全文获取类型
收费全文 | 769篇 |
免费 | 32篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 16篇 |
地球物理 | 232篇 |
地质学 | 263篇 |
海洋学 | 25篇 |
天文学 | 204篇 |
综合类 | 6篇 |
自然地理 | 31篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 28篇 |
2017年 | 35篇 |
2016年 | 50篇 |
2015年 | 36篇 |
2014年 | 42篇 |
2013年 | 36篇 |
2012年 | 33篇 |
2011年 | 43篇 |
2010年 | 30篇 |
2009年 | 44篇 |
2008年 | 37篇 |
2007年 | 39篇 |
2006年 | 30篇 |
2005年 | 27篇 |
2004年 | 21篇 |
2003年 | 17篇 |
2002年 | 21篇 |
2001年 | 8篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 4篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有801条查询结果,搜索用时 15 毫秒
51.
The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations 总被引:1,自引:1,他引:1
Andrzej Krankowski Irk I. Shagimuratov Lubomir W. Baran Galina Yakimova 《Acta Geophysica》2007,55(4):490-508
GPS data from the International GNSS Service (IGS) network were used to study the development of the severe geomagnetic storm
of November 7–12, 2004, in the total electron content (TEC) on a global scale. The TEC maps were produced for analyzing the
storm. For producing the maps over European and North American sectors, GPS measurements from more than 100 stations were
used. The dense network of GPS stations provided TEC measurements with a high temporal and spatial resolution. To present
the temporal and spatial variation of TEC during the storm, differential TEC maps relative to a quiet day (November 6, 2004)
were created.
The features of geomagnetic storm attributed to the complex development of ionospheric storm depend on latitude, longitude
and local time. The positive, as well as negative effects were detected in TEC variations as a consequence of the evolution
of the geomagnetic storm. The maximal effect was registered in the subauroral/auroral ionosphere during substorm activity
in the evening and night period. The latitudinal profiles obtained from TEC maps for Europe gave rise to the storm-time dynamic
of the ionospheric trough, which was detected on November 7 and 9 at latitudes below 50°N. In the report, features of the
response of TEC to the storm for European and North American sectors are analyzed. 相似文献
52.
Measurements of topsoil magnetic susceptibility are often used for quick assessment of soil contamination of anthropogenic
origin, with heavy metals or other pollutants. However, because of complicated correlations between low-field magnetic susceptibility
(shortened to magnetic susceptibility) of topsoil and soil pollution, the outcome of a field magnetometry survey can not be
related directly to soil pollution. For each case study, the results should be interpreted on their own taking into account
not only the type of pollution but also pedogenic, biogenic and environmental factors. In practice, it is very difficult to
measure and consider all these factors. Here we illustrate the merit of geostatistical methods, which are focused on the spatial
variability of a phenomenon, in the interpretation of soil magnetometry results.
This article presents the analysis of spatial variability of top soil layers magnetic susceptibility-within the Upper Silesia
Industrial Region (USIR)-using semivariance analysis. It also explains how to adjust the sampling density of field magnetometry
measurements to spatial variability of the soil pollution as well as to the spatial scale of the investigated area. For this
purpose, the values of magnetic susceptibility have been measured by using various sampling densities at areas of different
size located within USIR. This enabled to determine the main scales of magnetic susceptibility spatial variability of soils
within USIR using semivariance. A few distinct scales of variability were found from the site scale to a more regional scale.
Variability ranges of 30 km, 12 km, and 5 km refer to the large regional scale, whereas smaller ranges of few hundreds down
to a few tens of meters, can be attributed to the local (site) scale. In addition, the precision of the measuring campaigns,
performed within USIR with different sampling densities, was compared through the analysis of the spatial variability of the
soil magnetic susceptibility signal by using ordinary kriging.
jarek97@yahoo.com, piotr.fabijanczyk@is.pw.edu.pl 相似文献
53.
Alfred Kepiński 《Aquatic Sciences - Research Across Boundaries》1962,24(2):272-290
Ohne Zusammenfassung 相似文献
54.
Summary Two groups of basaltic rocks with normal and reversed NRM were examined. It was found that in both groups the primary NRM, synchronous with the period of rock formation, is preserved. Relations of the primary NRM to the origin and the degree of oxidation of magnetic minerals were considered in detail. 相似文献
55.
56.
57.
Żelaźniewicz Andrzej Marheine Dirk Oberc-Dziedzic Teresa 《International Journal of Earth Sciences》2003,92(2):185-194
A Variscan foreland in western Poland comprises two NW-trending basement highs, which are concealed under Carboniferous through Triassic strata of the Fore-Sudetic Monocline (FSM). Both highs consist of multiply deformed quartz-sericite - albite - chlorite phyllites of unknown protolith age. 40Ar/39Ar laser probe dating of white micas in up to 0.5-mm-thick mica layers, which form the S2 axial-plane foliation in phyllites of the Wolsztyn-Leszno High, yielded an age of 340.1DŽ.6 Ma for the lower greenschists facies metamorphism and probably also for the F2 folding. This deformation was associated and followed by thrusting, which brought about the basement highs. The latter delivered clasts to overlying late Viséan-early Namurian flysch basin that was mainly sourced from the Saxothuringian Sudetes in which most of the deformation occurred between 345-335 Ma. The FSM basement may represent an independent terrane, referred to as the Wielkopolska terrane, belonging to the Armorican Terrane Assemblage. 相似文献
58.
Pollution of the water environment by mining waters is a problem not only in Poland, but worldwide. This study investigated the mollusc communities in seven mining subsidence reservoirs affected by coal mine output (the Katowicka Upland, Upper Silesia, Southern Poland). The objective of the survey was to determine the relationship between the molluscs and their environments and to evaluate the ecological-conservation value of freshwater habitats which support rare and vulnerable molluscs. From 1993 to 2005, 23 mollusc species were recorded. Our result confirmed an invasion by Potamopyrgus antipodarum (Gray, 1843), whose density varied from 2 to 2422 individuals/m2 in the waters of the Katowicka Upland. A few rare and vulnerable species were found, e.g. Acroloxus lacustris (Linnaeus, 1758), Hippeutis complanatus (Linnaeus, 1758), Ferrissia wautieri (Mirolli, 1960), Anodonta anatina (Linnaeus, 1758), Musculium lacustre (O.F. Müller, 1774) or Pisidium casertanum (Poli, 1791). Principal component analysis showed a positive correlation between mollusc density and pH, the concentration of chlorides, the total hardness, alkalinity and total dissolved solids, and a negative correlation between the number of species and phosphates. Because of the distinctive environmental features of the mining subsidence reservoirs in Czułów, the research area has provided a refuge for wildlife. 相似文献
59.
Lightning discharges monitored by the SAFIR network system in Poland have been additionally identified over the 100×100 km
area near Warsaw by single-point independent recordings of electric field and Maxwell current rapid changes. The data collected
in summer thunderstorm days of 2002 showed some untypical properties of the lightning discharges which are rarely observed.
Especially remarkable was a number of ground multi-stroke flashes with the return strokes (RS) which transported to the earth
charges of opposite signs. Bipolar flashes (BF) of this kind were mostly involved in the events in which the nearby intracloud
(ic) and cloud-to-ground (c-g) discharges were very closely associated in time. Events of such a close collocation of two
different types of lightning discharges, previously called the complex lightning discharge events (CLDE), were quite often
observed during summer thunderstorms in Poland.
The events of this kind, i.e. 8 flashes, identified by the SAFIR detection system as BF’s present the multiple stroke flashes
of the mean horizontal separation distance between striking points of particular RS equal to (2.8 ± 2.1) km and of the mean
time interval between strokes of (46.8 ± 74.4) ms. The time separation between the observed BF and the adjacent ic flashes
was from 0.1 to 335 ms, and horizontal separation distance between them ranged from 1.8 to 14.5 km. The multiplicity of the
recorded BF’s ranged from 2 to 4 strokes. Four of these BF’s followed the ic discharge, but the other three preceded the ic
and one was alone with no close ic. 相似文献
60.
Leszek Marynowski Michał Zatoń Bernd R.T. Simoneit Angelika Otto Mariusz O. Jędrysek Cezary Grelowski Slawomir Kurkiewicz 《Applied Geochemistry》2007
The comprehensive biomarker characteristics from previously undescribed Middle Jurassic clays of Poland are presented. The molecular composition of the organic matter (OM) derived from clays of Aalenian to Callovian age has not changed significantly through time. High relative concentrations of many biomarkers typical for terrestrial material suggest a distinct dominance of OM derived from land plants. Increasing concentrations of C29-diaster-13(17)-enes towards the northern part of the basin indicate an increase in terrestrial input. This terrestrial material would have originated from the enhanced transport of organic matter from land situated at the northern bank of the basin, i.e., the Fennoscandian Shield. The organic matter was deposited in an oxic to suboxic environment, as indicated by relatively low concentrations of C33–C35 homohopanes, moderate to high Pr/Ph ratio values, an absence of compounds characteristic for anoxia and water column stratification, such as isorenieratane, aryl isoprenoids and gammacerane, as well as common benthic fauna and burrows. δ18O measurements from calcitic rostra of belemnites suggest that the mean value of the Middle Jurassic sea-water temperature of the Polish Basin was 13.1 °C. It is suggested that this mirrored the temperature of the lower water column because belemnites are considered here to be necto-benthic. The organic matter from the Middle Jurassic basin of Poland is immature. This is clearly indicated by a large concentration of biomarkers with the biogenic configurations, such as ββ-hopanes, hop-13(18)-enes, hop-17(21)-enes, diasterenes and sterenes. The identification of preserved, unaltered biomolecules like ferruginol, 6,7-dehydroferruginol and sugiol in Protopodocarpoxylon wood samples from these sediments present particularly strong evidence for the presence of immature OM in the Middle Jurassic sediments. Moreover, the occurrence of these polar diterpenoids is important due to the fact that they are definitely the oldest known natural products detected in geological samples. 相似文献