全文获取类型
收费全文 | 37220篇 |
免费 | 601篇 |
国内免费 | 587篇 |
专业分类
测绘学 | 940篇 |
大气科学 | 3084篇 |
地球物理 | 7447篇 |
地质学 | 12289篇 |
海洋学 | 3374篇 |
天文学 | 8742篇 |
综合类 | 121篇 |
自然地理 | 2411篇 |
出版年
2021年 | 202篇 |
2020年 | 259篇 |
2019年 | 263篇 |
2018年 | 614篇 |
2017年 | 567篇 |
2016年 | 885篇 |
2015年 | 625篇 |
2014年 | 859篇 |
2013年 | 1890篇 |
2012年 | 1040篇 |
2011年 | 1453篇 |
2010年 | 1196篇 |
2009年 | 1782篇 |
2008年 | 1581篇 |
2007年 | 1496篇 |
2006年 | 1407篇 |
2005年 | 1290篇 |
2004年 | 1219篇 |
2003年 | 1174篇 |
2002年 | 1096篇 |
2001年 | 984篇 |
2000年 | 986篇 |
1999年 | 925篇 |
1998年 | 842篇 |
1997年 | 844篇 |
1996年 | 722篇 |
1995年 | 646篇 |
1994年 | 565篇 |
1993年 | 517篇 |
1992年 | 514篇 |
1991年 | 482篇 |
1990年 | 477篇 |
1989年 | 420篇 |
1988年 | 403篇 |
1987年 | 454篇 |
1986年 | 438篇 |
1985年 | 527篇 |
1984年 | 586篇 |
1983年 | 560篇 |
1982年 | 524篇 |
1981年 | 469篇 |
1980年 | 443篇 |
1979年 | 400篇 |
1978年 | 417篇 |
1977年 | 359篇 |
1976年 | 327篇 |
1975年 | 337篇 |
1974年 | 339篇 |
1973年 | 340篇 |
1972年 | 202篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
251.
M. M. Bisi A. R. Breen B. V. Jackson R. A. Fallows A. P. Walsh Z. Mikić P. Riley C. J. Owen A. Gonzalez-Esparza E. Aguilar-Rodriguez H. Morgan E. A. Jensen A. G. Wood M. J. Owens M. Tokumaru P. K. Manoharan I. V. Chashei A. S. Giunta J. A. Linker V. I. Shishov S. A. Tyul’bashev G. Agalya S. K. Glubokova M. S. Hamilton K. Fujiki P. P. Hick J. M. Clover B. Pintér 《Solar physics》2010,265(1-2):49-127
We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth’s magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time (Dst) index reaching ?263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation. 相似文献
252.
253.
Discontinuity controlled probabilistic slope failure risk maps of the Altindag (settlement) region in Turkey 总被引:7,自引:0,他引:7
The evaluation of potential rock slope problems using stereographic projection techniques known as kinematic analysis is one of the most important parts of a slope stability investigation to be carried out in jointed rock media. In conventional stereoprojection techniques for the assessment of possible rock slope failures, the peak orientations of joints together with the slope geometry and the friction angle of the weakness planes are used. Other possible joint orientations which may be encountered in the rock media are ignored, although they belong to the group of joint peak orientations. In this study, nearly vertical jointed andesites cropped out at the Altindag settlement region in Ankara were studied in order to evaluate the relevance of this ignored discontinuity orientation data on slope stability. As a result, probabilistic risk maps for planar, toppling and wedge failures were produced using the kinematic rules and digital elevation model of the study area. The comparison of the distribution of the actual failures in the area and the probabilistic risk maps prepared for the study area revealed that all of the identified failures are found to be located in the higher risk zones on the probabilistic risk maps. 相似文献
254.
Paul C. Sutton Andrew R. Goetz Stephen Fildes Clive Forster Tilottama Ghosh 《The Professional geographer》2013,65(1):119-133
This article explores the use of nighttime satellite imagery for mapping urban and peri-urban areas of Australia. A population-weighted measure of urban sprawl is used to characterize relative levels of sprawl for Australia's urban areas. In addition, the expansive areas of low light surrounding most major metropolitan areas are used to map the urban–bush interface of exurban land use. Our findings suggest that 82 percent of the Australian population lives in urban areas, 15 percent live in peri-urban or exurban areas, and 3 percent live in rural areas. This represents a significantly more concentrated human settlement pattern than presently exists in the United States. 相似文献
255.
256.
Philipp Tesch Robert S. Reece James R. Markello Juan Carlos Laya Michael C. Pope 《Basin Research》2020,32(2):388-401
We developed a seismic geomorphology-based procedure to enhance traditional trajectory analysis with the ability to visualize and quantify lateral variability along carbonate prograding-margin types (ramps and rimmed shelves) in 3D and 4D. This quantitative approach analysed the shelf break geometric evolution of the Oligo-Miocene carbonate clinoform system in the Browse Basin and delineated the feedback between antecedent topography and carbonate system response as controlling factor on shelf break rugosity. Our geometrical analysis identified a systematic shift in the large-scale average shelf break strike direction over a transect of 10 km from 62° to 55° in the Oligo-Miocene interval of the Browse Basin, which is likely controlled by far-field allogenic forcing from the Timor Trough collision zone. Plotting of 3D shelf break trajectories represents a convenient way to visualize the lateral variability in shelf break evolution. Shelf break trajectories that indicate contemporaneous along-strike progradation and retrogradation correlate with phases of autogenic slope system re-organization and may be a proxy for morphological stability of the shelf break. Shelf break rugosity and shelf break trajectory rugosity are not inherited parameters and antecedent topography does not dictate long-term differential movement of the shelf margin through successive depositional sequences. The autogenic carbonate system response to antecedent topography smooths high-rugosity areas by filling accommodation and maintains a relatively constant shelf break rugosity of ~150 m. Color-coding of the vertical component in the shelf break trajectory captures the creation and filling of accommodation, and highlights areas of the transect that are likely to yield inconsistent 2D sequence stratigraphic interpretations. 相似文献
257.
Determination of Stellar Parameters with GAIA 总被引:1,自引:0,他引:1
C.A.L. Bailer-Jones 《Astrophysics and Space Science》2002,280(1-2):21-29
The GAIA Galactic survey satellite will obtain photometry in 15 filters of over 109 stars in our Galaxy across a very wide range of stellar types. No other planned survey will provide so much photometric information
on so many stars. I examine the problem of how to determine fundamental physical parameters (T
eff, log g, [Fe/H] etc.) from these data. Given the size, multidimensionality and diversity of this dataset, this is a challenging task
beyond any encountered so far in large-scale stellar parametrization. I describe the problems faced (initial object identification,
interstellar extinction, multiplicity, missing data etc.) and present a framework in which they can be addressed. A probabilistic
approach is advocated on the grounds that it can take advantage of additional information (e.g. priors and data uncertainties)
in a consistent and useful manner, as well as give meaningful results in the presence of poor or degenerate data. Furthermore,
I suggest an approach to parametrization which can use the other information GAIA will acquire, in particular the parallax,
which has not previously been available for large-scale multidimensional parametrization. Several of the problems identified
and ideas suggested will be relevant to other large surveys, such as SDSS, DIVA,FAME, VISTA and LSST, as well as stellar parametrization
in a virtual observatory.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
258.
河北平原水系密度与隐伏活动构造的关系 总被引:4,自引:1,他引:4
以1926年出版的比例尺为1:5万的顺直地形图作为基础图件,用地理信息系统技术对河北平原作水系密度计量分析,揭示隐伏在第四纪巨厚的沉积物之下活动构造的信息,研究结果证实水系线密度统计图与使用其它地球科学方法获得的成果,例如基底活动断块图,地貌类型图和第四纪厚度图都有很好的对应,特别与布格重力图对应更好,研究结果发现水系密度图与布格重力异常图在总体一致性较好的前提下,多处反向异常区均为近代强震发生的区域,提出这种地表水系密度统计研究的成果不仅可以揭示深部隐伏的活动构造,而且具有较明确的时间含义。 相似文献
259.
Summary Future research directions for agricultural geography were the subject of debate in Area in the late 1980s, and the subsequent application of political economy ideas undoubtedly revived interest in agricultural research. This paper argues that agricultural geography contains greater diversity than the dominant political economy discourse would suggest. It reviews 'other' areas of agricultural research such as policy, post- productivism, people, culture and animals, presenting future suggestions which should ensure that agricultural research continues revitalized rather than redundant into the next millennium. 相似文献
260.