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801.
M. Arockiasamy H. El-Tahan A.S.J. Swamidas W.E. Russell D.V. Reddy 《Ocean Engineering》1984,11(5):463-490
The paper presents an analytical and experimental study on the transient response of semisubmersibles to bergybit impact and the strength of bergybit ice to high strain-rate loadings. Two approaches have been proposed for the solution of the semisubmersible-bergybit interaction problem, one using the energy approach and the other using the conventional structural dynamics approach with initial velocity conditions. In addition the local behaviour of the impacted regions have been analysed for deformation and failure. Numerical results have been given for local behaviour of an impacted column and global behaviour of semisubmersible-bergybit system. Experimental study has been reported on the impact strength of iceberg ice at strain rates of 10−3, 10−2 and 10−1; the indentation impact strength of ice is found to be 3–4 times the unaixial compressive strength, at the same strain rate. 相似文献
802.
A. S. Drofa V. G. Eran’kov V. N. Ivanov A. G. Shilin G. F. Iskevich 《Izvestiya Atmospheric and Oceanic Physics》2013,49(3):298-306
The results of experimental investigations into the action of polydispersion salt powders on model cloud media are presented. The results of experiments show a considerable positive effect of the modification of convective clouds by salt powders in order to obtain additional precipitation. The introduction of polydispersion salt powder into a forming cloud medium leads to the appearance of large cloud droplets and to the droplet-spectrum broadening. This result is a positive factor for the stimulation of coagulation processes and further precipitation formation. No “overseeding” phenomenon (when, instead of the enlargement of droplets, their sizes decrease and the concentration of cloud droplets increases) is observed at rather high mass concentrations of the introduced powder. 相似文献
803.
A conceptual variant for constructing a computer database for the theory of wave processes in the World's Ocean is suggested.
Five basic model components have been singled out, namely, acoustic waves, surface waves, internal waves, gyroscopic waves,
and Rossby waves. The structure of each block is described. The main principle of organizing the databank consists in dividing
the entire variety of wave processes into categories and in generating a hierarchical system of models for each, category,
using the principle of transition from general to partial.
Translated by Vladimir A. Puchkin. 相似文献
804.
S. F. Dotsenko 《Physical Oceanography》1998,9(4):249-258
The paper analyses the transformation of tsunami-type solitary waves, propagating from the abyssal part of the Black Sea towards
its shelf zone. The study is performed by solving numerically unidimensional non-linear equations for non-dispersive long
waves, using the finite-difference slope and shelf, with the full wave reflection prescribed at a 10 m depth contour. The
non-linearity of the process is shown to throughly impact the reflection of waves by the shore and the shape of the reflected
wave. Tsunami wave heights have been seen to increase by several times in the Black sea shelf area.
Translated by Vladimir A. Puchkin. 相似文献
805.
On the southwestern Barents Sea shelf, sediments containing gas hydrates that overlie free gas have been inferred from multichannel
seismic data. The volume of suspected gas hydrate is tentatively estimated to about 1.9×108 m3. The gas hydrate zone probably formed from thermogenic gas leaking from a deeper source. The hydrate zone may have thickened
during the Neogene by including gas originally trapped as free gas below the hydrate following a significant downward migration
of the isotherms caused by erosion and/or subsidence. Within the present oceanographic conditions, gas hydrate is suspected
to be stable or slowly decomposing.
Received: 20 December 1996 / Revision received: 20 August 1997 相似文献
806.
This study experimentally investigates the nonlinear response stability and transition behaviour of a submerged, moored ocean structural system which consists of a spherical buoy and attached multi-point mooring lines. The system is excited by a periodic wave field in a closed channel. System nonlinearities include complex geometric restoring (stiffness) force and coupled fluid-system interaction exciting forces. Experimental set-up, operating procedures and analysis of the measured results are presented. Characteristic motions observed include harmonic, subharmonic and ultraharmonic responses, which demonstrate a signature of the intricate pattern of the nonlinear global behaviour. Good agreements between the measured and most predicted responses are demonstrated in both time and frequency domains. These results confirm the validity of the analytical model presented and calibrate the accuracy of the existing numerical predictions. Primary and secondary resonances in the response are identified via frequency response curves. Response bifurcation cascades are observed in the experimental results and the possible existence of higher-order nonlinear responses is inferred. 相似文献
807.
In this paper the probability of green water occurrence is investigated by taking into account the threshold of the vertical relative motion exceeding the freeboard. The number of wetting of the unit/vessel is predicted using probabilistic method. This paper compares the significant load, due to shipping of green water with the works of other researchers, and the loads are found to be close with the results presented in this paper. There is no direct relation between the velocities in the waves and the water velocity over the deck. The water velocities around the bow are heavily distributed by the presence of the bow. This scenario makes the flow very complex for schematic modelling. 相似文献
808.
M. S. Barash 《Oceanology》2012,52(2):238-248
At the end of the Permian, at the boundary between the Paleozoic and Mesozoic (251.0 ± 0.4 Ma), the largest mass extinction
of organisms on the Earth occurred. Up to 96% of the species of marine invertebrates and ∼70% of the terrestrial vertebrates
died off. A lot of factors were suggested and substantiated to explain this mass mortality, such as the disappearance of environmental
niches in the course of the amalgamation of the continental plates into Pangea, sea level fluctuations, anoxia, an elevated
CO2 content, H2S intoxication, volcanism, methane discharge from gas-hydrates, climate changes, impact events (collisions with large asteroids),
or combinations of many of these reasons. Some of these factors are in subordination to others, while others are independent.
Almost all of these factors developed relatively slowly and could not cause the sudden mass mortality of organisms globally.
It could have happened when large asteroids, whose craters have been discovered lately, fell to the Earth. It is suggested
that the impact events “finished off” the already suppressed biota. A simultaneous change in many of the factors responsible
for the biodiversity, including those not connected in a cause-and-effect relationship, proves the existence of a common extrater-restrial
cause that affected both the changes in the internal and external geospheres and the activation of asteroid attacks (the Sun’s
transit of spiral arms of our galaxy, the Sun’s oscillations perpendicularly to the galactic plane, etc). 相似文献
809.
A. I. Ryabinin S. A. Bobrova L. V. Saltykova E. A. Danilova 《Physical Oceanography》2012,21(5):320-328
We study the space-and-time variations of the delivery of fluxes of 26 elements (Na, K, Rb, Cs, Cu, Ag, Au, Ca, Sr, Ba, Zn,
Cd, Hg, Hf, Ta, As, Sb, Cr, Se, Mo, W, Mn, Br, Fe, Co and Ni) with atmospheric precipitations to the sea surface in the regions
of Sevastopol and the South Coast of Crimea. It is established A series of general regularities of the delivery of the sum
of these elements and their soluble and insoluble forms. We also give the characteristics of their space-time variability. 相似文献
810.
A. S. Zapevalov 《Izvestiya Atmospheric and Oceanic Physics》2012,48(2):200-206
We assess the influence of changes in the skewness and kurtosis of the distribution of elevations on a rough sea surface that
were observed in field conditions on the accuracy of the recovery of the sea-surface level along the satellite trace. For
different values of a significant height of surface waves, we obtain numerical estimates for the bias in relief recovery due
to the simultaneous variation in skewness and kurtosis. It is shown that, with a decrease in kurtosis, the effect of skewness
changes on the accuracy of altimetry measurements of the level increases. We note the limitations of the Gram-Charlier model
in simulating the radar waveforms return from the sea surface. 相似文献