首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4838篇
  免费   165篇
  国内免费   103篇
测绘学   109篇
大气科学   558篇
地球物理   1120篇
地质学   1522篇
海洋学   786篇
天文学   640篇
综合类   46篇
自然地理   325篇
  2022年   30篇
  2021年   55篇
  2020年   62篇
  2019年   93篇
  2018年   175篇
  2017年   157篇
  2016年   178篇
  2015年   123篇
  2014年   227篇
  2013年   328篇
  2012年   205篇
  2011年   281篇
  2010年   244篇
  2009年   248篇
  2008年   233篇
  2007年   234篇
  2006年   197篇
  2005年   176篇
  2004年   179篇
  2003年   146篇
  2002年   144篇
  2001年   108篇
  2000年   109篇
  1999年   78篇
  1998年   64篇
  1997年   53篇
  1996年   40篇
  1995年   55篇
  1994年   33篇
  1993年   32篇
  1992年   38篇
  1991年   31篇
  1990年   32篇
  1989年   26篇
  1988年   34篇
  1987年   43篇
  1986年   36篇
  1985年   46篇
  1984年   54篇
  1983年   57篇
  1982年   40篇
  1981年   40篇
  1980年   49篇
  1979年   38篇
  1978年   35篇
  1977年   40篇
  1975年   24篇
  1973年   24篇
  1972年   19篇
  1971年   20篇
排序方式: 共有5106条查询结果,搜索用时 15 毫秒
1.
ABSTRACT

Land-Use Mix (LUM) refers to the strategy of integrating complementary functions within a building or area. While LUM has become a dominant approach in urban planning, its actual benefits and vision for spatial planning remain unclear. To clarify this issue, this study discerns the spatial features of land-use patterns depending on the compatibilities among land-use categories. Accordingly, this study introduces three LUM measures – adjacency, intensity, and proximity – to identify differences in the spatial distribution of land-use categories. Based on these measures, a land-use allocation model is developed to specify spatial patterns satisfying the given compatibilities. This model is tested by applying the concept of the neighborhood unit on a case study of normative land-use patterns subject to specified compatibilities. The results describe spatial features of four compatibility sets, including a set exhibiting a compatibility conflict between the same land-use pair and LUM measures when, for example, a given land-use pair is compatible in terms of intensity but incompatible in terms of proximity. Understanding the spatial features of a normative land-use pattern that satisfies various possible compatibilities will facilitate the incorporation of the LUM approach into local planning guidance and zoning ordinances.  相似文献   
2.
3.
4.
Carcedo  L.  Brown  D.S.  Hood  A.W.  Neukirch  T.  Wiegelmann  T. 《Solar physics》2003,218(1-2):29-40
Many authors use magnetic-field models to extrapolate the field in the solar corona from magnetic data in the photosphere. The accuracy of such extrapolations is usually judged qualitatively by eye, where a less judgemental quantitative approach would be more desirable. In this paper, a robust method for obtaining the best fit between a theoretical magnetic field and intensity observations of coronal loops on the solar disk will be presented. The method will be applied to Yohkoh data using a linear force-free field as an illustration. Any other theoretical model for the magnetic field can be used, provided there is enough freedom in the model to optimize the fit.  相似文献   
5.
The D-CIXS Compact X-ray Spectrometer will provide high quality spectroscopic mapping of the Moon, the primary science target of the ESA SMART-1 mission. D-CIXS consists of a high throughput spectrometer, which will perform spatially localised X-ray fluorescence spectroscopy. It will also carry a solar monitor, to provide the direct calibration needed to produce a global map of absolute lunar elemental abundances, the first time this has been done. Thus it will achieve ground breaking science within a resource envelope far smaller than previously thought possible for this type of instrument, by exploiting two new technologies, swept charge devices and micro-structure collimators. The new technology does not require cold running, with its associated overheads to the spacecraft. At the same time it will demonstrate a radically novel approach to building a type of instrument essential for the BepiColombo mission and potential future planetary science targets.  相似文献   
6.
7.
It is shown how the hard X-ray burst count rate and itse-folding ime can be used to estimate the minimum magnetic fieldB min required in a flare magnetic reconnection site for the burst to be interpreted in terms of a thick target model. Application of the method to data from the Solar Maximum Mission (HXRBS) indicates absolute minimum fields well in excess of 100 G, and impossibly high values for some reconnection geometries.  相似文献   
8.
This paper presents a method that incorporates a non‐associated flow rule into the limit analysis to investigate the influence of the dilatancy angle on the factor of safety for the slope stability analysis. The proposed method retain's the advantage of the upper bound method, which is simple and has no stress involvement in the calculation of the energy dissipation and the factor of safety. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号