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991.
基于农户行为的耕地质量评价指标体系 构建的理论与方法 总被引:23,自引:0,他引:23
从农户土地利用目标变化相关理论出发, 依据在不同经济发展阶段下, 农户土地利用目 标的产量最大化、产量与利润最优化和利润最大化三个阶段的变化特征, 创建了基于农户土地利 用目标变化的“压力- 状态- 效应- 响应”逻辑框架模型; 并据不同经济发展阶段下的“压力- 状态- 效应- 响应”的变化特征, 构建了基于农户土地利用目标变化的耕地质量评价指标体系。这一评价 指标体系的建立为我国在不同经济发展阶段下, 从农户尺度上进行耕地质量保护提供政策依据。 相似文献
992.
沙漠绿洲多功能高分子植物生长调节剂籽瓜增产和品质改善研究 总被引:1,自引:0,他引:1
选择适合当地土壤和生态环境特点的优质高产籽瓜品种——新籽瓜1号,进行甘肃省武威市民勤沙漠绿洲多功能高分子植物生长调节剂籽瓜根部追施增产和品质改善试验研究。结果显示,施用产品不但有利于籽瓜的营养和生殖生长,增加瓜径3%~5%、提高产量11.5%,而且显著改善籽瓜的品质,提高其粗蛋白和维生素B1、B2含量,分别比对照增加1.80%和29.41%、14.29%,因而产生较好的经济效益,净增产值358.95~580.95元·hm-2。 相似文献
993.
994.
根据大量公路软基处理的施工实践,提出了公路软基处理施工质量的综合控制方法。实践表明,从软基处理的施工机械、原材料、施工安排、施工过程、施工效率、成品检验、制度威慑等方面进行公路软基施工质量综合控制是有效的,也是必要的。 相似文献
995.
Groundwater contamination due to accidental releases of mono- and polycyclic aromatic compounds (MAHs and PAHs) from decommissioned
manufactured-gas plants is an ongoing and litigious problem. The MAHs and PAHs are derived from coal tar, which was a by-product
of the gas-manufacturing process. While originally designed to contain coal tar, the manufactured-gas plant structures that
remain today have often degraded over time and are not completely leak-proof. Over a period of many years, subsurface water
has seeped into and out of the structures, resulting in groundwater contamination. This was particularly true once the tops
of the structures were removed. In this study, process-based simulations were conducted to estimate the groundwater-quality
impacts of accidental releases of dissolved naphthalene (C10H8) from the sites of three former manufactured-gas plants. The results from one-dimensional, transient, unsaturated, near-surface
fluid-flow and solute-transport simulations served as input to three-dimensional saturated subsurface fluid-flow and solute-transport
simulations. The simulation results and sensitivity analysis reported here indicate that accidental releases of naphthalene
had significant, negative impacts on groundwater quality at each of the three sites.
Electronic Publication 相似文献
996.
997.
The establishment of local self-government was a key part of the post-1989 transformation in East and Central Europe. Local
government in both Western and East and Central Europe has increasingly been expected to play a role in local economic development
(LED). Local government is one important agent in the complex processes of building 'institutional thickness' to ensure the
development of local economies and the quality of life of inhabitants. This paper presents the results of a national postal
questionnaire survey of the LED role of the lowest level of local self-government in Poland, the gmina or commune. The paper
establishes a baseline of knowledge regarding: the local economic problems faced by communes; their attitudinal, strategic
and organisational responses; and the main factors which are hindering the communes' LED role.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
998.
999.
Md. Mokhlesur Rahman Muhammad Qumrul Hassan Mohammad Saiful Islam S. Z. K. M. Shamsad 《Environmental Geology》2000,40(1-2):31-40
This paper deals with an environmental impact assessment of low water flow in the river Ganges during a dry period at the
Khulna and Mongla port areas in south-western Bangladesh. Large-scale surface water withdrawal in India after commissioning
the Farakka Barrage causes a drastic fall in the Ganges low-flow condition within the Bangladesh territory during every dry
period. The average lowest discharge in the Ganges is 552 m3/s, which is about 73% less than that in the pre-Farakka time. This has caused the deterioration of both surface and groundwater
quality of the study area. Salinity is the principal cause of water quality degradation in the area. Present observation shows
that the surface water of the area is sulphate-chloride dominated, which signifies high salinity whereas the groundwater is
categorized as of medium to high salinity. To maintain the Rupsa River's maximum salinity below 1000 μS/cm the discharge in
the Ganges should be ∼1500 m3/s, whereas that at Garai basin is ∼10 m3/s. If this present situation continues it will be a crippling blow to the environment of the area in the long term. An integrated
multidisciplinary approach to hydrogeological research is urgently required to salvage the area from further deterioration.
Received: 9 August 1999 · Accepted: 8 March 2000 相似文献
1000.
Lake and reservoir water quality affected by metals leaching from tropical soils, Bangladesh 总被引:2,自引:0,他引:2
Md. R. Islam W. P. Lahermo R. Salminen S. Rojstaczer V. Peuraniemi 《Environmental Geology》2000,39(10):1083-1089
The release of metals during weathering has been studied in order to assess its geochemical controls and possible effects
on environmental health in Bangladesh. A total of 27 soil samples and 7 surface water samples were collected from four locations
covering three major regions in the country. Results show that weathering effects are a strong function of climatic conditions.
Surface waters are typically enriched in Al, Mg, Ca, Na, K, As, Ba, Cr, Cu, Ni, Pb and Zn. The solubility of metal ions, organometallic
complexes, co-precipitation or co-existence with the colloidal clay fraction are the main processes that lead to metal enrichment
in lake and reservoir water. Aluminium concentrations exceed World Health Organization (WHO) drinking-water standards in all
samples, and in two regions, arsenic concentrations also significantly exceed WHO standards. The elevated levels of As indicate
that arsenic contamination of water supplies in Bangladesh is not confined to groundwater.
Received: 4 June 1999 · Accepted: 17 August 1999 相似文献