全文获取类型
收费全文 | 649篇 |
免费 | 11篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 67篇 |
地球物理 | 122篇 |
地质学 | 284篇 |
海洋学 | 36篇 |
天文学 | 118篇 |
综合类 | 4篇 |
自然地理 | 23篇 |
出版年
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 9篇 |
2014年 | 16篇 |
2013年 | 28篇 |
2012年 | 11篇 |
2011年 | 27篇 |
2010年 | 23篇 |
2009年 | 42篇 |
2008年 | 18篇 |
2007年 | 25篇 |
2006年 | 18篇 |
2005年 | 24篇 |
2004年 | 19篇 |
2003年 | 17篇 |
2002年 | 14篇 |
2001年 | 6篇 |
2000年 | 13篇 |
1999年 | 8篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1982年 | 16篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 5篇 |
1971年 | 9篇 |
1970年 | 6篇 |
1968年 | 6篇 |
1967年 | 7篇 |
1959年 | 7篇 |
1954年 | 5篇 |
排序方式: 共有663条查询结果,搜索用时 0 毫秒
571.
Werner Höhne 《Theoretical and Applied Climatology》1961,11(1):126-134
Zusammenfassung Es wird gezeigt, daß es möglich ist, auf galvanischem Wege Thermosäulen zu erzeugen, deren Empfindlichkeit von der Bezugstemperatur unabhängig ist. Der galvanische Niederschlag muß hierbei eine bestimmte Stärke besitzen, die vom Querschnitt des Materials der Unterlage abhängt. Eine entsprechend dimensionierte Kupfer-Konstantan-Thermosäule besitzt eine um 23% geringere Empfindlichkeit als eine normale Thermosäule der gleichen Materialien und gleicher Gliederzahl; ihre Linearität wird durch dieses Verfahren verbessert.
Mit 2 Textabbildungen 相似文献
Summary The possibility is shown to produce a thermopile by electroplating, the sensitivity of which is independent from the reference temperature. In this case the deposition must have a fixed thickness depending upon the cross section of the base wire. A copper-constantan-thermopile made in this way has a sensitivity being 23 per cent smaller than that of a normal thermopile of the same materials and with the same number of junctions; its linearity is improved by this process.
Résumé On montre qu'il est possible de construire une pile thermoélectrique par galvanoplastie dont la sensibilité est indépendante de la température de référence. Le dépôt galvanique doit avoir une certaine épaisseur en rapport avec la section du noyau. Une pile cuivre-constantan de cette nature a une sensibilité de 23% plus faible qu'une pile normale de même composition et du même nombre de soudures; le processus de fabrication indiqué rend plus linéaires ses indications.
Mit 2 Textabbildungen 相似文献
572.
A traditional mulching technique used in Lanzarote, Canary Islands, allows dry farming as well as pronounced water savings in irrigation. It is known to reduce evaporational losses, but is also supposed to enhance the nocturnal condensation of water vapour from the atmosphere. The mulch layer consists of porous volcanic rock fragments abundantly available on the island. The mulched surface is believed to cool rapidly and to be more hygroscopic than a bare soil surface. This was investigated during a field experiment conducted over 68 nights during different seasons in 2001 and 2002, as well as some simple laboratory measurements. It was found that nocturnal condensation on the mulch surface (max 0.33 mm) was lower than on the bare soil surface (max 0.57 mm) or any one of three alternative mulch substrates. However, a slightly stronger nocturnal cooling of the mulched as compared to the bare surface was present. It is shown that these contrary findings can be explained by the higher hygroscopicity of the dry loam soil, resulting in condensation gains beyond the strict definition of dew. Differences in plant-availability of non-hygroscopic dew water and hygroscopic water uptakes are discussed, and conditions under which mulching would show positive condensation effects are defined. This includes a theoretical section demonstrating that non-hygroscopic mulch layers of a proper thickness can provide small amounts of dew to plant roots at the mulch–soil interface. This condensation could also happen during the day and would be favoured by a high amplitude of the diurnal atmospheric moisture cycle. 相似文献
573.
Jennifer L. Lewicki Deborah Bergfeld Carlo Cardellini Giovanni Chiodini Domenico Granieri Nick Varley Cynthia Werner 《Bulletin of Volcanology》2005,68(1):76-90
We present a comparative study of soil CO2 flux () measured by five groups (Groups 1–5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1–5 measured using the accumulation chamber method at 5-m spacing within a 900 m2 grid during a morning (AM) period. These measurements were repeated by Groups 1–3 during an afternoon (PM) period. Measured ranged from 218 to 14,719 g m−2 day−1. The variability of the five measurements made at each grid point ranged from ±5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO2 emission rate estimates varied between groups by only ±22%. All three groups that made PM measurements reported an 8–19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO2 emission rate of one data set and to map the spatial distribution, we compared six geostatistical methods: arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods. While the total CO2 emission rates estimated using the different techniques only varied by ±4.4%, the maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of , but a variety of geostatistical methods are appropriate to estimate the total CO2 emission rate from a study area, which is a primary goal in volcano monitoring research.Editorial responsibility: H Shinohara 相似文献
574.
Robert A. Werner 《Journal of Geodesy》2017,91(3):307-328
Formulas of a homogeneous polyhedron’s gravitational potential typically include two arctangent terms for every edge of every face and a special term to eliminate a possible facial singularity. However, the arctangent and singularity terms are equivalent to the face’s solid angle viewed from the field point. A face’s solid angle can be evaluated with a single arctangent, saving computation. 相似文献
575.
576.
V. Guineva G. Witt J. Gumbel M. Khaplanov R. Werner J. Hedin S. Neichev B. Kirov L. Bankov P. Gramatikov V. Tashev M. Popov K. Hauglund G. Hansen J. Ilstad H. Wold 《Geomagnetism and Aeronomy》2009,49(8):1292-1295
The resonance transition 2P-2S of the atomic hydrogen (Lyman-alpha emission) is the strongest and most conspicuous feature in the solar EUV spectrum. The Lyman-alpha radiation transfer depends on the resonance scattering from the hydrogen atoms in the atmosphere and on the O2 absorption. Since the Lyman-alpha extinction in the atmosphere is a measure for the column density of the oxygen molecules, the atmospheric O2 density and temperature profiles can be calculated thereof. A detector of solar Lyman-alpha radiation was manufactured in the Stara Zagora Department of the Solar-Terrestrial Influences Laboratory (STIL). Its basic part is an ionization camera, filled in with NO. A 60 V power supply is applied to the chamber. The produced photoelectric current from the sensor is fed to a two-channel amplifier, providing analog signal. The characteristics of the Lyman-alpha detector were studied. It passed successfully all tests and the results showed that the so-designed instrument could be used in rocket experiments to measure the Lymanalpha flux. From the measurements of the detector, the Lyman-alpha vertical profile can be obtained. Programs are created to compute the O2 density, atmospheric power and temperature profiles based on Lymanalpha data. The detector design appertained to ASLAF project (Attenuation of the Solar Lyman-Alpha Flux), a scientific cooperation between STIL—Bul.Acad.Sci., Stara Zagora Department and the Atmospheric Physics Group at the Department of Meteorology (MISU), Stockholm University, Sweden. The joint project was part of the rocket experiment HotPay I, in the ALOMAR eARI Project, EU’s 6th Framework Programme, Andøya Rocket Range, Andenes, Norway. The project is partly financed by the Bulgarian Ministry of Science and Education. 相似文献
577.
This paper presents the first high resolution temperature data from a small Agrostis magellanica mire on subantarctic Marion Island as part of an ongoing island‐wide monitoring project on subsurface ground temperature variability. Variations in ground temperatures were found to be directly linked to the passage of synoptic scale weather systems that influence thermal characteristics and heat fluxes especially in the upper 30 cm of the mire. Preliminary data published here suggest that shallow temperatures will be most affected by changes in synoptic climate that Marion Island is currently experiencing with an increase in average temperatures and a reduction in temperature variability with depth. This study proposes that to effectively detect the ecosystem responses to climate change in a maritime sub‐Antarctic environment the temporal scale of measurement needs to be at least on a diurnal scale to be effective. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
578.
Microbial biodegradation of organic substances takes place during drinking water treatment, but also in the distribution net, if the drinking water still contains biodegradable organic substances. This phenomenon is called regrowth. The regrowth potential of a drinking water is high, when for instance ozonation is used as the last step of treatment. It was proved before, that ozonation increases the biodegradability of humic substances, which are the main fraction of organic carbon in drinking water. In this work the objective was to check, if chlorination has a similar effect on humic substances. Using the method developed by Werner of measuring the regrowth potential of a water it could be shown by dilution series with chlorinated and unchlorinated humic substances that the substrate quality of these organics is increased by chlorination. The better substrate quality is seen in the chlorinated solutions, which might contain also low molecular weight organic compounds, but also in the fulvic acid fraction after XAD-enrichment, which removes most of the low molecular weight organic compounds. The chlorination creates in the fulvic acid solutions a shift of molecular size to smaller molecules and higher polar substances, which might be the reasons for the better biodegradability. From these results it can be concluded, that chlorination produces substances, which are more easily biodegradable. But this will not produce regrowth problems as long as there is free chlorine present as a disinfectant. In contrast, when the chlorine demand is very high and no free chlorine is left, this might produce high colony counts in the distribution net. 相似文献
579.
580.