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321.
Modified Method for the Analysis of Nitrogen Isotopic Composition of Oceanic Nitrate at Low Concentration 总被引:1,自引:0,他引:1
A method for the determination of the δ15N of nitrate in seawater described by Cline and Kaplan (1975) has been modified for application to low-level nitrate samples.
We have minimized the reagent blank problem by replacing the Devarda's alloy with an aluminum reagent, and have also established
a procedure that yields quantitative (93 ± 2%) extraction of nitrogen even at low nitrate levels. Though the amounts and the
δ15N of the blank N varied from one reagent set to another, with these modifications, an overall N blank was reduced to approximately
0.80 ± 0.33 μmole N having an estimated δ15N value of −1.8‰. After blank and yield corrections, the measured isotopic composition of nitrate differed by approximately
0.1‰ from the actual value while the precision was within ±0.2‰ at the 1.25 μM level. The modified procedure was applied to
seawater samples collected from the equatorial Pacific in order to compare the N blanks in field samples with those derived
from laboratory experiments. The results support the suitability of the modified approach for isotopic analysis of oceanic
nitrate in shallow water.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
322.
Sediment trap experiments were carried out ten times in one year (1977) at three depths in Funka Bay. The material obtained in the traps was analyzed for metals, organic elements and radionuclides, together with the suspended matter in the overlying water column. Two groups with extremely different downward fluxes were found, a group with a small flux increasing with depth, and another with a large flux that is rather constant with depth and is observed only in winter. The flux in winter, and sometimes in the bottom layer below the summer thermocline was larger than the net sedimentation rate for total dry matter or for each chemical constituent. The flux was also larger than the net removal flux for 234Th. A most striking fact is that the specific activity of short-lived 234Th did not decrease in winter, indicating that the large flux in winter was not caused by the re-suspension of old bottom sediments. The concentration of suspended matter in winter was not much greater than that in other seasons. These results suggest that the downward flux observed in sediment trap experiments is not a net removal rate and that there must be an upward particulate flux in the bay. 相似文献
323.
Katsuhisa Tanaka Kazumaro Okamura Katsunori Kimoto Hiroshi Yagi Masashi Kodama 《Journal of Oceanography》2007,63(1):143-148
CDB-P (phosphorus extractable by the citrate-dithionite-bicarbonate extraction procedure) was used as the indicator of bio-available
inorganic P in the suspended and surface sediments in the inner part of Ariake Bay. The CDB-P pool of suspended and surface
sediments in the tidal flat area was estimated to be 10 ton and 90 ton, respectively (total of 100 ton), which corresponds
to 1.5 times the average dissolved inorganic phosphorus standing stock. During the summer periods of hypoxia, the CDB-P concentration
in the surface sediments decreased with the decline of Eh, losing 43–47% of the CDB-P observed in April. These results suggest
that the phosphorus dynamics have been affected by the decrease of resuspended sediment concentrations brought about by the
reduction of the tidal currents and phosphate release from the surface sediments during frequently occurring summer hypoxia
events. 相似文献
324.
Hiroshi Murakami Kosei Sasaoka Kohtaro Hosoda Hajime Fukushima Mitsuhiro Toratani Robert Frouin B. Greg Mitchell Mati Kahru Pierre-Yves Deschamps Dennis Clark Stephanie Flora Motoaki Kishino Sei-Ichi Saitoh Ichio Asanuma Akihiko Tanaka Hiroaki Sasaki Katsumi Yokouchi Yoko Kiyomoto Hiroaki Saito Cécile Dupouy Absornsuda Siripong Satsuki Matsumura Joji Ishizaka 《Journal of Oceanography》2006,62(3):373-393
The Global Imager (GLI) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) made global observations from 2 April
2003 to 24 October 2003. In cooperation with several institutes and scientists, we obtained quality controlled match-ups between
GLI products and in-situ data, 116 for chlorophyll-a concentration (CHLA), 249 for normalized water-leaving radiance (nLw) at 443 nm, and 201 for
aerosol optical thickness at 865 nm (Tau_865) and Angstrom exponent between 520 and 865 nm (Angstrom). We evaluated the GLI
ocean color products and investigated the causes of errors using the match-ups. The median absolute percentage differences
(MedPD) between GLI and in-situ data were 14.1–35.7% for nLws at 380–565 nm, 52.5–74.8% nLws at 625–680 nm, 47.6% for Tau_865, 46.2% for Angstrom, and 46.6%
for CHLA, values that are comparable to the ocean-color products of other sensors. We found that some errors in GLI products
are correlated with observational conditions; nLw values were underestimated when nLw at 680 nm was high, CHLA was underestimated
in absorptive aerosol conditions, and Tau_865 was overestimated in sunglint regions. The error correlations indicate that
we need to improve the retrievals of the optical properties of absorptive aerosols and seawater and sea surface reflection
for further applications, including coastal monitoring and the combined use of products from multiple sensors. 相似文献
325.
Clay mineral composition and geotechnical index properties of marine clays collected from Singapore, Korea, and Japan were investigated, and the correlation of clay mineral composition with the consistency limits and activity of the clays was examined. Predominant clay minerals were kaolinite for Singapore clay, kaolinite, vermiculite, and illite for Pusan clay, and smectite for Hachirogata and Ariake clay from Japan. The activity of clay indicates that Singapore clay is classified as normal or inactive, Pusan clay as normal, and Hachirogata and Ariake clays mostly as active. Significant positive correlations were found between smectite percentage in bulk soil and the liquid and plastic limits of the clays. 相似文献
326.
Relationships between biotic and abiotic factors and the ecological performance of late larval and juvenile flatfish in nursery grounds are examined from ecophysiological viewpoints. The first events in the nursery are metamorphosis and settlement. Development of organs, osmoregulation and behavioural changes during metamorphosis, and size at metamorphosis are regulated by environmental factors. Various hormones play critical roles in this regulation. Effects of environmental conditions on individual growth in the nursery grounds are described on the basis of Fry's five environmental factors: limiting, controlling, masking, directive and lethal factors. The main limiting factors are food and dissolved oxygen; controlling factors are temperature and body size; masking factors are salinity and pollutants; lethal factors are extreme environments; and directive factors are food, predators and dissolved oxygen. In addition to temperature, it has been indicated that dissolved oxygen seems to be relatively important for flatfish of the eastern US and northern European countries, while food abundance appears to be more critical for Japanese flounder. The feasibility is discussed of ecophysiological modelling to predict individual growth and subpopulation production based on the assessment of the role of environmental variability using the above classification, which organises and integrates environmental effects. 相似文献
327.
Conceptual model of the evolution of groundwater quality at the wet zone in Sri Lanka 总被引:2,自引:1,他引:1
The evolution of groundwater quality at a wet zone in Sri Lanka was made clear using field investigation, chemical and isotopic
analyses methods. In the wet zone, the concentrations of major ions and electrical conductivity (EC) in the groundwater are
low with small seasonal change. Except for sodium, silica and chloride, the EC and other major ion concentrations increase
along the groundwater flow direction. The contributions of bicarbonate and calcium ions to the increase in EC are the largest
among the major ions. The groundwater quality shows calcium-bicarbonate type, the initial stage of the Chebotarev series.
There is a seasonal change in isotopic composition. The isotopically lighter groundwater was found at the valley bottom in
the rainy season. Under the very heavy precipitation conditions, the slope of the regression line between δD and δ18O and deuterium excess for groundwater are close to 8 and 10, respectively. In other cases, the slopes of the regression lines
and deuterium excess are, less than 8 and 10, respectively.
Received: 5 August 1998 · Accepted: 19 October 1998 相似文献
328.
Yoshimasa Tanaka Atsuki Shinbori Tomoaki Hori Yukinobu Koyama Shuji Abe Norio Umemura Yuka Sato Manabu Yagi Satoru UeNo Akiyo Yatagai Yasunobu Ogawa Yoshizumi Miyoshi 《极地研究(英文版)》2013,(4):231-240
To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on the upper atmosphere has been developed by a Japanese inter-university project called the Inter-university Upper atmosphere Global Observation Network (1UGONET). The objective of this paper is to describe the infrastructure and tools developed by IUGONET. We focus on the data analysis software. It is written in Interactive Data Language (IDL) and is a plug-in for the THEMIS Data Analysis Software suite (TDAS), which is a set of IDL libraries used to visualize and analyze satellite- and ground-based data. We present plots of upper atmospheric data provided by IUGONET as examples of applications, and verify the usefulness of the software in the study of polar science. We discuss IUGONET's new and unique developments, i.e., an executable file of TDAS that can run on the IDL Virtual Machine, IDL routines to retrieve metadata from the IUGONET database, and an archive of 3-D simulation data that uses the Common Data Format so that it can easily be used with TDAS. 相似文献
329.
Hitoshi Tanaka Kosuke Kayane Mohammad Bagus Adityawan Min Roh Mohammad Farid 《Ocean Dynamics》2014,64(9):1319-1332
The relations of river morphology and tsunami propagation in rivers were studied at several rivers in the Tohoku region during The Great Chilean Tsunami of 2010 and The Great East Japan Tsunami of 2011. It was found that river mouth morphological features play an important role in the intrusion of low magnitude tsunamis in which the geological and geographical conditions are an important factor. Nevertheless, the effects of these features were not found in the case of an extreme tsunami wave. As the wave enters the river, the propagation depends on other factors. It was found that the intrusion distance correlates well to the riverbed slope. The measurements of water level and riverbed slope were analyzed to propose an empirical method for estimating the damping coefficient for the tsunami propagation in rivers based on the tsunami of 2011. The proposed empirical method was used to approximate the length of the tsunami intrusion into a river by assuming that the furthest distance is given for the ratio of local tsunami wave height to the tsunami wave height at the river entrance of 0.05 (5 %). The estimated intrusion length from the proposed method in this study shows a good comparison with measurement data. 相似文献
330.
Yasushi Ikebe Karen Leighly Yasuo Tanaka Takao Nakagawa Yuichi Terashima Stefanie Komossa 《Monthly notices of the Royal Astronomical Society》2000,316(2):433-441
We present new data taken at 850 μm with SCUBA at the James Clerk Maxwell Telescope for a sample of 19 luminous infrared galaxies. Fourteen galaxies were detected. We have used these data, together with fluxes at 25, 60 and 100 μm from IRAS , to model the dust emission. We find that the emission from most galaxies can be described by an optically thin, single temperature dust model with an exponent of the dust extinction coefficient ( k λ ∝ λ − β ) of β ≃1.4–2. A lower β ≃1 is required to model the dust emission from two of the galaxies, Arp 220 and NGC 4418. We discuss various possibilities for this difference and conclude that the most likely is a high dust opacity. In addition, we compare the molecular gas mass derived from the dust emission, M 850 μm , with the molecular gas mass derived from the CO emission, M CO , and find that M CO is on average a factor 2–3 higher than M 850 μm . 相似文献