全文获取类型
收费全文 | 7518篇 |
免费 | 1125篇 |
国内免费 | 1754篇 |
专业分类
测绘学 | 97篇 |
大气科学 | 212篇 |
地球物理 | 833篇 |
地质学 | 4835篇 |
海洋学 | 761篇 |
天文学 | 2149篇 |
综合类 | 318篇 |
自然地理 | 1192篇 |
出版年
2024年 | 67篇 |
2023年 | 184篇 |
2022年 | 367篇 |
2021年 | 353篇 |
2020年 | 336篇 |
2019年 | 345篇 |
2018年 | 311篇 |
2017年 | 298篇 |
2016年 | 303篇 |
2015年 | 331篇 |
2014年 | 325篇 |
2013年 | 386篇 |
2012年 | 356篇 |
2011年 | 357篇 |
2010年 | 312篇 |
2009年 | 555篇 |
2008年 | 442篇 |
2007年 | 490篇 |
2006年 | 541篇 |
2005年 | 409篇 |
2004年 | 404篇 |
2003年 | 449篇 |
2002年 | 364篇 |
2001年 | 305篇 |
2000年 | 308篇 |
1999年 | 258篇 |
1998年 | 281篇 |
1997年 | 191篇 |
1996年 | 144篇 |
1995年 | 126篇 |
1994年 | 133篇 |
1993年 | 88篇 |
1992年 | 84篇 |
1991年 | 44篇 |
1990年 | 46篇 |
1989年 | 27篇 |
1988年 | 21篇 |
1987年 | 23篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
S. ENDO S.WALLIS T. HIRATA R. ANCZKIEWICZ J. PLATT M. THIRLWALL Y. ASAHARA 《Journal of Metamorphic Geology》2009,27(5):371-384
Two distinct age estimates for eclogite-facies metamorphism in the Sanbagawa belt have been proposed: (i) c. 120–110 Ma based on a zircon SHRIMP age for the Western Iratsu unit and (ii) c. 88–89 Ma based on a garnet–omphacite Lu–Hf isochron age from the Seba and Kotsu eclogite units. Despite the contrasting estimates of formation ages, petrological studies suggest the formation conditions of the Western Iratsu unit are indistinguishable from those of the other two units—all ∼20 kbar and 600–650 °C. Studies of the associated geological structures suggest the Seba and Western Iratsu units are parts of a larger semi-continuous eclogite unit. A combination of geochronological and petrological studies for the Western Iratsu eclogite offers a resolution to this discrepancy in age estimates. New Lu–Hf dating for the Western Iratsu eclogite yields an age of 115.9 ± 0.5 Ma that is compatible with the zircon SHRIMP age. However, petrological studies show that there was significant garnet growth in the Western Iratsu eclogite before eclogite facies metamorphism, and the early core growth is associated with a strong concentration of Lu. Pre-eclogite facies garnet (Grt1) includes epidote–amphibolite facies parageneses equilibrated at 550–650 °C and ∼10 kbar, and this is overgrown by prograde eclogite facies garnet (Grt2). The Lu–Hf age of c. 116 Ma is strongly skewed to the isotopic composition of Grt1 and is interpreted to reflect the age of the pre-eclogite phase. The considerable time gap ( c. 27 Myr) between the two Lu–Hf ages suggests they may be related to separate tectonic events or distinct phases in the evolution of the Sanbagawa subduction zone. 相似文献
2.
Nikos Prantzos 《Astrophysics and Space Science》2003,284(2):675-684
We develop a detailed model of the Milky Way (a `prototypical' disk galaxy) and extend it to other disks with the help of
some simple scaling relations, obtained in the framework of Cold Dark Matter models. This phenomenological (`hybrid') approach
to the study of disk galaxy evolution allows us to reproduce successfully a large number of observed properties of disk galaxies
in the local Universe and up to redshift z ∼ 1. The important conclusion is that, on average, massive disks have formed the bulk of their stars earlier than their lower
mass counterparts: the `star formation hierarchy' has been apparently opposite to the `dark matter assembly' hierarchy. It
is not yet clear whether `feedback' (as used in semi-analytical models of galaxy evolution) can explain that discrepancy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
4.
R. Surendiranath N. Kameswara Rao Ram Sagar J. S. Nathan K. K. Ghosh 《Journal of Astrophysics and Astronomy》1990,11(2):151-166
bdAbstract The open cluster NGC 2818 containing a planetary nebula has been observed inVRI bands using the CCD system at prime focus of the 2.3-metre Vainu Bappu Telescope. The study extending to starsV ∼ 21 magnitude establishes the distance modulus as(m-M)
0 = 12.9 ±0.1 for the cluster. Based on the fitting of theoretical isochrones computed for solar metallicity, an age of 5(±1)
× 108 years has been assigned to the cluster. Association of the planetary nebula with the cluster indicates that the progenitor
mass of the planetary nebula on the main sequence is ≥2.5M⊙
Based on observations obtained with the Vainu Bappu Telescope. 相似文献
5.
6.
J. Dommanget 《Journal of Astrophysics and Astronomy》2003,24(3-4):99-109
A research that we conducted in 1963 on the evolution of the binaries based on the available orbital data to obtain a philosophical
degree, led to the establishment of an interesting and new diagram between the logarithm of the total mass and a particular
parameterX, bound to the areal constant. This appeared to have a real physical significance but the basic observational material was
insufficiently extended to assure its undeniable existence. In 1981, a new research based on a more extended orbital material,
has confirmed this diagram. Presently, another important increase in the orbital material and the availability of highly accurate
trigonometric parallaxes produced by the Hipparcos satellite, gave us the opportunity to confirm once more the stability of
this diagram. This last research is here described. 相似文献
7.
8.
9.
10.