全文获取类型
收费全文 | 21247篇 |
免费 | 3585篇 |
国内免费 | 4215篇 |
专业分类
测绘学 | 1433篇 |
大气科学 | 2335篇 |
地球物理 | 2724篇 |
地质学 | 11311篇 |
海洋学 | 3022篇 |
天文学 | 2537篇 |
综合类 | 1436篇 |
自然地理 | 4249篇 |
出版年
2024年 | 62篇 |
2023年 | 204篇 |
2022年 | 618篇 |
2021年 | 738篇 |
2020年 | 698篇 |
2019年 | 867篇 |
2018年 | 706篇 |
2017年 | 780篇 |
2016年 | 816篇 |
2015年 | 907篇 |
2014年 | 1145篇 |
2013年 | 1013篇 |
2012年 | 1272篇 |
2011年 | 1276篇 |
2010年 | 1096篇 |
2009年 | 1498篇 |
2008年 | 1299篇 |
2007年 | 1601篇 |
2006年 | 1577篇 |
2005年 | 1470篇 |
2004年 | 1333篇 |
2003年 | 1277篇 |
2002年 | 1109篇 |
2001年 | 885篇 |
2000年 | 742篇 |
1999年 | 679篇 |
1998年 | 585篇 |
1997年 | 458篇 |
1996年 | 400篇 |
1995年 | 368篇 |
1994年 | 311篇 |
1993年 | 266篇 |
1992年 | 253篇 |
1991年 | 188篇 |
1990年 | 122篇 |
1989年 | 186篇 |
1988年 | 78篇 |
1987年 | 54篇 |
1986年 | 33篇 |
1985年 | 19篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1954年 | 4篇 |
1877年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
文章阐述了地勘单位物业管理社会化的必然性和内函 ,提出发展地勘单位物业管理的基本内容和需要解决的问题 ,最终实现以业养业 ,自我发展。 相似文献
92.
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
93.
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
94.
Ramona Núñez-López Anton Lipovka Vladimir Avila-Reese 《Monthly notices of the Royal Astronomical Society》2006,369(4):2005-2012
Possible detection of signatures of structure formation at the end of the 'dark age' epoch ( z ∼ 40–20) is examined. We discuss the spectral–spatial fluctuations in the cosmic microwave background radiation (CMBR) temperature produced by elastic resonant scattering of CMBR photons on deuterated hydrogen (HD) molecules located in protostructures moving with peculiar velocity. Detailed chemical kinematic evolution of HD molecules in the expanding homogeneous medium is calculated. Then, the HD abundances are linked to protostructures at their maximum expansion, whose properties are estimated by using the top-hat spherical approach and the Λ cold dark matter (ΛCDM) cosmology. We find that the optical depths in the HD three lowest pure rotational lines for high-peak protohaloes at their maximum expansion are much higher than those in LiH molecule. The corresponding spectral–spatial fluctuation amplitudes, however, are probably too weak to be detected by current and forthcoming millimetre telescope facilities. We extend our estimates of spectral–spatial fluctuations to gas clouds inside collapsed CDM haloes by using results from a crude model of HD production in these clouds. The fluctuations for the highest peak CDM haloes at redshifts ∼20–30 could be detected in the future. Observations will be important to test model predictions of early structure formation in the Universe. 相似文献
95.
96.
FUZZY COMPREHENSIVE EVALUATION OF CONTAINER TRANSPORTATION MODES ALONG THE CHANGJIANG RIVER MAIN LINE AND ITS DELTA AREA 总被引:1,自引:0,他引:1
ZHANGShi-yu XIAOHan-liang 《中国地理科学(英文版)》2003,13(3):259-261
The Changjiang River (Yangtze) is one of the fastest growth areas of container transportation in Chi-na. Rail, road and water transportation have competed against each other for container transportation in the Chang-jiang River main line and its delta area. It is of significance to assess these different transportation modes scientifi-cally in order to organize container transportation efficiently in this area and make decision for integral plan and construction of transportation system in this area. This paper outlines application of fuzzy comprehensive evaluation to appraise different modes of typical direction of containers. Twelve assessment indexes were decided. Membership functions were formulated. Evaluation results indicated that road transportation was optimal mode in the Changjiang River delta area, however water transportation was the primary way in the Changjiang River main line. 相似文献
97.
S.W. Allen 《Astrophysics and Space Science》2003,285(1):247-256
Chandra X-ray observations of rich, dynamically relaxed galaxy clusters allow the properties of the X-ray gas and the total
gravitating mass to be determined precisely. Here, we discuss how Chandra observations may be used as a powerful tool for
cosmological studies. By combining Chandra X-ray results on the X-ray gas mass fractions in clusters with independent measurements
of the Hubble constant and the mean baryonic matter density of the universe, we obtain a tight constraint on the mean total
matter density of the universe, Οm, and an interesting constraint on the cosmological constant, ΟΛ. Using these results, together with the observed local X-ray luminosity function of the most X-ray luminous galaxy clusters,
a mass-luminosity relation determined from Chandra and ROSAT X-ray data and weak gravitational lensing observations, and the
mass function predicted by numerical simulations, we obtain a precise constraint on the normalization of the power spectrum
of density fluctuations in the nearby universe,σ8. We compare our results with those obtained from other, independent methods.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
98.
99.
100.