全文获取类型
收费全文 | 115009篇 |
免费 | 1629篇 |
国内免费 | 765篇 |
专业分类
测绘学 | 2679篇 |
大气科学 | 7862篇 |
地球物理 | 21802篇 |
地质学 | 43104篇 |
海洋学 | 9817篇 |
天文学 | 25453篇 |
综合类 | 379篇 |
自然地理 | 6307篇 |
出版年
2022年 | 679篇 |
2021年 | 1133篇 |
2020年 | 1233篇 |
2019年 | 1379篇 |
2018年 | 4475篇 |
2017年 | 4048篇 |
2016年 | 3906篇 |
2015年 | 1699篇 |
2014年 | 2970篇 |
2013年 | 5285篇 |
2012年 | 3877篇 |
2011年 | 5875篇 |
2010年 | 5234篇 |
2009年 | 6451篇 |
2008年 | 5488篇 |
2007年 | 5939篇 |
2006年 | 4156篇 |
2005年 | 3273篇 |
2004年 | 3177篇 |
2003年 | 3078篇 |
2002年 | 2908篇 |
2001年 | 2428篇 |
2000年 | 2387篇 |
1999年 | 1928篇 |
1998年 | 1973篇 |
1997年 | 1815篇 |
1996年 | 1545篇 |
1995年 | 1534篇 |
1994年 | 1313篇 |
1993年 | 1250篇 |
1992年 | 1162篇 |
1991年 | 1180篇 |
1990年 | 1159篇 |
1989年 | 1026篇 |
1988年 | 932篇 |
1987年 | 1116篇 |
1986年 | 962篇 |
1985年 | 1199篇 |
1984年 | 1366篇 |
1983年 | 1326篇 |
1982年 | 1214篇 |
1981年 | 1147篇 |
1980年 | 1046篇 |
1979年 | 968篇 |
1978年 | 965篇 |
1977年 | 829篇 |
1976年 | 831篇 |
1975年 | 828篇 |
1974年 | 774篇 |
1973年 | 836篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Yulia A. Chernetenko 《Celestial Mechanics and Dynamical Astronomy》2001,80(3-4):185-194
International programs of observations of selected minor planets have lasted about 50 years and the last one comes to the end in 2000. The main aim of these observational programs consists in obtaining the orientation of the stellar reference frame with respect to the dynamical one using observations of the bright minor planets. The observations are also useful for the orbital improvements of the asteroids themselves. They are available from the author via e-mail at the address .During the above mentioned period more than 23 000 observations of minor planets, referred to different reference star catalogues, have been obtained. The reduction procedure of observations to the PPM star catalogue is described. The orientation parameters are given and discussed. 相似文献
132.
We report on SWS and LWS observations of the circumstellar disks of young stars of a few solar masses. The ISO spectra of
these objects present a diversity of emission features of carbon-rich and oxygen-rich grains. The similarity of the forsterite
spectra observed for Comet Hale-Bopp and the Haebe star HD100546 is particularly striking and provides a new argument that
huge comet swarms are formed in the disks surrounding young stars. While the data suggest that the formation of crystalline
silicates in the dust disks essentially occurs when a Haebe star has already reached the main sequence, no clear correlation
with stellar age only is apparent.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
133.
Generally speaking, variable stars are monitored through observing campaigns which coordinate multi-site telescopes at various
longitudes. A new practice is in progress: devoted networks involving robotic telescopes. We will review these two technologies
and will emphasize the NORT (Network of Oriental Robotic Telescopes) project which we are promoting in North Africa, Middle-Eastern
countries and Asia.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
134.
A. Kučinskas 《Astrophysics and Space Science》1997,251(1-2):231-234
We have calculated terminal gas outflow velocities from the circumstellar shells of the AGB stars. Our results confirm that,
in case of the stationary dust driven winds, the dynamics of the outflow is governed essentially by the dust properties and
stellar luminosities, while only marginally by other stellar parameters. Although being far from comprehensive, our calculations
also indicate that the dust driven winds may only occur in cool, luminous, low mass objects.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
135.
Published in Astrofizika, Vol. 38, No. 4, pp. 677–680, October–December, 1995. 相似文献
136.
J. M. Gregory J. A. Church G. J. Boer K. W. Dixon G. M. Flato D. R. Jackett J. A. Lowe S. P. O'Farrell E. Roeckner G. L. Russell R. J. Stouffer M. Winton 《Climate Dynamics》2001,18(3-4):225-240
Sea-level rise is an important aspect of climate change because of its impact on society and ecosystems. Here we present
an intercomparison of results from ten coupled atmosphere-ocean general circulation models (AOGCMs) for sea-level changes
simulated for the twentieth century and projected to occur during the twenty first century in experiments following scenario
IS92a for greenhouse gases and sulphate aerosols. The model results suggest that the rate of sea-level rise due to thermal
expansion of sea water has increased during the twentieth century, but the small set of tide gauges with long records might
not be adequate to detect this acceleration. The rate of sea-level rise due to thermal expansion continues to increase throughout
the twenty first century, and the projected total is consequently larger than in the twentieth century; for 1990–2090 it amounts
to 0.20–0.37 m. This wide range results from systematic uncertainty in modelling of climate change and of heat uptake by the
ocean. The AOGCMs agree that sea-level rise is expected to be geographically non-uniform, with some regions experiencing as
much as twice the global average, and others practically zero, but they do not agree about the geographical pattern. The lack
of agreement indicates that we cannot currently have confidence in projections of local sea-level changes, and reveals a need
for detailed analysis and intercomparison in order to understand and reduce the disagreements.
Received: 1 September 2000 / Accepted: 20 April 2001 相似文献
137.
This paper presents a method that incorporates a non‐associated flow rule into the limit analysis to investigate the influence of the dilatancy angle on the factor of safety for the slope stability analysis. The proposed method retain's the advantage of the upper bound method, which is simple and has no stress involvement in the calculation of the energy dissipation and the factor of safety. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
138.
The Etna volcano is located in an apparently anomalous position on the hinge zone of the Apennines subduction and its Na-alkaline geochemistry does not favour a magma source from the deep slab as indicated for the Aeolian K-alkaline magmatism. The steeper dip of the regional foreland monocline at the front of the Apennines in the Ionian Sea than in Sicily, implies a larger rollback of the subduction hinge in the Ionian Sea. Moreover, the lengthening of the Apennines arc needs extension parallel to the arc. Therefore, the larger southeastward subduction rollback of the Ionian lithosphere with respect to the Hyblean plateau in Sicily, should kinematically produce right-lateral transtension and a sort of vertical 'slab window' which might explain (i) the Plio-Pleistocene alkaline magmatism of eastern Sicily (e.g. the Etna volcano) and (ii) the late Pliocene to present right lateral transtensional tectonics and seismicity of eastern Sicily. The area of transfer of different dip and rollback occurs along the inherited Mesozoic passive continental margin between Sicily and the oceanic Ionian Sea, i.e. the Malta escarpment. 相似文献
139.
Stephen A. Royle 《Singapore journal of tropical geography》1997,18(1):89-98
Indonesia is one of the most rapidly developing nations in the world. One important component of its transformation is an industrialisation policy which sees its people utilised by transnational corporations as sources of cheap labour for export goods processing. This has both positive and negative outcomes. This paper explores these issues in a review of Indonesian development strategy with particular reference to Batam Island in Riau Province. 相似文献
140.