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151.
1IntroductionPopulation growth has created escalating pressureson our resources(natural,humanandsocial)onlocal,regional,and global scales.These pressures negativelyi mpact the natural environment,our communities andthe quality of our lives.In the face of …  相似文献   
152.
陈祥 《盐湖研究》2002,10(4):44-47
提出了青海盐湖钾肥公司据生产需要 ,开辟新的采卤区后 ,卤水组份发生变化问题。根据分析与试验探讨了CaCl2 在盐田生产中的影响及应采取的措施  相似文献   
153.
The purpose of this article is to investigate a possible use of lime for the stabilization of base soils underlying salt evaporation ponds in Çamalt? Solar Marine Salt Plant. The plant is located on the old Gediz River Delta, on the north shore of the Izmir Bay-Turkey, where alluvial deltaic soft marine sediments constitute the local soil condition. The low bearing capacity of the pond base soils results in some problems on the mechanical harvest of the solar salt. Therefore, stabilization was taken into consideration for improving the productivity of the salt plant. For this purpose, bench-scale laboratory tests were performed on the specimens that had been sampled from the bases of the salt evaporation pond to investigate the influence of lime on the unconfined compressive strength (UCS) of these marine sediments. By interpreting the pH test results and consistency limits of the lime stabilized soils, optimum lime content was determined as 8%. The verification of the long-term pozzolanic reactions for the optimum lime content was conducted by performing UCS tests with up to six months curing periods, along with the microstructural analysis through X-ray diffraction analysis (XRD) and a scanning electron microscope (SEM). Long-term tests revealed that the optimum lime content successfully sustained the required pozzolanic reactions, and a strength gain of 500% was achieved for a six-month curing period.  相似文献   
154.
Brazil is the largest economy in Latin America and the world's leading producer and exporter of coffee. Smallholders are the predominant producers of Brazilian coffee and have been significantly impacted by post-ISI (import substitution industrialisation) neoliberal reforms that swept the nation's agricultural sector beginning in the 1980s. These reforms stimulated increased coffee production while simultaneously diminishing state interventions, including agricultural subsidies, farmer credits, research and development programmes, extension services, and rural development initiatives. These changes were closely followed by major restructuring of the global coffee market and the elimination of international coffee export quotas. Our research joins a growing body of recent literature exploring how changes related to market liberalisation and globalisation affect localities and regions where producers supply coffee for conventional markets. Through a case study, we describe the impacts of neoliberal globalisation on the lives, livelihoods, and environment of small-scale coffee producers in Minas Gerais, Brazil. We explore how neoliberal reform, reflected in the specific historical, geographical, and environmental context of Brazilian coffee production, has resulted in the increased marginalisation of small-scale farmers, the degradation of soils, and overall rural decline.  相似文献   
155.
1 INTRODUCTIONAccording to historical records, there has existed the large-area desert in the northwest of China for a long time, which formed in the geologic age and historical periods, and continuously evolved because of climate changes and human activities. Although a certain amount of achievement has been obtained since the 1950s, land desertification went on expanding quickly. For desertification by wind erosion, the average expansion speed was 1560km2 per year from the late 1950s …  相似文献   
156.
157.
黄淮海平原农区土地利用转型及其动力机制(英文)   总被引:7,自引:0,他引:7  
Land use transition refers to changes in land use morphology, including dominant morphology and recessive morphology, of a particular region over a period of time driven by various factors. Recently, issues related to land use transition in China have attracted interest among a wide variety of researchers as well as government officials. This paper examines the patterns of land use transition and their dynamic mechanism in the Huang-Huai-Hai Plain during 2000–2010. First, the spatio-temporal patterns of land use transition, their characteristics and the laws governing them were analyzed. Second, based on the established conceptual framework for analyzing the dynamic mechanism of land use transition, a spatial econometric regression analysis method was used to analyze the dynamic mechanism of the five types of major land use transition in the Huang-Huai-Hai Plain at the county level. Land use pattern changes in the study area were characterized by an increase in construction land, water body and forested land, along with a decrease in farmland, unused land and grassland. The changes during 2000–2005 were much more significant than those during 2005–2010. In terms of factors affecting land use transitions, natural factors form the basis, and they have long-term effects. Socio-economic factors such as population and GDP, however, tend to determine the direction, structure, size and layout of land use transition over shorter time periods. Land law and policy factors play a mandatory guiding and restraining role in land use transitions, so as to improve the overall efficiency of land use. Land resource engineering is also an important tool to control land use transitions. In general, the five types of major land use transition were the result of the combined action of various physical, social and economic factors, of which traffic condition and location condition had the most significant effects, i.e. they were the common factors in all land use transitions. Understanding the spatio-temporal process of land use transitions and their dynamic mechanisms is an important foundation for utilizing land resources, protecting regional ecological environment and promoting sustainable regional socio-economic development.  相似文献   
158.
Nutrient and Chlorophyll-a (Chl-a) concentrations were investigated monthly along three transects extending from a mariculture area to open waters around the Zhangzi Island area from July to December 2009. The objective of this study is to illustrate food availability to the bottom-sowed scallop Patinopecten yessoensis under the influences of the Yellow Sea Cold Water Mass (YSCWM), freshwater input and feedbacks of cultivated scallops. Significant thermal stratification was present in open waters from July to October, and salinity decreased in July and August in surface layers in the mariculture area. Nutrient concentrations increased with depth in both areas in summer, but were similar through water column in November and December. On average, nutrient increased from summer to autumn in all components except ammonia. Nutrient concentrations lower than the minimum thresholds for phytoplankton growth were present only in upper layers in summer, but stoichiometric nitrogen limitation existed in the entire investigation period. Column-averaged Chl-a concentration was lower in open waters than in mariculture area in all months. It increased significantly in mariculture area in August and October, and was less variable in open waters. Our results show that nutrients limitation to phytoplankton growth is present mainly in upper layer in association with stratification caused by YSCWM in summer. Freshwater input and upwelling of nutrients accumulated in YSCWM can stimulate phytoplankton production in mariculture area. Farming activities may change stoichiometric nutrient ratios but have less influence on Chl-a concentration.  相似文献   
159.
Fifty years ago, the Forge River and Moriches Bay, of Long Island’s south shore lagoonal system, achieved notoriety when their polluted conditions were alluded to in a report of the US President’s Science Advisory Committee (1965). The Woods Hole Oceanographic Institution investigated the bay throughout the 1950s, identifying duck farming as the cause of “objectionable”, “highly contaminated” conditions of these waters.Much has changed: duck farming declined; the river was dredged to remove polluted sediments, improve navigation; and barrier island inlets stabilized. Yet, the river remains seasonally eutrophic.Why? This paper reviews what occurred in the Forge River watershed. While governments aggressively curtailed the impacts of duck pollution, they failed to manage development and sewage pollution. The Forge experience indicates that watershed management is a continuing governmental responsibility as development accelerates. Otherwise, we will always be looking for that instantaneous remediation that is usually not affordable and is socially contentious.  相似文献   
160.
层次分析法(AHP)在尾矿库安全运行分析中的应用   总被引:9,自引:1,他引:8  
王涛  侯克鹏  郭振世  张成良 《岩土力学》2008,29(Z1):680-686
尾矿库是用于堆存金属非金属矿山进行矿石选别后排出尾矿的场所,是一种高势能的人造泥石流源,一旦发生事故将会严重威胁到库区周边环境和下游居民的生命及财产安全。考虑到我国小型尾矿库数量多、安全度水平低以及尾矿库发生事故的复杂性、多样性及不确定性等特点,根据影响尾矿库安全运行的因素建立层次结构模型,运用Delphi法构造相关因素的各层次判断矩阵,应用定性与定量相结合的层次分析法进行分析,最后确定出各影响因素的权重并进行总排序。结果表明,在尾矿库运行期间排洪系统对其整体安全影响最大,其次为筑坝堆存系统、尾矿库管理与维护、回水系统和尾矿输送系统。该研究结果可以为相关单位制定合理的安全防范措施提供必要的参考价值,从而有针对性的消除各种事故隐患,提高安全管理水平,确保尾矿库的安全运行。  相似文献   
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