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71.
Yu Zhi Shi Xiuzhi Zhou Jian Gou Yonggang Rao Dijun Huo Xiaofeng 《Natural Resources Research》2021,30(6):4063-4078
Natural Resources Research - In the process of open-pit bench blasting for many mines, rock fragments move in the direction of loose space after fragmentation under explosive energy, leading to ore... 相似文献
72.
人地系统耦合下生态系统服务与人类福祉关系研究进展与展望 总被引:3,自引:1,他引:2
21世纪以来生态系统服务退化与人类需求提升间的矛盾愈发激烈,如何有效推进生态系统服务与人类福祉的协调平衡成为当前可持续发展的核心主题。论文通过梳理生态系统服务与人类福祉关系研究的阶段演进发现,现有研究主要从服务对福祉的影响与福祉对服务的反馈切入,逐步聚焦到供需关系与空间流动、权衡/协同的利益博弈、文化服务的价值化、生态补偿与付费、优化调控与可持续管理等二者相互作用关系的实践上。但目前的关系研究仍以“级联框架的‘影响链条’”为主导,缺少测度直接交互作用的技术路径,理论体系匮乏,面向可持续管理的应用支撑较弱,而同时二者逐渐形成非线性交互关系,亟需在人地系统耦合框架下寻求综合集成范式经验以推进理论创新。因此,论文提出从级联到耦合的关系研究新思路,以生态系统服务与人类福祉的耦合研究来系统辨析其交互胁迫效应及内在动力演化机理,同时探索性构建耦合研究的理论框架与技术思路,丰富人地系统耦合的关键命题。以此为基础,未来研究还需着重从交互作用关系的梳理出发,深化耦合效应解耦、传导机制与动态集成、基于服务与福祉协调的可持续优化等领域研究,促进有序协调的生态文明发展。 相似文献
73.
Journal of Oceanology and Limnology - The increases of atmospheric carbon dioxide and other greenhouse gases have caused fundamental changes to the physical and biogeochemical properties of the... 相似文献
74.
75.
A new prediction model for grain yield in Northeast China based on spring North Atlantic Oscillation and late-winter Bering Sea ice cover 下载免费PDF全文
Accurate estimations of grain output in the agriculturally important region of Northeast China are of great strategic significance for guaranteeing food security. New prediction models for maize and rice yields are built in this paper based on the spring North Atlantic Oscillation index and the Bering Sea ice cover index. The year-to-year increment is first forecasted and then the original yield value is obtained by adding the historical yield of the previous year. The multivariate linear prediction model of maize shows good predictive ability, with a low normalized root-mean-square error (NRMSE) of 13.9%, and the simulated yield accounts for 81% of the total variance of the observation. To improve the performance of the multivariate linear model, a combined forecasting model of rice is built by considering the weight of the predictors. The NRMSE of the model is 12.9% and the predicted rice yield explains 71% of the total variance. The corresponding cross-validation test and independent samples test further demonstrate the efficiency of the models. It is inferred that the statistical models established here by applying year-to-year increment approach could make rational prediction for the maize and rice yield in Northeast China before harvest. The present study may shed new light on yield prediction in advance by use of antecedent large-scale climate signals adequately. 相似文献
76.
GPS Solutions - We evaluate the performance of Galileo broadcast NeQuick model by comparing it with GPS broadcast Klobuchar and the original NeQuick2 models. The broadcast coefficients of Galileo... 相似文献
77.
构建早稻雨洗花灾害指标及适于早稻产量估算的灾损评估模型,对开展早稻雨洗花灾害监测、损失评估、灾害保险等具有重要意义。该文以江西省早稻为研究对象,利用1981-2015年14个水稻气象观测站逐日气象资料和农业气象观测资料,筛选出基于早稻抽穗扬花期间过程降水量、最大降水量、降水日数及实际产量的雨洗花灾害样本78个,在此基础上,利用相关分析、正态分布以及主成分回归法,建立了雨洗花灾害指标和灾损评估模型,并对其进行验证。结果表明:抽穗扬花期降水对雨洗花灾害形成有显著影响,其主要影响时段为抽穗扬花普遍期前后5 d内,关键时段为抽穗扬花普遍期前后3 d内。日降水量40 mm可作为早稻抽穗扬花期雨洗花灾害临界指标。以该指标为基础,统计日降水量不低于40 mm的降水日数及其对应的累积降水量,当累积降水量为40~170 mm时,为轻度雨洗花灾害,早稻一般减产小于15%,平均减产10%;当累积降水量不小于170 mm时,为重度雨洗花灾害,早稻一般减产不低于15%,平均减产22%。指标验证结果与历史实际灾害发生情况有较好的一致性。雨洗花灾损评估模型检验结果表明:雨洗花年模拟产量与实际产量吻合度较高,平均相对模拟误差为4.3%,78.0%的资料相对误差在5%以内,可利用该模型对雨洗花年的早稻减产率进行模拟和预测。 相似文献
78.
以湖南省油菜为研究对象,综合洪涝与连阴雨的致灾因子,利用历史灾情数据反演涝渍过程样本,构建临灾、受灾状态样本,采用均值t检验方法,定量分析不同降水累积衰减系数w情况下,降水因子差异的显著性,构建有效累积降水量PE。基于Fisher判别准则,计算涝渍灾害临灾与受灾的临界线,构建逐日动态的油菜春季涝渍过程灾变判别指标y,并进行涝渍过程样本反演及独立样本验证。分析春季涝渍受灾频率与相对气象产量的关系,构建灾害影响评价模型。结果表明:当w=0.899时,受灾与临灾样本PE的差异最显著。灾变判别指标y可逐日动态监测涝渍灾变过程及灾害后续影响,为动态监测区域油菜涝渍过程提供了数据支撑;指标指示的灾变范围与实际受灾情况基本一致,为区域防灾减灾提供了科学参考。开花期及结荚期湖南油菜涝渍受灾频率较高,成熟期较低。湖南省油菜春季涝渍灾害影响指数呈东南高西北低,长沙东部、株洲中部及北部、湘潭、永州及郴州中部油菜产量受涝渍灾害影响最重。 相似文献
79.
80.
Observed particle sizes and fluxes of Aeolian sediment in the near surface layer during sand-dust storms in the Taklamakan Desert 总被引:1,自引:0,他引:1
Wen?Huo Qing?He Fan?Yang Xinghua?Yang Qing?Yang Fuyin?Zhang Ali?Mamtimin Xinchun?Liu Mingzhong?Wang Yong?Zhao Xiefei?ZhiEmail author 《Theoretical and Applied Climatology》2017,130(3-4):735-746
Monitoring, modeling and predicting the formation and movement of dust storms across the global deserts has drawn great attention in recent decades. Nevertheless, the scarcity of real-time observations of the wind-driven emission, transport and deposition of dusts has severely impeded progress in this area. In this study, we report an observational analysis of sand-dust storm samples collected at seven vertical levels from an 80-m-high flux tower located in the hinterland of the great Taklamakan Desert for ten sand-dust storm events that occurred during 2008–2010. We analyzed the vertical distribution of sandstorm particle grain sizes and horizontal sand-dust sediment fluxes from the near surface up to 80 m high in this extremely harsh but highly representative environment. The results showed that the average sandstorm grain size was in the range of 70 to 85 μm. With the natural presence of sand dunes and valleys, the horizontal dust flux appeared to increase with height within the lower surface layer, but was almost invariant above 32 m. The average flux values varied within the range of 8 to 14 kg m?2 and the vertical distribution was dominated by the wind speed in the boundary layer. The dominant dust particle size was PM100 and below, which on average accounted for 60–80 % of the samples collected, with 0.9–2.5 % for PM0–2.5, 3.5–7.0 % for PM0–10, 5.0–14.0 % for PM0–20 and 20.0–40.0 % for PM0–50. The observations suggested that on average the sand-dust vertical flux potential is about 0.29 kg m?2 from the top of the 80 m tower to the upper planetary boundary layer and free atmosphere through the transport of particles smaller than PM20. Some of our results differed from previous measurements from other desert surfaces and laboratory wind-dust experiments, and therefore provide valuable observations to support further improvement of modeling of sandstorms across different natural environmental conditions. 相似文献