全文获取类型
收费全文 | 6120篇 |
免费 | 1212篇 |
国内免费 | 1749篇 |
专业分类
测绘学 | 775篇 |
大气科学 | 1002篇 |
地球物理 | 1440篇 |
地质学 | 3442篇 |
海洋学 | 1005篇 |
天文学 | 232篇 |
综合类 | 511篇 |
自然地理 | 674篇 |
出版年
2024年 | 50篇 |
2023年 | 162篇 |
2022年 | 336篇 |
2021年 | 427篇 |
2020年 | 286篇 |
2019年 | 380篇 |
2018年 | 404篇 |
2017年 | 330篇 |
2016年 | 403篇 |
2015年 | 387篇 |
2014年 | 435篇 |
2013年 | 415篇 |
2012年 | 443篇 |
2011年 | 446篇 |
2010年 | 458篇 |
2009年 | 398篇 |
2008年 | 408篇 |
2007年 | 376篇 |
2006年 | 307篇 |
2005年 | 258篇 |
2004年 | 197篇 |
2003年 | 157篇 |
2002年 | 185篇 |
2001年 | 163篇 |
2000年 | 166篇 |
1999年 | 199篇 |
1998年 | 127篇 |
1997年 | 141篇 |
1996年 | 109篇 |
1995年 | 76篇 |
1994年 | 75篇 |
1993年 | 100篇 |
1992年 | 64篇 |
1991年 | 55篇 |
1990年 | 32篇 |
1989年 | 21篇 |
1988年 | 20篇 |
1987年 | 22篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1973年 | 2篇 |
1959年 | 1篇 |
1958年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有9081条查询结果,搜索用时 15 毫秒
31.
In this paper, a new theoretical expression of dissipation term is presented on the basis of statistical model of breaking wave, which is an improvement to LAGFD-WAM wave model. The computational results in three typical wind fields show a good improvement to LAGFD-WAM model and a better accuracy in comparison with the observed data in the South China Sea. 相似文献
32.
Konstantin V. Lebedev Max Yaremchuk Humio Mitsudera Iwao Nakano Gang Yuan 《Journal of Oceanography》2003,59(6):751-763
A finite-difference quasigeostrophic (QG) model of an open ocean region has been employed to produce a dynamically constrained
synthesis of acoustic tomography and satellite altimetry data with in situ observations. The assimilation algorithm is based upon the 4D variational data interpolation scheme controlled by the model's
initial and boundary conditions. The data sets analyzed include direct and differential travel times measured at the array
of five acoustic transceivers deployed by JAMSTEC in the region of the Kuroshio Extension in 1997, Topex/Poseidon altimetry,
CTD soundings, and ADCP velocity profiles. The region monitored is located within the area 27.5°–36.5°N, 143°–155°. The results
of assimilation show that mesoscale variability can be effectively reconstructed by five transceivers measuring direct and
reciprocal travel times supported by relatively sparse in situ measurements. The misfits between model and data lie within the observational error bars for all the data types used in assimilation.
We have compared the results of assimilation with the statistical inversion of travel time data and analyzed energy balances
of the optimized model solution. Energy exchange between the depth-averaged and shear components of the observed currents
reveals a weak decay of the barotropic mode at the rate of 0.2 ± 0.7⋅10−5 cm2/s3 due to topographic interaction. Mean currents in the region are unstable with an estimate of the available potential energy
flux from the mean current to the eddies of 4.7 ± 2.3⋅10−5 cm2/s3. Kinetic energy transition has the same sign and is estimated as 2.8 ± 2.5⋅10−5 cm2/s3. Potential enstrophy is transferred to the mesoscale at a rate of 5.5 ± 2.7⋅10−18 s−3. These figures provide observational evidence of the properties of free geostrophic turbulence which were predicted by theory
and observed in numerical experiments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
33.
Extrapolating from the propagation theories of electromagnetic waves in a layered medium, a three-layer medium model is deduced in this paper by using microwave radiometric remote sensing technology which is suitable to first-year sea ice condition of the northern part of China seas. Comparison with in situ data indicates that for microwave wavelength of 10 cm, the coherent model gives a quite good fit result for the thickness of sea ice less than 20 cm, and the incoherent model also works well for thickness within 20 to 40 cm. Based on three theoretical models, the inversion soft ware from microwave remote sensing data for calculating the thickness of sea ice can be set up. The relative complex dielectrical constants of different types of sea ice in the Liaodong Gulf calculated by using these theoretical models and measurement data are given in this paper. The extent of their values is (0. 5-4. 0)-j(0. 07~0. 19). 相似文献
34.
35.
This paper proposes a nonlinear robust adaptive control strategy to force a six degrees of freedom underactuated underwater vehicle with only four actuators to follow a predefined path at a desired speed despite of the presence of environmental disturbances and vehicle’s unknown physical parameters. The proposed controller is designed using Lyapunov’s direct method, the popular backstepping and parameter projection techniques. The closed loop path following errors can be made arbitrarily small. Interestingly, it is shown that our developed control strategy is easily extendible to situations of practical importance such as parking and point-to-point navigation. Numerical simulations are provided to illustrate the effectiveness of the proposed methodology. 相似文献
36.
对海水中Zn(Ⅱ),Ca(Ⅱ),Cd(Ⅱ)与高岭石、伊利石和蒙脱石等粘土矿物;无定形水合氧化铁、α-FeOOH等铁的水合氧化物;δ-MaO_2,γ-MnOOH,水锰矿等锰的水合氧化物等30个左右实验体系的液-固界面台阶型动力学曲线进行了系统的实验测定和全面的条件研究。在实验测定上提出两种方法、互为校核。对动力学曲线之台阶的消长和变化规律作了系统研究,确定主要影响因素是:金属离子初始浓度、固体交换剂量、体系的pH值和温度,以及搅拌速度等。 相似文献
37.
38.
作者引入 I(L)值完全下半连续映射 ,研究其性质。利用 I(L)值完全下半连续映射定义I(L)值完全诱导空间 ,给出 I(L)值完全诱导空间的拓扑基的表达形式 ,证得两个 I(L)值完全诱导空间的映射是连续映射的充分必要条件 ,并建立了乘积空间的 I(L)值完全诱导空间与 I(L)值完全诱导空间的乘积空间的联系 相似文献
39.
对于含多资料三维分潮波模型建立了一种岸边资料运动学外推的潮波第一边值方法,并对渤海的四大原湖波进行试算。结果证实本方法可行,该方法使潮波方程既满足第一边值问题,充分利用岸边测站资料,又保证岸界法向流速为零条件,符合物理意义。并对复型病态矩阵的收敛问题提出了一种可行性处理。 相似文献
40.
Circulations east of Taiwan and in East China Sea and east of Ryukyu Islands during early summer 1985YuanYaochu;Cho-tengLiu;P... 相似文献