全文获取类型
收费全文 | 110731篇 |
免费 | 1847篇 |
国内免费 | 1053篇 |
专业分类
测绘学 | 2481篇 |
大气科学 | 7710篇 |
地球物理 | 21666篇 |
地质学 | 39628篇 |
海洋学 | 10235篇 |
天文学 | 25043篇 |
综合类 | 325篇 |
自然地理 | 6543篇 |
出版年
2022年 | 686篇 |
2021年 | 1184篇 |
2020年 | 1292篇 |
2019年 | 1421篇 |
2018年 | 2977篇 |
2017年 | 2752篇 |
2016年 | 3344篇 |
2015年 | 1800篇 |
2014年 | 3175篇 |
2013年 | 5835篇 |
2012年 | 3537篇 |
2011年 | 4661篇 |
2010年 | 4159篇 |
2009年 | 5407篇 |
2008年 | 4692篇 |
2007年 | 4784篇 |
2006年 | 4402篇 |
2005年 | 3335篇 |
2004年 | 3208篇 |
2003年 | 3038篇 |
2002年 | 2964篇 |
2001年 | 2589篇 |
2000年 | 2560篇 |
1999年 | 2119篇 |
1998年 | 2143篇 |
1997年 | 2027篇 |
1996年 | 1768篇 |
1995年 | 1695篇 |
1994年 | 1447篇 |
1993年 | 1387篇 |
1992年 | 1302篇 |
1991年 | 1334篇 |
1990年 | 1288篇 |
1989年 | 1135篇 |
1988年 | 1070篇 |
1987年 | 1230篇 |
1986年 | 1126篇 |
1985年 | 1356篇 |
1984年 | 1530篇 |
1983年 | 1463篇 |
1982年 | 1357篇 |
1981年 | 1266篇 |
1980年 | 1118篇 |
1979年 | 1065篇 |
1978年 | 1062篇 |
1977年 | 894篇 |
1976年 | 878篇 |
1975年 | 875篇 |
1974年 | 854篇 |
1973年 | 923篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
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
142.
143.
David A. Williams 《Planetary and Space Science》1992,40(12):1683-1693
We review the present understanding of interstellar CH+. We show that the essential chemistry was correctly identified by Bates and Spitzer in 1951. More recent work has been concerned with defining appropriate venues within which this chemistry can function efficiently. This process had led to a much fuller understanding of the nature of the interstellar medium. 相似文献
144.
The restricted problem of 2 + 2 bodies when one of the infinitesimal masses is further acted upon by the light pressure of the two primaries, is considered. The stationary solutions of this problem are found out. A short discussion is devoted to the stability of these solutions. 相似文献
145.
Perspectives for the Radio-Optical Telescope 54/32/2.6 are given for scientific research in radioastronomy. Its characteristics and potential scientific fields are summarized in the frame of the present French-Armenian collaboration. A 3-phase upgrade plan including a detailed technical evaluation of the antenna is presented.Published in Astrofizika, Vol. 38, No. 4, pp. 645–648, October–December, 1995. 相似文献
146.
We have studied the influence of the magnetic helicity on solar particle propagation using the IMF data observed by the HELIOS spacecraft in the range 0.31–0.95 AU, during eight solar proton events. For this, we have derived power and helicity spectra of the turbulence of the magnetic field during the time of the events. These are used to compute the particle pitch-angle scattering coefficients according to the quasi-linear theory (QLT) treatment of particle propagation in turbulent magnetic fields. The results show that in all the cases the helicity effects are negligible and the particle's mean free paths deduced from the pitch-angle diffusion coefficients are the same regardless of whether or not helicity effects are included in the calculations. The computed mean free paths are quite different in each case.Deceased 10 April, 1995. 相似文献
147.
K. A. van der Hucht 《Astronomy and Astrophysics Review》1992,4(2):123-159
Summary Recent literature on Population I Wolf-Rayet star research extending from the Milky Way to blue compact dwarf galaxies is reviewed, broken down into inventory, basic parameters and galactic distribution, atmospheres, binaries, intrinsic variability, mass loss, enrichment and evolution. Also the incidence of Wolf-Rayet stars with variable non-thermal radio emission, excess X-ray fluxes, and episodic/periodic IR excesses is reviewed. These phenomena appear to be associated with wind-wind interaction in wide long-period WR+OB binaries and with wind-compact object interaction in WR+c binaries, with orbit sizes of the order of magnitude of the WR radio photosphere sizes or larger. 相似文献
148.
G. Cevolani G. Bortolotti L. Foschini C. Franceschi G. Grassi G. Trivellone A. Hajduk V. Porubčan 《Earth, Moon, and Planets》1995,68(1-3):247-255
Continuous radio-wave monitoring of the Geminid activity in December 1992 and 1993 by using a forward scatter (FS) bistatic radar over the Bologna-Lecce baseline (700 km) in Italy, reveals peculiar structural aspects of the stream in terms of signal amplitude-rate and duration-rate dependence. The observational results of the Geminid display obtained in the two consecutive years with differentiated peak levels of transmitted power, exhibit different time distributions of underdense meteors against the signal received power. Both sets of the data relative to the peak activity in December 12–14, show reflection properties of Geminids which are atypical if compared with echoes from cometary-type showers, with really high echo counts at mid-upper levels of the peak received power. An assymmetric curve of activity of the Geminids complex is evidenced, with the peak flux of smaller particles occurring earlier than that of larger ones. 相似文献
149.
Swath bathymetric, gravity, and magnetic studies were carried out over a 55 km long segment of the Central Indian Ridge.
The ridge is characterized by 12 to 15 km wide rift valley bounded by steep walls and prominent volcanic constructional ridges
on either side of the central rift valley. A transform fault at 7°45′S displaces the ridge axis. A mantle Bouguer anomaly
low of −14 mGals and shallowing of rift valley over the middle of the ridge segment indicate along axis crustal thickness
variations. A poorly developed neovolcanic zone on the inner rift valley floor indicate dominance of tectonic extension. The
off-axis volcanic ridgs suggest enhanced magmatic activity during the recent past.
Received: 24 May 1996 / Rivision received: 13 January 1997 相似文献
150.
We present special generating plane orbits, the vertical-critical orbits, of the coplanar general three-body problem. These
are determined numerically for various values of m3, for the entire range of the mass ratio of the two primaries. The vertical-critical orbits are necessary in order to specify
the vertically stable segments of the families of plane periodic orbits, and they are also the starting points of the families
of the simplest possible three-dimensional periodic orbits, namely the simple and double periodic. The initial conditions
of the vertical-critical periodic orbits of the basic families l, m, i, h, b and c and their stability parameters are determined.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献