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991.
992.
Su Qing-Rui 《Solar physics》1990,127(1):139-147
Using a finite elements method, the magnetohydrostatic equation in a non-isothermal atmosphere is solved. The result is similar to the case in an isothermal atmosphere (Su, 1985). It is found that at some critical amount of shearing a magnetic island is formed and then breaks out to form an open magnetic configuration in which tearing-mode instability may occur. As the gradient of longitudinal magnetic field at some lower solar corona level increases, shearing loops containing strong currents are formed and the critical magnetic shearing parameter at which the magnetic island occurs, gets larger. In such a case, a lot of magnetic free energy is not easily released. It may be accumulated in a small volume above the polarity inversion line. As magnetic shearing increases, the magnetic free energy gets larger, until the magnetic shearing parameter reaches a higher critical value, a sudden change in magnetic configuration occurs. Such conditions may lead to high-energy solar eruptive phenomenon. 相似文献
993.
Results of our aerosol study, performed during 1983–1984 in Beijing, demonstrate that ambient carbonaceous aerosols are derived
mainly from coal combustion. Different SO2 oxidation processes have been observed in summer and winter. The winter sulfate appears to be produced locally and associated
with products of incomplete combustion. 相似文献
994.
The polarization is analyzed in four microwave bursts with one loop-top and two footpoint sources observed at 17 GHz with
the Nobeyama Radioheliograph (NoRH). The loop-like structure of the four events is confirmed by simultaneous SOHO/MDI magnetograms
and TRACE/EUV images or Yohkoh/SXT images. The heliocentric distance of the four events is greater than 30°. The three microwave sources in each given burst
are polarized in the same sense. This may be interpreted in terms of extraordinary mode emission, taking into account the
polarity of the underlying magnetic field and propagation effects, which may lead to inversion of the sense of polarization
in the limbward foot and loop-top source of the flaring loop. 相似文献
995.
996.
Cheng-Yue Su Yi-Ping Qin Jun-Hui Fan Zhang-Yu Han National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming Graduate School of Chinese Academy of Sciences Beijing Department of Physics Guangdong University of Technology Guangzhou Center for Astrophysics Guangzhou University Guangzhou Department of Mechanics University of Science Technology of China Hefei 《中国天文和天体物理学报》2006,6(3):323-330
We investigate the forming of gamma-ray burst pulses with a simple one-dimensional relativistic shock model. The mechanism is that a "central engine" drives forward the nearby plasma inside the fireball to generate a series of pressure waves. We give a relativistic geometric recurrence formula that connects the time when the pressure waves are produced and the time when the corresponding shocks occurred. This relation enables us to relate the pulse magnitude with the observation time. Our analysis shows that the evolution of the pressure waves leads to a fast rise and an exponential decay pulses. In determining the width of the pulses, the acceleration time is more important than that of the deceleration. 相似文献
997.
A statistical analysis of RHESSI X-ray flares in the 12–25 keV band during the period from February 2002 to June 2005 is presented.
We found that a power-law with an index of 1.80± 0.02 can fit well the frequency distribution of the peak count rates. This
power-law does not change significantly with time. However, the frequency distribution of the flare durations cannot be fitted
well by a single power-law. There is a weak correlation between the peak count rates and the characteristic times like rise
times, decay times, or durations. But the correlation between the rise times and decay times seems to be strong. We discuss
the results obtained and compare them with previous works. The frequency distribution of rise times for the sub-group events
with a similar magnitude of peak count rates is also shown. In particular, we propose a new parameter R
a
, the growth factor of the count rate, defined as the peak count rate divided by the rise time, to reflect the characteristics
of the rising phases of flares. The distribution of R
a
is shown and discussed. 相似文献
998.
An X17 class (GOES soft X-ray) two-ribbon solar flare on October 28, 2003 is analyzed in order to determine the relationship
between the timing of the impulsive phase of the flare and the magnetic shear change in the flaring region. EUV observations
made by the Transition Region and Coronal Explorer (TRACE) show a clear decrease in the shear of the flare footpoints during the flare. The shear change stopped in the middle
of the impulsive phase. The observations are interpreted in terms of the splitting of the sheared envelope field of the greatly
sheared core rope during the early phase of the flare. We have also investigated the temporal correlation between the EUV
emission from the brightenings observed by TRACE and the hard X-ray (HXR) emission (E > 150 keV) observed by the anticoincidence system (ACS) of the spectrometer SPI on board the ESA INTEGRAL satellite. The
correlation between these two emissions is very good, and the HXR sources (RHESSI) late in the flare are located within the
two EUV ribbons. These observations are favorable to the explanation that the EUV brightenings mainly result from direct bombardment
of the atmosphere by the energetic particles accelerated at the reconnection site, as does the HXR emission. However, if there
is a high temperature (T > 20 MK) HXR source close to the loop top, a contribution of thermal conduction to the EUV brightenings cannot be ruled out. 相似文献
999.
Mu Xinru Huang Jianping Li Zhenchun Liu Yanli Su Laiyuan Liu Junzhou 《Surveys in Geophysics》2022,43(3):737-773
Surveys in Geophysics - The propagation of seismic waves in attenuating and anisotropic earth media is accompanied by amplitude attenuation and phase distortion. If these adverse effects are not... 相似文献
1000.
Zhao Jiagang Li Shufeng Farnsworth Alexander Valdes Paul J. Reichgelt Tammo Chen Linlin Zhou Zhekun Su Tao 《中国科学:地球科学(英文版)》2022,65(7):1339-1352
Science China Earth Sciences - The growth of the Qinghai-Tibetan Plateau (QTP) during the Cenozoic drove dramatic climate and environmental change in this region. However, there has been limited... 相似文献