全文获取类型
收费全文 | 83篇 |
免费 | 6篇 |
出版年
2022年 | 1篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2015年 | 4篇 |
2013年 | 2篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1964年 | 2篇 |
排序方式: 共有89条查询结果,搜索用时 250 毫秒
1.
Seven male newborns of Chinese, Greek and Italian origin presented with severe hemolytic jaundice due to red cell glucose-6-phosphate dehydrogenase (G-6-PD) deficiency. In five, the hemolysis was precipitated by inhalation of mothball vapours in the home. Kernicterus was evident upon admission in six infants and was fatal in four of these.G-6-PD deficiency should be suspected as a cause of jaundice in all full-term male infants of these ethnic groups. The diagnosis can be confirmed in any hospital by the methemoglobin reduction test. In areas similar to Toronto, Canada, where these high-risk ethnic groups prevail, the following measures are recommended: (1) detection of G-6-PD deficient newborns by screening cord bloods of all infants of these ethnic groups; (2) protection of affected infants from potentially hemolytic agents such as naphthalene, certain vitamin K preparations, and sulfonamides; and (3) observation of serum bilirubin levels to assess the need for exchange transfusion for hyperbilirubinemia. 相似文献
2.
3.
Classical genetic studies suggest strong complex genetic contributions to a predisposition to abuse multiple addictive substances. Until recently, there were no reproducible genome scanning data identifying chromosomal positions likely to contain allelic variants that predispose the carrier to illegal substance addiction. Nominal results of linkage-based genome scanning studies for ethanol and nicotine addictions failed to display much agreement. Our recent data from association-based genome scans for illegal addictions, and reanalyses of previous results now provide a substantial body of converging results. The 15 reproducible chromosomal loci identified here are good candidates to harbor allelic variants that alter human substance abuse vulnerabilities. We discuss several approaches to identifying the specific gene variants that underlie these convergent association and linkage observations, and the impact that these convergent observations should have on understanding important human addictive disorders. 相似文献
4.
Bo Chen Allison L. Miller Marlon Rebelatto Yambasu Brewah Daniel C. Rowe Lori Clarke Meggan Czapiga Kim Rosenthal Tomozumi Imamichi Yan Chen Chew-Shun Chang Partha S. Chowdhury Brian Naiman Yue Wang De Yang Alison A. Humbles Ronald Herbst Gary P. Sims 《PloS one》2015,10(2)
Release of endogenous damage associated molecular patterns (DAMPs), including members of the S100 family, are associated with infection, cellular stress, tissue damage and cancer. The extracellular functions of this family of calcium binding proteins, particularly S100A8, S100A9 and S100A12, are being delineated. They appear to mediate their functions via receptor for advanced glycation endproducts (RAGE) or TLR4, but there remains considerable uncertainty over the relative physiological roles of these DAMPs and their pattern recognition receptors. In this study, we surveyed the capacity of S100 proteins to induce proinflammatory cytokines and cell migration, and the contribution RAGE and TLR4 to mediate these responses in vitro. Using adenoviral delivery of murine S100A9, we also examined the potential for S100A9 homodimers to trigger lung inflammation in vivo. S100A8, S100A9 and S100A12, but not the S100A8/A9 heterodimer, induced modest levels of TLR4-mediated cytokine production from human PBMC. In contrast, for most S100s including S100A9, RAGE blockade inhibited S100-mediated cell migration of THP1 cells and major leukocyte populations, whereas TLR4-blockade had no effect. Intranasal administration of murine S100A9 adenovirus induced a specific, time-dependent predominately macrophage infiltration that coincided with elevated S100A9 levels and proinflammatory cytokines in the BAL fluid. Inflammatory cytokines were markedly ablated in the TLR4-defective mice, but unexpectedly the loss of TLR4 signaling or RAGE-deficiency did not appreciably impact the S100A9-mediated lung pathology or the inflammatory cell infiltrate in the alveolar space. These data demonstrate that physiological levels of S100A9 homodimers can trigger an inflammatory response in vivo, and despite the capacity of RAGE and TLR4 blockade to inhibit responses in vitro, the response is predominately independent of both these receptors. 相似文献
5.
MOTIVATION: In proteomics, reverse database searching is used to control the false match frequency for tandem mass spectrum/peptide sequence matches, but reversal creates sequences devoid of patterns that usually challenge database-search software. RESULTS: We designed an unsupervised pattern recognition algorithm for detecting patterns with various lengths from large sequence datasets. The patterns found in a protein sequence database were used to create decoy databases using a Monte Carlo sampling algorithm. Searching these decoy databases led to the prediction of false positive rates for spectrum/peptide sequence matches. We show examples where this method, independent of instrumentation, database-search software and samples, provides better estimation of false positive identification rates than a prevailing reverse database searching method. The pattern detection algorithm can also be used to analyze sequences for other purposes in biology or cryptology. AVAILABILITY: On request from the authors. SUPPLEMENTARY INFORMATION: http://bioinformatics.psb.ugent.be/. 相似文献
6.
We investigated whether large woody debris (LWD) piles create nodes of environmental resources that contribute to the recovery
of riparian vegetation and that also augment the heterogeneity and resilience of the riverine system. River and riparian systems
are typified by a large degree of heterogeneity and complex interactions between abiotic and biotic elements. Disturbance
such as floods re-distribute the resources, such as LWD, and thereby add greater complexity to the system. We examined this
issue on a semi-arid savanna river where a ~100-year return interval flood in 2000 uprooted vegetation and deposited substantial
LWD. We investigated the micro-environment within the newly established LWD piles and compared this with conditions at adjacent
reference sites containing no LWD. We found soil nutrient concentrations to be significantly higher in LWD piles compared
with the reference plots (total N +19%, available P +51%, and total C +36%). Environmental variables within LWD piles and
reference sites varied with landscape position in the river–riparian landscape and with LWD pile characteristics. Observed
differences were generally between piles located in the terrestrial and riparian areas as compared to piles located on the
macro-channel floor. After 3 years the number and cover of woody species were significantly higher when associated with LWD
piles, regardless of landscape position or pile type. We conclude that LWD piles formed after large floods act as resource
nodes by accumulating fine sediments and by retaining soil nutrients and soil moisture. The subsequent influence of LWD deposition
on riparian heterogeneity is discerned at several spatial scales including within and between LWD piles, across landscape
positions and between channel types. LWD piles substantially influence the initial developmental of riparian vegetation as
the system regenerates following large destructive floods. 相似文献
7.
The term “keystone species” is used to describe organisms that exert a disproportionately important influence on the ecosystems
in which they live. Analogous concepts such as “keystone mutualism” and “mobile links” illustrate how, in many cases, the
interactions of two or more species produce an effect greater than that of any one species individually. Because of their
role in transporting nutrients from the ocean to river and riparian ecosystems, Pacific salmon (Oncorhynchus spp.) and brown bear (Ursus arctos) have been described as keystone species and mobile links, although few data are available to quantify the importance of
this interaction relative to other nutrient vectors. Application of a mass balance model to data from a southwestern Alaskan
stream suggests that nitrogen (N) influx to the riparian forest is significantly increased in the presence of both salmon
and bear, but not by either species individually. The interactions of salmon and bear may provide up to 24% of riparian N
budgets, but this percentage varies in time and space according to variations in salmon escapement, channel morphology and
watershed vegetation characteristics, suggesting interdependence and functional redundancy among N sources. These findings
illustrate the complexity of interspecific interactions, the importance of linkages across ecosystem boundaries and the necessity
of examining the processes and interactions that shape ecological communities, rather than their specific component parts. 相似文献
8.
Abundance and Production of Riparian Trees in the Lowland Floodplain of the Queets River, Washington 总被引:1,自引:1,他引:0
Riparian zones associated with alluvial rivers are spatially dynamic, forming distinct vegetative mosaics that exhibit sharp
contrasts in structure and processes related to the underlying biophysical template. The productivity of riparian plants,
especially trees, influences streamside community characteristics as well as the forms and fluxes of organic matter to adjacent
streams – thereby strongly impacting patterns of channel morphology, water flow, sedimentation, and habitat in rivers. As
part of a comprehensive investigation of riparian dynamics in coastal rain forest rivers of the Pacific Northwest (USA), we
examined riparian tree abundance (density, basal area, and biomass) and rates of production (basal area growth [BAI] and bole
wood biomass increase [P]) of seven common species – red alder (Alnus rubra), Sitka spruce (Picea sitchensis), bigleaf maple (Acer macrophyllum), western hemlock (Tsuga heterophylla), black cottonwood (Populus trichocarpa), vine maple (Acer circinatum) and willow (Salix spp.) – in the lowland floodplain of the Queets River (Olympic National Park), Washington. Measurements were made annually
for three years (1999 – 2001) in 16 permanent plots on three biophysical templates that formed a toposequence – active floodplain,
young terrace and mature terrace. Stem density was highest in the active floodplain (∼27,000 stems/ ha), decreasing in the
young terrace (∼2,700 stems /ha) and the mature terrace (∼500 stems/ha). Basal area and total stem biomass were lowest in
the active floodplain (∼16 m2/ha and ∼18 Mg dry weight/ha, respectively) and higher on the young terrace (∼32 m2/ha and ∼134
Mg dry weight/ha) and on the mature terrace (∼69 m2/ha and ∼540 Mg dry weight /ha). Total plot-scale BAI was not significantly
different among the physical templates with mean values ranging from approximately 1.4 (low terrace) to approximately 2.8
m2/ha/y (active floodplain). In contrast, P was significantly higher on the mature terrace (10.3 Mg/ha) than the active floodplain
(3.2 Mg/ha) but there was no significant difference between young terrace (6.5 Mg/ha) and mature terrace. For the entire Queets
River floodplain (57 km2 over 77 km of river length), the mature terrace contributed 81% of the total annual production (28,764 Mg) whereas the active
floodplain and young terrace accounted only for 5 and 14%, respectively. Overall, we show that riparian trees grow quickly
in this coastal Pacific Northwest system and that the older riparian forests on mature terraces are the main contributors
to stem production at the plot and floodplain scales for at least 350 years after stand initiation. This suggests that, in
combination with the rapid lateral migrations of many alluvial rivers, the older riparian forests on those terraces are important
and sustained sources of organic matter (especially large woody debris, LWD) that, over decades to centuries, shape the character
of coastal rivers in the Pacific Northwest. 相似文献
9.
Robert J. Naiman Robert E. Bilby Daniel E. Schindler James M. Helfield 《Ecosystems》2002,5(4):399-417
Pacific salmon (Oncorhynchus spp.) accumulate substantial nutrients in their bodies as they grow to adulthood at sea. These nutrients are carried to predominantly
oligotrophic lakes and streams, where they are released during and after spawning. Research over more than 3 decades has shown
that the annual deposition of salmon-borne marine-derived nutrients (MD-nutrients) is important for the productivity of freshwater
communities throughout the Pacific coastal region. However, the pathways and mechanisms for MD-nutrient transfer and accumulation
in freshwater and riparian ecosystems remain virtually unexplored, consequently, there are many uncertainties in this area.
This article addresses three related topics. First, we summarize recent advances in our understanding of the linkages among
MD-nutrients, freshwater (including riparian) ecosystems, and community dynamics by addressing the importance of MD-nutrients
to lakes and streams and by then reviewing large-scale and long-term processes in the atmosphere and ocean that govern variability
in salmon populations. Second, we evaluate the validity of the discoveries and their implications for active ecosystem management,
noting areas where extrapolation from these results still requires great caution. Finally, we outline five key research issues
where additional discoveries could greatly augment our understanding of the processes shaping the structure and dynamics of
salmon populations and the characteristics of their freshwater habitat and associated riparian zones. Collectively, the data
suggest that the freshwater portion of the salmon production system is intimately linked to the ocean. Moreover, for the system
to be sustainable, a holistic approach to management will be required. This holistic approach will need to treat climate cycles,
salmon, riparian vegetation, predators, and MD-nutrient flowpaths and feedbacks as an integrated system.
Received 3 July 2001; accepted 14 December 2001. 相似文献
10.