全文获取类型
收费全文 | 54616篇 |
免费 | 9957篇 |
国内免费 | 12729篇 |
专业分类
测绘学 | 4463篇 |
大气科学 | 7052篇 |
地球物理 | 12501篇 |
地质学 | 30295篇 |
海洋学 | 8036篇 |
天文学 | 3174篇 |
综合类 | 3708篇 |
自然地理 | 8073篇 |
出版年
2024年 | 194篇 |
2023年 | 546篇 |
2022年 | 1420篇 |
2021年 | 1706篇 |
2020年 | 1801篇 |
2019年 | 2268篇 |
2018年 | 1768篇 |
2017年 | 1950篇 |
2016年 | 2101篇 |
2015年 | 2381篇 |
2014年 | 2882篇 |
2013年 | 2889篇 |
2012年 | 3241篇 |
2011年 | 3495篇 |
2010年 | 2941篇 |
2009年 | 3607篇 |
2008年 | 3532篇 |
2007年 | 4056篇 |
2006年 | 3855篇 |
2005年 | 3367篇 |
2004年 | 3207篇 |
2003年 | 3035篇 |
2002年 | 2668篇 |
2001年 | 2363篇 |
2000年 | 2193篇 |
1999年 | 2048篇 |
1998年 | 1800篇 |
1997年 | 1574篇 |
1996年 | 1490篇 |
1995年 | 1250篇 |
1994年 | 1253篇 |
1993年 | 1063篇 |
1992年 | 821篇 |
1991年 | 606篇 |
1990年 | 507篇 |
1989年 | 399篇 |
1988年 | 302篇 |
1987年 | 200篇 |
1986年 | 137篇 |
1985年 | 95篇 |
1984年 | 40篇 |
1983年 | 33篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1980年 | 27篇 |
1979年 | 30篇 |
1978年 | 36篇 |
1977年 | 26篇 |
1975年 | 4篇 |
1954年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Yulia A. Chernetenko 《Celestial Mechanics and Dynamical Astronomy》2001,80(3-4):185-194
International programs of observations of selected minor planets have lasted about 50 years and the last one comes to the end in 2000. The main aim of these observational programs consists in obtaining the orientation of the stellar reference frame with respect to the dynamical one using observations of the bright minor planets. The observations are also useful for the orbital improvements of the asteroids themselves. They are available from the author via e-mail at the address .During the above mentioned period more than 23 000 observations of minor planets, referred to different reference star catalogues, have been obtained. The reduction procedure of observations to the PPM star catalogue is described. The orientation parameters are given and discussed. 相似文献
82.
K. Nagamine † M. Fukugita R. Cen J.P. Ostriker 《Monthly notices of the Royal Astronomical Society》2001,327(1):L10-L14
The luminosity function of galaxies is derived from a cosmological hydrodynamic simulation of a Λ cold dark matter universe with the aid of a stellar population synthesis model. At , the resulting B -band luminosity function has a flat faint-end slope of with the characteristic luminosity and the normalization in fair agreement with observations, while the dark matter halo mass function is steep with a slope of . The colour distribution of galaxies also agrees well with local observations. We also discuss the evolution of the luminosity function, and the colour distribution of galaxies from to 5. A large evolution of the characteristic mass in the stellar mass function as a result of number evolution is compensated by luminosity evolution; the characteristic luminosity increases only by 0.8 mag from to 2, and then declines towards higher redshift, while the B -band luminosity density continues to increase from to 5 (but only slowly at . 相似文献
83.
Jonathan Mackey Martin White Marc Kamionkowski 《Monthly notices of the Royal Astronomical Society》2002,332(4):788-798
It has recently been argued that the observed ellipticities of galaxies may be determined at least in part by the primordial tidal gravitational field in which the galaxy formed. Long-range correlations in the tidal field could thus lead to an ellipticity–ellipticity correlation for widely separated galaxies. We present a new model relating ellipticity to angular momentum, which can be calculated in linear theory. We use this model to calculate the angular power spectrum of intrinsic galaxy shape correlations. We show that, for low-redshift galaxy surveys, our model predicts that intrinsic correlations will dominate correlations induced by weak lensing, in good agreement with previous theoretical work and observations. We find that our model produces ' E -mode' correlations enhanced by a factor of 3.5 over B -modes on small scales, making it harder to disentangle intrinsic correlations from those induced by weak gravitational lensing. 相似文献
84.
85.
K. A. van der Hucht 《Astronomy and Astrophysics Review》1992,4(2):123-159
Summary Recent literature on Population I Wolf-Rayet star research extending from the Milky Way to blue compact dwarf galaxies is reviewed, broken down into inventory, basic parameters and galactic distribution, atmospheres, binaries, intrinsic variability, mass loss, enrichment and evolution. Also the incidence of Wolf-Rayet stars with variable non-thermal radio emission, excess X-ray fluxes, and episodic/periodic IR excesses is reviewed. These phenomena appear to be associated with wind-wind interaction in wide long-period WR+OB binaries and with wind-compact object interaction in WR+c binaries, with orbit sizes of the order of magnitude of the WR radio photosphere sizes or larger. 相似文献
86.
本文介绍了瞬变电磁法在煤矿水文地质勘探中的具体应用效果.采用瞬变电磁法对落差较大断层的含(导)水性进行测量,不仅可有效地控制断层的空间位置,而且可定性地判断断层的富水性,其测量结果与已知水文地质资料吻合较好. 相似文献
87.
88.
应用显微光度术、显微傅立叶红外光谱(Micro-FT.IR)和飞行时间二次离子质谱(TOF-SIMS)等原位微分析技术并结合均一温度测量对胜利油气区下第三系沙河街组沙三段中有机包裹体进行了研究。区分出两类有机包裹体,即原生有机包裹体和次生有机包裹体。结果表明两类有机包裹体特征不同,二者物质组成、有机质成分及化学结构、热演化程度等差别也较大。结合地质分析表明原生有机包裹体是沙三段烃源岩生成烃类运移产物,具“自生自储”特点,而次生有机包裹体是沙四段烃源岩生成的烃类二次运移的产物。沙三段是沙河街组油气运移和聚集的主要层位,因而是寻找油气资源的主要目标层。研究表明,有机包裹体是研究油气生成、运移、聚集和演化等成藏系统最有效的手段之一,在油气勘探中有重要的应用意义。 相似文献
89.
In this paper, we idealize the actual solar atmosphere as a multi-isothermal-layer system so as to obtain the energy transmittance of the linear Alfvén wave that propagates through such a system in presence of a uniform oblique magnetic filed. The results indicate that the two-layer model is essentially different to the three-layer one. In the two-layer model, the temperature jump acts as a high pass filter. In the three-layer model, resonant transfer will take place and the transmittance undergoes oscillation as the trigonometric function terms dominate its behavior. For actual solar atmosphere, the result reveals that the lower parts of solar atmosphere are more suitable for those Alfvén waves with period of seconds to transfer their energy. 相似文献
90.
使用中国科学院紫金山天文台青海站13.7米射电望远镜于1996年12月至1997年1月对富碳拱星IRC 10216和CIT6的CO J=1-0跃迁(115GHz)进行了观测。在观测谱线的基础上得到了IRC 10216的视向速度和膨胀速度分别为一26.1km s~(-1)和14.8km s~(-1),CIT6的视向速度和膨胀速度分别为0.6km s~(-1)和13.8kms~(-1)。并对望远镜的射束及指向精度进行了研究。 相似文献