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21.
The microstructures of turbiditic and hemipelagic muds and mudstones were investigated using a scanning electron microscope to determine whether there are microstructural features that can differentiate turbiditic from hemipelagic sedimentary processes. Both types of muddy deposits are, in general, characterized by randomly‐oriented clay particles. However, turbiditic muds and mudstones also characteristically contain aggregates of ‘edge‐to‐face’ contacts between clay particles with long‐axis lengths of up to 30 μm. Based on observations of the clay fabric of the experimentally‐formed muds settled from previously agitated muddy fluids, these types of aggregates, hereafter referred to as ‘aggregates of clay particles’, are interpreted as having been formed by the collision of component flocs in turbulent fluids. Furthermore, some aggregates of clay particles have ‘face‐to‐face’ contacts between clay particles; this is similar to face‐to‐face aggregates characteristically developed in fluid‐mud deposits that are commonly recognized only in turbiditic mudstones, indicating the possibility of a final stage of deposition under highly‐dense conditions, such as temporary fluid muds. In conjunction with earlier proposed lithofacies‐based and ichnofacies‐based criteria, aggregates of clay particles should be useful for the differentiation of turbiditic and hemipelagic muddy deposits, particularly with limited volumes of non‐oriented samples from deep‐water successions.  相似文献   
22.
This study examines the effect of contact metamorphism by an igneous dyke on parameters for kerogen maturation, such as elemental composition (H/C, O/C, N/C), 1H-NMR T1, vitrinite reflectance and infrared spectra. Although elemental composition and 1H-NMR T1 of the kerogen changed only within 1.5 and 5.0 m from the dyke respectively, vitrinite reflectance of the kerogen was thermally affected beyond 10.0 m from the intrusion. It is concluded that vitrinite reflectance is the most sensitive of the parameters evaluated to assess thermal stress of kerogens.  相似文献   
23.
Concentrations of 12 trace elements (V, Cr, Mn, Cu, Zn, Se, Rb, Sr, Cd, Cs, Ba, and Hg) were determined in liver and skin tissues of minke whales from various regions within the Antarctic Ocean. Cd concentrations in livers of southern minke whale were apparently higher than those in cetaceans from other regions, while Hg concentrations were lower. There were significant positive correlations between body length and concentrations of Cd and Hg in the liver. The concentrations of all trace elements in the skin were lower than those in other cetaceans reported previously. Significant positive correlations between liver and skin were found for Cr, Mn, Cu, Zn, Rb, Cd, and Cs, implying that the concentrations of these trace elements in the skin reflect those of internal organs. Large interannual variation of the accumulation pattern of trace elements in the skin was observed for the southern minke whales from Area V. There were significant differences in the skin element concentrations among Areas III, IV, and V, especially for males. Also, discriminant analysis between geographically two different groups collected during 1995/1996 austral summer season, based on the concentrations of trace elements in the skin, allowed for a correct classification of 90% of these minke whales. These results suggest that measurement of trace elements in skin samples could provide valuable information on the status of contamination and possible geographic differences in the accumulation levels in southern minke whales.  相似文献   
24.
从节旋藻属5个品系和螺旋藻属1个品系中克隆了hoxY基因的部分序列.序列长度都是479bp.在节旋藻中该基因GC含量为46.0%~46.6%,螺旋藻中为43.5%.节旋藻各品系间序列的相似性介于93.7%~100%,明显高于节旋藻属和螺旋藻属间的序列相似性(69.5%~72.2%).2个属中镍铁氢化酶小亚基HoxY氨基酸序列的比较也表明螺旋藻和节旋藻之间存在较大差异.利用MEGA2通过比较核酸序列构建了系统树,表明螺旋藻和节旋藻属处于不同的分枝.  相似文献   
25.
In drylands, water deficit is the primary factor limiting plant growth. In the present study, surface energy balance and plant growth (above‐ground and below‐ground biomass) were measured continuously during the 2002 growing season in semiarid grassland in the northern part of Kazakhstan, Central Asia. Although there was above normal total rainfall during the 2002 growing season (May–November; 244 mm over 183 days), there was a dry period during July and August. Evaporative water was effectively supplied by precipitation and surface soil moisture during the wet season (May and June), during which time above‐ground biomass increased. During the early stages of the dry period, mature plants were likely to tap deeper sources of soil moisture, representing stored snowmelt water. As the soil moisture content decreased during the summer dry period due to the high levels of evapotranspiration and lack of precipitation, the evaporative fraction and above‐ground biomass rapidly decreased, whereas the below‐ground biomass increased. These results suggest that in summer, soil moisture acts to store water, and that soil moisture is essential for plant growth as a direct source of water during the dry period in natural grasslands in the Kazakhstan steppe. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
26.
River runoff from the four largest Siberian river basins (the Ob, Yenisei, Lena, and Kolyma) considerably contributes to freshwater flux into the Arctic Ocean from the Eurasian continent. However, the effects of variation in snow cover fraction on the ecohydrological variations in these basins are not well understood. In this study, we analysed the spatiotemporal variability of the maximum snow cover fraction (SCFmax) in the four Siberian river basins. We compared the SCFmax from 2000 to 2016 with data in terms of monthly temperature and precipitation, night-time surface temperatures, the terrestrial water storage anomaly (TWSA), the normalised difference vegetation index (NDVI), and river runoff. Our results exhibit a decreasing trend in the April SCFmax values since 2000, largely in response to warming air temperatures in April. We identified snowmelt water as the dominant control on the observed increase in the runoff contribution in May across all four Siberian river basins. In addition, we detected that the interannual river runoff was predominantly controlled by interannual variations in the TWSA. The NDVI in June was strongly controlled by the timing of the snowmelt along with the surface air temperature and TWSA in June. The rate of increase in the freshwater flux from the four Siberian rivers decreased from 2000 to 2016, exhibiting large interannual variations corresponding to interannual variations in the TWSA. However, we identified a clear increase trend in the freshwater flux of ~4 km3/year when analysing the long-term 39-year historical record (1978–2016). Our results suggest that continued global warming will accelerate the transition towards the earlier timing of snowmelt and spring freshwater flux into the Arctic Ocean. Our findings also highlight the effects of earlier snowmelt on ecohydrological changes in the Northern Hemisphere.  相似文献   
27.
This paper introduces QSAT, the satellite for polar plasma observation. The QSAT project began in 2006 as an initiative by graduate students of Kyushu University, and has the potential to contribute greatly to IHY (International Heliophysical Year) by showing to the world the beauty, importance, and relevance of space science. The primary objectives of the QSAT mission are (1) to investigate plasma physics in the Earth’s aurora zone in order to better understand spacecraft charging, and (2) to conduct a comparison of the field-aligned current observed in orbit with ground-based observations. The QSAT project can provide education and research opportunities for students in an activity combining space sciences and satellite engineering. The QSAT satellite is designed to be launched in a piggyback fashion with the Japanese launch vehicle H-IIA. The spacecraft bus is being developed at the Department of Aeronautics and Astronautics of Kyushu University with collaboration of Fukuoka Institute of Technology. Regarding the payload instruments, the Space Environment Research Center of Kyushu University is developing the magnetometers, whereas the Laboratory of Spacecraft Environment Interaction Engineering of Kyushu Institute of Technology is developing the plasma probes. We aim to be ready for launch in 2009 or later.  相似文献   
28.
29.
Abstract. Bottom-simulating reflectors suggestive of the presence of methane hydrates are widely distributed below the ocean floor around Japan. In late 1999, drilling of the MITI Nankai Trough wells was conducted to explore this potential methane hydrate resource and a Tertiary conventional structure. The wells are located in the Northwest Pacific Ocean off Central Japan at a water depth of 945 m. A total of six wells were drilled, including the main well, two pilot wells, and three post survey wells at intervals of 10–100 m. All wells except the first confirmed the occurrence of hydrates based on logging-while-drilling, wire-line logging and/or coring using a pressure and temperature coring system in addition to conventional methods. Based on the various well profiles, four methane hydrate-bearing sand-rich intervals in turbidite fan deposits were recognized. Methane hydrates fill the pore spaces in these deposits, reaching saturation of up to 80 % in some layers. The methane hydrate-bearing turbiditic sand layers are less than 1 m thick, with a total thickness of 12–14 m. The bottom depth of high hydrate concentration correlates well with the depth of the bottom-simulating reflector. Based on these exploration results, the Japanese government inaugurated a 16-year methane hydrate exploitation program in 2001.  相似文献   
30.
This study presents full-length cDNA sequences of CYP1A1 and 1A2, in common minke whale (Balaenoptera acutorostrata) from the North Pacific. Both CYP1A1 and CYP1A2 cDNAs had an open reading frame of 516 amino acid residues, and predicted molecular masses were 58.3 kDa and 58.1 kDa, respectively. The deduced full-length amino acid sequence of CYP1A1 revealed higher identities with those of sheep (86%) and pig (87%), and that of CYP1A2 was most closely related to human (82%) and monkey CYP1A2 (82%) among species from which CYP1A2 has been isolated so far. Differences in certain conserved and functional amino acid residues of CYP1A1 and 1A2 between common minke whale and other mammalian species indicate the possibility of their specific metabolic function. Concentrations of organochlorine compounds (OCs) including PCBs and DDTs analyzed in common minke whale liver showed no significant correlation with hepatic mRNA expression levels of CYP1A1 and CYP1A2, indicating no induction of these enzymes by such OCs.  相似文献   
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