全文获取类型
收费全文 | 474篇 |
免费 | 16篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 46篇 |
地球物理 | 123篇 |
地质学 | 164篇 |
海洋学 | 79篇 |
天文学 | 66篇 |
综合类 | 4篇 |
自然地理 | 19篇 |
出版年
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 13篇 |
2018年 | 24篇 |
2017年 | 17篇 |
2016年 | 29篇 |
2015年 | 12篇 |
2014年 | 22篇 |
2013年 | 24篇 |
2012年 | 25篇 |
2011年 | 22篇 |
2010年 | 28篇 |
2009年 | 26篇 |
2008年 | 27篇 |
2007年 | 28篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 2篇 |
1964年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有507条查询结果,搜索用时 46 毫秒
501.
Igor A. Beresnev 《Journal of Seismology》2017,21(5):1277-1284
Small-scale slip heterogeneity or variations in rupture velocity on the fault plane are often invoked to explain the high-frequency radiation from earthquakes. This view has no theoretical basis, which follows, for example, from the representation integral of elasticity, an exact solution for the radiated wave field. The Fourier transform, applied to the integral, shows that the seismic spectrum is fully controlled by that of the source time function, while the distribution of final slip and rupture acceleration/deceleration only contribute to directivity. This inference is corroborated by the precise numerical computation of the full radiated field from the representation integral. We compare calculated radiation from four finite-fault models: (1) uniform slip function with low slip velocity, (2) slip function spatially modulated by a sinusoidal function, (3) slip function spatially modulated by a sinusoidal function with random roughness added, and (4) uniform slip function with high slip velocity. The addition of “asperities,” both regular and irregular, does not cause any systematic increase in the spectral level of high-frequency radiation, except for the creation of maxima due to constructive interference. On the other hand, an increase in the maximum rate of slip on the fault leads to highly amplified high frequencies, in accordance with the prediction on the basis of a simple point-source treatment of the fault. Hence, computations show that the temporal rate of slip, not the spatial heterogeneity on faults, is the predominant factor forming the high-frequency radiation and thus controlling the velocity and acceleration of the resulting ground motions. 相似文献
502.
Igor Leščešen Urošev Marko Dolinaj Dragan Pantelić Milana Telbisz Tamás Varga György Savić Stevan Milošević Dragan 《Water Resources》2019,46(6):853-860
Water Resources - Floods are one of the most common natural hazards and as such, they are causing a great loss of human life as well as great economic damages. Flood frequency analysis (FFA) is... 相似文献
503.
Marja Liisa Räisänen Galina Kashulina Igor Bogatyrev 《Journal of Geochemical Exploration》1997,59(3):175-195
The mobility and retention of heavy metals, arsenic and sulphur in podzols from eight areas located north of the Arctic Circle in Finland, Norway and Russia were determined by analyzing the < 2.0 mm fraction, using an ammonium acetate (pH 4.5) extraction in addition to a concentrated nitric acid digestion for the humus samples, and a hot aqua regia digestion for the mineral soil samples. Total C, H and N concentrations were determined in humus and mineral soil samples with a CHN analyser.Ni, Cu, Co and As were strongly enriched in the humus layer in the contaminated sites (Monchegorsk, Kurka, Zapoljarnij) when compared to their concentrations in the parent tills and in podzols from the background sites. In most study sites the illuvial layer showed a low capacity to retain the metals and As, the exception included a strongly eroded profile at Monchegorsk, where Ni was tightly fixed in the illuvial layer while Cu was mobile. In contrast to metals, airborne S was not accumulated in the humus layer, but was accumulated in the illuvial layer, more markedly at eroded sites than in places where the humus was covered as at Monchegorsk. 相似文献
504.
Reliable information on the distribution of magnetic fields across the whole surface of the Sun is urgently needed to predict conditions in the solar corona, in the interplanetary medium, and in the near-Earth space (space weather). Several space- and ground-based solar instruments currently provide full-disk magnetograms. However, these measurements sometimes differ very significantly, which makes a cross-calibration of different datasets and searching for the reasons for such differences a very crucial task. Here, we analyze the Huairou Solar Observing Station (HSOS) Solar Magnetism and Activity Telescope (SMAT) full-disk line-of-sight magnetograms in comparison with magnetograms taken at the Solar Dynamic Observatory/Helioseismic and Magnetic Imager (SDO/HMI) and Solar Telescope for Operative Predictions (STOP) instruments. We show systematic differences between original SMAT magnetograms and those of other telescopes. The differences are caused by some SMAT instrumental problems, which we investigate. We suggest methods for compensating for these effects that have improved the quality of SMAT magnetograms. These methods will enable us to use SMAT measurements to solve many solar physics problems that are related to studying global solar magnetism and space weather. 相似文献
505.
Olga L.Ryabukhina Igor I.Zinchenko Manash R.Samal Petr M.Zemlyanukha Dmitry A.Ladeyschikov ANDrej M.Sobolev Christian Henkel Devendra K.Ojha 《天文和天体物理学研究(英文版)》2018,(8)
We present results of a high resolution study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex in several molecular species tracing different physical conditions. These include three isotopologues of carbon monoxide(CO), ammonia(NH3) and carbon monosulfide(CS). The aim of this work is to study the general structure and kinematics of the filamentary cloud, and its fragmentation and physical parameters. The gas temperature is derived from the NH3(J, K) =(1,1),(2, 2) and ~(12)CO(2-1) lines, and the ~(13)CO(1-0), ~(13)CO(2-1) emission is used to investigate the overall gas distribution and kinematics. Several dense clumps are identified from the CS(2-1)data. Values of the gas temperature lie in the range 10-35 K, and column density N(H2) reaches the value 5.1 x 10~(22) cm~(-2). The width of the filament is of order 1 pc. The masses of the dense clumps range from ~ 30 M_☉ to ~ 160 M_☉. They appear to be gravitationally unstable. The molecular emission shows a gas dynamical coherence along the filament. The velocity pattern may indicate longitudinal collapse. 相似文献
506.
507.
A sulfur budget for the Black Sea anoxic zone 总被引:1,自引:0,他引:1
Lev N. Neretin Igor I. Volkov Michael E. Bttcher Vladimir A. Grinenko 《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(12)
A budget for the sulfur cycle in the Black Sea is proposed which incorporates specific biogeochemical process rates. The average sulfide production in the water column is estimated to be 30–50 Tg yr−1, occurring essentially in the layer between 500 and 2000 m. About 3.2–5.2 Tg sulfide yr−1 form during sulfate reduction in surface sediments of the anoxic zone. Total sulfur burial in anoxic sediments of 1 Tg yr−1 consists of 10–70% (ca. 40–50% is the average) water column formed (syngenetic) component, the rest being diagenetic pyrite. As a maximum, between 3 and 5 Tg yr−1 contribute sulfide to the bottom water or diffuse downward in the sediment. About 20–50 Tg yr−1 sulfide is oxidized mostly at the chemocline and about 10–20% of this amount (4.4–9.2 Tg yr−1) below the chemocline by the oxygen of the Lower Bosphorus Current. A model simulating the vertical distribution of sulfide in the Black Sea water column shows net consumption in the upper layers down to ca. 500 m, essentially due to oxidation at the chemocline, and net production down to the bottom. On the basis of the calculated budget anoxic conditions in the Black Sea are sustained by the balance between sulfide production in the anoxic water column and oxidation at the chemocline. On average the residence time of sulfide in the anoxic zone is about 90–150 yr, comparable to the water exchange time between oxic and anoxic zones. Hydrophysical control on the sulfur cycle appears to be the main factor regulating the extent of anoxic conditions in the Black Sea water column, rather than rates of biogeochemical processes. 相似文献