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851.
基于BP模型和Ward法的北京市平谷区乡村地域功能评价与分区 总被引:10,自引:3,他引:10
构建乡村地域功能评价指标体系,借助BP神经网络模型揭示平谷区“生产-生活-生态”功能分异特征;运用Ward法划分功能区,服务于平谷区乡村转型发展和功能区布局。结果表明:① 在多项功能综合作用下,平谷区基本形成了“平原地区生产功能较强、镇中心及周边村域生活功能明显、山地区以生态功能为主”的功能分布格局。② 基于评价结果和空间属性,平谷区划分为西部平原生产区、东部山地生态生产区、中部平原城市生活区、中部近郊平原生活区、东部丘陵生态生活区和北部山地生态区。其中,西部平原生产区、中部平原城市生活区、北部山地生态区是平谷三生空间功能发展的优势区域,分布相对集中。按照“强功能重优化、中等功能重提升、弱功能重改善”的原则提升乡村地域功能,促进地区均衡发展。 相似文献
852.
853.
Guocheng Pan 《Natural Resources Research》1997,6(4):285-293
A fundamental task for petroleum exploration decision-making is to evaluate the uncertainty of well outcomes. The recent development
of geostatistical simulation techniques provides an effective means to the generation of a full uncertainty model for any
random variable. Sequential indicator simulation has been used as a tool to generate alternate, equal-probable stochastic
models, from which various representations of uncertainties can be created. These results can be used as input for the quantification
of various risks associated with a wildcat drilling program or the estimation of petroleum resources. A simple case study
is given to demonstrate the use of sequential indicator simulation. The data involves a set of wildcat wells in a gas play.
The multiple simulated stochastic models are then post-processed to characterize various uncertainties associated with drilling
outcomes. 相似文献
854.
Growth and physiological responses of wheat to sand burial were studied in Horqin Sandy Land, to determine the impact on productivity and survival as well as antioxidant enzymes responses. This study c... 相似文献
855.
Pan Ming Huang Shan-Li Wang Yu-Min Tzou Yibin Huang Boqi Weng Shunyao Zhuang Ming Kuang Wang 《Environmental Earth Sciences》2013,68(8):2199-2209
Soil is a vital biological habitat, which is of primary importance in determining and regulating biological activity and biodiversity. Therefore, it is Earth’s most important resource in sustaining both belowground and aboveground biological activities. Biodiversity versus landscape diversity and land use practices in multifunctional landscapes have been addressed. Humans have so manipulated nature that few locations in the world remain without human influence, causing unforeseen changes in ecosystem continuously and biodiversity. Among the environmental compartments, about 90 % of environmental pollutants are bound with soil particles. The soil-bound pollutants may be released to the soil solution through physical, chemical and biological interfacial interactions and pose a threat to biodiversity and ecosystem integrity. These interfacial interactions are especially important in the rhizosphere, where the kinds and concentrations of biomolecules are different from the bulk soil because of intense biological activity. These biomolecules affect biogeochemical processes, soil microbial ecology, nutrient and contaminant dynamics, abiotic and biotic factors, and soil biodiversity through allelopathic interactions. Soil interfacial interactions under different pedogenic processes and anthropogenic activity in relation to belowground biodiversity and the impact on aboveground biodiversity, productivity and integrity should be an important and exciting area of science for years to come. 相似文献
856.
2007年7月16日日本新溻地震对柏崎刈羽核电站的影响 总被引:1,自引:0,他引:1
2007年7月16日日本新溻县柏崎市附近海域发生Mw6.6地震(日本气象局震级MJMA6.8)。该地震引发世界最大核电厂——柏崎刈羽核电站多起核安全事件,是世界范围内有记载的对核电站影响最为严重的一次地震。本文根据收集到的资料,详细介绍了该地震对柏崎刈羽核电站造成的影响,文章最后概述了日本、国际原子能机构对该地震的反思以及我们应该从中吸取的经验教训。 相似文献
857.
The research of coupling WRF (Weather Research and Forecasting Model) with a land surface model is enhanced to explore the
interaction of the atmosphere and land surface; however, regional applicability of WRF model is questioned. In order to do the
validation of WRF model on simulating forcing data for the Heihe River Basin, daily meteorological observation data from 15 stations
of CMA (China Meteorological Administration) and hourly meteorological observation data from seven sites of WATER
(Watershed Airborne Telemetry Experimental Research) are used to compare with WRF simulations, with a time range of a whole
year for 2008. Results show that the average MBE (Mean Bias Error) of daily 2-m surface temperature, surface pressure, 2-m relative
humidity and 10-m wind speed were ?0.19 °C, ?4.49 hPa, 4.08% and 0.92 m/s, the average RMSE (Root Mean Square Error)
of them were 2.11 °C, 5.37 hPa, 9.55% and 1.73 m/s, and the average R (correlation coefficient) of them were 0.99, 0.98, 0.80 and
0.55, respectively. The average MBE of hourly 2-m surface temperature, surface pressure, 2-m relative humidity, 10-m wind speed,
downward shortwave radiation and downward longwave were ?0.16 °C, ?6.62 hPa, ?5.14%, 0.26 m/s, 33.0 W/m2 and ?6.44
W/m2, the average RMSE of them were 2.62 °C, 17.10 hPa, 20.71%, 2.46 m/s, 152.9 W/m2 and 53.5 W/m2, and the average R of
them were 0.96, 0.97, 0.70, 0.26, 0.91 and 0.60, respectively. Thus, the following conclusions were obtained: (1) regardless of
daily or hourly validation, WRF model simulations of 2-m surface temperature, surface pressure and relative humidity are more
reliable, especially for 2-m surface air temperature and surface pressure, the values of MBE were small and R were more than 0.96;
(2) the WRF simulating downward shortwave radiation was relatively good, the average R between WRF simulation and hourly
observation data was above 0.9, and the average R of downward longwave radiation was 0.6; (3) both wind speed and rainfall
simulated from WRF model did not agree well with observation data. 相似文献
858.
利用LI-6400XT便携式光合仪和大型称重式蒸渗仪研究红砂(Reaumuria soongorica)、珍珠(Salsola passerina)灌丛在干旱和湿润条件下的蒸腾耗水特征,并探讨从叶片到灌丛尺度转换中,在非破损状态下植物叶面积的可靠测定方法。结果表明:用图像法获得非破损状态下植物叶面积是可行的,基于植物叶面积通过尺度转换得到灌丛尺度的蒸腾量与蒸渗仪测定的蒸腾量具有较高一致性(r=0.9752,P<0.01)。干旱条件下,红砂蒸腾速率的日变化呈单峰曲线,主要影响因素为气孔导度(P<0.01);湿润条件下,红砂和珍珠蒸腾速率的日变化均呈单峰曲线,主要的影响因素为气孔导度、空气相对湿度、饱和蒸汽压亏缺和光合有效辐射(P<0.01)。珍珠水分利用效率和气孔限制值均高于红砂。此外,干旱条件下红砂的水分利用效率和气孔限制均高于湿润条件。通过尺度转换得到的灌丛尺度的蒸腾量和蒸渗仪测定的蒸腾量的结果均表明,红砂的蒸腾量始终大于珍珠,且随土壤湿润状况的改善而增大。红砂灌丛蒸腾量与蒸散量之比在干旱条件下(T/ET=21%)较湿润条件下高(约2%)。同时,红砂灌丛T/ET高于珍珠灌丛。因此,基于图像法获得的叶面积参数可用于从叶片(便携式光合仪法)到植株及灌丛水平(称重式蒸渗仪法)的植物蒸腾耗水尺度转换研究。 相似文献
859.
Journal of Oceanology and Limnology - Magnetotactic bacteria(MTB) display magnetotaxis ability because of biomineralization of intracellular nanometer-sized, membrane-bound organelles termed... 相似文献
860.