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排序方式: 共有1075条查询结果,搜索用时 15 毫秒
351.
Sin Chan Chou Andr de Arruda Lyra Jorge Lus Gomes Daniel Andrs Rodriguez Minella Alves Martins Nicole Costa Resende Priscila da Silva Tavares Claudine Pereira Dereczynski Isabel Lopes Pilotto Alessandro Marques Martins Lus Felipe Alves de Carvalho Jos Luiz Lima Onofre Idalcio Major Manuel Penhor Adrito Santana 《Climate Dynamics》2020,54(9):4021-4042
Sao Tome and Principe is a small insular African country extremely vulnerable to rising sea levels and impacts such as inundation, shore line change, and salt water intrusion into underground aquifers. Projections of climate change have considered coarse model resolutions. The objective of this work is to dynamically downscale the global model projections to 4-km resolution and to assess the climate change in the Sao Tome and Principe islands. The global climate projections are provided by the Canadian Earth System Model under two Representative Concentration Pathways greenhouse gas scenarios, RCP4.5 and RCP8.5. The downscaling is produced by the Eta regional climate model. The baseline period is taken between 1971 and 2000, and the future climate period is taken between 2041 and 2070. The 2-m temperature simulations show good agreement with station data. The model simulates temperature more accurately than precipitation. The precipitation simulations systematically show underestimation and delay of the rainy and the dry seasons by about 1 month, a feature inherited from the global climate model. In the middle of the 21st century, projections show the strongest warming in the elevated parts of the Sao Tome Island, especially in February under RCP8.5. Warmer nights and warmer days become more frequent in the islands when compared with those in the present. While under RCP4.5, precipitation increases in the islands; under RCP8.5, it decreases everywhere in both islands. Heavy precipitation rates should increase, especially in the south-southwestern parts of the Sao Tome islands. Detailed spatial variability of the temperature and precipitation changes in the islands can only be revealed at very high spatial model resolution. Implications for the potential energy production from two major river basins are assessed in this work. 相似文献
352.
353.
The polarisation of astrophysical source emission in the energy range from a few tens of keV up to the MeV region is an almost
unexplored field of high-energy astrophysics. Till date, polarimetry in astrophysics–in the energy domain from hard X-rays
up to soft γ-rays–has not been pursued due to the difficulties involved in obtaining sufficient sensitivity. Indeed for those
few instruments that are capable of performing this type of measurement (e.g. the COMPTEL instrument on the Compton Gamma-ray
Observatory and the IBIS instrument on INTEGRAL), polarimetry itself plays a secondary role in the mission objectives, as
the efficiencies (0.5% and 10% maximum, respectively) and polarimetric Q factors (0.1 and 0.3, respectively) are relatively limited. In order to perform efficient polarimetric measurements for hard
X-ray and soft gamma-ray sources, with an instrument of relatively robust and simple design, a CdTe based telescope (CIPHER:
Coded Imager and Polarimeter for High Energy Radiation) is under study. This instrument is based on a thick (10 mm) CdTe position-sensitive
spectrometer comprising four modules of 32 × 32 individual pixels, each with a surface area of 2 × 2 mm2 (about 160 cm2 total detection area). The polarimetric performance and design optimisation of the CIPHER detection surface have been studied
by use of a Monte Carlo code. This detector, due to its intrinsic geometry, can allow efficient polarimetric measurements
to be made between 100 keV and 1 MeV. In order to predict the polarimetric performance and to optimise the design and concept
of the CIPHER detection plane, a Monte Carlo code based on GEANT4 library modules was developed to simulate the detector behaviour
under a polarised photon flux. The Compton double event efficiency, as well bi-dimensional double event distribution maps
and the corresponding polarimetric modulation factor will be presented and discussed. Modulation Q factors better than 0.50 and double event total efficiencies greater than 10% were calculated in the energy range between
100 keV and 1 MeV. Herein we will present and discuss the general problems that affect polarimetric measurements in space,
such as the inclination of the source with respect to the telescope optical axis and background radiation. Q factor calculations for several beam inclinations as well as for background together with simulated astronomical sources
will be presented and discussed. 相似文献
354.
M. Favre P. Silva H. Chuaqui E. Wyndham P. Choi 《Astrophysics and Space Science》1997,256(1-2):485-490
We present preliminary time and space resolved studies of current sheath formation in Plasma Focus discharges, using a novel array of non-invasive magnetic field probes. The experiments are performed in a Mather type plasma focus, operating at 2 kV. The discharge is formed between a hollowed anode and six symmetrically arranged cathode rods. The array of small magnetic probes is located along the cathode rods. The probes are of millimeter size. They are shielded behind the rods, as to minimize capacitive coupling to the anode electrode, and allow non-perturbing measurements to be made. A simple analytical model of current sheath evolution is used to analyze the probe signals. The experiments have been performed in pure Hydrogen and Hydrogen with Argon mixture, at pressures from below 0.2 Torr upwards. The effect of the Argon mixture on the current sheath structure is investigated with the probe array. It is found that at constant mass density operation, the increase in the percentage of Argon results in a thinner sheath, with steeper current profile. 相似文献
355.
Robert G. Mann Seb Oliver Ruth Carballo Alberto Franceschini Michael Rowan-Robinson Alan F. Heavens Maria Kontizas David Elbaz Anastasios Dapergolas Evanghelos Kontizas Gian Luigi Granato Laura Silva Dimitra Rigopoulou J. Ignacio Gonzalez-Serrano Aprajita Verma Steve Serjeant reas Efstathiou Paul P. van der Werf 《Monthly notices of the Royal Astronomical Society》2002,332(3):549-574
356.
Laura Silva Gian Luigi Granato Alessandro Bressan Cedric Lacey Carlton M. Baugh Shaun Cole Carlos S. Frenk 《Astrophysics and Space Science》2001,276(2-4):1073-1078
We present the basic features and preliminary results of the interface between our spectrophotometric model GRASIL (which
calculates galactic SEDs from the UV to the submm with a detailed computation of dust extinction and thermal reemission) with
the semi-analytical galaxy formation model GALFORM (which computes galaxy formation and evolution in the hierarchical scenario,
providing the star formation history as an input to our model). With these two models we are able to synthesize simulated
samples of a few thousand galaxies for statistical studies of galaxy properties to investigate galaxy formation and evolution.
There is good agreement with the available SED and luminosity function data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
357.
358.
359.
The present work deals with the theory of oscillations with periods of about 3 min observed in the chromosphere above sunspot umbrae. The model of these oscillations (slow mode magneto-acoustic waves trapped in a chromospheric resonant cavity) provides an independent method of checking empirical models of the chromosphere above sunspots. Making use of this method, we investigate sunspot models which have been derived from spectroscopic data; the calculated periods of the oscillations fit well the observed periods. 相似文献
360.
P. G. Silva 《Geomorphology》2004,57(3-4):439-441