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141.
Daisuke Nagaoka Masahito Shigemitsu Masao Minagawa Shinichiro Noriki 《Journal of Oceanography》2010,66(1):117-132
We have investigated Pb concentrations and isotopic compositions in settling particles collected by sediment traps experiments
over a period of two years, from May 2005 to April 2007, at two depths, 770 and 5100 m, at station KNOT in the Northwestern
Pacific Ocean (44°N, 155°E). To the identify provenances of Pb, the samples were separated into two fractions by chemical
leaching techniques, with the leachate expected to contain Pb of anthropogenic origin. Isotopic compositions of Pb and concentrations
of Pb, Sc, Mn, La, Yb, and Th were measured by quadrupole ICP-MS. The isotope ratios of leachable Pb in settling particles
were 207Pb/206Pb = 0.860 ± 0.001; 208Pb/206Pb = 2.116 ± 0.002 (mean ± 95% confidence intervals), which are similar to those of aerosols in China that are greatly affected
by pollution from coal combustion. We estimated the mean contribution from anthropogenic Pb sources to the Pb in settling
particles, using the conventional binary (anthropogenic and natural Pb) mixing equation for Pb isotopes, as 90% in the upper
trap and 78% in the lower trap. Furthermore, we found a significant negative correlation between the isotope ratios of Pb
and concentrations of leachable Mn, normalized to those of leachable Pb, suggesting that manganese oxides play an important
role in transporting Pb from the upper layers of the ocean to the deeper layers. Our results support the speculation published
in a previous study that Pb might be scavenged by Mn oxides in the Northwestern Pacific Ocean. 相似文献
142.
Daiki Nomura Toru Takatsuka Masao Ishikawa Toshiyuki Kawamura Kunio Shirasawa Hisayuki Yoshikawa-Inoue 《Estuarine, Coastal and Shelf Science》2009
Physico-chemical properties in the brine and under-ice water were measured in Saroma-ko Lagoon on the northeastern coast of Hokkaido, Japan, which is connected to the Sea of Okhotsk, during the period from mid-February through mid-March 2006. The brine within brine channels of the sea ice was collected with a new sampling method examined in this study. Salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), dissolved oxygen (DO), nutrients and oxygen isotopic ratio (δ18O) contained in the brine within brine channels of the sea ice and in the under-ice water varied largely in both time and space during the ice melt period, when discharge from Saromabetsu River located on the southeast of the lagoon increased markedly due to the onset of snow melting. The under-ice plume expands as far as 4.5 km from the river mouth at mid-March 2006, transporting chemical components supplied from the river into the lagoon. The under-ice river water was likely transported into the sea ice through well-developed brine channels in the sea ice due to upward flushing of water through brine channels occurred by loading of snowfalls deposited over the sea ice. These results suggest that the river water plume plays an important role in supplying chemical components into the sea ice, which may be a key process influencing the biogeochemical cycle in the seasonally ice-covered Saroma-ko Lagoon. 相似文献
143.
Latitudinal distribution of soil CO2 efflux and temperature along the Dalton Highway,Alaska 总被引:1,自引:1,他引:0
Yongwon Kim Seong-Deog Kim Hiroyuki Enomoto Keiji Kushida Miyuki Kondoh Masao Uchida 《Polar Science》2013,7(2):162-173
In this paper, we investigate spatial variations in soil CO2 efflux and carbon dynamics across five sites located between 65.5°N and 69.0°N in tundra and boreal forest biomes of Alaska. Growing and winter mean CO2 effluxes for the period 2006–2010 were 261 ± 124 (Coefficients of Variation: 48%) and 71 ± 42 (CV: 59%) gCO2/m2, respectively. This indicates that winter CO2 efflux contributed 24% of the annual CO2 efflux over the period of measurement. In tundra and boreal biomes, tussock is an important source of carbon efflux to the atmosphere, and contributes 3.4 times more than other vegetation types. To ensure that representativeness of soil CO2 efflux was determined, 36 sample points were used at each site during the growing season, so that the experimental mean fell within ±20% of the full sample mean at 80% and 90% confidence levels. We found that soil CO2 efflux was directly proportional to the seasonal mean soil temperature, but inversely proportional to the seasonal mean soil moisture level, rather than to the elevation-corrected July air temperature. This suggests that the seasonal mean soil temperature is the dominant control on the latitudinal distribution of soil CO2 efflux in the high-latitude ecosystems of Alaska. 相似文献
144.
Seung-On Hwang Song-You Hong Masao Kanamitsu 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(2):185-197
Impacts of the observing systems and meteorological parameters on a reanalyzed climatology are investigated using an assimilation algorithm based on the National Centers for Environmental Prediction/Department of Energy (NCEP/DOE) reanalysis system. The one-year analyzed climatology is generated in a standard analysis using all of the observations, which is named the control run. Additional climatology data sets are produced by selectively choosing observational systems or meteorological variables in the reanalysis system. It is found that the radiosonde-only observation is sufficient for reproducing the reanalysis climatology. Satellite observations have no significant contribution to the large-scale fields. The importance of meteorological variables on the analyzed climatology is temperature, wind, and moisture in that order, where the mass observation is found to have a greater impact on the analyzed climatology than wind. It is, however, noted that the moisture field demonstrates a profound influence on the surface hydroclimate such as cloud cover, radiation flux, and land surface temperature. 相似文献
145.
146.
Holocene glacial rebound and sea-level change in NW Europe 总被引:1,自引:0,他引:1
147.
Hiroyasu Ando Takeshi Noguchi Masao Nakagiri Akihiko Miyashita Yasumasa Yamashita Kyoji Nariai Hiroyoshi Tanabe 《Astrophysics and Space Science》1989,160(1-2):183-189
Two steps have been taken to decide at what place and altitude to set up the JNLT on Mauna Kea. First, the wind tunnel experiment has been made in collaboration with the Institute of Meteorology using the two models of summit area with the reduced scales of 1/1000 and 1/5000. This study tells us that the north-west cone is suitable for JNLT. Secondly, we have done the measurement of the microthermal activities in this area with a 30 m tower, which was continued for about 4 months in collaboration with the University of Hawaii. This experiment has given the mean vertical profile ofC
T
2
over 4 months and its scale height in the boundayr layer on our site. By use of these measurements, the contribution of the boundary layer to seeing is estimated. The behaviour ofC
T
2
under strong winds can be explained very well by topographic effects, which is in fairly good agreement with the results of our wind tunnel experiment.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988. 相似文献
148.
An analytical method for the determination of the roughness parameters over complex regions 总被引:1,自引:0,他引:1
The values of roughness length for momentum z
0and zero-plane displacement d
0over a hilly rough complex region with vegetation were evaluated without any assumption concerning z
0and d
0.It was found that for widely scattered profile data, the method of least squares will not give a reasonable result in determining the roughness parameters. For this purpose, the method of maximum correlation was introduced instead. This method gave a fair result for captive balloon observations conducted in hilly terrain mainly covered with forest in the northwestern part of the Kanto Plain, Japan. 相似文献
149.
The present study investigates the way an ocean filled with homogeneous warm water is cooled by prescribing cold water formation inside the ocean in the southern part of the southern hemisphere using multi-level numerical models. Cooling of the whole ocean starts with introduction of the cold water from the formation region into the deepest part of the ocean in the equatorial and eastern boundary regions by Kelvin wave-type density currents. The cold water along the eastern boundary extends westward as a Rossby wave-type density current setting up an interior poleward flow, and hits the western boundary to form a northward flowing boundary current in the northern hemisphere. Only then does the western boundary current cross the equator. Cooling of the rest of the ocean basin is accomplished by upwellings in the interior and also along the coasts. During this introduction the cold water is mixed with surrounding warm waters, and the thermocline, rather than forming just below the top level where heating is imposed, tends to spread down to deeper depths. Consequently the circulation at a steady state has a significant vertical structure such that the maximum upwelling in the interior occurs in the mid-depths, and only the deeper part of the deep ocean yields the Stommel and Arons circulation pattern. In the equatorial region higher vertical mode motions dominate, and a set of alternating zonal jets forms along the equator. 相似文献
150.
Responses of a four-legged offshore platform to wave forces are analysed by taking account of one torsional motion around the vertical axis which passes the centre of gravity of the structure, and two translational motions in the horizontal plane. Applying the spring-mass system with one degree-of-freedom to each mode of motion, a calculation method for predicting resultant dynamic displacements of the topdeck is developed. Both the inline force and the transverse force are considered as external forces. The calculated results are found to agree with experiments. Furthermore, the influence of seven important factors on the dynamic response is examined by the calculations. It is shown that the combination pattern of the direction factor of the transverse force is of importance in dynamic analysis. 相似文献