全文获取类型
收费全文 | 767篇 |
免费 | 18篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 42篇 |
地球物理 | 176篇 |
地质学 | 190篇 |
海洋学 | 229篇 |
天文学 | 112篇 |
综合类 | 4篇 |
自然地理 | 42篇 |
出版年
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 13篇 |
2016年 | 20篇 |
2015年 | 12篇 |
2014年 | 19篇 |
2013年 | 26篇 |
2012年 | 23篇 |
2011年 | 34篇 |
2010年 | 34篇 |
2009年 | 38篇 |
2008年 | 37篇 |
2007年 | 40篇 |
2006年 | 49篇 |
2005年 | 37篇 |
2004年 | 55篇 |
2003年 | 27篇 |
2002年 | 22篇 |
2001年 | 25篇 |
2000年 | 16篇 |
1999年 | 8篇 |
1998年 | 21篇 |
1997年 | 11篇 |
1996年 | 17篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1973年 | 7篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 3篇 |
排序方式: 共有802条查询结果,搜索用时 15 毫秒
241.
Charcoal column chromatography and a dialysis system using a Visking tube were used for the concentration and separation of dissolved carbohydrates in seawater. Recoveries of mono-, oligo-, and polysaccharides were 46–74, 61–89 and 70%, respectively, relative to the total amount of sugars initially submitted to analysis. The combined charcoal column chromatography and dialysis system was used to separate dissolved carbohydrates in seawater samples from Mikawa Bay into mono-, oligo- and polysaccharide fractions. The polysaccharides are separated into two fractions with molecular weights of <4,000 and >4,000 using Sephadex G-25 column chromatography. Monosaccharides, oligosaccharides, polysaccharides with M.W.<4,000 and polysaccharides with M.W. >4,000 accounted for 7–9, 15–26, 7–13 and 20–33% of total dissolved carbohydrates, respectively. However, 32–38% of dissolved carbohydrates were lost during the analytical procedures. Glucose, galactose, mannose, xylose, arabinose, ribose, fucose, and rhamnose were found upon acid hydrolysis of the oligo- and polysaccharide fractions, while fucose and rhamnose were not present in the monosaccharide fraction. Possible sources of the carbohydrates in these fractions are discussed with reference to the monosaccharide composition of cellular carbohydrate in marine algae. 相似文献
242.
Yutaka?W.?WatanabeEmail author Hiroshi?Ishida Toshiya?Nakano Naoki?Nagai 《Journal of Oceanography》2005,61(6):1011-1016
Using time series of hydrographic data in the wintertime and summertime obtained along 137°E from 1971 to 2000, we found that
the average contents of nutrients in the surface mixed layer showed linear decreasing trends of 0.001∼0.004 μmol-PO4 l−1 yr−1 and 0.01∼0.04 μmol-NO3 l−1 yr−1 with the decrease of density. The water column Chl-a (CHL) and the net community production (NCP) had also declined by 0.27∼0.48
mg-Chl m−2 yr−1 and 0.08∼0.47 g-C-NCP m−2 yr−1 with a clear oscillation of 20.8±0.8 years. These changes showed a strong negative correlation with the Pacific Decadal Oscillation
Index (PDO) with a time lag of 2 years (R = 0.89 ± 0.02). Considering the recent significant decrease of O2 over the North Pacific subsurface water, these findings suggest that the long-term decreasing trend of surface-deep water
mixing has caused the decrease of marine biological activity in the surface mixed layer with a bidecadal oscillation over
the western North Pacific. 相似文献
243.
Shinsuke Tanabe Ryo Tatsukawa Masahide Kawano Hideo Hidaka 《Journal of Oceanography》1982,38(3):137-148
Concentrations of chlorinated hydrocarbons such as HCH isomers and DDT compounds were determined in air and surface water samples taken from the Western Pacific, Eastern Indian and Antarctic Oceans. The most interesting finding was their presence in measurable concentrations in the Antarctic Ocean. Chlorinated hydrocarbon pesticides are widely distributed in the open ocean environment over both the northern and southern hemispheres, and some characteristic distribution patterns of pesticide species in different oceanic regions were observed both in air and water samples. HCH residues found in the northern hemisphere were much higher in concentration than those in the southern hemisphere. On the other hand, higher concentrations of DDT residues were found in the tropical regions, but their levels were not so different between both the northern and southern hemispheres. HCH isomers found in the northern hemisphere had the following order of concentrations:-HCH> HCH>-HCH, while in the southern hemisphere-HCH was apparently dominant. DDT compound compositions were rather uniform in all the oceans surveyed, and more than 50% wasp,p-DDT. These facts can be explained by the world wide situation regarding pesticide use and the physicochemical properties of the pesticides such as their vapor pressures and water solubilities. In addition, the meridional circulation of the atmosphere, particularly the mass flows of the Hadley and Ferrel cells in the troposphere, also contributes to the atmospheric transport and global distribution of these pesticides. 相似文献
244.
245.
The microwave backscattering from wind-wave surfaces is observed in a windwave tunnel under various conditions of the wind and wind waves, and its statistical features are investigated. The dependence of the backscattered power on the wind speed and the incident angle shows similar features to those predicted by models proposed previously. However, the dependence of the backscattered power on the incident angles also corresponds to the asymmetrical feature of the wind-wave surfaces with respect to the wind direction. The spectral analyses of time series of the backscattered intensity show that the propagating speed of fine structures of the wind-wave surface contributing to the backscattering at large incident angles does not coincide with the phase speed of the freely propagating Braggwaves. Atupwind incidence, the surface structures of wind waves contributing to the backscattering propagates with the dominant waves at their phase speed. This result is inconsistent with the two-scale model in which the Bragg waves are simply superimposed on longer waves, but is consistent with the results of optical observation by Ebuchiet al. (1987). At downwind incidence, the propagating speed is slower than the phase speed of the dominant waves. 相似文献
246.
Hiroshi Kuroda Manabu Shimizu Yuuichi Hirota Daisuke Ambe Hideki Akiyama 《Journal of Oceanography》2008,64(1):81-91
In order to specify a vertical thermal structure related to surface current variation on the continental slope in Tosa Bay,
Japan, we analyzed monthly regular hydrographic measurements in the years 1991–2004. Subsurface temperature below 200 m on
the slope was found to vary synchronously with the vertical displacement of the main thermocline around 200 m. It is shown
that the vertical-averaged temperature below 200 m is significantly correlated with an along-isobath/southwestward surface
current velocity on the slope. This correlation indicates that when a strong (weak) southwestward surface current is observed,
temperature below 200 m decreases (increases) simultaneously, that is, isotherms below the 200 m are displaced upward (downward)
together with the main thermocline. Moreover, when the strong southwestward flow is detected, across-isobath isotherms around
200 m slope upward toward the offshore direction. Furthermore, it is suggested that as the Kuroshio axis moves offshore south
of the bay, the southwestward flow tends to be weakened by the combined effect of other Kuroshio parameters such as transport
and stream width as well as the Kuroshio axis position. As a result, it is inferred that the correlation between the surface
current and subsurface temperature can be interpreted in terms of the formation and decay of an anticlockwise circulation
interacting with a cold eddy. 相似文献
247.
Sea surface temperature observation by Global Imager (GLI)/ADEOS-II: Algorithm and accuracy of the product 总被引:1,自引:0,他引:1
Futoki Sakaida Kohtaro Hosoda Masao Moriyama Hiroshi Murakami Akira Mukaida Hiroshi Kawamura 《Journal of Oceanography》2006,62(3):311-319
A sea surface temperature (SST) retrieval algorithm for Global Imager (GLI) aboard the ADEOS-II satellite has been developed.
The algorithm is used to produce the standard SST product in the Japan Aerospace Exploration Agency (JAXA). The algorithm
for cloud screening is formed by combinations of various types of tests to detect cloud-contaminated pixels. The combination
is changed according to the solar zenith angle, which enables us to detect clouds even in the sun glitter region in daytime.
The parameters in the cloud-detection tests have been tuned using the GLI global observations. SST is calculated by the Multi-Channel
SST (MCSST) technique from the detected clear pixels. Using drifting buoy measurements, match-up data are produced to derive
the coefficients of the MCSST equations and to examine their performance. The bias and RMSE of the GLI SST are 0.03 K and
0.66 K for daytime and, −0.01 K and 0.70 K for nighttime, respectively. 相似文献
248.
Estimating the Kuroshio Axis South of Japan Using Combination of Satellite Altimetry and Drifting Buoys 总被引:3,自引:4,他引:3
Daisuke Ambe Shiro Imawaki Hiroshi Uchida Kaoru Ichikawa 《Journal of Oceanography》2004,60(2):375-382
By tracking the locally strongest part of the sea-surface velocity field, which was obtained by integrating data of satellite
altimeters and surface drifting buoys, we extracted the Kuroshio axis south of Japan every 10 days from October 1992 to December
2000. The obtained axes clearly express the effect of the bottom topography; three modes were observed when the Kuroshio ran
over the Izu Ridge. The axis was very stable to the south of ‘Tosa-bae,’ off the Kii Channel. Mean current speed at the Kuroshio
axis gradually increased from 0.65 m/s south of Kyushu to 1.45 m/s off Enshu-nada.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
249.
Takeshi Yoshimura Koji Suzuki Hiroshi Kiyosawa Tsuneo Ono Hiroshi Hattori Kenshi Kuma Jun Nishioka 《Journal of Oceanography》2013,69(5):601-618
Response of phytoplankton to increasing CO2 in seawater in terms of physiology and ecology is key to predicting changes in marine ecosystems. However, responses of natural plankton communities especially in the open ocean to higher CO2 levels have not been fully examined. We conducted CO2 manipulation experiments in the Bering Sea and the central subarctic Pacific, known as high nutrient and low chlorophyll regions, in summer 2007 to investigate the response of organic matter production in iron-deficient plankton communities to CO2 increases. During the 14-day incubations of surface waters with natural plankton assemblages in microcosms under multiple pCO2 levels, the dynamics of particulate organic carbon (POC) and nitrogen (PN), and dissolved organic carbon (DOC) and phosphorus (DOP) were examined with the plankton community compositions. In the Bering site, net production of POC, PN, and DOP relative to net chlorophyll-a production decreased with increasing pCO2. While net produced POC:PN did not show any CO2-related variations, net produced DOC:DOP increased with increasing pCO2. On the other hand, no apparent trends for these parameters were observed in the Pacific site. The contrasting results observed were probably due to the different plankton community compositions between the two sites, with plankton biomass dominated by large-sized diatoms in the Bering Sea versus ultra-eukaryotes in the Pacific Ocean. We conclude that the quantity and quality of the production of particulate and dissolved organic matter may be altered under future elevated CO2 environments in some iron-deficient ecosystems, while the impacts may be negligible in some systems. 相似文献
250.
Shinpei Yoshitake Masaki Uchida Toshiyuki Ohtsuka Hiroshi Kanda Hiroshi Koizumi Takayuki Nakatsubo 《Polar Science》2011,5(3):391-397
The distribution of organic carbon and its relationship to vegetation development were examined on a glacier foreland near Ny-Ålesund, Svalbard (79°N). In a 0.72-km2 area, we established 43 study plots on three line transects along primary succession from recently deglaciated area to old well-vegetated area. At each plot, we measured the type and percent coverage of vegetation types. The organic carbon content of vegetation, organic soil, and mineral soil samples was determined based on their organic carbon concentration and bulk density. Cluster analysis based on vegetation coverage revealed five types of ground surfaces representing variations in the amounts and allocation patterns of organic carbon. In the later stages of succession, 7%–24% and 31%–40% of organic carbon was contained in the organic and deeper soil layers, respectively. Organic carbon storage in the later stages of succession ranged from 1.1 – 7.9 kg C m−2. A larger amount of organic carbon, including ancient carbon in a raised beach deposit, was expected to be contained in much deeper soil layers. These results suggest that both vegetation development and geological history affect ecosystem carbon storage and that a non-negligible amount of organic carbon is distributed in this High Arctic glacier foreland. 相似文献