全文获取类型
收费全文 | 163089篇 |
免费 | 2816篇 |
国内免费 | 2071篇 |
专业分类
测绘学 | 4773篇 |
大气科学 | 12120篇 |
地球物理 | 32853篇 |
地质学 | 60289篇 |
海洋学 | 13231篇 |
天文学 | 32285篇 |
综合类 | 2466篇 |
自然地理 | 9959篇 |
出版年
2021年 | 1081篇 |
2020年 | 1313篇 |
2019年 | 1364篇 |
2018年 | 8050篇 |
2017年 | 7349篇 |
2016年 | 6390篇 |
2015年 | 2465篇 |
2014年 | 3599篇 |
2013年 | 6976篇 |
2012年 | 5011篇 |
2011年 | 8577篇 |
2010年 | 7404篇 |
2009年 | 9037篇 |
2008年 | 7912篇 |
2007年 | 8265篇 |
2006年 | 5099篇 |
2005年 | 4543篇 |
2004年 | 4637篇 |
2003年 | 4403篇 |
2002年 | 3938篇 |
2001年 | 3344篇 |
2000年 | 3264篇 |
1999年 | 2644篇 |
1998年 | 2712篇 |
1997年 | 2622篇 |
1996年 | 2237篇 |
1995年 | 2192篇 |
1994年 | 1995篇 |
1993年 | 1809篇 |
1992年 | 1753篇 |
1991年 | 1605篇 |
1990年 | 1799篇 |
1989年 | 1575篇 |
1988年 | 1440篇 |
1987年 | 1733篇 |
1986年 | 1492篇 |
1985年 | 1911篇 |
1984年 | 2077篇 |
1983年 | 1990篇 |
1982年 | 1872篇 |
1981年 | 1730篇 |
1980年 | 1600篇 |
1979年 | 1447篇 |
1978年 | 1501篇 |
1977年 | 1374篇 |
1976年 | 1303篇 |
1975年 | 1233篇 |
1974年 | 1231篇 |
1973年 | 1226篇 |
1972年 | 791篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
192.
193.
B. Ahmed G. J. Alner H. Araujo J. C. Barton A. Bewick M. J. Carson D. Davidge J. V. Dawson T. Gamble S. P. Hart R. Hollingworth A. S. Howard W. G. Jones M. K. Joshi V. A. Kudryavtsev T. B. Lawson V. Lebedenko M. J. Lehner J. D. Lewin P. K. Lightfoot I. Liubarsky R. Lüscher J. E. McMillan B. Morgan G. Nicklin S. M. Paling R. M. Preece J. J. Quenby J. W. Roberts M. Robinson N. J. T. Smith P. F. Smith N. J. C. Spooner T. J. Sumner D. R. Tovey 《Astroparticle Physics》2003,19(6):691-702
The NAIAD experiment (NaI Advanced Detector) for weakly interacting massive particle (WIMP) dark matter searches at Boulby mine (UK) is described. The detector consists of an array of encapsulated and unencapsulated NaI(Tl) crystals with high light yield. Six crystals are collecting data at present. Data accumulated by four of them (10.6 kg × year exposure) have been used to set upper limits on the WIMP–nucleon spin-independent and WIMP–proton spin-dependent cross-sections. Pulse shape analysis has been applied to discriminate between nuclear recoils, as may be caused by WIMP interactions, and electron recoils due to gamma background. Various calibrations of crystals are presented. 相似文献
194.
195.
W.M. Napier 《Astrophysics and Space Science》2003,285(2):419-427
Claims that ordinary spiral galaxies and some classes of QSO show periodicity in their redshift distributions are investigated
using recent high-precision data and rigorous statistical procedures. The claims are broadly upheld. The periodicites are
strong and easily seen by eye in the datasets. Observational, reduction or statistical artefacts do not seem capable of accounting
for them.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
196.
197.
Dirk Pandel France A. Córdova Steve B. Howell 《Monthly notices of the Royal Astronomical Society》2003,346(4):1231-1241
We present an analysis of X-ray and ultraviolet (UV) data of the dwarf nova VW Hyi that were obtained with XMM–Newton during the quiescent state. The X-ray spectrum indicates the presence of an optically thin plasma in the boundary layer that cools as it settles on to the white dwarf. The plasma has a continuous temperature distribution that is well described by a power law or a cooling flow model with a maximum temperature of 6–8 keV. We estimate from the X-ray spectrum a boundary layer luminosity of 8 × 1030 erg s-1 , which is only 20 per cent of the disc luminosity. The rate of accretion on to the white dwarf is 5 × 10−12 M⊙ yr−1 , about half of the rate in the disc. From the high-resolution X-ray spectra, we estimate that the X-ray emitting part of the boundary layer is rotating with a velocity of 540 km s−1 , which is close to the rotation velocity of the white dwarf but is significantly smaller than the Keplerian velocity. We detect a 60-s quasi-periodic oscillation of the X-ray flux, which is likely to be due to the rotation of the boundary layer. The X-ray and the UV flux show strong variability on a time-scale of ∼1500 s. We find that the variability in the two bands is correlated and that the X-ray fluctuations are delayed by ∼100 s. The correlation indicates that the variable UV flux is emitted near the transition region between the disc and the boundary layer and that accretion rate fluctuations in this region are propagated to the X-ray emitting part of the boundary layer within ∼100 s. An orbital modulation of the X-ray flux suggests that the inner accretion disc is tilted with respect to the orbital plane. The elemental abundances in the boundary layer are close to their solar values. 相似文献
198.
J. Dommanget 《Journal of Astrophysics and Astronomy》2003,24(3-4):99-109
A research that we conducted in 1963 on the evolution of the binaries based on the available orbital data to obtain a philosophical
degree, led to the establishment of an interesting and new diagram between the logarithm of the total mass and a particular
parameterX, bound to the areal constant. This appeared to have a real physical significance but the basic observational material was
insufficiently extended to assure its undeniable existence. In 1981, a new research based on a more extended orbital material,
has confirmed this diagram. Presently, another important increase in the orbital material and the availability of highly accurate
trigonometric parallaxes produced by the Hipparcos satellite, gave us the opportunity to confirm once more the stability of
this diagram. This last research is here described. 相似文献
199.
JINFeng-jun 《中国地理科学(英文版)》2003,13(2):97-103
It is very important to establish cooperative mechanism to guarantee all members to develop their e-conomies in the Yellow Sea Rim. In this paper, the development strategies ofshipplng centers and transportation networkare discussed based on economic giobalization tendency. The results argue that a united transportation network should bebuilt in order to promote the economic competition of Northeast Asia in the world. As a key component of the economiccooperation, a hierarchical shipping centers network should be established with Hong Kong, Shanghai, Pusan, Koho,and Tokyo as cores. The authorities of China, Japan, R. O. Korea and D. P. B. Korea should make more efforts tobuild a set of cooperation institutions based on raising the transportation efficiency. 相似文献
200.
MENGLi-li 《中国地理科学(英文版)》2003,13(2):190-192
The exploitation and utilization of the tour resources of tournament athletics, including skiling, boat sail-ing, archery, ice engraving, snow engraving, has become a new trend of the development of Chinese tourism. Due tothe unique cold climate and superior geographic location, Harbin is a promising city for developing tour resources of tourna-ment athletics. Based on the analysis of the superiority and peculiarity of Harbin, the speculation on development of tour resources of tournament athletics in Harbin is proposed as follows : 1 ) Harbin should develop its special tour resources of tournament athletics associated with needs of market; 2) Harbin should take the advantages of rich resources and devel-op ice and snow entertainment in winter and travel for sight-seeing and spending summer;, 3) the adjustment of the layoutof ice and snow resources should be based on the idea of taking Harbin as the center and all-side opening at the largescale in the way of radiation; 4) tourism should be developed by the combined efforts of various departments to make feasi-ble plan, and the organizers should pay much attention to ensuring the safetv of tourists. 相似文献