全文获取类型
收费全文 | 199篇 |
免费 | 5篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 2篇 |
地球物理 | 68篇 |
地质学 | 62篇 |
海洋学 | 47篇 |
天文学 | 5篇 |
自然地理 | 21篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 9篇 |
2011年 | 8篇 |
2010年 | 10篇 |
2009年 | 8篇 |
2008年 | 11篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 9篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有208条查询结果,搜索用时 31 毫秒
171.
This paper deals with steel moment frames combined with hysteretic dampers. Specifically, it examines the strength of dampers required to minimize damage to moment frames under earthquake loading. The important structural variables are the ratio of the dampers' shear strength to the maximum resistance, termed β in this study, and the relative stiffness between the damper and the main frame, termed k. The equivalent viscous damping ratio of the entire structural system is affected by the quantities β and k and the ductility ratio of the main frame. The optimum dampers' strength ratio (βopt), which maximizes the equivalent viscous damping ratio, was formulated as a function of k, and it was found that βopt is independent of the ductility ratio of the main frame. Earthquake response analysis confirmed that damage to the main frame can be significantly reduced by hysteretic dampers and minimized at the value of βopt. © 1998 John Wiley & Sons, Ltd. 相似文献
172.
Goh Onitsuka Yutaka Yoshikawa Tomoyuki Shikata Kei Yufu Kazuo Abe Takahisa Tokunaga Katsunori Kimoto Takeshi Matsuno 《Journal of Oceanography》2018,74(4):351-365
The temporal evolution of a thin phytoplankton layer was observed by field measurements using a research vessel and mooring instruments in the Yatsushiro Sea, a semi-enclosed narrow embayment in Japan, in early August 2013. The subsurface chlorophyll maximum developed into a thin layer within 2 days just below the pycnocline at around 10-m depth, where turbulent mixing (the dissipation rate of turbulent kinetic energy) was weak (low). The layer persisted for 1.5 to 2 days and declined after irradiance drastically decreased at the sea surface. At the peak period, the layer thickness, which is defined as the full-width at half-maximum of the peak in chlorophyll a concentration, ranged from 0.6 to 1.4 m, and the maximum concentration reached 42.3 mg m?3. The horizontal extent of the layer was approximately 10 km along the longitudinal axis of the bay. The phytoplankton population characterized by the layer was dominated by a chain-forming centric diatom, Chaetoceros spp. The formation mechanisms of the thin diatom layer were investigated using the observed data and a vertical one-dimensional model that includes physical and biological processes. The results suggest that the development of the thin layer was caused by in situ growth and aggregation due to nutrient-dependent sinking of the species under weak turbulence. The study highlights that continuous multidisciplinary observations and understanding species-specific physiological responses to environmental variations are necessary to elucidate drastically fluctuating phytoplankton dynamics in a coastal water. 相似文献
173.
174.
Abstract A systematic geochemical study of sandstones from the Cretaceous Shimanto Supergroup and psammitic schists from the Oboke unit in Shikoku has been carried out in order to clarify the depositional age of the protoliths of the Oboke psammitic schists. The geochemical data, together with chronological and geologic data, led to the following conclusions. (i) It is inferred that Oboke psammitic schists are metamorphically equivalent to sandstones in the Hiwasa Formation of the Shimanto accretionary complex, deposited in a trench area during the Campanian, in eastern Shikoku. (ii) The protolith attained to maximum metamorphic conditions within 20 million years after the deposition. (iii) The accumulation of a large amount of coarse-grained clastic sediments in the trench area induced offscraping and underplating of the sediments in the subduction zone, forming the Hiwasa Formation and Oboke unit, respectively. 相似文献
175.
Microalgal-based indicators were used to assess terrestrial influence on Shiraho coral reef of Ishigaki Island (Okinawa, Japan). A typhoon occurred on 4-5 August 2005 and sampling were made on three occasions thereafter (6, 8, and 11 August). Pre-typhoon sampling was conducted on 26 July. The typhoon-enhanced terrestrial discharges increased reef nutrient levels (e.g. average NO(3)(-)-N: 0.088mg/L pre-typhoon to 0.817mg/L post-typhoon). This elevated chlorophyll-a concentrations by four times and shifted phytoplankton composition (spectral class-based) from an initial dominance of diatoms and green microalgae to the dominance of bluegreen microalgae (cyanobacteria) and cryptophytes. Cyanobacteria later increased by more than 200% and accounted for as much as 80% of total chl-a ( approximately 0.29microg/L), possibly assisted by favorable nutrient availability. In outer reef waters, diatoms and green microalgae predominated whereas cyanobacteria and cryptophytes were nearly undetectable. Due to detrital decomposition and river discharge, the CDOM was much higher in the inner reef than in the outer reef. Benthic bluegreen microalgae were relatively more abundant in areas close to the river mouth and coastal agricultural fields. At these locations, nutrient concentrations were much higher due to river discharge and potentially significant groundwater discharge. Thus, phytoplankton and benthic microalgae can serve as indicators of terrestrial influence on coral reefs. 相似文献
176.
Toru Kobari Hiroyasu Akamatsu Masato Minowa Toshihiro Ichikawa Kazuo Iseki Ryuji Fukuda Masataka Higashi 《Journal of Oceanography》2010,66(5):673-684
Seasonal changes in the shape and size composition of fecal pellets were investigated with sediment trap samples from 50 and
150 m in Kagoshima Bay to evaluate how the mesozooplankton community affects fecal pellet flux. Deep vertical mixing was evident
in March, and thermal stratification was developed above 50 m in June, August and November. Chlorophyll a, suspended particulate organic carbon (POC) and copepod abundance were uniform throughout the water column during the seasonal
mixing and concentrated above 50 m in the stratified seasons. Calanoids were the most predominant copepods in March and poecilostomatoids
composed more than 45% of the copepod community in June, August and November. Fecal pellet fluxes at 50 and 150 m were the
highest in March, nearly half of POC flux. The relative contribution declined considerably in the other months, especially
for less than 4% of POC flux in August. The decline was corresponded to the predominance of cyclopoids and poecilostomatoids.
Cylindrical pellets dominated the fecal matters at both depths throughout the study period, while larger cylindrical pellets
nearly disappeared at 150 m in June, August and November. Copepod incubation revealed that cylindrical and oval pellets were
egested by calanoids and the other copepods, respectively. We suggest that cylindrical fecal pellets produced by calanoid
copepods contribute to feces flux but the predominance of poecilostomatoids and/or cyclopoids decreases feces flux via the
increase of oval pellets and fragmentation of larger cylindrical pellets. 相似文献
177.
Lawrence Patrick C. Bernardo Kazuo Nadaoka Takashi Nakamura Atsushi Watanabe 《Ocean Dynamics》2017,67(11):1369-1384
While widely known for their destructive power, typhoon events can also bring benefit to coral reef ecosystems through typhoon-induced cooling which can mitigate against thermally stressful conditions causing coral bleaching. Sensor deployments in Sekisei Lagoon, Japan’s largest coral reef area, during the summer months of 2013, 2014, and 2015 were able to capture local hydrodynamic features of numerous typhoon passages. In particular, typhoons 2015-13 and 2015-15 featured steep drops in near-bottom temperature of 5 °C or more in the north and south sides of Sekisei Lagoon, respectively, indicating local cooling patterns which appeared to depend on the track and intensity of the passing typhoon. This was further investigated using Regional Ocean Modeling System (ROMS) numerical simulations conducted for the summer of 2015. The modeling results showed a cooling trend to the north of the Yaeyama Islands during the passage of typhoon 2015-13, and a cooling trend that moved clockwise from north to south of the islands during the passage of typhoon 2015-15. These local cooling events may have been initiated by the Yaeyama Islands acting as an obstacle to a strong typhoon-generated flow which was modulated and led to prominent cooling of waters on the leeward sides. These lower temperature waters from offshore may then be transported to the shallower inner parts of the lagoon area, which may partly be due to density-driven currents generated by the offshore-inner area temperature difference. 相似文献
178.
Karim Nassar Wael Elham Mahmod Hassan Fath Ali Masria Kazuo Nadaoka Abdelazim Negm 《Marine Georesources & Geotechnology》2019,37(1):81-95
This study focuses on the shoreline change detection along the North Sinai coast in Egypt using geographic information system and digital shoreline analysis system (DSAS) during the elapsed period from 1989 to 2016. The measurement of shoreline variation is mainly described for three zones: zone I, El-Tinah plain bay; zone II, El-Bardawil Lake; zone III, El-Arish valley. The rates of shoreline changes in the form of erosion and accretion patterns are automatically quantified by four statistical parameters functioned in DSAS namely endpoint rate, net shoreline movement, linear regression rate (LRR), and least median of squares. LRR results elucidate that the western seaside of El-Tinah plain bay has experienced an extremely dynamic feature with an average erosion rate of ?8.17?m/year. The littoral drifts have been driven by eastward alongshore currents toward the east side of the bay to be accreted with an average rate of +4.28?m/year. Moreover, the shoreline has progressed west of El-Bardawil inlet (1), El-Bardawil inlet (2), and El-Arish harbor. Subsequently, the corresponding average beach growth rates are found to be +2.7, +8.5, and +6.5?m/year, respectively. In contrast, the shoreline on the down-drift side to the east has negatively retreated, and the corresponding beaches have regressed at rates of ?4.5, ?8.65, and ?2.9?m/year, respectively. 相似文献
179.
180.
Jinming Feng Dong-Kyou Lee Congbin Fu Jianping Tang Yasuo Sato Hisashi Kato John L. Mcgregor Kazuo Mabuchi 《Meteorology and Atmospheric Physics》2011,111(1-2):41-53
A number of uncertainties exist in climate simulation because the results of climate models are influenced by factors such as their dynamic framework, physical processes, initial and driving fields, and horizontal and vertical resolution. The uncertainties of the model results may be reduced, and the credibility can be improved by employing multi-model ensembles. In this paper, multi-model ensemble results using 10-year simulations of five regional climate models (RCMs) from December 1988 to November 1998 over Asia are presented and compared. The simulation results are derived from phase II of the Regional Climate Model Inter-comparison Project (RMIP) for Asia. Using the methods of the arithmetic mean, the weighted mean, multivariate linear regression, and singular value decomposition, the ensembles for temperature, precipitation, and sea level pressure are carried out. The results show that the multi-RCM ensembles outperform the single RCMs in many aspects. Among the four ensemble methods used, the multivariate linear regression, based on the minimization of the root mean square errors, significantly improved the ensemble results. With regard to the spatial distribution of the mean climate, the ensemble result for temperature was better than that for precipitation. With an increasing number of models used in the ensembles, the ensemble results were more accurate. Therefore, a multi-model ensemble is an efficient approach to improve the results of regional climate simulations. 相似文献