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81.
地质灾害的形成原因有自然的也有人为的,矿山泥石流就是由人为因素为主导,在矿山一带沟谷内形成的。由于物源堆存量和地域短时降水量大小的不同,使灾害发生的规模和对附近居民带来的影响也各不相同。该文以保定西部矿山泥石流特征为例,弄清地质灾害的发生机制和发展规律,对防灾减灾、环境保护及灾害治理工作有着极其重要而深远的意义。 相似文献
82.
地质灾害的形成原因有自然的也有人为的,矿山泥石流就是由人为因素为主导,在矿山一带沟谷内形成的。由于物源堆存量和地域短时降水量大小的不同,使灾害发生的规模和对附近居民带来的影响也各不相同。该文以保定西部矿山泥石流特征为例,弄清地质灾害的发生机制和发展规律,对防灾减灾、环境保护及灾害治理工作有着极其重要而深远的意义。 相似文献
83.
84.
ABSTRACTDue to their efficiency, revitalized traditional techniques for irrigation management of scarce water resources have been suggested as a way to at least partially cope with the present water crises in the Middle East. A better irrigation management includes re-using treated wastewater in agriculture. Treated wastewater should also be used in industrial processes, thus contributing to a more efficient overall water management. However, the most important change leading to better water management is improving water efficiency in agricultural irrigation. Traditional water management techniques have an important role in many Middle East and North African (MENA) countries. Besides bringing more water to a thirsty population, they can also contribute to the societal awareness, and recognition of the great diversity of cultural and social values water has to human civilization.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR P. Hubert 相似文献
85.
再论北京西山山地壶穴的形态特征与成因机制 总被引:1,自引:0,他引:1
北京西山"京西古道"的"驮兽蹄窝",近些年来因为进山旅游的人越来越多而名声大噪,常见诸报刊、电视、网络等媒体。至于其真正成因,却鲜有学者深究。通过对出现"驮兽蹄窝"的北京西山牛角岭、石佛岭和峰口庵三个垭口详细的野外观察和实地测量,认为基岩路面上那些圆形、椭圆形或多边形凹坑,是历史上无数次暴雨流挟带砂砾冲刷与磨蚀基岩坡面上原先的构造和岩性薄弱部位而逐渐形成的山地壶穴(hillside potholes),属于正常的雨流侵蚀现象(rain-induced erosion)。壶穴的分布特征(在山脊垭口两侧,沿基岩路面上沟槽成串分布)、几何形态的非对称性、内壁的水平擦痕、底部的中央岛现象,以及长、短轴长度、长短轴比(a/b)、宽深比(D/h)和长轴倾向的统计结果与D-h相关性等数据,皆证明"驮兽蹄窝"的成因是不可能的。 相似文献
86.
The precipitation events (n = 91), collected for 3 years (2000–2002) during the period of SW-monsoon (Jun–Aug) from an urban
site (Ahmedabad, 23.0°N, 72.6°E) of a semi-arid region in western India, are found to exhibit characteristic differences in
terms of their solute contents. The low solute (<700 μeq L−1) events are either marked by heavy precipitation amount or successive events collected during an extended rain spell; whereas
light precipitation events occurring after antecedent dry period are characterized by high solutes (>700 μeq L−1). The ionic composition of low solute events show large variability due to varying contribution of anthropogenic species
(: 1%–74%; : 1%–25%; and : 8%–68%) to the respective ion balance. In high solute events, ionic abundances are dominated by mineral dust (Ca2+ and ) and sea-salts (Na+ and Cl−). These differences are also reflected in the pH of low solute events (range: 5.2–7.4, VWM: 6.4) and high solute events (range:
6.6–8.2, VWM: 7.3). The comparison of Ca2+/Na+ and nss- ratios (on equivalent basis) in rain and aerosols suggests that the ionic composition of high solute events is influenced
by below-cloud scavenging; whereas evidence for in-cloud scavenging is significantly reflected in low solute events. The annual
wet-deposition fluxes of and are 330 and 480 mg m−2 y−1, respectively, in contrast to their corresponding dry-deposition fluxes (14 and 160 mg m−2 y−1); whereas wet and dry removal of Ca2+, Mg2+ and are comparable. 相似文献
87.
Major ion content of 37 wet-only rainwater samples collected on the southern flank of Mount Etna volcano was investigated. Measured pH values range from 3.80 to 7.22 and display a positive correlation with Ca2+ and an inverse correlation with NO3
–, suggesting that anthropogenic NOx are the most effective acidifying agents while Ca, likely as solid CaCO3, is the prevailing proton acceptor. Na/Cl ratios indicate a dominant marine origin for both species, while K, mg and Ca contents point to additional sources (soil dust, fertilisers etc.). Nitrate and sulphate concentrations display a nearly constant ratio indicating a common anthropogenic origin, and only a few samples are characterised by sulphate excess. The analysis of time series reveals a good correlation between the excess sulphate in rainwater and SO2 fluxes from the summit craters plume. Non sea salt chloride contents show also a significant correlation with volcanic activity indicating a magmatic sulphur and chloride contribution to rainwater. Meteoric flux estimations point to a prevailing magmatic origin for sulphur in the collected rainwaters while sea spray is the main source of chlorine. 相似文献
88.
Methanesulfonate (MS–) and non-sea-salt sulfate (nss-SO
4
2–
), two of the major oxidation products of atmospheric dimethylsulfide (DMS), have been continuously measured in rainwater at three remote islands in the Southern Indian Ocean: Amsterdam since 1991, Crozet since 1992, and Kerguelen since 1993. The annual volume weighted mean (VWM) concentrations of nss-SO
4
2–
in rainwater were 3.19, 3.04 and 4.57 eq l–1 at Amsterdam, Crozet, and Kerguelen, respectively while the VWM of MS– were 0.24, 0.15 and 0.30 eq l–1, respectively. At all three islands, MS– presented a well-distinguished seasonal variation with a maximum during summer whereas the seasonal variation of nss-SO
4
2–
was less pronounced, possibly due to the increased anthropogenic influence during the winter period. Furthermore, MS– presented significant interannual variations, in particular at Amsterdam and Crozet, which is closely related to the sea-surface temperature (SST) anomalies). Finally, the nss-SO
4
2–
deposition at Crozet Island presented a decreasing interannual trend, reflecting probably reductions in sulfur emissions from Southern Africa. On the contrary no interannual tendency was observed in the nss-SO
4
2–
concentrations at Amsterdam Island, indicating that the biogeochemical sulfur cycle at this area is mainly influenced by biogenic emissions. 相似文献
89.
90.
我国水资源短缺,许多城市都面临着水资源短缺问题。充分利用城市降水资源,实施雨水资源化是一条既经济快捷又广泛有效的途径,并可带来一系列生态环境效应。根据城市下垫面性质的不同,将城市建成区划分为不透水区、园林绿地区和水域区3种类型,分别分析了在这3种下垫面情况下雨水资源的利用方式和利用潜力,提出了城市雨水资源化潜力模型。最后利用逐日降水资料,分析了商丘市2000-2005年城市雨水资源化现实潜力。计算结果表明,商丘市年平均雨水资源化可能潜力为22.94×106m3,现实潜力为18.58×106m3,接近常年城市供水总量的30%。 相似文献