全文获取类型
收费全文 | 7505篇 |
免费 | 420篇 |
国内免费 | 52篇 |
专业分类
测绘学 | 200篇 |
大气科学 | 768篇 |
地球物理 | 1989篇 |
地质学 | 2938篇 |
海洋学 | 472篇 |
天文学 | 1241篇 |
综合类 | 36篇 |
自然地理 | 333篇 |
出版年
2024年 | 23篇 |
2023年 | 40篇 |
2022年 | 58篇 |
2021年 | 150篇 |
2020年 | 162篇 |
2019年 | 134篇 |
2018年 | 339篇 |
2017年 | 362篇 |
2016年 | 465篇 |
2015年 | 330篇 |
2014年 | 398篇 |
2013年 | 569篇 |
2012年 | 463篇 |
2011年 | 459篇 |
2010年 | 404篇 |
2009年 | 448篇 |
2008年 | 326篇 |
2007年 | 252篇 |
2006年 | 249篇 |
2005年 | 194篇 |
2004年 | 216篇 |
2003年 | 164篇 |
2002年 | 159篇 |
2001年 | 123篇 |
2000年 | 104篇 |
1999年 | 94篇 |
1998年 | 93篇 |
1997年 | 104篇 |
1996年 | 63篇 |
1995年 | 78篇 |
1994年 | 77篇 |
1993年 | 48篇 |
1992年 | 32篇 |
1991年 | 45篇 |
1990年 | 64篇 |
1989年 | 31篇 |
1988年 | 24篇 |
1987年 | 45篇 |
1986年 | 35篇 |
1985年 | 36篇 |
1984年 | 44篇 |
1983年 | 33篇 |
1982年 | 35篇 |
1981年 | 44篇 |
1980年 | 21篇 |
1979年 | 27篇 |
1978年 | 20篇 |
1977年 | 24篇 |
1974年 | 19篇 |
1973年 | 22篇 |
排序方式: 共有7977条查询结果,搜索用时 14 毫秒
961.
962.
Robert A. Watson Pedro Carreira Kieran Cleary Rod D. Davies Richard J. Davis Clive Dickinson Keith Grainge † Carlos M. Gutiérrez Michael P. Hobson Michael E. Jones Rüdiger Kneissl Anthony Lasenby Klaus Maisinger Guy G. Pooley Rafael Rebolo José Alberto Rubiño-Martin ‡ Ben Rusholme § Richard D. E. Saunders Richard Savage Paul F. Scott Ane Slosar Pedro J. Sosa Molina Angela C. Taylor David Titterington Elizabeth Waldram Althea Wilkinson 《Monthly notices of the Royal Astronomical Society》2003,341(4):1057-1065
963.
Statistical Analysis of the Fluctuations Detected in High-Altitude Neutron Monitor,Solar and Interplanetary Parameters 总被引:1,自引:0,他引:1
Galactic cosmic ray fluctuations from six mountain altitude neutron monitors around the world are analyzed during the period 1990–1999. The period comprises the maximum and declining phase of solar cycle 22 and the beginning of cycle 23. The evolution of the most significant periodicities and comparisons with solar activity and interplanetary indicators are presented. We found a 38-day variation present in all neutron monitors, solar activity parameters, and IMF fluctuations. The possible origin of this and other stable periodicities of cosmic ray variations in the analyzed period are discussed. 相似文献
964.
We present a study at HST-like spatial resolution of the gas kinematics in the innermost part of NGC 1068. This work is based
on observations with the integral field spectrograph TIGER mounted on the CFH Telescope. We first derived the final spatial
PSF of our data and checked its photometric integrity by comparison with two independent [OIII] HST images (FOC and WFPC2).
We then performed a spatial deconvolution of the data-cube constraining the sum of the deconvolved velocity-slices to be as
close as possible to the HST image. The resulting deconvolved data-cube has then a resolution similar to the HST image. It
shows that the velocity distribution of the inner clouds detected with the HST differs strongly from a simple NE-SW ejection
flow. We thus show that the previous interpretations of the double-peaked lines NE of the nucleus must be revisited.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
965.
P. Kakaletris X. Moussas R. Pérez-enriquez D. Psarros 《Astrophysics and Space Science》1982,84(2):485-493
An analysis of the interplanetary medium structure is made during STIP 1. (September–October, 1975). Using a simple extrapolation method a reconstruction of the stream lines is made which shows that the interplanetary space during this time period was very quiet. Such a behaviour is expected because this interval is close to the minimum of the solar cycle activity.The evolution of two fast solar wind streams, which dominated the interplanetary medium for very long time periods, is studied.A peculiar solar proton event, with onset time before the optical flare, is explained according to Elliot mechanism — i.e., that energetic particles are stored for a long time and released, sometimes, before the optical flare.These particles can be seen only when the interplanetary medium is very quiet, (without shock waves) and the flare very isolated. 相似文献
966.
This all-sky catalogue of unambiguous rotation measure (from a Faraday-thin, one-component, spectrum selection) for 674 galaxies or quasars has been compiled, ordered, and edited from the available literature. All the known applications of the RM distribution toward foreground objects in the Galaxy (i.e., magnetic field in 4 nearby spiral arms and in 4 nearby interstellar magnetic bubbles) have also been catalogued. 相似文献
967.
Further photometric and spectroscopic observations of a chain of galaxies in Centaurus are presented and discussed. 相似文献
968.
Described here is a preliminary and tentative application of a method for fine-classification of stars, selected for studies
of galactic structure. The present investigation is based on about 100 stars within the approximate spectral type range B6-A5,
for which both spectra andUBV photometry have been obtained.
The motivation of the project is the following: For the study of galactic fine-structure it is essential to use as many members
as possible of stellar agglomerations of various type for a statistical treatment of the material. A-type stars are fairly
numerous and reasonably bright, but if all chemically peculiar stars, fast rotators or multiple systems have to be omitted
there is generally too little left for a relevant investigation. Here we perform some experiments in order to find a method
for fine-classification of A stars, both normal and chemically peculiar, within the framework of the M K system.
In this connection it is desirable to reduce the present multitude of CP classifications to a manageable number. It is shown
here that, independenttly of the definition of the degree of peculiarity, there is no sharp borderline separating the CP stars
from the ‘normal’ ones.
Also it is found that spectral classification can on an average be performed with almost the same accuracy for CP stars as
for the ‘normal’ ones provided cases of extreme peculiarity are avoided.
Based on observations collected at European Southern Observatory, La Silla, Chile. 相似文献
969.
970.
Beatriz García Carlos Hernández Stella Malaroda Nidia Morrell Hugo Levato 《Astrophysics and Space Science》1988,148(1):163-173
We determined radial velocities for 25 probable members of the open cluster IC 2602. We identified the stars with variable radial velocity. We improved the orbit of HD 93030, and computed a preliminary orbit for another spectroscopic binary. We discussed with such data the average cluster radial velocity and we compare the incidence of short period binaries among the Main-Sequence members of IC 2602 with the incidence for other clusters with different values of the average axial rotation of their members.Cerro Tololo Interamerican Observatory operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 相似文献