全文获取类型
收费全文 | 13672篇 |
免费 | 2874篇 |
国内免费 | 3599篇 |
专业分类
测绘学 | 2793篇 |
大气科学 | 2816篇 |
地球物理 | 3412篇 |
地质学 | 6610篇 |
海洋学 | 1918篇 |
天文学 | 473篇 |
综合类 | 933篇 |
自然地理 | 1190篇 |
出版年
2024年 | 48篇 |
2023年 | 155篇 |
2022年 | 482篇 |
2021年 | 567篇 |
2020年 | 610篇 |
2019年 | 726篇 |
2018年 | 593篇 |
2017年 | 720篇 |
2016年 | 702篇 |
2015年 | 757篇 |
2014年 | 1013篇 |
2013年 | 1078篇 |
2012年 | 1032篇 |
2011年 | 1038篇 |
2010年 | 802篇 |
2009年 | 1018篇 |
2008年 | 1025篇 |
2007年 | 1073篇 |
2006年 | 1014篇 |
2005年 | 835篇 |
2004年 | 784篇 |
2003年 | 599篇 |
2002年 | 596篇 |
2001年 | 438篇 |
2000年 | 413篇 |
1999年 | 355篇 |
1998年 | 318篇 |
1997年 | 272篇 |
1996年 | 219篇 |
1995年 | 174篇 |
1994年 | 181篇 |
1993年 | 118篇 |
1992年 | 94篇 |
1991年 | 68篇 |
1990年 | 54篇 |
1989年 | 25篇 |
1988年 | 38篇 |
1987年 | 26篇 |
1986年 | 15篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 9篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1971年 | 4篇 |
1954年 | 5篇 |
1900年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
81.
82.
崂山花岗岩地区含锶、偏硅酸矿泉水的形成机理 总被引:1,自引:0,他引:1
报道了崂山花岗岩地区矿泉水的特征。指出其矿泉类型为含锶、偏硅酸型,并讨论了其形成机理。 相似文献
83.
使用切向流超滤系统得到粒度较均匀的Fe(OH)3胶体,进而对Fe(OH)3胶体粒子与Cu2 的作用进行了研究,并将实验结果与南沙群岛海区表层水中铜与胶体物质结合状况的调查数据进行了比较分析,得到如下结果:(1)在海水介质中,铜在Fe(OH)3胶体上结合的百分率(pH>5)随pH的升高而下降,随着Fe(OH)3胶体浓度的减小而下降?(2)在天然海水介质中,使铜在Fe(OH)3胶体上结合的百分率在50%-70%的有机物浓度为1.0mg·L-1,有机物浓度的增大使铜与无机胶体结合的百分率有下降的趋势? 相似文献
84.
Xu Shikai Wang Hongchuan Hong Guangwen
Engineer Nanjing Hydraulic Research Institute Nanjing .
Professor Research Institute of Coastal Ocean Engineering Hohai University Nanjing 《中国海洋工程》1996,(4)
To solve problems concerning wave elements and wave propagation, an effective way is the wave energy balance equation, which is widely applied in oceanography and ocean dynamics for its simple computation. The present papaer advances wave energy balance equations considering lateral energy transmission and energy loss as the governing equation for the study of wave refraction-diffraction. For the mathematical model, numerical simulation is made by means of difference method, and the result is verified with two examples. 相似文献
85.
Presented here is a compact explicit difference scheme of high accuracy for solving the extended Boussinesq equations.For time discretization,a three-stage explicit Runge-Kutta method with TVD property is used at predicting stage,a cubic spline function is adopted at correcting stage,which made the time discretization accuracy up to fourth order;For spatial discretization,a three-point explicit compact difference scheme with arbitrary order accuracy is employed.The extended Boussinesq equations derived by Beji and Nadaoka are solved by the proposed scheme.The numerical results agree well with the experimental data.At the same time,the comparisons of the two numerical results between the present scheme and low accuracy difference method are made,which further show the necessity of using high accuracy scheme to solve the extended Boussinesq equations.As a valid sample,the wave propagation on the rectangular step is formulated by the present scheme,the modelled results are in better agreement with the experimental data than those of Kittitanasuan. 相似文献
86.
87.
胶州湾三维变动边界的潮流数值模拟 总被引:35,自引:3,他引:35
基于Blumberg等(1986)的河口、陆架和海洋模式,引入变边界处理技术,建立了胶州湾三维变动边界的潮流模型,模型以σ-正交曲线坐标下三维非线性潮波方程为基本方程,引入2.5阶瑞封闭方程组,采用分裂算子法数值求解方程组,利用湍封闭方程求解垂直紊动粘滞系数,采用干湿网格方法模拟潮流漫滩过程,三维变动边界潮流模型计算结果与实测值吻合良好。 相似文献
88.
依据水面红外发射和红外遥感测温原理,采用HDG-高灵敏度红外测温仪和常规测量仪器相结合的方法,在实验室空气稳定条件下,模拟测得了水面皮层破坏-复原(重建)的热力过程和气-水温差对水面皮层复原过程的影响,获得了大量的测量数据。数据分析表明,当气-水温差从3.0℃变为11.5℃时,水面皮层破坏可导致皮温增量从气-水温差3.0℃时的0.15℃变到11.5℃时的0.45℃,并发现恢复时间与气-水温差呈负线性关系。 相似文献
89.
90.
Michael Riedel 《Marine Geophysical Researches》2007,28(4):355-371
Two single-channel seismic (SCS) data sets collected in 2000 and 2005 were used for a four-dimensional (4D) time-lapse analysis
of an active cold vent (Bullseye Vent). The data set acquired in 2000 serves as a reference in the applied processing sequence.
The 4D processing sequence utilizes time- and phase-matching, gain adjustments and shaping filters to transform the 2005 data
set so that it is most comparable to the conditions under which the 2000 data were acquired. The cold vent is characterized
by seismic blanking, which is a result of the presence of gas hydrate in the subsurface either within coarser-grained turbidite
sands or in fractures, as well as free gas trapped in these fracture systems. The area of blanking was defined using the seismic
attributes instantaneous amplitude and similarity. Several areas were identified where blanking was reduced in 2005 relative
to 2000. But most of the centre of Bullseye Vent and the area around it were seen to be characterized by intensified blanking
in 2005. Tracing these areas of intensified blanking through the three-dimensional (3D) seismic volume defined several apparent
new flow pathways that were not seen in the 2000 data, which are interpreted as newly generated fractures/faults for upward
fluid migration. Intensified blanking is interpreted as a result of new formation of gas hydrate in the subsurface along new
fracture pathways. Areas with reduced blanking may be zones where formerly plugged fractures that had trapped some free gas
may have been opened and free gas was liberated. 相似文献