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581.
Miloš Pick Ivanka Charvátová-Jakubcová Reviewer O. Novotný 《Studia Geophysica et Geodaetica》1988,32(1):47-53
Summary Runcorn's equations, which can be used to compute the stresses caused by convection flows from the outer gravity field, were transformed so that gravity anomalies or geoid heights can be employed as input data.
au aa, m n¶rt;m u n u mmu u anu, a uu nmau, u maua ma, m unam u¶rt; ¶rt; ¶rt;a, aauu u mmu uu mu¶rt;a.相似文献
582.
583.
Zdeněk Dolníček Bohuslav Fojt Walter Prochaska Jan Kučera Petr Sulovský 《Mineralium Deposita》2009,44(1):81-97
The Zálesí vein-type deposit is hosted by Early Paleozoic high-grade metamorphic rocks on the northern margin of the Bohemian
Massif. The mineralization is composed of three main stages: uraninite, arsenide, and sulfide. The mineral assemblages formed
at low temperatures (~80 to 130°C, locally even lower) and low pressures (<100 bars). The salinity of the aqueous hydrothermal
fluids (0 to 27 wt.% salts) and their chemical composition vary significantly. Early fluids of the oldest uraninite stage
contain a small admixture of a clathrate-forming gas, possibly CO2. Salinity correlates with oxygen isotope signature of the fluid and suggests mixing of brines [δ
18O around +2‰ relative to standard mean ocean water (SMOW)] with meteoric waters (δ
18O around −4‰ SMOW). The fluid is characterized by highly variable halogen ratios (molar Br/Cl = 0.8 × 10−3 to 5.3 × 10−3; molar I/Cl = 5.7 × 10−6 to 891 × 10−6) indicating a dominantly external origin for the brines, i.e., from evaporated seawater, which mixed with iodine-enriched
halite dissolution brine. The cationic composition of these fluids indicates extensive interaction of the initial brines with
their country rocks, likely associated with leaching of sulfur, carbon, and metals. The brines possibly originated from Permian–Triassic
evaporites in the neighboring Polish Basin, infiltrated into the basement during post-Variscan extension and were finally
expelled along faults giving rise to the vein-type mineralization. Cenozoic reactivation by low-salinity, low-δ
18O (around −10‰ SMOW) fluids of mainly meteoric origin resulted in partial replacement of primary uraninite by coffinite-like
mineral aggregates. 相似文献
584.
The western part of the Bohemian Massif (West-Bohemia/Vogtland region at the Czech-German border) is characterized by relatively
frequent intraplate earthquake swarms and by other manifestations of present-day geodynamic activity. During the strong earthquake
swarm at the turn of the years 1985 and 1986, significant changes in mineral spring parameters were observed at the spa of
Františkovy Lázně. In this study, we present all available data on the mineral springs parameters, and we discuss them in
terms of relations to seismic activity. Some changes in discharge were very distinct, amounting up to 40%, and had a co-seismic
character. The changes in temperature were less noticeable, but preceded the beginning of the swarm by several months. Some
hydrological changes persisted for nearly two years after the earthquake swarm. The character of the observed changes seems
to support the hypothesis on an injection of mantle fluids, in particular of CO2, as the main triggering mechanism of the earthquake swarm and the main cause of discharge anomalies. 相似文献
585.
Horálek Josef Fischer Tomáš Boušková Alena Jedlička Petr 《Studia Geophysica et Geodaetica》2000,44(2):107-125
The local network of digital seismic stations WEBNET monitors the seismic activitv of practically the whole region of Western Bohemia/Vogtland swarms. The network consists of ten short-period stations and one very broadband station. The paper describes the configuration of the network, instrumental equipment and the basic parameters of the stations. The method of and formula for computing the local magnitudes from the WEBNET and KRASLICE seismograms are also given. Based on continuous WEBNET observations in the period 1995-1999, we were able to improve the model of temporal and spatial energy release in the region, the principal characteristics of which are summarised in the paper. Apart from direct P and S waves, the WEBNET seismograms also contain other significant P- and S-type waves, provisionally interpreted as reflected PxP, SxS and SxP waves. The fundamental characteristics of these waves are given in the paper, and tentative mechanisms of their origination are discussed. The large residua in the travel times of the P and S waves, and the discrepancies in the seismograms recorded at stations located east of the principal focal zone are pointed out. 相似文献
586.
Surface water quality can vary a lot with fluctuating discharge during a Rainfall – runoff event. This paper uses a set of hydrological and hydrochemical variables to explain concentration–discharge loops and hysteresis of ${\rm NO}_{3}^{- } $ , ${\rm NH}_{4}^{ + } $ and total suspended solids in a brook dewatering a small upland agricultural catchment in the Czech Republic. Our study is based on data collected by a continuous monitoring approach provided by an automatic ISCO sampler both from snow thawing and rainfall – runoff events. Methods of correlation, regression and principal component analysis (PCA) were employed to reveal possible relationships among the variables. For ${\rm NO}_{3}^{- } $ and ${\rm NH}_{4}^{ + } $ , we found several types of concentration–discharge loops due to the loop rotation direction and also the loop curvature shape, in mutual combinations, no matter which type of a hydrological event it was related to. PCA indicated that ${\rm NO}_{3}^{- } $ loops correlated mostly with the length of a rising hydrograph limb and with the slope of the initial phase of a falling hydrograph limb, 5‐day amount of precipitation and runoff coefficient. In case of ${\rm NH}_{4}^{ + } $ , the concentrations usually increased with elevated discharge, whereas PCA did not detect any closer linkages. For suspended solids, an unambiguous positive monotonic relationship was discovered. Although no definite pattern was found, this study showed the necessity of a continuous water quality monitoring system as an approach for capturing and understanding relationships between solute concentrations and runoff formation for tracing and modelling catchment pollution sources and describing transport processes. 相似文献
587.
Michael K. Shepard Beth Ellen Clark Ellen S. Howell Jon D. Giorgini Steven J. Ostro Brian Warner Petr Pravec Thomas Bennett Raoul Behrend Josep Coloma Andrew Rivkin 《Icarus》2008,195(1):184-205
We observed ten M- and X-class main-belt asteroids with the Arecibo Observatory's S-band (12.6 cm) radar. The X-class asteroids were targeted based on their albedos or other properties which suggested they might be M-class. This work brings the total number of main-belt M-class asteroids observed with radar to 14. We find that three of these asteroids have rotation rates significantly different from what was previously reported. Based on their high radar albedo, we find that only four of the fourteen—16 Psyche, 216 Kleopatra, 758 Mancunia, and 785 Zwetana—are almost certainly metallic. 129 Antigone has a moderately high radar albedo and we suggest it may be a CH/CB/Bencubbinite parent body. Three other asteroids, 97 Klotho, 224 Oceana, and 796 Sarita have radar albedos significantly higher than the average main belt asteroid and we cannot rule out a significant metal content for them. Five of our target asteroids, 16 Psyche, 129 Antigone, 135 Hertha, 758 Mancunia, and 785 Zwetana, show variations in their radar albedo with rotation. We can rule out shape and composition in most cases, leaving variations in thickness, porosity, or surface roughness of the regolith to be the most likely causes. With the exception of 129 Antigone, we find no hydrated M-class asteroids (W-class; Rivkin, A.S., Howell, E.S., Lebofsky, L.A., Clark, B.E., Britt, D.T., 2000. Icarus 145, 351-368) to have high radar albedos. 相似文献
588.
This contribution is a follow-up to the recent paper of Kuznetsov et al. (Contrib. Astron. Obs. Skalnaté Pleso
36, 85, 2006) on the ground level enhancement (GLE) on 20 January 2005. We focused on a study of Forbush decrease (FD) of 17 – 18 and
21 – 22 January 2005, respectively. The data from the neutron monitor at Lomnicky Štít (1 min counts) and from the Geomagnetic
Observatory in Hurbanovo, both in Slovakia, were used as the basis for our investigation. The data on magnetic field and solar
wind from GOES 10 and 12, SOHO-CELIAS, ACE and WIND satellites were used for better understanding of the global evolution
of the event. The magnetic field is transformed to the RTN (Radial – Tangential – Normal) system where only the disturbed
part of the field is compared, i.e., daily variations and a constant part are subtracted. The field reduction method is described. Our results are temporal vector
diagrams of variation of all parameters at all positions from where we used the data. The amplitudes of |B| exceed 100 nT and variations during the arrival of the wavefront of CME take place simultaneously at the ground-based station
and at GOES satellites. The character of the variations is as if there would be regions with the dominant electric charge
of opposite signs, or electric currents with different orientations in the CME. On the basis of the values v
p and n
p and using certain assumptions we determined the mass of CME on 17 January and 21 January, respectively, of 1012 kg. A decrease of the cosmic ray level runs suddenly (during 10 minutes), starting, however, about two hours after a sudden
change of the magnetic field. 相似文献
589.
590.