全文获取类型
收费全文 | 5258篇 |
免费 | 1106篇 |
国内免费 | 1542篇 |
专业分类
测绘学 | 412篇 |
大气科学 | 894篇 |
地球物理 | 1306篇 |
地质学 | 2744篇 |
海洋学 | 1054篇 |
天文学 | 252篇 |
综合类 | 674篇 |
自然地理 | 570篇 |
出版年
2024年 | 41篇 |
2023年 | 85篇 |
2022年 | 298篇 |
2021年 | 325篇 |
2020年 | 291篇 |
2019年 | 336篇 |
2018年 | 406篇 |
2017年 | 351篇 |
2016年 | 354篇 |
2015年 | 291篇 |
2014年 | 327篇 |
2013年 | 334篇 |
2012年 | 433篇 |
2011年 | 384篇 |
2010年 | 355篇 |
2009年 | 323篇 |
2008年 | 248篇 |
2007年 | 286篇 |
2006年 | 227篇 |
2005年 | 204篇 |
2004年 | 147篇 |
2003年 | 148篇 |
2002年 | 120篇 |
2001年 | 120篇 |
2000年 | 170篇 |
1999年 | 221篇 |
1998年 | 156篇 |
1997年 | 174篇 |
1996年 | 129篇 |
1995年 | 112篇 |
1994年 | 105篇 |
1993年 | 100篇 |
1992年 | 73篇 |
1991年 | 52篇 |
1990年 | 47篇 |
1989年 | 31篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
1954年 | 4篇 |
排序方式: 共有7906条查询结果,搜索用时 109 毫秒
961.
1999年夏季江淮地区热源和水汽汇时空变化特征 总被引:4,自引:1,他引:3
利用1999年的NCAR再分析网格点风场、温度场、湿度场及含HUBEX试验加密观测的降水资料等,诊断分析了夏季长江流域梅雨暴雨集中期及其前后江淮地区的大气热源、水汽汇的时空分布及多时间尺度特征. 相似文献
962.
我国短期气候动力预测模式系统的研究及试验 总被引:38,自引:5,他引:33
气候和气候异常对我国的国民经济发展具有重大影响,为提高短期气候预测的准确率,研究动力气候模式短期气候预测新技术至关重要.通过近5年的努力,建立了一套出月动力延伸预报模式,海气耦合的全球气候模式(AGCM+OGCM+海冰+高分辨率印度洋-太平洋海盆模式),区域气候模式季和年际尺度的业务动力模式组成的系统.初步把我国的短期气候预测水平由经验统计方法提高到定量和客观分析的水平上.在此基础上,已建成了一个具有物理基础的统计方法与气候动力模式相结合的综合气候预报系统. 相似文献
963.
964.
965.
China Ocean Engineering - Based on the elastic foundation beam theory and the multi-floating-module hydrodynamic theory, a novel method is proposed to estimate the dynamic responses of VLFS (Very... 相似文献
966.
967.
Zhifan Mu Tianxiao Li Dong Liu Qiang Fu Renjie Hou Qinglin Li Yi Ji Song Cui Mo Li 《水文研究》2021,35(4):e14155
To enhance the utilization efficiency of farmland irrigation water and reduce the leakage of water conveyance channels, the leakage process of channels was simulated dynamically. The simulated results were compared with data measured in laboratory experiments, and the performance of the model was evaluated. The results indicated that the simulated values of the model were consistent with the observation values, and the R2 values varied between 0.91 and 0.99. In addition, based on the laboratory experiments, a water supply system (Mariotte bottles) and soil box were built using plexiglass. Three influencing factors, namely, the channel form, soil texture and channel cross-sectional area, were varied to observe and calculate the resulting cumulative infiltration amount, infiltration rate and wetting front migration distance. HYDRUS-3D software was used to solve the three-dimensional soil water movement equation under different initial conditions. The results demonstrated that the U-shaped channel was more effective than the trapezoidal channel in increasing the utilization efficiency of the water resources. A U-shaped channel with a small channel cross-sectional area should be adopted and the soil particle size should be prioritized in the construction of water conveyance channels for farmlands. The simulation results were in agreement with the observed results, which indicates that HYDRUS-3D is a reliable tool that can accurately simulate the soil moisture movement in water conveyance channels. The research results can provide a reference for the design and operation of farmland irrigation systems. 相似文献
968.
Journal of Oceanology and Limnology - Jellyfish blooms occur worldwide and have resulted in serious problems in tourism, fisheries, coastal industries, and the marine ecosystem. The life cycle of... 相似文献
969.
Residential segregation is a dual process of socio-spatial differentiation in residents and spatio-temporal heterogeneity in dwelling.However,most of the existing studies are es-tablished from the single perspective of urban residents based on demographic data,which is difficult to reveal the dynamics and complex spatial reconstruction within and between cities.With the characteristics of both stability and timeliness,the rapidly changing housing market is one of the processes and results of socio-spatial reconfiguration,and it is undoubtedly a better lens to observe residential segregation.This paper adopts methods such as multi-group segregation index,multi-scalar segregation profiles,and decomposition of segregation index,with Nanjing and Hangzhou as case cities,and establishes multi-scalar segregation profiles and comparative models based on three geographical scales of census tract,block and grid,and different residential types.A quantitative study was conducted on the degree and pattern of multi-scalar residential segregation in Nanjing and Hangzhou from 2009 to 2018.The pa-per found that the spatial segregation index is an improvement of the non-spatial segregation index.There are differences between Nanjing and Hangzhou in the evolution process of residential segregation.Nanjing has a higher degree of spatial differentiation as a whole,among which spatial components have a more significant impact. 相似文献
970.
ZHANG Xuhui LI Huan GONG Zheng ZHOU Zeng DAI Weiqi WANG Lizhu Samuel DARAMOLA 《地理学报(英文版)》2021,31(12):1852-1872
It is common to obtain the topography of tidal flats by the Unmanned Aerial Vehicle(UAV) photogrammetry,but this method is not applicable in tidal creeks.The residual water will lead to inaccurate depth inversion results,and the topography of tidal creeks mainly de-pends on manual survey.The present study took the tidal creek of Chuandong port in Jiangsu Province,China,as the research area and used UAV oblique photogrammetry to reconstruct the topography of the exposed part above the water after the ebb tide.It also proposed a Trend Prediction Fitting (TPF) method for the topography of the unexposed part below the water to obtain a complete 3D topography.The topography above the water measured by UAV has the vertical precision of 12 cm.When the TPF method is used,the cross-section should be perpendicular the central axis of the tidal creek.A polynomial function can be adapted to most shape of sections,while a Fourier function obtains better results in asym-metrical sections.Compared with the two-order function,the three-order function lends itself to more complex sections.Generally,the TPF method is more suitable for small,straight tidal creeks with clear texture and no vegetation cover. 相似文献