全文获取类型
收费全文 | 834篇 |
免费 | 38篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 36篇 |
大气科学 | 33篇 |
地球物理 | 265篇 |
地质学 | 330篇 |
海洋学 | 49篇 |
天文学 | 121篇 |
综合类 | 7篇 |
自然地理 | 33篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 11篇 |
2020年 | 11篇 |
2019年 | 19篇 |
2018年 | 32篇 |
2017年 | 38篇 |
2016年 | 58篇 |
2015年 | 50篇 |
2014年 | 43篇 |
2013年 | 59篇 |
2012年 | 40篇 |
2011年 | 43篇 |
2010年 | 41篇 |
2009年 | 48篇 |
2008年 | 34篇 |
2007年 | 37篇 |
2006年 | 20篇 |
2005年 | 21篇 |
2004年 | 15篇 |
2003年 | 9篇 |
2002年 | 20篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1970年 | 3篇 |
排序方式: 共有874条查询结果,搜索用时 31 毫秒
51.
František Jiříček Pavel Tříska Jaroslav Vojta Ya. I. Likhter V. V. Korobovkin Reviewer V. Bumba 《Studia Geophysica et Geodaetica》1973,17(1):49-58
Summary The Interkosmos5 VLF experiment consisted of a spectrum analyser with twelve narrow-band channels and broadband measurements between0.07 and20 kHz using an analogue telemetry with a tape recorder on board. The apparatus used in the experiment is shortly described, some examples ofVLF phenomena observed are given and a review of all analogue data recorded is shown in a graphical calendar. 相似文献
52.
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
53.
Zusammenfassung Es wird der Einfluss des sogenannten Vorticity-Zentrums auf die Grenzfläche zweier Luftmassen der mittleren geographischen Breiten studiert. Zwecks Aufklärung der Rolle des Bewegungs- und Druckfeldes in diesem Prozesse wurde ein einfaches Modell konstruiert und numerisch gelöst. Die sich entwickelnde frontale Welle kann beziehungsweise als ein Anfangswert beim Lösen der mit der Stabilität der Wellen verbundenen Probleme mittels der Gleichungen, linearisiert durch die Methode der kleinen Störungen, dienen. Bei der Konstruktion des Modells wird ausser anderem von der Geometrie der Bewölkung ausgegangen, wie sie auf den Aufnahmen der meteorologischen Satelliten erfasst ist. 相似文献
54.
55.
56.
Żaneta Polkowska Aleksander Astel Marzena Grynkiewicz Tadeusz Górecki Jacek Namieśnik 《Journal of Atmospheric Chemistry》2002,41(3):239-264
The paper presents monitoring results and environmental pollution assessment for the Gdask-Sopot-Gdynia Tricity (Poland), based onanalysis of precipitation. Precipitation samples were collected over a period of 12 months (January–December 1998) at ten locations in the Tricity. The following selected ions were determined in the samples:SO4
2–, F–, Cl–, NO3
–,PO4
3–, NH4
+, Na+,Mg2+, Ca2+, K+. The results were subjected to full statistical evaluation. Values of the parameters determined were correlated with each other. An attempt was made to explain co-occurrences of certain ions and the significance of their mutual effects. Pollutant concentrations and loads in precipitation were also correlated with data on wind direction and temperature in the region.Deposition of pollutants was very high in spring due to the prevailing air circulation patterns and low temperatures. Analysis of the correlations between co-occurring ions confirmed the significant impact of the location (sea coast) on the composition of rain water. Ionic ratios in rainwater were similar to those observed for sea salt samples. In addition, heavy traffic was most probably responsible for high concentrations of various forms of nitrogen and sulphates in the vicinity of major highways. 相似文献
57.
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
58.
Trace Metal Solid State Speciation in Aerosols of the Northern Levantine Basin,East Mediterranean 总被引:3,自引:0,他引:3
Mustafa Koçak Nilgun Kubilay Barak Herut Malcolm Nimmo 《Journal of Atmospheric Chemistry》2007,56(3):239-257
An established three stage sequential leach scheme was applied to a series of selected high volume aerosol samples (n = 35) collected from the Turkish Eastern Mediterranean coastline (Erdemli). Samples were selected according to their air
mass back trajectory history to reflect the contrasting mixtures of aerosol material present in the Eastern Mediterranean
marine aerosol. Two populations were adopted, those samples which were classed as “anthropogenic” and those which were “Saharan”
dominated aerosol populations. Applying the three stage leach it was possible to define the proportion for each of the considered
metals (Al, Fe, Cu, Pb, Cd, Zn and Mn) present in the (a) “exchangeable” (b) “carbonate / oxide” and (c) “refractory” phases,
representing novel solid state aerosol speciation data for this marine system. Clear trends were established, conforming with
data from previous studies with mainly crustal derived metals (Al and Fe) being present in the refractory phases (Al > 88%;
Fe > 84%) and those influenced by anthropogenic sources being dominating in the exchangeable phase, although for these metals
the variability was comparatively high (12–64%; 19–85%; 40–100% for Zn, Pb and Cd, respectively). For the majority, greater
exchangeable fractions were present the lower the crustal source contribution to the aerosol population, whereas the “refractory”
fraction exhibited contrasting behaviour. This was illustrated by the novel application of the mixing diagram, presenting
each of the three speciation stages against the corresponding percent anthropogenic contribution to each collected sample.
Zn, Pb and Cd all illustrated progressive decrease in the percent exchangeable with increasing crustal contribution to the
aerosol population. The percent exchangeable was discussed in terms of its use to represent the upper limit of the bioavailable
fraction of metal associated with the aerosol, post deposition. The mixing diagram approach enabled the prediction of the
residual fractions for Cd, Pb and Zn (41 ± 4%; 62 ± 4% and 82 ± 5%, respectively,) in Saharan end-member material. 相似文献
59.
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
60.
This paper presents the development and utilisation of an automated image processing algorithm for detection and analysis
of grains. Using optical polarising microscopy, a set of colored images are collected from an area on a thin section. A filtering
operation, using rotation of a morphological alternating sequence filter (based on a structuring element), is used to remove
twinning features within individual grains. Filtering is followed by the watershed segmentation technique to determine grain
boundaries. The method is used for the identification of calcite grains in marble and the subsequent analysis of morphological
anisotropy. 相似文献