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391.
392.
Post-mine metal transport and attenuation in the Keno Hill mining district, central Yukon, Canada 总被引:6,自引:0,他引:6
The Keno Hill mining district in central Yukon was the second largest silver producer in Canada with mines operating from
1913 to 1989 on more than 65 vein silver deposits. The seven and a half decades of mining activities have generated large
volumes of mine waste disposed on the land surface, resulting in elevated metal contents in numerous small drainages. To assess
the extent of metal mobilization, old mine workings and the associated mine waste were examined and the water courses draining
to a major river valley sampled. The results of field observations and an array of water and sediment analyses led to three
major conclusions. 1. Acid mine drainage is not widespread because of galvanic protection of pyrite from oxidative dissolution
and neutralization by carbonates in the country rock. 2. Mechanisms operative to limit aqueous metal transport in small streams
in the district include cryogenic precipitation, coprecipitation and sorption. 3. The near-surface concentration of metals
limits the options of waste disposal in future mining developments due to potential metal-leaching problems.
Received: 12 December 1995 · Accepted: 26 March 1996 相似文献
393.
Study of evaporation and recharge in desert soil using environmental tracers, New Mexico, USA 总被引:4,自引:0,他引:4
The purpose of this study is to investigate the rates and mechanisms of recharge and evaporation in soils of a desert environment
using two environmental tracers (chloride and oxygen-18). The profiles of chloride concentration and oxygen-18 enrichment
in soil-water, together with the depth distribution of water content in soil, reveal information about long-term recharge
and instantaneous evaporation processes without needing to know the physical properties of the soil. Three holes were hand-augured,
in different desert settings in southeastern New Mexico. The chloride concentration profiles were used, with the chloride
mass balance method, to estimate long-term recharge rates in these three holes as 0.5, 0.8, and 2.4 mm yr–1. Analysis using a bimodal flow and transport model shows that possibly 85% of the recharge occurs via movement of water through
preferred pathways in the root zone. Preferential flow was evident in all three sampling sites. Clay layers have a noticeable
effect on the development of water content distribution and thus on oxygen-18 enrichment and chloride concentration profiles.
The spatial variation in clay layering partly explains the variation in recharge rate estimates.
Received: 13 October 1995 · Accepted: 15 November 1995 相似文献
394.
晋西北地区末次盛冰期古风成砂的发现及环境演化 总被引:6,自引:1,他引:6
野外调查中在晋西北地区首次发现了马兰黄土中的古风成砂沉积,其机械组成主要是极细砂和细砂,而且具有明显的风成交错层理等特征。结合年代资料和孢粉分析,认为古风成砂形成于27000~10000aB.P.间的末次冰期盛冰期,当时晋西北地区是干旱荒漠-干草原景观,气候寒冷干燥,风的地质作用成为控制该区环境变化的主要动力因素,沙漠化土地迅速扩展或沙漠大范围地南侵,说明该区土地沙漠化过程至少在晚更新世晚期就已断续存在 相似文献
395.
概略介绍了国外勘查地球物理工作的现状和某些发展趋势,其中着重介绍利用地球物理方法进行区域地质调查和地壳、上地幔调查、寻找深部隐伏矿床、计算矿产储量和研究环境地质问题.还提到勘查地球物理方法技术的重大进展.在介绍现状的同时,力图指出勘查地球物理的一些新的应用领域、新的方法技术和发展思路. 相似文献
396.
本文通过对青海省各林区林火的区域划分、时间分布以及林火与气象因子的关系进行分析,找出了能较好反映青海省林火发生规律的天气指标,建立了气象因子与林火险级的定量关系。 相似文献
397.
蒙脱石层间域的性质及其环境意义 总被引:28,自引:0,他引:28
蒙脱石矿物是土壤中比表面积大、分布很广的一种粘土矿物,也是土壤中主要的活性组分之一。蒙脱石层间域是一个特殊的化学反应场所。系统地评述了无机、有机阳离子、农药分子在蒙脱石层间域中的吸附、脱附、氧化还原、催化降解等反应机理,并指出它们的环境化学行为对环境的影响和意义。 相似文献
398.
M. Ross 《Environmental Geology》1995,26(3):182-188
It is estimated that nearly $100 billion has been spent on removal of asbestos-bearing materials from schoolrooms, public and commercial buildings, and homes. This removal continues to this day despite the publication of an advisory document in 1990 by the US Environmental Protection Agency that states most removal is unnecessary and is even counterproductive both in terms health protection and costs. Concern over low exposure to substances that are designated as carcinogens is based on the false concept that even the smallest exposure to such substances can increase cancer risk. The expression one molecule of a chemical or one asbestos fiber can possibly produce a tumor is repeated over and over until it is accepted as a truth. Over 1400 air samples taken in 219 North American school buildings show the average fiber level to be 0.00022 fibers per milliliter of air. Using the most pessimistic models and attendance in the school for 6 h a day, five days a week, for 14 years, the calculated risk is one excess cancer death per million lifetimes. In contrast, the risk of dying from a lightning strike is 35 deaths per million lifetimes. Ambient air asbestos concentrations measured in the chrysotile asbestos mining towns of Quebec are 220 to 2200 times greater than that measured in the average schoolroom, yet the women living their entire lives in these towns show no increased cancer risk. The asbestos abatement program in the United States is a public policy debacle. 相似文献
399.
沉积物污染和环境沉积学 总被引:44,自引:2,他引:44
环境沉积学着重研究人类活动与沉积循环(包括风化作用、侵蚀作用、沉积作用和早期成岩作用)相互间的影响,寻求人类与自然协调发展的更佳方式。现在,全球河流、湖泊和海洋中沉积物污染严重,沉积学家应予以关注并为解决由此所产生的环境问题做出贡献。实际上,为了对沉积物环境质量进行评估和治理被污染的环境,需要沉积学家去研究污染物的时空分布与岩相、沉积相和沉积体系之间的相互关系,研究污染物在沉积作用和早期成岩作用中的行为,研究沉积物中污染物的存在形式等重要课题。 相似文献
400.
Responding to China's major environmental challenges, researchers are increasingly exploring dynamics between international non-governmental organisations, the nation-state, and local communities. Much less understood are domestic environmental non-governmental organisations (eNGOs) and their interactions with actors across scales. This paper responds by exploring domestic eNGOs and interactions with institutional actors, including international donors, and with levels of Chinese government. The practices of eNGOs in China are influenced by interactions at various scales. Rather than being directly influenced by international partners and simply constrained by state regulations, Chinese eNGOs are embedded in more complex power relations. These interrelationships are exemplified in the operations of Green Watershed, a domestic eNGO working in Yunnan Province. Green Watershed has extensive interactions with international donors and various levels of government as a result of its national campaign and long-term local projects. Relationships between eNGOs’ international donors and the Chinese government are significant in influencing eNGO practice. NGO–government relations in China are inconsistent and constantly changing owing to the diverse interests and priorities of the various levels of government. The impacts of the local practice of Chinese eNGOs are deeply informed by their relationships both at and beyond the local level. Complex interrelationships make it difficult to achieve bottom-up, participatory resource management in China. 相似文献