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151.
Nakajima H. Shimada Y. Somekawa T. Fujita M. Tanaka K.A. 《Geoscience and Remote Sensing Letters, IEEE》2009,6(4):718-722
Conventional ground-penetrating radar (GPR) requires large-aperture antennas or long-span measurements to survey a remote location precisely. We propose a laser-driven GPR (LGPR) as a new detection method. LGPR uses microwaves from laser-produced plasmas as remote transmitters and can survey a remote location using a compact instrument. We performed numerical simulations to investigate the radiation mechanism of microwaves from laser plasmas and confirmed the pulsewidth of the laser suitable for LGPR. Experiments with subnanosecond pulse lasers clarified the feasibility and detection performance of LGPR. 相似文献
152.
153.
Variation of precipitation δ18O in Langtang Valley Himalayas 总被引:1,自引:0,他引:1
The variation of the δ18O in precipitation and the relationship with precipitation amount at Kyangjin Base House and Yala Glacier Camp in Langtang
Valley, Nepal Himalayas were analyzed. The variations of the δ18O with precipitation had great scatter, and the correlations between the δ18O and precipitation changed with time on the synoptic scale. On the seasonal scale, there was marked amount effect at Kyangjin
Base House. However, the δ18O-precipitation gradient was smaller than that on the synoptic scale. Because of the maintenance of the basic equilibrium
between stable isotopic compositions in atmospheric vapor and precipitation, the evaporation enrichment was light during the
rainy season. Therefore, the variation of stable isotopic compositions in precipitation was independent on the sampling intervals.
Simulations show that the rainfall in Langtang Valley was not the outcome of the initial condensation of ocean vapor that
originated from low latitudes. The stable isotopic compositions in precipitation were greatly depleted due to the strong rainout
of the vapor from oceans as the vapor was raised over the Himalayas. 相似文献
154.
Steven Emerson Yutaka W. Watanabe Tsuneo Ono Sabine Mecking 《Journal of Oceanography》2004,60(1):139-147
We present a compilation of apparent oxygen utilization (AOU) changes observed in the upper pycnocline of the North Pacific
Ocean over the last several decades. The goal here is to place previously-published data in a common format, and assess the
causes of the observed changes. The general trend along repeat cross sections of the eastern and western subtropical ocean
and the subarctic ocean is an increase in AOU from the mid 1980s to the mid 1990s. AOU has also been increasing in a time-series
study in the northwest subarctic Ocean off of Japan since the late 1960s. Observed AOU changes south of 35°N in the subtropical
ocean are 10–20 μmol kg−1, with much greater changes, reaching 60–80 μmol kg−1 in isolated areas, in the subtropical/subarctic boundary and the subarctic ocean. Analysis of changes in both AOU and salinity
on isopycnals suggests that there are significant salinity-normalized increases that must be due to alteration in the rate
of ventilation or organic matter degradation. A common feature in the data is that the maximum increase in AOU is centered
near the density horizon σθ= 26.6. Time series results from the Oyashio Current region near the winter outcrop area of this density horizon indicate
that surface waters there have become fresher with time, which may mean this density surface has ceased to outcrop in the
latter decades of the 20th century. Whether this is due to natural decadal-scale changes or anthropogenic influences can be
decided by determining future trends in AOU on these density surfaces.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
155.
Masahide?WakitaEmail author Shuichi?Watanabe Yutaka?W.?Watanabe Tsuneo?Ono Nobuo?Tsurushima Shizuo?Tsunogai 《Journal of Oceanography》2005,61(1):129-139
The dissolved inorganic carbon (DIC) and related chemical species have been measured from 1992 to 2001 at Station KNOT (44°N, 155°E) in the western North Pacific subpolar region. DIC (1.3∼2.3 µ mol/kg/yr) and apparent oxygen utilization (AOU, 0.7∼1.8 µmol/kg/yr) have increased while total alkalinity remained constant in the intermediate water (26.9∼27.3σθ). The increases of DIC in the upper intermediate water (26.9∼27.1σθ) were higher than those in the lower one (27.2∼ 27.3σθ). The temporal change of DIC would be controlled by the increase of anthropogenic CO2, the decomposition of organic matter and the non-anthropogenic CO2 absorbed at the region of intermediate water formation. We estimated the increase of anthropogenic CO2 to be only 0.5∼0.7 µmol/kg/yr under equilibrium with the atmospheric CO2 content. The effect of decomposition was estimated to be 0.8 ± 0.7 µmol/kg/yr from AOU increase. The remainder of non-anthropogenic CO2 had increased by 0.6 ± 1.1 µmol/kg/yr. We suggest that the non-anthropogenic CO2 increase is controlled by the accumulation of CO2 liberated back to atmosphere at the region of intermediate water formation due to the decrease of difference between DIC in the winter mixed layer and DIC under equilibrium with the atmospheric CO2 content, and the reduction of diapycnal vertical water exchange between mixed layer and pycnocline waters. In future, more accurate and longer time series data will be required to confirm our results. 相似文献
156.
Cultures of six marine phytoplankton were grown at ammonium concentrations ranging up to 200 μg-atom NH4---N litre−1. Only the growth of dinoflagellates, Gymnodinium splendens and Gonyaulax polyedra was inhibited at the two highest concentrations used. In 3-h photosynthetic 14CO2 uptake experiments, only Gymnodinium was inhibited at concentrations of NH4---N greater than 100 μg-atom litre−1. We conclude that the increased ammonium concentrations found near Southern California sewage outfalls would not be inhibiting to phytoplankton in the vicinity of such outfalls. 相似文献
157.
Masayuki Takahashi Toshisuke Nakai Takashi Ishimaru Hiroshi Hasumoto Yoshihiko Fujita 《Journal of Oceanography》1985,41(2):73-80
Continuous distribution of the subsurface chlorophyll maximum (SCM) was confirmed in the Kuroshio and neighbouring areas in observations at 15 to 40 km intervals. Chlorophyll amounts occurring in and immediately around the SCM constituted 60 to 80% of the total chlorophyll in the water column above the 1% light level. The SCM zone received 1 to 10% of the surface irradiance at its center and contained sufficient macronutrients to support approximately one doubling of the existing phytoplankton biomass at most stations. There were several stations where there were higher nutrient concentrations that would support more than one doubling of the existing biomass around the SCM zone, and this was interpreted as resulting from uplift of the SCM zone due to upwelling. 相似文献
158.
Photosynthetic pigment system of picophytoplankton of cyanophytes was examined with five strains isolated from the Kuroshio
water at the depth of 70 m. Examination was made for the absorption spectra of intact cells of each strain. Analysis of pigment
composition was also made withSynechococcus NIBB 1059 and 1071, which were isolated from surface waters of the Gulf Stream and Kuroshio area, respectively. Results indicated
that (1) all strains contain phycoerythrin with a very high concentration, and (2) the phycoerythrin in these strains contains
two chromophores, phycoerythrobilin and phycourobilin, and (3) a large abundance of phycoerythrin and phycourobilin in the
phycoerythrin enablesSynechococcus picophytoplankton to absorb effectively the light in the blue-green region at the subsurface depth. These characteristics
suggest that cyanophytes in the subsurface water can collectt the blue-green light and perform actively photosynthesis even
at the bottom of euphotic layer. 相似文献
159.
Eguchi Takao Fujinawa Yukio Fujita Eisuke Iwasaki Sin-Iti Watabe Isao Fujiwara Hiroyuki 《Marine Geophysical Researches》1998,20(2):73-94
We installed a real-time operating regional observation network of Ocean-Bottom-Seismometers, connected to an electro-optical fiber communication cable, at the Sagami trough subduction zone, just south of the Tokyo metropolitan area, central Japan. The network, called ETMC, has six seismic observation sites at approximately 20 km spacing. In addition, there are three tsunami observation sites along the ETMC network to monitor the propagation process of tsunamis around the Sagami trough region.The on-line data from the ETMC has been improving the detection capability of smaller-magnitude earthquakes even at areas close to the margin of the trough. The ETMC data analyzing system, which has a function of real-time digital filtering for each seismic channel, can read the arrival times of P- and S-waves precisely, constraining well the automatic on-line hypocenter locations. The network has been providing useful information regarding the bending and downgoing process of the Philippine sea plate at the Sagami trough subduction zone.The pressure sensors of the installed network have a detection capability of tsunami wave trains with an amplitude of less than 1 cm. For example, the sensors recorded the full time history of tsunami wave trains, with mm order resolution, originating from a tsunami earthquake with 5.7 MW and the tsunami magnitude of 7.5 occurred near Tori Shima (Tori Is.) of the Izu-Bonin Is. arc on September 4, 1996. The maximum amplitude of the tsunami signals on the trough-floor was approximately 1 cm (P-P), in contrast with approximately 20 cm (0-P) at a coastal site on Izu-Oshima, near the trough. Also, the pressure sensors observed tsunamis due to a large tsunami earthquake (7.1 MW) at the northern New Guinea, on July 17, 1998. 相似文献
160.
Photographic observations of the brittle starOphiura sarsi were conducted at a depth of approximately 280 m in the Pacific Ocean off tsuchi, northeastern Japan. Bottom photographs showed that this ophiuroid occurred in high densities, uniformly covering the sea floor and that other megafauna was rare. The mean density and biomass of ophiuroids in the dense bed were estimated to be 373 m–2 and 124 g m–2, respectively. Ophiuroids comprised 99% of all megabenthic organisms in terms of number of individuals, and megafaunal assemblage of the dense bed showed very low species diversity.O. sarsi exhibited a regular spatial pattern avoiding contact with conspecific neighbors. This regular spatial pattern was disrupted by certain other organisms, around which halo-like, bare areas were observed. The size and shape of these halo-like areas varied and were apparently related to the body size and/or motility of the organisms. In the present observation areaO. sarsi covered 96% of the sea bottom, and the remaining 4% was occupied by other organisms and their halo-like bare areas. 相似文献