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   481篇
  免费   13篇
  国内免费   2篇
测绘学   10篇
大气科学   58篇
地球物理   74篇
地质学   167篇
海洋学   47篇
天文学   105篇
综合类   2篇
自然地理   33篇
  2024年   2篇
  2022年   3篇
  2019年   5篇
  2018年   7篇
  2017年   11篇
  2016年   10篇
  2015年   15篇
  2014年   10篇
  2013年   19篇
  2012年   13篇
  2011年   9篇
  2010年   15篇
  2009年   20篇
  2008年   24篇
  2007年   23篇
  2006年   19篇
  2005年   15篇
  2004年   31篇
  2003年   10篇
  2002年   13篇
  2001年   12篇
  2000年   15篇
  1999年   6篇
  1998年   5篇
  1997年   10篇
  1996年   5篇
  1995年   9篇
  1994年   8篇
  1993年   7篇
  1992年   5篇
  1991年   6篇
  1990年   5篇
  1989年   11篇
  1988年   10篇
  1987年   11篇
  1986年   10篇
  1985年   12篇
  1984年   8篇
  1983年   8篇
  1982年   11篇
  1981年   8篇
  1980年   4篇
  1977年   3篇
  1976年   6篇
  1975年   11篇
  1972年   2篇
  1971年   3篇
  1956年   2篇
  1955年   2篇
  1935年   1篇
排序方式: 共有496条查询结果,搜索用时 31 毫秒
461.
The drying-induced deformation behaviour of Opalinus Clay and tuff, which are being investigated under international and local collaborative projects for nuclear waste disposal in Switzerland and Japan, was investigated under a no-stress condition in the laboratory to evaluate their generic susceptibility to the formation of excavation damaged zone. The cylindrical core samples of Opalinus Clay and tuff were prepared to a one-dimensional drying condition and submitted to an uncontrolled laboratory environment. The strain evolution, evaporative water loss and environmental entities, such as temperature and relative humidity, were recorded simultaneously and quasi-continuously. It was observed that the drying phase induced significant strain magnitude and damage in Opalinus Clay samples, which was evidenced by the formation of hairy cracks on the surface parallel to the bedding. On the contrary, the strain occurrences in tuff samples were relatively insignificant, and no tendency of cracking was observed. In addition, the quasi-continuous availability of volumetric strains was further used in poroelastic relation for the estimation of capillary suction evolution. The calculated results were validated with pore size distributions obtained from mercury intrusion porosimetry.  相似文献   
462.
It is well known that magnetic activity in late‐type stars increases with increasing rotation rate. Using inversion techniques akin to medical imaging, the rotationally broadened profiles from such stars can be used to reconstruct ‘Doppler images’ of the distribution of cool, dark starspots on their stellar surfaces. Interacting binaries, however, contain some of the most rapidly rotating late‐type stars known and thus provide important tests of stellar dynamo models. Furthermore, magnetic activity is thought to play a key role in their evolution, behaviour and accretion dynamics. Despite this, we know comparatively little about the magnetic activity and its influence on such binaries. In this review we summarise the concepts behind indirect imaging of these systems, and present movies of the starspot distributions on the cool stars in some interacting binaries. We conclude with a look at the future opportunities that such studies may provide. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
463.
In steep and rocky terrains, their rough surfaces make it difficult to create landslide inventories even with detailed maps/images produced from airborne LiDAR data. To provide objective clues in locating deep-seated landslides, the surface textures of a 5 km2 steepland area in Japan was investigated using the eigenvalue ratio and slope filters calculated from a very high resolution LiDAR-derived DEM. The range of filter values was determined for each of a number of surface features mapped in the field and these included: cracked bedrock outcrops, coarse colluvial deposits, gently undulating surfaces, and smooth surfaces. Recently active slides commonly contained patches of ground in which deposition and erosion occurred together near the erosion front, or where cracked bedrock outcrops and coarse colluvial deposits coexisted under a gently undulating surface. The characteristic eigenvalue and slope filter values representing this sliding process were applied to maps of the DEM derived filter values to extract potential sites of recent landslide activity. In addition, the relationships between the filter values of deep-seated landslides at various stages of evolution within the field mapped area were extended to the entire study area, to assess the contribution that landslide evolution makes to change in the landscape as a whole. While landslide components made up the steepest as well as the gentlest parts of the landscape depending on their evolutionary stage, landslides were constantly coarsened and steepened by progressive erosion, probably initiated by river bank erosion at the foot of slopes.  相似文献   
464.
We present MERLIN observations of the symbiotic nova V1016 Cygni made at 6 cm between 1992 and 1997 and at 18 cm in 1993 and 1997. In the 6-cm images we find complex structure which has not been previously seen, in particular three bright components. These components do not appear to be expanding as would be expected from the remains of a hot wind resulting from the nova outburst. The change in positions of two of the features exhibits tentative east–west movement. The brightness temperature of the peak with the highest flux density remains above 50 000 K in all epochs, thereby confirming the presence of shocked material in the system. At 18 cm there is no evidence of any non-thermal emission as might be expected from comparison with a sister star, HM Sge.  相似文献   
465.
466.
This study assesses selected impacts on tertiary activities of the anomalously hot summer of 1995 and warm period from November 1994 through October 1995 in the U.K. Over this period, the mean Central England temperature was 1.6 °C above the 1961–1990 normal, representing the highest mean 12-month temperature since the start of the Central England temperature record in 1659. The study is distinguished by its breadth of coverage, for it includes tertiary sectors and activities. Although impacts in tertiary activities are often not included in assessments of the potential impacts of climatic change, many of these activities are very important to the U.K. economy, and therefore even a small perturbation in output due to a weather extreme can have significant implications for the economy as a whole. The activities and sectors studied include energy consumption, retailing and manufacturing, construction and buildings, tourism, health, human behaviour, and fires. Both negative and positive impacts were incurred within most sectors. Net positive impacts (to the general public) were found convincingly for energy consumption and health, and clear negative impacts for buildings insurance and fires. Sectors which show clear differences in their response to winter and summer warm anomalies are energy consumption, tourism and health (greater sensitivity to winter anomalies) and buildings insurance and fires (greater sensitivity to summer anomalies). Changes in sensitivity to climate extremes may have occurred over time, and a comparison of impacts of the 1995 anomalous weather with the unusually warm dry period of 1975–1976 is approached for several series.  相似文献   
467.
This paper presents the results from the Jodrell BankInstituto de Astrofisicia de Canarias (IAC) two-element 33-GHz interferometer operated with an element separation of 32.9 wavelengths and hence sensitive to 1°-scale structure on the sky. The level of cosmic microwave background (CMB) fluctuations, assuming a flat CMB spatial power spectrum over the range of multipoles =208±18, was found using a likelihood analysis to be at the 68 per cent confidence level, after the subtraction of the contribution of monitored point sources. Other possible foreground contributions have been assessed and are expected to have negligible impact on this result.  相似文献   
468.
Results are presented from the seventy five laboratories participating in GeoPT4, round four of the international proficiency testing programme for analytical geochemistry laboratories. Laboratories were required to analyse the sample OU-2 (Belford dolerite) using routine methods of analysis. The sample was distributed during September 1998 with a deadline for the submission of results of 15th January 1999. In this report, contributed data are analysed and z-scores calculated. Z-score values provide participating laboratories with information concerning the quality of their results and indicate data that may be subject to unsuspected analytical bias. Laboratories are invited to examine these data and take the appropriate action.  相似文献   
469.
    
  相似文献   
470.
Measurements of the lateral distribution function (ldf) of Extensive Air Showers (EAS) as recorded by the array of water- erenkov detectors at Haverah Park are described, and accurate experimental parameterizations expressing the mean ldf for 2 × 1017 < E < 4 × 1018 eV, 50 < r < 700 m, and θ < 45° are given. An extrapolation of these relations to the regime E ≥ 1019 eV and r > 700 m is described: extrapolation in this energy domain appears valid, and an approximate correction term is given for the larger core distances. The results of recent Monte Carlo simulations of shower development and detector behavior are compared to the parameterized ldf. The agreement is good increasing confidence that these simulations may be trusted as design tools for the Auger project, a proposed ‘next generation’ detector system.  相似文献   
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