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121.
We examined long-term charcoal records spanning the glacial–interglacial cycles that are evident in two cores collected from Lake Biwa in central Japan. We found that the records of the two cores have a similar long-term variation pattern of charcoal concentrations and abundant large charcoal fragments in postglacial sediments, which indicates that frequent fires occurred near the shores of Lake Biwa during the postglacial period. Analogous natural conditions in the early postglacial period and the early part of the last interglacial period strongly suggest that the frequent fires that occurred only during the postglacial period were anthropogenic. A comparison between the charcoal records of Lake Biwa sediments and the cultural changes and human populations in this district suggests that anthropogenic fires in this district were influenced by the lifestyle and culture of each era rather than by the populations. Humans tended to use more fire at the start of the settlement during the early Neolithic era in this region, in spite of the small population size. 相似文献
122.
Seaports are located in vulnerable areas to climate change impacts: on coasts susceptible to sea-level rise and storms or at mouths of rivers susceptible to flooding. They serve a vital function within the local, regional, and global economy. Their locations in the heart of sensitive estuarine environments make it an imperative to minimize the impacts of natural hazards. Climate impacts, like a projected SLR of .6?m to 2?m and doubling of Category 4 and 5 hurricanes by 2100, will result in more extreme events at many seaports. To assess the current state of knowledge on this issue, we surveyed port authorities from around the world about how administrators felt climate change might impact their operations, what sea-level change would create operational problems, and how they planned to adapt to new environmental conditions. The planned rapid expansion of ports reported by the survey respondents indicates that adaptation measures should be considered as ports construct new infrastructure that may still be in use at the end of the century. Respondents agreed that the ports community needs to address this issue and most felt relatively uninformed about potential climate impacts. Although most ports felt that SLR would not be an issue at their port this century, sea-level rise was nevertheless an issue of great concern. Our results suggest opportunities for the scientific community to engage with port practitioners to prepare proactively for climate change impacts on this sector. 相似文献
123.
S. Yonemura S. Kawashima H. Matsueda Y. Sawa S. Inoue H. Tanimoto 《Theoretical and Applied Climatology》2008,92(1-2):47-58
Summary The application of principal components and cluster analysis to vertical ozone concentration profiles in Tsukuba, Japan, has
been explored. Average monthly profiles and profiles of the ratio between standard deviation and the absolute ozone concentration
(SDPR) of 1 km data were calculated from the original ozone concentration data. Mean (first) and gradient (second) components
explained more than 80% of the variation in both the 0–6 km tropospheric and 11–20 km troposphere–stratosphere (interspheric)
layers. The principal components analysis not only reproduced the expected inverse relationship between mean ozone concentration
and tropopause height (r
2 = 0.41) and that in the tropospheric layer this is larger in spring and summer, but also yielded new information as follows.
The larger gradient component score in summer for the interspheric layer points to the seasonal variation of the troposphere–stratosphere
exchange. The minimum SDPR was at about 3 km in the tropospheric layer and the maximum was at about 17 km in the interspheric
layer. The tropospheric SDPR mean component score was larger in summer, possibly reflecting the mixing of Pacific maritime
air masses with urban air masses. The cluster analysis of the monthly ozone profiles for the 1970s and 2000s revealed different
patterns for winter and summer. The month of May was part of the winter pattern in the 1970s but part of the summer pattern
during the 2000s. This statistically detected change likely reflects the influence of global warming. Thus, these two statistical
analysis techniques can be powerful tools for identifying features of ozone concentration profiles.
Authors’ addresses: S. Yonemura, S. Kawashima, S. Inoue, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai,
Tsukuba, Ibaraki 305-0031, Japan; H. Matsueda, Y. Sawa, Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki
305-0052, Japan; H. Tanimoto, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan. 相似文献
124.
Anomalous sea level, anomalous observed dynamic height (0/400 db) and anomalous model dynamic height are examined at the locations
of 13 island sea level stations in the tropical Pacific for each bimonth of the four year period 1979 to 1982. Starting in
1981, the anomalous dynamic height data show off-equatorial Rossby waves propagated toward the W boundary of the Pacific basin.
At the W boundary, the model Rossby wave activity was found to have excited coastally trapped Kelvin-Munk waves which transmitted
the anomalous dynamic height equatorward. At the equator, coastally trapped wave activity excited eastward propagating equatorial
Kelvin waves, yielding a pair of anomalous peaks in dynamic height variability in the E equatorial Pacific associated with
the 1982–1983 ENSO event. The evolution of the peaks in dynamic height associated with the Rossby and Kelvin wave activity
reflects the redistribution of observed upper-ocean heat content in the W tropical Pacific, providing a qualitative hindcast
for the 1982–1983 ENSO event.
In consequence of these results, and the results of a related study (Inoue et al. 1985), the redistribution of both observed
and model heat content, as evidenced in dynamic height in the W Pacific during the 23-year period 1964–1985, is examined for
its ability to hindcast and forecast ENSO events in this period. Complex EOF analysis is applied to the Onset Phase of ENSO
events occurring in 1968–69, 1972–73, 1976–77, and 1982–83; it is used to determine the characteristic redistribution of heat
content (dynamic height) prior to the Mature Phase of ENSO events. This analysis found both model and observed dynamic height
in the N hemisphere to be characterized by wind-driven, westward propagating, baroclinic Rossby wave activity, having a remarkably
stable period of 3 years over the 23-year period. The complex time series associated with these first spatial eigen-functions
are used to construct observed and model hindcast indices that yield high values one year prior to the Mature Phase of ENSO
events of the period. These indices achieve these values due to the incidence upon the Philippine coast in fall/winter of
a positive anomaly in dynamic height propagating from the east at nondispersive Rossby long wave speeds. 相似文献
125.
Tomoko Kyuka Satomi Yamaguchi Yusuke Inoue Kattia Rubi Arnez Ferrel Hideto Kon Yasuyuki Shimizu 《地球表面变化过程与地形》2021,46(7):1225-1237
Previous studies have demonstrated that riparian vegetation leads to channel transformation from a multi-bar to a single-thread channel planform. However, it still remains unclear how the presence of pioneer and mature vegetation affects the morphodynamics of single-thread meandering rivers. In this study, we therefore investigated the effects of vegetation strength on the morphodynamic evolution of an experimental meandering channel. Three physical laboratory experiments were conducted using alfalfa sprouts in different life stages – no vegetation, immature vegetation, and mature vegetation – to simulate different floodplain vegetation strengths. Our results demonstrate that vegetation plays a key role in mediating bank erosion and point-bar accretion, and that this is reflected in both the evolution of the channel bed as well as the sediment flux. The presence of mature vegetation maintained a deep, single-thread channel by reducing bank erosion, thereby limiting both channel widening and sediment storage capacity. Conversely, an unvegetated floodplain led to channel widening and high sediment storage capacity. Channel evolution in the unvegetated scenario showed that the active sediment supply from outer bank erosion led to slightly delayed point-bar accretion on the inner banks due to helical flow, deflecting the surface flow toward the outer banks and causing further erosion. In contrast, in the immature vegetation scenario, the outer banks were also initially eroded, but point-bar accretion did not clearly progress. This led to a greater width-to-depth ratio, resulting in a transition from a single- to a multi-thread channel with minor flow paths on the floodplain. The experimental results suggest that the eco-morphodynamic effects of young (low-strength) and mature (high-strength) vegetation are different. Notably, low-strength, early-stage vegetation increases channel complexity by accelerating both channel widening and branching, and therefore might promote the coexistence of multi-bars and pioneer vegetation. 相似文献
126.
127.
128.
Mutsuo Inoue Yusuke Nakano Yoko Kiyomoto Hisaki Kofuji Yasunori Hamajima Masayoshi Yamamoto 《Journal of Oceanography》2010,66(3):425-428
A total of 21 surface water samples were collected on the east side of the East China Sea (ECS) (3 sites) and at the Tsushima
Strait (1 site), and 226Ra and 228Ra activities were measured using low-background γ-spectrometry. The 228Ra/226Ra ratios among the samples exhibited notable seasonal variation (228Ra/226Ra = 0.2–2.6) accompanying changes of salinity (31.7–34.7). Seasonal water circulation within the ECS is hypothesized to cause
the change by altering the mixing ratio of 228Ra-rich continental shelf water and 228Ra-poor Kuroshio water. 相似文献
129.
A new type of rock drill, which has compact size and a simple mechanism and which can be automatically operated in water, was developed. The drill can obtain 75 cm of rock core from a rocky bottom covered by thin sediments at a maximum depth of 300 m.The drill was operated under a current of 1.5 knots in Sagami Bay south of Tokyo and obtained a 40-cm core of volcanic conglomerate of Miocene age from the slope of a small bank at a depth of 130 m. During the operation the vessel was not anchored. 相似文献
130.
In order to investigate ways of reducing vibrations of building structures subjected to excitation acting on intermediate storey, active vibration controls are conducted with active control devices installed on different floors of the structure, and the effective location of control devices is also investigated. In this paper, we propose a new ‘Discrete‐Optimizing Control Method’ for vibration control. The control forces are determined analytically which makes the ‘discrete‐index function’ minimum. Through numerical simulation, the Discrete‐Optimizing Control Method is proved to be an effective control method. The response reduction effects are best when the control devices are concentrated on the adjacent three floors of the vibration source. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献