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51.
52.
Interannual variability in Nordic seas primary production 总被引:1,自引:0,他引:1
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57.
ENSO variability and the eastern tropical Pacific: A review 总被引:3,自引:0,他引:3
El Niño-Southern Oscillation (ENSO) encompasses variability in both the eastern and western tropical Pacific. During the warm phase of ENSO, the eastern tropical Pacific is characterized by equatorial positive sea surface temperature (SST) and negative sea level pressure (SLP) anomalies, while the western tropical Pacific is marked by off-equatorial negative SST and positive SLP anomalies. Corresponding to this distribution are equatorial westerly wind anomalies in the central Pacific and equatorial easterly wind anomalies in the far western Pacific. Occurrence of ENSO has been explained as either a self-sustained, naturally oscillatory mode of the coupled ocean–atmosphere system or a stable mode triggered by stochastic forcing. Whatever the case, ENSO involves the positive ocean–atmosphere feedback hypothesized by Bjerknes. After an El Niño reaches its mature phase, negative feedbacks are required to terminate growth of the mature El Niño anomalies in the central and eastern Pacific. Four requisite negative feedbacks have been proposed: reflected Kelvin waves at the ocean western boundary, a discharge process due to Sverdrup transport, western Pacific wind-forced Kelvin waves, and anomalous zonal advections. These negative feedbacks may work together for terminating El Niño, with their relative importance being time-dependent.ENSO variability is most pronounced along the equator and the coast of Ecuador and Peru. However, the eastern tropical Pacific also includes a warm pool north of the equator where important variability occurs. Seasonally, ocean advection seems to play an important role for SST variations of the eastern Pacific warm pool. Interannual variability in the eastern Pacific warm pool may be largely due to a direct oceanic connection with the ENSO variability at the equator. Variations in temperature, stratification, insolation, and productivity associated with ENSO have implications for phytoplankton productivity and for fish, birds, and other organisms in the region. Long-term changes in ENSO variability may be occurring and are briefly discussed. This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific. 相似文献
58.
Carbon balance in a salt marsh: Interactions of diffusive export, tidal deposition and rainfall-caused erosion 总被引:1,自引:0,他引:1
Alice G. Chalmers Richard G. Wiegert Paul L. Wolf 《Estuarine, Coastal and Shelf Science》1985,21(6):757-771
Studies of the concentrations of particulate and dissolved organic carbon in the Duplin River, of the tidal exchange of POC and DOC in the marsh, of the standing stock and movement of Spartina alterniflora wrack in the Duplin, and of the removal of carbon from the surface of the marsh by rain were conducted at Sapelo Island, Georgia in order to test three hypotheses about export of carbon from the Duplin River watershed. We found that the gradients in POC and DOC concentrations are such that carbon is being transported down the Duplin River throughout the year, although in smaller quantities than previously believed. In contrast, almost all tidal exchanges within the marsh result in deposition of carbon. Most of this deposited carbon is subsequently eroded as a result of rain falling on the exposed marsh surface, and is washed back into the tidal creeks. This cycle of deposition and erosion is a possible mechanism keeping POC in the thin aerobic surface layer of the marsh, thus increasing its availability to detritivores and aerobic microbes. The standing stock of wrack is only a fraction of the S. alterniflora produced each year, and its export is a negligible term in the carbon balance equation. 相似文献
59.
Positive gravity anomalies indicate two dense conduits or eruptive centers beneath the northern summit of Sio Guyot, western Mid-Pacific Mountains. The low amplitude of the positive anomalies and the gravity lows flanking the guyot can be explained by crust 2.5 times the normal Pacific Ocean crustal thickness extending to a depth of 22 ± 2 km. The excess mass of the seamount is 100% locally isostatically compensated by the mass deficit below; this compensation may result from flexural loading and voluminous sill injection near a former ridge-crest transform fault system trending roughly ENE and NNW. 相似文献
60.
Paul Weimer 《Geo-Marine Letters》1989,9(4):185-272
The Mississippi Fan is a large, mud-dominated submarine fan over 4 km thick, deposited in the deep Gulf of Mexico during the
late Pliocene and Pleistocene. Analysis of 19,000 km of multifold seismic data defined 17 seismic sequences, each characterized
by channel, levee, and associated overbank deposits, as well as mass transport deposits. At the base of nine sequences are
a series of seismic facies consisting of mounded, hummocky, chaotic, and subparallel reflections, which constitute 10–20%
of the sediments in each the sequences. These facies are externally mounded and occur in two general regions of the fan: (1)
in the upper and middle fan they are elongate in shape and mimic the channel's distribution; (2) in the middle fan to lower
fan they are characterized by a fan-shaped distribution, increasing in width downfan. These facies are interpreted to have
formed as disorganized slides, debris flows, and turbidites (informally called “mass transport complexes”).
Overlying this basal interval, characteristic of all sequences, are well-developed channel-levee systems that constitute 80–90%
of the fan's sediments. Channels consist of high amplitude, subparallel reflections, whereas the flanking levee sediments
appear as subparallel reflections that have high amplitudes at the base changing upward to low amplitude. The vertical change
in amplitude may reflect a decrease in grain size and bed thicknesses. Overbank sediments are characterized by interbedded
subparallel to hummocky and mounded reflections, suggesting both turbidites from the channel, as well as slides and debris
flows derived both locally and from the slope updip. 相似文献