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971.
972.
宁波夏季强对流和台风短时暴雨雷达回波特征对比分析 总被引:3,自引:1,他引:3
为了对比宁波地区夏季强对流短时暴雨和台风短时暴雨的多普勒雷达回波特征,选取2004年和2005年该地区夏季出现的强对流短时暴雨和台风短时暴雨的个例作为研究对象,从回波的发展演变、回波形态及回波产品值等进行分析比较,发现:这两类短时暴雨在回波强度、回波高度及垂直液态水含量等产品有明显差异,而降水产品如OHP,STP估计的雨量值,在这两种天气过程中,均比实况雨量资料偏小,且实况雨量越大,偏差也越大;另外,在分析中也发现,用雷达缺省的Z-I关系来估计雨量有很大误差,特别是在台风降水过程中;最后分别建立了对流性降水与台风降水的Z-I关系,以修正宁波夏季的降水估计值。 相似文献
973.
974.
Akio Kitoh 《Natural Hazards》2007,42(2):261-272
There is a close relationship between interannual variability of the Indian summer monsoon rainfall and the El Niño/Southern Oscillation (ENSO) (drought conditions over India accompany warm ENSO events and vice versa). However, recent observations suggest a weakening of this ENSO-monsoon relationship that may be linked to global warming. We report here an analysis of the ENSO-monsoon relationship within the framework of a 1000-year control simulation of the MRI-coupled general circulation model (GCM), MRI-CGCM2.2. An overall correlation between the June-July-August (JJA) Nino3.4 sea surface temperature and the JJA Indian monsoon rainfall is –0.39, with reasonable circulation characteristics associated with the modeled ENSO. The simulated ENSO-monsoon relationship reveals long-term variations, from –0.71 to +0.07, in moving 31-year windows. This modulation in the ENSO-monsoon relationship is associated with decadal variability of the climate system. 相似文献
975.
不整合分类研究进展与新型分类方案 总被引:6,自引:0,他引:6
总结了前人对不整合类型的划分工作和不整合形态特点,在此基础之上,根据不整合的成因机制和不整合形态的主控因素,提出了新型不整合分类方案,将不整合分为七个大类,包括削截不整合、褶曲不整合、底辟不整合、震积不整合、古岩溶不整合、超覆不整合和假整合,并进一步细分为13个亚类。新型的不整合分类考虑了震积作用研究等最新的地质学进展,吸收了许多有益成果,扩充了不整合类型,更加关注盆地的自身特点,通过剔除重复类型等方法,使不整合分类方案更加完备,具有较高的科学性和实用性。文中还以国内外有关油田为例分析了不整合类型基本特征。 相似文献
976.
邓肯E-B模型无法描述软化土体的应力应变关系以及土体的剪胀效应;采用抛物线型体应变曲线的南水模型破坏时的剪胀率趋于定值,与实际土体不符。但南水模型适合描述应力应变峰值点前或最大剪胀率前土体的本构关系,邓肯模型适合描述的应变范围更小。因此,若要进行土工结构渐进破坏的分析计算,则需要建立一个适合于描述直至破坏的更大应变范围的土体本构关系。采用损伤扰动概念,将变形过程中的土体视为“相对完整”的未损伤土体和“完全调整”扰动土体的混合体,其应力应变关系可根据损伤扰动程度,由各自的应力应变关系组合确定。并根据试验提出了确定损伤扰动函数的计算公式。对体应变曲线,则采用抛物线加双曲线的形式加以描述。 相似文献
978.
Peter Neeb 《Journal of Atmospheric Chemistry》2000,35(3):295-315
The reaction with the OH radical constitutes the singlemost important removal process for most organiccompounds found in the atmosphere. Efforts to measurethe OH radical rate constants of all troposphericconstituents remain incomplete due to the largevariety of primary emitted compounds and theirtropospheric degradation products.Based on the measured rate constants of 250molecules with the OH radical, a structure-activityrelationship (SAR) for OH reactions has beendeveloped. The molecules used in the dataset includemost classes of tropospheric compounds (includingalkanes, alkenes, and oxygenated hydrocarbons), withthe exception of aromatic and halogen-containingcompounds. Using a new parameterization of themolecular structure, the overall agreement betweenmeasured values and those estimated using the SARdeveloped in this study is usually very good, with10% of the molecules showing deviations larger than50%. In particular, the estimated rate constants ofethers and ketones are in better agreement withexperimental data than with previous SARs (Kwok andAtkinson, Atmos. Environ.
29, 1685–1695,1995). Rate constants of organic nitrates werenot well described by the SAR used in thisstudy. The basic assumption that the additive rateconstant for a chemical group is only influenced byneighbouring functional groups did not allow a goodparameterization for the rate constants of organicnitrates. The use of a second parameter to alter thereactivity of C-H bonds in -position to thefunctional group resulted in markedly better agreementbetween calculated and measured rate constants, butwas not extended due to the limited set of data. This indicates that strong electron withdrawing groups(e.g., nitrate groups) might influence the reactivityof C-H bonds that are not directly adjacent. 相似文献
979.
A Fixed-Path Markov Chain Algorithm for Conditional Simulation of Discrete Spatial Variables 总被引:4,自引:0,他引:4
Weidong Li 《Mathematical Geology》2007,39(2):159-176
The Markov chain random field (MCRF) theory provided the theoretical foundation for a nonlinear Markov chain geostatistics.
In a MCRF, the single Markov chain is also called a “spatial Markov chain” (SMC). This paper introduces an efficient fixed-path SMC algorithm for conditional simulation of discrete spatial variables
(i.e., multinomial classes) on point samples with incorporation of interclass dependencies. The algorithm considers four nearest
known neighbors in orthogonal directions. Transiograms are estimated from samples and are model-fitted to provide parameter
input to the simulation algorithm. Results from a simulation example show that this efficient method can effectively capture
the spatial patterns of the target variable and fairly generate all classes. Because of the incorporation of interclass dependencies
in the simulation algorithm, simulated realizations are relatively imitative of each other in patterns. Large-scale patterns
are well produced in realizations. Spatial uncertainty is visualized as occurrence probability maps, and transition zones
between classes are demonstrated by maximum occurrence probability maps. Transiogram analysis shows that the algorithm can
reproduce the spatial structure of multinomial classes described by transiograms with some ergodic fluctuations. A special
characteristic of the method is that when simulation is conditioned on a number of sample points, simulated transiograms have
the tendency to follow the experimental ones, which implies that conditioning sample data play a crucial role in determining
spatial patterns of multinomial classes. The efficient algorithm may provide a powerful tool for large-scale structure simulation
and spatial uncertainty analysis of discrete spatial variables. 相似文献
980.
新疆物候(候鸟)与气候因子关系分析 总被引:1,自引:0,他引:1
通过对新疆10个站4种候鸟物候及相应气候因子变化的关系分析,得出候鸟停留时间与同期日照时数及≥0℃的积温关系密切,并经过数理统计,得出用气候因子预测候鸟停留时间的数学模式,对预知一定生态环境中鸟类的迁徙具有一定指导意义。 相似文献