全文获取类型
收费全文 | 352篇 |
免费 | 21篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 53篇 |
地球物理 | 94篇 |
地质学 | 91篇 |
海洋学 | 81篇 |
天文学 | 20篇 |
综合类 | 8篇 |
自然地理 | 15篇 |
出版年
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 13篇 |
2014年 | 10篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 20篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 24篇 |
2007年 | 21篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1964年 | 2篇 |
1959年 | 2篇 |
1953年 | 1篇 |
1942年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有385条查询结果,搜索用时 15 毫秒
71.
Nien-Sheng Hsu Wei-Chen Cheng Wen-Ming Cheng Chih-Chiang Wei William W.-G. Yeh 《Advances in water resources》2008
This paper develops an iterative procedure for capacity expansion studies for water distribution systems. We propose a methodology to analyze an existing water distribution system and identify the potential bottlenecks in the system. Based on the results, capacity expansion alternatives are proposed and evaluated for improving the efficiency of water supply. The methodology includes a network flow based optimization model, four evaluation indices, and a series of evaluation steps. We first use a directed graph to configure the water distribution system into a network. The network flow based model optimizes the water distribution in the system so that different expansion alternatives can be evaluated on a comparable basis. This model lends itself to linear programming (LP) and can be easily solved by a standard LP code. The results from the evaluation tool help to identify the bottlenecks in the water distribution system and provide capacity expansion alternatives. A useful complementary tool for decision making is composed of a series of evaluation steps with the bottleneck findings, capacity expansion alternatives, and the evaluation of results. We apply the proposed methodology to the Tou-Qian River Basin, located in the northern region of Taiwan, to demonstrate its applicability in optimization and capacity expansion studies. 相似文献
72.
Dam overtopping risk assessment considering inspection program 总被引:3,自引:2,他引:1
Jan-Tai Kuo Yung-Chia Hsu Yeou-Koung Tung Keh-Chia Yeh Jian-De Wu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(3):303-313
Safety inspection of large dams in Taiwan is conducted every 5 years. The practice does not take into consideration uncertainty
of dam conditions. The goal of this study is to determine the optimal dam inspection interval under the consideration of overtopping
risk incorporating uncertainty gate availability. In earlier studies, assessment of overtopping risk only considered the uncertainties
in reservoir properties and natural randomness of hydrologic events without giving much thought to the availability of spillway
gates. As a result, the overtopping risk could be underestimated. In this study, an innovative concept is proposed to evaluate
dam overtopping by taking into account spillway gate availability. The framework consists of three parts: (1) evaluation of
conditional overtopping risk for different numbers of malfunctioning spillway gates; (2) evaluation of spillway gate availability;
and (3) dam inspection scheduling. Furthermore, considerations are given to overtopping risk, inspection cost, and dam break
cost for determining the optimal inspection schedule. The methodology is applied to the Shihmen Reservoir in Taiwan and to
evaluate its time-dependent overtopping risk. Results show that overtopping risk considering the availability of the spillway
gates is higher than the one without considering the availability of the spillway gates. 相似文献
73.
大量的数值模拟表明,SVD和LSQRD在面波频散网格反演两步法中的应用效果都很好.但SVD可以用分辨矩阵、信息矩阵和协方差矩阵对解估计进行数学上客观有效的评价;而对于大型稀疏方程组的求解,LSQRD确是一种内存需求小、计算速度快以及分辨抗噪能力都较强的算法 .在现有计算机运算速度较快、内存可以扩充较大的条件下,实测数据量不很大时,应采用SVD算法进行线性反演. 相似文献
74.
利用1994-2013年ERA-Interim及NCEP/NCAR再分析数据,对国家气候中心(BCC)次季节到季节尺度模式(S2S)1994-2013年的回报试验数据进行亚洲季风区准双周振荡(QBWO)预报能力评估,并诊断模式预报误差来源。结果表明:BCC S2S模式对QBWO的预报能力随着预报提前时间的增长而降低,9 d后预报技巧明显减弱,其周期、传播特征和强度出现误差;在提前9 d预报中,印度洋地区QBWO对流-环流系统结构松散,信号偏弱,对流向东传播,这与印度洋平均态的预报误差有关,夏季对流平均态低层水汽场在西太平洋和阿拉伯海较强,而东印度洋、孟加拉湾一带偏弱;西北太平洋地区QBWO具有向西北传播的特征,但强度偏弱,可能原因是预报低估了QBWO对流西北侧低层涡度的超前信号,经涡度方程诊断发现,地转涡度平流正贡献微弱,相对涡度平流在对流西北侧引发负涡度,从而减弱了对流西北侧由低层正涡度引发的有利条件。 相似文献
75.
Abstract This paper explores the dynamics behind the changing regimes of urban renewal and its social impacts in Taiwan. Before the 1980s, the state was willing to solely shoulder the job of urban renewal with a wholly supportive financial budget and land appropriation law, while in the 1990s it became financially overburdened due to its renewal policy. Around the year 2000, the state turned towards promoting urban regeneration as a key business model. Through this historical exposition, the Taiwanese story of state transformation in urban renewal policy brings two issues to the fore. The first issue is the learning process concerning the policy of public-private partnership (PPP) initiatives. Trans-border policy mobility connects and constitutes cities, such as Taipei, with other places, such as London, through visits and seminars attended by policy makers and experts. However, policy transferred from abroad is “localized” in the learning process and used to prioritize the regeneration of public lands in the urban area. The PPP model is transformed in the face of domestic political struggles. The second issue is the social exclusion as a result of property-led regeneration. Rather than playing the role of an impartial institutional moderator, the state privileged landowners and developers and sacrificed the rights of tenants to stay put. By doing so, the state secures political support from landowner-cum-citizens and initiates a political culture of property in which local citizenship is predicated on ownership. 相似文献
76.
The stability of merwinite (Mw) and its equivalent assemblages, akermanite (Ak)+calcite (Cc), diopside (Di)+calcite, and wollastonite (Wo)+monticellite (Mc)+calcite was determined at T=500–900° C and P
f=0.5–2.0 kbar under H2O–CO2 fluid conditions with X
CO
2=0.5, 0.1, 0.05, and 0.02. Merwinite is stable at P
f=0.5 kbar with T>700° C and X
CO
2<0.1. At P
f=2.0 kbar, the assemblage Di+Cc replaces merwinite at all T and X
CO
2 conditions. At intermediate P
f=1 kbar, the assemblage Ak+Cc is stable above 707° C and Wo+Mc+Cc is stable below 707° C. The univariant curve for the reaction Di+Cc=Wo+Mc+CO2 is almost parallel to the T axis and shifts to low P
f with increasing X
CO
2, with the assemblage Di+Cc on the high-P
f side. The implications of the experimental results in regard to contact metamorphism of limestone are discussed using the aureole at Crestmore, California as an example. 相似文献
77.
Te-Hsien Lin Ching-Hua Lo Sun-Lin Chung Fang-Jui Hsu Meng-Wan Yeh Tung-Yi Lee Jian-Qing Ji Yi-Zhau Wang Dunyi Liu 《Journal of Asian Earth Sciences》2009,34(5):674-685
We conducted a comprehensive 40Ar/39Ar geochronological study of the Jiali and Gaoligong shear zones to obtain a better understanding of crustal deformation and tectonic evolution around the Eastern Himalayan Syntaxis (EHS). The new age data reveal that the main phase of deformation in the Jiali and Gaoligong shear zones occurred from 22 to 11 Ma and from 18 to 13 Ma, respectively. Structural data collected during this study indicate that the Jiali shear zone underwent a change in shear sense from sinistral to dextral during its movement history. Based on a comparison with the deformation histories of other major shear zones in the region, we argue that the initial sinistral motion recorded by the Jiali shear zone was coincident with that of the Ailao Shan–Red River shear zone, which marked the northern boundary of the southeastward extrusion of the Indochina block during the Early Miocene. From the Middle Miocene (~18 Ma), the Jiali shear zone changed to dextral displacement, becoming linked with the dextral Gaoligong shear zone that developed as a consequence of continued northward indentation of the Indian continent into Asia. Since this time, the Jiali and Gaoligong shear zones have been united, defining the southwestern boundary of the EHS during clockwise rotation of the eastward-extruding Tibetan block, as revealed by recent GPS data. The temporal change in regional deformation pattern from southeastward block extrusion to clockwise rotation of crustal fragments may have played an important role in the development of the eastern Himalayan drainage system around the EHS. 相似文献
78.
Evaluation of Hydraulic Properties of Aquitards Using Earthquake‐Triggered Groundwater Variation
下载免费PDF全文
![点击此处可从《Ground water》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shih‐Jung Wang Kuo‐Chin Hsu Chein‐Lee Wang Wen‐Chi Lai Liang‐Tzu Hsu 《Ground water》2017,55(5):747-756
The hydraulic properties of aquitards are not easily obtained because monitoring wells are usually installed in aquifers for groundwater resources management. Earthquake‐induced crust stress (strain) triggers groundwater level variations over a short period of time in a large area. These groundwater anomalies can be used to investigate aquifer systems. This study uses a poroelastic model to fit the postseismic variations of groundwater level triggered by the Chi‐Chi earthquake to evaluate the hydraulic properties of aquitards in the Jhoushuei River alluvial fan (JRAF), Taiwan. Six of the adopted eight wells with depths of 70 to 130 m showed good agreement with the recovery theory. The mean hydraulic conductivities (K) of the aquifers for the eight wells are 1.62 × 10?4 to 9.06 × 10?4 m/s, and the thicknesses are 18.8 to 46.1 m. The thicknesses of the aquitards are 11.3 to 42.0 m. Under the isotropic assumption for K, the estimated values of K for the aquitards are 3.0 × 10?8 to 2.1 × 10?6 m/s, corresponding to a silty medium. The results match the values obtained for the geological material of the drilling core and those reported in previous studies. The estimated values were combined with those given in previous studies to determine the distribution of K in the first two aquitards in the JRAF. The distribution patterns of the aquitards reflect the sedimentary environments and fit the geological material. The proposed technique can be used to evaluate the K value of aquitards using inverse methods. The inversion results can be used in hydrogeological analyses, contaminant modeling, and subsidence evaluation. 相似文献
79.
80.
Dr. L. C. Hsu 《Mineralogy and Petrology》1992,47(1):87-101
Summary Bastnaesites of Ce and La and their OH-analogs were synthesized and their stability relations were determined atPf = 1 kbar andT = 400 to 900°C in a part of the system (Ce,La)-F-H-C-0. The initial fluid compositions were such that
and HF/(HF + H2O) ratios were 0 to 0.172. XRD and IR studies indicate that bastnaesites equilibrated in initial fluids low in HF are all F-enriched. The hydroxylbastnaesite-(La) is stable up to 810°C and the fluorbastnaesite-(La) is stable up to 860°C. Their condensed breakdown products are La2O2CO3 and LaOF, respectively. The stability of Ce bastnaesites is slightly
dependent. The hydroxylbastnaesite-(Ce) is stable up to 660°C at the
defined by the IQF buffer and up to 640°C by the MH buffer. The fluorbastnaesite-(Ce) is stable up to 800°C at the
defined by the IQF and up to 760°C by the MH buffer. The condensed breakdown product for the hydroxyl end-member is simply CeO2 but for the fluorine one is a combination of CeO2, CeF3, and CeOF. Factors, such as OH vs F,
, and bulk composition, that affect the stability of individual species are discussed. Petrogenic implications resulting from the present study include that bastnaesites can be stable from hydrothermal to magmatic conditions, that F-enriched species can form in an environment relatively low in F content, and that OH-species are rare and occur only in low-temperature environments essentially devoid of F.
With 8 Figures 相似文献
Synthese und Stabilität von Bastndsil in einem Teil des Systems (Ce,La)-F-H-C-O
Zusammenfassung Ce- und La-Bastnäsite, sowie deren OH-Analoga wurden synthetisiert und ihre Stabilitätsbeziehunger beiP f = 1 kbar undT = 400 bis 900°C wurden im System (Ce,La)F-H-C-O bestimmt. Die anfänglichen Flüssigkeitszusammensetzungen waren so, daß und die HF/(HF + H2O)-Verhältnisse 0–0.172 waren. Röntgenpulver- und Ultrarot-Untersuchungen zeigten, daß Bastnäsite, die mit anfänglich HF-armen Flüssigkeiten equilibriert wurden, alle an F angereichert sind. Hydroxilbastndsit-(La) ist bis 810°C und Fluorbastnäsit-(La) bis 860°C stabil. Ihre festen Zersetzungsprodukte sind La2O2O3, bzw. LaOF. Die Stabilität der Ce-Bastnäsite hängt etwas von ab. Hydroxilbastnäsit-(Ce) ist bei des Eisen-Quarz-Fayalit-Puffers bis 660°C stabil und mit Magnetit-Hämatit-Puffer bis 640°C. Das feste Zerfallsprodukt ist für das Hydroxil-Glied nur CeO2, für das Fluor-Glied eine Mischung aus CeO2, CeF3 und CeOF. Faktoren, welche die Stabilität der einzelnen Spezies beeinflussen, werden diskutiert, wie das Verhältnis OH zu F, und die Gesamtzusammensetzung. Petrogenetische Folgerungen aus der vorliegenden Studie schließen ein, daß Bastnäsite von hydrothermalen bis zu magmatischen Bedingungen stabil sein können, daß sich an F angereicherte Glieder in relativ F-armer Umgebung bilden können, und daß OH-Glieder selten sind und nur unter Bildungsbedingungen niedriger Temperatur und weitgehender Abwesenheit von F auftreten.
With 8 Figures 相似文献