全文获取类型
收费全文 | 1707篇 |
免费 | 150篇 |
国内免费 | 401篇 |
专业分类
测绘学 | 63篇 |
大气科学 | 117篇 |
地球物理 | 215篇 |
地质学 | 1016篇 |
海洋学 | 232篇 |
天文学 | 497篇 |
综合类 | 47篇 |
自然地理 | 71篇 |
出版年
2024年 | 10篇 |
2023年 | 19篇 |
2022年 | 30篇 |
2021年 | 36篇 |
2020年 | 46篇 |
2019年 | 57篇 |
2018年 | 27篇 |
2017年 | 39篇 |
2016年 | 48篇 |
2015年 | 60篇 |
2014年 | 60篇 |
2013年 | 59篇 |
2012年 | 58篇 |
2011年 | 87篇 |
2010年 | 101篇 |
2009年 | 127篇 |
2008年 | 112篇 |
2007年 | 128篇 |
2006年 | 149篇 |
2005年 | 109篇 |
2004年 | 114篇 |
2003年 | 106篇 |
2002年 | 77篇 |
2001年 | 86篇 |
2000年 | 74篇 |
1999年 | 57篇 |
1998年 | 52篇 |
1997年 | 45篇 |
1996年 | 43篇 |
1995年 | 33篇 |
1994年 | 17篇 |
1993年 | 34篇 |
1992年 | 22篇 |
1991年 | 30篇 |
1990年 | 26篇 |
1989年 | 17篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
排序方式: 共有2258条查询结果,搜索用时 640 毫秒
11.
12.
本文作者首次发现了EXO 2030+375的回旋吸收线迹象.这是迄今唯一一个同时有用回旋吸收线直接测量的磁场数据和用吸积演化方法间接测量的中子星磁矩数据的X射线脉冲星.两种测量方法的结果有很大差别,本文提出了可能导致这种差别的物理机制. 相似文献
13.
L. I. Matveenko 《Astronomy Letters》2001,27(11):686-690
The core (injector) and the jet (relativistic plasma outflow) of AGN objects are surrounded by an ionized medium, an H II region observed in emission lines. The synchrotron radiation from the core and the jet is observed through a thin screen that cocoons the structure under consideration. The screen transparency depends on wavelength and distance from the injector. We consider the objects 3C 345 and 1803+784 whose core emission at decimeter wavelengths is absorption by more than 25 dB. The visible bright compact component is the bright nearby portion of the jet that extends outside the dense part of the screen. We explore the possibility of measuring the screen transparency from absorption in Hα recombination lines with different quantum numbers at centimeter wavelengths. 相似文献
14.
Jeremy Allington-Smith Graham Murray Robert Content George Dodsworth Bryan W. Miller James Turner Inger Jorgensen Isobel Hook 《Experimental Astronomy》2002,13(1):1-37
We describe the integral field unit (IFU) which converts the Gemini Multiobject Spectrograph (GMOS) installed on the Gemini-North telescope to an integral field spectrograph,which produces spectra over a contiguous field of view of 7 × 5 arcsec with spatial sampling of 0.2 arcsecover the wavelength range 0.4-1.0 μm.GMOS is converted to this mode by the remote insertion of the IFU into thebeam in place of the masks used for the multiobject mode. A separate fieldof half the area of the main field, but otherwise identical, is alsoprovided to improve background subtraction. The IFU contains 1500lenslet-coupled fibres and was the first facility of any type for integralfield spectroscopy employed on an 8/10 m telescope.We describe the design, construction and testing of the GMOS IFU and present measurements of the throughput both in the laboratory and at the telescope. We compare these with a theoretical prediction made before construction started. All are in good agreement with each other, with the on-telescope throughput exceeding 60% (averaged over wavelength). Finallywe show an example of data obtained during commissioning to illustrate the power of the device. 相似文献
15.
Martin M. Roth Thomas Fechner Dieter Wolter Andreas Kelz Thomas Becker 《Experimental Astronomy》2002,14(2):99-105
PMAS, the Potsdam Multi-Aperture Spectrophotometer, is a new integral field spectrograph in the optical, which is optimized
for good transmission and high image quality from 350 nm to 1 μm. We present our plan to implement a CCD charge-shuffle mode
to allow for beam switching with a very high degree of sky subtraction accuracy for faint object 3-D spectroscopy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
介绍一种自行设计和加工的直接雾化石墨炉进样装置的结构、工作原理和操作方法。该装置由微机控制与石墨炉加热程序同步工作,可以实现自动控制和自动测量。对雾化进样石墨炉分析的仪器参数和实验条件进行了研究和选择。结果表明,该装置与石墨炉结合具有自动化程度高、重现性好、样品利用率高和分析速度快等特点。 相似文献
17.
18.
19.
M. T. Murphy S. J. Curran J. K. Webb 《Monthly notices of the Royal Astronomical Society》2003,342(3):830-836
We describe initial results of a search for redshifted molecular absorption towards four millimetre-loud, optically faint quasars. A wide frequency bandwidth of up to 23 GHz per quasar was scanned using the Swedish–ESO Submillimetre Telescope at La Silla. Using a search list of commonly detected molecules, we obtained nearly complete redshift coverage up to z abs = 5 . The sensitivity of our data is adequate to have revealed absorption systems with characteristics similar to those seen in the four known redshifted millimetre-band absorption systems, but none were found. Our frequency-scan technique nevertheless demonstrates the value of wide-band correlator instruments for searches such as these. We suggest that a somewhat larger sample of similar observations should lead to the discovery of new millimetre-band absorption systems. 相似文献
20.