全文获取类型
收费全文 | 72911篇 |
免费 | 724篇 |
国内免费 | 558篇 |
专业分类
测绘学 | 1962篇 |
大气科学 | 4473篇 |
地球物理 | 13418篇 |
地质学 | 28967篇 |
海洋学 | 6168篇 |
天文学 | 16149篇 |
综合类 | 272篇 |
自然地理 | 2784篇 |
出版年
2022年 | 536篇 |
2021年 | 829篇 |
2020年 | 897篇 |
2019年 | 1016篇 |
2018年 | 4159篇 |
2017年 | 3725篇 |
2016年 | 3259篇 |
2015年 | 1072篇 |
2014年 | 1952篇 |
2013年 | 3109篇 |
2012年 | 2889篇 |
2011年 | 4560篇 |
2010年 | 4071篇 |
2009年 | 4707篇 |
2008年 | 3966篇 |
2007年 | 4569篇 |
2006年 | 2679篇 |
2005年 | 1853篇 |
2004年 | 1799篇 |
2003年 | 1770篇 |
2002年 | 1585篇 |
2001年 | 1319篇 |
2000年 | 1235篇 |
1999年 | 930篇 |
1998年 | 925篇 |
1997年 | 944篇 |
1996年 | 704篇 |
1995年 | 722篇 |
1994年 | 712篇 |
1993年 | 576篇 |
1992年 | 562篇 |
1991年 | 518篇 |
1990年 | 596篇 |
1989年 | 496篇 |
1988年 | 473篇 |
1987年 | 505篇 |
1986年 | 400篇 |
1985年 | 586篇 |
1984年 | 606篇 |
1983年 | 587篇 |
1982年 | 555篇 |
1981年 | 498篇 |
1980年 | 522篇 |
1979年 | 398篇 |
1978年 | 431篇 |
1977年 | 395篇 |
1976年 | 341篇 |
1975年 | 357篇 |
1974年 | 337篇 |
1973年 | 358篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
101.
E.A. Evstigneeva R.R. de Carvalho A.L. Ribeiro H.V. Capelato 《Astrophysics and Space Science》2003,284(2):487-490
We present the preliminary results of a study of how small stellar systems merge to form larger ones. As we display the families
of galaxies in the μe - Re plane (effective surface brightness versus effective radius) we realize that different morphological types occupy different
loci, evidencing the different physical mechanisms operating in each family. As proposed by Capaccioli et al. (1992) this
diagram is the logical equivalent of the HR diagram for stars. Here we take some initial steps in understanding of how we
can establish the evolutionary tracks, solely due to dynamical processes, in the μe - Re plane, ultimately making a dwarf elliptical to turn into a normal elliptical galaxy.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
102.
Green Lake Landslide is an ancient giant rock slide in gneiss and granodiorite located in the deeply glaciated Fiordland region of New Zealand. The landslide covers an area of 45 km2 and has a volume of about 27 km3. It is believed to be New Zealand's largest landslide, and possibly the largest landslide of its type on Earth. It is one of 39 known very large (106–107 m3) and giant (≥108 m3) postglacial landslides in Fiordland discussed in the paper. Green Lake Landslide resulted in the collapse of a 9 km segment of the southern Hunter Mountains. Slide debris moved up to 2.5 km laterally and 700 m vertically, and formed a landslide dam about 800 m high, impounding a lake about 11 km long that was eventually infilled with sediments. Geomorphic evidence supported by radiocarbon dating indicates that Green Lake Landslide probably occurred 12 000–13 000 years ago, near the end of the last (Otira) glaciation. The landslide is described, and its geomorphic significance, age, failure mechanism, cause, and relevance in the region are discussed, in relation to other large landslides and recent earthquake-induced landslides in Fiordland. The slope failure occurred on a low-angle fault zone undercut by glacial erosion, and was probably triggered by strong shaking (MM IX–X) associated with a large (≥ M 7.5–8) earthquake, on the Alpine Fault c. 80 km to the northwest. Geology was a major factor that controlled the style and size of Green Lake landslide, and in that respect it is significantly different from most other gigantic landslides. Future large earthquakes on the Alpine Fault in Fiordland are likely to trigger more very large and giant landslides across the region, causing ground damage and devastation on a scale that has not occurred during the last 160 years, with potentially disastrous effects on towns, tourist centres, roads, and infrastructure. The probability of such an event occurring within the next 50 years may be as high as 45%. 相似文献
103.
V. G. Gorbatskii 《Astrophysics》1990,32(2):149-154
Leningrad State University. Translated from Astrofizika, Vol. 32, No. 2, pp. 267–275, March–April, 1990. 相似文献
104.
V. J. Mclntyre A. C. Gilmore J. B. Hearnshaw 《Journal of Astrophysics and Astronomy》1990,11(1):81-123
Photographic spectra of SN1987A in the LMC have been obtained from 1987 February 25 to 1988 June 30. Microdensitometer tracings
of these have been reduced to intensity and corrections for instrumental response have been applied to the spectra. This paper
presents these data in an atlas format, discusses the reduction procedures in detail, and presents radial velocity measurements
of selected lines in the spectra 相似文献
105.
In this paper we analyse error-removing techniques used without sufficient theoretical support in a previous paper, where Chandrasekhar's higher-order perturbation theories were developed for either uniformly or differentially-rotating polytropic stars. 相似文献
106.
Solutions of field equations of the generalized theory of gravitation for neutral and charged point masses are found. The problem is formulated so that the solution may be expressed in harmonic, isotropic, Schwarzschild and, if necessary, any other coordinates. A method for the solution of the static axisymmetric problem (an analogue of a well-known Weyl's solution) is also proposed. 相似文献
107.
108.
The Bloomington meteorite, a 67.8 gram veined, brecciated chondrite, fell during the summer of 1938 in Bloomington, Illinois. Its olivine, orthopyroxene and metal compositions (fo69, en74 and Fe52 Ni48 respectively) and its texture identify it as a brecciated LL6 chondrite of shock facies d. Shock melt glasses occur in Bloomington as sparse melt pockets and veins in clasts and as isolated masses in the black, clast-rich matrix. The vein glasses chemically resemble bulk LL-group chondrites and thus appear to reflect total melting of the host meteorite. The melt pocket and matrix glasses, like those described previously in L-group chondrites, have more varied compositions and are typically enriched in normative plagioclase. All glasses that we analyzed in Bloomington have FeO/MgO and Na/Al ratios similar to those of LL-group chondrites, indicating that melting of this meteorite involved neither a significant change in the oxidation state of iron nor loss of sodium to a vapor phase. Bloomington is a monomict breccia whose components formed in place as a result of a single episode of shock and attendant melting. 相似文献
109.
110.
Observations of the brightness, color, and polarization of the fuor V1057 Cyg over more than 30 years are presented and briefly discussed. Variability of the linear polarization was found. 相似文献