全文获取类型
收费全文 | 63篇 |
免费 | 3篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 3篇 |
地球物理 | 14篇 |
地质学 | 11篇 |
海洋学 | 4篇 |
天文学 | 30篇 |
自然地理 | 3篇 |
出版年
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2000年 | 2篇 |
1989年 | 1篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1970年 | 4篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 2篇 |
1963年 | 1篇 |
排序方式: 共有66条查询结果,搜索用时 734 毫秒
11.
Philip H. Scherrer John M. Wilcox Valeri Kotov A. B. Severny Robert Howard 《Solar physics》1977,52(1):vi-12
The mean solar magnetic field as measured in integrated light has been observed since 1968. Since 1970 it has been observed both at Hale Observatories and at the Crimean Astrophysical Observatory. The observing procedures at both observatories and their implications for mean field measurements are discussed. A comparison of the two sets of daily observations shows that similar results are obtained at both observatories. A comparison of the mean field with the interplanetary magnetic polarity shows that the IMF sector structure has the same pattern as the mean field polarity. 相似文献
12.
Andrew S. Tanenbaum John M. Wilcox Edward N. Franzier Robert Howard 《Solar physics》1969,9(2):328-342
One dimensional magnetograph scans have been used to study the 5-min photospheric velocity oscillations and the supergranulation.
The oscillations in wing brightness lead the oscillations in velocity by less than 90° in the photosphere, and about 90° in
the chromosphere, suggesting that they are traveling waves at lower levels and standing waves at higher levels. Downward flows
have been observed to be coincident with the chromospheric network confirming the hypothesis that material is flowing downward
at supergranular boundaries. 相似文献
13.
A clearly evident large-scale pattern in the interplanetary magnetic field during 1964 is used to search for a similar large-scale pattern in the solar magnetic field. It is found that such a pattern did exist in the photospheric field observations on both sides of the equator over a range of at least 40°N to 35°S. The pattern is basically similar at all these latitudes, and differs from that to be expected from solar differential rotation in three important respects. It is found that the solar magnetic pattern changed at all latitudes investigated within an interval of a few solar rotations. 相似文献
14.
Ng Jing Lin Abd Aziz Samsuzana Huang Yuk Feng Wayayok Aimrun Rowshon MK 《Theoretical and Applied Climatology》2018,133(1-2):489-509
Theoretical and Applied Climatology - A tropical country like Malaysia is characterized by intense localized precipitation with temperatures remaining relatively constant throughout the year. A... 相似文献
15.
Jeffrey D. Wilcox 《水文研究》2019,33(11):1538-1541
Solar eclipses provide opportunities to observe unusual natural phenomena. This paper presents data showing that diurnal groundwater fluctuations were briefly interrupted in a Southern Appalachian fen following a total solar eclipse on August 21, 2017. Groundwater levels, which were rapidly declining in the middle of a summer afternoon, nearly stabilized following totality. This anomaly in the water‐level record was caused by reduced evapotranspiration (ET). ET was significantly lower (36% ± 11%, p < 0.02) over a 45‐min time period following the eclipse when compared with other days within the study period, although the effects were short lived and did not have a significant impact on the daily total ET (p > 0.05). These findings may prompt evaluation of existing groundwater records along the path of totality from past eclipses or plan for studies ahead of future eclipses. 相似文献
16.
The zoogeography of marine Bryozoa around South Africa was investigated using published distribution records, museum catalogues, and an examination of previously unworked bryozoan material in (mostly) museum collections. Although a total of 276 valid species are recognised, it was not possible to unambiguously assess geographic patterns of diversity. At all depth zones examined (shore and inner-shelf, 0–30 m; mid- and outer-shelf, 31–350 m; bathyal, >500 m), there was a clear geographic structure to communities that mirrored established regional patterns of biogeography. Too few samples were collected from the shelf edge (351–500 m) and they were consequently excluded from zoogeographic analysis. Communities on the shore and inner-shelf and on the mid- and outer-shelf were more similar to each other than they were to bathyal communities, and the pronounced structure in bathyal communities suggests heterogeneity in the deep sea around South Africa. 相似文献
17.
Robert J. Orth Scott R. Marion Kenneth A. Moore David J. Wilcox 《Estuaries and Coasts》2010,33(1):139-150
Decreases in seagrass abundance reported from numerous locations around the world suggest that seagrass are facing a global
crisis. Declining water quality has been identified as the leading cause for most losses. Increased public awareness is leading
to expanded efforts for conservation and restoration. Here, we report on abundance patterns and environmental issues facing
eelgrass (Zostera marina), the dominant seagrass species in the Chesapeake Bay region in the mid-Atlantic coast of the USA, and describe efforts to
promote its protection and restoration. Eelgrass beds in Chesapeake Bay and Chincoteague Bay, which had started to recover
from earlier diebacks, have shown a downward trend in the last 5–10 years, while eelgrass beds in the Virginia coastal bays
have substantially increased in abundance during this same time period. Declining water quality appears to be the primary
reason for the decreased abundance, but a recent baywide dieback in 2005 was associated with higher than usual summer water
temperatures along with poor water clarity. The success of eelgrass in the Virginia coastal bays has been attributed, in part,
to slightly cooler water due to their proximity to the Atlantic Ocean. A number of policies and regulations have been adopted
in this region since 1983 aimed at protecting and restoring both habitat and water quality. Eelgrass abundance is now one
of the criteria for assessing attainment of water clarity goals in this region. Numerous transplant projects have been aimed
at restoring eelgrass but most have not succeeded beyond 1 to 2 years. A notable exception is the large-scale restoration
effort in the Virginia coastal bays, where seeds distributed beginning in 2001 has initiated an expanding recovery process.
Our research on eelgrass abundance patterns in the Chesapeake Bay region and the processes contributing to these patterns
have provided a scientific background for management strategies for the protection and restoration of eelgrass and insights
into the causes of success and failure of restoration efforts that may have applications to other seagrass systems. 相似文献
18.
Donal R. Mullineaux Ray E. Wilcox Walter F. Ebaugh Roald Fryxell Meyer Rubin 《Quaternary Research》1978,10(2):171-180
Pumice layers of set S from Mount St. Helens can be correlated with certain ash beds associated with young flood deposits of the channeled scabland. The correlation points to an age of about 13,000 14C yr B.P. for the last major flood to have crossed the scabland. Until recently, the last major episode of flooding was thought to be closer to 20,000 yr B.P., an age inferred chiefly from the relation of the flood to glacial events of the northern Rocky Mountains. Several investigations within the last few years have suggested that the last major flood occurred well after 20,000 yr B.P. Tentative correlations of ash beds of the scabland with set S pumice layers, the relations of flood and glacial events along the northwestern margin of the Columbia Plateau, and a radiocarbon date from the Snake River drainage southeast of the plateau all indicate an age much younger than 20,000 yr. The postulated age of about 13,000 yr B.P. is further supported by a radiocarbon date in the Columbia River valley downstream from the scabland tract. Basal peat from a bog on the Portland delta of Bretz, which is a downvalley deposit of the last major scabland flood, has been dated as 13,080 ± 300 yr B.P. (W-3404). 相似文献
19.
Habitat requirements for submerged aquatic vegetation in Chesapeake Bay: Water quality, light regime, and physical-chemical factors 总被引:1,自引:0,他引:1
W. Michael Kemp Richard Batleson Peter Bergstrom Virginia Carter Charles L. Gallegos William Hunley Lee Karrh Evamaria W. Koch Jurate M. Landwehr Kenneth A. Moore Laura Murray Michael Naylor Nancy B. Rybicki J. Court Stevenson David J. Wilcox 《Estuaries and Coasts》2004,27(3):363-377
We developed an algorithm for calculating habitat suitability for seagrasses and related submerged aquatic vegetation (SAV) at coastal sites where monitoring data are available for five water quality variables that govern light availability at the leaf surface. We developed independent estimates of the minimum light required for SAV survival both as a percentage of surface light passing though the water column to the depth of SAV growth (PLW min) and as a percentage of light reaching reaching leaves through the epiphyte layer (PLL min). Value were computed by applying, as inputs to this algorithm, statistically dervived values for water quality variables that correspond to thresholds for SAV presence in Chesapeake Bay. These estimates ofPLW min andPLL min compared well with the values established from a literature review. Calcultations account for tidal range, and total light attenuation is partitioned into water column and epiphyte contributions. Water column attenuation is further partitioned into effects of chlorophylla (chla), total suspended solids (TSS) and other substances. We used this algorithm to predict potential SAV presence throughout the Bay where calculated light available at plant leaves exceededPLL min. Predictions closely matched results of aerial photographic monitoring surveys of SAV distribution. Correspondence between predictions and observations was particularly strong in the mesohaline and polythaline regions, which contain 75–80% of all potential SAV sites in this estuary. The method also allows for independent assessment of effects of physical and chemical factors other than light in limiting SAV growth and survival. Although this algorithm was developed with data from Chesapeake Bay, its general structure allows it to be calibrated and used as a quantitative tool for applying water quality data to define suitability of specific sites as habitats for SAV survival in diverse coastal environments worldwide. 相似文献
20.