全文获取类型
收费全文 | 6865篇 |
免费 | 899篇 |
国内免费 | 1222篇 |
专业分类
测绘学 | 556篇 |
大气科学 | 698篇 |
地球物理 | 1431篇 |
地质学 | 3197篇 |
海洋学 | 1079篇 |
天文学 | 889篇 |
综合类 | 290篇 |
自然地理 | 846篇 |
出版年
2024年 | 37篇 |
2023年 | 75篇 |
2022年 | 181篇 |
2021年 | 286篇 |
2020年 | 228篇 |
2019年 | 289篇 |
2018年 | 241篇 |
2017年 | 218篇 |
2016年 | 249篇 |
2015年 | 293篇 |
2014年 | 311篇 |
2013年 | 506篇 |
2012年 | 364篇 |
2011年 | 426篇 |
2010年 | 387篇 |
2009年 | 467篇 |
2008年 | 404篇 |
2007年 | 410篇 |
2006年 | 406篇 |
2005年 | 360篇 |
2004年 | 283篇 |
2003年 | 222篇 |
2002年 | 232篇 |
2001年 | 223篇 |
2000年 | 186篇 |
1999年 | 126篇 |
1998年 | 99篇 |
1997年 | 69篇 |
1996年 | 62篇 |
1995年 | 64篇 |
1994年 | 65篇 |
1993年 | 51篇 |
1992年 | 53篇 |
1991年 | 50篇 |
1990年 | 45篇 |
1989年 | 47篇 |
1988年 | 37篇 |
1987年 | 57篇 |
1986年 | 39篇 |
1985年 | 61篇 |
1984年 | 78篇 |
1983年 | 64篇 |
1982年 | 62篇 |
1981年 | 69篇 |
1980年 | 58篇 |
1979年 | 46篇 |
1978年 | 46篇 |
1977年 | 51篇 |
1976年 | 41篇 |
1975年 | 53篇 |
排序方式: 共有8986条查询结果,搜索用时 46 毫秒
11.
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
12.
13.
14.
山区公路软基病害研究 总被引:2,自引:0,他引:2
随着高等级公路建设规模的扩大,山区公路所面临的路基病害特别是软土路基病害问题也逐渐增多。结合对陕南勉(县)一宁(强)高速公路工程实例分析,对山区软土成因及其特性进行了初步分析,认为山区软土属以坡洪积、湖积和冲积为主的软土,也有少量是由坡残积物堆积而形成。山区软土的特殊性表现在成分的复杂性、分布的不均匀性、隐蔽性和物理力学性质的特殊性。根据其特性以及中国山区公路软基普遍存在的病害问题,总结了山区公路软基的主要病害类型为剪切拉裂破坏、浸水沉陷破坏、剥蚀坍塌破坏、推挤滑动破坏。还提出了相应的软基处理方法及建议。 相似文献
15.
16.
T.D. Thoroughgood V.S. Dhillon S.P. Littlefair T.R. Marsh D.A. Smith 《Monthly notices of the Royal Astronomical Society》2001,327(4):1323-1333
We present spectroscopy of the eclipsing recurrent nova U Sco. The radial velocity semi-amplitude of the primary star was found to be from the motion of the wings of the He ii λ 4686-Å emission line. By detecting weak absorption features from the secondary star, we find its radial velocity semi-amplitude to be . From these parameters, we obtain a mass of for the white dwarf primary star and a mass of for the secondary star. The radius of the secondary is calculated to be , confirming that it is evolved. The inclination of the system is calculated to be , consistent with the deep eclipse seen in the light-curves. The helium emission lines are double-peaked, with the blueshifted regions of the disc being eclipsed prior to the redshifted regions, clearly indicating the presence of an accretion disc. The high mass of the white dwarf is consistent with the thermonuclear runaway model of recurrent nova outbursts, and confirms that U Sco is the best Type Ia supernova progenitor currently known. We predict that U Sco is likely to explode within ∼700 000 yr. 相似文献
17.
Dryer M. Fry C.D. Sun W. Deehr C. Smith Z. Akasofu S.-I. Andrews M.D. 《Solar physics》2001,204(1-2):265-284
Prediction of solar-generated disturbances and their three-dimensional propagation through interplanetary space continues
to present a vitally important operational space weather forecasting objective. This paper presents the first successful real-time
prediction of a series of major heliospheric shock waves at Earth, including the one from the 14 July 2000 (`Bastille Day')
flare. An ensemble of three models and their predictions were distributed to a world-wide group of interested scientists as
part of an informal Internet space weather forecast research program. Two of the models, STOA (Shock Time of Arrival) and
ISPM (Interplanetary Shock Propagation Model), presently in operation by the US Air Force Weather Agency, provided predictions
of shock arrival time (SAT) that were, respectively, 0.5 hours after and 3.7 hours before the observed arrival. The third
model, HAFv.2 (Hakamada–Akasofu–Fry version 2.0) predicted a time 0.3 hours after the observed shock arrival time (14:37 UT,
15 July 2000). Of primary interest to this study is the third model, firstly in terms of its capability of propagating shocks
through non-uniform solar wind conditions, and secondly, in terms of its ability to integrate multiple solar events and display
them graphically along with the background solar wind. This latter capability was brought to bear on ten real-time-reported
flares, some with CMEs (coronal mass ejections) that took place as companions to the Bastille flare during the period 7–15
July 2000. Some limited statistics are given regarding the three models' shock arrival prediction capability at Earth, as
an extension of our earlier studies with this three model ensemble in the prediction of SAT. HAFv.2, however, was able to
describe not only the ten events and their interaction as measured at Earth, but also at the spacecraft NEAR (orbiting the
asteroid, Eros, at 1.8 AU), and CASSINI (en route, at 4.0 AU, to Saturn). Several important points are noted: (1) this epoch
represents a small statistical sample that should be expanded; and (2) the three models, based on theory, empiricism, and
simulations represent the state of the art that should presage a similar community process. This paper was presented earlier
as an Invited Talk at the American Geophysical Union Fall Meeting, December 14–19, 2000, in San Francisco, CA, U.S.A.toward
space weather objectives in the Sun-Earth domain.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1014200719867 相似文献
18.
19.
20.