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491.
It is shown that it can be useful to incorporate the orbital period P as an additional parameter into the Kukarkin-Parenago relationship. Then it turns out that the relationship splits into two, one holding for objects above and the other for objects below the well-known and much-discussed period gap between 2.2 and 2.8 hours A = -2.03 + 2.26 log C + 8.80 log P for P > 2.2 h A = 2.07 + 2.46 log C - 3.68 log P for P > 2.8 h (A amplitude (mag), C cycle length (d), P orbital period (h)). Future theories of the dwarf nova phenomenon and the origin of the period gap will have to deal with this. 相似文献
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494.
Parastoo Ghaznavi Yogita Kadlag David Haberthür Ruslan Hlushchuk Ingo Leya 《Meteoritics & planetary science》2023,58(6):897-900
Micro-computed tomography (μCT) is a fast and powerful technology for studying textural, physical, and chemical properties of solid objects in three dimensions. While regularly used for sample documentation and curation, it is often assumed that μCT techniques are essentially nondestructive or at least very little destructive. However, there are very few studies proving or rejecting the assumption of nondestructiveness. Here we study whether X-ray tomographic imaging affects the noble gas budget of matrix samples from the CV3 carbonaceous chondrite Allende. We irradiated powdered and homogenized matrix samples in the Bruker SkyScan 1272 μCT instrument at three different X-ray tube acceleration voltages of 30, 70, and 100 keV. By comparing the noble gas concentrations and especially the elemental and isotopic ratios of the irradiated samples with data for two non-irradiated aliquots, we found no significant differences. Our study therefore demonstrates that X-ray tomographic imaging has no measurable effect on the noble gas budget and can therefore safely be used for sample characterization prior to noble gas studies. 相似文献
495.
The comparison of the spatial distribution of galaxies in the surroundings of the nearest compact and loose groups of galaxies confirms that compact groups are very likely to be part of looser groups and shows that loose groups associated to compact groups tend to have higher spatial density than normal ones. 相似文献
496.
Photometric data (magnitudes, radii, profiles) for galaxies in the field of 7 nearby groups of galaxies are measured by photographic surface photometry. Most of them are dwarf galaxies. 相似文献
497.
P. Rafanelli S. Roi A. Tegon H. Schulz S. Di Serego-Alighieri S. Komossa G. Richter J. Vennik 《Astronomische Nachrichten》1997,318(6):319-327
[OIII] images and blue spectra of the emission-line dwarf galaxy F348 are presented. In [OIII] light, the object contains two knots about 9” NE of the nucleus and one large extended knot 11” to the SW. The nuclear region is hundred times less luminous in emission-line light than the knots. Despite the presence of line intensity ratios [OIII]λ5007/Hβ > 3 the prior classification as a Seyfert-2 object cannot be upheld. This clinches an earlier suggestion by Veron-Cetty & Veron (1986). In particular, we show that the line spectra can be modeled with photoionization models employing stellar input continua. Also, the line luminosities of the extranuclear knots are typical for giant HII regions. There is neither evidence for tidal tails nor for high velocity differences between the knots. In addition, the linear arrangement of the knots does not support interaction. It rather suggests self-propagating star formation In this picture, the faintness of the nuclear region can be understood by an edge-on view. In addition, the nuclear starburst appears to be fading in contrast to the young extranuclear star formation regions. Within the scheme of Melnick (1987), F348 has to be classified as a multiple-system HII galaxy. 相似文献
498.
N. Richter 《Astronomische Nachrichten》1978,299(6):325-330
The results of the U, B, V photometries of W. BRONKALLA and N. RICHTER near the north galactic pole are discussed. In these photometries which have been carried out on the same Tautenburg Schmidt plates the share of blue objects suspected as quasistellar (QSO) has been determined by total photometry of all starlike objects in selected partly overlapping test fields. The results of both photometries agree very well. The position of the blue objects of the Tautenburg catalogues and BRONKALLA's photometry in the two-colour diagram is compared with the two-colour diagram of QSO's published by C. BARBIERI and M. CAPPACIOLI . In both cases 65 per cent of the objects are placed on the right-hand side and 35 per cent on the left-hand side (region of white dwarfs) of the black-body line. Therefore, it is no longer admissible to qualify in a photometric statistics of blue objects all those objects as white dwarfs which are situated on the left-hand side of the black-body line in the two-colour plot. This result is confirmed by the discussion of the number-magnitude relation of these objects. Clustering of blue objects and their connection with clusters of galaxies are discussed. Using results from A. SANDAGE and E. M. BURBIDGE and our own results one can conclude that more than 60 per cent of Tautenburg blue objects must be QSO's. For further spectroscopic and proper motion investigations it is proposed to prefer the objects placed on the left-hand side of the black-body line in order to obtain the real share of white dwarfs in this group of objects suspected to be quasistellar. 相似文献
499.