全文获取类型
收费全文 | 494篇 |
免费 | 44篇 |
国内免费 | 109篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 12篇 |
地球物理 | 87篇 |
地质学 | 331篇 |
海洋学 | 150篇 |
天文学 | 2篇 |
综合类 | 21篇 |
自然地理 | 38篇 |
出版年
2024年 | 4篇 |
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 15篇 |
2020年 | 14篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 26篇 |
2013年 | 34篇 |
2012年 | 21篇 |
2011年 | 31篇 |
2010年 | 21篇 |
2009年 | 29篇 |
2008年 | 31篇 |
2007年 | 30篇 |
2006年 | 40篇 |
2005年 | 27篇 |
2004年 | 22篇 |
2003年 | 18篇 |
2002年 | 25篇 |
2001年 | 21篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 11篇 |
1997年 | 23篇 |
1996年 | 18篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有647条查询结果,搜索用时 15 毫秒
51.
S. O. Zorina 《Stratigraphy and Geological Correlation》2007,15(3):267-276
The work is aimed at litho-, bio- and magnetostratigraphic subdivision of the Middle-Upper Jurassic sedimentary succession in the northeast of the Ul’yanovsk-Saratov depression (the East Russian plate). Problems of regional and interregional correlation of distinguished subdivisions are considered. As is shown, the ammonite biostratigraphy is most effective method for solving problems of chronostratigraphy. 相似文献
52.
53.
54.
Globally, an estimated land area of 9.55×108 ha is affected by salinity and sodicity[1]. In the Yellow River Delta, saline-alkali land covers more than 70% of the total area. Soil salinization is the key factor that influences sustainable agricultural development. Geographic information system (GIS) is a powerful tool for spatial data analysis, which can be used to analyze data from different sources for saline-alkali land monitoring. Based on GIS, zonation of saline-alkali land can provi… 相似文献
55.
Vertical distribution of the dominant planktonic crustaceans in a mesotrophic reservoir, Xujiahe reservoir (central China) 总被引:1,自引:0,他引:1
The day and night vertical distributions of the dominant planktonic crustaceans in Xujiahe Reservoir were investigated on July 7, 1998. Sampling was carried out at Station D in the upstream region, Doupuohe, and Stations LI and LII in the downstream region, Lujiaodao. At Station D and Station LI, Leptodora kindti showed diel vertical migrations. In Daphnia galeata and Diaphanosoma dubia a limited reverse diel vertical migration was found at Station D, and large individuals tended to stay in lower layers during the day. Neutrodiaptomus incongruens seemed to avoid the water column of 0–6 m by day, but a detectable proportion of the population moved upwards at night. Mesocyclops thermocyclopoides showed a clearly defined diel vertical migration behavior at all three stations. The vertical distribution of Thermocyclops crassus was similar at different stations: in daylight hours it was found almost exclusively in the water column below 6 m and during the night a significant proportion of the population shifted upwards. 相似文献
56.
Down-core variation in planktonic foraminifera (PF) at Site 1143 (ODP 184) has disclosed the evolution of upper water-column
structure over the last 12 Ma in the southern South China Sea. In the early Late Miocene (∽10.6–7.8 Ma), there existed a lower
percentage of total deep-dwelling species, reflecting a water thermocline deeper than that in the Middle Miocene, which resulted
from the closure of Indonesian seaway and relevant intensification of the equatorial warm current. After the increase in deep-dwelling
PF and the rising of thermocline during the late Late Miocene (7.6–6.4 Ma), the total deep-dwelling species decreased gradually
from late Late Miocene (6.4 Ma) to the Pliocene, implying the deepening of water thermocline. The evolution of thermocline
depth in the southern South China Sea reflected by the PF at Site 1143 might be a good indicator of the change of west Pacific
“warm pool”. 相似文献
57.
Fluid-rock history of granulite facies humite-marbles from Ambasamudram, southern India. 总被引:1,自引:0,他引:1
An extensive humite‐bearing marble horizon within a supracrustal sequence at Ambasamudram, southern India, was studied using petrological and stable isotopic techniques to define its metamorphic history and fluid characteristics. At peak metamorphic temperatures of 775±73°C, based on calcite‐graphite carbon isotope thermometry, the mineral assemblages suggest layer‐by‐layer control of fluid compositions. Clinohumite + calcite‐bearing assemblages suggest XCO2 < 0.4 (at 700°C and 5 kbar), calcite + forsterite + K‐feldspar‐bearing assemblages suggest XCO2>0.9 (at 790°C); and local wollastonite + scapolite + grossular‐bearing zones formed at XCO2 of c. 0.3. Retrograde reaction textures such as scapolite + quartz symplectites after feldspar and calcite and replacement of dolomite + diopside or tremolite+dolomite after calcite+forsterite or calcite+clinohumite are indicative of retrogression under high XCO2 conditions. Calcite preserves late Proterozoic carbon and oxygen isotopic signatures and the marble lacks evidence for extensive retrograde fluid infiltration, while during prograde metamorphism the possible infiltration of aqueous fluids did not produce significant isotopic resetting. Isotopic zonation of calcite and graphite grains was likely produced by localized CO2 fluid infiltration during retrogression. Contrary to the widespread occurrence of humite‐marbles related to retrograde aqueous fluid infiltration, the Ambasamudram humite‐marbles record a prograde‐to‐peak metamorphic humite formation and retrogression under conditions of low XH2O. 相似文献
58.
Maria Rose Petrizzo 《Cretaceous Research》2001,22(6):829
An almost complete Upper Cretaceous sedimentary sequence recently recovered on the Kerguelen Plateau (southern Indian Ocean) during ODP Leg 183 was analysed for planktonic foraminifera in order to refine and integrate the zonal schemes previously proposed for the Southern Ocean area. Detailed biostratigraphic analysis carried out on holes 1135A, 1136A and 1138A (poleward of 50°S palaeolatitude during Late Cretaceous time) has allowed recognition of low and mid–high latitude bioevents, useful for correlation across latitudes, in addition to known Austral bioevents. The low latitude biozonation can be applied to Turonian sediments, because of the occurrence of Helvetoglobotruncana helvetica, which marks the boundary between Whiteinella archaeocretacea and Helvetoglobotruncana helvetica zones. The base of the Whiteinella archeocretacea Zone falls within the uppermost Cenomanian–Turonian black shale level in Hole 1138A. The stratigraphic interval from upper Turonian to uppermost Santonian can be resolved using bioevents recognized in the mid–high latitude sections. They are, in stratigraphic order: the last occurrence of Falsotruncana maslakovae in the Coniacian, the first occurrence of Heterohelix papula at the Coniacian/Santonian boundary, the extinction of the marginotruncanids in the late Santonian, and the first occurrence of Globigerinelloides impensus in the latest (?) Santonian. The remainder of the Late Cretaceous fits rather well in the Austral zonal scheme, except that Globigerinelloides impensus exhibits a stratigraphic range in agreement with its record at the mid–high latitude sections and extends further downwards than previously recorded at southern sites. Therefore, despite the poor recovery in certain intervals and the presence of several hiatuses of local and regional importance as revealed by correlation among holes, a more detailed zonal scheme has been obtained (mainly for the less resolved Turonian–Santonian interval). Remarks on some species often overlooked in literature are also provided. 相似文献
59.
潜在震源区内部空间非均匀分布地震区划方法在攀西地区和晋中南地区的应用 总被引:2,自引:1,他引:2
本文依据潜在震源区内部地震非均匀分布模型研究了攀西地区和晋中南地区地震区划问题。研究结果表明,一般使用的均匀分布模型会低估地震危险性结果,导致高烈度分区的面积缩小。本文讨论了不同的确定非均匀分布概率的方法对地震区划结果的影响。 相似文献
60.
Researchonseismicintensityzonationbyuseoftheresponseintensityofhistoricalearth┐quakeswiththecentralpartofShanxiProvinceasanex... 相似文献