全文获取类型
收费全文 | 14830篇 |
免费 | 144篇 |
国内免费 | 130篇 |
专业分类
测绘学 | 270篇 |
大气科学 | 983篇 |
地球物理 | 2729篇 |
地质学 | 6159篇 |
海洋学 | 1434篇 |
天文学 | 2859篇 |
综合类 | 113篇 |
自然地理 | 557篇 |
出版年
2022年 | 189篇 |
2021年 | 257篇 |
2020年 | 264篇 |
2019年 | 301篇 |
2018年 | 693篇 |
2017年 | 600篇 |
2016年 | 673篇 |
2015年 | 274篇 |
2014年 | 598篇 |
2013年 | 868篇 |
2012年 | 703篇 |
2011年 | 814篇 |
2010年 | 806篇 |
2009年 | 858篇 |
2008年 | 766篇 |
2007年 | 802篇 |
2006年 | 665篇 |
2005年 | 407篇 |
2004年 | 339篇 |
2003年 | 302篇 |
2002年 | 300篇 |
2001年 | 267篇 |
2000年 | 273篇 |
1999年 | 178篇 |
1998年 | 192篇 |
1997年 | 182篇 |
1996年 | 120篇 |
1995年 | 131篇 |
1994年 | 117篇 |
1993年 | 98篇 |
1992年 | 74篇 |
1991年 | 99篇 |
1990年 | 98篇 |
1989年 | 69篇 |
1988年 | 81篇 |
1987年 | 100篇 |
1986年 | 82篇 |
1985年 | 109篇 |
1984年 | 97篇 |
1983年 | 104篇 |
1982年 | 87篇 |
1981年 | 81篇 |
1980年 | 99篇 |
1979年 | 89篇 |
1978年 | 87篇 |
1977年 | 77篇 |
1976年 | 60篇 |
1975年 | 63篇 |
1974年 | 71篇 |
1973年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
The effect of fluids on recrystallization behaviour is well known; however, the detailed microscale distribution of fluid in grain boundaries and the influence of fluid on grain boundary migration are still unresolved. In this study, in‐situ deformation experiments in transmitted light microscopy were undertaken, as this allows continuous and direct observation of the whole range of processes involved in fluid‐assisted grain boundary migration. A new see‐through deformation apparatus was developed to enable the control of fluid pressure. Bischofite containing small amounts of aqueous fluid was deformed at temperatures between 50 and 90 °C, over a range of fluid pressure from 0.5 to 1 MPa, and strain rates of 5 × 10?6 to 1 × 10?4 s?1. The rates of grain boundary migration were measured at different temperatures and strain rates. Detailed observations during and after the deformation illustrate the evolution of migrating fluid‐filled grain boundaries and show that the incorporation of fluids from inclusions as well as their pinch‐off is dependent on the grain boundary velocity, the thickness of the grain boundary and the size and shape of the inclusions. Direct evidence is presented for the contraction of the grain boundary fluids into isolated inclusions after equilibrium conditions are attained. 相似文献
105.
Ya.P. Malovitskiy E.M. Emelyanov O.V. Kazakov V.N. Moskalenko G.V. Osipov K.M. Shimkus I.S. Chumakov 《Marine Geology》1975,18(5):231-261
According to geophysical data, the Mediterranean Sea depressions are noted for a peculiar type of the earth's crust. The sedimentary rock sequence is of great thickness (8–15 km) and is of platform-type dislocation. Several structural stages are distinguished in the sedimentary complex. The youngest of them are the Messinian (evaporite) and Pliocene—Quaternary stages. The consolidated part of the earth's crust shows small thickness and is divided into large blocks. Vertical dislocations of the large crustal blocks which were conditioned by condensation—rarefaction and the upper mantle substance migration were at the base of Mediterranean sea floor transformation. 相似文献
106.
107.
O. Yu. Bogdanova A. I. Gorshkov G. V. Novikov Yu. A. Bogdanov 《Geology of Ore Deposits》2008,50(6):462-469
The mineralogy and structural features of the main types of ferromanganese deposits—nodules, micronodules, Co-bearing crusts, crustlike nodules, and low-temperature hydrothermal manganese crusts and ferruginous ochers—are considered. The correlation between their mineral composition and structure is shown. The proposed classification of mineral types is based on characteristic assemblages of Fe and Mn minerals. 相似文献
108.
The structures of sodium silicate and aluminosilicate glasses quenched from melts at high pressure (6-10 GPa) with varying degrees of polymerization (fractions of nonbridging oxygen) were explored using solid-state NMR [17O and 27Al triple-quantum magic-angle spinning (3QMAS) NMR]. The bond connectivity in melts among four and highly coordinated network polyhedra, such as [4]Al, [5,6]Al, [4]Si, and [5,6]Si, at high pressure is shown to be significantly different from that at ambient pressure. In particular, in the silicate and aluminosilicate melts, the proportion of nonbridging oxygen (NBO) generally decreases with increasing pressure, leading to the formation of new oxygen clusters that include 5- and 6-coordinated Si and Al in addition to 4-coordinated Al and Si, such as [4]Si-O-[5,6]Si, [4]Si-O-[5,6]Al and Na-O-[5,6]Si. While the fractions of [5,6]Al increase with pressure, the magnitude of this increase diminishes with increasing degrees of ambient-pressure polymerization under isobaric conditions. Incorporating the above structural information into models of melt properties reproduces the anomalous pressure-dependence of O2− diffusivity and viscosity often observed in silicate melts. 相似文献
109.
In order to better understand the interaction between aqueous uranium and pyrite (FeS2) the uptake of uranium onto the surfaces of both weathered and freshly generated pyrite surfaces was examined using batch sorption experiments. Analysis was performed using X-ray photoelectron spectroscopy (XPS). The results clearly indicate that freshly polished pyrite surfaces are efficient scavengers of uranium from solution, while weathered surfaces exhibit only limited uptake. Results also indicate partial reduction of uranium at the pyrite surfaces, with a heterogeneous distribution of U(IV) and U(VI) species. 相似文献
110.
A. B. Kotov A. A. Sorokin E. B. Sal’nikova A. P. Sorokin A. M. Larin S. D. Velikoslavinskii T. V. Belyakov I. V. Anisimova S. Z. Yakovleva 《Doklady Earth Sciences》2009,429(2):1457-1461
U-Pb geochronological results confirm the Mesozoic age (124 ± 1 Ma) of the Beket granitoid complex, previously interpreted
as being one of the markers amongst the Early Proterozoic magmatic complexes within the Amur superterrane (microcontinent)
of the Central Asian Fold Belt. This implies that the structural and metamorphic amphibolite facies overprints documented
either in the Beket granitoids or Gonzha host rocks are evidently Mesozoic rather than Early Proterozoic in age. 相似文献