全文获取类型
收费全文 | 60764篇 |
免费 | 10788篇 |
国内免费 | 14474篇 |
专业分类
测绘学 | 4871篇 |
大气科学 | 8275篇 |
地球物理 | 13383篇 |
地质学 | 36110篇 |
海洋学 | 7646篇 |
天文学 | 2209篇 |
综合类 | 4156篇 |
自然地理 | 9376篇 |
出版年
2024年 | 377篇 |
2023年 | 955篇 |
2022年 | 1795篇 |
2021年 | 2204篇 |
2020年 | 2260篇 |
2019年 | 2555篇 |
2018年 | 2071篇 |
2017年 | 2337篇 |
2016年 | 2490篇 |
2015年 | 2688篇 |
2014年 | 3372篇 |
2013年 | 3535篇 |
2012年 | 3591篇 |
2011年 | 3864篇 |
2010年 | 3370篇 |
2009年 | 3861篇 |
2008年 | 3856篇 |
2007年 | 4262篇 |
2006年 | 4161篇 |
2005年 | 3644篇 |
2004年 | 3407篇 |
2003年 | 3234篇 |
2002年 | 2892篇 |
2001年 | 2541篇 |
2000年 | 2369篇 |
1999年 | 2157篇 |
1998年 | 1859篇 |
1997年 | 1700篇 |
1996年 | 1495篇 |
1995年 | 1272篇 |
1994年 | 1291篇 |
1993年 | 1072篇 |
1992年 | 845篇 |
1991年 | 605篇 |
1990年 | 526篇 |
1989年 | 441篇 |
1988年 | 314篇 |
1987年 | 216篇 |
1986年 | 136篇 |
1985年 | 101篇 |
1984年 | 45篇 |
1983年 | 38篇 |
1982年 | 34篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 30篇 |
1978年 | 40篇 |
1977年 | 24篇 |
1971年 | 4篇 |
1954年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
91.
Fabio Fontanot Pierluigi Monaco Stefano Borgani 《Monthly notices of the Royal Astronomical Society》2003,341(2):692-706
We apply the ztrace algorithm to the optical NOG and infrared PSC z galaxy catalogues to reconstruct the pattern of primordial fluctuations that have generated our local Universe. We check that the density fields traced by the two catalogues are well correlated, and consistent with a linear relation [either in δ or in log (1 +δ) ] with relative bias (of NOG with respect to PSC z ) b rel = 1.1 ± 0.1 . The relative bias relation is used to fill the optical zone of avoidance at | b | < 20° using the PSC z galaxy density field.
We perform extensive testing on simulated galaxy catalogues to optimize the reconstruction. The quality of the reconstruction is predicted to be good at large scales, up to a limiting wavenumber klim ≃ 0.4 h Mpc−1 beyond which all information is lost. We find that the improvement arising from the denser sampling of the optical catalogue is compensated by the uncertainties connected to the larger zone of avoidance.
The initial conditions reconstructed from the NOG catalogue are found (analogously to those from the PSC z ) to be consistent with a Gaussian paradigm. We use the reconstructions to produce sets of initial conditions ready to be used for constrained simulations of our local Universe. 相似文献
We perform extensive testing on simulated galaxy catalogues to optimize the reconstruction. The quality of the reconstruction is predicted to be good at large scales, up to a limiting wavenumber k
The initial conditions reconstructed from the NOG catalogue are found (analogously to those from the PSC z ) to be consistent with a Gaussian paradigm. We use the reconstructions to produce sets of initial conditions ready to be used for constrained simulations of our local Universe. 相似文献
92.
松辽盆地中生代沉积基准面变化研究 总被引:6,自引:0,他引:6
利用地质资料研究来恢复沉积基准面变化。首先根据沉积物的分布规律、沉积构造、古生物组合及古生态、自生矿物和波基面等特征来获得古水深,然后利用对地层做脱水压实校正获得沉积物原始厚度。对湖盆地区古水深和沉积物原始厚度累加起来就可得到沉积基准面变化曲线。沉积基准面变化曲线为在松辽盆地中进行地层对比提供了依据。 相似文献
93.
Nikolay Sidorenkov 《Celestial Mechanics and Dynamical Astronomy》2003,87(1-2):27-38
Spectral analysis of the components of the relative atmospheric angular momentum vector is performed based on the series of these components for the 6 h intervals within the period of 1958–2000. These series have been computed in the Subbureau of the Atmospheric Angular Momentum of the International Earth Rotation Service using the NCEP/NCAR reanalysis of atmospheric observations. The basic harmonics of diurnal tides are determined. New results on the fortnight's and week's duration oscillations of the equatorial components of the atmospheric angular momentum are obtained. The zonal tides transformation mechanisms in the atmosphere are discussed. It is shown that the main mechanism of the zonal tides effect on the atmospheric variability is the amplitude modulation of daily oscillations of the relative atmospheric angular momentum. The effects of the atmospheric tides on the Earth rotation are discussed. 相似文献
94.
95.
本文论述了保安地区火山岩的地质、岩石、副矿物、岩石化学、微量元素、稀土元素、稳定同位素、火山岩相及火山机构等特征。并对其演化规律、形成机制与成矿作用的关系,作了初步探讨。 相似文献
96.
张小波 《广东海洋大学学报》2004,24(5):70-74
通过对辜鸿铭所翻译的《中庸》、《论语》进行分析和研究 ,反映出社会背景对中国古典文化经典翻译的不同策略的影响。从而证明辜鸿铭译文的别出心裁出于强势语下的无奈。从翻译理论上揭示归化翻译的历史意义以及译品存在的价值。 相似文献
97.
A coupled deterministic hydrological and water temperature model, CEQUEAU, was modified to include soil temperature and crown closure in its calculation of local advective terms in the heat budget. The modified model was than tested to verify its sensitivity to these modifications. An analysis of the heat budget of a small forested catchment in eastern Canada revealed that the advective term related to interflow plays a significant role in the daily water heat budget, providing on average 28% of the local advective budget (which also includes advective heat terms from surface runoff and groundwater) and nearly 14% of the total heat budget (which includes all radiative terms at the water surface, convection and evaporation, as well as the local advective terms). Relative sensitivity indices (RSIs) were used to verify the impact of the newly introduced parameters and variables. Among them, parameters related to the forest cover (crown closure and leaf area index) have a maximum RSI of ?0·6; i.e. a 100% increase in value produces a 60% decrease in the local advective term. Parameters with the greatest influence are the volume of water contributing to interflow and the amplitude of the net radiative flux at the soil surface, which, if doubled, would double the contribution of the local interflow advective term to the heat budget. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
98.
For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring‐early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70‐year‐old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high‐latitude stands. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
99.
Szilárd Csizmadia Zsolt Kővári Péter Klagyivik 《Astrophysics and Space Science》2006,304(1-4):355-357
We carried out optical and Hα photometry of two contact binaries (V861 Herculis, EQ Tauri). The light curve modeling revealed stellar spots in both contact systems and strong Hα excess in the position of the observed stellar spots. A correlation was found between the V−R and R−Hα colour indices of V861 Her. 相似文献
100.