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61.
62.
Diego F. Torres Shu Zhang Olaf Reimer Xavier Barcons Amalia Corral Valentí Bosch-Ramon Josep M. Paredes Gustavo E. Romero Jin Qu Werner Collmar Volker Schönfelder Yousaf Butt 《Astrophysics and Space Science》2007,309(1-4):17-21
The COMPTEL unidentified source GRO J 1411-64 was observed by INTEGRAL and XMM-Newton in 2005. The Circinus Galaxy is the
only source detected within the 4σ location error of GRO J1411-64, but in here excluded as the possible counterpart. At soft X-rays, 22 reliable and statistically
significant sources (likelihood >10) were extracted and analyzed from XMM-Newton data. Only one of these sources, XMMU J141255.6-635932,
is spectrally compatible with GRO J1411-64 although the fact the soft X-ray observations do not cover the full extent of the
COMPTEL source position uncertainty make an association hard to quantify and thus risky. At the best location of the source,
detections at hard X-rays show only upper limits, which, together with MeV results obtained by COMPTEL suggest the existence
of a peak in power output located somewhere between 300–700 keV for the so-called low state. Such a spectrum resembles those
in blazars or microquasars, and might suggest at work by the models accordingly. However, an analysis using a microquasar
model consisting on a magnetized conical jet filled with relativistic electrons, shows that it is hard to comply with all
observational constrains. This fact and the non-detection at hard X-rays introduce an a-posteriori question mark upon the
physical reality of this source, what is discussed here. 相似文献
63.
Shu-Ping Yan Jin-Lu Qu Guo-Qiang Ding Peng Han Li-Ming Song Shu Zhang Hong-Xing Yin Cheng-Min Zhang Jian-Min Wang 《Astrophysics and Space Science》2012,337(1):137-146
Systematically studying all the RXTE/PCA observations for GRS 1915+105 before November 2010, we have discovered three additional patterns in the relation between
Quasi-Periodic Oscillation (QPO) frequency and photon energy, extending earlier outcomes reported by Qu et al. (Astrophys.
J. 710:836, 2010). We have confirmed that as QPO frequency increases, the relation evolves from the negative correlation to positive one.
The newly discovered patterns provide new constraints on the QPO models. 相似文献
64.
能谱仅反映了高能天体辐射的部分性质,而高能X射线辐射的时变可以反映致密天体的动态性质。因此,在构造高能辐射的理论模型时,既要考虑X辐射的能谱性质,也要考虑其时变性质。特别对高能天体X辐射的快速光变,一般认为其发生在致密天体附近,致密天体快速光变的研究可以揭示出致密天体附近的物理性质,因此,时变可以对X辐射模型给以很强的限制。X射线源不同能量光子到达观测者的时间差称为X射线辐射的时延。介绍了高能X辐射时变中的时延分析方法及其最新发展,综述了致密双星系统中黑洞侯选林和中子星的时延现象,并简单介绍了为解释这些现象所发展的模型,以及时延对模型的限制。 相似文献
65.
Z. Q. Qu C. L. Xu X. Y. Zhang X. L. Yan C. L. Jin 《Monthly notices of the Royal Astronomical Society》2006,370(4):1790-1796
The influence of magnetic fields on the energy level populations of atoms is firstly studied by analysing the Stokes profiles of Fe i 6302.5 forming in the solar magnetized atmosphere, with the aid of a departure factor defined to evaluate the deviation from the normal Boltzmann distribution without a magnetic field. This factor is directly related to the ratio of line-source function to the continuum one. The relationship between the departure and the magnetic field reveals an effect that the magnetic field induces an exponential increase in the level population of the lower level of Fe i 6302.5 (Landé factor g = 2.5 ) with the field strength. This indicates that the magnetic field can cause the redistribution of populations of those levels whose Landé factors are non-zero. Therefore, this effect should be included in the calculation of the statistical equilibrium. Secondly, an experiment utilizing the Hg5461 line in the laboratory on the Earth is carried out to reveal that the exponential relation is independent of variations in temperature, and the excitation is completely magneto-induced. Finally, the exponential relation is explained by taking account of the magnetic energy in the Boltzmann distribution. 相似文献
66.
Geochemical evidence of an extraterrestrial component in impact melt breccia from the Paleoproterozoic Dhala impact structure,India 下载免费PDF全文
Jayanta Kumar Pati Wen Jun Qu Christian Koeberl Wolf Uwe Reimold Munmun Chakarvorty Ralf Thomas Schmitt 《Meteoritics & planetary science》2017,52(4):722-736
The Paleoproterozoic Dhala structure with an estimated diameter of ~11 km is a confirmed complex impact structure located in the central Indian state of Madhya Pradesh in predominantly granitic basement (2.65 Ga), in the northwestern part of the Archean Bundelkhand craton. The target lithology is granitic in composition but includes a variety of meta‐supracrustal rock types. The impactites and target rocks are overlain by ~1.7 Ga sediments of the Dhala Group and the Vindhyan Supergroup. The area was cored in more than 70 locations and the subsurface lithology shows pseudotachylitic breccia, impact melt breccia, suevite, lithic breccias, and postimpact sediments. Despite extensive erosion, the Dhala structure is well preserved and displays nearly all the diagnostic microscopic shock metamorphic features. This study is aimed at identifying the presence of an impactor component in impact melt rock by analyzing the siderophile element concentrations and rhenium‐osmium isotopic compositions of four samples of impactites (three melt breccias and one lithic breccia) and two samples of target rock (a biotite granite and a mafic intrusive rock). The impact melt breccias are of granitic composition. In some samples, the siderophile elements and HREE enrichment observed are comparable to the target rock abundances. The Cr versus Ir concentrations indicate the probable admixture of approximately 0.3 wt.% of an extraterrestrial component to the impact melt breccia. The Re and Os abundances and the 187Os/188Os ratio of 0.133 of one melt breccia specimen confirm the presence of an extraterrestrial component, although the impactor type characterization still remains inconclusive. 相似文献
67.
68.
Z. B. Li L. M. Song J. L. Qu Y. J. Lei J. Y. Nie C. M. Zhang 《Astrophysics and Space Science》2012,341(2):383-393
In this paper, the rms-flux (root mean square-flux) relation along the Z-track of the bright Z-Source Cyg X-2 is analyzed using the observational data of Rossi X-ray Timing Explorer (RXTE). Three types of rms-flux relations, i.e. positive, negative, and ‘arch’-like correlations are found in different branches. The rms is positively correlated with flux in normal branch (NB), but anti-correlated in the vertical horizontal branch (VHB). The rms–flux relation shows an ‘arch’-like shape in the horizontal branch (HB). We also try to explain this phenomenon using existing models. 相似文献
69.
J. Wang H. K. Chang C. M. Zhang D. H. Wang L. Chen J. L. Qu L. M. Song 《Astrophysics and Space Science》2012,342(2):357-364
We take the recently published data of twin kHz quasi-period oscillations (QPOs) in neutron star (NS) low-mass X-ray binaries (LMXBs) as the samples, and investigate the morphology of the samples, which focuses on the quality factor, peak frequency of kHz QPOs, and try to infer their physical mechanism. We notice that: (1) The quality factors of upper kHz QPOs are low (2~20 in general) and increase with the kHz QPO peak frequencies for both Z and Atoll sources. (2) The distribution of quality factor versus frequency for the lower kHz QPOs are quite different between Z and Atoll sources. For most Z source samples, the quality factors of lower kHz QPOs are low (usually lower than 15) and rise steadily with the peak frequencies except for Sco X-1, which drop abruptly at the frequency of about 750 Hz. While for most Atoll sources, the quality factors of lower kHz QPOs are very high (from 2 to 200) and usually have a rising part, a maximum and an abrupt drop. (3) There are three Atoll sources (4U 1728-34, 4U 1636-53 and 4U 1608-52) of displaying very high quality factors for lower kHz QPOs. These three sources have been detected with the spin frequencies and sidebands, in which the source with higher spin frequency presents higher quality factor of lower kHz QPOs and lower difference between sideband frequency and lower kHz QPO frequency. 相似文献
70.
We present a rare observation of direct magnetic interaction between an activating filament and a coronal hole(CH). The filament was a quiescent one located at the northwest of the CH. It underwent a nonradial activation, during which filament material constantly fell and intruded into the CH. As a result, the CH was clearly destroyed by the intrusion. Brightenings appeared at the boundaries and in the interior of the CH, meanwhile, its west boundaries began to retreat and the area gradually shrank. It is noted that the CH went on shrinking after the end of the intrusion and finally disappeared entirely. Following the filament activation, three coronal dimmings(D1–D3) were formed, among which D1 and D2 persisted throughout the complete disappearance of the CH. The derived coronal magnetic configuration shows that the filament was located below an extended loop system, which obviously linked D1 to D2. By extrapolating this result, our observations imply that the interaction between the filament and the CH involved direct intrusion of the filament material to the CH and the disappearance of the CH might be due to interchange reconnection between the expanding loop system and the CH's open field. 相似文献