全文获取类型
收费全文 | 23068篇 |
免费 | 196篇 |
国内免费 | 130篇 |
专业分类
测绘学 | 355篇 |
大气科学 | 1210篇 |
地球物理 | 4395篇 |
地质学 | 9018篇 |
海洋学 | 2236篇 |
天文学 | 5307篇 |
综合类 | 42篇 |
自然地理 | 831篇 |
出版年
2022年 | 264篇 |
2021年 | 431篇 |
2020年 | 396篇 |
2019年 | 464篇 |
2018年 | 940篇 |
2017年 | 868篇 |
2016年 | 883篇 |
2015年 | 365篇 |
2014年 | 769篇 |
2013年 | 1294篇 |
2012年 | 899篇 |
2011年 | 1093篇 |
2010年 | 1056篇 |
2009年 | 1217篇 |
2008年 | 1042篇 |
2007年 | 1230篇 |
2006年 | 1069篇 |
2005年 | 570篇 |
2004年 | 540篇 |
2003年 | 545篇 |
2002年 | 568篇 |
2001年 | 508篇 |
2000年 | 418篇 |
1999年 | 337篇 |
1998年 | 326篇 |
1997年 | 332篇 |
1996年 | 254篇 |
1995年 | 261篇 |
1994年 | 238篇 |
1993年 | 185篇 |
1992年 | 209篇 |
1991年 | 181篇 |
1990年 | 195篇 |
1989年 | 188篇 |
1988年 | 156篇 |
1987年 | 182篇 |
1986年 | 172篇 |
1985年 | 206篇 |
1984年 | 198篇 |
1983年 | 198篇 |
1982年 | 189篇 |
1981年 | 172篇 |
1980年 | 162篇 |
1979年 | 182篇 |
1978年 | 158篇 |
1977年 | 144篇 |
1976年 | 134篇 |
1975年 | 137篇 |
1974年 | 125篇 |
1973年 | 165篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
A. E. Volvach A. A. Berezhnoi L. N. Volvach I. D. Strepka E. A. Volvach 《Bulletin of the Crimean Astrophysical Observatory》2011,107(1):122-124
Investigations on OH maser lines in comets have been performed with the RT-22 at CrAO. The results of observations of 9P/Temper1
and Lulin C/2007 N3 comets in the OH molecule line at a wavelength of 18 cm are presented. An original technique for observation
data analysis has been developed. The gas production rate of OH molecules in these comets is estimated. 相似文献
82.
I. D. Somerville 《Geological Journal》1979,14(2):69-86
For the first time, minor cyclicity is described from some limestones in the lower part of the Brigantian (D2) succession of the Mold district North Wales which can be traced throughout the area enabling a detailed correlation to be established. The minor cyclicity may have been caused by eustatic sea-level fluctuations. Periods of emergence associated with each regressive phase are demonstrated by the presence of subaerial features and terrestrial deposits. The lateral persistence of the cycles is confirmed by comparison with established faunal and lithological horizons. Correlation with other cyclic Brigantian strata in Yorkshire, Derbyshire and Bristol is briefly discussed. The Asbian/Brigantian (D1/D2) boundary in North Wales is described and distinctive faunal and lithological changes similar to those in the area of the stratotype in north England have been recorded. 相似文献
83.
Karaevskaya E. S. Demidov N. E. Kazantsev V. S. Elizarov I. M. Kaloshin A. G. Petrov A. L. Karlov D. S. Schirrmeister L. Belov A. A. Wetterich S. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(10):1254-1270
Izvestiya, Atmospheric and Oceanic Physics - The archaeal composition of permafrost samples taken during the drilling of frozen marine sediments in the area of the Barentsburg coal mine on the east... 相似文献
84.
A. F. Morozov B. N. Khakhaev O. V. Petrov V. I. Gorbachev G. V. Tarkhanov L. D. Tsvetkov Yu. M. Erinchek A. M. Akhmedov V. A. Krupenik K. Yu. Sveshnikova 《Doklady Earth Sciences》2010,435(1):1483-1486
A thick (200 m) rock salt mass covering Late Archean granitoids was exposed for the first time in the Early Proterozoic volcanogenic-sedimentary
formations in the Onega trough of the east Baltic Shield by the Onega parametric well. The mineral composition of salts, their
geochemical features, and the isotopic composition of carbonate carbon and oxygen have been studied. After fluid inclusions
present in salts, their metamorphism temperature and isotopic composition of helium and argon were determined. The obtained
results give evidence of the fact that rock salts and magnesites associated with them were formed in an evaporate basin with
participation of deep crustal processes. The age of the underlying granitoids (2.716 ± 9 Ma) is determined using the Pb—Pb
method. 相似文献
85.
Javier García-Veigas Luis Gibert Dioni I. Cendón David Artiaga Hugo Corbí Jesús M. Soria Tim K. Lowenstein Enrique Sanz 《Basin Research》2020,32(5):916-948
The Lorca and Fortuna basins are two intramontane Neogene basins located in the eastern Betic Cordillera (SE Spain). During the Late Tortonian—Early Messinian, marine and continental evaporites precipitated in these basins as a consequence of increased marine restriction and isolation. Here we show a stratigraphic correlation between the evaporite records of these basins based on geochemical indicators. We use SO4 isotope compositions and Sr isotopic ratios in gypsum, and halite Br contents to characterize these units and to identify the marine or continental source of the waters feeding the evaporite basins. In addition, we review the available chronological information used to date these evaporites in Lorca (La Serrata Fm), including a thick saline deposit, that we correlate with the First Evaporitic Group in Fortuna (Los Baños Fm). This correlation is also supported by micropalaeontological data, giving a Late Tortonian age for this sequence. The Second Evaporitic Group, (Chicamo Fm), and the Third Evaporitic Group (Rambla Salada Fm) developed only in Fortuna during the Messinian. According to the palaeogeographical scheme presented here, the evaporites of the Lorca and Fortuna basins were formed during the Late Tortonian—Early Messinian, close to the Betic Seaway closure. Sulphate isotope compositions and Sr isotopic ratios of the Ribera Gypsum Mb, at the base of the Rambla Salada Fm (Fortuna basin), match those of the Late Messinian selenite gypsum beds in San Miguel de Salinas, in the near Bajo Segura basin (40 km to the East), and other Messinian Salinity Crisis gypsum deposits in the Mediterranean. According to these geochemical indicators and the uncertainty of the chronology of this unit, the assignment of the Rambla Salada Fm to the MSC cannot be ruled out. 相似文献
86.
Doklady Earth Sciences - Distribution density functions for the sensitivity of a three-coil sounder are constructed as the weighted mean rock volume between the in-phase surfaces of running... 相似文献
87.
88.
This paper addresses the geochemical features of the noble metal disseminated sulfide and Timagnetite mineralization in the rocks of the Kalar group of autonomous gabbro-anorthosite massifs. The investigations suggest that this mineralization was formed in two stages. The first stage is related to the gabbroanorthosites proper and may be promising for low-sulfide PGE mineralization as well as PGE-bearing Ti-magnetite mineralization, while the second stage is linked to the ultrabasic intrusions associated with copper-nickel or chromite mineralization accompanying by PGE. The horizons of low-sulfide mineralization in the gabbro-anorthosites and copper-nickel mineralization in the dunite-pyroxenites are characterized by the Pd predominance over Pt, while the Cr-bearing and Ti-magnetite ores show the Pt predominance over Pd. 相似文献
89.
90.
Thermal characteristics of anisotropic media with inclusions 总被引:1,自引:0,他引:1