全文获取类型
收费全文 | 23397篇 |
免费 | 247篇 |
国内免费 | 137篇 |
专业分类
测绘学 | 371篇 |
大气科学 | 1232篇 |
地球物理 | 4445篇 |
地质学 | 9238篇 |
海洋学 | 2282篇 |
天文学 | 5301篇 |
综合类 | 41篇 |
自然地理 | 871篇 |
出版年
2022年 | 267篇 |
2021年 | 435篇 |
2020年 | 401篇 |
2019年 | 468篇 |
2018年 | 959篇 |
2017年 | 871篇 |
2016年 | 901篇 |
2015年 | 376篇 |
2014年 | 788篇 |
2013年 | 1317篇 |
2012年 | 926篇 |
2011年 | 1108篇 |
2010年 | 1075篇 |
2009年 | 1229篇 |
2008年 | 1058篇 |
2007年 | 1227篇 |
2006年 | 1081篇 |
2005年 | 584篇 |
2004年 | 545篇 |
2003年 | 557篇 |
2002年 | 569篇 |
2001年 | 520篇 |
2000年 | 416篇 |
1999年 | 340篇 |
1998年 | 329篇 |
1997年 | 333篇 |
1996年 | 260篇 |
1995年 | 269篇 |
1994年 | 239篇 |
1993年 | 185篇 |
1992年 | 215篇 |
1991年 | 189篇 |
1990年 | 202篇 |
1989年 | 190篇 |
1988年 | 161篇 |
1987年 | 188篇 |
1986年 | 174篇 |
1985年 | 215篇 |
1984年 | 204篇 |
1983年 | 205篇 |
1982年 | 195篇 |
1981年 | 175篇 |
1980年 | 167篇 |
1979年 | 188篇 |
1978年 | 165篇 |
1977年 | 145篇 |
1976年 | 137篇 |
1975年 | 142篇 |
1974年 | 127篇 |
1973年 | 174篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
Astronomy Letters - Based on published data, we have produced a sample of 256 radio sources whose trigonometric parallaxes and proper motions were measured by VLBI. This sample contains Galactic... 相似文献
992.
Khamitov I. M. Bikmaev I. F. Burenin R. A. Glushkov M. V. Melnikov S. S. Lyapin A. R. 《Astronomy Letters》2020,46(1):1-11
Astronomy Letters - An example of simultaneous spectroscopic redshift measurements for a large number of galaxies in a cluster by multiobject spectroscopy with the medium- and low-resolution TFOSC... 相似文献
993.
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
994.
Renas I. Koshnaw Brian K. Horton Daniel F. Stockli Douglas E. Barber Mazin Y. Tamar-Agha 《Basin Research》2020,32(4):688-715
In the northwestern sector of the Zagros foreland basin, axial fluvial systems initially delivered fine-grained sediments from northwestern source regions into a contiguous basin, and later transverse fluvial systems delivered coarse-grained sediments from northeastern sources into a structurally partitioned basin by fold-thrust deformation. Here we integrate sedimentologic, stratigraphic, palaeomagnetic and geochronologic data from the northwestern Zagros foreland basin to define the Neogene history of deposition and sediment routing in response to progressive advance of the Zagros fold-thrust belt. This study constrains the depositional environments, timing of deposition and provenance of nonmarine clastic deposits of the Injana (Upper Fars), Mukdadiya (Lower Bakhtiari) and Bai-Hasan (Upper Bakhtiari) Formations in the Kurdistan region of Iraq. Sediments of the Injana Formation (~12.4–7.75 Ma) were transported axially (orogen-parallel) from northwest to southeast by meandering and low-sinuosity channel belt system. In contrast, during deposition of the Mukdadiya Formation (~7.75–5 Ma), sediments were delivered transversely (orogen-perpendicular) from northeast to southwest by braided and low-sinuosity channel belt system in distributive fluvial megafans. By ~5 Ma, the northwestern Zagros foreland basin became partitioned by growth of the Mountain Front Flexure and considerable gravel was introduced in localized alluvial fans derived from growing topographic highs. Foredeep accumulation rates during deposition of the Injana, Mukdadiya and Bai-Hasan Formations averaged 350, 400 and 600 m/Myr respectively, suggesting accelerated accommodation generation in a rapidly subsiding basin governed by flexural subsidence. Detrital zircon U-Pb age spectra show that in addition to sources of Mesozoic-Cenozoic cover strata, the Injana Formation was derived chiefly from Palaeozoic-Precambrian (including Carboniferous and latest Neoproterozoic) strata in an axial position to the northwest, likely from the Bitlis-Puturge Massif and broader Eastern Anatolia. In contrast, the Mukdadiya and Bai-Hasan Formations yield distinctive Palaeogene U-Pb age peaks, particularly in the southeastern sector of the study region, consistent with transverse delivery from the arc-related terranes of the Walash and Naopurdan volcano-sedimentary groups (Gaveh-Rud domain?) and Urumieh-Dokhtar magmatic arc to the northeast. These temporal and spatial variations in stratigraphic framework, depositional environments, sediment routing and compositional provenance reveal a major drainage reorganization during Neogene shortening in the Zagros fold-thrust belt. Whereas axial fluvial systems initially dominated the foreland basin during early orogenesis in the Kurdistan region of Iraq, transverse fluvial systems were subsequently established and delivered major sediment volumes to the foreland as a consequence of the abrupt deformation advance and associated topographic growth in the Zagros. 相似文献
995.
Shibing Zhu Qu Yi Liu Yingzhu Dobrynin D. V. Sukhova O. V. Kotlov I. P. Sandlersky R. B. Yachmennikova A. A. Rozhnov V. V. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(9):1107-1126
Izvestiya, Atmospheric and Oceanic Physics - The population of the Amur tiger (Panthera tigris altaica) in the Russian Far East is currently being restored; young individuals are being spread... 相似文献
996.
Ivanova J. N. Vyhristenko R. I. Vikentyev I. V. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(12):1537-1545
Izvestiya, Atmospheric and Oceanic Physics - The central part of the Malouralsky volcanic–plutonic belt, which includes the Manyukuyu–Vorchatinsky ore cluster, is analyzed using... 相似文献
997.
Sadovsky I. N. Kuzmin A. V. Khapin Yu. B. Kozlova T. O. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(12):1741-1750
Izvestiya, Atmospheric and Oceanic Physics - The MIRS microwave radiometer–spectrometer is described. The instrument is being developed using a conceptual design that was the first stage of... 相似文献
998.
Izvestiya, Atmospheric and Oceanic Physics - Data on the relative contribution of the Ox, HOx, NOx, ClOx, BrOx, and IOx catalytic cycles to atmospheric ozone destruction are given for June and... 相似文献
999.
Oceanology - Abstract—The paper studies carbon transformation and transfer processes in the crust and mantle. Sediments dragged into subduction zones are dewatered, broken down, and altered... 相似文献
1000.
Gordeev V. V. Dara O. M. Alekseeva T. N. Kochenkova A. I. Boev A. G. Lokhov A. S. Belorukov S. K. 《Oceanology》2020,60(3):384-392
Oceanology - The paper presents the first results of a study of seasonal variations in the grain size distribution and mineral compositions of suspended particulate matter (SPM) of the Northern... 相似文献