首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   63篇
  免费   2篇
测绘学   1篇
大气科学   1篇
地球物理   14篇
地质学   16篇
海洋学   17篇
天文学   10篇
综合类   2篇
自然地理   4篇
  2021年   3篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2014年   1篇
  2013年   1篇
  2012年   1篇
  2011年   3篇
  2010年   3篇
  2009年   6篇
  2008年   1篇
  2007年   4篇
  2006年   4篇
  2005年   4篇
  2004年   1篇
  2003年   1篇
  2001年   1篇
  2000年   3篇
  1999年   1篇
  1997年   1篇
  1995年   1篇
  1991年   1篇
  1988年   1篇
  1987年   1篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1975年   1篇
  1964年   1篇
  1963年   1篇
  1960年   1篇
排序方式: 共有65条查询结果,搜索用时 31 毫秒
31.
A molecular spectral line survey of the title source detected 166 molecular lines from 18 interstellar molecules in the frequency ranges of 34.25–50.00, 83.50–84.50, and 86.00–91.50 GHz. For each molecule, gaussian decomposition of the velocity components in the transition profiles gave consistent radial velocity and linewidth. Rotation diagrams were drawn for each velocity component.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   
32.
Both evergreen and deciduous forests (Efs and Dfs) are widely distributed under similar climatic conditions in tropical monsoon regions. To clarify the hydraulic properties of the soil matrix in different forest types and their effects on soil water storage capacity, the soil pore characteristics (SPC) were investigated in Ef and Df stands in three provinces in Cambodia. Soils in the Ef group were characterized in common by large amounts of coarse pores with moderate pore size distribution and the absence of an extremely low Ks at shallow depths, compared to Df group soils. The mean available water capacity of the soil matrix (AWCsm) for all horizons of the Ef and Df group soils was 0·107 and 0·146 m3 m?3, respectively. The mean coarse pore volume of the soil matrix (CPVsm) in the Ef and Df groups was 0·231 and 0·115 m3 m?3, respectively. A water flow simulation using a lognormal distribution model for rain events in the early dry season indicated that variation in SPC resulted in a larger increase in available soil water in Ef soils than in Df soils. Further study on deeper soil layers in Ef and each soil type in Df is necessary for the deeper understanding of the environmental conditions and the hydrological modelling of each forest ecosystem. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
33.
Detailed spatiotemporal structures for the submonthly-scale (7–25 days) intraseasonal oscillation (ISO) in summer monsoon rainfall and atmospheric circulation were investigated in South Asia using high-quality rainfall and reanalysis datasets. The Meghalaya–Bangladesh–coast of the western Myanmar (MBWM) region is the predominant area of submonthly-scale ISO in the Asian monsoon regions. The distinct rainfall ISO is caused by a remarkable alternation of low-level zonal wind between westerly and easterly flows around the Gangetic Plain on the same timescales. In the active ISO phase of the MBWM, a strong low-level westerly/southwesterly flows around the plain and a center of cyclonic vorticity appears over Bangladesh. Hence, a local southerly flows toward the Meghalaya Plateau and there is strong southwesterly flow towards the coast along southeastern Bangladesh and western Myanmar, resulting in an increase in orographic rainfall. Rainfall also increases over the lowland area of the MBWM due to the low-level convergence in the boundary layer under the strong cyclonic circulation. The submonthly-scale low-level wind fluctuation around the MBWM is caused by a westward moving n = 1 equatorial Rossby (ER) wave. When the anticyclonic (cyclonic) anomaly related to the ER wave approaches the Bay of Bengal from the western Pacific, humid westerly/southwesterly (easterly/southeasterly) flows enhance around the Gangetic Plain on the northern fringe of the anticyclone (cyclone) and in turn promote (reduce) rainfall in the MBWM. Simultaneously, robust circulation signals are observed over the mid-latitudes. In the active phase, cyclonic anomalies appear over and around the TP, having barotropic vertical structure and also contributing to the enhancement of low-level westerly flow around the Gangetic Plain. In the upper troposphere, an anticyclonic anomaly is also observed upstream of the cyclonic anomaly over the TP, having wavetrain structure. The mid-latitude circulation around the TP likely helps to induce the distinct ISO there in conjunction with the equatorial waves. Thus, the distinct ISO in the MBWM is strongly enhanced locally (~500 km) by the terrain features, although the atmospheric circulation causing the ISO has a horizontal scale of ~6,000 km or more, extending across the whole Asian monsoon system from the tropics to mid-latitudes.  相似文献   
34.
黑河流域土地利用变化对地下水资源的影响   总被引:1,自引:0,他引:1  
Land use and land cover changes have a great impact on the regional hydrological process. Based on three periods of remote sensing data from the 1960s and the long-term observed data of groundwater from the 1980s, the impacts of land use changes on the groundwater system in the middle reach of Heihe River Basin in recent three decades are analyzed by the perspective of groundwater recharge and discharge system. The results indicate that with the different intensities of land use changes, the impacts on the groundwater recharge were 2.602 × 10^8 m^3/a in the former 15 years (1969-1985) and 0.218 × 10^8 m^3/a in the latter 15 years (1986-2000), and the impacts on the groundwater discharge were 2.035 × 10^8 m^3/a and 4.91 × 10^8 m^3/a respectively. When the groundwater exploitation was in a reasonable range less than 3.0 × 10^8 m^3/a, the land use changes could control the changes of regional groundwater resources. Influenced by the land use changes and the large-scale exploitation in the recent decade, the groundwater resources present apparently regional differences in Zhangye region. Realizing the impact of land use changes on groundwater system and the characteristics of spatial-temporal variations of regional groundwater resources would be very important for reasonably utilizing and managing water and soil resources.  相似文献   
35.
36.
A modulation function representing the position and density of (Na, Ca) atoms in the superstructure of the e-plagioclase has been derived from the average structures of different plagioclase and a general modulation theory. Based on this function the superstructure of bytownite (An73) has been studied with the single crystal X-ray method. The cell dimensions by Megaw's axes are a=7.946(3)A, b=67.09(2)A, c=12.236(4)A, α=39.03(1)°, β=45.63(1)° and γ=59.63(1)°. Z=18(Na, Ca) Al(Al, Si)Si2O8. The initial phase factor of the modulation function for bytownite has been obtained from the intensity data of the satellite reflections. This modulation function indicates a coherent small-scale alternation of the Na-rich and Ca-rich bands in the superstructure. This superstructure has been refined by applying the albite and anorthite structures to the Na-rich and Ca-rich bands, respectively. The change of the superstructure of the e-plagioclase due to the compositional change has been described based on the movements of the satellites in reciprocal space. The direction of the coherent small-scale intergrowth of the anorthite-like and albite-like bands is perpendicular to the t vector. The thickness of the intergrowth is 1/|t|. Both direction and thickness change regularly from An75 to An25.  相似文献   
37.
Mt. Yaké or Yaké-daké is a dissected dome-shaped volcano mainly composed of the biotite bearing augite-hypersthene-hornblende andesite lavas extruded on the high mountain ridge consisting of the granite and hard Palaeozoic rocks between two prefectures Nagano and Gifu in the central part of Japan. It had been almost in dormant state only with weak fumarole activity on and around its summit dome since the former active period from 1907 to 1932. Incandescent lava emission has never been recorded in the historic age. On 17th June 1962 at about 21 h 55 m, a sudden explosion took place on the northern side of the dome. After successive explosions a fissure, about 700 m in length, was formed. On 19th from the northeast end of the fissure, milky hot water suspending muddy material flowed out. The mud flow ran down on the slope along the dry gully and poured into the Lake Taisyo-iké, about 2.5 km east of the vent. The lake was formed in 1915-eruption when a tremendous mud flow dammed up Azusagawa, the river running through the valley east of the volcano. Ejected blocks were deposited on the area within 1 km from the vent. Ash was deposited about 1 cm in thickness on the area about 4 km east of the volcano. Several mud flows poured into the Lake Taisyo-iké and the River Azusagawa. But no red-hot ejecta was observed during the present eruption, and temperature near the vent was lower than 100°C. Thus the present eruption is said to be low temperature phreatic explosions. In suspensoids of the hot water and in clayey matter deposited around the new vent are contained the montmorillonites, which hove never been found in the rocks exposed on the volcano in spite of the detailed investigation of the writers over 10 years. On the other hand, the mineral is not expected to be formed in the altered rocks under oxydized state on the surface. It was fine, at least no rain, before and during the explosions and the mud flow ran down along the dry gully. So the hot water was purely derived from the inner part of the volcano and the mud flow was not brought about by rain fall after deposition of ejecta on the volcano. The mud flow must have been formed endogenously under the volcano where the katamorphism of the rocks forming the volcano had advanced owing to chemical action of volcanic gas in the long period before the eruption.  相似文献   
38.
The title telescope — in operation since 1982 — gives a surface accuracy of better than 0.2 mm (r.m.s.), with an aperture efficiency of about 25% at 115 GHz. A 5-element interferometer is at final adjustment stage. Observations of proto-stellar objects, extragalactic objects, and spectral lines are briefly described.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   
39.
Welded tuffs in the Bogopol and Sijanov groups were sampled at 27 sites from 12 caldera formations in the Sikhote Alin mountain range around Kavalerovo (44.3°N, 135.0°E) for chronological and paleomagnetic studies. KAr age dates show that the welded tuffs erupted between 66 Ma and 46 Ma. All sites yield reliable paleomagnetic directions, with unblocking temperatures higher than 560°C. The high-temperature component at 12 sites and the medium-temperature component at 3 sites in the Bogopol Group show reversed polarity (D = 193.7°, I = −57.6°,95 = 8.1°). The high-temperature component at 11 sites in the Sijanov Group showed both reversed and normal polarities and its mean direction reveals no detectable deflection from north (D = −2.9°, I = 59.6°,95 = 11.2°). The combined paleomagnetic direction of the two groups yields a paleomagnetic pole of 250.5°E, 84.1°N (A95 = 8.8°), which falls near Cretaceous paleomagnetic poles from Outer Mongolia, Inner Mongolia, the North China Block and the South China Block. The Sikhote Alin area appears not to have been subjected to detectable motion with respect to East Asia since about 50 Ma. This implies that the Sikhote Alin area behaved as an integral part of East Asia during the opening of the Japan Sea at about 15 Ma. However, significant separation between the paleomagnetic poles of East Asia and Europe during the Jurassic-Paleogene implies a major relative movement between these two blocks since the Paleogene.  相似文献   
40.
Clinoenstatite crystals from a boninite and the Yamato-74191 chondrite have been studied with an analytical electron microscope. (100) twins and cracks perpendicular and parallel to the c axis are characteristic of their submicroscopic textures. The frequency in appearance along the c axis and widths of the cracks have been explained by the dimensional change of the c axis in the direct transformation of protoenstatite to clinoenstatite and by the cooling rate around the transformation temperature. The cracks in the crystals from the boninite are filled with fibrous crystals of talc, while those from the chondrite are open or filled with glass in which fine crystals of plagioclase are common.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号