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621.
V. O. Mokievsky L. V. Vorobjeva L. A. Garlitska M. A. Miljutina N. V. Kucheruk 《Oceanology》2010,50(6):945-952
The results of meiobenthic surveys undertaken in 1991, 1999, and 2005 off the Caucasian coasts of the Black Sea are presented.
During the period of 1991 to 1999, the number of free-living nematodes increased significantly at all the sampling stations.
The mean nematode abundance values grew from 85 ind./10 cm2 in 1991 to 1167 ind./10 cm2 in 1999. Proportionally, the total metazoan meiofauna density increased from 171 to 1283 ind./10 cm2. The abundance of other meiofaunal groups including harpacticoid copepods did not change significantly. As a result of these
changes, the ratio of nematodes to copepods (the nematodes-copepods index) increased from 2.5: 1 in 1991 to 26: 1 in 1999
and to 70: 1 in 2005. The number of foraminifers increased twofold. In 1991, they were found only at five stations out of
25. In 1999, foraminifers were presented at all ten stations with a mean density of 212 ind./10 cm2. Such changes in the meiobenthic communities could have resulted from cascade transformations of the ecosystem leading to
among other changes to a decline in the macrobenthos biomass and the release of nonutilized organic matter in the bottom ecosystems.
The differences in the procedures of the sampling and the samples’ processing in the different years may be responsible for
the 20–30% variation in the assessment of the meiobenthos’ number. 相似文献
622.
S. N. Kulichkov I. P. Chunchuzov O. I. Popov 《Izvestiya Atmospheric and Oceanic Physics》2010,46(1):60-68
The results of simulating the influence of an atmospheric fine structure on the characteristics of acoustic signals propagating
throughout the atmosphere for long distances from their sources are presented. A numerical model of an atmospheric fine inhomogeneous
structure within the height range z = 20…120 km is proposed to perform calculations. This model and its numerical parameters are based on the current notions
of the formation of an atmospheric fine structure due to internal gravity waves. The numerical calculations were performed
using the parabolic-equation method. A spatial structure of the acoustic field and the structure of an acoustic signal at
long distances from a pulsed source were calculated. It is shown that the presence of an atmospheric fine structure results
in a scattering of acoustic signals and their recording in the geometric shadow region. The results of calculations of signal
forms are in a satisfactory agreement with data on signals recorded in the geometric shadow region which is formed at a distance
of about 300 km from an experimental explosion. 相似文献
623.
A. G. Zatsepin E. G. Morozov V. T. Paka A. N. Demidov A. A. Kondrashov A. O. Korzh V. V. Kremenetskiy S. G. Poyarkov D. M. Soloviev 《Oceanology》2010,50(5):643-656
During cruise 54 of the R/V Akademik Mstislav Keldysh to the southwestern Kara Sea (September 6 to October 7, 2007), a large amount of hydrophysical data with unique spatial resolution
was obtained on the basis of measurements using different instruments. The analysis of the data gave us the possibility to
study the dynamics and hydrological structure of the southwestern Kara Sea basin. The main elements of the general circulation
are the following: the Yamal Current, the Eastern Novaya Zemlya Current, and the St. Anna Trough Current. All these currents
are topographically controlled; they flow over the bottom slopes along the isobaths. The Yamal Current begins at the Kara
Gates Strait and turns to the east as part of the cyclonic circulation. Then, it turns to the north and propagates along the
Yamal coast over the 100-m isobath. The Eastern Novaya Zemlya Current (its core is located over the eastern slope of the Novaya
Zemlya Trough) flows to the northeast. Near the northern edge of Novaya Zemlya, it encounters the St. Anna Trough Current,
separates from the coast, and flows practically to the east merging with the continuation of the Yamal Current. A strong frontal
zone is formed in the region where the two currents merge above the threshold that separates the St. Anna Trough from the
Novaya Zemlya Trough and divides the warm and saline Arctic waters from the cooler and fresher waters of the southwestern
part of the Kara Sea. This threshold, whose depth does not exceed 100–150 m, is a barrier that prevents the spreading of the
Barents Sea and Arctic waters to the southwestern part of the Kara Sea basin through the St. Anna Trough. 相似文献
624.
Importance of wave-induced bed liquefaction in the fine sediment budget of Cleveland Bay,Great Barrier Reef 总被引:3,自引:0,他引:3
J. Lambrechts C. Humphrey L. McKinna O. Gourge K.E. Fabricius A.J. Mehta S. Lewis E. Wolanski 《Estuarine, Coastal and Shelf Science》2010
Data from a three-year long field study of fine sediment dynamics in Cleveland Bay show that wave-induced liquefaction of the fine sediment bed on the seafloor in shallow water was the main process causing bed erosion under small waves during tradewinds, and that shear-induced erosion prevailed during cyclonic conditions. These data were used to verify a model of fine sediment dynamics that calculates sediment resuspension by both excess shear stress and wave-induced liquefaction of the bed. For present land-use conditions, the amount of riverine sediments settling on the bay may exceed by 50–75% the amount of sediment exported from the bay. Sediment is thus accumulating in the bay on an annual basis, which in turn may degrade the fringing coral reefs. For those years when a tropical cyclone impacted the bay there may be a net sediment outflow from the bay. During the dry, tradewind season, fine sediment was progressively winnowed out of the shallow, reefal waters. 相似文献
625.
Sediment processes in estuaries are controlled by the interaction of factors that include tides, fresh water inputs, bed morphology, sediment supply, and hydrodynamics. The interaction of these factors strongly influences the pattern of sediment deposition. The ability to quantify sediment deposition on a regional scale will improve the understanding of the underlying processes, and provide valuable information for managing estuarine systems. This paper describes our approach for obtaining the deposition pattern and quantifying the amount of 20th century impacted sediments in the Haverstraw Bay section of the Hudson River Estuary. Through the combination of high-resolution seismic data and rapidly acquired geochemical information from numerous sediment cores, we estimate that our study site experiences an average sediment accumulation rate of ∼3 mm/y and that ∼75,000 t/y or ∼10% of the annual total sediment input measured at the Poughkeepsie, NY gauging station (USGS) is stored in this reach of the Hudson River on ∼100 y timescales. A detailed analysis of the depositional pattern indicates that the accumulation rate varies considerably throughout the study area ranging from non-depositional to >8 mm/y. Our data also clearly indicate that the dredged channel in Haverstraw Bay is currently the main focus of deposition in this area. 相似文献
626.
The hydrodynamic performance of a vertical wall with permeable lower part (horizontal slots) was experimentally and theoretically studied under normal regular waves. The effect of different wave and structural parameters was investigated e.g. the wave length, the upper part draft, and the lower part porosity. Also, the theoretical model based on an Eigen Function Expansion Method and a Least Square Technique was developed. In order to examine the validity of the theoretical model, the theoretical results were compared with the present experimental results and with the results obtained from different previous studies. Comparison between experiments and predictions showed that the theoretical model provides a good estimate of the wave transmission, reflection, and energy dissipation coefficients when the friction factor f = 5.5. In general, the tested model gives transmission coefficients less than 0.5 and reflection coefficients larger than 0.5 when the relative wave length h/L is larger than 0.3, the relative upper part draft D/h larger than 0.36, and lower part porosity ε less than 0.5. Also, the tested model dissipates about 50% of the incident wave energy when the relative wave length h/L is in the range of 0.25 to 0.35. 相似文献
627.
V. I. Man’kovskii G. A. Tolkachenko E. B. Shibanov O. V. Martynov E. N. Korchemkina D. V. Yakovleva I. A. Kalinskii 《Physical Oceanography》2010,20(3):207-230
We present the results of measurements of optical characteristics of waters (the beam attenuation coefficient, volume scattering
function, sea water reflectance, and Secchi depth) and optical characteristics of the atmosphere (aerosol optical thickness,
content of vapors, and the ?ngstr?m exponent) carried out in September 2008 on the oceanographic platform near Katsiveli.
We carried out the comparative analysis of hydrooptical characteristics measured in various years. The optical type of sea
waters in the period of observations is determined. 相似文献
628.
629.
Based on photographic and CCD observations with the Pulkovo 26-inch refractor, radial velocity measurements with the 1.5-m RTT-150 telescope (TUBITAK National Observatory, Turkey), and highly accurate observations published in the WDS catalog, we have obtained the orbits of ten wide visual double stars by the apparent motion parameter method. The orientation of the orbits in the Galactic coordinate system has been determined. For the outer pair of the multiple star HIP 12780 we have calculated a family of orbits with a minimum period P = 4634 yr. Two equivalent solutions with the same period have been obtained for the stars HIP 50 (P = 949 yr) and HIP 66195 (P = 3237 yr). We have unambiguously determined the orbits of six stars: HIP 12777 (P = 3327 yr), HIP 15058 (P = 420 yr), HIP 33287 (P = 1090 yr), HIP 48429 (P = 1066 yr), HIP 69751 (P = 957 yr), and HIP 73846 (P = 1348 yr). The orbit of HIP 55068 is orientated perpendicularly to the plane of the sky, P >1000 yr. The star HIP 48429 is suspected to have an invisible companion. 相似文献
630.
We suggest a method and build a model of radio galaxy distribution over the sphere using data from the WENSS catalogs and standard radio count models by Condon. We calculate the angular power spectrum of the contribution of extended radio galaxies into the microwave background and show that it can be a distorting factor for correct estimation of the angular spectrum from the signal determined by the Sunyaev–Zeldovich effect. 相似文献