全文获取类型
收费全文 | 6317篇 |
免费 | 150篇 |
国内免费 | 59篇 |
专业分类
测绘学 | 161篇 |
大气科学 | 452篇 |
地球物理 | 1685篇 |
地质学 | 1926篇 |
海洋学 | 440篇 |
天文学 | 1242篇 |
综合类 | 14篇 |
自然地理 | 606篇 |
出版年
2021年 | 58篇 |
2020年 | 70篇 |
2019年 | 88篇 |
2018年 | 114篇 |
2017年 | 111篇 |
2016年 | 155篇 |
2015年 | 152篇 |
2014年 | 146篇 |
2013年 | 305篇 |
2012年 | 207篇 |
2011年 | 273篇 |
2010年 | 242篇 |
2009年 | 318篇 |
2008年 | 237篇 |
2007年 | 235篇 |
2006年 | 207篇 |
2005年 | 189篇 |
2004年 | 206篇 |
2003年 | 206篇 |
2002年 | 196篇 |
2001年 | 122篇 |
2000年 | 131篇 |
1999年 | 118篇 |
1998年 | 111篇 |
1997年 | 78篇 |
1996年 | 96篇 |
1995年 | 84篇 |
1994年 | 81篇 |
1993年 | 81篇 |
1992年 | 70篇 |
1991年 | 82篇 |
1990年 | 66篇 |
1989年 | 72篇 |
1988年 | 62篇 |
1987年 | 91篇 |
1986年 | 74篇 |
1985年 | 86篇 |
1984年 | 107篇 |
1983年 | 88篇 |
1982年 | 82篇 |
1981年 | 95篇 |
1980年 | 86篇 |
1979年 | 76篇 |
1978年 | 96篇 |
1977年 | 69篇 |
1976年 | 73篇 |
1975年 | 60篇 |
1974年 | 54篇 |
1973年 | 56篇 |
1971年 | 72篇 |
排序方式: 共有6526条查询结果,搜索用时 15 毫秒
21.
A microflare or a group of Ellerman bombs was found to be associated with several points of white-light enhancements. These points had similar sizes as facular points (d 0.3 arc sec). Temporal evolution of these activities is described. Origins of these activities are discussed to be deeply seated excess heating in chromospheric and photospheric levels. 相似文献
22.
Richard A. Serafin 《Celestial Mechanics and Dynamical Astronomy》1996,65(4):389-398
We deal here with the efficient starting points for Kepler's equation in the special case of nearly parabolic orbits. Our approach provides with very simple formulas that allow calculating these points on a scientific vest-pocket calculator. Moreover, srtarting with these points in the Newton's method we can calculate a root of Kepler's equation with an accuracy greater than 0.001 in 0–2 iterations. This accuracy holds for the true anomaly || 135° and |e – 1| 0.01. We explain the reason for this effect also.Dedicated to the memory of Professor G.N. Duboshin (1903–1986). 相似文献
23.
Stanislav Horník 《GeoJournal》1993,31(4):379-382
Some results of biogeographic research on meadows in the Dyje-Svratka basin in the Czech Republic. The paper shows one example of biogeographic inventory of natural ecosystems in an unflooded meadow in the Dyje-Svratka basin. It is part of the complex physio-geographic research of the Geographic Department of the Masaryk University in Brno aimed at gaining a basis for territorial interpretation of ecological regularities and territorial application of general ecological optimizing principles. A segment of biocenosis of Ulmi-fraxineta carpini has been analyzed (Zlatník 1956).The endeavour of Czech geographers to study geosystems of various dimensions completely gets in the limelight. In question is the understanding of mutual relationship of components of geosystems based on the exchange of mass and energy. There are two ways of studying them: spatial relations or approaches concentrated on processes. In contrast to the above unilateral concept, the endeavour to make the approaches compatible appears rarely. This complex view is made possible by geobiocenologically taken biogeography in papers of Zlatník and Rauer, their students and successors. This paper shows only one example of the results of biogeographic stock-taking of meadows in the Dyje-Svratka basin, indicating relations of eco- and geosystems which confirm the necessity of ecological orientation of the present biogeography and its potential contribution to ecology. 相似文献
24.
Miroslav Krs František Novák Marta Krsová Petr Pruner Jiří Jansa 《Studia Geophysica et Geodaetica》1993,37(4):382-400
Summary This study is a follow up of the investigation of some magnetic properties and metastability of greigite in samples obtained from Miocene claystones in the Kruné hory (Erzgebirge) Piedmont basins (Bohemia). Three different methods of upgrading the smythite were applied; the magnetic properties of the concentrates are compared. The thermal conversion of smythite sets in at 200°C while greigite converts at 250°C. The first intermediate products to be formed are iron sulphides, marcasite clearly dominating over pyrite and pyrrhotite. Apart from a Fe3+ sulphate with a composition of Fe2(SO4)3, oxidation of these sulphides gives rise to -Fe2O3. The result of the subsequent decomposition of the mentioned sulphate is the formation of -Fe2O3, which retains the sulphate structure. The final product of the thermal decomposition at 800°C is -Fe2O3. In the smythite concentrate the conversion to Fe3+ sulphate and -Fe2O3 is about twice as intensive as in greigite. No direct conversion to -Fe2O3 was found. During the thermal process self-reversals of remanence were observed, in various samples as many as four reversals in the temperature interval from 340 to 590°C. The occurrences of self-reversals of remanence were only observed at high degrees of thermal demagnetization, of the order of 10–2 down to 10–3 in the temperature interval of sulphide origin (below 400°C), and of the order of 10–4 down to 10–6 in the temperature interval of Fe-oxides origin (above 400°C).Presented at the 3rd Conference on New Trends in Geomagnetism, Castle of Smolenice, Czechoslovakia, June 22–29, 1992 相似文献
25.
26.
Measurements made when testing an interferometric system for imaging the sodium emission indicate that, between 3 and 7.5 arc min (9 and 23RJ) from Jupiter, the observed emissions can probably be attributed to terrestrial airglow. 相似文献
27.
28.
A high-resolution (0.6 cm?1) spectrum of Jupiter at 5 μm recorded at the Kuiper Airborne Observatory is used to determine upper limits to the column density of 19 molecules. The upper limits to the mixing ratios of SiH4, H2S, HCN, and simple hydrocarbons are discussed with respect to current models of Jupiter's atmosphere. These upper limits are compared to expectations based upon the solar abundance of the elements. This analysis permits upper limit measurements (SiH4), or actual detections (GeH4), of molecules with mixing ratios with hydrogen as low as 10?9. In future observations at 5 μm the sensitivity of remote spectroscopic analyses should permit the study of constituents with mixing ratios as low as 10?10, which would include the hydrides of such elements as Sn and As as well as numerous organic molecules. 相似文献
29.
30.