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81.
The exopolysaccharide (EPS) of avirulentXanthomonas campestris pv.Malvacearum race-32 did not contain the watersoaking (WS)— inducing factor but contained necrotic reaction (NR)-inducing factor and induced
NR on resistant cotton (cv. 101-102B) on which the viable cells of the same avirulent race-32 produced hypersensitive reaction
(HR). NR and HR were differentiated on the basis of the induction period required, visible reaction on infiltrated areas,
bacterial constituents or metabolite responsible, involvement of host constituent during these reactions and its chemical
inhibition. Pre and/or challenge inoculation of EPS of avirulent race-32 (3 mg per infiltration or lesion) in susceptible
or resistant cotton cultivars, on pre-and/or post-infiltrated (0–8 h) exponential-phase culture of virulent race-32 inhibited
the WS and/or HR of the virulent race in susceptible or resistant cotton. 相似文献
82.
Photoreactivation of UV-irradiated DSNA with phr A photolyase from Escherichia coli was studied in the presence of yeast RNA. Mixing of RNA with UV-irradiated DNA before its treatment with photolyase inhibited the photoreactivation of DNA. Denatured (by sonication) RNA was found to be more effective in blocking photolyase action. Agarose gel electrophoresis experiments suggest that this inhibition of photoreactivation is due to interference in the binding of photolyase with UV-irradiated DNA by yeast RNA. 相似文献
83.
Effect of oestradiol was studied on the angiotensin converting enzyme (ACE)--a component of renin angiotensin system, in oviduct of immature quails of 15 days of age. ACE was studied in whole oviduct, magnum, shell gland and the glandular epithelium of magnum and shell gland. It was found that whole oviduct had a significantly higher level of ACE in control than those treated with exogenous estrogen at three dose levels (200, 400 or 600 micrograms). ACE contents of whole muscle and glandular epithelium did not differ but magnum had higher ACE level than the shell gland. Results are explained on the basis of functional role of oviductal parts. 相似文献
84.
K Marumo L Lindqvist N Verma A Weintraub P R Reeves A A Lindberg 《European journal of biochemistry》1992,204(2):539-545
A two-step enzymatic synthesis of dTDP-L-rhamnose is developed using enzymes from sonicated extracts of cultures of Escherichia coli K12 strains harboring plasmids containing different parts of the rfb gene cluster of Salmonella enterica LT2. The intermediate dTDP-6-deoxy-D-xylo-4-hexulose was isolated after a 1-h reaction, using only dTDP-D-glucose and dTDP-D-glucose 4,6-dehydratase, followed by protein precipitation and desalting by gel chromatography (yield 89%). In a two-step reaction using dTDP-D-glucose and dTDP-D-glucose 4,6-dehydratase in the first step, and with NADPH, dTDP-6-deoxy-D-xylo-4-hexulose 3,5-epimerase and NADPH:dTDP-6-deoxy-L-lyxo-4-hexulose-4-reductase in the second hour of incubation, the dTDP-D-glucose was fully converted to dTDP-L-rhamnose. The hexoses of both products were identified by mass spectroscopy. The molar yield of dTDP-L-rhamnose, after protein precipitation, anion-exchange chromatography and desalting by gel chromatography, was 62%, corresponding to more than 150 mg, starting from 250 mg of dTDP-D-glucose. When stored lyophilysed under nitrogen, these products were found to be stable for several months. Both dTDP-6-deoxy-D-xylo-4-hexulose and dTDP-L-rhamnose have light absorption maxima at 267 nm, with molar absorption coefficients close to that of dTMP. However, the absorption coefficient of dTDP-6-deoxy-D-xylo-4-hexulose at the absorption maximum of 320 nm (specific for sugars containing keto groups) was found to be approximately 20% higher than values presented earlier. Furthermore, an HPLC technique is presented for determining the net activity of dTDP-6-deoxy-D-xylo-4-hexulose 3,5-epimerase and NADPH:dTDP-6-deoxy-L-lyxo-4-hexulose-4-reductase, based on separation of dTDP-6-deoxy-D-xylo-4-hexulose and dTDP-L-rhamnose. The HPLC technique is also suitable for determination of all the nucleotide components involved in the synthesis. 相似文献
85.
Monica I. Masana Jose A. Bitran John K. Hsiao William Z. Potter 《Journal of neurochemistry》1992,59(1):200-205
In vivo microdialysis of cyclic AMP from prefrontal cortex complemented by ex vivo measures was used to investigate the possibility that lithium produces functional changes in G proteins that could account for its effects on adenylate cyclase activity. Four weeks of lithium administration (serum lithium concentration of 0.85 +/- 0.05 mM; n = 11) significantly increased the basal cyclic AMP content in dialysate from prefrontal cortex of anesthetized rats. Forskolin infused through the probe increased dialysate cyclic AMP, but the magnitude of this increase was unaffected by chronic lithium administration. Inactivation of the inhibitory guanine nucleotide binding protein Gi with pertussis toxin increased dialysate cyclic AMP in control rats, as did stimulation with cholera toxin (which activates the stimulatory guanine nucleotide binding protein Gs). The effect of pertussis toxin was abolished following chronic lithium, whereas the increase in cyclic AMP after cholera toxin was enhanced. In vitro pertussis toxin-catalyzed ADP ribosylation of alpha i (and alpha o) was increased by 20% in prefrontal cortex from lithium-treated rats, but the alpha i and alpha s contents (as determined by immunoblot) as well as the cholera toxin-catalyzed ADP ribosylation of alpha s were unchanged. Taken together, these results suggest that chronic lithium administration may interfere with the dissociation of Gi into its active components and thereby remove a tonic inhibitory influence on adenylate cyclase, with resultant enhanced basal and cholera toxin-stimulated adenylate cyclase activity. 相似文献
86.
The symbiotic root nodule, an organ formed on leguminous plants, is a product of successful interactions between the host plant and the soil bacteria, Rhizobium spp. Plant hormones play an important role in the genesis of this organ. The hormonal balance appears to be modulated by the signals produced by bacteria. Many host genes induced during nodule organogenesis and the symbiotic state have been identified and characterized from several legumes. These genes encode nodule-specific proteins (nodulins) which perform diverse functions in root nodule development and metabolism. Formation of a subcellular compartment housing the bacteria is essential to sustain the symbiotic state, and several nodulins are involved in maintaining the integrity and function of this compartment. The bacteroid enclosed in the perbacteroid membrane behaves as an 'organelle,'completely dependent on the host for all its requirements for carbon, nitrogen and other essential elements. Thus it seems likely that the nodulins in the peribacteroid membrane perform specific transport functions. While the function of a few other nodulins is known (e.g. nodulin-100, nodulin-35), a group of uncharacterized nodulins exists in soybean root nodules. These nodulins share structural similarities and seem to have been derived from a common ancestor. Induction of nodulin genes occurs prior to and independent of nitrogen fixation, and thus is a prelude to symbiosis. Although some of the early nodulin genes are induced prior to or during infection, induction of late nodulins requires endocytotic release of bacteria. 相似文献
87.
Flexibility in the donor substrate specificity of {beta} 1,4-galactosyltransferase: application in the synthesis of complex carbohydrates 总被引:8,自引:5,他引:3
Biosynthetically, bovine N-acetylglucosainine ß 1,4-galacto-syltransferase(GalT) catalyses the transfer of galactosyl residues from UDP-Galto the 4-position of GlcNAc units, resulting in the productionof N-acetyllactosamine sequences. UDP-Glc and UDP-GalNAc werealso found to act as donors for this enzyme, allowing the preparationof ßGlc(14)-ßGlcNAc and ßGalNAc(14)ßGlcNActerminating structures on the milligram scale. GalT could thusbe used to add ßGalNAc to ßGlcNAc(12)Manterminating structures, converting them to the ßGalNAc(14)ßGlcNAc(12)Mansequences found on glycoprotein hormones. GalT did not transferGlcNAc residues from UDP-GlcNAc, but it could utilize UDP-GlcNH2as a donor. Synthesis of ßGlcNAc(14)ßGlcNAcsequences could therefore be accomplished by transfer of GlcNH2from its UDP derivative, followed by N-acetylation of the productamino-disaccharide using acetic anhydride in methanol. The productsof the enzymatic reactions were characterized by 1H-NMR-spectroscopyand fast-atom bombardment mass spectrometry. This work expandsthe scope of the combined chemical-enzymatic synthesis of complexcarbohydrates, using glycosyltrans-ferases, to the productionof oligosaccharides different from those for which these enzymeswere designed. These unnatural reactions should find applicationin glycoprotein and glycolipid remodelling. galactosyltransferase chemica1-enzymatic synthesis of oligosaccharides oligosaccharide analogues sugar-nucleotide analogues carbohydrate remodelling 相似文献
88.
In vitro absorption of nutrients like glucose, leucine, protein hydrolysate and Ca2+ by ligated loops of small intestine was significantly affected in presence of lectins from peas and lentils. Except for sucrose, all other nutrients showed significant decrease in their absorption in presence of lectins. Lentil lectins had a greater inhibitory effect than pea lectins. 相似文献
89.
90.
Nocardia polychromogenes (saprophytic) and Nocardia asteroides (pathogenic) showed characteristic patterns in changes of cellular lipids during growth. Total lipids and total phospholipids decreased with the age of the culture in the saprophytic strain, whereas in the pathogenic strain total lipids increased throughout the culture period and the total phospholipids decreased in the late stationary phase. The decrease in total phospholipids in saprophytic strain was reflected in the individual phosphatides. In the pathogenic strain, the phosphatidylinositomannoside content doubled in early stationary phase. Differences were observed in fatty acid composition of phosphatides at various stages of growth, but the ratio of saturated to unsaturated fatty acids remained unaltered. 相似文献