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11.
Biotechnology Letters - 相似文献
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F J Joubert G S Townshend D P Botes 《Hoppe-Seyler's Zeitschrift für physiologische Chemie》1983,364(12):1717-1726
Two phospholipases A2, CM-I and CM-II, were purified from Bitis nasicornis venom by gel filtration on Sephadex G-50, followed by ion-exchange chromatography on CM-cellulose. Both enzymes comprise 119 amino acids, including 12 half-cystine residues. The primary structure of CM-II has been elucidated. The sequence and invariant amino-acid residues of CM-II resemble those of phospholipases A2 from other venoms of Viperidae and Crotalidae (Group II) snake venoms. CM-I and CM-II both contain a single histidine residue which is probably located at the active centre (histidine-47). CM-II are relatively non-toxic. 相似文献
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L A Engel H Menkes L D Wood G Utz J Joubert P T Macklem 《Journal of applied physiology》1973,35(1):9-17
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Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans 总被引:13,自引:3,他引:10
Recent studies of mitochondrial DNA (mtDNA) variation in mammals and
Drosophila have shown an excess of amino acid variation within species
(replacement polymorphism) relative to the number of silent and replacement
differences fixed between species. To examine further this pattern of
nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5
genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans.
Of interest are the frequency spectra of silent and replacement
polymorphisms, and potential variation among genes and taxa in the
departures from neutral expectations. The Drosophila ND3 and ND5 data show
no significant excess of replacement polymorphism using the
McDonald-Kreitman test. These data are in contrast to significant
departures from neutrality for the ND3 gene in mammals and other genes in
Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however,
both Drosophila and human mtDNA show very significant excesses of amino
acid polymorphism. Silent polymorphisms at ND5 show a significantly higher
variance in frequency than replacement polymorphisms, and the latter show a
significant skew toward low frequencies (Tajima's D = -1.954). These
patterns are interpreted in light of the nearly neutral theory where mildly
deleterious amino acid haplotypes are observed as ephemeral variants within
species but do not contribute to divergence. The patterns of polymorphism
and divergence at charge-altering amino acid sites are presented for the
Drosophila ND5 gene to examine the evolution of functionally distinct
mutations. Excess charge-altering polymorphism is observed at the carboxyl
terminal and excess charge-altering divergence is detected at the amino
terminal. While the mildly deleterious model fits as a net effect in the
evolution of nonrecombining mitochondrial genomes, these data suggest that
opposing evolutionary pressures may act on different regions of
mitochondrial genes and genomes.
相似文献
18.
P Birman F Bai-Grenier D Joubert 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1991,312(6):241-245
In order to assess whether a chronic treatment with a dopamine agonist, CV205-502, could modulate anterior pituitary epidermal growth factor (EGF) binding sites, female Wistar rats were treated or not (controls) with CV205-502 0.25 mg/kg/day sc for 8 days. This treatment significantly reduced rats' pituitary weight and plasma prolactin levels when compared to controls (weight: 10.4 +/- 0.1 vs 11.1 +/- 0.1 mg, p less than 0.01; prolactin: 1.2 +/- 0.2 vs 4.9 +/- 0.5 ng/ml, p less than 0.01). These decreases were associated with a significant stimulation of the number of pituitary EGF binding sites Bmax: 16.7 +/- 2.3 vs 11.3 +/- 1.9 fmoles/mg proteins, p less than 0.01) with no significant effect on their affinity (Kd: 0.94 +/- 0.17 vs 0.95 +/- 0.14 nM). Therefore, the modulation of pituitary EGF binding sites might be one of the mechanisms by which the dopamine agonist, CV205-502, exerts its pharmacological effects on hormonal secretions and/or cell multiplication in the pituitary. 相似文献
19.
Biotinylated derivative of a human brain lectin: synthesis and use in affinoblotting for endogenous ligand studies 总被引:3,自引:0,他引:3
Coupling of biotin to an endogenous lectin yields a probe which can be used for selective nonradioactive detection of complementary endogenous ligands. To exemplify practical applications of this type of compounds, we have synthesized and characterized a biotinylated derivative of a beta-galactoside-specific human brain lectin. Proteins which bind this lectin can be located on nitrocellulose sheets after electrophoretic transfer from gradient polyacrylamide gels, by sequential incubation with biotinylated probes and streptavidin-peroxidase, with visualization by an insoluble reaction product (affinoblotting). Biotinylated galactoside-binding plant lectins were used in the same way to visualize human brain glycoproteins, and their binding specificity was compared with that of human brain lectin. The results obtained by means of these different probes showed the usefulness of the endogenous lectin derivative to actually identify its endogenous partners. Thus this approach may find extended applications in the study of biological activities of vertebrate lectins in homologous systems, i.e., with lectins and ligands coming from the same tissue origin. 相似文献
20.
The anation reaction of aquopentaamminecobalt(III) by acetate has been studied in the temperature range 60–80°C and acidity range 1.0 ≦ pH ≦ 5.5 for total acetate concentrations ≦ 0.5 M and at ionic strength 1.0 M. The anation by acetic acid follows second-order kinetics (k0), whereas the kinetic results for the anation by acetate (Q1, k1) provide evidence for the formation of an ion-pair with the complex ion. Typical experimental results at 70°C are k0 = 5.33 X 10−5 M−1 sec−1, Q1 = 5.87 M−1 and k1 = 1.46 X 10−4sec−1. The activation parameters for the different reaction paths are reported and the results discussed with reference to various other anation reactions of Co(III) complexes. 相似文献