全文获取类型
收费全文 | 527篇 |
免费 | 20篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 17篇 |
地球物理 | 127篇 |
地质学 | 179篇 |
海洋学 | 126篇 |
天文学 | 79篇 |
综合类 | 5篇 |
自然地理 | 22篇 |
出版年
2023年 | 4篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 29篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 3篇 |
2014年 | 23篇 |
2013年 | 22篇 |
2012年 | 12篇 |
2011年 | 17篇 |
2010年 | 21篇 |
2009年 | 25篇 |
2008年 | 25篇 |
2007年 | 31篇 |
2006年 | 26篇 |
2005年 | 31篇 |
2004年 | 10篇 |
2003年 | 16篇 |
2002年 | 7篇 |
2001年 | 18篇 |
2000年 | 10篇 |
1999年 | 22篇 |
1998年 | 14篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有557条查询结果,搜索用时 15 毫秒
121.
G. G. Katul R. Leuning J. Kim O. T. Denmead A. Miyata Y. Harazono 《Boundary-Layer Meteorology》2001,98(1):103-125
Source/sink strengths and vertical fluxdistributions of carbon dioxide within and above arice canopy were modelled using measured meanconcentration profiles collected during aninternational rice experiment in Okayama, Japan (IREX96). The model utilizes an Eulerian higher-orderclosure approach that permits coupling of scalar andmomentum transport within vegetation to infer sourcesand sinks from mean scalar concentration profiles; theso-called `inverse problem'. To compute the requiredvelocity statistics, a Eulerian second-order closuremodel was considered. The model well reproducedmeasured first and second moment velocity statisticsinside the canopy. Using these modelled velocitystatistics, scalar fluxes within and above the canopywere computed and compared with CO2eddy-correlation measurements above the canopy. Goodagreement was obtained between model calculations offluxes at the top of the canopy and measurements. Close to the ground, the model predicted higherrespiratory fluxes when the paddy was drained comparedto when it was flooded. This is consistent with thefloodwater providing a barrier to diffusion ofCO2 from the soil to the atmosphere. TheEulerian sources and flux calculations were alsocompared to source and flux distributions estimatedindependently using a Lagrangian Localized Near Fieldtheory, the first study to make such a comparison.Some differences in source distributions werepredicted by these analyses. Despite this, thecalculated fluxes by the two approaches compared wellprovided a closure constant, accounting for theinfluence of `near-field' sources in the Eulerian fluxtransport term, was given a value of 1.5 instead ofthe value of 8 found in laboratory studies. 相似文献
122.
Cao Shuyang Akira Nishi Kimitaka Hirano Shigehira Ozono Hiromori Miyagi Hiromori Kikugawa Yuji Matsuda Yasuo Wakasugi 《Boundary-Layer Meteorology》2001,101(1):61-76
An actively controlled wind tunnel equipped with multiple fansand airfoils has been developed, mainly for the purpose of reproducing the atmospheric boundary layer (ABL) for wind engineering applications. Various fluctuating flows can be achieved in this wind tunnel by altering the input data of the fans and airfoils through computer control. In this study, the ABL is physically simulated in this wind tunnel, and particular attention ispaid to the simulation of the profile of Reynolds stress. The method of generating the fluctuating flow and the experimental results of reproducing the ABL are presented. As the results show, the spatial distribution of Reynolds stress is satisfactorily simulated, and the profiles of other statisticalturbulent parameters, such as mean velocity, turbulent intensity, integral scale and power spectrum are successfully reproduced simultaneously. 相似文献
123.
Akira?NaganoEmail authorView authors OrcID profile Toshio?Suga Yoshimi?Kawai Masahide?Wakita Kazuyuki?Uehara Kyoko?Taniguchi 《Journal of Oceanography》2016,72(6):837-850
From the moored buoy observation at \(33.9^{\circ }\)N, \(144.9^{\circ }\)E south of the Kuroshio Extension (KE), we obtained Eulerian time series of dissolved oxygen concentration (DO) at 200, 400, and 600 m depths from June 2012 to March 2013. We observed ventilation by meso- and submesoscale processes that transport water southward across the KE jet. First, the cyclonic mesoscale eddy in June 2012 substantially depressed DO at depths of 400 and 600 m but maintained DO at 200 m, suggesting near-surface lateral transport of high-DO water derived from the north of the KE. Second, subduction of high-DO (>230 \({\upmu }\)mol kg\(^{-1}\)) water to a depth of 600 m was observed from early February to March 2013, associated with a mesoscale/submesoscale meandering of the KE jet. In mid-March 2013, shipboard hydrographic data were collected where the water mass at the mooring site would be advected by the eastward current on the southern flank of the KE. Based on these data, the subduction event was identified as an intrusion of an anomalously thick water mass from approximately 400–900 dbar. Ventilation of the subtropical mode water at a depth of 200 m around a subsurface DO maximum layer was detected as a rapid rise in DO in January 2013. This occurred after a significant seasonal decrease in DO at a rate of \(-0.130 \pm 0.007\) \({\upmu }\)mol kg\(^{-1}\) day\(^{-1}\) from July to December 2012. 相似文献
124.
Chemical, optical and X-ray powder data on coexisting anthophyllite and hornblende in an amphibolite are presented. Some chemical features of amphibole pairs are briefly discussed. 相似文献
125.
Ogawa Toshio Tanaka Yoshikazu Huzita Akira Yasuhara Michihiro 《Planetary and Space Science》1975,23(5):825-830
Three dimensional electric fields were measured at the altitude of about 27 km in the stratosphere over the Pacific Ocean about 200–400 km away from the Sanriku coast of Honsyu Island (L = 1·4) on 16–17 October 1973, which was magnetically disturbed. The average horizontal electric field thus measured is about 10 mV/m, and the electric field vectors made clockwise semidiurnal rotations rather than diurnal. Daily variation of this electric field was compared with data at L = 2·7–3·5 published by Mozer (1973) and was found to be very similar. This suggests that these electric fields are of common origin in the plasmasphere. From their mean daily variation it is estimated that the plasmaspheric convection is decreased in the night side and is increased in the day side by 200–300 m/sec, and there is an outward flow in the first half of the afternoon and an inward flow in the plasma bulge region of about 500 m/sec. 相似文献
126.
Diel changes in vertical distribution and feeding conditions of the chaetognath Parasagitta elegans (Verill) were observed in three regions of the subarctic North Pacific in the summer of 1997. Samples were collected by repeated vertical hauls with a Vertical Multiple Plankton Sampler (VMPS) for 15–45 hours by demarcating the 0–500 m water column into four sampling layers. Integrated abundance through the entire water column and the proportion of juveniles were higher in the Bering Sea than the western and eastern subarctic Pacific. Juveniles always inhabited the surface layer in the western subarctic Pacific and Bering Sea, but they inhabited the underlying layer in the eastern subarctic Pacific. Stages I–III concentrated into the upper 150 m in the western subarctic Pacific but were distributed widely from 20–300 m in the Bering Sea. Among them, Stages II and III migrated rather synchronously over a wide vertical range in the eastern subarctic Pacific. The feeding rate of P. elegans was calculated to be 0.18 prey/chaetognath/day in the western subarctic Pacific, 0.27 prey/chaetognath/day in the Bering Sea and 0.07 prey/chaetognath/day in the eastern subarctic Pacific. 相似文献
127.
Several numerical experiments were carried out on the formation of water masses and their fronts such as observed in the Kii Channel in winter. Such water masses and fronts may caused by density-induced current system. The phenomenon is assumed to take place in the vertical two-dimensional plane not involving the effect of the earth's rotation. The linear momentum equation and the diffusion-advection equations of salinity and temperature are integrated with respect to time under a vertically hydrostatic condition. The result is that two rolls which correspond to the onshore water mass and the offshore water mass are formed with an accompanying front between them. The apparent diffusion coefficient reaches a relatively great amount inside the water masses and drops down to the eddy diffusivity level at the front. The dependence of the synoptic distributions of the temperature and salinity on several parameters is also examined. Finally another experiment is carried out involving the effect of the earth's rotation, which results in a rather different distribution pattern from that of the non-rotating model. 相似文献
128.
A series of measurements of winds and wind-waves were carried out in wind-wave flumes. A data analysis based on the hypothesis
of local equilibrium yielded a new empirical formula on the controversial quantity of roughness heightz
0 over the water surface:
, where the nondimensional roughness height
is defined bygz
0/u
*
2 and the wave-wind parameterũ byω
p
u
*/g, g being the gravitational acceleration,u
* the friction velocity of air,ω
p
the peak frequency of wind-wave spectra. The obtained formula is compared with Charnock's (1955) and Toba's (1979) proposals;
is constant in the former and inversely proportional toũ in the latter. As in Toba's, this formula immediately leads to a practically important conclusion that the drag coefficientC
d
depends not merely on the usual variableU
10 (wind velocity at 10m height over the water surface), but also on the surface state represented by wind-waves. An explicit
expression is provided for the drag coefficient incorporating the wave-wind parameter; it covers the range ofC
d
calculated from most of the previous drag formulas, by varying the wave-wind parameter. 相似文献
129.
Influence of Salinity on pH and Aluminum Concentration on the Interaction of Acidic Red Soil with Seawater 总被引:1,自引:0,他引:1
Mohamed?M.?Kombo Said?A.?Vuai Maki?Ishiki Akira?TokuyamaEmail author 《Journal of Oceanography》2005,61(3):591-601
Contamination of acidic red soil in the coastal areas of Okinawa Islands is a serious environmental problem. This study was conducted to examine the effects of the salinity on pH and aluminum concentration when the acidic red soil interacts with seawater. Acidic red soil from Gushikawa recreation center was fractionated into bulk soil, coarse sand and silt + clay. Different weights of each fraction were equilibrated with seawater solutions. The pH and concentrations of Al3+, Na+, K+, Ca2+ and Mg2+ were then analyzed in the extracts. The results showed a decreasing trend of pH with increasing soil to solution ratio while the extracted Al3+ revealed an increasing trend. The lowest pH values were 3.85, 4.06, 4.41, 4.66 and their corresponding highest Al3+ concentrations were 2.50, 1.01, 0.062 and 0.036 mmolL−1 in the seawater extracts, one-tenth seawater extracts, one-hundredth seawater extracts and one-thousandth seawater solution extracts, respectively. Mostly, the concentrations of Na+, Ca2+, Mg2+ and especially K+ decreased with increasing soil weight in the high salinities but showed the opposite trend in the low salinity samples. Potassium concentration decreased by 39%, 53% and 40% in the seawater extracts, one-tenth and one-hundredth seawater extracts but increased by 200% in one-thousandth seawater extracts. The coincidence of the increase in Al3+ and H+ concentrations, and the decrease of Na+, K+, Ca2+ and Mg2+ concentrations in the solutions suggests ion exchange/adsorption, while the increased patterns, particularly at low salinity could be attributed to the dissolution of the species from the soils. 相似文献
130.