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41.
The critical thermal maxima (TMAX) of threadfin shad Dorosoma petenense exposed to standardized stress (30 s handling in a dip‐net), simulating stressors endured during fish loading before transport, were measured over a range of holding temperatures (15, 20 and 25° C). Dorosoma petenense TMAX showed a significant thermal effect, displaying mean ±s.d . critical thermal maxima of 26·5 ± 1·6, 30·9 ± 1·2 and 33·3 ± 1·4° C, when tested at temperatures of 15, 20 and 25° C, respectively. Dorosoma petenense TMAX levels were also affected by stress, with handled fish showing significantly lower values than control fish exposed to 15 (mean ±s.d . TMAX = 25·6 ± 2·0° C), 20 (27·6 ± 2·8° C) and 25° C (32·0 ± 2·6° C). In addition to providing basic information on D. petenense thermal tolerance, experimental results suggest that fishery managers should consider the whole suite of potential stressors, such as air exposure during handling and fish loading, when developing management criteria. 相似文献
42.
The restriction enzyme TaqI digests 0.2% of the genomic DNA from the
grasshopper Caledia captiva to a family of sequences 168 bp in length
(length of consensus sequence). The sequence variation of this "Taq family"
of repeat units was examined among four races from C. captiva to assay the
pattern of evolution within this highly repeated DNA. The Taq-family
repeats are located in C-banded heterochromatin on at least one member of
each homologous pair of chromosomes; the locations range from centromeric
to telomeric. Thirty-nine cloned repeats isolated from two population 1A
individuals along with 11 clones from seven populations taken from three of
the races demonstrated sequence variation at 72 positions. Pairwise
comparisons of the cloned repeats, both within an individual and between
different races, indicate that levels of intraspecific divergence, as
measured by reproductive incompatibility, do not correlate with sequence
divergence among the 168-bp repeats. A number of subsequences within the
repeat remain unchanged among all 50 clones; the longest of these is 18 bp.
That the same 18-bp subsequence is present in all clones examined is a
finding that departs significantly (P less than 0.01) from what would be
expected to occur at random. Two other cloned repeats, from a
reproductively isolated race of C. captiva, have sequences that show 56%
identity with this 18-bp conserved region. An analysis showed that the
frequency of occurrence of an RsaI recognition site within the 168- bp
repeat in the entire Taq family agreed with that found in the cloned
sequences. These data, along with a partial sequence for the entire Taq
family obtained by sequencing uncloned repeats, suggest that the consensus
sequence from the cloned copies is representative of this highly repeated
family and is not a biased sample resulting from the cloning procedure. The
18-bp conserved sequence is part of a 42-bp sequence that possesses dyad
symmetry typical of protein-binding sites. We speculate that this may be
significant in the evolution of the Taq family of sequences.
相似文献
43.
44.
Ashley D. Ficke Christopher A. Myrick Lara J. Hansen 《Reviews in Fish Biology and Fisheries》2007,17(4):581-613
Despite uncertainty in all levels of analysis, recent and long-term changes in our climate point to the distinct possibility
that greenhouse gas emissions have altered mean annual temperatures, precipitation and weather patterns. Modeling efforts
that use doubled atmospheric CO2 scenarios predict a 1–7°C mean global temperature increase, regional changes in precipitation patterns and storm tracks,
and the possibility of “surprises” or sudden irreversible regime shifts. The general effects of climate change on freshwater
systems will likely be increased water temperatures, decreased dissolved oxygen levels, and the increased toxicity of pollutants.
In lotic systems, altered hydrologic regimes and increased groundwater temperatures could affect the quality of fish habitat.
In lentic systems, eutrophication may be exacerbated or offset, and stratification will likely become more pronounced and
stronger. This could alter food webs and change habitat availability and quality. Fish physiology is inextricably linked to
temperature, and fish have evolved to cope with specific hydrologic regimes and habitat niches. Therefore, their physiology
and life histories will be affected by alterations induced by climate change. Fish communities may change as range shifts
will likely occur on a species level, not a community level; this will add novel biotic pressures to aquatic communities.
Genetic change is also possible and is the only biological option for fish that are unable to migrate or acclimate. Endemic
species, species in fragmented habitats, or those in east–west oriented systems will be less able to follow changing thermal
isolines over time. Artisanal, commercial, and recreational fisheries worldwide depend upon freshwater fishes. Impacted fisheries
may make it difficult for developing countries to meet their food demand, and developed countries may experience economic
losses. As it strengthens over time, global climate change will become a more powerful stressor for fish living in natural
or artificial systems. Furthermore, human response to climate change (e.g., increased water diversion) will exacerbate its
already-detrimental effects.
Model predictions indicate that global climate change will continue even if greenhouse gas emissions decrease or cease. Therefore,
proactive management strategies such as removing other stressors from natural systems will be necessary to sustain our freshwater
fisheries. 相似文献
45.
Two soluble glycosyltransferases glycosylate less efficiently in vivo than their membrane bound counterparts 总被引:1,自引:1,他引:1
Zhu G; Allende ML; Jaskiewicz E; Qian R; Darling DS; Worth CA; Colley KJ; Young WW Jr 《Glycobiology》1998,8(8):831-840
Many Golgi glycosyltransferases are type II membrane proteins which are
cleaved to produce soluble forms that are released from cells. Cho and
Cummings recently reported that a soluble form of alpha1, 3-
galactosyltransferase was comparable to its membrane bound counterpart in
its ability to galactosylate newly synthesized glycoproteins (Cho,S.K. and
Cummings,R.D. (1997) J. Biol. Chem., 272, 13622-13628). To test the
generality of their findings, we compared the activities of the full length
and soluble forms of two such glycosyltransferases, ss1,4
N-Acetylgalactosaminyltransferase (GM2/GD2/ GA2 synthase; GalNAcT) and beta
galactoside alpha2,6 sialyltransferase (alpha2,6-ST; ST6Gal I), for
production of their glycoconjugate products in vivo . Unlike the full
length form of GalNAcT which produced ganglioside GM2 in transfected cells,
soluble GalNAcT did not produce detectable GM2 in vivo even though it
possessed in vitro GalNAcT activity comparable to that of full length
GalNAcT. When compared with cells expressing full length alpha2,6-ST, cells
expressing a soluble form of alpha2,6-ST contained 3-fold higher
alpha2,6-ST mRNA levels and secreted 7-fold greater alpha2,6-ST activity as
measured in vitro , but in striking contrast contained 2- to 4-fold less of
the alpha2,6-linked sialic acid moiety in cellular glycoproteins in vivo .
In summary these results suggest that unlike alpha1,3-galactosyltransferase
the soluble forms of these two glycosyltransferases are less efficient at
glycosylation of membrane proteins and lipids in vivo than their membrane
bound counterparts.
相似文献
46.
R H Durland T S Rao G R Revankar J H Tinsley M A Myrick D M Seth J Rayford P Singh K Jayaraman 《Nucleic acids research》1994,22(15):3233-3240
The goal of this study was to address antiparallel triplex formation at duplex targets that do not conform to a strict oligopurine.oligopyrimidine motif. We focused on the ability of natural bases and base analogs incorporated into oligonucleotide third strands to bind to so-called CG inversions. These are sites where a cytosine base is present in an otherwise purine-rich strand of a duplex target. Using a 26-base-triplet test system, we found that of the standard bases, only thymine (T) shows substantial binding to CG inversions. This is quantitatively similar to the report of Beal and Dervan [Science (1991), 251, 1360-1363]. Binding to CG inversions was only slightly weaker than binding to AT base pairs. Binding of T to CG inversions was also evaluated in two other sequences, with qualitatively similar results. Six different analogs of thymine were also tested for binding to CG inversions and AT base pairs. Significant changes in affinity were observed. In particular, 5-fluoro-2'-deoxyuridine was found to increase affinity for CG inversions as well as for AT base pairs. Studies with oligonucleotides containing pyridin-2-one or pyridin-4-one suggest that thymine O4 plays a critical role in the T.CG interaction. Possible models to account for these observations are discussed. 相似文献
47.
Frantz L. Jean-Francois Jian Dai Lu Yu Alissa Myrick Eric Rubin Piotr G. Fajer Likai Song Huan-Xiang Zhou Timothy A. Cross 《Journal of molecular biology》2014
MgtR, a highly hydrophobic peptide expressed in Salmonella enterica serovar Typhimurium, inhibits growth in macrophages through binding to the membrane protein MgtC that has been identified as essential for replication in macrophages. While the Mycobacterium tuberculosis MgtC is highly homologous to its S. Typhi analogue, there does not appear to be an Mtb homologue for MgtR, raising significant pharmacological interest in this system. Here, solid-state NMR and EPR spectroscopy in lipid bilayer preparations were used to demonstrate the formation of a heterodimer between S. Typhi MgtR and the transmembrane helix 4 of Mtb MgtC. Based on the experimental restraints, a structural model of this heterodimer was developed using computational techniques. The result is that MgtR appears to be ideally situated in the membrane to influence the functionality of MgtC. 相似文献
48.
Using cultured cells from bovine and rat aortas, we have examined the possibility that endothelial cells might regulate the growth of vascular smooth muscle cells. Conditioned medium from confluent bovine aortic endothelial cells inhibited the proliferation of growth-arrested smooth muscle cells. Conditioned medium from exponential endothelial cells, and from exponential or confluent smooth muscle cells and fibroblasts, did not inhibit smooth muscle cell growth. Conditioned medium from confluent endothelial cells did not inhibit the growth of endothelial cells or fibroblasts. In addition to the apparent specificity of both the producer and target cell, the inhibitory activity was heat stable and not affected by proteases. It was sensitive flavobacterium heparinase but not to hyaluronidase or chondroitin sulfate ABC lyase. It thus appears to be a heparinlike substance. Two other lines of evidence support this conclusion. First, a crude isolate of glycosaminoglycans (TCA-soluble, ethanol-precipitable material) from endothelial cell-conditioned medium reconstituted in 20 percent serum inhibited smooth muscle cell growth; glycosaminoglycans isolated from unconditioned medium (i.e., 0.4 percent serum) had no effect on smooth muscle cell growth. No inhibition was seen if the glycosaminoglycan preparation was treated with heparinase. Second, exogenous heparin, heparin sulfate, chondroitin sulfate B (dermatan sulfate), chondroitin sulfate ABC, and hyaluronic acid were added to 20 percent serum and tested for their ability to inhibit smooth muscle cell growth. Heparin inhibited growth at concentrations as low as 10 ng/ml. Other glycosaminoglycans had no effect at doses up to 10 μg/ml. Anticoagulant and non- anticoagulant heparin were equally effective at inhibiting smooth muscle cell growth, as they were in vivo following endothelial injury (Clowes and Karnovsk. Nature (Lond.). 265:625-626, 1977; Guyton et al. Circ. Res. 46:625-634, 1980), and in vitro following exposure of smooth muscle cells to platelet extract (Hoover et al. Circ. Res. 47:578-583, 1980). We suggest that vascular endothelial cells may secrete a heparinlike substance in vivo which may regulate the growth of underlying smooth muscle cells. 相似文献
49.
Intercalation of proflavine and a platinum derivative of proflavine into double-helical Poly(A) 下载免费PDF全文
The equilibria and kinetics of the interactions of proflavine (PR) and its platinum-containing derivative [PtCl(tmen)(2)HNC(13)H(7)(NHCH(2)CH(2))(2)](+) (PRPt) with double-stranded poly(A) have been investigated by spectrophotometry and Joule temperature-jump relaxation at ionic strength 0.1 M, 25 degrees C, and pH 5.2. Spectrophotometric measurements indicate that base-dye interactions are prevailing. T-jump experiments with polarized light showed that effects due to field-induced alignment could be neglected. Both of the investigated systems display two relaxation effects. The kinetic features of the reaction are discussed in terms of a two-step series mechanism in which a precursor complex DS(I) is formed in the fast step, which is then converted to a final complex in the slow step. The rate constants of the fast step are k(1) = (2.5 +/- 0.4) x 10(6) M(-1) s(-1), k(-1) = (2.4 +/- 0.1) x 10(3) s(-1) for poly(A)-PR and k(1) = (2.3 +/- 0.1) x 10(6) M(-1) s(-1), k(-1) = (1.6 +/- 0.2) x 10(3) s(-1) for poly(A)-PRPt. The rate constants for the slow step are k(2) = (4.5 +/- 0.5) x 10(2) s(-1), k(-2) = (1.7 +/- 0.1) x 10(2) s(-1) for poly(A)-PR and k(2) = 9.7 +/- 1.2 s(-1), k(-2) = 10.6 +/- 0.2 s(-1) for poly(A)-PRPt. Spectrophotometric measurements yield for the equilibrium constants and site size the values K = (4.5 +/- 0.1) x 10(3) M(-1), n = 1.3 +/- 0.5 for poly(A)-PR and K = (2.9 +/- 0.1) x 10(3) M(-1), n = 2.3 +/- 0.6 for poly(A)-PRPt. The values of k(1) are similar and lower than expected for diffusion-limited reactions. The values of k(-1) are similar as well. It is suggested that the formation of DS(I) involves only the proflavine residues in both systems. In contrast, the values of k(2) and k(-2) in poly(A)-PRPt are much lower than in poly(A)-PR. The results suggest that in the complex DS(II) of poly(A)-PRPt both proflavine and platinum residues are intercalated. In addition, a very slow process was detected and ascribed to the covalent binding of Pt(II) to the adenine. 相似文献
50.
H?Bukulmez AL?Matthews CM?Sullivan C?Chen MJ?Kraay RC?Elston RW?Moskowitz VM?Goldberg ML?WarmanEmail author 《Arthritis research & therapy》2005,8(1):R25
In order to determine whether there is a genetic component to hip or knee joint failure due to idiopathic osteoarthritis (OA),
we invited patients (probands) undergoing hip or knee arthroplasty for management of idiopathic OA to provide detailed family
histories regarding the prevalence of idiopathic OA requiring joint replacement in their siblings. We also invited their spouses
to provide detailed family histories about their siblings to serve as a control group. In the probands, we confirmed the diagnosis
of idiopathic OA using American College of Rheumatology criteria. The cohorts included the siblings of 635 probands undergoing
total hip replacement, the siblings of 486 probands undergoing total knee replacement, and the siblings of 787 spouses. We
compared the prevalence of arthroplasty for idiopathic OA among the siblings of the probands with that among the siblings
of the spouses, and we used logistic regression to identify independent risk factors for hip and knee arthroplasty in the
siblings. Familial aggregation for hip arthroplasty, but not for knee arthroplasty, was observed after controlling for age
and sex, suggesting a genetic contribution to end-stage hip OA but not to end-stage knee OA. We conclude that attempts to
identify genes that predispose to idiopathic OA resulting in joint failure are more likely to be successful in patients with
hip OA than in those with knee OA. 相似文献