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991.
针对中国高速公路交通气象灾害风险预警业务需求,以基于影响的预报预警服务技术为指导,综合考虑高速公路致灾因子危险性、孕灾环境暴露度、承灾体脆弱性和防灾减灾能力因子,构建交通气象灾害风险预警模型。在此基础上,采用C/S体系架构,综合运用多源数据接入与可视化、基于GIS技术的产品自动加工制作方法等技术,研发高速公路交通气象灾害风险预警业务系统。系统具备气象实况监测告警、灾害预警分析、产品自动加工制作、人机交互订正、服务产品交互制作、数据接入与综合显示、地图管理与操作等功能。系统在交通气象服务业务使用过程中,突显出较好的业务应用能力与发展前景。 相似文献
992.
毛细管离子电泳分离间接紫外光度法测定镍矿石镍钴铜 总被引:1,自引:0,他引:1
研究了以咪唑为背景吸收电解质,α-羟基异丁酸为络合剂,毛细管离子电泳分离,间接紫外光度法测定镍矿石中Ni,Co,Cu含量。考察了背景电解质的pH值,α-羟基异丁酸和咪唑浓度对Fe^3+,Co^2+,Ni^2+,Zn^2+,Cu^2+分离的影响,在优化的条件下,几种离子在8min内完成分离,检测限低至0.2mg/L,以Zn作内标,改善了方法的精密度,对于20mg/L各离子峰面积的相对标准偏差〈6.5 相似文献
993.
In this paper, a new particle tracking technique is described which can simulate non-Fickian diffusion within porous media. The technique employs fractional Brownian motions (fBms), a generalization of regular Brownian motion. These random fractal functions allow both super- and subdiffusive particle paths to be produced and hence non-Fickian diffusion of the resulting panicle clouds can be modeled. In recent years, fBm trace functions have been used by many authors to reproduce self-affine random fields to simulate various porous media properties. In contrast, a method is detailed herein which uses self-similar spatial fBm trajectories to simulate directly non-Fickian behavior of the particle clouds. Although fractal trajectories have been previously suggested as the basis for possible methods of modeling non-Fickian diffusion, the authors believe that this paper contains the first algorithm to be presented which does not require an a priori knowledge of the end condition of the random walk and, more importantly, allows both a definable scaling exponent and (fractal) diffusion coefficient to be specified. The resulting non-Fickian diffusion using the new algorithm is illustrated and some applications are discussed. The purpose of this paper is to bring the potential usefulness of fBm trajectories in simulating non-Fickian processes within homogeneous media to the attention of numerical modelers active in the simulation of subsurface diffusive processes. The method has a particular environmental application in the simulation of the non-Fickian dispersion of groundwater contaminants through porous media. 相似文献
994.
应重视和加强我国沙漠绿洲的研究 总被引:2,自引:1,他引:2
把散布在我国干旱荒漠地带内的沙漠绿洲,统一组合成一种独特而完整的生成地域单元开展研究,应予重视和加强。沙漠绿洲是干旱荒漠地带内精华地域,也是今后该地带开发建设和经济发展基地,还是改造利用沙漠的潜力与希望所在。随着我国经济发展战略重点向西北转移,开发建设和整治利用沙漠绿洲,有着特别的重要性和紧迫性。 相似文献
995.
996.
利用常规气象观测资料、NCEP FNL分析资料(水平分辨率为1°×1°,时间分辨率为6 h),对2013年7月21-22日和2014年7月8-9日两次陕北暴雨过程成因进行热力动力诊断,结果表明:两次陕北暴雨与高低空急流关系密切,暴雨带位于低空急流左侧的水汽辐合区,“0721”过程低空急流更强,在高低空急流耦合的强上升运动区(延安)出现大暴雨。降水前期,两次过程大气均存在对流不稳定,切变线触发对流,产生强降水,而其释放的凝结潜热加热形成中低层大气的热力不连续面,湿斜压性及锋生增强,造成整层饱和大气的抬升,维持强降水。“0721”过程前期对流降水的潜热释放更大,由此反馈的低空急流及锋生更强,出现大暴雨天气。广义对流涡度矢量垂直分量很好地描述了两次暴雨过程高低空急流耦合作用以及凝结潜热释放增强的锋生作用,其变化趋势能够反映降水的发展和减弱过程。暴雨出现在湿热力平流参数垂直积分大值中心及南侧的高梯度区,大值中心出现后约6 h会产生强降水,这对于强降水落区的预报有一定指示意义。 相似文献
997.
998.
Classification is an important process in interpretation of synthetic aperture radar(SAR) imagery. As an advanced instrument for remote sensing, the polarimetric SAR has been applied widely in many fields. The main aim of this paper is to explore the ability of the full-polarization SAR data in classification. The study area is a part of Dunhuang, Gansu Province, China. An L-band full-polarization image of Dunhuang which includes quad-polarization modes was acquired by the ALOS-PALSAR(Advanced Land Observing Satellite–the Phased Array type L-band Synthetic Aperture Radar). Firstly, new characteristic information was extracted by the difference operation, ratio operation, and principal component transform based on the full-polarization(HH, HV or VH, VV) modes SAR data. Then the single-, dual-, full-polarization SAR data and new SAR characteristic information were used to analyze quantitatively the classification accuracy based on the Support Vector Machines(SVM). The results show that classification overall accuracy of single-polarization SAR data is poor, and the highest is 56.53% of VV polarization. The classification overall accuracy of dual-polarization SAR is much better than single-polarization, the highest is 74.77% of HV VV polarization data. The classification overall accuracy of full-polarization SAR is 80.21%, adding the difference characteristic information, ratio characteristic information and the first principal component(PC1) respectively, the overall accuracy increased by 3.09%, 3.38%, 4.14% respectively. When the full-polarization SAR data in combination with the all characteristic information, the classification overall accuracy reached to 91.01%. The full-polarization SAR data in combination with the band math characteristic information or the PC1 can greatly improve classification accuracy. 相似文献
999.
Sand hazards are serious at the Danghe Reservoir of Dunhuang,and efforts to control sand are ineffective because disaster-causing mechanisms are currently unclear.The source of sandy materials,dynamic environment of blown sand,and controlling measures of the reservoir area are investigated using different methods,such as granularity analyses,wind regime and sand transport field observation and analyses,sand drift potential calculation.Accordingly,the sandy materials are found to derive chiefly from the Mingsha Mountain on the north side of the reservoir area.In addition,sand grain in the range of 0.50-0.25 mm and 0.25-0.10 mm are dominant.The prevailing sand-moving wind originates from the N direction,accounting for 15.38% of the yearly total,which coincides in the same direction with sand source,thereby increasing the severity of sand hazards in the reservoir area.The yearly sand DP is 1386.59 VU,the yearly RDP is 567.31 VU,the yearly RDP/DP is 0.41,and the yearly RDD is 183.15°.In the windy season(mainly in summer),sand materials are blown by wind from north to south,and then blocked by the Danghe River.The sand materials then move with an approximate east-west trend into the river channel and produce sediment,thereby causing adisaster.We propose that the sand-controlling pattern of the Danghe Reservoir is dominated by sand blocking in the outer fringe and sand fixing in the inner fringe.Applying windbreak and sand fixation to control sandy material movement into the river channel plays an important role in retarding sedimentation and extending the useful life of the Danghe Reservoir. 相似文献
1000.
研究宅基地转入方的需求意愿及影响因素可为构建科学合理的宅基地流转制度提供参考。从需求的角度出发,构建城市居民宅基地转入意愿影响因素分析模型,以长沙市为例,运用Logistic回归模型分析了城市居民宅基地转入意愿的影响因素。结果表明:影响城市居民宅基地转入意愿的因素主要有宅基地形状、城市居民年龄、城市居民家庭住房使用年限、宅基地产权、宅基地与中心城区的距离和宅基地基础设施状况。宅基地流转应以城中村和城郊村为试点范围,加快宅基地确权颁证,完善宅基地基础设施。 相似文献