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651.
652.
653.
E. B. Sal’nikova A. M. Larin S. Z. Yakovleva A. B. Kotov V. A. Glebovitskii A. V. Tkachev I. V. Anisimova Yu. V. Plotkina B. M. Gorokhovskii 《Doklady Earth Sciences》2011,441(1):1479-1483
The U-Pb age of the manganotantalite from rare-metal pegmatites of the Vishnyakovskoe deposit (East Sayan Belt) has been assessed
at 1838 ± 3 Ma. The acquired data indicate the pegmatites of this deposit and associated granites of the Sayan complex belong
to the postcollision South Siberian igneous belt (1.88–1.84 Ga), which stretches along the southwestern frame of the Siberian
Craton by more than 2500 km, from the Yenisei Ridge to the Aldan Shield. Formation of this igneous belt is related to joining
(starting from about 1.9 Ga BP) of the series of continental microplates and island arcs to the Siberian Craton; this led
to final stabilization of the craton at about 1.8 Ga BP. 相似文献
654.
The ion composition of fluxes of charged particles in interplanetary space with energies ∼0.03–10 MeV/nucleon are studied
during quiet periods in the 23rd solar-activity cycle using data from the ACE spacecraft. Apart from the activity minimum,
the Fe/O ratio during such periods corresponds to either the relative abundances of ions in particle fluxes accelerated in
solar flares or the mean abundances of elements in the solar corona. At the cycle minimum, this ratio takes on values characteristic
for the solar wind. These results indicate that the background fluxes of low-energy particles in the phases of the growth,
maximum, and decay of the solar cycle include significant contributions from both coronal particles accelerated to suprathermal
energies and particles accelerated in small impulsive solar flares. The particle fluxes from such flares are distinguished
by an enhanced abundance of iron ions. 相似文献
655.
656.
A. M. Zubareva E. P. Pavlenko M. V. Andreev S. V. Antipin N. N. Samus’ A. V. Sergeev 《Astronomy Reports》2011,55(3):224-229
We have obtained data on various brightness states of the polar MT Dra over five years of observations, including the first
multicolor photometry for this close binary. We confirm the known orbital period, which has remained constant over 17 years,
which is unusual for cataclysmic binaries. Our observations in October 2006 demonstrated a transition of the polar to its
low brightness state within one day. 相似文献
657.
HST trigonometric distances, photometric metallicities, isochronic ages from the second revised version of the Geneva-Copenhagen
survey, and uniform spectroscopic Fe and Mg abundances from our master catalog are used to construct and analyze the age-metallicity
and age-relative Mg abundance relations for stars of the thin disk. The influences of selection effects are discussed in detail.
It is demonstrated that the radial migration of stars does not lead to appreciable distortions in the age dependence of the
metallicity. During the first several billion years of the formation of the thin disk, the interstellarmaterial in this disk
was, on average, fairly rich in heavy elements (〈[Fe/H]〉 ≈ −0.2) and poorly mixed. However, the metallicity dispersion continuously
decreased with age, from σ
[Fe/H] ≈ 0.22 to ≈0.13. All this time, the mean relative abundance of Mg was somewhat higher than the solar value (〈[Mg/Fe]〉 ≈ 0.1).
Roughly four to five billion years ago, the mean metallicity began to systematically increase, while retaining the same dispersion;
the mean relative Mg abundance began to decrease immediately following this. The number of stars in this subsystem increased
sharply at the same time. These properties suggest that the star-formation rate was low in the initial stage of formation
of the thin disk, but abruptly increased about four to five billion years ago. 相似文献
658.
Observations at 44 GHz in the 70−61
A
+ methanol line have been carried out on the 20-m telescope of the Onsala Space Observatory (Sweden) in the directions of the
poorly studied region G27.4–0.2 and of several supernova remnants, at the coordinates of the OH(1720) maser satellite emission,
with the aim of searching for Class I methanol maser emission in these sources. The region G27.4–0.2 has beenmapped, and contains
maser sources and two supernova remnants with similar coordinates and radial velocities, which may accelerate condensation
of the ambient gas-dust medium. This may play a role in enhancing the probability of methanol formation and maser emission.
This is the first detection of 44 GHz maser emission in this source, and this maser is among the 10% of the strongest Class
I methanol masers, within the uncertainties in the integrated flux (of a total of 198 currently knownmasers). A 27′ × 27′
region around the maser has been mapped at 44 GHz in steps of 1′. The 44-GHz emission forms only within the previously known
maser region. Further studies in water lines are needed to estimate the influence of shocks from supernovae. No 44-GHz Class
I methanol maser emission was detected at the 3σ level at the coordinates of the OH(1720) satellite emission in six supernova remnants; i.e., the presence of OH(1720) emission
is not a sufficient condition for the detection of Class I methanol masers. 相似文献
659.
G. A. Shul’man 《Astronomy Reports》2011,55(8):718-723
The quantum motion of non-relativistic and relativistic electrons in the presence of constant magnetic fields at the surfaces of magnetic stars, magnetic white dwarfs, and pulsars is considered. The quantizing magnetic-field strengths for charged particles with specified energies are determined. The quantum motion of these particles in a plane perpendicular to the magnetic field is accompanied by spontaneous radiation due to electron transitions from higher to lower discrete energy levels, right down to the ground state. In the non-relativistic case, this emission is monochromatic. In the non-relativistic case, various frequencies are emitted, but lie within an order of magnitude of each other. The electron kinetic energy along the magnetic field varies from zero to a maximum value, due to the one-dimensional character of the motion along the field, between each pair of potential barriers corresponding to the discrete energy levels. The results may be relevant to describing gamma-ray flares of pulsars. 相似文献
660.
A. V. Volkov N. E. Savva A. A. Sidorov V. Yu. Prokof’ev N. A. Goryachev S. D. Voznesensky A. V. Al’shevsky A. D. Chernova 《Geology of Ore Deposits》2011,53(1):1-26
The Shkol’noe deposit is localized in a small granitoid stock, the root portion of which is traced using geophysical data
to a depth of 5–8 km. The high-grade gold ore (33 gpt Au) is enriched in silver and principally differs in ore composition
from the previously studied mesothermal gold-quartz and epithermal gold-silver deposits in the Russian Northeast. The main
reserves of the Shkol’noe deposit concentrate in bonanzas (20% of the total volume of orebodies). The internal deformation
is related to the rearrangement of matter in freibergite; exsolution structures in fahlore and native gold are related to
postmineral metamorphism. It is suggested that the ore of the Shkol’noe deposit occupies a transitional position between porphyrytype
and epithermal levels of ore deposition. 相似文献