全文获取类型
收费全文 | 51085篇 |
免费 | 8106篇 |
国内免费 | 11036篇 |
专业分类
测绘学 | 4648篇 |
大气科学 | 5204篇 |
地球物理 | 9867篇 |
地质学 | 29387篇 |
海洋学 | 5343篇 |
天文学 | 4616篇 |
综合类 | 3334篇 |
自然地理 | 7828篇 |
出版年
2024年 | 272篇 |
2023年 | 707篇 |
2022年 | 1414篇 |
2021年 | 1584篇 |
2020年 | 1662篇 |
2019年 | 1908篇 |
2018年 | 1498篇 |
2017年 | 1772篇 |
2016年 | 1934篇 |
2015年 | 2100篇 |
2014年 | 2567篇 |
2013年 | 2545篇 |
2012年 | 2906篇 |
2011年 | 3083篇 |
2010年 | 2618篇 |
2009年 | 3337篇 |
2008年 | 3297篇 |
2007年 | 3677篇 |
2006年 | 3541篇 |
2005年 | 3086篇 |
2004年 | 2897篇 |
2003年 | 2802篇 |
2002年 | 2466篇 |
2001年 | 2155篇 |
2000年 | 1978篇 |
1999年 | 1858篇 |
1998年 | 1638篇 |
1997年 | 1418篇 |
1996年 | 1290篇 |
1995年 | 1074篇 |
1994年 | 1112篇 |
1993年 | 947篇 |
1992年 | 748篇 |
1991年 | 528篇 |
1990年 | 476篇 |
1989年 | 377篇 |
1988年 | 288篇 |
1987年 | 193篇 |
1986年 | 124篇 |
1985年 | 85篇 |
1984年 | 35篇 |
1983年 | 29篇 |
1982年 | 33篇 |
1981年 | 21篇 |
1980年 | 24篇 |
1979年 | 29篇 |
1978年 | 35篇 |
1977年 | 25篇 |
1975年 | 4篇 |
1954年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Yoshio Kubo 《Celestial Mechanics and Dynamical Astronomy》1990,50(2):165-187
Hamiltonian mechanics is applied to the problem of the rotation of the elastic Earth. We first show the process for the formulation of the Hamiltonian for rotation of a deformable body and the derivation of the equations of motion from it. Then, based on a simple model of deformation, the solution is given for the period of Euler motion, UT1 and the nutation of the elastic Earth. In particular it is shown that the elasticity of the Earth acts on the nutation so as to decrease the Oppolzer terms of the nutation of the rigid Earth by about 30 per cent. The solution is in good agreement with results which have been obtained by other, different approaches. 相似文献
12.
本文以丰富的实际资料,论证了地下水的卤素元素(F、Cl、Br、I)的形成、含量及其分布规律与含水介质成分、上覆岩土性质、地下水退流条件、氧化还原环境、地下水矿化度之间的关系。根据江汉平原东部区和鄱阳湖区地下水中Br、I元素的调查研究结果及它们形成的控制因素与分布规律,结合长江三角洲南部区水文地球化学环境条件分析对比,指出该区是一个形成Br、I矿泉水的有利地区。 相似文献
13.
T. H. BELL S. E. JOHNSON B. DAVIS A. FORDE N. HAYWARD C. WILKINS 《Journal of Metamorphic Geology》1992,10(3):295-307
Extensive examination of large numbers of spatially orientated thin sections of orientated samples from orogens of all ages around the world has demonstrated that porphyroblasts do not rotate relative to geographical coordinates during highly non-coaxial ductile deformation of the matrix subsequent to their growth. This has been demonstrated for all tectonic environments so far investigated. The work also has provided new insights and data on metamorphic, structural and tectonic processes including: (1) the intimate control of deformation partitioning on metamorphic reactions; (2) solutions to the lack of correlation between lineations that indicate the direction of movement within thrusts and shear zones, and relative plate motion; and (3) a possible technique for determining the direction of relative plate motion that caused orogenesis in ancient orogens. 相似文献
14.
15.
16.
17.
O. Tamuz T. Mazeh S. Zucker † 《Monthly notices of the Royal Astronomical Society》2005,356(4):1466-1470
We suggest a new algorithm to remove systematic effects in a large set of light curves obtained by a photometric survey. The algorithm can remove systematic effects, such as those associated with atmospheric extinction, detector efficiency, or point spread function changes over the detector. The algorithm works without any prior knowledge of the effects, as long as they linearly appear in many stars of the sample. The approach, which was originally developed to remove atmospheric extinction effects, is based on a lower rank approximation of matrices, an approach which has already been suggested and used in chemometrics, for example. The proposed algorithm is especially useful in cases where the uncertainties of the measurements are unequal. For equal uncertainties, the algorithm reduces to the Principal Component Analysis (PCA) algorithm. We present a simulation to demonstrate the effectiveness of the proposed algorithm and we point out its potential, in the search for transit candidates in particular. 相似文献
18.
N. Ivanova K. Belczynski J. M. Fregeau F. A. Rasio 《Monthly notices of the Royal Astronomical Society》2005,358(2):572-584
We study the evolution of binary stars in globular clusters using a new Monte Carlo approach combining a population synthesis code ( startrack ) and a simple treatment of dynamical interactions in the dense cluster core using a new tool for computing three- and four-body interactions ( fewbody ). We find that the combination of stellar evolution and dynamical interactions (binary–single and binary–binary) leads to a rapid depletion of the binary population in the cluster core. The maximum binary fraction today in the core of a typical dense cluster such as 47 Tuc, assuming an initial binary fraction of 100 per cent, is only ∼ 5–10 per cent. We show that this is in good agreement with recent Hubble Space Telescope observations of close binaries in the core of 47 Tuc, provided that a realistic distribution of binary periods is used to interpret the results. Our findings also have important consequences for the dynamical modelling of globular clusters, suggesting that 'realistic models' should incorporate much larger initial binary fractions than has usually been the case in the past. 相似文献
19.
20.
We present new 1.45-1.75 μm spectra of Europa's dark non-ice material with a spectral resolution (λ/δλ) of 1200, obtained by using adaptive optics on the Keck telescope to spatially separate the spectrum of the non-ice material from that of the surrounding ice-rich regions. Despite the great increase in spectral resolution over the previous best spectra of the non-ice material, taken with Galileo's near-infrared mapping spectrometer (NIMS) with λ/δλ=66, no new fine-scale spectral structure is revealed. The smoothness of the spectra is inconsistent with available laboratory spectra of crystalline hydrated salts at Europa temperatures, but is more consistent with various combinations of non-crystalline hydrated salts and/or hydrated sulfuric acid, as have been matched to the lower-resolution NIMS spectra. 相似文献