全文获取类型
收费全文 | 418篇 |
免费 | 25篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 30篇 |
地球物理 | 93篇 |
地质学 | 185篇 |
海洋学 | 14篇 |
天文学 | 102篇 |
自然地理 | 19篇 |
出版年
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 18篇 |
2012年 | 15篇 |
2011年 | 23篇 |
2010年 | 21篇 |
2009年 | 20篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 6篇 |
2004年 | 18篇 |
2003年 | 8篇 |
2002年 | 14篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1971年 | 5篇 |
1970年 | 4篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1964年 | 3篇 |
1962年 | 4篇 |
排序方式: 共有447条查询结果,搜索用时 328 毫秒
391.
Dieter Breitschwerdt 《Astrophysics and Space Science》2001,276(1):163-176
The state of our observational and theoretical knowledge of the localinterstellar medium (LISM) is reviewed. The LISM stretches out from thelocal Cloud, surrounding the solar system to the boundary of the LocalBubble, which is a region of distinct anticorrelation between HI (N
H< 1020 cm-2) and 1/4 keV diffuse soft X-rays. After discussingsome key observations in soft X-rays, obtained by ROSAT and DXS, and inthe EUV by the EUVE satellite and the EURD instrument onboard Minisat, Iwill critically review models of the LISM. Since we cannot determine theplasma state (temperature, density, etc.) directly, the best plasmadiagnostic tool is high resolution spectroscopy. The interpretationof the data then has to rely heavily on plasma emission models. I willpoint out several caveats in the standard procedure. Preference is givento dynamical models of the Local Bubble in general and to non-equilibriumplasma emission models in particular, which have to be calculatedself-consistently. Such a model can explain (i) the deficiency of EUVlines as observed by EUVE, (ii) the dispersion measure and scintillationproperties of a nearby pulsar, (iii) the existence of local neutral HIclouds, and (iv) OVI absorption line widths. New model spectra of theLISM will be presented and briefly compared with DXS, EUVE and preliminaryEURD results. 相似文献
392.
Dieter Lorenz-Petzold 《Astrophysics and Space Science》1983,96(2):351-354
We investigate the Einstein field equations for tilted spatially self-similar Bianchi type-fV spacetimes. The solutions represent anisotropic models which can be made consistent with the observed isotropy. 相似文献
393.
Kenneth R. Meyer Dieter S. Schmidt 《Celestial Mechanics and Dynamical Astronomy》1982,28(1-2):201-207
The fundamental matrix solutionT for the variational equations of a Hamiltonian system is symplectic. We use this fact to completeT when it is only partially known. We discuss three cases. The last one gives an easy proof for the method invented by Brown in his lunar theory.Paper presented at the 1981 Oberwolfach Conference on Mathematical Methods in Celestial Mechanics.Dedicated to Victor Szebehely. 相似文献
394.
Dieter Henning 《Dynamics of Atmospheres and Oceans》1984,8(1):101
395.
Toxicological and ecotoxicological assessment of water tracers 总被引:2,自引:3,他引:2
H. Behrens U. Beims H. Dieter G. Dietze T. Eikmann T. Grummt H. Hanisch H. Henseling W. Käß H. Kerndorff C. Leibundgut U. Müller-Wegener I. Rönnefahrt B. Scharenberg R. Schleyer W. Schloz F. Tilkes 《Hydrogeology Journal》2001,9(3):321-325
Uncertainties regarding possible negative effects on the environment or on human health of authorizing tracing experiments
in groundwater and surface waters led to the establishment of a Working Group at the German Federal Environmental Agency (Umweltbundesamt
– UBA) for conducting a toxicological and ecotoxicological assessment. A total of 17 water tracers was assessed by the Working
Group on the basis of the results of toxicological tests, the available literature, and the group's expert knowledge. In the
future, tracers that pose a risk to the environment or to human health should no longer be used. Nevertheless, there are a
number of tracers that could be used in hydrogeological and hydrological investigations for water-pollution-control purposes
with no adverse environmental impact.
Electronic Publication 相似文献
396.
New information obtained about >500 keV electron intensity enhancements, which have been observed intermittently close to the outer edge of the electron radiation belt, is used in conjunction with an earlier statistical study by Brown and Stone (1972) to investigate processes which could lead to such structures. The enhancements are typically of ~20 sec duration and occur in a very narrow invariant latitude band, maximally 2° wide. The intensity increase relative to the “normal” background level is up to a factor 10, and the “spike” frequency of occurrence is strongly local time dependent, with more spikes observed in the night and dusk-noon sectors than in the noon-dawn sector. The processes investigated quantitatively are distortions of the magnetospheric topology in the equatorial region, wave-particle interactions and the effects of ionospheric currents. It is shown that the various processes which contribute to equatorial field disturbances can explain the observations. 相似文献
397.
Zusammenfassung Die vorliegende Arbeit behandelt die Ergebnisse von Messflügen zur Bestimmung der Konzentrationsverteilung von Spurengasen in der freien Atmosphäre. Auf Grund dieser Aufstiege war es erstmals möglich, den Gehalt der Atmosphäre an Schwefeldioxyd und Stickstoffdioxyd bis in Höhen von 6000 m zu erfassen. Die gewonnene mittelere Konzentrations-verteilung bietet die Basis zu Abschätzungen über den Haushalt und die mittlere Verweilzeit von SO2 und NO2 in der Troposphäre.
Summary This paper deals with the results of aircraft ascents for the measurement of the vertical distribution of atmospheric trace gases in the free atmosphere. The aircraft ascents permitted for the first time to measure the SO2- and NO2-concentration up to 6000 m. On the basis of the average distribution assumptions on the tropospheric budget of SO2 and NO2 as well as on the average tropospheric residence time of these gases were made.相似文献
398.
Vertical exchange due to horizontal density gradients in lakes; the case of Lake Lucerne 总被引:1,自引:1,他引:0
David C. van Senden Robert Portielje Alex Borer Heinz Ambühl Dieter M. Imboden 《Aquatic Sciences - Research Across Boundaries》1990,52(4):381-398
Recent field investigations have shown that differential mixing causes a significant density driven exchange between the two eastern basins of Lake Lucerne, Gersauersee and Urnersee. The long term vertical mixing characteristics during the winter mixing period and the influence of the resulting exchange flow on water quality are examined through the analysis of ten years (1964 to 1974) of monthly limnological data. Vertical homogenization of the state variables (temperature, electric conductivity and density) occurred on average once every two years in Urnersee, but not once in Gersauersee where the ten year average winter mixed-layer depth extended to 120 m. In Urnersee intense mixing was evident over the whole water column for every year. In contrast intense mixing in the deeper layers of Gersauersee occurred approximately once every four years. A three layer model shows that theT/
20 signature of the Gersauersee intermediate water correlates best with the Urnersee deep water confirming the regular occurrence of a density driven exchange. For the lower layers the oxygen consumption rate in Urnersee was approximately twice that for Gersauersee. It appears the exchange flow can act either as a source or sink for the oxygen balance of Urnersee deep water. The larger rate in Urnersee hypolimnion might also be associated with the larger sediment input to this system. Density driven exchange resulting from differential mixing is probably an important contribution to the vertical water replenishment in many lakes. 相似文献
399.
Michael Owor Tina Hartwig Andrew Muwanga Dieter Zachmann Walter Pohl 《Environmental Geology》2007,51(6):1065-1075
The abandoned Kilembe copper mine in western Uganda is a source of contaminants, mobilised from mine tailings into R. Rukoki
flowing through a belt of wetlands into Lake George. Water and sediments were investigated on the lakeshore and the lakebed.
Metal associations in the sediments reflect the Kilembe sulphide mineralisation. Enrichment of metals was compared between
lakebed sediments, both for wet and dry seasons. Total C in a lakebed core shows a general increment, while Cu and Co decrease
with depth. The contaminants are predominant (> 65%) in the ≤ 63 μm sediment size range with elevated Cu and Zn (> 28%), while
Ni, Pb and Co are low (< 18%) in all the fractions. Sequential extraction of Fe for lakeshore sediment samples reveals low
Fe mobility. Relatively higher mobility and biological availability is seen for Co, Cu and S. Heavy metal contents in lake
waters are not an immediate risk to the aquatic environment. 相似文献
400.