全文获取类型
收费全文 | 460篇 |
免费 | 35篇 |
国内免费 | 26篇 |
专业分类
测绘学 | 56篇 |
大气科学 | 59篇 |
地球物理 | 71篇 |
地质学 | 54篇 |
海洋学 | 29篇 |
天文学 | 224篇 |
综合类 | 12篇 |
自然地理 | 16篇 |
出版年
2024年 | 4篇 |
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 6篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 5篇 |
2017年 | 15篇 |
2016年 | 9篇 |
2015年 | 18篇 |
2014年 | 17篇 |
2013年 | 12篇 |
2012年 | 17篇 |
2011年 | 19篇 |
2010年 | 16篇 |
2009年 | 23篇 |
2008年 | 25篇 |
2007年 | 39篇 |
2006年 | 21篇 |
2005年 | 32篇 |
2004年 | 32篇 |
2003年 | 25篇 |
2002年 | 20篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 14篇 |
1996年 | 4篇 |
1995年 | 15篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1982年 | 1篇 |
排序方式: 共有521条查询结果,搜索用时 0 毫秒
51.
E. L. Afraimovich Ya. F. Ashkaliev V. M. Aushev A. B. Beletsky V. V. Vodyannikov L. A. Leonovich O. S. Lesyuta Yu. V. Lipko A. V. Mikhalev A. F. Yakovets 《Journal of Atmospheric and Solar》2002,64(18)
Basic properties of the mid-latitude traveling ionospheric disturbances (TIDs) during the maximum phase of a major magnetic storm of 6–8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics (51.9°N,103.0°E), and MORTI located at the observatory of the Institute of Ionosphere (43.2°N, 77.0°E). Observations of the O (557.7 and 630.0 nm) emissions originating from atmospheric layers centered at altitudes of 90 and 250 km were carried out at Irkutsk and of the O2(b1∑g+−X3∑g−) (0-1) emission originating from an atmospheric layer centered at altitude of 94 km was carried out at Almaty. Our radio and optical measurement network observed a storm-induced solitary large-scale wave with duration of 1 h and a wave front width of no less than 5000 km, while it traveled equatorward with a velocity of 200 m/s from 62°N to 38°N geographic latitude. The TEC disturbance, basically displaying an electron content depression in the maximum of the F2 region, reveals a good correlation with growing nightglow emission, the temporal shift between the TEC and emission variation maxima being different for different altitudes. A comparison of the auroral oval parameters with dynamic spectra of TEC variations and optical 630 nm emissions in the frequency range 0.4–4 mHz (250–2500 s periods) showed that as the auroral oval expands into mid-latitudes, also does the region with a developed medium-sale and small-scale TEC structure. 相似文献
52.
53.
1m红外太阳塔是我国未来重点发展的地面太阳观测设备 ,本文的所有工作均围绕着与此相关的红外波段太阳观测技术方法展开。1 .针对望远镜实验平台—云台太阳光谱仪 ,建立了光谱仪分光流量模型 ,并用多种实验手段验证了其可靠性。利用该模型计算了FeⅠ 1 .56μm红外太阳光谱的分光流量 ,分析了实验观测的可行性及改进方案。2 .针对探测器实验平台—PtSi红外焦平面阵列相机 ,建立了FeⅠ 1 .56μm光谱观测信噪比模型 ,模拟了各种噪声对观测的影响。在此基础上 ,在国内首次成功进行了FeⅠ1 .56μm红外太阳光谱的面阵观测实验。3 .在红外观测实验所处的高背景低对比度条件下 ,讨论了红外太阳光谱观测的图像处理方法 ,分析了观测中出现的干涉条纹的来源及解决办法 ,初步建立起了一整套红外太阳光谱与成像的定标方法和图像处理方法。4 .首次利用PVA材料 ,设计研制了一套FeⅠ 1 .56μm近红外Stokes参量偏振仪 ,并将该偏振仪安装在美国国立天文台McMath望远镜上进行了观测实验。针对一太阳黑子 ,通过扫描进行了二维的Stokes参量观测。同时建立了一套从Stokes参量反演磁矢量场的方法 ,并将反演的结果与怀柔太阳磁场望远镜的观测结果进行了比对。5.针对 1m红外太阳塔的太阳光谱仪系统 ,给出了垂直多波段光谱仪和红外 相似文献
54.
A. G. Shtukenberg Yu. O. Punin E. Haegele H. Klapper 《Physics and Chemistry of Minerals》2001,28(9):665-674
Optical anomalies (deviations of the symmetry of optical properties from the ideal symmetry of the crystal) occur in many
minerals and synthetic compounds and have been under investigation since the last century. An important feature of optically
anomalous mixed crystals is a high degree of optical inhomogeneity, whereas the optical patterns of mixed crystals without
anomalies are usually rather uniform. This work is devoted to the study of this phenomenon. As a model object we have chosen
mixed alum crystals, which were known for their anomalous birefringence and which revealed the following types of optical
inhomogeneities: (1) sector zoning; (2) concentric zoning; (3) subsector zoning; (4) stripes normal to growth front.
The inhomogeneity of anomalous birefringence of mixed crystals of alums can be explained by superposition of several effects:
mismatch strain, strain along dislocations and growth ordering of isomorphous components. Optical inhomogeneities due to the
sector zoning of crystals and their dislocation structure arise even under stationary growth conditions and stationary micromorphology
of the growing face. Both variable growth conditions and the relief of the growing face strongly intensify the optical inhomogeneity
due to three interrelated factors: (1) a significantly inhomogeneous mismatch strain; (2) a variable degree of ordering of
isomorphous components due to the compositional inhomogeneities; (3) different degrees of ordering of isomorphous atoms caused
by different orientations, heights and velocities of growth steps. These effects lead to the formation of subsector zoning
and zoning superimposed on the optical sector zoning. These optical structures are crossed by birefringent stripes arising
from dislocations.
Received: 29 March 2000 / Accepted: 11 March 2001 相似文献
55.
A technique to detect man-made interference in the visibility data of the Mauritius Radio Telescope (MRT) has been developed.
This technique is based on the understanding that the interference is generally ‘spiky’ in nature and has Fourier components
beyond the maximum frequency which can arise from the radio sky and can therefore be identified. We take the sum of magnitudes
of visibilities on all the baselines measured at a given time to improve detectability. This is then high-pass filtered to
get a time series from which the contribution of the sky is removed. Interference is detected in the high-pass data using
an iterative scheme. In each iteration, interference with amplitudes beyond a certain threshold is detected. These points
are then removed from the original time series and the resulting data are high-pass filtered and the process repeated. We
have also studied the statistics of the strength, numbers, time of occurrence and duration of the interference at the MRT.
The statistics indicate that most often the interference excision can be carried out while post-integrating the visibilities
by giving a zero weight to the interference points. 相似文献
56.
本文简要地介绍了云南天文台太阳射电快速记录系统PIN调制器的运用,描述了该器件的结构原理和性能检测,并给出了测试结果 相似文献
57.
《Geofísica Internacional》2014,53(4):385-398
Reflectance spectral curves were analysed by a derivative method. Derivative reflectance spectra revealed concealed peaks of both reflectance and absorption curves of Caribbean seawater and elements contained within it. Reflectance curves showed a predominant blue colour (400–500 nm) characteristic of Caribbean oligotrophic waters, conspicuous peaks result from the optical properties of chlorophyll a and seawater. Reflectance curves had a similar spectral response. This paper analyses reflectance spectra of surface seawater at 31 stations in the Caribbean Sea during the summer of 2001. 相似文献
58.
Broadband solar irradiance data obtained in the spectral range 400–940 nm at Kwangju, South Korea from 1999–2000 have been analyzed to investigate the effects of cloud cover and atmospheric optical depth on solar radiation components. Results from measurements indicate that the percentage of direct and diffuse horizontal components of solar irradiance depend largely on total optical depth (TOD) and cloud cover. During summer and spring, the percentages of diffuse solar irradiance relative to the global irradiance were 5.0% and 4.9% as compared to 2.2% and 3.0% during winter and autumn. The diffuse solar irradiance is higher than the direct in spring and summer by 24.2%, and 40.6%, respectively, which may largely be attributed to the attenuation (scattering) of radiation by heavy dust pollution and large cloud amount. In cloud-free conditions with cloud cover ≤2/10, the fraction of the direct and diffuse components were 66.0% and 34.0%, respectively, with a mean daily global irradiance value of 7.92±2.91 MJ m−2 day−1. However, under cloudy conditions (with cloud cover ≥8/10), the diffuse and direct fractions were 97.9% and 2.2% of the global component, respectively. The annual mean TOD under cloudless conditions (cloud cover≤2/10) yields 0.74±0.33 and increased to as much as 3.15±0.67 under cloudy conditions with cloud amount ≥8/10. An empirical formula is derived for estimating the diffuse and direct components of horizontal solar irradiance by considering the total atmospheric optical depth (TOD). Results from statistical models are shown for the estimation of solar irradiance components as a function of TOD with sufficient accuracy as indicated by low standard error for each solar zenith angle (SZA). 相似文献
59.
本文系统地分析国外几十年来用光学方法对海面微尺度波浪观测的研究方法和观测装置,从中比较各自的优缺点,对于今后在此方面的研究工作提供帮助。 相似文献
60.
南黄海浮游植物与水色透明度之间相关关系的研究 总被引:1,自引:0,他引:1
本文根据 1995 年 9 月在南黄海获取的资料,分析和讨论了该水域浮游植物现存量(叶绿素 a ( C H ))、初级生产力( P P) 和海水光学参数(透明度( S T))、水色( W C)) 之间的相关关系。分析结果表明,夏末秋初南黄海 C H 与 P P, C H 与 W C 和 P P 与 W C 以及悬浮物( S S) 与 W C 之间均有良好的正相关关系。相关式分别为: P P = 22519ln( C H ) + 48891 或 P P = 5 E- 05 C H 16464( R2 = 07037); W C = 403ln( C H ) + 89768 或 W C = 71306 C H 04747 ( R2 =07921); C H = 15437ln( S S) + 13647 或 C H = 07499 S S1252( R2 = 07223); P P =33286ln S S+ 15222 或 P P = 33029 S S05694 ( R2 = 05476); P P = 42588ln( W C) - 37071或 P P = 66512 W C08665( R2 = 06731) 以 及 S S = 14019ln( W C) - 13363 相似文献