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91.
S. R. MORTON O. HOEGH‐GULDBERG D. B. LINDENMAYER M. HARRISS OLSON L. HUGHES M. T. McCULLOCH S. McINTYRE H. A. NIX S. M. PROBER D. A. SAUNDERS A. N. ANDERSEN M. A. BURGMAN E. C. LEFROY W. M. LONSDALE I. LOWE A. J. McMICHAEL J. S. PARSLOW W. STEFFEN J. E. WILLIAMS J. C. Z. WOINARSKI 《Austral ecology》2009,34(1):1-9
The need to improve environmental management in Australia is urgent because human health, well‐being and social stability all depend ultimately on maintenance of life‐supporting ecological processes. Ecological science can inform this effort, but when issues are socially and economically complex the inclination is to wait for science to provide answers before acting. Increasingly, managers and policy‐makers will be called on to use the present state of scientific knowledge to supply reasonable inferences for action based on imperfect knowledge. Hence, one challenge is to use existing ecological knowledge more effectively; a second is to tackle the critical unanswered ecological questions. This paper identifies areas of environmental management that are profoundly hindered by an inability of science to answer basic questions, in contrast to those areas where knowledge is not the major barrier to policy development and management. Of the 22 big questions identified herein, more than half are directly related to climate change. Several of the questions concern our limited understanding of the dynamics of marine systems. There is enough information already available to develop effective policy and management to address several significant ecological issues. We urge ecologists to make better use of existing knowledge in dialogue with policy‐makers and land managers. Because the challenges are enormous, ecologists will increasingly be engaging a wide range of other disciplines to help identify pathways towards a sustainable future. 相似文献
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97.
Asensio JL; Canada FJ; Bruix M; Gonzalez C; Khiar N; Rodriguez-Romero A; Jimenez-Barbero J 《Glycobiology》1998,8(6):569-577
The specific interaction of hevein with GlcNAc-containing oligosaccharides
has been analyzed by1H-NMR spectroscopy. The association constants for the
binding of hevein to a variety of ligands have been estimated from1H-NMR
titration experiments. The association constants increase in the order
GlcNAc-alpha(1-->6)-Man < GlcNAc < benzyl-beta-GlcNAc <
p-nitrophenyl-beta-GlcNAc < chitobiose < p-
nitrophenyl-beta-chitobioside < methyl-beta-chitobioside <
chitotriose. Entropy and enthalpy of binding for different complexes have
been obtained from van't Hoff analysis. The driving force for the binding
process is provided by a negative DeltaH0which is partially compensated by
negative DeltaS0. These negative signs indicate that hydrogen bonding and
van der Waals forces are the major interactions stabilizing the complex.
NOESY NMR experiments in water solution provided 475 accurate protein
proton-proton distance constraints after employing the MARDIGRAS program.
In addition, 15 unambiguous protein/carbohydrate NOEs were detected. All
the experimental constraints were used in a refinement protocol including
restrained molecular dynamics in order to determine the highly refined
solution conformation of this protein- carbohydrate complex. With regard to
the NMR structure of the free protein, no important changes in the protein
nOe's were observed, indicating that carbohydrate-induced conformational
changes are small. The average backbone rmsd of the 20 refined structures
was 0.055 nm, while the heavy atom rmsd was 0.116 nm. It can be deduced
that both hydrogen bonds and van der Waals contacts confer stability to the
complex. A comparison of the three-dimensional structure of hevein in
solution to those reported for wheat germ agglutinin (WGA) and hevein
itself in the solid state has also been performed. The polypeptide
conformation has also been compared to the NMR-derived structure of a
smaller antifungical peptide, Ac-AMP2.
相似文献
98.
IV Zlatkin M Schneider FJ de Bruijn LJ Forney PhD 《Journal of industrial microbiology & biotechnology》1996,17(3-4):219-227
Culturable bacteria from the deep subsurface (179 m) at Cerro Negro, New Mexico were isolated and characterized. The average number of viable aerobic bacteria was estimated to be 5×105g–1 of sediment, but only about 0.1% of these could be recovered on agar medium when incubated under aerobic conditions. Of 158 strains isolated from this depth, 92 were characterized by cellular fatty acid profiles (FAME), 36 by analysis of partial 16S rDNA sequences, and 44 by rep-PCR genome fingerprint analysis using three different sets of oligonucleotide primers (REP, BOX, or ERIC). These analyses showed the majority of isolates (67%) were Gram-positive bacteria and primarily members of genera with a high %G+C DNA. The remaining isolates were -subdivisionProteobacteria (19%) and members of the flavobacteria group (14%). The diversity indices based on these different methods of characterization were very high suggesting this subsurface habitat harbors a highly diverse microbial community. 相似文献
99.
Phylogenetic reconstruction of the Drosophila obscura group, on the basis of mitochondrial DNA 总被引:2,自引:0,他引:2
We have constructed restriction-site maps of the mtDNAs in 13 species and
one subspecies of the Drosophila obscura group. The traditional division of
this group into two subgroups (affinis and obscura) does not correspond to
the phylogeny of the group, which shows two well- defined clusters (the
Nearctic affinis and pseudoobscura subgroups) plus a very heterogeneous set
of anciently diverged species (the Palearctic obscura subgroup). The mtDNA
of Drosophila exhibits a tendency to evolve toward high A+T values. This
leads to a "saturation" effect that (1) begets an apparent decrease in the
rate of evolution as the time since the divergence of taxa increases and
(2) reduces the value that mtDNA restriction analysis has for the
phylogenetic reconstruction of Drosophila species that are not closely
related.
相似文献
100.
Changes in ionized calcium were studied in axons isolated from living squid by measuring absorbance of the Ca binding dye Arsenazo III using multiwavelength differential absorption spectroscopy. Absorption changes measured in situ were calibrated in vitro with media of ionic composition similar to axoplasm containing CaEGTA buffers. Calcium loads of 50-2,500 μmol/kg axoplasm were induced by microinjection, by stimulation in 112 mM Ca seawater, or by soaking in choline saline with 1-10 mM Ca. Over this range of calcium loading of intact axoplasm, the ionized calcium in the axoplasm rose about 0.6 nM/μM load. Similar loading in axons preteated with carbonyl cyanide 4- trifluoromethoxyphenylhydrazone (FCCP) to inhibit the mitochondrial proton gradient increased ionized calcium by 5-7 percent of the imposed load, i.e. 93-95 percent of the calcium load was buffered by a process insensitive to FCCP. This FCCP- insensitive buffer system was not saturated by the largest calcium loads imposed, indicating a capacity of at least several millimolar. Treatment of previously loaded axons with FCCP or apyrase plus cyanide produced rises in ionized calcium which could be correlated with the extent of the load. Analysis of results indicated that, whereas only 6 percent of the endogenous calcium in fresh axons is stored in the FCCP-sensitive (presumably mitochondrial) buffer system, about 30 percent of an imposed exogenous load in the range of 50-2,500 μM is taken up by this system. 相似文献