全文获取类型
收费全文 | 239篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
大气科学 | 1篇 |
地球物理 | 24篇 |
地质学 | 134篇 |
海洋学 | 23篇 |
天文学 | 56篇 |
自然地理 | 2篇 |
出版年
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 10篇 |
2015年 | 3篇 |
2014年 | 10篇 |
2013年 | 14篇 |
2012年 | 12篇 |
2011年 | 15篇 |
2010年 | 18篇 |
2009年 | 20篇 |
2008年 | 15篇 |
2007年 | 18篇 |
2006年 | 19篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 6篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有240条查询结果,搜索用时 15 毫秒
71.
72.
In the course of the expedition of the Pacific Oceanological Institute in August 2007, extensive hypoxia was found in the
near-bottom layer of the Amur Bay water mass. The hypoxia’s formation was immediately reflected in the values and distribution
of the carbonate parameters in the near-bottom waters of the bay. The maximum values of the carbon dioxide partial pressure,
the dissolved inorganic carbon, and the total alkalinity were associated with the areas of the minimum oxygen content. The
microbial destruction of the dead phytoplankton greatly increased the partial pressure of carbon dioxide, which was over 2000
μatm in the hypoxia centers at a depth of about 20 m. At the same time, the carbon dioxide partial pressure in the surface
waters of Amur Bay was considerably lower than that in the atmosphere. Hence, the bay’s aquatic area was a sink for the atmospheric
CO2 despite its high content in the near-bottom waters. It was shown that the excess alkalinity associated with the hypoxia sites
in the near-bottom layer of water was caused by the sulfate reduction proceeding in the upper layer of the sediment. 相似文献
73.
We present our 2-year-long photometric (V, R c, I c) observations of the T Tauri star V1184 Tau. They show that the relatively quiet “photometric life” of this object, which ended in 2004 with a sharp brightness decline by four magnitudes, was succeeded by a qualitatively new (in nature) period of activity characterized by high-amplitude irregular photometric variability. Judging by its color variations, the object belongs to the class of UX Ori stars and, hence, variable circumstellar extinction is responsible for its brightness variations. Moreover, the (V?I c)/V color-magnitude diagram for the object is identical to that for UX Ori itself, suggesting that the optical properties of dust grains in the circumstellar space of these stars are similar. At the same time, V1184 Tau is quite dissimilar to UX Ori stars in its light curve, variability amplitude (reaching 4.5 magnitudes in the V band), and some other parameters. 相似文献
74.
V.A. Sergeev E.M. Sazhina N.A. Tsyganenko J.Å. Lundblad F. Søraas 《Planetary and Space Science》1983,31(10):1147-1155
Characteristics of the nightside isotropic precipitation of energetic protons during a period of 4 quiet days has been studied using data from the ESRO 1A satellite. The observed features of the equatorward precipitation boundary (its thickness, energy dependence, dynamics, dependence of its latitudinal position on the magnetic field at the geosynchronous orbit, etc.) were found to be in good agreement with calculations based on recent magnetospheric magnetic field models. We argue that the mechanism of non-adiabatic pitchangle scattering in the equatorial current sheet is a dominant source of isotropic precipitation of energetic protons observed in the nightside auroral zone. Observations of the isotropic precipitation boundary can be used for monitoring the changes in the magnetotail current intensity. 相似文献
75.
V. N. Sergeev N. G. Vorob’eva P. Yu. Petrov 《Stratigraphy and Geological Correlation》2007,15(1):1-11
Excellently preserved organic-walled and silicified microfossils are first found in the Lower Riphean Ust-Il’ya and Kotuikan formations of the Billyakh Group in the northern slope of the Anabar Uplift (the Fomich River basin). Similar assemblages were previously known only from sections located southward in the Kotuikan River basin, and taxonomic composition of organic-walled microbiotas from the Ust-Il’ya and Kotuikan formations became a corner stone in competitive microphytological models that are based on different approaches. In their composition and general appearance, microbiotas from the Kotuikan and Ust-Il’ya formations in the Fomich River basin are similar to microbiotas reported from the Kotuikan River basin, although northern sections of the above formations characterize deeper sedimentation settings than in localities known before. The Ust-Il’ya and Kotuikan assemblages of organic-walled microfossils include sphaeromorphic Chuaria circularis and Leiosphaeridia, two-layer vesicles the genus Simia, filamentous Plicatidium and Taenitrichoides, and some others. The silicified microbiota from the lower Kotuikan Subformation is largely composed of akinetes of Anabaena-like cyanobacteria Archaeoellipsoides, spherical Myxococcoides grandis, and short trichomes Filiconstrictosus and Orculiphycus representing initial germination stages of Anabaena-like cyanobacterial spores. Acanthomorphic acritarchs known from lithology-similar Lower and Middle Riphean (Mesoproterozoic) formations of Australia and China have not been observed in the Ust-Il’ya and Kotuikan microbiotas, which are probably of older age. The found microbiotas outline substantially wider distribution area of organic-walled and silicified microfossils, supplement microphytological characteristics of Riphean sediments in the Anabar Uplift, provide information on taxonomic composition of microbiotas from a wider spectrum of facies, and specify relationships between Early and Middle Riphean assemblages of microorganisms from different continents. 相似文献
76.
Geology of Ore Deposits - The microstructure and composition of accessory chromian spinels from peridotite and ore-forming chromian spinels from disseminated ores in dunite near the boundary... 相似文献
77.
78.
Precambrian stromatolites were studied with a complex approach including two complementary methods. The biogenic origin of ultramicrostructures examined with SEM was supported by the traditional optical microscopy. The paper addresses columnar-stratiform stromatolites of the Vendian Chencha Formation in the Ura Uplift (Baikal–Patom Highland, Central Siberia) and fossilized remains of coccoidal and filamentous microorganisms therein: cyanobacteria Eoentophysalis, hormogonian cyanobacteria Siphonophycus and, probably, Eomicrocoleus. The unraveled community of stromatolite builders includes the major organisms commonly observed in the Precambrian microbiota. Stromatolites of the Chencha Formation contained not only cyanobacteria, but also remains of eukaryotic microorganisms, including likely testate amoebae and acanthomorphic acritarchs. It is shown that the complex approach rules out incorrect determination of biota and significantly enhances concepts of the origin and formation of stromatolites, as well as the participation of microorganisms in their formation. 相似文献
79.
80.
V. P. Grinin O. Yu. Barsunova S. G. Sergeev A. A. Arkharov S. Yu. Shugarov A. O. Semenov N. V. Efimova 《Astronomy Reports》2018,62(10):677-688
The results of many-year photometric observations of the weak-line T Tauri star V715 Per in the optical (V RI) and infrared (JHK) photometric bands are presented. The period of the star’s lowamplitude brightness variations in the V RI bands detected earlier, 5.23d, is confirmed. This period persists during the entire 14-year time interval of the observations, but its amplitude varies with time. The same period was found in the variations of JHK infrared fluxes, with the brightness variations in the two ranges being almost synchronous. The most probable origin of these variations is periodic eclipses of the star by its own disk, perturbed by its interaction with the magnetosphere (AA Tau-type variations). In addition to the periodic brightness variations, the star also displayed sporadic Algol-like minima characteristic of UX Ori stars during several years (2005–2011). The amplitude of these variations increasedmonotonically, reaching approximately 1m in the V band by the end of 2010, after which the deep fadings ended. During this entire time interval, the amplitude of the periodic variations was observed to decrease. After 2011, the periodic component began to become stronger again. These changes of the photometric activity of V715 Per can be explained by an increasing rate of gas accretion onto the star, decreasing the radius of warped regions of the disk and leading to accompanying Algol-like fadings. This model assumes a low inclination of the circumstellar disk in V715 Per to the line of sight. 相似文献