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1.
2.
Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O2 diffusion. Here we describeexperiments using O2 specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O2 concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O2 concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O2 concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O2 concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O2 fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O2 concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N2or air. Key words: Oxygen, root nodules, air spaces 相似文献
3.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
4.
Subunit structure of human and rat glutathione S-transferases 总被引:4,自引:0,他引:4
Y C Awasthi S V Singh 《Comparative biochemistry and physiology. B, Comparative biochemistry》1985,82(1):17-23
In rat tissues different forms of glutathione (GSH) S-transferases represent various dimeric combinations of at least four different classes of subunits categorized on the basis of their Mr values as seen on polyacrylamide gels. These subunit types represent heterogeneous populations and the actual number of subunits in rat GSH S-transferases may be far more than is known at present. Human GSH S-transferases arise from dimeric combinations of at least four immunologically and functionally distinct subunits which can be classified into three types, A (Mr 26,500), B (Mr 24,500) and C (Mr 22,500). There is evidence for considerable charge heterogeneity in each of these subunit types. 相似文献
5.
S S Singhal M Saxena H Ahmad S Awasthi A K Haque Y C Awasthi 《Archives of biochemistry and biophysics》1992,299(2):232-241
Glutathione S-transferase (GST) isozymes of human lung have been purified, characterized, quantitated, and, based on their structural and immunological profiles, identified with their respective classes. The tau-, mu-, and alpha-class GSTs represented 94, 3, and 3% activities of total human lung GSTs toward CDNB, respectively, and 60, 10, and 30% of total GST protein, respectively. Both the mu- and the alpha-class GSTs of human lung exhibited heterogeneity. The two mu-class GSTs of human lung had pI values of 6.5 and 6.25 and were differentially expressed in humans. Significant differences were seen between the kinetic properties of these two isozymes and also between the lung and liver mu-class GSTs. The alpha-class GST isozymes of lung resolved into three peaks during isoelectric focusing corresponding to pI values of 9.2, 8.95, and 8.8. All three alpha-class GSTs isozymes had blocked N-termini and were immunologically similar to human liver alpha-class GSTs. Peptide fingerprints generated by SV-8 protease digestion and CNBr cleavage indicated minor structural differences between the liver and the lung alpha-class GSTs. The three alpha-class GSTs of lung expressed glutathione peroxidase activities toward the hydroperoxides of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol, with Km values in the range of 22 to 87 microM and Vmax values in the range of 67-120 mol/mol/min, indicating the involvement of the alpha-class GSTs in the protection mechanisms against peroxidation. All three classes of lung GSTs expressed activities toward leukotriene A4 methyl ester and epoxy stearic acid but the mu-class GSTs had relatively higher activities toward these substrates. 相似文献
6.
S. P. Gautam A. K. Gupta R. Shrivastava M. Awasthi 《World journal of microbiology & biotechnology》1996,12(1):99-100
Two thermostable enzymes produced by the thermophilic fungus Paecilomyces varioti, a chitinase and laminarinase, were used to isolate protoplasts of a thermophilic fungus, Malbranchea sulfurea. The frequency of protoplast regeneration observed (35%) was considerably higher than that obtained using commercial lytic enzymes. 相似文献
7.
Thirty-one Brassica juncea accessions were screened at the cotyledon stage for resistance to four isolates of Peronospora parasitica. Isolates R1 and P003 were derived from crops of oilseed rape (B. napus ssp. oleifera) in the UK and isolates IP01 and IP02 were derived from crops of mustard (B. juncea) in India. B. napus cv. Ariana, which was used as a susceptible control for isolates from B. napus, was resistant to isolates from B. juncea. All, B. juncea accessions were resistant to isolates from B. napus except one accession which expressed moderate resistance to isolate P003. Five groups of B. juncea accessions with differential resistance were identified. Lines homogeneous for resistance were selected from seedling populations of accessions that exhibited a heterogeneous reaction to isolates from B. juncea. The differential resistance identified in the B. juncea-P. parasitica combination can be used as a foundation for future studies of the genetics of the host-pathogen interaction and for breeding for disease resistance. 相似文献
8.
Summary The increased downward mobility of phorate, quinalphos and carbofuran residues was detected in soil with increase in depth
of soil column whereas aldicarb was found to remain localised mainly in 0–7.5 cm and 7.5–15.0 cm layers. Persistence of organophosphate
insecticides was higher as compared to carbamates in all the soil layers. Residues of all the four insecticides got distributed
in all parts of okra plant through uptake but accumulated in higher amounts in fruits only.
Contribution No. 312/83 from I.I.H.R. Bangalore (India) 相似文献
9.
10.
Sita Awasthi Poonam Kakkar P. N. Viswanathan R. Bhardwaj 《Journal of neurochemistry》1991,57(1):277-281
Administration of phenobarbitone caused a marked increase in the capacity of rat brain microsomes to produce thiobarbituric acid-reactive substances in vitro. Enzymatic peroxidation of lipids was more affected than the nonenzymatic processes occurring in heat-inactivated preparations. Analysis of the phospholipid profile showed a drastic decrease in phosphatidylcholine and total phospholipid contents in the exposed animals, but about a fivefold increase in the lysophosphatidylcholine fraction. Data for in vivo incorporation of [14C]choline showed a similar pattern of high radioactivity in lysolecithin. The increase in lipid peroxidation could be related to the higher level of lysolecithin and the accompanying structural and functional changes in microsomes resulting from the neurotoxic effects of phenobarbitone. 相似文献