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1.
2.
Ni powders coated by deposition of TiO2 or controlled oxidation to NiO develop substantial resistance to corrosion. Chymotrypsin immobilized to these coated Ni supports shows very high stability of activity on storage. Chymotrypsin immobilized by adsorption and glutaraldehyde crosslinking was fairly rapidly eluted under operational conditions in the presence of substrate. If 3-aminopropyltriethoxysilane (APS) was used to produce a covalent linkage, desorption of enzyme still occurred because of relatively unstable bonding of the silane to the oxide surface. A more stable attachment was produced by joining together many silane links with a layer of polyglutaraldehyde. The mechanism of action of APS as a coupling agent under these conditions is discussed. gamma-Fe2O3, and particularly a Mn-Zn ferrite, are suitable magnetic support materials available with smaller particle sizes. Particles below 1 mum give the expected higher specific activities of immobilized enzymes. 相似文献
3.
Influence of chloroplast development on the activation of the diphenyl ether herbicide acifluorfen-methyl 总被引:2,自引:2,他引:0 下载免费PDF全文
The activity of acifluorfen-methyl (AFM); methyl 5-(2-chloro-4-[trifluoromethyl] phenoxy)-2-nitrobenzoate in excised cucumber cotyledons (Cucumis sativus L.) was examined. AFM induced membrane disruption, was significantly greater when etiolated cotyledons were illuminated 16 hours at 150 microeinsteins per square meter per second photosynthetically active radiation versus incubation under illumination of 4-fold greater intensity. These results were unexpected since the loss of membrane integrity is initiated by photodynamic reactions. Untreated, etiolated cotyledons were not able to accumulate chlorophyll under the higher light intensity while control and herbicide treated cotyledons greened significantly under the lower intensity illumination suggesting that some process associated with greening stimulated AFM activity. Inhibition of greening by cycloheximide also reduced AFM activity. Intermittent lighting induced greening in AFM treated cotyledons without causing any detectable loss of plasmalemma integrity. Utilization of this system for pretreatment of cotyledons prior to continuous illumination revealed that activity was greater when tissue was greened in the presence of AFM than when herbicide treatments were made after a greening period of the same duration. The results indicate that the pigments in situ in etiolated tissue are sufficient, without greening, to initiate membrane disruption by AFM. However, greening increases the herbicidal efficacy greatly. Furthermore, the stimulation appears to be due to specific interactions between AFM and the developing plastid and is not attributable solely to an increase in endogenous photosensitizers. 相似文献
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Summary For numerical solution of the reaction-mass transfer equations for immobilised biocatalysts it may be better to start integration at the particle surface and proceed inwards: calculations are targetted on the region to which practically interesting changes are often confined (because concentrations are effectively zero in the interior); and during iterative solution wrong initial estimates may be rejected after detecting anomalies early in the integration.Symbols Cb
substrate concentration in bulk (mol m–3)
- c
dimensionless substrate concentration (C/Cb) (-)
- De
effective diffusion coefficient (m2s–1)
- Da
Damkohler number (V.ro
2/De.Ks) (-)
- Ks
substrate concentration kinetic coefficient (mol m–3)
- ke
external mass transfer coefficient (ms–1)
- ro
bead radius (m)
- Sh
Sherwood number (ke.ro/De) (-)
- V
maximum rate per unit volume in beads (mol m–3s–1)
- x
dimensionless distance from bead centre (r/ro) (-)
-
dimensionless kinetic coefficient (Ks/Cb) (-)
- o
effectiveness factor (-) 相似文献
8.
Rhodocybe pulchrisperma is described as a new species of Agaricales from North America. It belongs in section Rhodocybe due to the brightly colored pseudocystidia and lack of clamp connections. The very large, handsomely ornamented basidiospores distinguish this species from others in the section. A key to taxa from Florida, Papua New Guinea, and India that exhibit similar features is presented. 相似文献
9.
MAJOR CLADES OF THE ANGIOSPERMS 总被引:2,自引:0,他引:2
ROLF DAHLGREN KÅRE BREMER 《Cladistics : the international journal of the Willi Hennig Society》1985,1(4):349-368
Abstract— Our knowledge of fundamental angiosperm interrelationships is still very incomplete. The absence of a narrowly circumscribed gymnosperm outgroup, ideally the sister group, makes character evaluation, necessary for a cladistic analysis, difficult. According to current views the superorder Magnoliiflorae with a number of other groups, for example the monocotyledons, may represent a complex of families near the base of the angiosperms. Interrelationships of groups within the monocotyledons are much better understood than those between groups within the dicotyledons. A cladogram of monocotyledon orders based on earlier work by R. Dahlgren, H. T. Clifford, and F. N. Rasmussen is presented. A data matrix for a sample of the angiosperms with 61 characters for 49 taxa, mostly magnoliifloran and related families, is presented. The characters are polarized mainly according to the current view that the primitive angiosperm morphotype is a woody dicotyledon with strobiloid flowers. As an alternative the matrix is adjusted following W. C. Burger's conjecture that the primitive angiosperm was a herbaceous monocotyledon with trimerous flowers. Both matrices were run in a computerized parsimony analysis, resulting in numerous equally parsimonious solutions. This result is illustrative of the great homoplasy in the available character information, and also of how little actually is known about fundamental angiosperm interrelationships or phylogeny. 相似文献
10.
Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution 总被引:1,自引:0,他引:1
In order to study the relationships among mammalian alpha-globin genes, we
have determined the sequence of the 3' flanking region of the human alpha 1
globin gene and have made pairwise comparisons between sequenced
alpha-globin genes. The flanking regions were examined in detail because
sequence matches in these regions could be interpreted with the least
complication from the gene duplications and conversions that have occurred
frequently in mammalian alpha-like globin gene clusters. We found good
matches between the flanking regions of human alpha 1 and rabbit alpha 1,
human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and
horse alpha 1 and goat II alpha. These matches were used to align the
alpha-globin genes in gene clusters from different mammals. This alignment
shows that genes at equivalent positions in the gene clusters of different
mammals can be functional or nonfunctional, depending on whether they
corrected against a functional alpha-globin gene in recent evolutionary
history. The number of alpha-globin genes (including pseudogenes) appears
to differ among species, although highly divergent pseudogenes may not have
been detected in all species examined. Although matching sequences could be
found in interspecies comparisons of the flanking regions of alpha- globin
genes, these matches are not as extensive as those found in the flanking
regions of mammalian beta-like globin genes. This observation suggests that
the noncoding sequences in the mammalian alpha-globin gene clusters are
evolving at a faster rate than those in the beta-like globin gene clusters.
The proposed faster rate of evolution fits with the poor conservation of
the genetic linkage map around alpha-globin gene clusters when compared to
that of the beta-like globin gene clusters. Analysis of the 3' flanking
regions of alpha-globin genes has revealed a conserved sequence
approximately 100-150 bp 3' to the polyadenylation site; this sequence may
be involved in the expression or regulation of alpha-globin genes.
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