全文获取类型
收费全文 | 693篇 |
免费 | 25篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 61篇 |
地球物理 | 136篇 |
地质学 | 185篇 |
海洋学 | 203篇 |
天文学 | 92篇 |
综合类 | 6篇 |
自然地理 | 33篇 |
出版年
2024年 | 2篇 |
2022年 | 2篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 16篇 |
2018年 | 16篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 21篇 |
2014年 | 26篇 |
2013年 | 43篇 |
2012年 | 20篇 |
2011年 | 31篇 |
2010年 | 23篇 |
2009年 | 29篇 |
2008年 | 34篇 |
2007年 | 38篇 |
2006年 | 27篇 |
2005年 | 42篇 |
2004年 | 34篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 17篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 10篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有727条查询结果,搜索用时 140 毫秒
21.
Koji Suzuki Akira Hinuma Hiroaki Saito Hiroshi Kiyosawa Hongbin Liu Toshiro Saino Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):167
To verify the hypothesis that the growth of phytoplankton in the Western Subarctic Gyre (WSG), which is located in the northwest subarctic Pacific, is suppressed by low iron (Fe) availability, an in situ Fe fertilization experiment was carried out in the summer of 2001. Changes over time in the abundance and community structure of phytoplankton were examined inside and outside an Fe patch using phytoplankton pigment markers analyzed by high-performance liquid chromatography (HPLC) and flow cytometry (FCM). In addition, the abundance of heterotrophic bacteria was also investigated by FCM. The chlorophyll a concentration was initially ca. 0.9 μg l−1 in the surface mixed layer where diatoms and chlorophyll b-containing green algae (prasinophytes and chlorophytes) were predominant in the chlorophyll biomass. After the iron enrichment, the chlorophyll a concentration increased up to 9.1 μg l−1 in the upper 10 m inside the Fe patch on Day 13. At the same time, the concentration of fucoxanthin (a diatom marker) increased 45-fold in the Fe patch, and diatoms accounted for a maximum 69% of the chlorophyll biomass. This result was consistent with a microscopic observation showing that the diatom Chaetoceros debilis had bloomed inside the Fe patch. However, chlorophyllide a concentrations also increased in the Fe patch with time, and reached a maximum of 2.2 μg l−1 at 5 m depth on Day 13, suggesting that a marked abundance of senescent algal cells existed at the end of the experiment. The concentration of peridinin (a dinoflagellate marker) also reached a maximum 24-fold, and dinoflagellates had contributed significantly (>15%) to the chlorophyll biomass inside the Fe patch by the end of the experiment. Concentrations of 19′-hexanoyloxyfucoxanthin (a prymnesiophyte marker), 19′-butanoyloxyfucoxanthin (a pelagophyte marker), and alloxanthin (a cryptophyte marker) were only incremented a few-fold increment inside the Fe patch. On the contrary, chlorophyll b concentration reduced to almost half of the initial level in the upper 10 m water column inside the Fe patch at the end of the experiment. A decrease with time in the abundance of eukaryotic ultraphytoplankton (<ca. 5 μm in size), in which chlorophyll b-containing green algae were possibly included was also observed by FCM. Overall, our results indicate that Fe supply can dramatically alter the abundance and community structure of phytoplankton in the WSG. On the other hand, cell density of heterotrophic bacteria inside the Fe patch was maximum at only ca. 1.5-fold higher than that outside the Fe patch. This indicates that heterotrophic bacteria abundance was little respondent to the Fe enrichment. 相似文献
22.
Atsushi Kaneda Hidetaka Takeoka Eiji Nagaura Yoshitsugu Koizumi 《Journal of Oceanography》2002,58(4):547-556
A cold-water intrusion, called a “bottom intrusion”, occurs in the lower layer of the Bungo Channel in Japan. It is an intrusion
from the shelf slope region of the Pacific Ocean margin in the south of the channel. In order to reveal the fundamental characteristics
of the bottom intrusion, we conducted long-term observations of water temperature at the surface and bottom layers of the
channel and 15-day current observations at the bottom of the shelf-break region. The long-term water temperature data indicated
that the bottom intrusion occurs repeatedly between early summer and late autumn, and its reiteration between early and mid-summer
causes a local minimum of water temperature in the lower layer in mid-summer. Moreover, the data revealed that most of the
bottom intrusions occurred in neap tidal periods. The current meter recorded a bottom intrusion with a speed of approximately
15 cm⋅s−1. The current meter also revealed that the intruded cold water slowly retreated back to the shelf slope region after the intrusion.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
23.
Takushi?NikiEmail author Taiki?Fujinaga Mariyo?F.?Watanabe Junji?Kinoshita 《Journal of Oceanography》2004,60(5):913-917
Solid-phase microextraction (SPME) is a simple, sensitive and less destructive method for the determination of dimethylsulfide
(DMS) in seawater. Combined with detection by gas chromatography-mass spectrometry (GC-MS), the method had sufficient sensitivity
(minimum detectable concentration of DMS was 0.05 nM), and practical levels of reproducibility (relative standard deviation
≤7%) and linearity (r
2 > 0.995) over a wide concentration range (0.5 to 910 nM). The protocol developed was applied to a Sagami Bay water sample
to determine concentrations of DMS and DMSP, and in situ DMSP-lyase activity. 相似文献
24.
Shinya Magome Tomohiro Yamashita Takeshi Kohama Atsushi Kaneda Yuichi Hayami Satoru Takahashi Hidetaka Takeoka 《Journal of Oceanography》2007,63(5):761-773
Jellyfish patch formation is investigated by conducting a drifter experiment combined with aerial photography of a sustained
patch of the moon jellyfish in Hokezu Bay, Japan. Jellyfish patches are aggregations of individuals that are caused by a combination
of swimming (active influence) and advection by currents (passive influence). The drifter experiment involved the injection
of 49 drifters around a distinct surface patch of jellyfish within an area of approximately 300 m × 300 m. The drifters’ motion,
caused only by the passive influence, was recorded in a series of 38 aerial photographs taken over approximately 1 h. The
ambient uniform current field larger than the patch scale was estimated from the movement of the centroid position of drifters,
while the distribution of horizontal divergence and relative vorticity around the patch was estimated from the time-derivative
in areas of triangles formed by the drifters. The centroid positions of both drifters and patches moved stably toward the
bay head at different speeds. The difference vector between the patch and drifter centroids was directed to the sun, and was
opposite to the ambient current. The distributions of vorticity and divergence around patches exhibited inhomogeneity within
the patch scale, and the drifters in this nonuniform current field aggregated near the convergence area within 1 h. The results
suggest that horizontal patch formation is predominantly influenced by passive factors at the surface of Hokezu Bay. Furthermore,
the upward swimming against downwelling may make sustained patch in surface layer. 相似文献
25.
Y.W. Watanabe H. Yoshinari A. Sakamoto Y. Nakano N. Kasamatsu T. Midorikawa T. Ono 《Marine Chemistry》2007,103(3-4):347-358
We proposed an empirical equation of sea surface dimethylsulfide (DMS, nM) using sea surface temperature (SST, K), sea surface nitrate (SSN, μM) and latitude (L, °N) to reconstruct the sea surface flux of DMS over the North Pacific between 25°N and 55°N: ln DMS = 0.06346 · SST − 0.1210 · SSN − 14.11 · cos(L) − 6.278 (R2 = 0.63, p < 0.0001). Applying our algorithm to climatological hydrographic data in the North Pacific, we reconstructed the climatological distributions of DMS and its flux between 25 °N and 55 °N. DMS generally increased eastward and northward, and DMS in the northeastern region became to 2–5 times as large as that in the southwestern region. DMS in the later half of the year was 2–4 times as large as that in the first half of the year. Moreover, applying our algorithm to hydrographic time series datasets in the western North Pacific from 1971 to 2000, we found that DMS in the last three decades has shown linear increasing trends of 0.03 ± 0.01 nM year− 1 in the subpolar region, and 0.01 ± 0.001 nM year− 1 in the subtropical region, indicating that the annual flux of DMS from sea to air has increased by 1.9–4.8 μmol m− 2 year− 1. The linear increase was consistent with the annual rate of increase of 1% of the climatological averaged flux in the western North Pacific in the last three decades. 相似文献
26.
Tsuneo Odate Toru Hirawake Atsushi Tanimura Mitsuo Fukuchi 《Journal of Oceanography》2000,56(2):185-196
Surface temperature, salinity, concentrations of silicate (Si) and nitrate + nitrite (N), and in vivo fluorescence (Fluor) were investigated in the marginal ice zone (MIZ) and the seasonally open oceanic zone (SOOZ) (32–40°E, 64–69°S) from February 23 to 28 1992. In the MIZ the mean Si and N were 67.8 ± 2.2 M and 32.5 ± 1.7 M, respectively. There was a trend that low N values coincided with high Fluor values. Observation conducted at one point (64°S, 38°E) revealed a diel variation pattern in Fluor. Applying this pattern of deviation from noon value, all Fluor data were normalized to value at local noon. In the MIZ a significant negative correlation was observed between the normalized Fluor and N but not Si. On the other hand, Si decreased continuously from south to north in the SOOZ and was negatively correlated with the normalized Fluor. Difference in Si concentration was about 30 M between the sea around 64°S and the MIZ, while the difference in N concentration was estimated as less than 10 M. If diatoms take up silicate and nitrogen at an approximate ratio of 1:1, additional nitrogenous nutrients other than nitrate and nitrite (e.g. ammonia, urea etc.) would be required. In this case, an f-ratio of lower than 33% is obtained. It is suggested that in the MIZ abundance of phytoplankton community dominated by non-diatom increases utilizing nitrate while in the SOOZ abundance of phytoplankton community dominated by diatoms increases consuming Si and regenerated nitrogen. 相似文献
27.
Abstract. Four sites were sampled in kelp (Macrocysiis pyrifera) forests occupying rocky bottom habitats along a wave exposure gradient in central California. Consistent betwecn-site differences were found in the three major structural elements - the surface canopy, the undcrstory assemblage, and the ground cover/turf assemblage - of kelp forest communities. Macrocysiis pyrifera was found at all four sites. Nereucyslis tuelkeana only at the most exposed site. The understory kelps Laminaria setchellii and Pterygopltora californica were also characteristic of exposed sites. Articulated coralline algae were more abundant at exposed sites than protected, while fleshy red algae showed the opposite pattern. All four study sites were located along 8.5 km of coastline, and thus were assumed to have available to them the same species pool for colonization. The substrate composition was the same and the amount of unconsolidated substrate was similar at all four sites. We suggest that exposure to wave-generated water motion, through its influence on the surface canopy and therefore on the amount of light reaching the bottom, is responsible for these between-site differences. 相似文献
28.
Kazushi Aranami Shuichi Watanabe Shizuo Tsunogai Masato Hayashi Ken Furuya Toshi Nagata 《Journal of Oceanography》2001,57(3):315-322
Dimethylsulfide (DMS), chlorophyll a (Chl-a), accessory pigments (fucoxanthin, peridinin and 19-hexanoyloxyfucoxanthin), and bacterial production (BP) were measured in the surface layer (0–100 m) of the subarctic North Pacific, including the Bering Sea, during summer (14 July–5 September, 1997). In surface sewater, the concentrations of DMS and Chl-a varied widely from 1.3 to 13.2 nM (5.1 ± 3.0 nM, mean ± S.D., n = 48) and from 0.1 to 2.4 µg L–1 (0.6 ± 0.6 µg L–1, n = 24), respectively. In the subarctic North Pacific, DMS to Chl-a ratios (DMS/Chl-a) were higher on the eastern side than the western side (p < 0.0001). Below the euphotic zone, DMS/Chl-a ratios were law and the correlation between DMS and Chl-a was relatively strong (r
2 = 0.700, n = 27, p < 0.0001). In the euphotic zone, DMS/Chl-a ratios were higher and the correlation between DMS and Chl-a was weak (r
2 = 0.128, n = 50, p = 0.01). The wide variation in DMS/Chl-a ratios would be at least partially explained by the geographic variation in the taxonomic composition of phytoplankton, because of the negative correlation between DMS/Chl-a and fucoxanthin-to-Chl-a ratios (Fuc/Chl-a) (r
2 = 0.476, n = 26, p = 0.0001). Furthermore, there was a positive correlation between DMS and BP (r
2 = 0.380, n = 19, p = 0.005). This suggests that BP did not represent DMS and dimethylsulfoniopropionate (DMSP) removal by bacterial consumption but rather DMSP degradation to DMS by bacterial enzyme. 相似文献
29.
The topographic effect of the Izu Ridge on the horizontal distribution of the North Pacific Intermediate Water (NPIW) south of Japan has been studied using observational data obtained by the Seisui-Maru of Mie University (Mie Univ. data) and those compiled by Japan Oceanographic Data Center (JODC data). Both data sets show that water of salinity less than 34.1 psu on potential density () surface of 26.8 is confined to the eastern side of the Izu Ridge, while water of salinity less than 34.2 psu is confined to the southern area over the Izu Ridge at a depth greater than 2000 m and to the southeastern area in the Shikoku Basin. It is also shown by T-S analysis of Mie Univ. data over the Izu Ridge that water of salinity less than 34.2 psu dominates south of 30°N, where the depth of the Izu Ridge is deeper than 2000 m and NPIW can intrude westward over the Izu Ridge. JODC data reveal that relatively large standard deviations of the salinity on surface of 26.7, 26.8 and 26.9 are detected along the mean current path of the Kuroshio and the Kuroshio Extension. Almost all of the standard deviations are less than 0.05 psu in other area with the NPIW, which shows that the time variation in the salinity can be neglected. This observational evidence shows that the topographic effect of the Izu Ridge on the horizontal distribution of the NPIW, which is formed east of 145°E by the mixing of the Kuroshio water and the Oyashio water, is prominent north of 30°N with a depth shallower than 2000 m. 相似文献
30.
Semigeostrophic gravity waves associated with a coastal boundary current, which has finite and uniform potential vorticity
and is bounded away from the coastline by a density front on the ocean surface, are investigated. It is shown that the semigeostrophic
coastal current has two waves which are named here the Semigeostrophic Coastal Wave (SCW) and the Semigeostrophic Frontal
Wave (SFW). The SCW becomes an elementary Kelvin wave at some limit while the SFW is caused by the existence of the surface
density front. The SCW appears mainly as variations in the upper layer depth at the coast and as alongshore velocity at the
density front. On the other hand, the SFW appears mainly as variations in the width of the current. When the weak nonlinearity
and ageostrophic effect are included, these semigeostrophic gravity waves satisfy the Kortweg- de Vries equation, which suggests
that the local changes in the width and/or velocity of the semigeostrophic coastal current propagate as wave-like disturbances. 相似文献