全文获取类型
收费全文 | 129344篇 |
免费 | 1754篇 |
国内免费 | 1040篇 |
专业分类
测绘学 | 3163篇 |
大气科学 | 8660篇 |
地球物理 | 25645篇 |
地质学 | 46060篇 |
海洋学 | 11230篇 |
天文学 | 29665篇 |
综合类 | 368篇 |
自然地理 | 7347篇 |
出版年
2022年 | 770篇 |
2021年 | 1325篇 |
2020年 | 1474篇 |
2019年 | 1553篇 |
2018年 | 3419篇 |
2017年 | 3235篇 |
2016年 | 3909篇 |
2015年 | 2126篇 |
2014年 | 3766篇 |
2013年 | 6793篇 |
2012年 | 3977篇 |
2011年 | 5251篇 |
2010年 | 4655篇 |
2009年 | 5936篇 |
2008年 | 5444篇 |
2007年 | 5459篇 |
2006年 | 5037篇 |
2005年 | 3842篇 |
2004年 | 3720篇 |
2003年 | 3477篇 |
2002年 | 3267篇 |
2001年 | 3081篇 |
2000年 | 2835篇 |
1999年 | 2370篇 |
1998年 | 2424篇 |
1997年 | 2394篇 |
1996年 | 1950篇 |
1995年 | 1956篇 |
1994年 | 1736篇 |
1993年 | 1587篇 |
1992年 | 1551篇 |
1991年 | 1497篇 |
1990年 | 1664篇 |
1989年 | 1464篇 |
1988年 | 1360篇 |
1987年 | 1543篇 |
1986年 | 1296篇 |
1985年 | 1694篇 |
1984年 | 1896篇 |
1983年 | 1778篇 |
1982年 | 1696篇 |
1981年 | 1545篇 |
1980年 | 1422篇 |
1979年 | 1315篇 |
1978年 | 1344篇 |
1977年 | 1204篇 |
1976年 | 1161篇 |
1975年 | 1068篇 |
1974年 | 1129篇 |
1973年 | 1116篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
M. V. Ramana 《Geo-Marine Letters》1986,6(1):1-5
Satellite imagery and offshore magnetic data were analysed to correlate regional tectonic elements on the inner continental
shelf off Konkan and the adjacent Deccan plateau. Three statistically important lineament trends—N-S, WNW-ESE and ENE-WSW—that
prevail on land are correlatable well with the offshore trends. This positive correlation suggests simultaneous deformation.
The major magnetic lineament observed off Jaigad Bay, west coast of India, may be the extension of onshore lineaments. The
correlation of both the offshore and onshore trends indicates that the fracture pattern of the crystalline basement has also
controlled the offshore structural pattern. 相似文献
162.
Trends in emigration from Ireland over time are reviewed. "During the eighteenth and nineteenth centuries overseas migration to the United States and seasonal harvest migration to Britain were the main types of movement, but over the past 100 years the Irish have developed a special affinity for settling in British towns. Although the outflow was halted for a time during the 1970s, when return migration took over, the 1980s have seen a renewal of the exodus. This time, however, the character of the flow has changed from predominantly low-skill construction and factory workers to embrace better-educated emigrants, including many graduates. This shift reflects Ireland's changing position in the international market for labour." 相似文献
163.
M. J. Martres 《Solar physics》1989,119(2):357-384
This paper consists of two parts. We first discuss recent general results on the study of properties of flare homology, and their relevance to the physical interpretation of the flare phenomenon at large. We devote particular attention to the discovery of homologous flares which occur in rapid succession, within a few minutes of each other in many cases. We name these kind of flares rafales. These flares signal the existence of several episodes of energy release within the same magnetic configuration. We also show the existence of particular sites in the solar atmosphere which have peculiar characteristics in terms of solar rotation, and where recurrent flaring may take place over and over again in different solar rotations. This indicates that the disturbance causing the emergence of activity is deep seated, below the solar photosphere. Finally, in the second part, we discuss an extensive set of observations of two homologous flares of a rafale, stressing the dynamic aspects of the observations, particularly the presence of peaks in the vertical component of the velocity field. These results are shown to be in agreement with studies of filament activations and the surging arches which are observed before the flash phase of solar flares. 相似文献
164.
Sofer M 《Singapore journal of tropical geography》1992,13(2):118-129
The author examines circular labor migration in Fiji. "This paper is organized into five sections. The first section provides a brief discussion of two major perspectives of labour circulation in developing countries. The second section presents the state of the Fijian village in the context of the current pattern of uneven development in Fiji. The practice of labour circulation by Fijian villagers is dealt with in the third section. In the last two sections, issues concerning the maintenance of the polarized pattern and the preservation of the village mode of production are discussed." 相似文献
165.
166.
167.
This study considers the influence of the effects of scattering due to Langmuir turbulent pulsations in the transfer of radiation in the spectral lines. The transfer equation of radiation in spectral lines, by taking into account scattering due to Langmuir turbulent pulsations, is written in a form convenient for application by numerical methods.The profile's intensity for a plane-parallel finite isothermal slab of a turbulent plasma in the case of complete redistribution of scattering by an atom are obtained. Numerical studies show that in this case with the broadening of spectral lines and the decreasing of self-reversal, the Langmuir frequency
pe is of the same order as the electronic Doppler width
De. Creation of the line satellites when
pe is larger than the line width is shown with the aid of numerical methods. 相似文献
168.
We present a simple model for the formation and growth of photochemical aerosols in the atmosphere of Titan. We show that, in general, an optically thick layer of particles in the size range required by models of Titan cannot be obtained at pressures less than about 2 mbar. Since the thin model of Titan's atmosphere requires that the inversion not extend below pressures of 0.11 mbar (D. M. Hunten and J. J. Caldwell, 1978, preprint), it seems to be ruled out by the calculations. 相似文献
169.
170.
Detailed studies of the daytime E-region critical frequency at Aberystwyth (geomagnetic latitude +56°) show clear evidence for changes associated with both the axially-symmetric (Dst) and asymmetric (DS) components of the disturbance magnetic field. Comparison of the sensitivity of the E-region peak density to these two influences shows that the changes cannot entirely (if at all) be ascribed to the influence of electric currents in the region. It is suggested that a major role is played by dynamical influences associated with the neutral air “storm circulation” which distributes the energy fed into the auroral region to lower latitudes. 相似文献