全文获取类型
收费全文 | 37607篇 |
免费 | 267篇 |
国内免费 | 220篇 |
专业分类
测绘学 | 728篇 |
大气科学 | 1748篇 |
地球物理 | 7071篇 |
地质学 | 14901篇 |
海洋学 | 3553篇 |
天文学 | 8804篇 |
综合类 | 99篇 |
自然地理 | 1190篇 |
出版年
2022年 | 488篇 |
2021年 | 708篇 |
2020年 | 754篇 |
2019年 | 827篇 |
2018年 | 1696篇 |
2017年 | 1544篇 |
2016年 | 1640篇 |
2015年 | 618篇 |
2014年 | 1422篇 |
2013年 | 2061篇 |
2012年 | 1626篇 |
2011年 | 1912篇 |
2010年 | 1800篇 |
2009年 | 2003篇 |
2008年 | 1777篇 |
2007年 | 1992篇 |
2006年 | 1745篇 |
2005年 | 920篇 |
2004年 | 830篇 |
2003年 | 822篇 |
2002年 | 747篇 |
2001年 | 770篇 |
2000年 | 640篇 |
1999年 | 428篇 |
1998年 | 454篇 |
1997年 | 509篇 |
1996年 | 363篇 |
1995年 | 370篇 |
1994年 | 355篇 |
1993年 | 290篇 |
1992年 | 291篇 |
1991年 | 306篇 |
1990年 | 356篇 |
1989年 | 282篇 |
1988年 | 270篇 |
1987年 | 270篇 |
1986年 | 200篇 |
1985年 | 306篇 |
1984年 | 306篇 |
1983年 | 301篇 |
1982年 | 278篇 |
1981年 | 252篇 |
1980年 | 268篇 |
1979年 | 205篇 |
1978年 | 246篇 |
1977年 | 209篇 |
1976年 | 181篇 |
1975年 | 185篇 |
1974年 | 172篇 |
1973年 | 207篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Studia Geophysica et Geodaetica - 相似文献
94.
A possible mechanism of the ascent of material within the Earth’s crust and mantle is the mechanism of hydroextrusion, i.e.,
the effect of squeezing of material under excess pressure. The major factors that predetermine the high plasticity of the
material and its ability to produce hydroextrusions are high lithostatic pressures and temperatures. The phenomenon of hydroextrusion
can be most clearly illustrated by the example of the origin of salt diapirs. The driving force of hydroextrusions of material
in the crust and mantle is excess pressure, which can result from lateral differences between the densities of rocks (as is
the case during the development of salt diapirs) and phase transitions associated with a volume increase. When the material
of the upper mantle undergoes partial melting with the derivation of basaltic melts at depths of 60–100 km, excess pressures
reach 80 MPa, whereas the plasticity limit of 20% melted rocks is no higher than 5 MPa. As a result, the partially molten
material is forced from the melting region toward zones with lower lithostatic pressures. A local temperature increase in
the transitional zones in the Earth’s mantle at positive dP/dT values of the phase transitions also gives rise to excess pressures, whose values can range from 100 to 800 MPa at a 0.5–3.0%
volume change and which can be the driving force during the origin of mantle plumes.
Original Russian Text ? V.N. Anfilogov, Yu.V. Khachai, 2006, published in Geokhimiya, 2006, No. 8, pp. 873–878. 相似文献
95.
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
96.
97.
98.
CCD photometry data of the T Tauri star H 187 are presented. They show that a new eclipse of this star began at the end of
2004. Since only one eclipse of this star has been observed previously with a duration of 3.5 years, our data indicate that
the eclipses of this object are periodic with a period P=4.9 years between eclipses. Thus, in terms of the absolute duration
of the eclipses and in terms of their relative length as a fraction of the period, H 187 is one of the most exotic objects
in the sky.
__________
Translated from Astrofizika, Vol. 48, No. 4, pp. 529–534 (November 2005). 相似文献
99.
Michel Westphal Evgueni L. Gurevitch Boris V. Samsonov Hugues Feinberg & Jean Pierre Pozzi 《Geophysical Journal International》1998,134(1):254-266
The deep drill hole SG6 in western Siberia (66°N, 78.5°E) penetrated 1.1 km of lower Triassic basalts, which are possibly an extension of the central Siberian Permo– Triassic flood basalt province. About 300 samples of these basalts were progressively demagnetized and measured. Principal component analysis often shows multiple magnetizations carried by haematite and magnetite. The corrected mean inclinations are +77° and −77° for the haematite component. A magnetostratigraphic scale was derived and showed a N–R–N–R–N succession. This is quite different from the Noril'sk and Taimyr typical polarity scale, R–N.
The basalts found in the SG6 deep drill hole are slightly younger than those of central Siberia and Taimyr. They correspond to middle–upper Induan age, whereas the Noril'sk and Taimyr sections correspond to an uppermost Permian and lower Induan age. Altogether they indicate that, after a high output rate of volcanic material near the Permo–Triassic boundary, this activity slowed down drastically on the Siberian platform and Taimyr, but persisted for several million years in western Siberia. 相似文献
The basalts found in the SG6 deep drill hole are slightly younger than those of central Siberia and Taimyr. They correspond to middle–upper Induan age, whereas the Noril'sk and Taimyr sections correspond to an uppermost Permian and lower Induan age. Altogether they indicate that, after a high output rate of volcanic material near the Permo–Triassic boundary, this activity slowed down drastically on the Siberian platform and Taimyr, but persisted for several million years in western Siberia. 相似文献
100.
This paper discusses the dynamic response of a curved bridge deck to a moving vehicle. The bridge deck is idealized as a set of annular sector plates and circular rings rigidly jointed together. On the basis of classical plate and ring theories a method has been developed to obtain the response to a moving vehicle idealized as a spring mass system. After obtaining the normal modes and frequencies and establishing the orthogonality conditions, the problem of the forced motion of the deck is solved by the method of spectral representation. Numerical results have been presented to illustrate the effect of several vehicle and bridge parameters on the response. 相似文献