全文获取类型
收费全文 | 3920篇 |
免费 | 38篇 |
国内免费 | 41篇 |
专业分类
测绘学 | 43篇 |
大气科学 | 320篇 |
地球物理 | 669篇 |
地质学 | 1971篇 |
海洋学 | 333篇 |
天文学 | 473篇 |
综合类 | 64篇 |
自然地理 | 126篇 |
出版年
2023年 | 4篇 |
2022年 | 49篇 |
2021年 | 68篇 |
2020年 | 85篇 |
2019年 | 100篇 |
2018年 | 223篇 |
2017年 | 218篇 |
2016年 | 253篇 |
2015年 | 110篇 |
2014年 | 243篇 |
2013年 | 318篇 |
2012年 | 318篇 |
2011年 | 315篇 |
2010年 | 336篇 |
2009年 | 269篇 |
2008年 | 254篇 |
2007年 | 277篇 |
2006年 | 216篇 |
2005年 | 102篇 |
2004年 | 38篇 |
2003年 | 28篇 |
2002年 | 30篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 18篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1958年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有3999条查询结果,搜索用时 15 毫秒
991.
Geomagnetism and Aeronomy - The behavior of the average annual luminosity of K–M dwarfs OU Gem, EQ Vir, V1005 Ori and AU Mic was studied at time intervals of several decades. The main sources... 相似文献
992.
Geomagnetism and Aeronomy - A statistical study of long-duration (long-duration event, LDE) flares in the soft X-ray (SXR) range for solar cycles 23 and 24 is carried out. Graphs of the dependence... 相似文献
993.
Geomagnetism and Aeronomy - The article considers 30 solar flare events during which the spectra of solar cosmic-ray (SCR) protons with energies above ~80 MeV were recorded in the course of the... 相似文献
994.
Pil’gaev S. V. Fedorenko Yu. V. Kleimenova N. G. Manninen J. Nikitenko A. S. Larchenko A. V. Filatov M. V. Lebed’ O. M. Frolov I. E. Kozelov B. V. 《Geomagnetism and Aeronomy》2020,60(2):212-215
Geomagnetism and Aeronomy - The first results are presented for observations of the VLF emissions (1–15 kHz) conducted at polar latitudes during the expedition Transarctica 2019, which was... 相似文献
995.
Geomagnetism and Aeronomy - In this article, the dynamics of the annual variation in the mean monthly values of temperature and precipitation is studied via the expansion of series into natural... 相似文献
996.
P. N. Makkaveev V. V. Gordeev P. O. Zav’yalov A. A. Polukhin P. V. Khlebopashev A. I. Kochenkova 《Water Resources》2018,45(2):188-198
The decrease in Aral Sea area, which started in the 1960s, caused considerable changes in the hydrological, chemical, and biological structure of sea water. Regular observations of Aral water chemistry ceased in the early 1990s. There were no observations of the concentrations of biogenic element compounds in water (the so-called “first-day analyses”). During expeditions of the Institute of Oceanology, RAS, in September 2012 and October 2013, integrated hydrochemical observations were carried out, including measuring the concentrations of biogenic element compounds, dissolved oxygen, hydrogen sulfide, and carbonate equilibrium components. An objective of this study was to develop methods of hydrochemical studies under high water salinity (mineralization). In addition to the standard hydrochemical complex, water samples were taken to determine total water mineralization and the concentration of dissolved and suspended metal forms. The results of these studies are given. 相似文献
997.
K. K. Edel’shtein V. V. Puklakov Yu. S. Datsenko O. N. Erina D. I. Sokolov 《Water Resources》2018,45(3):399-408
The annual regimes of estimated rates of oxygen and carbon dioxide exchange between water surface and the atmosphere was compared for two water bodies with different sizes and hydroecological conditions: the deep oligotrophic Lake Baikal and the small mesotrophic–eutrophic Mozhaisk Reservoir with water exchange rate 150 times greater than that of Baikal. The obtained, very large, differences between the rates of gas evasions and invasions in the lake and the reservoir allow the rates of these processes to be used as integral characteristics for the parameterization of the self-purification capacity of freshwater bodies from organic pollutants. 相似文献
998.
Slowness domain offset and traveltime approximations in layered vertical transversely isotropic media
下载免费PDF全文
![点击此处可从《Geophysical Prospecting》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Considering horizontally layered transversely isotropic media with vertical symmetry axis and all types of pure‐mode and converted waves we present a new wide‐angle series approximation for the kinematical characteristics of reflected waves: horizontal offset, intercept time, and total reflection traveltime as functions of horizontal slowness. The method is based on combining (gluing) both zero‐offset and (large) finite‐offset series coefficients. The horizontal slowness is bounded by the critical value, characterised by nearly horizontal propagation within the layer with the highest horizontal velocity. The suggested approximation uses five parameters to approximate the offset, six parameters to approximate the intercept time or the traveltime, and seven parameters to approximate any two or all three kinematical characteristics. Overall, the method is very accurate for pure‐mode compressional waves and shear waves polarised in the horizontal plane and for converted waves. The application of the method to pure‐mode shear waves polarised in the vertical plane is limited due to cusps and triplications. To demonstrate the high accuracy of the method, we consider a synthetic, multi‐layer model, and we plot the normalised errors with respect to numerical ray tracing. 相似文献
999.
J. Yu. Vasil’chuk N. A. Budantseva Ju. N. Chizhova D. L. Golovanov A. N. Tkachenko Yu. K. Vasil’chuk 《Water Resources》2018,45(5):776-784
The results of studies of variations of δ18O values in river water in Crimea Peninsula in January–February 2015–2017 are given. The variation range of δ18О in river water over the three years of studies never exceeded 3‰. A tendency toward an increase in δ18О in the water of the Salgir, Kacha, Al’ma, Bel’bek, Biyuk-Karasu from their sources to mouths was identified and explained by a decrease in evaporation in the mouth areas of the rivers relative to their sources and upper reaches, and the inflow of isotopically light precipitation (rain and snow) into the rivers in their upper reaches. The values of δ18О in waters of the rivers with regulated stream were found to increase under the effect of the Simferopol Reservoir on the Salgir River and the Izobil’nenskoe Reservoir on the Ulu-Zen’ River. The values of δ18О in the upper reaches of the large rivers of Kacha and Bel’bek (the northwestern slope of the Crimean Mountains) vary from ?8.7 to ?9.7‰, except for the rivers of Al’ma (?7.7‰) and Kokozka (?10.2‰) because of the different shares of groundwater in the recharge of these rivers. 相似文献
1000.
The space and time dynamics of organic matter concentration in groundwater in the Tungusskoe deposit during the historical 2013 flood in the Amur River is discussed. For comparison analysis, several methods for determining the quantitative characteristics of organic matter (spectrophotometry, gas-chromatographic mass spectrometry, and high-performance liquid chromatography) were applied to different layers of an aquifer at different distances from the shore line. The genesis of many organic substances is due to the inflow of river filtrate and surface water from the inundated floodplain. In the post-flood 2014, groundwater showed a decrease in the total amount of organic components and the presence of low-molecular hydrocarbons, diphenylamine, cosanes, phenanthrene, naphthalene, and derivatives of stearic and palmitic acids. Toxic methyl benzene was identified in most wells. 相似文献