全文获取类型
收费全文 | 45342篇 |
免费 | 221篇 |
国内免费 | 981篇 |
专业分类
测绘学 | 1822篇 |
大气科学 | 3360篇 |
地球物理 | 8087篇 |
地质学 | 20961篇 |
海洋学 | 2626篇 |
天文学 | 5783篇 |
综合类 | 2182篇 |
自然地理 | 1723篇 |
出版年
2023年 | 20篇 |
2022年 | 30篇 |
2021年 | 36篇 |
2020年 | 31篇 |
2019年 | 48篇 |
2018年 | 6888篇 |
2017年 | 6191篇 |
2016年 | 3839篇 |
2015年 | 368篇 |
2014年 | 279篇 |
2013年 | 256篇 |
2012年 | 1947篇 |
2011年 | 4815篇 |
2010年 | 4230篇 |
2009年 | 4435篇 |
2008年 | 3559篇 |
2007年 | 4576篇 |
2006年 | 308篇 |
2005年 | 813篇 |
2004年 | 843篇 |
2003年 | 885篇 |
2002年 | 531篇 |
2001年 | 144篇 |
2000年 | 158篇 |
1999年 | 92篇 |
1998年 | 99篇 |
1997年 | 87篇 |
1996年 | 75篇 |
1995年 | 47篇 |
1994年 | 33篇 |
1993年 | 57篇 |
1992年 | 35篇 |
1991年 | 42篇 |
1990年 | 27篇 |
1989年 | 34篇 |
1988年 | 38篇 |
1987年 | 42篇 |
1986年 | 52篇 |
1985年 | 41篇 |
1984年 | 45篇 |
1983年 | 43篇 |
1982年 | 46篇 |
1981年 | 55篇 |
1980年 | 56篇 |
1979年 | 35篇 |
1977年 | 20篇 |
1976年 | 27篇 |
1975年 | 23篇 |
1974年 | 20篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
66.
The history of the discovery of hot gas in galaxies is briefly reviewed, and the main properties of this gas described, emphasizing the need to refine these properties, in particular, the mass of the gas. It is proposed to do this via observations of the Sunyaev-Zel’dovich (SZ) effect due to hot gas in the coronas of elliptical galaxies. The absolute and relative perturbations of the spectrum of the cosmic microwave background (CMB) radiation due to scattering of the CMB photons by electrons with a Maxwellian energy distribution are calculated. The possibility of observing the SZ effect is demonstrated using three elliptical galaxies as examples. The kinematic SZ effect arising due to the peculiar motions and rotations of the galaxies is also accessible to observations. Together with X-ray data, such observations would enable refinement of the properties of gas in galaxies, and also yield additional information about the rotation of galaxies, possible accretion flows in the galactic gas, and hot galactic winds. 相似文献
67.
Mirdita Zone ophiolites and associated sediments in Albania reveal Neotethys Ocean origin 总被引:1,自引:1,他引:0
Hans-Jürgen Gawlick Wolfgang Frisch Lirim Hoxha Paulian Dumitrica Leopold Krystyn Richard Lein Sigrid Missoni Felix Schlagintweit 《International Journal of Earth Sciences》2008,97(4):865-881
The Mirdita Ophiolite Zone in Albania is associated with widespread mélanges containing components of up to nappe-size. We
dated matrix and components of the mélange by radiolarians, conodonts, and other taxa. The components consist of radiolarites,
pelagic limestones and shallow-water limestones, all of Triassic age, as well as ophiolites. Triassic radiolarite as a primary
cover of ophiolite material proves Middle Triassic onset of Mirdita ocean-floor formation. The mélange contains a turbiditic
radiolarite-rich matrix (“radiolaritic flysch”), dated as Late Bajocian to Early Oxfordian. It formed as a synorogenic sediment
during west-directed thrusting of ophiolite and sediment-cover nappes representing ocean floor and underplated fragments of
the western continental margin. The tectonic structures formed during these orogenic events (“Younger Kimmeridian or Eohellenic
Orogeny”) are sealed by Late Jurassic platform carbonates. The geological history conforms with that of the Inner Dinarides
and adjoining areas; we therefore correlate the Mirdita-Pindos Ophiolite Zone with the Vardar Zone and explain its present
position by far-distance west-directed thrusting. 相似文献
68.
We developed light requirements for eelgrass in the Pacific Northwest, USA, to evaluate the effects of short- and long-term
reductions in irradiance reaching eelgrass, especially related to turbidity and overwater structures. Photosynthesis-irradiance
experiments and depth distribution field studies indicated that eelgrass productivity was maximum at a photosynthetic photon
flux density (PPFD) of about 350–550 μmol quanta m−2 s−1. Winter plants had approximately threefold greater net apparent primary productivity rate at the same irradiance as summer
plants. Growth studies using artificial shading as well as field monitoring of light and eelgrass growth indicated that long-term
survival required at least 3 mol quanta m−2 day−1 on average during spring and summer (i.e., May-September), and that growth was saturated above about 7 mol quanta m−2 day−1. We conclude that non-light-limited growth of eelgrass in the Pacific Northwest requires an average of at least 7 mol quanta
m−2 day−1 during spring and summer and that long-term survival requires a minimum average of 3 mol quanta m−2 day−1. 相似文献
69.
O. G. Den 《Astronomy Reports》2008,52(11):931-936
We analyze the flare events of October 28 and May 27, 2003 to examine the possible connection of solar flares with singularities in the differential characteristics of solar magnetic fields. The relation between flares and the behavior of F indicators (which describe structural singularities of the magnetic fields) introduced earlier is analyzed. It is shown that the generation of flares can be associated with self-intersections (or reconnection) of the F = 0 curves, where magnetic reconnection can occur. Consequently, the current sheets generated in such regions can be sources of energy release. 相似文献
70.
It is shown that the centroid of the heliospheric equator undergoes quasi-periodic oscillations. During the minimum of the 11-year cycle, the centroid shifts southwards (the so-called bashful-ballerina effect). The direction of the shift reverses during the solar maximum. The solar quadrupole is responsible for this effect. The shift is compared with the tilt of the heliospheric current sheet. 相似文献