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611.
612.
长江口海平面上升预测及其对滨海湿地影响 总被引:1,自引:0,他引:1
选择吴淞站和吕四站2个验潮站数据,通过统计学方法进行长江口海平面上升预测,从而构建了一套长江口地区较完备的海平面上升情景库:以2013年为基准年份,其最佳预测值的范围在2030年、2050年、2100年分别为50~217 mm,118~430 mm,256~1215 mm。以此情景库为基础,探究海平面上升变化对长江口滨海湿地的影响,结果表明:随着海平面上升值的增加,长江口滨海湿地的面积不断减少;在基于验潮站数据作趋势外推得到的情景下,湿地面积减少较平缓,而在考虑全球变暖背景的情景下,湿地面积减少迅速;且不论在何种情景下,时间尺度越大,湿地减少的面积越大。 相似文献
613.
城市居民认知距离透视认知变形 ——-以北京市为例 总被引:1,自引:0,他引:1
对距离的认知是人类建立认知空间框架的重要基础。本文在相关研究的基础上, 对认知距离的特点进行了分析, 提出从数量认知距离与实际认知距离两种分析角度来分析这一概念。通过分别利用定义一元线性回归, 与 采用多维标度法(MDS)及二维回归(BR), 对认知距离的标量变形和向量变形进行定量分析。在此基础上, 以北京市 为例, 对北京市居民进行抽样调查。通过认知心理学实验的方式, 令被试估计城市主要地标两两之间的距离。对实 验结果分别将上述方法应用于计算北京市居民在标量变形和向量变形的定量化表示, 并进一步通过方差分析 (ANOVA)讨论了影响北京市居民对城市距离认知变形的因素, 包括年龄、居住地区等。 相似文献
614.
Schratzberger M Daniel F Wall CM Kilbride R Macnaughton SJ Boyd SE Rees HL Lee K Swannell RP 《Marine pollution bulletin》2003,46(4):430-443
Numerous studies have demonstrated the efficacy of bioremediation for enhancing oil removal but the ecological effect on shoreline biota is unclear. Therefore, a field experiment was designed at an intertidal sandflat in SW England to assess the effects of nutrient addition to oiled sediments on meio- and macrofauna for a period of up to 45 weeks. Natural assemblages were exposed to different types of experimental treatments (no oil, oil alone, oil treated with slow-release fertiliser or liquid fertiliser). Bioremediation stimulated the microbial population and increased oil biodegradation. This, however, did not result in faster recolonisation rates of fertilised versus non-fertilised oiled sediments. Mild effects of oil and bioremediation treatments on benthic fauna were observed, including short-term shifts in dominance patterns. Decreased abundance of dominant species in the oiled compared to unoiled sediments resulted in significantly higher evenness of benthic assemblages within the first 11 weeks of the experiment. 相似文献
615.
Environmental effects of water resource development and use in the Tarim River basin of northwestern China 总被引:9,自引:0,他引:9
Feng?QiEmail author Liu?Wei Si?Jianhua Su?Yonghong Zhang?Yewu Cang?Zongqiang Xi?Haiyang 《Environmental Geology》2005,48(2):202-210
The unbridled development and use of water resources in the Tarim River basin over the last 50 years have led to a serious degradation of soil (>12×103 km2 of land desertified between the 1960s and 1990s) and water quality (rise in maximum salinity was from 1.3 g l–1 in 1960, to 4.0 g l–1 in 1981–1984, and to 7.8 g l–1 in 1998). Approximately 300 km of the lower reaches of the river course dried up between the 1950s and 1970s, seriously altering the downstream hydrological processes (a 4–6 m drop in groundwater levels from the 1960s to the 1980s, and 0.2 m yr–1 thereafter) and ecosystems (67% and 50% decrease (1958–1978) in Populus euphratica forest acreage and biomass, respectively). Between the 1950s and 1990s, 3820 km2 of P. euphratica forest and 200 km2 of shrub- and grassland were lost in the lower reaches of the Tarim River. In this study, based on estimates of soil organic carbon in desertified lands, it has been found that in the last 30 years (1970–2000), approximately 112 Tg of organic carbon (28% originating in the 0–1.0 m soil profile) has been released into the atmosphere as a result of soil degradation in the Tarim River basin. Intensive anthropogenic disturbance has been one of the foremost factors leading to the deterioration of water resources in this region. The key to solving these problems is to enhance the scientific and technical level of monitoring, management, and restoration of water resources and associated water and soil components of local ecosystems. 相似文献
616.
自从1984年《地理研究》开辟地理学学位论文摘要这个栏目到现在已经有五年历史了,尽管这个栏目很小,仅占学术刊物的一角之地;所刊登的学位论文,据不完全统计,也只占全部地理学学位论文的三分之一左右,但它已经起到了它所应起的作用,扩大了地理科学这一部分宝贵财富的社会效益,为地理界提供了一个“相互了解和学位的园地”1),作为文献,它也是青年地理学家的第一个记录,并且使我们从中看出,新一代的地理学家正在继往开来,茁壮成长,予示着未来地理学的光辉前程,这是值得我们广大地理工作者高兴的。 相似文献
617.
The present paper models the behaviour of bimodular materials (materials with different tensile and compressive moduli) by using a three-dimensional finite element method. Since there is no explicit and definite expression for the shear modulus G of bimodular materials, the analysis starts with a 3 × 3 elasticity matrix in the principal stress coordinate system, and then uses a transformation from principal to Cartesian coordinates to obtain the 6 × 6 elasticity matrix. A corresponding iterative technique is proposed, and multiloading sequences in non-proportionate loading—which need more iterations because of the non-linear elastic property—are also discussed. Numerical examples are presented which show good agreement with analytical results. 相似文献
618.
Growing season evapotranspiration from Tamarix ramosissima stands under extreme arid conditions in northwest China 总被引:1,自引:0,他引:1
Given the increasing threat of water shortages in the extremely arid regions (rainfall<50 mm year−1) of northwestern China, growing season evapotranspiration (ET) associated with native species such as Tamarix ramosissima is of particular interest. Consequently, this study sought to evaluate the accuracy of daily ET estimates using Bowen ratio
data, as well as measuring seasonal ET and development of an energy balance for a stand of T. ramosissima. Bowen ratio apparatus measurements of ET were carried out on a stand of T. ramosissima in a 2.04 km2 field, which are all covered with T. ramosissima near Erdaoqiao, Ejina Province, Inner Mongolia Autonomous Region, China. Soil moisture content and green area index were
also monitored. Daily ET could be accurately estimated from Bowen ratio data on a continuous basis over the 153-day growing
season. The mean daily T. ramosissima ET over this period was 1.62 mm day−1, for a seasonal total of 248.20 mm. In this extremely arid locale, the great majority of available energy dissipated over
the growing season was a result of sensible rather than latent heat fluxes. While the heat storage term was the main source
of energy at night and a considerable sink of energy during the daytime, the magnitude of the daily mean soil heat flux was
small. Such a determination of temporal and ecosystem-specific ET patterns allows an improved prediction of ET in the desert
riparian zone. 相似文献
619.
R. Szczerba S.K. GÓrny G. StasiŃska N. SiÓdmiak R. Tylenda 《Astrophysics and Space Science》2001,275(1-2):113-119
We present Infrared Space Observatory (ISO)Short Wavelength Spectrometer (SWS) observations for 16Wolf–Rayet ([WR]) planetary nebulae (PNe) in the range from 2.4 to16.5 m with the aim of analyzing the dust features present inthis group of objects. We have found that Policyclic AromaticHydrocarbon (PAH) molecular bands are present in most of the observed[WR] planetary nebulae with clear exception for K 2–16 among latetype [WC] stars. 相似文献
620.