全文获取类型
收费全文 | 137篇 |
免费 | 0篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 33篇 |
地球物理 | 17篇 |
地质学 | 39篇 |
海洋学 | 13篇 |
天文学 | 29篇 |
自然地理 | 9篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2017年 | 1篇 |
2015年 | 1篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 7篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 12篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 31 毫秒
51.
52.
Using key dates associated with solar interaction regions (SIR), a superposed epoch analysis is performed on the zonal and meridional kinetic energy density and square of the vorticity (enstrophy) of the main motion at 500 mb height. No relationships are found between SIR and these atmospheric dynamical parameters irrespective of the polarity (North or South) of the enhanced interplanetary magnetic fields (IMF) within the SIR, or with latitude and season. This investigation and other available results suggest that the short term solar variations do not influence large volumes of the troposphere but only localized regions.The average atmospheric kinetic energy density during active solar conditions is higher than during quiet solar condition, with no significant differences in enstrophy. This confirms an earlier result.It is also shown that SIR with enhanced southward directed IMF correspond to higher level of geomagnetic index (Ap > 10, Kp > 3) than randomly selected days. 相似文献
53.
R. Auld R. F. Minchin J. I. Davies B. Catinella W. van Driel P. A. Henning S. Linder E. Momjian E. Muller K. O'Neil S. Sabatini S. Schneider G. Bothun L. Cortese M. Disney G. L. Hoffman M. Putman J. L. Rosenberg M. Baes W. J. G. de Blok A. Boselli E. Brinks N. Brosch J. Irwin I. D. Karachentsev V. A. Kilborn B. Koribalski K. Spekkens † 《Monthly notices of the Royal Astronomical Society》2006,371(4):1617-1640
54.
55.
The use of rotating modulation collimators in high resolution solar X-ray spectroscopy is discussed with reference to the recent flight of a sounding rocket payload. This rocket carried an experiment which combined a modulation collimator and a Bragg crystal spectrometer to make moderately high resolution spectral and spatial measurements simultaneously. The response of the instrument to extended sources is described. It is shown that the technique is particularly suited to long term observations of active region emission, but that useful measurements can be made even during a short rocket flight.Our observations were made in 1972 October 26 between 0432 UT and 0436 UT. During the flight a scan of the solar X-ray spectrum was made which covered the wavelength range 1.45–1.71 nm. A small flare commenced at about 0432 UT in McMath calcium plage region 12094; the emission from this provided the major contribution to the observed spectrum. X-ray emission from a group of active regions in the SW and the small McMath region 12090 has also been detected.Spectral and spatial observations have been combined to investigate the conditions in both active region and flare plasmas. 相似文献
56.
57.
A previously presented objective method to calculate each species sensitivity to disturbance is here slightly modified and implemented in the Benthic Quality Index (BQI) for marine benthic invertebrates. A framework for assessment of water bodies based on multi-site BQI-values is also presented, where a certain variation of BQI-values is allowed to cover the heterogeneity within each water body. The 20th percentile, using bootstrapping, from the available sites’ BQI-values is compared with the status boundaries for quality assessment. The reliability of the assessment depends on the background information available for the boundary setting as well as the number of sampling sites included in the assessment. Agreement between time series of quality assessments in areas with known changes in anthropogenic disturbances is encouraging. Problems associated with water body assessment based on few or no samples, as well as multiple sampling occasions during the 6-yr WFD cycle are discussed. 相似文献
58.
Temporal and spatial changes in marine benthic habitats in relation to the EU Water Framework Directive: The use of sediment profile imagery 总被引:1,自引:0,他引:1
In 2002 to 2006, sediment profile imagery (SPI) was used to study the environmental impact of eutrophication-induced irregular and seasonal hypoxia on marine benthic habitats in six regions in the Skagerrak and Kattegat (West Sweden). The benthic habitat quality (BHQ) was assessed by parameterisation of biogenic structures observed by the SPI technique, and benthic quality status was related to the EU Water Framework Directive (EU-WFD). The temporal changes were analysed by a 5-factor nested ANOVA and significant temporal differences were recorded within three of the regions. Two of these were affected by hypoxia in the deeper parts and one was probably affected by hypoxia below the halocline. The environmental quality status according to the EU-WFD was bad to high in two regions, moderate to good in three regions, and good to high, i.e., acceptable according to the EU-WFD, in only one region. As BHQ is highly correlated to benthic faunal data, measures have to be taken to improve the coastal water quality in five of the six studied areas. 相似文献
59.
L. Cortese R. F. Minchin R. R. Auld J. I. Davies B. Catinella E. Momjian J. L. Rosenberg R. Taylor G. Gavazzi K. O'Neil M. Baes A. Boselli G. Bothun B. Koribalski S. Schneider W. van Driel 《Monthly notices of the Royal Astronomical Society》2008,383(4):1519-1537
We present 21 cm H i line observations of 5 × 1 deg2 centred on the local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment Survey. One hundred sources are detected (79 new H i measurements and 50 new redshifts), more than half belonging to the cluster core and its infalling region. Combining the H i data with Sloan Digital Sky Survey (SDSS) optical imaging, we show that our H i selected sample follows scaling relations similar to the ones usually observed in optically selected samples. Interestingly, all galaxies in our sample appear to have nearly the same baryon fraction independently of their size, surface brightness and luminosity. The most striking difference between H i and optically selected samples resides in their large-scale distribution: whereas optical and X-ray observations trace the cluster core very well, in H i there is almost no evidence of the presence of the cluster. Some implications on the determination of the cluster luminosity function and H i distribution for samples selected at different wavelength are also discussed. 相似文献
60.
Allison M. Thomson Robert A. Brown Steven J. Ghan R. Cesar Izaurralde Norman J. Rosenberg L. Ruby Leung 《Climatic change》2002,54(1-2):141-164
Crop growth models, used in climate change impact assessments to project production on a local scale, can obtain the daily weather information to drive them from models of the Earth's climate. General Circulation Models (GCMs), often used for this purpose, provide weather information for the entire globe but often cannot depict details of regional climates especially where complex topography plays an important role in weather patterns. The U.S. Pacific Northwest is an important wheat growing region where climate patterns are difficult to resolve with a coarse scale GCM. Here, we use the PNNL Regional Climate Model (RCM) which uses a sub-grid parameterization to resolve the complex topography and simulate meteorology to drive the Erosion Productivity Impact Calculator (EPIC) crop model. The climate scenarios were extracted from the PNNL-RCM baseline and 2 × CO2 simulationsfor each of sixteen 90 km2 grid cells of the RCM, with differentiation byelevation and without correction for climate biases. The dominant agricultural soil type and farm management practices were established for each grid cell. Using these climate and management data in EPIC, we simulated winter wheat production in eastern Washington for current climate conditions (baseline) and a 2 × CO2 `greenhouse' scenario of climate change.Dryland wheat yields for the baseline climate averaged 4.52 Mg ha–1 across the study region. Yields were zero at high elevations where temperatures were too low to allow the crops to mature. The highest yields (7.32 Mgha–1) occurred at intermediate elevations with sufficientprecipitation and mild temperatures. Mean yield of dryland winter wheat increased to 5.45 Mg ha–1 for the 2 × CO2 climate, which wasmarkedly warmer and wetter. Simulated yields of irrigated wheat were generally higher than dryland yields and followed the same pattern but were, of course, less sensitive to increases in precipitation. Increases in dryland and irrigated wheat yields were due, principally, to decreases in the frequency of temperature and water stress. This study shows that the elevation of a farm is a more important determinant of yield than farm location in eastern Washington and that climate changes would affect wheat yields at all farms in the study. 相似文献