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71.
72.
The existence of an oxygen exosphere and ionosphere in Saturn’s main ring region has been confirmed by the Saturn Orbital Insertion (SOI) observations of the Cassini spacecraft. Through the ion-molecule collisions, the ring atmosphere could serve as a source of ions throughout Saturn’s magnetosphere. If photolysis of ice in the main rings is the dominant source of O2, then the complex structure of the ring atmosphere/ionosphere and the injection rate of neutral O2 will be subject to modulation by the seasonal variation of Saturn along its orbit (Tseng, Wei-Ling, Ip, W.-H., Johnson, R.E., Cassidy, T.A., Erlod, M.K. [2010]. Icarus 206, 382-389). In addition, the radio and plasma wave science (RPWS) instrument onboard Cassini found that a large amount of the Enceladus-originated water-group plasma would be deposited on the outer edge of the A ring (Farrell, W.M., Kaiser, M.L., Gurnett, D.A., Kurth, W.S., Persoon, A.M., Wahlund, J.E., Canu, P. [2008]. Geophys. Res. Lett. 35, L02203). A large amount of Enceladus’ plume neutrals (water-group neutrals) would collide with the main rings through collisional interaction with the ambient neutrals and plasma ions (Jurac, S., Richardson, J.D. [2007]. Geophys. Res. Lett. 34, L08102; Cassidy, T.A., Johnson, R.E. [2010]. Icarus, in press). These absorbed ions and neutrals could be recycled to neutral oxygen molecules via grain-surface chemistry to contribute the ring oxygen atmosphere. In this work, we have examined the mass budget of the ring oxygen atmosphere of Saturn taking into account such an “exogenic” source. The maximum O2 source rate from recycling of Enceladus-originated plasma and neutrals is probably comparable or higher to the one from photolytic decomposition of ices. In the above case, the neutral O2 source rate would be independent of the solar insolation angle. Therefore, even at Saturn’s Equinox, the extended oxygen atmosphere still could be an important supplier of oxygen ions in the saturnian magnetosphere. We have performed several studies for different recycling source rates from Enceladus. These predictions need further the Cassini Plasma Spectrometer (CAPS) and the Magnetospheric Imaging Instrument (MIMI) observations to be verified in future. 相似文献
73.
Estimation of effective aquifer hydraulic properties from an aquifer test with multi-well observations (Taiwan) 总被引:1,自引:0,他引:1
Jet-Chau Wen Cheng-Mau Wu Tian-Chyi J. Yeh Chung-Ming Tseng 《Hydrogeology Journal》2010,18(5):1143-1155
The representative anisotropic parameters for an aquifer located at the campus of the National Yunlin University of Science and Technology in Taiwan have been acquired. A constant-rate pumping test was carried out, and drawdown-time data were collected from ten observation wells. Applications of the conventional aquifer test analysis, which assumes aquifer homogeneity for each observed well hydrograph, yielded spatially varying transmissivity and storage coefficient estimates, contradicting the homogeneous assumption. A direct approach and a nonlinear-least squares minimization of distance-drawdown data were then employed to analyze anisotropy of the transmissivity of an equivalent homogeneous aquifer. Results show that the direction and values of anisotropic transmissivities vary with time and the estimates depend on the number of observation wells used. These field results are consistent with results from recent theoretical investigations which questioned the suitability of the conventional aquifer test analysis. 相似文献
74.
Chien-Yuan Chen Lien-Kuang Chen Fan-Chieh Yu Sheng-Chi Lin Yu-Ching Lin Chou-Lung Lee Yu-Ting Wang 《Environmental Earth Sciences》2010,59(8):1693-1702
Typhoons Aere (2004) and Matsa (2005) caused high nephelometric turbidity in the Shihmen reservoir in northern Taiwan, jeopardizing
the operation of the reservoir for several days, and ultimately impacting the living conditions and economy of the downstream
residents. The torrential rains caused landslides and debris flows in upland areas, and flowed into riverbeds, likely contributing
significantly to the suspended sediment yields in the reservoir. This investigation elucidates how upland landslides affect
sediment attributes in the reservoir basin. Study methods including field observations, spatial analysis in GIS and aerial
photo interpretation are adopted to trace the sediment sources and contributing factors to the landslide. Torrential rains
induced landslides and debris-flows upland, causing river incisions and soil erosion in landslide areas lacking vegetation.
These factors, together with the conditions of the engineered structures and geologic vulnerabilities of the area, caused
suspended sediment yield in the reservoir. The high nephelometric turbidity could potentially reoccur, with masses of landslide-derived
sediment remaining upland and in the riverbed. 相似文献
75.
A spectral method to investigate the effect of Fe3+, Fe2+ on the thermostability of phycocyanin (PC) ofSpirulina maxima showed that iron ions provent decrease of visible light absorbance and fluorescence intensity of PC. Increase in denaturation temperature caused by Fe3+ was observed by the micro-differential scanning calorimetric method. All results showed iron ions maintain the aggregation stability of the PC. The absorption spectrum of phycocyanobilin (PCB, a prosthetic group of PC) with Fe3+ in chloroform was quite different from that of free PCB.
相似文献76.
CCC plasmid was isolated from an economically important blue-green alga —Spirulina platensis (1.7×106 dalton from the S6 strain and 1.2×106 dalton from the F3 strain) using a rapid method based on ultrasonic disruption of algal cells and alkaline removal of chromosomal DNA. The difference
in the molecular weight of the CCC DNAs from the two strains differing in form suggests that plasmid may be related with the
differentiation of algal form. This modified method, which does not use any lysozyme, is a quick and effective method of plasmid
isolation, especially for filamentous blue-green algae.
Contribution No. 79 of the Experimental Marine Biology Laboratory and 2153 of the Institute of Oceanology, Academia Sinica.
This research was supported in part by The President of the Chinese Academy of Sciences Foundation. 相似文献
77.
The excitation energy transfer from phycobiliproteins to thylakoid PSII of higher plants was investigated. When incubated
with spinach thylakoids, phycobiliproteins isolated from red and blue-green algae transferred light energy absorbed to spinach
PSII. The efficiency of energy transfer was dependent on the kind of phycobiliproteins used. If spinach thylakoids were replaced
by the thylakoids ofBrassica chinensis, R-phycoerythin or C-phycocyanin did not transfer their excitation energy to PSII ofBrassica chinensis unless allophycocyanin was present.
Contribution No. 69 from the Experimental Marine Biology Laboratory IOAS. 相似文献
78.
Toxicity assessments of nanoscale zerovalent iron and its oxidation products in medaka (Oryzias latipes) fish 总被引:1,自引:0,他引:1
Iron-based nanotechnologies are increasingly used for environmental remediation; however, toxicologic impacts of iron nanoparticles on the aquatic ecosystem remain poorly understood. We treated larvae of medaka fish (Oryzias latipes) with thoroughly characterized solutions containing carboxymethyl cellulose (CMC)-stabilized nanoscale zerovalent iron (nZVI), aged nanoscale iron oxides (nFe-oxides) or ferrous ion (Fe[II]) for 12-14 days' aqueous exposure to assess the causal toxic effect(s) of iron NPs on the fish. With the CMC-nZVI solution, the dissolved oxygen level decreased, and a burst of reactive oxygen species (ROS) was generated as Fe(II) oxidized to ferric ion (Fe[III]); with the other two iron solutions, these parameters did not significantly change. CMC-nZVI and Fe(II) solutions caused acute lethally and sublethally toxic effects in medaka larvae, with nFe-oxide-containing solutions causing the least toxic effects. We discuss modes of toxic action of iron NPs and chronic toxic effects in terms of hypoxia, Fe(II) toxicity and ROS-mediated oxidative damage. 相似文献
79.
High rates of urbanization, environmental degradation, and industrial development in disaster-prone areas have all served to increase the extent of damage following catastrophes. Recently, losses from environmental hazards have escalated, which has resulted in a noticeable change in policy, with more emphasis on loss reduction through mitigation, preparedness, and recovery programs. This study focuses on natural disaster management in which the direct risks are posed by the natural disasters themselves. This paper presents a review of issues surrounding natural disaster risk control and insurance in Taiwan. It proposes the use of background information concerning risk control strategies as well as earthquake, typhoon, and flood insurance in Taiwan. Finally, an insurance case study is utilized to demonstrate the feasibility of the proposed methodology. 相似文献
80.
Southern California is an increasingly urbanized hotspot for surfing, thus it is of great interest to assess the human illness risks associated with this popular ocean recreational water sport from exposure to fecal bacteria contaminated coastal waters. Quantitative microbial risk assessments were applied to eight popular Southern California beaches using readily available enterococcus and fecal coliform data and dose-response models to compare health risks associated with surfing during dry weather and storm conditions. The results showed that the level of gastrointestinal illness risks from surfing post-storm events was elevated, with the probability of exceeding the US EPA health risk guideline up to 28% of the time. The surfing risk was also elevated in comparison with swimming at the same beach due to ingestion of greater volume of water. The study suggests that refinement of dose-response model, improving monitoring practice and better surfer behavior surveillance will improve the risk estimation. 相似文献