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221.
Stanisław P. Kasperczuk 《Celestial Mechanics and Dynamical Astronomy》2000,76(4):215-227
In a recent paper Ballersteros and Ragnisco (1998) have proposed a new method of constructing integrable Hamiltonian systems.
A new class of integrable systems may be devised using the following sequence:
, where A is a Lie algebra
is a Lie–Poisson structure on R
3, C is a Casimir for
is a reduced Poisson bracket and (A, ▵) is a bialgebra. We study the relation between a Lie-Poisson stucture Λ and a reduced Poisson bracket
, which is a key element in using the Lie algebra A to constructing this sequence. New examples of Lie algebras and their
related integrable Hamiltonian systems are given.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
222.
Milan Burša Jan Kouba Viliam Vatrt Vojtěch Vítek Marie Vojtíšková 《Studia Geophysica et Geodaetica》2000,44(1):1-12
The T/P altimeter data 1993 – 1997 (cycles 11 – 194) has been analyzed with emphases on seasonal variations in sea surface topography (SST). The amplitude of the annual variations amounted to (5.9±0.3) mm when inverted barometer (IB) corrections were applied and (2.0±0.4) mm without any IB corrections. The amplitude of the semi-annual variations in SST was small with IB corrections applied: (0.6±0.3) mm. However, when no IB corrections were applied, it was (1.8±0.4) mm, i.e. the semiannual variations are at the same level as the annual variations with no IB corrections. The phase angle offset of the annual term has shifted by about 180° when IB correction was applied. The dynamics of the ocean-atmosphere system is discussed and it is concluded that it could, at least partly, be responsible for the above observed effects. 相似文献
223.
This paper analyses the topographic context of the remaining glaciated areas in the Maladeta Massif (Central Spanish Pyrenees). These ice‐covered surfaces have been incorporated into a geographic information system (GIS) in an attempt at correlating the presence of ice with a range of topographic variables obtained from a digital elevation model. The use of generalized additive models and binary regression tree models enabled us (i) to quantify the spatial variability in the distribution of glaciers attributable to characteristics of the local terrain, (ii) to investigate the interaction between the variables that account for the ice cover distribution and (iii) to map the probability of glacier development. Our results show that although the development of glaciers depends on regional climate conditions, the topographic context is of paramount importance in determining the location, extent, shape and recent evolution of each glacial body. Thus, the joint effect of altitude, exposure to incoming solar radiation, slope and mean curvature is able to explain more than 70 per cent of the observed variance. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
224.
The Harvard CMT catalogue contains 481 shallow earthquakes that occurred between 1 January 1977 and 30 November 2005 within
a broad region defined by the geographical latitude from 3°S to 14°N and by the longitude from 91°E to 102°E. There are 230
events that occurred before the great earthquake of 26 December 2004. Their surface distribution is not uniform and the source
area of the 2004 great event appears as an area of seismic quiescence with a radius of about 100 km. There are 186 events
that occurred between the two great earthquakes of 26 December 2004 and 28 March 2005. Practically all of them are located
to the northwest from the great earthquake of 2005, that in turn was followed by 63 events, mostly located to the southeast.
The cumulative seismic moment from earthquakes before the occurrence of the great event of 2004 increased rather regularly
with time, with sudden increase about twenty years and two years before the occurrence of the great event. The seismic moment
of earthquakes between the two great events increased rapidly during the first ten-fifteen days, then flattened out and increased
slowly with time. After the great event of 2005 the seismic moment shows quiet increase during some 115 days, then sudden
jump, followed by very small activity till the end of our observations. From the spatial distribution of seismic moment of
earthquakes that occurred before the great event of 2004 it follows that its largest release appeared to the southeast from
the great event, around the rupture area of the great earthquake of 2005. The largest release of seismic moment from earthquakes
between the two great events is observed in the vicinity of the 2004 event and further up to the north. The seismic moment
from earthquakes that occurred after the great event of 2005 was mostly released in its vicinity and further down to the south. 相似文献
225.
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
226.
B. Offerle C. S. B. Grimmond K. Fortuniak K. Kłysik T. R. Oke 《Theoretical and Applied Climatology》2006,84(1-3):103-115
Summary Energy fluxes have been measured over an area near the centre of the city of Łódź, Poland, since November 2000. The site was
selected because the building style (surface cover and morphology) is typical of European cities, yet distinct from the majority
of cities where energy balance observations have been studied thus far. The multi-year dataset permits consideration of temporal
changes in energy balance partitioning over a wide range of seasonal and synoptic conditions and of the role of heat storage
and anthropogenic fluxes in the energy balance. Partitioning of net radiation into the turbulent fluxes is consistent in the
two years, with the largest differences occurring due to differing precipitation. The monthly ensemble diurnal cycles of the
turbulent fluxes over the two years are similar. The largest differences occur during the July–September period, and are attributable
to greater net radiation and lower rainfall in 2002. The latent heat flux accounts for approximately 40% of the turbulent
heat transfer on an annual basis. The average daily daytime Bowen ratio and its variability are slightly reduced during the
summer (growing) season. Anthropogenic heat is a significant input to the urban energy balance in the winter. The fluxes observed
in this study are consistent with results from other urban sites. 相似文献
227.
Summary Data from two automatic stations in Łódź (one urban and one rural) for the period 1997–2002 are analyzed to reveal urban–rural
contrasts of such parameters as air temperature, relative humidity, water vapour pressure and wind speed. Under favourable
weather conditions the highest temperature differences between the urban and rural station exceeds 8 °C. Relative humidity
is lower in the town, sometimes by more than 40%. Water vapour pressure differences can be either positive (up to 5 hPa) or
negative (up to −4 hPa). Wind speed at the urban station is on average lower by about 34% in night and 39% during daytime.
Regression analysis shows that for rural winds lower than 1.13 m s−1 urban winds can be stronger than rural speeds. Attention has also been paid to singularities in the course of the analyzed
parameters over 24 hour periods. It is shown that the typical course of the urban heat island intensity under favourable conditions
is similar in all season. Four stages of this course have been distinguished. Wind speed differences also seem to change in
a typical way. Case studies show that humidity contrasts, unlike temperature, can evolve in different ways under fine weather
conditions. Types of relative humidity evolution are proposed. 相似文献
228.
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
229.
Fernando J. Hidalgo Brian R. Silliman María Cielo Bazterrica Mark D. Bertness 《Estuaries and Coasts》2007,30(5):886-894
Rocky intertidal communities of Argentinean Patagonia are exposed to harsh physical conditions caused by dry, strong southern
trade winds (mean speed 45 km h-1, gusts up to 140 km h-1) that result in intense desiccation of intertidal organisms. Predator distributions in these communities were evaluated from
April 2003 to December 2004 at two exposed headlands and six protected bays in Cabo dos Bahias (44°50′S, 65°40′W). Crabs and
sea stars dominated the predator assemblage, with occasional scavenger snails and fish also present. During low tide, predators
were never found in the open but were always associated with shelter (primarily within mussel beds and coralline algae), suggesting
a strong predator dependency on foundation species to buffer them from physical stress. Few predators (mostly crabs) emerged
from shelter at high tide. Unlike the larger predators found on Chilean rocky shores, invertebrate predators in this system
are diminutive, generally < 2 cm. The lone exception was the newly discovered invasive green crab,Carcinus mamas. Feeding trials, gut content analyses, and visual surveys indicated that native predators feed primarily on small, soft-bodied
prey.C. mamas fed on slow-moving and sessile animals, including the super abundant musselPerumytilus purpuratus, with much greater voracity than native predators. Because native intertidal organisms are dependent on mussel beds and coralline
algae for shelter from desiccation, successful invasion ofC. mamas may lead to a significant decrease in native diversity by consuming foundation species. This study represents a preliminary
survey of predator distributions and feeding habits on the rocky shores of Argentinean Patagonia and provides important baseline
data to evaluate trophic linkages and predatory effects on Patagonian rocky shores. 相似文献
230.
Sebastin Apesteguía 《Gondwana Research》2007,12(4):533-546
A study of the abundant and undescribed isolated and associated bones and teeth from the La Amarga Formation (Barremian of Neuquén, Argentina) permitted the recognition of additional clades of sauropod dinosaurs: basal titanosauriforms, both basal and derived titanosaurs, and rebbachisauroid diplodocoids, which are now added to the already known dicraeosaurids and a recently published basal diplodocoid. These forms substantially increase the knowledge on the Early Cretaceous sauropod diversity in Gondwana. 相似文献