全文获取类型
收费全文 | 43793篇 |
免费 | 19574篇 |
国内免费 | 44601篇 |
专业分类
测绘学 | 3813篇 |
大气科学 | 22512篇 |
地球物理 | 14593篇 |
地质学 | 40013篇 |
海洋学 | 16875篇 |
天文学 | 1304篇 |
综合类 | 5314篇 |
自然地理 | 3544篇 |
出版年
2024年 | 219篇 |
2023年 | 527篇 |
2022年 | 1024篇 |
2021年 | 1356篇 |
2020年 | 2425篇 |
2019年 | 5881篇 |
2018年 | 6160篇 |
2017年 | 5800篇 |
2016年 | 5922篇 |
2015年 | 5196篇 |
2014年 | 4852篇 |
2013年 | 5382篇 |
2012年 | 5122篇 |
2011年 | 5009篇 |
2010年 | 4851篇 |
2009年 | 4187篇 |
2008年 | 3467篇 |
2007年 | 3515篇 |
2006年 | 3085篇 |
2005年 | 2846篇 |
2004年 | 3062篇 |
2003年 | 2805篇 |
2002年 | 2616篇 |
2001年 | 2356篇 |
2000年 | 1957篇 |
1999年 | 1973篇 |
1998年 | 1968篇 |
1997年 | 1994篇 |
1996年 | 1592篇 |
1995年 | 1507篇 |
1994年 | 1404篇 |
1993年 | 1342篇 |
1992年 | 1092篇 |
1991年 | 828篇 |
1990年 | 781篇 |
1989年 | 641篇 |
1988年 | 566篇 |
1987年 | 426篇 |
1986年 | 351篇 |
1985年 | 273篇 |
1984年 | 296篇 |
1983年 | 182篇 |
1982年 | 213篇 |
1981年 | 156篇 |
1980年 | 110篇 |
1979年 | 114篇 |
1978年 | 49篇 |
1977年 | 44篇 |
1971年 | 53篇 |
1970年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
内蒙古科尔康油田沙海组储集层的岩石学特征 总被引:1,自引:0,他引:1
根据碎屑岩铸体薄片和扫描电镜观察分析资料,研究了科尔康油田沙海组储集层的岩石学特征。科尔康油田沙海组储集层的岩石类型主要为岩屑砂岩和岩屑砂砾岩。碎屑岩的岩性特征对沙海组储集层的成岩作用具有显著的影响作用。 相似文献
83.
N. V. Sobolev F. V. Kaminsky W. L. Griffin E. S. Yefimova T. T. Win C. G. Ryan A. I. Botkunov 《Lithos》1997,39(3-4):135-157
The Sputnik kimberlite pipe is a small “satellite” of the larger Mir pipe in central Yakutia (Sakha), Russia. Study of 38 large diamonds (0.7-4.9 carats) showed that nine contain inclusions of the eclogitic paragenesis, while the remainder contain inclusions of the peridotitic paragenesis, or of uncertain paragenesis. The peridotitic inclusion suite comprises olivine, enstatite, Cr-diopside, chromite, Cr-pyrope garnet (both lherzolitic and harzburgitic), ilmenite, Ni-rich sulfide and a Ti-Cr-Fe-Mg-Sr-K phase of the lindsleyite-mathiasite (LIMA) series. The eclogitic inclusion suite comprises omphacite, garnet, Ni-poor sulfide, phlogopite and rutile. Peridotitic ilmenite inclusions have high Mg, Cr and Ni contents and high Nb/Zr ratios; they may be related to metasomatic ilmenites known from peridotite xenoliths in kimberlite. Eclogitic phlogopite is intergrown with omphacite, coexists with garnet, and has an unusually high TiO2 content. Comparison with inclusions in diamonds from Mir shows general similarities, but differences in details of trace-element patterns. Large compositional variations among inclusions of one phase (olivine, garnet, chromite) within single diamonds indicate that the chemical environment of diamond crystallisation changed rapidly relative to diamond growth rates in many cases. P-T conditions of formation were calculated from multiphase inclusions and from trace element geothermobarometry of single inclusions. The geotherm at the time of diamond formation was near a 35 mW/m2 conductive model; that is indistinguishable from the Paleozoic geotherm derived by studies of xenoliths and concentrate minerals from Mir. A range of Ni temperatures between garnet inclusions in single diamonds from both Mir and Sputnik suggests that many of the diamonds grew during thermal events affecting a relatively narrow depth range of the lithosphere, within the diamond stability field. The minor differences between inclusions in Mir and Sputnik may reflect lateral heterogeneity in the upper mantle. 相似文献
84.
丰城洛市地区推,滑覆构造特征及其成因探讨 总被引:2,自引:0,他引:2
介绍了洛市地区推、滑覆构造特征、运动学标志及其形成时期、成因模式。 相似文献
85.
This paper addresses the problem of characterizing the shape of a geological surface on the basis of its principal curvatures.
The surface is assumed to be modeled as a set of adjacent triangles defined by the location of their vertices and a method
is proposed for estimating numerically the principal curvatures at the vertices of the triangles using a local C2 interpolant. Also shown is how principal curvatures can be useful for studying the deformation of a geological surface (with
application to 3D balanced unfolding), and analyzing the folding or faulting of the interface between two adjacent layers. 相似文献
86.
K. S. Voudouris N. J. Lambrakis G. Papatheothorou P. Daskalaki 《Mathematical Geology》1997,29(1):43-59
R- andQ-mode factor analysis is applied to 51 groundwater samples collected from wells drilled in the Plio-Pleistocene aquifers of
NW Achaia, Greece. The purpose ofR- andQ-mode factor analysis application is to identify (i) the regional groundwater flow pattern, and (ii) the deterioration of
groundwater quality. Sixteen hydrogeological parameters are used in order to examine their importance and to provide significant
insight into their correlations. In theR-mode factor analysis, a six-factor model is suggested which can explain more than 77.5% of the total variance. The contribution
of each factor at every site (factor scores) also is computed. Maps are constructed showing the geographical distribution
of the factor scores. From these maps, the high salinity areas are delineated (seawater intrusion, possible appearance of
halite layers) and the areas with elevated contribution of karastic-water are defined. Using theQ-mode correspondence analysis the meaning of the electrical conductivity as the most important variable in groundwater quality
characterization is demonstrated. 相似文献
87.
88.
In this paper,the Gutenberg-Richter model is used to generate seismic events.The events that satisfy the random distribution are also generated.With those events,the natural probability distribution of Load and Unload Response Ratio(LURR),which measures quantitatively the degree of instability of a nonlinear system,is discussed.The study is based on stress energy release,which is chosen as the response of nonlinear system F3.The comparative results from the observation catalogue and generating data are also studied.It is revealed that the natural probability of LURR is mostly stable when the sample number is sufficient.The lower the natural probability of LURR,the more the precursory is information it may contain.The influence of Y3 resulting from the sample number and the magnitude range of events is also discussed. 相似文献
89.
Dong Ruishu Xiang Hongfa Guo Shunmin Ran Hongliu and Fu ChanghongInstitute of Geology SSB Beijing China Institute of Geophysics SSB Beijing China 《中国地震研究》1997,(4)
There have been 12 possible locations of the earthquakes occurring in the South Yellow Sea since 1505.In this paper,the location of the earthquake that occurred in 1505 has been determined by the collection of more historical data of the influenced field,referring the isoseismal data of earthquakes with the epicentral intensityⅨ and combining geophysical field data with tectonic condition,due to its great influence on seismic safety assessment of some significant engineering. 相似文献
90.