全文获取类型
收费全文 | 49篇 |
免费 | 3篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 4篇 |
地球物理 | 18篇 |
地质学 | 11篇 |
海洋学 | 5篇 |
天文学 | 3篇 |
自然地理 | 6篇 |
出版年
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 1篇 |
2007年 | 1篇 |
2006年 | 5篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有52条查询结果,搜索用时 15 毫秒
31.
Molly M. Miller Scott W. Phipps Clinton S. Major Kelly M. Major 《Estuaries and Coasts》2011,34(6):1182-1193
This study was designed to investigate non-point source nutrient pollution and its influences on submerged aquatic plant community
structure and biological invasion in the Weeks Bay National Estuarine Research Reserve (WBNERR). A monthly vegetation survey
was conducted to document plant abundance and changes in community structure; physicochemical data and water samples were
collected on a bi-monthly basis to monitor environmental conditions (i.e., pH, salinity, dissolved oxygen, light intensity,
and attenuation) and water column nutrient (NO2−/NO3− and NH4+) and chlorophyll a concentrations. A total of seven submerged aquatic species were identified at the WBNERR with the occurrence of only one
non-native species (Hydrilla verticillata). Statistical analyses suggest that water column nitrogen concentrations along with variations in dissolved oxygen (0.6–11.5 mg L−1), light attenuation, pH (5.6–8.6), and temperature (11–33°C) play key roles in determining the aquatic plant abundance and
distribution in the WBNERR. 相似文献
32.
Wendy M. Robertson Molly Robinett Deborah G. McCullough 《Environmental Earth Sciences》2018,77(9):356
Emerald ash borer (EAB) (Agrilus planipennis Fairmaire), an invasive forest insect first identified in southeastern Michigan in 2002, is established in at least 32 US states and three Canadian provinces. Ash (Fraxinus spp.) mortality rates in some forested areas exceed 90%, but to date, little is known about the potential effects of EAB-caused ash mortality on hydrological processes. More broadly, there is a need for information on the timing and magnitude of soil moisture response to species-specific mortality of overstory vegetation in deciduous forest systems. Soil moisture was examined in 28 forested sites where 0–100% of the white ash basal area (Fraxinus americana L.) was killed by EAB. Synoptic measurements of near-surface (0–6 cm depth) soil moisture were collected from 112 plots (18 m radius) within the sites. Three plots were also instrumented with soil moisture sensors at 10 and 25 cm depth to log hourly measurements from May to October. Synoptic data showing white ash mortality and soil moisture were positively correlated in the 34 plots with ≥?5% mortality (by total basal area). In the intensively monitored plots, volumetric soil moisture declined from 37 to 16% between July and September where white ash mortality was low (0.6% of basal area killed), but remained near field capacity (~?30%) throughout the monitoring period in the high mortality plot (8.6% of basal area killed), meriting further investigation to assess effects of white ash mortality on evapotranspiration and soil moisture dynamics in heterogeneous upland forests. Altered soil moisture may have implications for regrowth dynamics, infiltration/runoff partitioning, and nutrient cycling, but additional study to quantify the extent and duration of EAB-related ash mortality on hydrology at the plot and watershed scale is necessary. 相似文献
33.
Christopher S. Meinen Molly O. Baringer Rigoberto F. Garcia 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(7):835-846
More than forty years of Florida Current transport estimates are combined to study annual and longer-term variability in this important component of the MOC and subtropical gyre. A detailed analysis with error estimates illustrates the difficulties in extracting annual and longer time scale variability given the strong higher frequency energy present. The annual cycle represents less than 10% of the total Florida Current transport variance in a 16 yr segment of the record, while interannual (13–42 month) variability represents only 13% of the total and periods longer than 42 months represents less than 10% of the total. Given the observed high frequency variability of the Florida Current, in order to get a monthly mean that is accurate to within 0.5 Sv (one standard error level) more than 20 daily observations are needed. To obtain an estimate of the annual climatology that is “accurate” to within 20% of its own standard deviation, at least 24 yr of data is needed. More than 40 observations spread throughout a year are required to obtain an annual mean that is accurate to within 0.5 Sv. Despite these daunting data requirements, there is sufficient data now to evaluate both the annual cycle of the Florida Current transport with a high degree of accuracy and to begin to determine the longer period transport variability. Comparison of the Florida Current, NAO and wind stress curl records shows that a recently described Sverdrup-based mechanism explains a significant fraction of the long-period variability primarily during the 1986–1998 time window, with other mechanisms clearly dominating before and after. 相似文献
34.
35.
Traditional fecal coliform bacterial indicators have been found to be severely limited in determining the significance and
sources of fecal contamination in ambient waters of tropical and subtropical regions. The bacteriophages that infectBacteroides fragilis have been suggested as better fecal indicators and at least one type may be human specific. In this study, the phages that
infectB. fragilis host RYC2056 (RYC), including phage B56-3, and host ATCC 51477-HSP40 (HSP), including the human specific phage B40-8, were
evaluated in the drainage basins of Tampa Bay, 7 samples (n=62), or 11%, tested positive for the presence of phages infecting
the host HSP, whereas 28 samples, or 45%, tested positive using the host RYC. A survival study was also done to compare the
persistence of phages B56-3 and B40-8 to MS2 coliphage in seawater at various temperatures. The decay rates for MS2 were 0.239
log10 d−1 at 10°C, but increased to 0.896 at 20°C and 2.62 log10 d−1 at 30°C. The twoB. fragilis phages persisted much longer in the seawater compared to the coliphage and showed little variation between the temperatures.
All sewage influents sampled from area wastewater treatment plants contained phages that infected the twoB. fragilis hosts at levels from 1.2×104 to 1.11×105 pfu 100 ml−1 for host RYC and 67 to 350 pfu 100 ml−1 for host HSP. Of the 7 chlorinated effluent samples tested, 3 were positive for the presence of the phage using the host
RYC and the phage enrichment method, with levels estimated to be <10 pfu 100 ml−1. No phages were detected using the host HSP in the treated sewage effluent. Coliphages were found in 3 of the 7 effluent
samples at a range of 30 to 1.2×103 pfu 100 ml−1. 相似文献
36.
37.
A climate trend analysis of Ethiopia: examining subseasonal climate impacts on crops and pasture conditions 总被引:3,自引:0,他引:3
Molly E. Brown Chris Funk Diego Pedreros Diriba Korecha Melesse Lemma James Rowland Emily Williams James Verdin 《Climatic change》2017,142(1-2):169-182
Ethiopia experiences significant climate-induced drought and stress on crop and livestock productivity, contributing to widespread food insecurity. Here, we present subseasonal crop water stress analyses that indicate degrading, growing conditions along Ethiopia’s eastern highlands, including productive and populated highland regions. These seasonally shifting areas of increasing water stress stretch from the north to south across eastern Ethiopia, intersecting regions of acute food insecurity and/or high population. Crop model simulations indicate that between 1982 and 2014, parts of eastern Amhara and eastern Oromia experienced increasing water deficits during the critical sowing, flowering, and ripening periods of crop growth. These trends occurred while population in these regions increased by 143% between 2000 and 2015. These areas of enhanced crop water stress in south-central Ethiopia coincide with regions of high population growth and ongoing crop extensification. Conversely, large regions of relatively unpopulated western Ethiopia are becoming wetter. These areas may therefore be good targets for agricultural development. 相似文献
38.
39.
Molly F Spooner 《Marine pollution bulletin》1977,8(3):62-65
Fish farming was seriously but only temporarily affected by a large spill of a very toxic product oil at Hong Kong. Field experiments were set up to follow tainting and depuration. Studies were made of hydrography, water quality, oil in sands, macro- and meio-fauna of shores, and some observations made of possible effects on plankton and open-water fisheries. 相似文献
40.
Orozco-Borbón MV Rico-Mora R Weisberg SB Noble RT Dorsey JH Leecaster MK McGee CD 《Marine pollution bulletin》2006,52(10):1190-1196
This survey was part of a Binational Program (Mexico-United States) in microbiological water quality, with a goal to assess the shoreline bacteriological water quality from Tijuana to Ensenada, Mexico. Samples were collected at 29 sites (19 beaches and 10 outfalls), from the United States border to Punta Banda, Baja California, during summer (1998) and winter (1999). Total coliforms, fecal coliforms and enterococci were used as bacterial indicators. Standard methods were used for total and fecal coliforms, while the Enterolert quick method (IDEXX) was used for the enterococci. Compared with outfalls, the beaches exceeded water quality standards by a small percent, 25.3% in summer and 17% in winter. For outfalls, the percentage of shoreline that exceeded bacterial indicator thresholds had a minor value in summer (32.7%) than in winter (50%). Sites near wastewater discharges had the lowest quality and did not meet the microbiological water quality criteria for recreational use. 相似文献