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101.
102.
In six rice cultivars the relative amounts of 55, 26–28 and 15 kDa polypeptides were mostly lower in plants grown for 15 d
under low irradiance than in plants grown under saturating irradiance. This decline in the polypeptides, especially in those
related to light-harvesting chlorophyll proteins, was accompanied with a decrease in the whole chain electron transport and
the photosystem 2 activity. 相似文献
103.
We describe a novel method to calculate the packing interactions in protein structural models. The method calculates the interatomic occluded surface areas for each atom in the protein model. The identification of, and degree of interaction with, neighboring atoms is accomplished by extending surface normal from a dot surface of each atom to the point of intersection with neighboring atoms. The combined occluded and non-occluded surface areas may be normalized for the amino acid composition of the protein providing a single parameter, the normalized protein surface ratio, which is diagnostic for native-like Structures. Individual residues in the model which are in infrequent occluded surface environments may be identified. The method provides a means to explicitly describe packing densities and packing environments of individual atoms in a protein model. Finally, the method allows estimation of the complementarity between any interacting molecules, for example a ligand binding to a receptor. 相似文献
104.
105.
106.
Isolation and characterization of levansucrase-encoding gene from Bacillus amyloliquefaciens 总被引:9,自引:0,他引:9
The gene encoding levansucrase (LVS) from Bacillus amyloliquefaciens (sacB[BamP]) was isolated, sequenced and expressed in Bacillus subtilis. Analysis of the nucleotide sequence of sacB[BamP] reveals extensive homology with that of the B. subtilis LVS-encoding gene in the promoter and coding region. The sacB[BamP] gene cloned in a multicopy plasmid is induced by sucrose in B. subtilis. 相似文献
107.
108.
Comparative studies of the specificities of α-chymotrypsin and subtilisin BPN′. Studies with flexible and `locked'' substrates 下载免费PDF全文
Subtilisin BPN' hydrolysed N-acetyl-l-3-(2-naphthyl)-alanine methyl ester, N-acetyl-l-leucine methyl ester and N-acetyl-l-valine methyl ester, faster than alpha-chymotrypsin. Of eight ;locked' substrates tested, only methyl 5,6-benzindan-2-carboxylate was hydrolysed faster by subtilisin, whereas the other esters were better substrates for chymotrypsin. Compared with the values for chymotrypsin, the stereospecific ratios during the hydrolysis of the optically active locked substrates by subtilisin were decreased by one and two orders of magnitude for bi- and tri-cyclic substrates respectively. The polar groups adjacent to the alpha-carbon atom of locked substrates did not contribute significantly to the reactivity of the more active optical isomers, but had a detrimental effect on the less active antipodes during hydrolysis by both the enzymes. These studies show that the binding site of subtilisin BPN' is longer and broader than that of alpha-chymotrypsin. 相似文献
109.
The possibility of proteinase inhibitory activities in lenses measured with synthetic substrates being spurious, due to the
effective competition of lens proteins as substrates for the target enzymes, was investigated. Goat, sheep and human cataractous
lens proteins were found to be poor substrates for trypsin, elastase and papain compared to casein or bovine serum albumin.
Further, the inhibition of elastase catalyzed hydrolysis of succinyl trialanyl p-nitroanilide by casein (500 μg, 53%) and
albumin (500 μg, 49%) and of trypsin-catalyzed hydrolysis of benzoyl argininep-nitroanilide by albumin (1 mg, 24%) were significant only at high protein concentrations. These data indicated that the relatively
high antielastase and antitryptic activities observed in human cataractous lenses were real. On the other hand, coincident
lens protein hydrolysis elevating the true antitryptic and antielastase activities in goat and sheep lenses (that have low
activities) could not be ruled out The lesser papain inhibitory activities observed in lenses when albumin was used as substrate
compared to activities with benzoyl arginine p-nitroanilide as substrate, appeared to be partly due to lens protein hydrolysis
masking the actual inhibition in the former method. Preincubation of goat, sheep and human lens extracts with trypsin for
1 h resulted in complete loss of antitryptic and antielastase activity except in the case of human lens antielastase activity
which underwent 50% loss. Papain inhibitory activity was fully stable. Similar papain treatment caused loss of 80–100% of
antielastase activity and 45–55% loss of antitryptic activity. 相似文献
110.
A new colorimetric method based on the phenol-sulfuric acid reaction is described for the estimation of serum glycated proteins by the differential reduction of free glucose and hexose bound nonenzymatically with 2.0 and 20 mg of NaBH4 in 0.02 ml of serum, respectively, at room temperature for 15 min. The values (microgram hexose/mg protein) in control subjects (n = 60) and diabetics (n = 90) were estimated to be 5.60 +/- 0.85 and 10.8 +/- 1.6, respectively. The increase was highly significant (P less than 0.001) in diabetics. The serum glycated protein levels correlate well with fasting blood sugar values (r = 0.77, P less than 0.001, n = 25). There was also a highly significant correlation between glycated protein level and glycated albumin value in individual serum samples (r = 0.85, P less than 0.001, n = 25). Values of borohydride reducible glyco-groups bound to serum proteins also correlated well with serum glycated protein levels (r = 0.96, p less than 0.001, n = 20) determined by the thiobarbituric acid assay method. The method is found to be simple and rapid, with a coefficient of variations of +/- 3.8%. 相似文献