全文获取类型
收费全文 | 767篇 |
免费 | 14篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 62篇 |
大气科学 | 31篇 |
地球物理 | 132篇 |
地质学 | 313篇 |
海洋学 | 24篇 |
天文学 | 191篇 |
综合类 | 7篇 |
自然地理 | 27篇 |
出版年
2023年 | 2篇 |
2022年 | 9篇 |
2021年 | 20篇 |
2020年 | 15篇 |
2019年 | 7篇 |
2018年 | 57篇 |
2017年 | 42篇 |
2016年 | 51篇 |
2015年 | 27篇 |
2014年 | 25篇 |
2013年 | 48篇 |
2012年 | 28篇 |
2011年 | 34篇 |
2010年 | 29篇 |
2009年 | 36篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 16篇 |
2005年 | 12篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1972年 | 3篇 |
1971年 | 9篇 |
1970年 | 2篇 |
排序方式: 共有787条查询结果,搜索用时 15 毫秒
1.
2.
Hriday Mani Kalita Das Rajdeep Hajong Atul Kumar Neeraj Kharnaior Donly Dkhar Heart Casingh 《Water Resources》2019,46(6):934-943
Water Resources - This paper reports a series of experimental studies done to simulate the flow behavior over crump and ogee type of weirs. The transition of subcritical to supercritical flow, as... 相似文献
3.
Astrophysics - We used modified holographic Ricci dark energy to find anisotropic LRS Bianchi type I cosmological model in five-dimensions based on Lyra geometry. The exact solutions of the... 相似文献
4.
Ayesha Anjum Mousumi Das Jayant Murthy S. B. Gudennavar Rajesh Gopal S. G. Bubbly 《Journal of Astrophysics and Astronomy》2018,39(5):61
We have classified a sample of 37,492 objects from SDSS into QSOs, galaxies and stars using photometric data over five wave bands (u, g, r, i and z) and UV GALEX data over two wave bands (near-UV and far-UV) based on a template fitting method. The advantage of this method of classification is that it does not require any spectroscopic data and hence the objects for which spectroscopic data is not available can also be studied using this technique. In this study, we have found that our method is consistent by spectroscopic methods given that their UV information is available. Our study shows that the UV colours are especially important for separating quasars and stars, as well as spiral and starburst galaxies. Thus it is evident that the UV bands play a crucial role in the classification and characterization of astronomical objects that emit over a wide range of wavelengths, but especially for those that are bright at UV. We have achieved the efficiency of 89% for the QSOs, 63% for the galaxies and 84% for the stars. This classification is also found to be in agreement with the emission line diagnostic diagrams. 相似文献
5.
Das Ratul 《Water Resources》2020,47(2):222-230
Water Resources - Sediment mobility in stream corroborates many significant mechanisms in terms of interactions of transported particles in the carrier fluid flows. In general, the sediment... 相似文献
6.
T. Roy Choudhury Kanan Datta Suman Majumdar Raghunath Ghara Aseem Paranjape Rajesh Mondal Somnath Bharadwaj Saumyadip Samui 《Journal of Astrophysics and Astronomy》2016,37(4):29
Studying the cosmic dawn and the epoch of reionization through the redshifted 21-cm line are among the major science goals of the SKA1. Their significance lies in the fact that they are closely related to the very first stars in the Universe. Interpreting the upcoming data would require detailed modelling of the relevant physical processes. In this article, we focus on the theoretical models of reionization that have been worked out by various groups working in India with the upcoming SKA in mind. These models include purely analytical and semi-numerical calculations as well as fully numerical radiative transfer simulations. The predictions of the 21-cm signal from these models would be useful in constraining the properties of the early galaxies using the SKA data. 相似文献
7.
Kanan K. Datta Raghunath Ghara Suman Majumdar T. Roy Choudhury Somnath Bharadwaj Himadri Roy Abhirup Datta 《Journal of Astrophysics and Astronomy》2016,37(4):27
Detection of individual luminous sources during the reionization epoch and cosmic dawn through their signatures in the HI 21-cm signal is one of the direct approaches to probe the epoch. Here, we summarize our previous works on this and present preliminary results on the prospects of detecting such sources using the SKA1-low experiment. We first discuss the expected HI 21-cm signal around luminous sources at different stages of reionization and cosmic dawn. We then introduce two visibility based estimators for detecting such signals: one based on the matched filtering technique and the other relies on simply combing the visibility signal from different baselines and frequency channels. We find that the SKA1-low should be able to detect ionized bubbles of radius \(R_{\mathrm {b}} \gtrsim 10\) Mpc with ~100 h of observations at redshift z~8 provided that the mean outside neutral hydrogen fraction \(\mathrm {x}_{\text {HI}} \gtrsim 0.5\). We also investigate the possibility of detecting HII regions around known bright QSOs such as around ULASJ1120+0641 discovered by Mortlock et al. (Nature 474, 7353 (2011)). We find that a 5σ detection is possible with 600 h of SKA1-low observations if the QSO age and the outside xHI are at least ~2×107 Myr and ~0.2 respectively. Finally, we investigate the possibility of detecting the very first X-ray and Ly- α sources during the cosmic dawn. We consider mini-QSOs like sources which emits in X-ray frequency band. We find that with a total ~ 1000 h of observations, SKA1-low should be able to detect those sources individually with a ~ 9σ significance at redshift z=15. We summarize how the SNR changes with various parameters related to the source properties. 相似文献
8.
P. Kharb D. V. Lal V. Singh J. Bagchi C. H. Ishwara Chandra A. Hota C. Konar Y. Wadadekar P. Shastri M. Das K. Baliyan B. B. Nath M. Pandey-Pommier 《Journal of Astrophysics and Astronomy》2016,37(4):34
We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted. 相似文献
9.
10.
Suman?MajumdarEmail authorView authors OrcID profile Kanan?K.?Datta Raghunath?Ghara Rajesh?Mondal T.?Roy?Choudhury Somnath?Bharadwaj Sk.?Saiyad?Ali Abhirup?Datta 《Journal of Astrophysics and Astronomy》2016,37(4):32
The line-of-sight direction in the redshifted 21-cm signal coming from the cosmic dawn and the epoch of reionization is quite unique in many ways compared to any other cosmological signal. Different unique effects, such as the evolution history of the signal, non-linear peculiar velocities of the matter etc. will imprint their signature along the line-of-sight axis of the observed signal. One of the major goals of the future SKA-LOW radio interferometer is to observe the cosmic dawn and the epoch of reionization through this 21-cm signal. It is thus important to understand how these various effects affect the signal for its actual detection and proper interpretation. For more than one and half decades, various groups in India have been actively trying to understand and quantify the different line-of-sight effects that are present in this signal through analytical models and simulations. In many ways the importance of this sub-field under 21-cm cosmology have been identified, highlighted and pushed forward by the Indian community. In this article, we briefly describe their contribution and implication of these effects in the context of the future surveys of the cosmic dawn and the epoch of reionization that will be conducted by the SKA-LOW. 相似文献