全文获取类型
收费全文 | 77209篇 |
免费 | 1500篇 |
国内免费 | 761篇 |
专业分类
测绘学 | 1883篇 |
大气科学 | 5350篇 |
地球物理 | 15255篇 |
地质学 | 27864篇 |
海洋学 | 7045篇 |
天文学 | 17335篇 |
综合类 | 267篇 |
自然地理 | 4471篇 |
出版年
2022年 | 968篇 |
2021年 | 1473篇 |
2020年 | 1485篇 |
2019年 | 1554篇 |
2018年 | 2199篇 |
2017年 | 1942篇 |
2016年 | 2299篇 |
2015年 | 1401篇 |
2014年 | 2207篇 |
2013年 | 3871篇 |
2012年 | 2337篇 |
2011年 | 3273篇 |
2010年 | 2732篇 |
2009年 | 3690篇 |
2008年 | 3319篇 |
2007年 | 3117篇 |
2006年 | 2960篇 |
2005年 | 2438篇 |
2004年 | 2462篇 |
2003年 | 2338篇 |
2002年 | 2186篇 |
2001年 | 1995篇 |
2000年 | 1801篇 |
1999年 | 1422篇 |
1998年 | 1553篇 |
1997年 | 1497篇 |
1996年 | 1063篇 |
1995年 | 1161篇 |
1994年 | 1001篇 |
1993年 | 892篇 |
1992年 | 885篇 |
1991年 | 797篇 |
1990年 | 872篇 |
1989年 | 754篇 |
1988年 | 685篇 |
1987年 | 836篇 |
1986年 | 745篇 |
1985年 | 883篇 |
1984年 | 949篇 |
1983年 | 909篇 |
1982年 | 833篇 |
1981年 | 733篇 |
1980年 | 675篇 |
1979年 | 616篇 |
1978年 | 628篇 |
1977年 | 566篇 |
1976年 | 542篇 |
1975年 | 519篇 |
1974年 | 567篇 |
1973年 | 514篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
31.
Smirnov S. E. Mikhailov Yu. M. Mikhailova G. A. Kapustina O. V. 《Geomagnetism and Aeronomy》2019,59(6):696-703
Geomagnetism and Aeronomy - Winter thunderstorms in Kamchatka are a rare meteorological phenomenon. Temporal variations of the quasi-static electric field and meteorological values at the Paratunka... 相似文献
32.
Geomagnetism and Aeronomy - Features of the development of activity cycles in the solar-type stars and fast-rotating cool dwarfs have been considered for 65 stars observed in some decades. Cycles... 相似文献
33.
Natural Hazards - In this study, we present a novel methodology that may be used to analyze tsunami risk along coastal regions. The application of the proposed methodology is demonstrated for the... 相似文献
34.
Geotectonics - The dunite–wehrlite–clinopyroxenite–gabbro massif in Eastern Chukotka, a key object for geodynamic reconstructions of the Vel’may terrane, which represents... 相似文献
35.
Khamitov I. M. Bikmaev I. F. Burenin R. A. Glushkov M. V. Melnikov S. S. Lyapin A. R. 《Astronomy Letters》2020,46(1):1-11
Astronomy Letters - An example of simultaneous spectroscopic redshift measurements for a large number of galaxies in a cluster by multiobject spectroscopy with the medium- and low-resolution TFOSC... 相似文献
36.
The thermal evolution of sedimentary basins is usually constrained by maturity data, which is interpreted from Rock-Eval pyrolysis and vitrinite reflectance analytical results on field or boreholes samples. However, some thermal evolution models may be inaccurate due to the use of elevated maturities measured in samples collected within an undetected metamorphic contact aureole surrounding a magmatic intrusion. In this context, we investigate the maturity and magnetic mineralogy of 16 claystone samples from Disko-Svartenhuk Basin, part of the SE Baffin Bay volcanic margin. Samples were collected within thermal contact metamorphic aureoles near magma intrusions, as well as equivalent reference samples not affected by intrusions. Rock-Eval pyrolysis (Tmax), and vitrinite reflectance (Ro) analysis were performed to assess the thermal maturity, which lies in the oil window when 435°C ≤ Tmax ≤ 470°C and 0.6%–0.7% ≤ Ro ≤ 1.3%. In addition, we performed low- (<300K) and high-temperature (>300K) investigations of isothermal remanent magnetization to assess the magnetic mineralogy of the selected samples. The maturity results (0.37% ≤ Ro ≤ 2%, 22°C ≤ Tmax ≤ 604°C) show a predominance of immature to early mature Type III organic matter, but do not reliably identify the contact aureole when compared to the reference samples. The magnetic assemblage of the immature samples consists of iron sulphide (greigite), goethite and oxidized or non-stoichiometric magnetite. The magnetic assemblage of the early mature to mature samples consists of stoichiometric magnetite and fine-grained pyrrhotite (<1 μm). These results document the disappearance of the iron sulphide (greigite) and increase in content of magnetite during normal burial. On the other hand, magnetite is interpreted to be the dominant magnetic mineral inside the contact aureole surrounding dyke/sill intrusions where palaeotemperatures indicate mature to over-mature state. Interestingly, the iron sulphide (greigite) is still detected in the contact aureole where palaeotemperatures exceeded 130°C. Therefore, the magnetic mineralogy is a sensitive method that can characterize normal burial history, as well as identify hidden metamorphic contact aureoles where the iron sulphide greigite is present at temperatures beyond its stability field. 相似文献
37.
The Lyra-B space experiment (SE) is a high-precision multicolor multiple all-sky photometric survey of stars and star-like objects. The experiment will be conducted from the Russian segment of the International Space Station (ISS). For this purpose, a 0.5-m telescope will be installed onboard (or, more precisely, outboard) the ISS, which will observe stars in a scanning mode. The Lyra-B SE was included in the program of scientific experiments at the ISS fairly long ago. At the beginning of the SE design it was thought that the ISS would exist “eternally” and the time needed for the full-fledged implementation of the experiment would be allocated. Today, however, the situation has changed. In 2025 the ISS will possibly cease to exist either as the space station as a whole or in the form in which it exists now. Hence there arises the problem to perform the entire volume of observations in a maximally short time, i.e., to find an optimal sky scanning strategy that would ensure a maximum duration of observations. In addition, we consider two related questions: with what density will the observations be distributed over the sky and how many times will a point in the sky fallen within the field of view of the Lyra-B telescope be observed in successive orbital revolutions? This question is important for investigating variable stars, determining the orbits and axial rotation periods of asteroids, and ensuring a specified photometric accuracy over the entire sky. 相似文献
38.
Alameer Zakaria Elaziz Mohamed Abd Ewees Ahmed A. Ye Haiwang Jianhua Zhang 《Natural Resources Research》2019,28(4):1385-1401
Natural Resources Research - An accurate forecasting model for the price volatility of minerals plays a vital role in future investments and decisions for mining projects and related companies. In... 相似文献
39.
Glacial tills are highly compressible soils composed of loosely cemented sandy silt particles. Their role, for instance, as initial filler materials in geo-technical projects along temperate glacier regions warrant a systematic evaluation of their compressive characteristics. As such, we carry out a series of onedimensional compression tests on re-compacted glacial till samples obtained from Tianmo Gully, Tibet, with the aims of evaluating their compressive behavior under controlled initial stress conditions. The yield stress was determined from the void ratio versus consolidation pressure(e-log) planes. Its compression and swelling behaviors were observed during the primary and secondary compressions of the consolidation tests. From the compression curves, a correlation can be found between the consolidation stress and the void index. In addition, we find that the compression curves of glacial tills collapse into a single curve when normalized by the compression index. The experimental results in this study provide a basic understanding of the compression characteristics of the glacial tills in Tibet, China. 相似文献
40.
Geomagnetism and Aeronomy - The solar activity at different latitudes is analyzed based on daily observations at Kodaikanal, Mount Wilson, Sacramento Peak, and Meudon observatories in the CaIIK... 相似文献