全文获取类型
收费全文 | 3919篇 |
免费 | 38篇 |
国内免费 | 60篇 |
专业分类
测绘学 | 43篇 |
大气科学 | 319篇 |
地球物理 | 659篇 |
地质学 | 1985篇 |
海洋学 | 346篇 |
天文学 | 476篇 |
综合类 | 64篇 |
自然地理 | 125篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 51篇 |
2021年 | 69篇 |
2020年 | 89篇 |
2019年 | 100篇 |
2018年 | 225篇 |
2017年 | 220篇 |
2016年 | 252篇 |
2015年 | 111篇 |
2014年 | 245篇 |
2013年 | 318篇 |
2012年 | 318篇 |
2011年 | 313篇 |
2010年 | 334篇 |
2009年 | 268篇 |
2008年 | 253篇 |
2007年 | 276篇 |
2006年 | 216篇 |
2005年 | 102篇 |
2004年 | 38篇 |
2003年 | 29篇 |
2002年 | 30篇 |
2001年 | 28篇 |
2000年 | 28篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 18篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1958年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有4017条查询结果,搜索用时 11 毫秒
181.
David P. Bacon Nash’at N. Ahmad Thomas J. Dunn Michael C. Monteith Ananthakrishna Sarma 《Natural Hazards》2008,44(3):317-327
By definition, a crisis is a situation that requires assistance to be managed. Hence, response to a crisis involves the merging
of local and non-local emergency response personnel. In this situation, it is critical that each participant: (1) know the
roles and responsibilities of each of the other participants; (2) know the capabilities of each of the participants; and (3)
have a common basis for action. For many types of natural disasters, this entails having a common operational picture of the unfolding events, including detailed information on the weather, both current and forecasted, that may impact on either
the emergency itself or on response activities. The Consequences Assessment Tool Set (CATS) is a comprehensive package of
hazard prediction models and casualty and damage assessment tools that provides a linkage between a modeled or observed effect
and the attendant consequences for populations, infrastructure, and resources, and, hence, provides the common operational
picture for emergency response. The Operational Multiscale Environment model with Grid Adaptivity (OMEGA) is an atmospheric
simulation system that links the latest methods in computational fluid dynamics and high-resolution gridding technologies
with numerical weather prediction to provide specific weather analysis and forecast capability that can be merged into the
geographic information system framework of CATS. This paper documents the problem of emergency response as an end-to-end system
and presents the integrated CATS–OMEGA system as a prototype of such a system that has been used successfully in a number
of different situations. 相似文献
182.
Y. N. Gnedin S. D. Buliga N. A. Silant’ev T. M. Natsvlishvili M. Y. Piotrovich 《Astrophysics and Space Science》2012,342(1):137-145
In this paper we demonstrate that the wavelength dependence of polarization degree and position angle allows us to derive the distribution of magnetic field in accretion disc. The polarized radiation arises due to scattering of emission light by electrons in a magnetized optically thick accretion disc. Faraday rotation of polarization plane is taken into consideration. Through wavelength dependence of polarization it is possible to derive the value of the magnetic Prandtl number in the accretion disc plasma. The power law index of the polarization wavelength dependence is related with the radial distribution of magnetic field in an accretion disc. This allows us to test the various models of an accretion disc around the central black hole. 相似文献
183.
Yu. A. Izrael V. M. Zakharov N. N. Petrov A. G. Ryaboshapko V. N. Ivanov A. V. Savchenko Yu. V. Andreev V. G. Eran’kov Yu. A. Puzov B. G. Danilyan V. P. Kulyapin V. A. Gulevskii 《Russian Meteorology and Hydrology》2009,34(10):635-638
The paper describes the results of the field experiment on studying solar radiation transmission in the visible wavelength range through model aerosol media formed in the lower troposphere with the help of generators installed aboard helicopters. The refractive index and the average size of the aerosol particles formed are close to those characteristic of the natural stratospheric aerosol. The composition of the equipment complex used to control aerosol optical and microphysical aerosol parameters is considered. The measurement results are in satisfactory agreement with the results of theoretical and experimental studies in simulation chambers. 相似文献
184.
Relationship between the velocity ellipsoids of galactic-disk stars and their ages and metallicities
The dependences of the velocity ellipsoids of F-G stars of the thin disk of the Galaxy on their ages and metallicities are
analyzed based on the new version of the Geneva-Copenhagen Catalog. The age dependences of the major, middle, and minor axes
of the ellipsoids, and also of the dispersion of the total residual velocity, obey power laws with indices 0.25, 0.29, 0.32,
and 0.27 (with uncertainties ±0.02). Due to the presence of thick-disk objects, the analogous indices for all nearby stars
are about a factor of 1.5 larger. Attempts to explain such values are usually based on modeling relaxation processes in the
Galactic disk. Elimination of stars in the most numerous moving groups from the sample slightly reduces the corresponding
indices (0.22, 0.26, 0.27, and 0.24). Limiting the sample to stars within 60 pc of the Sun, so that the sample can be considered
to be complete, leaves both the velocity ellipsoids and their age dependences virtually unchanged. With increasing age, the
velocity ellipsoid increases in size and becomes appreciablymore spherical, turns toward the direction of the Galactic center,
and loses angular momentum. The shape of the velocity ellipsoid remains far from equilibrium. With increasing metallicity,
the velocity ellipsoid for stars of mixed age increases in size, displays a weak tendency to become more spherical, and turns
toward the direction of the Galactic center (with these changes occurring substantially more rapidly in the transition through
the metallicity [Fe/H]≈−0.25). Thus, the ellipsoid changes similarly to the way it does with age; however, with decreasing
metallicity, the rotational velocity about the Galactic center monotonically increases, rather than decreases (!). Moreover,
the power-law indices for the age dependences of the axes depend on the metallicity, and display a maximum near [Fe/H] ≈−0.1.
The age dependences of all the velocity-ellipsoid parameters for stars with equal metallicity are roughly the same. It is
proposed that the appearance of a metallicity dependence of the velocity ellipsoids for thin-disk stars, recorded from the
close to the Sun, is most likely due to the radial migration of stars. 相似文献
185.
Mouhamadou Bamba Sylla E. Coppola L. Mariotti F. Giorgi P. M. Ruti A. Dell’Aquila X. Bi 《Climate Dynamics》2010,35(1):231-247
This study examines the ability of the latest version of the International Centre for Theoretical Physics (ICTP) regional
climate model (RegCM3) to reproduce seasonal mean climatologies, annual cycle and interannual variability over the entire
African continent and different climate subregions. The new European Center for Medium Range Weather Forecast (ECMWF) ERA-interim
reanalysis is used to provide initial and lateral boundary conditions for the RegCM3 simulation. Seasonal mean values of zonal
wind profile, temperature, precipitation and associated low level circulations are shown to be realistically simulated, although
the regional model still shows some deficiencies. The West Africa monsoon flow is somewhat overestimated and the Africa Easterly
Jet (AEJ) core intensity is underestimated. Despite these biases, there is a marked improvement in these simulated model variables
compared to previous applications of this model over Africa. The mean annual cycle of precipitation, including single and
multiple rainy seasons, is well captured over most African subregions, in some cases even improving the quality of the ERA-interim
reanalysis. Similarly, the observed precipitation interannual variability is well reproduced by the regional model over most
regions, mostly following, and sometimes improving, the quality of the ERA-interim reanalysis. It is assessed that the performance
of this model over the entire African domain is of sufficient quality for application to the study of climate change and climate
variability over the African continent. 相似文献
186.
During the 50th cruise of R/V Akademik Mstislav Keldysh, on the south slope of the Atlantis massif (30°07′N; the Middle Atlantic Ridge), an inactive hydrothermal field named the
Lost Village was discovered. This new field was formed of light carbonate rock and was located near the active Lost City hydrothermal
field. The mineralogical associations of these fields were studied. A conclusion about the participation the ocean water in
the changing of the carbonate composition of the inactive hydrothermal field was reached. 相似文献
187.
A study of variations in the critical frequency of the F2 layer (foF2) prior to a shallow-focus eartquake with a magnitude M = 5.1 which occurred in Spain on May 11, 2011, is carried out. The obtained results show that a positive disturbance in the foF2 value was observed at the ionospheric Del’ebre station, which is the closest to the earthquake epicenter. At the same time, no disturbances in foF2 are revealed at ionospheric stations located at a greater distance from the epicenter. This fact makes it possible to conclude that the positive disturbance in the F2 layer observed at the Del’ebre station could have a sesmogenic nature. 相似文献
188.
N. R. Ikhsanov V. Y. Kim N. G. Beskrovnaya L. A. Pustil’nik 《Astrophysics and Space Science》2013,346(1):105-109
The point X-ray source 1E 161348-5055 is observed to display pulsations with the period 6.67?hr and $|\dot{P}| \leq1.6 \times10^{-9}\,{\rm s\,s^{-1}}$ . It is associated with the supernova remnant RCW?103 and is widely believed to be a ~2000?yr old neutron star. Observations give no evidence for the star to be a member of a binary system. Nevertheless, it resembles an accretion-powered pulsar with the magnetospheric radius ~3000?km and the mass-accretion rate $\sim 10^{14}\,{\rm g\,s^{-1}}$ . This situation could be described in terms of accretion from a (residual) fossil disk established from the material falling back towards the star after its birth. However, current fall-back accretion scenarios encounter major difficulties explaining an extremely long spin period of the young neutron star. We show that the problems can be avoided if the accreting material is magnetized. The star in this case is surrounded by a fossil magnetic slab in which the material is confined by the magnetic field of the accretion flow itself. We find that the surface magnetic field of the neutron star within this scenario is ~1012?G and that a presence of $\gtrsim10^{-7}\,{\rm M_{\odot}}$ magnetic slab would be sufficient to explain the origin and current state of the pulsar. 相似文献
189.
M. I. Kuz’min Yu. P. Troshin S. M. Boiko E. A. Razvozzhaeva L. D. Zorina D. Kh. Martikhaeva 《Geology of Ore Deposits》2010,52(3):252-259
The carbonaceous matter filling cavities in sulfide-quartz veins at the Kurultyken hydrothermal base-metal deposit in the
Khapcheranga ore district, Transbaikal region, was studied using chromatography/mass spectrometry, X-ray diffraction, thermal
and isotopic analyses, and IR spectroscopy. It was established that carbonaceous matter was a maltha composed of polycyclic
aromatic hydrocarbons (PAHs). Chrysene, pyrene, and benzpyrelene identified among PAHs are evidence for the hydrothermal origin
of the initial carbonaceous matter of maltha. The main mass of carbonaceous matter was synthesized under reductive conditions
and at a low temperature, i.e., at the final stage of base-metal ore formation. Nevertheless, the thermometric data indicate
that part of the carbonic compounds could have formed at 480°C, i.e., at the high-temperature stage of the postmagmatic process.
The contribution of host rocks as a source of carbonaceous matter was minimal. 相似文献
190.