全文获取类型
收费全文 | 16610篇 |
免费 | 271篇 |
国内免费 | 115篇 |
专业分类
测绘学 | 337篇 |
大气科学 | 1134篇 |
地球物理 | 3426篇 |
地质学 | 6224篇 |
海洋学 | 1623篇 |
天文学 | 3246篇 |
综合类 | 67篇 |
自然地理 | 939篇 |
出版年
2022年 | 168篇 |
2021年 | 266篇 |
2020年 | 251篇 |
2019年 | 297篇 |
2018年 | 615篇 |
2017年 | 511篇 |
2016年 | 601篇 |
2015年 | 318篇 |
2014年 | 543篇 |
2013年 | 834篇 |
2012年 | 611篇 |
2011年 | 799篇 |
2010年 | 725篇 |
2009年 | 893篇 |
2008年 | 781篇 |
2007年 | 766篇 |
2006年 | 694篇 |
2005年 | 502篇 |
2004年 | 472篇 |
2003年 | 425篇 |
2002年 | 425篇 |
2001年 | 321篇 |
2000年 | 350篇 |
1999年 | 249篇 |
1998年 | 267篇 |
1997年 | 233篇 |
1996年 | 179篇 |
1995年 | 216篇 |
1994年 | 193篇 |
1993年 | 156篇 |
1992年 | 136篇 |
1991年 | 149篇 |
1990年 | 162篇 |
1989年 | 128篇 |
1988年 | 137篇 |
1987年 | 159篇 |
1986年 | 136篇 |
1985年 | 172篇 |
1984年 | 184篇 |
1983年 | 172篇 |
1982年 | 152篇 |
1981年 | 138篇 |
1980年 | 165篇 |
1979年 | 143篇 |
1978年 | 142篇 |
1977年 | 116篇 |
1976年 | 108篇 |
1975年 | 114篇 |
1974年 | 110篇 |
1973年 | 114篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
James L. Etienne Neil F. Glasser Michael J. Hambrey 《Geografiska Annaler: Series A, Physical Geography》2003,85(2):149-164
Mapping and laboratory analysis of the sediment—landform associations in the proglacial area of polythermal Storglaciären, Tarfala, northern Sweden, reveal six distinct lithofacies. Sandy gravel, silty gravel, massive sand and silty sand are interpreted as glaciofluvial in origin. A variable, pervasively deformed to massive clast‐rich sandy diamicton is interpreted as the product of an actively deforming subglacial till layer. Massive block gravels, comprising two distinctive moraine ridges, reflect supraglacial sedimentation and ice‐marginal and subglacial reworking of heterogeneous proglacial sediments during the Little Ice Age and an earlier more extensive advance. Visual estimation of the relative abundance of these lithofacies suggests that the sandy gravel lithofacies is of the most volumetric importance, followed by the diamicton and block gravels. Sedimentological analysis suggests that the role of a deforming basal till layer has been the dominant factor controlling glacier flow throughout the Little Ice Age, punctuated by shorter (warmer and wetter climatic) periods where high water pressures may have played a more important role. These results contribute to the database that facilitates discrimination of past glacier thermal regimes and dynamics in areas that are no longer glacierized, as well as older glaciations in the geological record. 相似文献
92.
93.
Philipp Tesch Robert S. Reece James R. Markello Juan Carlos Laya Michael C. Pope 《Basin Research》2020,32(2):388-401
We developed a seismic geomorphology-based procedure to enhance traditional trajectory analysis with the ability to visualize and quantify lateral variability along carbonate prograding-margin types (ramps and rimmed shelves) in 3D and 4D. This quantitative approach analysed the shelf break geometric evolution of the Oligo-Miocene carbonate clinoform system in the Browse Basin and delineated the feedback between antecedent topography and carbonate system response as controlling factor on shelf break rugosity. Our geometrical analysis identified a systematic shift in the large-scale average shelf break strike direction over a transect of 10 km from 62° to 55° in the Oligo-Miocene interval of the Browse Basin, which is likely controlled by far-field allogenic forcing from the Timor Trough collision zone. Plotting of 3D shelf break trajectories represents a convenient way to visualize the lateral variability in shelf break evolution. Shelf break trajectories that indicate contemporaneous along-strike progradation and retrogradation correlate with phases of autogenic slope system re-organization and may be a proxy for morphological stability of the shelf break. Shelf break rugosity and shelf break trajectory rugosity are not inherited parameters and antecedent topography does not dictate long-term differential movement of the shelf margin through successive depositional sequences. The autogenic carbonate system response to antecedent topography smooths high-rugosity areas by filling accommodation and maintains a relatively constant shelf break rugosity of ~150 m. Color-coding of the vertical component in the shelf break trajectory captures the creation and filling of accommodation, and highlights areas of the transect that are likely to yield inconsistent 2D sequence stratigraphic interpretations. 相似文献
94.
95.
Marc W. Pound Jave O. Kane Bruce A. Remington Dmitri D. Ryutov Akira Mizuta Hideaki Takabe 《Astrophysics and Space Science》2005,298(1-2):177-181
Over the past few years, our group has been developing hydrodynamic models to simulate formation of the Eagle Nebula pillars.
The true test of any model is, of course, how well it can reproduce the observations. Here, we discuss how we go about testing
our models against observations. We describe the process by which we “observe” the model data to create synthetic maps. We
show an example of this technique using one of our model runs and compare the resultant synthetic map to the real one. 相似文献
96.
Natural Resources Research - Sand failure and production occurs when the formation stress exceeds the strength of the formation, which is derived majorly from the natural material that cements the... 相似文献
97.
98.
V. V. Aristov I. I. Babarina A. V. Grigor’eva V. Yu. Alekseev V. Yu. Prokof’ev A. A. Uzyunkoyan O. V. Zabolotskaya S. G. Titov 《Geology of Ore Deposits》2017,59(1):68-101
Gold deposits and occurrences small in reserves and high in Au grade conventionally determine the line of prospecting in terrigenous sequences of the Verkhoyansk–Kolyma region. In this paper, the geological structure of such gold objects is considered with the example of the deposits and prospects making up the Zhdaninsky ore–placer cluster in the Republic of Sakha (Yakuia). From lithological, structural, and mineralogical–geochemical data, the formation conditions of ore-bearing complexes are specified, the geological evolution history of the northern Ol’chan Zone of the Kular–Nera Belt is reconstructed, and the zonal distribution of mineralization within the ore–placer cluster is revealed. The structural–compositional complexes were formed in the following succession: (1) sedimentation at the shelf of the passive margin accompanied by synsedimentation deformations; (2) metagenesis of sediments and the development of bedding-plane intraformational detachments of collision stage D1 under conditions of tangential compression and accompanied by the formation of carbon dioxide–aqueous metamorphic fluid at a temperature of 300°C and under a pressure of 1.4 kbar; (3) folding and faulting of orogenic stage D2 with the formation of synkinematic magmatic bodies, metasomatic alteration, and Au-bearig mineral assemblages. Small Au-bearing objects with veined mineralization and high Au grade are localized in structures of stage D2 transverse to bedding-plane schistosity S1. They form at the collision stage above intraformational detachment surfaces and are controlled by shear structures of the orogenic stage with misalignment of these deformations. The ore zoning is determined by the distribution of Co and Ni minerals and by variations in the anionic composition of ore (S, As, Sb). 相似文献
99.
James M. Stroh 《Contributions to Mineralogy and Petrology》1976,54(3):173-188
The addition of Fe and Cr to the simple system MgO-SiO2-Al2O3 markedly affects the activities of phases involved in the equilibrium
\textMg\text2 \textSiO\text4 \text + MgAl\text2 \textSiO\text6 \text = MgAl\text2 \textO\text4 \text + Mg\text2 \textSi\text2 \textO\text6 \textOlivine + Opx\textsolid solution \text = Spinel + Opx\textsolid solution \begin{gathered} {\text{Mg}}_{\text{2}} {\text{SiO}}_{\text{4}} {\text{ + MgAl}}_{\text{2}} {\text{SiO}}_{\text{6}} {\text{ = MgAl}}_{\text{2}} {\text{O}}_{\text{4}} {\text{ + Mg}}_{\text{2}} {\text{Si}}_{\text{2}} {\text{O}}_{\text{6}} \hfill \\ {\text{Olivine + Opx}}_{{\text{solid solution}}} {\text{ = Spinel + Opx}}_{{\text{solid solution}}} \hfill \\ \end{gathered} 相似文献
100.
The galactic distribution and physical nature of X-ray transient sources is investigated. Two types of transients are considered. The observational data on 41 X-ray transient sources are given, and the average parameters of hard and soft X-ray transients are estimated. 相似文献
|