全文获取类型
收费全文 | 37154篇 |
免费 | 254篇 |
国内免费 | 218篇 |
专业分类
测绘学 | 721篇 |
大气科学 | 1705篇 |
地球物理 | 7050篇 |
地质学 | 14630篇 |
海洋学 | 3529篇 |
天文学 | 8795篇 |
综合类 | 100篇 |
自然地理 | 1096篇 |
出版年
2022年 | 488篇 |
2021年 | 708篇 |
2020年 | 754篇 |
2019年 | 826篇 |
2018年 | 1696篇 |
2017年 | 1544篇 |
2016年 | 1638篇 |
2015年 | 615篇 |
2014年 | 1414篇 |
2013年 | 2035篇 |
2012年 | 1619篇 |
2011年 | 1899篇 |
2010年 | 1790篇 |
2009年 | 1986篇 |
2008年 | 1765篇 |
2007年 | 1978篇 |
2006年 | 1735篇 |
2005年 | 898篇 |
2004年 | 815篇 |
2003年 | 808篇 |
2002年 | 741篇 |
2001年 | 764篇 |
2000年 | 630篇 |
1999年 | 417篇 |
1998年 | 437篇 |
1997年 | 474篇 |
1996年 | 337篇 |
1995年 | 358篇 |
1994年 | 335篇 |
1993年 | 281篇 |
1992年 | 284篇 |
1991年 | 290篇 |
1990年 | 337篇 |
1989年 | 272篇 |
1988年 | 258篇 |
1987年 | 260篇 |
1986年 | 191篇 |
1985年 | 301篇 |
1984年 | 302篇 |
1983年 | 295篇 |
1982年 | 274篇 |
1981年 | 248篇 |
1980年 | 265篇 |
1979年 | 203篇 |
1978年 | 242篇 |
1977年 | 204篇 |
1976年 | 177篇 |
1975年 | 184篇 |
1974年 | 171篇 |
1973年 | 206篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
I.?A.?Berezin Yu.?M.?Timofeyev Ya.?A.?VirolainenEmail author I.?S.?Frantsuzova K.?A.?Volkova A.?V.?Poberovsky B.?N.?Holben A.?Smirnov I.?Slutsker 《Izvestiya Atmospheric and Oceanic Physics》2017,53(1):58-64
Water vapor plays a key role in weather and climate forming, which leads to the need for continuous monitoring of its content in different parts of the Earth. Intercomparison and validation of different methods for integrated water vapor (IWV) measurements are essential for determining the real accuracies of these methods. CIMEL photometers measure IWV at hundreds of ground-based stations of the AERONET network. We analyze simultaneous IWV measurements performed by a CIMEL photometer, an RPG-HATPRO MW radiometer, and a FTIR Bruker 125-HR spectrometer at the Peterhof station of St. Petersburg State University. We show that the CIMEL photometer calibrated by the manufacturer significantly underestimates the IWV obtained by other devices. We may conclude from this intercomparison that it is necessary to perform an additional calibration of the CIMEL photometer, as well as a possible correction of the interpretation technique for CIMEL measurements at the Peterhof site. 相似文献
262.
L. V. Sahakyan G. G. Babayan O. A. Belyaeva K. V. Sarkisyan G. O. Tepanosyan A. K. Saghatelyan 《Water Resources》2018,45(3):388-398
The paper gives the results of hydrochemical studies of the Tartar R.—the largest river in Nagornyi Karabakh Republic (NKR). Water quality was assessed with respect to the ecological standards of the Republic of Armenia in terms of major physicochemical characteristics and the concentrations of seven heavy metals. Water quality in the upper reaches of the Tartar R. was referred to the fifth class (poor quality), which is due to the effect of the dumps of the Sotck Gold Deposit and the pollution by agricultural, livestock, and municipal wastewaters. In the lower reaches of the Tartar R., the processes of dilution and self-purification neutralize the adverse effect of pollution sources on water quality, resulting in the improvement of water quality to the class not lower than medium, which is enough for the normal functioning of aquatic ecosystems, fishery, and irrigation. Thus, the Sarang Reservoir, which regulates the Tartar R. runoff, receives good-quality water. 相似文献
263.
J. A. Van De Konijnenberg V. Naulin J. Juul Rasmussen B. Stenum G. J. F. Van Heijst 《地球物理与天体物理流体动力学》2013,107(1-2):85-114
Abstract spin-up and spin-down in a circular tank with a uniformly sloping bottom are studied experimentally and numerically for small values of the relative change in the angular velocity of the tank. Generally, the initial single-cell flow evolves into a number of smaller vortices. The evolution is compared with an analytical model based on an expansion of the flow field in linear Rossby waves (Pedlosky and Greenspan, 1967). Although it is possible to tune the experimental parameters in such a way that agreement with the theory is found, in most cases the experiments show shedding of vortices in the initial stage of the spin-up or spin-down, a phenomenon not described by the analytical model. Nonetheless, in such cases the analytical model still accounts for other observations: the alternating generation of cyclonic and anticyclonic vortices in the eastern part of the tank and their subsequent westward motion. 相似文献
264.
Geomagnetism and Aeronomy - The magnetic fields of a subterranean source observed on the Earth’s surface or from the orbit of a satellite are studied. We analyze the space of all harmonic... 相似文献
265.
The Caspian Sea is characterized in the geographic and ecological aspects, and the state of its ecosystem is estimated. The natural and anthropogenic processes that control the formation of the environmental conditions in the Caspian Sea and the distribution of principal commercial hydrobionts and their food items are analyzed. Data on modern tendencies in changes in the abiotic and biotic parameters of the ecosystem, their causes and mechanisms are summarized. Prospects of further changes related to the development of shelf fields of petroleum hydrocarbons are assessed. 相似文献
266.
D. V. Abramov M. N. Drobyshev V. N. Koneshov 《Izvestiya Physics of the Solid Earth》2013,49(4):548-553
Continuous high-precision long-term gravity measurements are carried out at the geophysical observatory located in the experimental base of Vladimir State University. The long time series of gravity acceleration and its standard deviation are obtained. The factors responsible for the increases in the studied deviations are analyzed. The recommendations for improving the accuracy of relative gravity measurements are formulated. 相似文献
267.
Digitization of the daily prominence sketches based on data from the global observational network of visual solar spectroscopes was performed for 1922–1934. More than 55000 prominences were distinguished. The results of analysis of distributions by area, height, and prominence location are presented. In addition, the prominence characteristics were compared to those obtained from more recent observations at the Kislovodsk Mountain Astronomical Station of Pulkovo Observatory. The distributions of prominence areas and heights are close to lognormal. The maximal height distribution corresponds to ~25–40 arcsecs. A second maximum also exists for prominence heights of ~70–90 arcsecs. 相似文献
268.
269.
Within the framework of a linear theory, the instability of an electron beam with a finite radius in a cold magnetised boundless plasma is considered. It is shown that a finite beam dimension influences the generation of quasi-potential waves in two aspects: the perpendicular wave number is quantised so that the frequencies of the waves are subjected to strong selection; a new kind of instability appears due to wave energy losses by emission into surrounding space. Growth rate dependence of wave numbers and frequencies is investigated for typical parameters of experiments with electron beams in space. 相似文献
270.
V. A. Marinov S. V. Meledina O. S. Dzyuba O. S. Urman O. V. Yazikova V. A. Luchinina A. G. Zamirailova A. N. Fomin 《Stratigraphy and Geological Correlation》2006,14(4):418-432
Paleontological study of Upper Jurassic and Lower Cretaceous sediments recovered by boreholes in the Agan-Vakh and Nadym-Vengapur interfluves clarified environments of their deposition. As is shown, influx of siliciclastic material to central areas of the West Siberian sea basin varied through time. Taxonomic composition and ecological structure of nektonic and benthic fossil assemblages are analyzed and considered in terms of environmental factors such as hydrodynamics, aeration, temperature, and salinity of seawater. 相似文献