kinematic data for 133 globular clusters (GCs). ThreeGCs (NGC 6341, NGC 7078, and ω Cen) whose distances between the positions where they crossed the Galactic disk and trajectories of the Gould Belt are less than 20% of their heliocentric distances at the crossing time (82, 98, and 96 million years ago, respectively) have been identified. For each of the clusters, this was their next to last, rather than their last, crossing of the Galactic disk. The passage of any one of these three GCs through the disk could potentially have initiated the formation of the Gould Belt. 相似文献
83.
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
84.
Sources of dissolved REE in mountainous streams draining granitic rocks, Sierras Pampeanas (Córdoba, Argentina) 总被引:1,自引:0,他引:1
M. Gabriela García Karina L. Lecomte Andrea I. Pasquini Stella M. Formica Pedro J. Depetris 《Geochimica et cosmochimica acta》2007,71(22):5355-5368
Stream waters draining granitic terrains from the highest part (850 to 2200 m a.s.l.) of Sierras Pampeanas (Córdoba, Argentina, ∼32°S, ∼65°W) were sampled in order to define sources and distribution of dissolved rare earth elements (REE), and to describe the geochemical processes that govern their mobility. The contribution of the regional granite to the dissolved REE pool in stream water is limited due to the physical conditions predominating in the area (i.e., steep slopes and semiarid climate). Therefore, precipitation is considered a seasonally significant source controlling REE concentration in stream water. Dissolved REE concentrations are inversely correlated with monthly precipitation and rainfall frequency. During the rainy season (i.e., the austral summer) REE concentrations in stream water are lower than during the dry season (i.e., austral winter). Such low concentrations reflect the balance between the REE input from precipitation and their removal by adsorption. In contrast, during the dry season, the longer residence time of water within fractures and colluvium determines an increased REE concentration in the base flow. Lower pH values also contribute to raise REE concentration through desorption from mineral surfaces. 相似文献
85.
86.
87.
Studia Geophysica et Geodaetica - 相似文献
88.
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
89.
90.