全文获取类型
收费全文 | 3567篇 |
免费 | 634篇 |
国内免费 | 670篇 |
专业分类
测绘学 | 365篇 |
大气科学 | 309篇 |
地球物理 | 1131篇 |
地质学 | 1379篇 |
海洋学 | 331篇 |
天文学 | 994篇 |
综合类 | 156篇 |
自然地理 | 206篇 |
出版年
2024年 | 9篇 |
2023年 | 39篇 |
2022年 | 87篇 |
2021年 | 111篇 |
2020年 | 139篇 |
2019年 | 135篇 |
2018年 | 102篇 |
2017年 | 150篇 |
2016年 | 172篇 |
2015年 | 188篇 |
2014年 | 211篇 |
2013年 | 188篇 |
2012年 | 188篇 |
2011年 | 202篇 |
2010年 | 168篇 |
2009年 | 298篇 |
2008年 | 250篇 |
2007年 | 303篇 |
2006年 | 268篇 |
2005年 | 210篇 |
2004年 | 216篇 |
2003年 | 180篇 |
2002年 | 158篇 |
2001年 | 141篇 |
2000年 | 115篇 |
1999年 | 115篇 |
1998年 | 116篇 |
1997年 | 52篇 |
1996年 | 60篇 |
1995年 | 44篇 |
1994年 | 46篇 |
1993年 | 46篇 |
1992年 | 37篇 |
1991年 | 34篇 |
1990年 | 24篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1954年 | 5篇 |
排序方式: 共有4871条查询结果,搜索用时 15 毫秒
951.
Krzysztof Rochowicz 《Astrophysics and Space Science》1996,238(1):71-74
Ultraviolet spectra of population I WR stars obtained from IUE archive are used to determine fundamental stellar parameters. Terminal velocities for 85 galactic and LMC Wolf-Rayet stars were obtained by means of the empirical relation between spectral quantities easily measured in low resolution and high-resolution terminal velocity measurements. Temperatures and so-called transformed radii were derived based on available contour plots of spectral characteristics for a grid of NLTE models. The effect of the reddening law on stellar far ultraviolet continua is emphasized and the revised extinction curve towards WR stars is used for dereddening. For the sample of stars attributed to open clusters or associations we construct the stellar distance scale and adopt it for the other WR stars. The remaining fundamental parameters are derived and HR diagram for population I WR stars is presented. 相似文献
952.
论述了太阳二维光谱观测和研究的重大意义,综述了二维光谱观测技术和仪器的进展,特别介绍了应用CCD的成像光谱仪的最近发展。文中还介绍了近年来二维光谱观测研究所取得的一些新结果,展望了未来观测技术和课题研究的发展前景。 相似文献
953.
合成孔经雷达(Synthetic Aperture Radar,SAR)是当今微波遥感领域的研究热点,其全天候、全天时、高分辨率以及穿透地表等特点使其具备其他传感器不可比拟的优势,因此得到了极其广泛的应用。成像处理是SAR技术的核心部分。分析了星载SAR点目标回波信号模型和几种常用的星载SAR数字成像处理算法。以距离-多普勒算法为例,阐述了距离压缩和方位压缩的实质,详细讨论了多普勒参数估计、距离徙动校正和斑点噪声的去除等几个关键的问题。采用ERS-1卫星数据做了成像实验,并对SAR成像技术加以总结。 相似文献
954.
Chun-Hua Zhu Chao-Zheng Zha Department of Physics Xinjiang University Urumqi 《中国天文和天体物理学报》2005,5(4):419-425
By means of a population synthesis code, we investigate the Mira variables. Their birth rate (over 0.65 yr-1) and their number (-130000) in the Galaxy are estimated. For all possible Mira variables, ranges of their initial masses, pulsating periods, mass losses and lifetimes are given. We check our model with the observed Mira variables near the Sun and our results prove to be valid. 相似文献
955.
亚热带山区泥石流的形成过程 总被引:1,自引:0,他引:1
本文应用地貌学、水文学等方法进行了泥石流源地分类,阐述了各类源地泥石流形成过程,分析了各类源地的地貌演变对泥石流形成过程的影响。 相似文献
956.
Y. Frémat P. Lampens H. Hensberge 《Monthly notices of the Royal Astronomical Society》2005,356(2):545-556
DG Leo is a spectroscopic triple system composed of three stars of late-A spectral type, one of which was suggested to be a δ Scuti star. Seven nights of observations at high spectral and high time-resolution at the Observatoire de Haute-Provence with the ELODIE spectrograph were used to obtain the component spectra by applying a Fourier transform spectral disentangling technique. Comparing these with synthetic spectra, the stellar fundamental parameters (effective temperature, surface gravity, projected rotation velocity and chemical composition) are derived. The inner binary consists of two Am components, at least one of which is not yet rotating synchronously at the orbital period though the orbit is a circular one. The distant third component is confirmed to be a δ Scuti star with normal chemical composition. 相似文献
957.
The Grey System is a method for making quantitative predictions using the similarity between a parent sequence and a set of subsequences. It has previously been used for non-geological problems, but here we demonstrate its use in ore prediction. Our example is from our work on known Cu deposits distributed in the Panzihua-Xichang region of Sichuan Province to set up a Grey prediction model for an unknown deposit in a similar type of environment. The following steps were carried out: (1) a sift selection was first made by logical information processing of the initial data from the known deposits, (2) data on seven deposits belonging to the same general rock type were obtained, and (3) a Grey prediction model was set up and used to make predictions about an unknown deposit in the same type of environment. 相似文献
958.
959.
Jia Pei-zhang 《Chinese Astronomy and Astrophysics》1992,16(4):465-472
A method of joint estimation of the parameters and the variance σ2 in the linear model is presented in this paper. The M-estimators with finite rejection points are adopted for estimating the parameters. In order to estimate the variance σ2, the Grubbs statistics and the Kurtosis test statistics are adopted to test the residual sequence {;ri};. And the sample variance of {;ri}; after discarding the outliers is taken as the estimation of σ2. This method of estimating σ2 is less computational demanding and more accurate, compared with the well-known method which takes 1.483 medi |ri| as the estimation of σ. The breakdown point of the above estimation of σ2 is more than 20%, while the brekdown point is less than 10%, if only the Grubbs statistics is used. 相似文献
960.
本文介绍了应用三轴风速仪测试大气扩散参数的方法和原理,计算了成都平原大气扩散参数,并对其结果进行了分析,提出了本地区应用三轴风速仪可以代替平衡球的依据,并对三轴法的优缺点进行了评价。指出了以往将静风与有风时处理混为一起的不合理性。 相似文献