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31.
32.
Charles R. Ross II 《Physics and Chemistry of Minerals》1988,15(3):274-282
A kinetic statistical model based upon a one-dimensional Ising lattice reflecting the nature of the pyroxene octahedral strip, and with nearest-neighbor and mean-field interactions, is applied to the order-disorder transformation in omphacitic pyroxenes. The equilibration temperature of a naturally ordered omphacite and the annealing data of Carpenter (1981a) on omphacites from the same sample, when applied to the model, provide time- temperature-transformation relations for both long-range and short-range ordering. Results indicate that cooling times on the order of tens of millions of years are necessary for the development of significant degrees of long-range order under optimum conditions, whereas short-range order is developed on much shorter time scales. These results are in agreement with observations of naturally ordered and disordered omphacites with the exception of omphacites ordered in a low-temperature subduction-zone regime; the results support the hypothesis that these omphacites crystallize in a highly ordered state. 相似文献
33.
Neal J. Evans II Shudong Zhou Carsten Kömpe C. M. Walmsley 《Astrophysics and Space Science》1994,212(1-2):139-145
The globular molecular cloud B335 contains a single, deeply embedded, far-infrared source. Our recent observations of H2CO and CS lines toward this source provide direct kinematic evidence for collapse. Both the intensity and detailed shape of the line profiles match those expected from inside-out collapse inside a radius of 0.036 pc. The collapse began about 1.5 × 105 years ago, similar to the onset of the outflow. The mass accretion rate is about 10 times the outflow rate, and about 0.4M
should have now accumulated in the star and disk. Because B335 rotates only very slowly, any disk would still be very small (about 3 AU). The accretion luminosity should be adequate to power the observed luminosity. Consequently, we believe that B335 is indeed a collapsing protostar.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A. 相似文献
34.
B. L. Turner II 《Geoforum》2002,33(4):427-429
Reviews and observations about the status of the discipline of geography, no matter how positive, invariably raise programmatic concerns. These concerns have a long history that arise from geography's struggles to find an identity that embraces its many parts and yet are consistent with the logic by which the academy partitions knowledge. Pedagogy and research historically claimed by geography is currently being reinvented and relabeled under such headings as “integrated environmental science” and “spatial science”, and these developments have the potential to change the breadth of the “geographic imagination”. Several observations about dominant explanatory perspectives and substantive domains of geographic enquiry are also provided. 相似文献
35.
36.
G. W. Collins II 《Astrophysics and Space Science》1980,73(2):355-378
The effects of formation of a binary black hole in a dense star cluster are found to have significant effects on the dynamics of the cluster. Tidal destruction of stars captured into bound orbits during the formation of the black hole binary provide a sizeable source of very high temperature thermal radiation as well as a source of radially outward moving clouds of gas. The efficiency of subsequently accreted matter onto the binary components as an energy source is investigated and suggestive evolutionary models of the dynamics of the binary system are presented. Lifetimes of the system are shown to be compatible with contemporary estimates. It is suggested that the high-density cluster core provides a suitable environment for the operation of a number of models for the core of active galactic nuclei. 相似文献
37.
Larissa F. Dobrzhinetskaya Harry W. Green II Alex P. Renfro Krassimir N. Bozhilov Dirk Spengler Herman L. M. van Roermund 《地学学报》2004,16(6):325-330
Our experimental simulations of the exhumation path of mantle peridotites show that high‐temperature (1400 °C) decompression of lherzolite from 14 to 13 and 12 GPa results in exsolution of interstitial blebs of diopside and Mg2SiO4 (wadsleyite) lamellae from majoritic garnet. At lower pressures (from 8 to 5 GPa, at T = 1400 °C) only enstatite exsolves as blebs at garnet boundaries. Continuous high‐temperature decompression from 14 to 7 GPa produces zoned majoritic garnet containing blebs of exsolved pyroxenes inside garnet rims. No intracrystalline precipitation of pyroxene was observed in garnet, although such lamellae are found in some natural garnet peridotites. The explanation appears to be the three orders of magnitude difference in grain size between experimental and natural specimens. Our data suggest that Mg2SiO4 and diopside exsolutions reflect the deepest point of the exhumation path of garnet peridotites, whereas enstatite precipitation may be restricted to garnets with less majoritic component at shallower depths. 相似文献
38.
D. Javorsek II M. C. Brewer J. B. Buncher E. Fischbach J. T. Gruenwald J. Heim A. W. Hoft T. J. Horan J. L. Kerford M. Kohler J. J. Lau A. Longman J. J. Mattes T. Mohsinally J. R. Newport M. A. Petrelli C. A. Stewart J. H. Jenkins R. H. Lee B. Morreale D. B. Morris R. Mudry D. O’Keefe B. Terry M. A. Silver P. A. Sturrock 《Astrophysics and Space Science》2012,338(1):9-13
A new prediction technique based on logarithmic values is proposed to predict the maximum amplitude (R
m) of a solar cycle from the preceding minimum aa geomagnetic index (aa
min). The correlation between lnR
m and lnaa
min (r=0.92) is slightly stronger than that between R
m and aa
min (r=0.90). From this method, cycle 24 is predicted to have a peak size of R
m(24)=81.7(1±13.2%). If the suggested error in aa (3 nT) before 1957 is corrected, the correlation coefficient between R
m and aa
min (r=0.94) will be slightly higher, and the peak of cycle 24 is predicted much lower, R
m(24)=52.5±13.1. Therefore, the prediction of R
m based on the relationship between R
m and aa
min depends greatly on the accurate measurement of aa. 相似文献
39.
Charles E. Konrad II 《自然地理学》2013,34(3):227-248
Synoptic data associated with a sample of 554 heavy rainfall events is utilized to carry out a trajectory analysis that identifies the movements of moisture towards regions of heavy rain. Both seasonal and regional variations are found in the moisture trajectories associated with heavy rain events occurring in three regions in the Appalachian study area. Numerous events in the region west of the mountain range are tied to westerly and south-southwesterly circulations that bring moisture from the Mississippi River Valley and the Gulf of Mexico during the warm and cool seasons, respectively. Many events southeast of the mountain range are associated with southerly to southeasterly circulations that advect moisture from the Atlantic Ocean. Because of orographic precipitation enhancement and a good exposure to the Gulf of Mexico and the Atlantic Ocean, the southern and southeastern slopes of the Appalachian mountains display high frequencies of heavy rainfall, particularly during the cool season. The interior portions of the mountain range and the adjacent plateau to the northwest, on the other hand, are sheltered from moisture source regions and, therefore, exhibit low heavy rain frequencies. [Key words: precipitation, synoptic climatology, Appalachia.] 相似文献
40.
Water shortage is a chronic problem in arid Northwest China.The rapid population growth and expanding urbanization as well as potential climate change impacts are likely to worsen the situation,threatening domestic,irrigation,and industrial supplies and even the survival of the ecosystems in Northwest China.This paper describes the preliminary work of adapting the Distributed Large Basin Runoff Model(DLBRM) to the Heihe watershed(the second largest inland river in arid Northwestern China,with a drainage area of 128,000 km2) for understanding distribution of glacial-snow melt,groundwater,surface runoff,and evapotranspi-ration,and for assessing hydrological impacts of climate change and glacial recession on water supply in the middle and lower reaches of the watershed.Preliminary simulation results show that the Qilian Mountain in the upper reach area produces most runoff in the Heihe watershed.The simulated daily river flows during the period of 1990-2000 indicate that the Heihe River dis-charges about 1×109 m3 of water from the middle reach(at Zhengyixia Station) to lower reach,with surface runoff and interflow contributing 51 and 49 percent respectively.The sandy lower soil zone in the middle reach has the highest evapotranspiration rate and also contributes nearly half of the river flow.Work underway focuses on the DLBRM model improvement and incorporation of the climate change and management scenarios to the hydrological simulations in the watershed. 相似文献