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71.
72.
香港地区海陆风的显式模拟研究 总被引:2,自引:2,他引:2
利用MM5模式对香港地区的海陆风进行了显式数值研究,模拟的风向、风速和温度与站点的观测值比较一致,较详细地分析了海陆风的日变化规律和三维结构特征,结果显示香港地区海风分布复杂,主要受偏西、偏南和偏东海风气流的影响,形成多个辐合带,海风锋最远可以深入内陆约90 km;陆风较简单,主要是偏北气流,陆风的风速和强度都比海风要弱,与山谷风、城市热岛环流等形成弱的辐合。香港是一个海岸曲折、多丘陵的地区,其中75%的面积是山区,为了研究这些丘陵地形对香港地区海陆风的影响,设计了保留海陆分布,去掉丘陵地形的敏感性试验,结果表明,由于丘陵地形的存在,在白天地形的热力作用是主要的,增强了海风的强度;而晚上动力阻挡作用比较明显,减弱了陆风的强度。 相似文献
73.
A numerical study of the influence of urban expansion on monthly climate in dry autumn over the Pearl River Delta, China 总被引:6,自引:0,他引:6
W. S. Lin C.-H. Sui L. M. Yang X. M. Wang R. R. Deng S. J. Fan C. S. Wu A. Y. Wang S. K. Fong H. Lin 《Theoretical and Applied Climatology》2007,89(1-2):63-72
Summary In this study, we employed a regional model to simulate the impact of urban expansion on monthly climate in Pearl River Delta
(PRD) region. Two experiments were performed by prescribing two different land covers in the PRD region. One land cover represents
vegetation in the 1970s which is derived from the United States Geological Survey (USGS) data with 24-category (hereafter
referred to as NU). The other land cover represents the current urban condition which is derived from remote sensing data
acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) in 2004 (hereafter referred to as HU). Using the two
land cover datasets, monthly climate of October 2004 was simulated, which was a very dry season in the PRD region. The results
obtained from the numerical simulation show a distinct difference in simulated shelter-level temperature, humidity, surface
fluxes and the height of planetary boundary layer (PBL) with two different land cover data sets being specified. The maximum
difference in simulated monthly mean temperature over urban areas was 0.9 °C. A large temperature difference was found in
urbanized area in Guangzhou, Dongguan, Zhongshan and Shenzhen. The monthly mean relative humidity in urban areas decreased
by 1.4% as a result of urban expansion (from 59.2% in NU to 57.8% in HU). The maximum decrease in mixing ratio was 0.4 g/kg
in Guangzhou and Dongguan, whereas the maximum decrease in relative humidity was 2.4%. There was an increase of sensible heat
flux in developed lands and the maximum increase was 90 W m−2. In contrast, latent hear flux in urban area decreased and the maximum decrease was 300 W m−2. In addition, the increase in mean height of PBL ranged from 20 to 80 m (HU compared with NU), and the maximum change of
the height was 180 m over urban area in city of Guangzhou. 相似文献
74.
Resource subsidy regimes, which range from presses to pulses, are common structuring forces in communities, yet research contrasting their effects is lacking. Many coastal marine ecosystems, including estuaries and coral reefs, have experienced increased nutrient subsidies while concurrently shifting to macroalgal dominance; however, the role of subsidy regime in transitions remains unknown. We created concentration–frequency distributions of nutrients in Cook’s Bay, Moorea, French Polynesia, and Carpinteria Salt Marsh Reserve, CA, USA. Both showed relatively high pulses interspersed by press concentrations. We grew dominant macroalgae alone and together in microcosms approximating these subsidy regimes to quantify individual performance and competitive outcomes. Subsidy regime changed growth and competitive abilities of macroalgae from both ecosystems but with divergent effects. In nutrient-limited reefs, different species were favoured under each enrichment regime, suggesting a fluctuating nutrient environment enhances diversity. In contrast, in eutrophic estuaries, enrichment of both regimes facilitated a single competitive dominant, suppressing diversity. Functional form groups did not predict responses to subsidy regime, likely because classifications ignore temporal variability in resource supplies. Because climate change will alter rainfall patterns globally, further accelerating nutrient subsidies from land to sea, understanding species’ responses to nutrient subsidy regimes is key to predicting the fate of coastal communities. 相似文献
75.
Numerical prediction experiment on Typhoon Maggie (9903) 总被引:3,自引:1,他引:3
Fong Soi Kun Wu Chisheng Hao I Pan Lam Kin Hang Ku Chi Meng Wang Anyu Lin Wenshi 《海洋学报(英文版)》2001,20(2):171-181
I~IOXTyphoon is a severe and diSaStrous weather phenomenon that affeCts the southeaSt COaStsregion of China. It causes Serious lOSS for the social eCOnondc development as well as the life andproperties Of PeOPle. Therefore, the enhancement to study on the artifice of monitoring, Prediction and public services of typhoon is an i~nent requirement for gove~t and Public.The concern is also a taSk of great Urgency to advanCe meteorolQgical sciences.Starting from the 1980' s, as the deve… 相似文献
76.
Cheinway Hwang Tzu-Pang Tseng Ting-Jung Lin Dražen Švehla Urs Hugentobler Benjamin Fong Chao 《GPS Solutions》2010,14(1):121-131
The precise orbit determination antennas of F3/C and GRACE-A satellites are from the same manufacturer, but are installed
in different configurations. The current orbit accuracy of F3/C is 3 cm at arcs with good GPS data, compared to 1 cm of GRACE,
which has a larger ratio of usable GPS data. This paper compares the qualities of GPS observables from F3/C and GRACE. Using
selected satellites and time spans, the following average values for the satellite F3/C and satellite A of GRACE are obtained:
multipath effect on the pseudorange P1, 0.78 and 0.38 m; multipath effect on the pseudorange P2, 1.03 and 0.69 m; occurrence
frequency of cycle slip, 1/29 and 1/84; standard error of unit weight, 4 and 1 cm; dynamic–kinematic orbit difference, 10
and 2 cm. For gravity determination using F3/C GPS data, a careful selection of GPS data is critical. With six satellites
in orbit, F3/C’s large amount of GPS data will make up the deficiency in data quality. 相似文献
77.
南海夏季风爆发的数值预报模拟实验 总被引:5,自引:0,他引:5
1998年5月21日00时(UTC),对流层上部200hPa的南亚反气旋中心位于(16oN,94oE)附近,850hPa南海的中南部仍为副热带反气旋控制;到21日12时,200hPa的南亚反气旋中心迅速移到(21oN,94oE)附近,同时850hPa的南海副热带反气旋减弱东撤,南海的中南部由东南风转变为西南风,南海夏季风爆发。本文利用美国国家大气研究中心和宾西法尼亚州大学联合研制的中尺度模式(MM5V2)模拟预报这一过程,同时通过敏感性实验研究了区域边界条件和水平分辨率对季风预报模拟实验的影响。 相似文献
78.
The Penn State/ NCAR Mesoscale Model (MM5) is used to simulate the precipitation event that occurred during 1–2 May 1994 to
the south of the Yangtze River. In five experiments the Kain–Fritsch scheme is made use of for the subgrid–scale convective
precipitation, but five different resolvable–scale microphysical parameterization schemes are employed. They are the simple
super-saturation removal scheme, the warm rain scheme of Hsie et al. (1984), the simple ice scheme of Dudhia (1989), the complex
mixed–phase scheme developed by Reisner et al. (1993), and the GSFC microphysical scheme with graupel. Our interest is how
the various resolvable-scale schemes affect the domain-averaged precipitation, the precipitation distribution, the sea level
pressure, the cloud water and the cloud ice. Through a series of experiments about a warm sector rainfall case, results show
that although the different resolvable-scale scheme is used, the differences of the precipitation characteristics among all
five runs are not very obvious. However, the precipitation is over-predicted and the strong mesoscale low is produced by the
simple super-saturation removal scheme. The warm rain scheme with the inclusion of condensation and evaporation under-predicts
the precipitation and allows the cloud water to reach the 300 hPa level. The scheme of the addition of graupel increases the
resolvable-scale precipitation by about 20%-30%. The inclusion of supercooled liquid water in the grid-scale scheme does not
affect significantly the results. 相似文献
79.
80.
Localized declines in coral condition are commonly linked to land-based sources of stressors that influence gradients of water quality, and the distance to sources of stressors is commonly used as a proxy for predicting the vulnerability and future status of reef resources. In this study, we evaluated explicitly whether proximity to shore and connections to coastal bays, two measures of potential land-based sources of disturbance, influence coral community and population structure, and the abundance, distribution, and condition of corals within patch reefs of the Florida Reef Tract. In the Florida Keys, long-term monitoring has documented significant differences in water quality along a cross-shelf gradient. Inshore habitats exhibit higher levels of nutrients (DIN and TP), TOC, turbidity, and light attenuation, and these levels decrease with increasing distance from shore and connections to tidal bays. In clear contrast to these patterns of water quality, corals on inshore patch reefs exhibited significantly higher coral cover, higher growth rates, and lower partial mortality rates than those documented in similar offshore habitats. Coral recruitment rates did not differ between inshore and offshore habitats. Corals on patch reefs closest to shore had well-spread population structures numerically dominated by intermediate to large colonies, while offshore populations showed narrower size-distributions that become increasingly positively skewed. Differences in size-structure of coral populations were attributed to faster growth and lower rates of partial mortality at inshore habitats. While the underlying causes for the favorable condition of inshore coral communities are not yet known, we hypothesize that the ability of corals to shift their trophic mode under adverse environmental conditions may be partly responsible for the observed patterns, as shown in other reef systems. This study, based on data collected from a uniform reef habitat type and coral species with diverse life-history and stress-response patterns from a heavily exploited reef system, showed that proximity to potential sources of stressors may not always prove an adequate proxy for assigning potential risks to reef health, and that hypothesized patterns of coral cover, population size-structure, growth, and mortality are not always directly related to water quality gradients. 相似文献