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961.
Hydraulic and flood-loss modeling of levee,floodplain, and river management strategies,Middle Mississippi River,USA 总被引:2,自引:2,他引:2
In this investigation, four scenarios were used to quantify the balance between the benefits of levees for flood protection
and their potential to increase flood risk using Hazards U.S. Multi-Hazard flood-loss software and hydraulic modeling of the
Middle Mississippi River (MMR). The goals of this study were (1) to quantify the flood exposure under different flood-control
configurations and (2) to assess the relative contributions of various engineered structures and flood-loss strategies to
potential flood losses. Removing all the flood-control structures along the MMR, without buyouts or other mitigation, reduced
the average flood stages between 2.3 m (100-year flood) and 2.5 m (500-year), but increased the potential flood losses by
$4.3–6.7 billion. Removing the agricultural levees downstream of St. Louis decreased the flood stages through the metro region
by ~1.0 m for the 100- and 500-year events; flood losses, without buyouts or other mitigation, were increased by $4.3–6.7 billion. Removing the agricultural levees downstream of St. Louis decreased the flood stages through the metro region
by ~1.0 m for the 100- and 500-year events; flood losses, without buyouts or other mitigation, were increased by 155 million
for the 100-year flood, but were decreased by $109 million for the 500-year flood. Thus, agricultural levees along the MMR
protect against small- to medium-size floods (up to the ~100-year flood level) but cause more damage than they prevent during
large floods such as the 500-year flood. Buyout costs for the all the buildings within the 500-year floodplain downstream
of urban flood-control structures near St. Louis are ~40% less than the cost of repairing the buildings damaged by the 500-year
flood. This suggests large-scale buyouts could be the most cost-effective option for flood loss mitigation for properties
currently protected by agricultural levees. 相似文献
962.
Elizabeth Holcombe Sarah Smith Edmund Wright Malcolm G. Anderson 《Natural Hazards》2012,61(2):351-385
Despite the recognition of the need for mitigation approaches to landslide risk in developing countries, the delivery of ‘on-the-ground’
measures is rarely undertaken. With respect to other ‘natural’ hazards, it is widely reported that mitigation can pay. However,
the lack of such an evidence base in relation to landslides in developing countries hinders advocacy amongst decision makers
for expenditure on ex-ante measures. This research addresses these limitations directly by developing and applying an integrated
risk assessment and cost–benefit analysis of physical landslide mitigation measures implemented in an unplanned community
in the Eastern Caribbean. In order to quantify the level of landslide risk reduction achieved, landslide hazard and vulnerability
were modelled (before and after the intervention), and project costs, direct and indirect benefits were monetised. It is shown
that the probability of landslide occurrence has been substantially reduced by implementing surface-water drainage measures
and that the benefits of the project outweigh the costs by a ratio of 2.7–1. This paper adds to the evidence base that ‘mitigation
pays’ with respect to landslide risk in the most vulnerable communities—thus strengthening the argument for ex-ante measures.
This integrated project evaluation methodology should be suitable for adoption as part of the community-based landslide mitigation
project cycle, and it is hoped that this resource, and the results of this study, will stimulate further such programmes. 相似文献
963.
Katsushi Sato 《Mathematical Geosciences》2012,44(5):635-644
Recent stress tensor inversion methods for fault-slip analysis are used to distinguish between multiple stress states to elucidate spatiotemporal change of the earth’s crustal tectonics. An estimator named the stress difference has been a practicable tool to measure the difference between stress solutions of inversion analysis. This measure corresponds to the expected difference in shear stress direction on a randomly oriented fault plane, which is, however, an approximation including several degrees of deviation. This study investigated the formula of stress difference and found the exact physical meaning, specifically the expected difference in shear stress vector which carries information on magnitude as well as direction. The present discovery is based on the analytical proportionality between the second invariant of stress tensor and the root mean square magnitude of shear stress for all orientation of fault planes. The meaningless difference in non-dimensional shear stress magnitude was found to be incorporated into the value of stress difference. This fact is not convenient for fault-slip analysis dealing only with orientations. 相似文献
964.
965.
Shen Weizhou Zhang Bangtong Ling Hongfei Lai Mingyuan Yang Jiedong Tao Xiancong 《《地质学报》英文版》1992,66(2):165-176
Nd, Sr and O isotopic study on the spilite-keratophyre sequence in Xiqiu shows that its ∈_(Nd) values are inthe range of 4.02-5.26, and its ∈_(Sr) values, +1.4-2.6. According to the points of these data in the ∈_(Nd)-T,∈_(Sr)-T and ∈_(Nd)-∈_(Sr) diagrams, the spilite-keratophyre is interpreted as being slightly contaminated by crustalmaterials. Its δ~(18)O values are 3.9-5.0‰. The depletion of ~(18)O in the rocks resulted from the influence ofseawater hydrothermal alteration during or soon after the rock formation. Based on the isotopic characteristicsand available geochemical data, it is believed that the spilite-keratophyre was formed in the well-developedisland-arc environment during the Late Proterozoic subduction of the palaeo-Pacific plate beneath thesoutheastern margin of the Yangtze massif. 相似文献
966.
The Wenchuan Earthquake (May 12, 2008), Sichuan Province,China, and resulting geohazards 总被引:14,自引:5,他引:14
Peng Cui Xiao-Qing Chen Ying-Yan Zhu Feng-Huan Su Fang-Qiang Wei Yong-Shun Han Hong-Jiang Liu Jian-Qi Zhuang 《Natural Hazards》2011,56(1):19-36
On Monday, May 12, 2008, a devastating mega-earthquake of magnitude 8.0 struck the Wenchuan area, northwestern Sichuan Province,
China. The focal mechanism of the earthquake was successive massive rock fracturing 15 km in depth at Yingxiu. Seismic analysis
confirms that the major shock occurred on the Beichuan–Yingxiu Fault and that aftershocks rapidly extended in a straight northeast–southeast
direction along the Longmenshan Fault zone. Fatalities approaching a total of 15,000 occurred, with a significant number resulting
from four types of seismically triggered geohazards—rock avalanches and landslides, landslide-dammed lakes (“earthquake lakes”),
and debris flows. China Geological Survey has identified 4,970 potentially risky sites, 1,701 landslides, 1,844 rock avalanches,
515 debris flows, and 1,093 unstable slopes. Rock avalanches and landslides caused many fatalities directly and disrupted
the transportation system, extensively disrupting rescue efforts and thereby causing additional fatalities. Landslide-dammed
lakes not only flooded human habitats in upstream areas but also posed threats to potentially inundated downstream areas with
large populations. Debris flows become the most remarkable geohazards featured by increasing number, high frequency, and low
triggering rainfall. Earthquake-triggered geohazards sequentially induced and transformed to additional hazards. For example,
debris flows occurred on rock avalanches and landslides, followed by landslide-dammed lakes, and then by additional debris
flows and breakouts of the landslide-dammed lakes and downstream flooding. Earthquake-induced geohazards occurred mainly along
the fault zone and decreased sharply with distance from the fault. It can be anticipated that post-earthquake geohazards,
particularly for debris flows, will continue for 5–10 years and even for as long as 20 years. An integrated strategy of continuing
emergency response and economic reconstruction is required. The lesson from Wenchuan Earthquake is that the resulted geohazards
may appear in large number in active fault regions. A plan for geohazard prevention in the earthquake-active mountainous areas
is needed in advance. 相似文献
967.
Jayalakshmi Devi Oinam AL. Ramanathan Anurag Linda Gurmeet Singh 《Environmental Earth Sciences》2011,62(6):1183-1195
The presence of arsenic (As) in groundwater and its effect on human health has become an issue of serious concern in recent
years. The present study assessed the groundwater quality of the Bishnupur District, Manipur, with respect to drinking water
standards. Higher concentrations of pH, iron and phosphate were observed at several locations. Phosphate and iron levels were
highest in the pre-monsoon, followed by monsoon and post-monsoon seasons. The arsenic concentrations were highest during post-monsoon
(1–200 μg L−1) as compared to pre-monsoon (1–108 μg L−1) and monsoon (2–99 μg L−1). Kwakta and Ngakhalawai show higher levels of arsenic concentration as compared to the prescribed World Health Organization
(WHO) and Bureau of Indian Standards (BIS) norms. Arsenic showed a strong positive correlation with phosphate and negative
correlation with sulphate, suggesting a partial influence of anthropogenic sources. The study suggests that the Bishnupur
area has an arsenic contamination problem, which is expected to increase in the near future. 相似文献
968.
黄铁矿型结构的晶体化学 总被引:2,自引:0,他引:2
本文根据特征离子坐标变化的特点,对黄铁矿型结构微变规律性进行了讨论,作了一些规律图,总结出:成分的变化控制着u值的变化,u值的变化影响着晶体结构微变化。u值发生变化,MX6反三方柱的顶面和底面中3轴相向或相背移动,u值增加愈接近正八面体,u值发生变化,X(M3X)三方锥底面的方位不变,但锥顶(X7)和锥体内的(X1)的坐标要变化,它们会沿着锥的中轴线相向或相背移动,形成扁平型的三方锥,最后得出:当 相似文献
969.
Xiao-hui Tan Xian-en Wang Xiao-jun Hu Meng-fen Shen Na Hu 《Geotechnical and Geological Engineering》2016,34(5):1283-1292
Two methods of reliability analysis of soil slopes are studied, and the representative flow charts of both methods are illustrated. Method 1 can predict the reliability index and the critical probabilistic slip surface directly and it is computational efficient, but it needs the development of new codes for integrating the reliability analysis code and the slope stability code. Method 2 makes the reliability analysis code call the slope stability analysis code directly, and each code can be considered as an intact part. The main result of Method 2 is the reliability index of soil slope. Combined with the proposed method for locating the critical slip surface, Method 2 can also predict the probabilistic slip surface. Although Method 2 needs much more callings of the subprogram of slope stability analysis code, it needs not the developing of new computer program. Thus, Method 2 is easy to use and can be applied to different reliability analysis methods and slope stability analysis methods. 相似文献
970.
Despite the importance of organic-rich shales, microstructural characterization and theoretical modeling of these rocks are limited due to their highly heterogeneous microstructure, complex chemistry, and multiscale mechanical properties. One of the sources of complexity in organic-rich shales is the intricate interplay between microtextural evolution and kerogen maturity. In this study, a suite of experimental and theoretical microporomechanics methods are developed to associate the mechanical properties of organic-rich shales both to their maturity level and to the organic content at micrometer and sub-micrometer length scales. Recent results from chemomechanical characterization experiments involving grid nanoindentation and energy-dispersive X-ray spectroscopy (EDX) are used in new micromechanical models to isolate the effects of maturity levels and organic content from the inorganic solids. These models enable attribution of the role of organic maturity to the texture of the indented material, with immature systems exhibiting a matrix-inclusion morphology, while mature systems exhibit a polycrystal morphology. Application of these models to the interpretation of nanoindentation results on organic-rich shales allows us to identify unique clay mechanical properties that are consistent with molecular simulation results for illite and independent of the maturity of shale formation and total organic content. The results of this investigation contribute to the design of a multiscale model of the fundamental building blocks of organic-rich shales, which can be used for the design and validation of multiscale predictive poromechanics models. 相似文献