全文获取类型
收费全文 | 70篇 |
免费 | 8篇 |
出版年
2021年 | 1篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 5篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1950年 | 1篇 |
1928年 | 1篇 |
1927年 | 1篇 |
1915年 | 1篇 |
排序方式: 共有78条查询结果,搜索用时 31 毫秒
1.
M.J. Siegert A. Behar M. Bentley D. Blake S. Bowden P. Christoffersen C. Cockell H. Corr D. C. Cullen H. Edwards A. Ellery C. Ellis-Evans G. Griffiths R. Hindmarsh D. A. Hodgson E. King H. Lamb L. Lane K. Makinson M. Mowlem J. Parnell D. A. Pearce J. Priscu A. Rivera M. A. Sephton M. R. Sims A . M. Smith M. Tranter J. L. Wadham G. Wilson J. Woodward 《Reviews in Environmental Science and Biotechnology》2007,6(1-3):161-179
Antarctic subglacial lakes have, over the past few years, been hypothesised to house unique forms of life and hold detailed
sedimentary records of past climate change. Testing this hypothesis requires in situ examinations. The direct measurement
of subglacial lakes has been considered ever since the largest and best-known lake, named Lake Vostok, was identified as having
a deep water-column. The Subglacial Antarctic Lake Environments (SALE) programme, set up by the Scientific Committee on Antarctic
Research (SCAR) to oversee subglacial lakes research, state that prior exploration of smaller lakes would be a “prudent way
forward”. Over 145 subglacial lakes are known to exist in Antarctica, but one lake in West Antarctica, officially named Ellsworth
Subglacial Lake (referred to hereafter as Lake Ellsworth), stands out as a candidate for early exploration. A consortium of
over 20 scientists from seven countries and 14 institutions has been assembled to plan the exploration of Lake Ellsworth.
An eight-year programme is envisaged: 3 years for a geophysical survey, 2 years for equipment development and testing, 1 year
for field planning and operation, and 2 years for sample analysis and data interpretation. The science experiment is simple
in concept but complex in execution. Lake Ellsworth will be accessed using hot water drilling. Once lake access is achieved,
a probe will be lowered down the borehole and into the lake. The probe will contain a series of instruments to measure biological,
chemical and physical characteristics of the lake water and sediments, and will utilise a tether to the ice surface through
which power, communication and data will be transmitted. The probe will pass through the water column to the lake floor. The
probe will then be pulled up and out of the lake, measuring its environment continually as this is done. Once at the ice surface,
any water samples collected will be taken from the probe for laboratory analysis (to take place over subsequent years). The
duration of the science mission, from deployment of the probe to its retrieval, is likely to take between 24 and 36 h. Measurements
to be taken by the probe will provide data about the following: depth, pressure, conductivity and temperature; pH levels;
biomolecules (using life marker chips); anions (using a chemical analyzer); visualisation of the environment (using cameras
and light sources); dissolved gases (using chromatography); and morphology of the lake floor and sediment structures (using
sonar). After the probe has been retrieved, a sediment corer may be dropped into the lake to recover material from the lake
floor. Finally, if time permits, a thermistor string may be left in the lake water to take time-dependent measurements of
the lake’s water column over subsequent years. Given that the comprehensive geophysical survey of the lake will take place
in two seasons during 2007–2009, a two-year instrument and logistic development phase from 2008 (after the lake’s bathymetry
has been assessed) makes it possible that the exploration of Lake Ellsworth could take place at the beginning of the next
decade. 相似文献
2.
C. Ellery Mayence David J. Marshall Robert C. Godfree 《Wetlands Ecology and Management》2010,18(6):717-730
Wetlands are prone to increased invasion by plant species following changes in hydrologic regime, leading to shifts in plant
community composition and potentially ecosystem function and health. In this paper, the ecology and potential control of Juncus ingens, a native wetland plant in the Murray-Darling Basin of south-eastern Australia, is investigated. J. ingens has benefited from altered Murray River hydrologic conditions by expanding its range and invading seasonally-flooded grassland
and riparian habitats along the Murray River. Here results of complementary glasshouse and field research of seedling and
mature J. ingens growth and resilience as influenced by hydrologic regime (moist, saturated, partial inundation and when possible, complete
inundation) and mechanical control (i.e., clipping) are presented. A moist hydrologic regime (soil held at field capacity)
resulted in the most vigorous seedlings (13.9–73.0% more total biomass), while saturated conditions (flooding maintained level
with the soil surface) resulted in the most vigorous mature J. ingens (14.1–98.4% more total biomass). Seedling mortality was greatest under complete and prolonged inundation (60% fatal with
remaining 40% showing severe stress), conditions suspected to have limited prior invasion but which currently occur infrequently
as a result of reduced flooding magnitude. Clipping was fatal for nearly all seedlings regardless of hydrologic regime but
was only fatal for mature plants if coupled with prolonged inundation. Coupling ground-level clipping with strategic flooding
may be the most effective means for controlling current populations of J. ingens and limiting further invasion, promoting re-colonisation by displaced species and rehabilitating the health of Barmah Forest
and similar Murray River floodplain wetlands. 相似文献
3.
Ellery PJ Tippett E Chiu YL Paukovics G Cameron PU Solomon A Lewin SR Gorry PR Jaworowski A Greene WC Sonza S Crowe SM 《Journal of immunology (Baltimore, Md. : 1950)》2007,178(10):6581-6589
HIV-1 persists in peripheral blood monocytes in individuals receiving highly active antiretroviral therapy (HAART) with viral suppression, despite these cells being poorly susceptible to infection in vitro. Because very few monocytes harbor HIV-1 in vivo, we considered whether a subset of monocytes might be more permissive to infection. We show that a minor CD16+ monocyte subset preferentially harbors HIV-1 in infected individuals on HAART when compared with the majority of monocytes (CD14highCD16-). We confirmed this by in vitro experiments showing that CD16+ monocytes were more susceptible to CCR5-using strains of HIV-1, a finding that is associated with higher CCR5 expression on these cells. CD16+ monocytes were also more permissive to infection with a vesicular stomatitis virus G protein-pseudotyped reporter strain of HIV-1 than the majority of monocytes, suggesting that they are better able to support HIV-1 replication after entry. Consistent with this observation, high molecular mass complexes of apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G (APOBEC3G) were observed in CD16+ monocytes that were similar to those observed in highly permissive T cells. In contrast, CD14highCD16- monocytes contained low molecular mass active APOBEC3G, suggesting this is a mechanism of resistance to HIV-1 infection in these cells. Collectively, these data show that CD16+ monocytes are preferentially susceptible to HIV-1 entry, more permissive for replication, and constitute a continuing source of viral persistence during HAART. 相似文献
4.
MARIA E. MCNAMARA PATRICK J. ORR TOM MANZOCCHI LUIS ALCALÁ PERE ANADÓN ENRIQUE PEÑALVER 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2012,45(2):210-226
McNamara, M.E., Orr, P.J., Manzocchi, T., Alcalá, L., Anadón, P. & Peñalver, E. 2011: Biological controls upon the physical taphonomy of exceptionally preserved salamanders from the Miocene of Rubielos de Mora, northeast Spain. Lethaia, Vol. 45, pp. 210–226. The middle Miocene Rubielos de Mora Konservat‐Lagerstätte of northeast Spain is hosted within profundal, finely laminated, lacustrine mudstones. The diverse biota includes abundant salamanders. Most individuals died during separate episodes and sank rapidly postmortem. Specimens are typically preserved in dorso‐ventral aspect, the most hydrodynamically stable orientation. The near‐cylindrical morphology of the body, however, allowed some carcasses to settle in or subsequently re‐orientate into, lateral orientations. Loss of skeletal elements (i.e. reduced completeness) reflects their location within the body and followed a distal to proximal trend. Two stages are identified: initial loss of a small number of phalanges, followed by loss of more proximal limb bones plus additional phalanges. Disarticulation is more complex: it occurred via several mechanisms (notably, abdominal rupture and re‐orientation of part of the body and limbs during decay) and shows no consistent pattern among specimens. The physical taphonomy of the salamanders is controlled predominantly by intrinsic biological factors, i.e. the geometry of the body and of individual skeletal elements, the orientation, inherent strength and location of specific joints and the extent to which soft tissues, particularly the skin, persist during decay. These biological factors probably control patterns of physical taphonomy of other fossil tetrapods with a similar skeletal configuration. □Articulation, completeness, Konservat‐Lagerstätten, orientation, quantitative taphonomy, salamanders. 相似文献
5.
Steve Horvath Abu NM Nazmul-Hossain Rodney PE Pollard Frans GM Kroese Arjan Vissink Cees GM Kallenberg Fred KL Spijkervet Hendrika Bootsma Sara A Michie Sven U Gorr Ammon B Peck Chaochao Cai Hui Zhou David TW Wong 《Arthritis research & therapy》2012,14(6):1-13
Bone tissue has an exceptional quality to regenerate to native tissue in response to injury. However, the fracture repair process requires mechanical stability or a viable biological microenvironment or both to ensure successful healing to native tissue. An improved understanding of the molecular and cellular events that occur during bone repair and remodeling has led to the development of biologic agents that can augment the biological microenvironment and enhance bone repair. Orthobiologics, including stem cells, osteoinductive growth factors, osteoconductive matrices, and anabolic agents, are available clinically for accelerating fracture repair and treatment of compromised bone repair situations like delayed unions and nonunions. Preclinical and clinical studies using biologic agents like recombinant bone morphogenetic proteins have demonstrated an efficacy similar or better than that of autologous bone graft in acute fracture healing. A lack of standardized outcome measures for comparison of biologic agents in clinical fracture repair trials, frequent off-label use, and a limited understanding of the biological activity of these agents at the bone repair site have limited their efficacy in clinical applications. 相似文献
6.
Jennifer B. Glass Si Chen Katherine S. Dawson Damian R. Horton Stefan Vogt Ellery D. Ingall 《Geomicrobiology journal》2018,35(1):81-89
Metal cofactors are required for many enzymes in anaerobic microbial respiration. This study examined iron, cobalt, nickel, copper, and zinc in cellular and abiotic phases at the single-cell scale for a sulfate-reducing bacterium (Desulfococcus multivorans) and a methanogenic archaeon (Methanosarcina acetivorans) using synchrotron X-ray fluorescence microscopy. Relative abundances of cellular metals were also measured by inductively coupled plasma mass spectrometry. For both species, zinc and iron were consistently the most abundant cellular metals. M. acetivorans contained higher nickel and cobalt content than D. multivorans, likely due to elevated metal requirements for methylotrophic methanogenesis. Cocultures contained spheroid zinc sulfides and cobalt/copper sulfides. 相似文献
7.
8.
Studies by eminent surgeons to reevaluate the place of radical operations in the treatment of carcinoma of the cervix—now that extensive procedures have become less hazardous—apparently have led to confusion in some minds as to choice between surgical and radiation therapy. Pending outcome of the studies, general employment of surgical treatment is unwarranted. Radiation is the treatment of choice in most cases, particularly if the lesion is in an early stage, although radical operation is indicated in certain rare early cases in which delivery of an effective dose of radiation to involved areas is technically difficult. Elsewise it appears at present that operation should be used only in cases of stages III or IV carcinoma—in which results by either means of treatment are poor.One hundred and seven patients were treated with a combination of x-ray and radium irradiation. X-ray was used first to reduce the hazard of implanting the radium. The “five-year arrest” rates were as follows: For 22 patients with stage I lesion, 70 per cent; for 31 with stage II, 55.7 per cent; 33 with stage III, 39.7 per cent; 21 with stage IV, 0. Eighteen patients with diagnosis of carcinoma of the cervix who had had subtotal hysterectomy were treated. The stage of the disease could not be determined. In this group the five-year arrest rate was 52 per cent. 相似文献
9.
Eight Danish Holstein cows were milked with a 1-mm thick specially designed soft liner on their right rear teat and a standard
liner mounted under extra high tension on their left rear teat. Four of the animals were overmilked for 5 min. Rear teats
were subjected to ultrasound examination on the first day and to infrared thermography on the second day. Teats were submersed
in ethanol 20 min post-milking on the second day. Ultrasonography measurements showed that teat canal length increased by
30–41% during milking. Twenty minutes after milking, teats milked with modified standard liners still had elongated teat canals
while teats milked with the soft liner were normalized. Overmilking tended to increase teat wall thickness. Approximately
80% of variability in teat canal length, from before teat preparation to after milking, could be explained by changes during
teat preparation. Thermography indicated a general drop in teat temperature during teat preparation. Teat temperature increased
during milking and continued to increase until the ethanol challenge induced a significant drop. Temperatures approached pre-challenge
rather than pre-milking temperatures within 10 minutes after challenge. Teat temperatures were dependent on type of liner.
Mid-teat temperatures post-challenge relative to pre-teat preparation were dependent on overmilking. Thermography and ultrasound
were considered useful methods to indirectly and non invasively evaluate teat tissue integrity. 相似文献
10.
To find out the infection efficiency of recombinant adeno-as sociated virus 2-mediated exogenou s genes in human peripheral blood monocyte-derived dendritic cells(D Cs),the process of transfection wa s investigated by FITC-labeled rAA V2,and observed under confocal mic roscope.Newly separated dendritic cells were tranfected by rAAV2-luc and rAAV2-GFP at different MOI,and transfection efficiency were detec ted by luminometer for rAAV2-luc a nd flow cytometry for rAAV2-GFP.Th e results were elucidated in four different assay systems:(1)60min w as needed for rAAV2 to bind on den dritic cells,and got into cells in the following 10min;(2)the express ion of luc could be detected at th e MOI as low as 1×10~5v.g/cell,and the expression plateau was reached by the MOI of 10~6~10~7v.g/cell,furt her increase of MOI had no functio n on expression level;(3)transgene expression was detected after 48h, and maintained a higher expression level from 96h to 240h after infec tion;(4)7days postinfection of rAA V2-GFP,5%~18% dendritic cells were GFP positive. These data suggest th at rAAV2 vector can efficiently in fect monocyte-derived dendritic ce lls and mediate exogenous gene exp ression,and that the application o f rAAV2 as vector may be useful fo r gene transfer to dendritic cells in ex vivo immunotherapy. 相似文献