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11.
Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
相似文献
12.
-Mannanase produced by Bacillus sp. W-2, isolated from decayed commercial konjak cake, was purified from the culture supernatant by (NH4)2 SO4 precipitation, adsorption to konjak gel, and column chromatography with DEAE-cellulose, Sephadex G-100 and Sephacryl S-200. Its molecular size was estimated by SDS-PAGE as 40 kDa, and by gel filtration as 36 kDa. The enzyme was most active at pH 7 and 70°C and was stable for at least 1 h between pH 5 and 10 and below 60°C. Its activity was completely inhibited by Hg2+. The enzyme hydrolysed galactomannan better than glucomannan and mainly produced mannose and mannobiose.The authors are with the Department of Bioproductive Science, Faculty of Agriculture, Utsunomiya University. Utsunomiya, Tochigi 321, Japan 相似文献
13.
14.
Correspondence of homologies in amino acid sequence and tertiary structure of protein molecules 总被引:7,自引:0,他引:7
According to the method developed previously (Kubota, Y., Takahashi, S., Nishikawa, K. and Ooi, T. (1981) J. Theor, Biol. 91, 347-361), homology among proteins may be estimated quantitatively. We extended the method to investigate the relationship of an amino acid sequence to its teritary structure and identify homologous segments which have homologous native conformations in proteins. First, we selected proper indices for the computation of correlation coefficients from 32 properties inherent to amino acids, such as hydrophobicity. The arithmetic average of correlation coefficients using six indices gave rise to a good correlation for the CD- and EF-hand regions (Ca2+ binding sites) in carp parvalbumin, but poor ones for other segments. We then applied the method to homologous proteins, the three-dimensional structures of which are known: horse hemoglobin alpha-chain and beta-chain; cytochrome c and c2; serine proteases, chymotrypsinogen and elastase; alpha-lytic protease and protease A from prokaryotic organisms. The results show that the sequence homology estimated by the present method has a good correspondence to the homology in three-dimensional structures and therefore the method is promising for the identification of important sites in sequences which have similar native conformations. For an example of the application of the method, two sequences of human interferon, one from fibroblast and the other from leukocyte, are compared, suggesting functional sites in the molecule. 相似文献
15.
E. multilocularis infection was suppressed in C.B-17 mice after intraperitoneal inoculation of protoscoleces, with larval cysts weighing no more than 1.0 g. In scid mice, which are genetically identical to C.B-17 except for a deficiency in functional lymphocytes, infection progressed and larval cysts reached a mass of 17.5 g at 15 weeks post-infection. The growth of the larval cyst mass in scid mice was similar to that in other susceptible mouse strains, with a biphasic pattern. Histological observations revealed giant cells and granulomatous inflammation in the C.B-17, but not in the scid mice. These results led to the conclusion that suppression of the growth of the larval cyst mass in the initial stage of infection in susceptible mice strains is caused by factors other than the host's lymphocytic immune response. 相似文献
16.
P. A. C. Ooi 《BioControl》1982,27(1):89-98
The two rice planthoppers that have caused devastating damage to rice crops in Peninsular Malaysia areNilaparvata lugens andSogatella furcifera. A surveillance system has been set up to monitor these pests. A case study in the off-season crop of 1980 in the Tanjung Karang Irrigation Scheme showed that hopperburn could be predicted a month before it happened. In the following main season, both surveillance records and ecological factors suggested that the pest would be under natural control and the forecast was accurate. The main factors considered in forecasting rice planthoppers were: migration, brachyptery, pest population, predatory: prey ratio, history of outbreaks and prevailing field conditions. 相似文献
17.
The thermal transition of RNase T1 was studied by two different methods; tryptophan residue fluorescence and circular dichroism. The fluorescence measurements provide information about the environment of the indole group and CD measurements on the gross conformation of the polypeptide chain. Both measurements at pH 5 gave the same transition temperature of 56 degrees C and the same thermodynamic quantities, delta Htr (= 120 kcal/mol) and delta Str (= 360 eu/mol), for the transition from the native state to the thermally denatured state, indicating simultaneous melting of the whole molecule including the hydrophobic region where the tryptophan residue is buried. Stabilization by salts was observed in the pH range from 2 to 10, since the presence of 0.5 m NaCL caused an increase of about 5 degrees C to 10 degrees C in the transition temperature, depending on the pH. The fluorescence measurements on the RNase T1 complexed with 2'-GMP showed a transition with delta Htr =167 kcal/mol and delta Str =497 eu/mol at a transition temperature about 6 degrees C higher than that for the free enzyme. The large value of delta Htr for RNase T1 indicates the highly cooperative nature of the thermal transition; this value is much higher than those of other globular proteins. Analysis of the CD spectrum of thermally denatured RNase T1 suggests that the denatured state is not completely random but retains some ordered structures. 相似文献
18.
The native conformation of a protein may be expressed in terms of the dihedral angles, phi's and psi's for the backbone, and kappa's for the side chains, for a given geometry (bond lengths and bond angles). We have developed a method to obtain the dihedral angles for a low-energy structure of a protein, starting with the X-ray structure; it is applied here to examine the degree of flexibility of bovine pancreatic trypsin inhibitor. Minimization of the total energy of the inhibitor (including nonbonded, electrostatic, torsional, hydrogen bonding, and disulfide loop energies) yields a conformation having a total energy of -221 kcal/mol and a root mean square deviation between all atoms of the computed and experimental structures of 0.63 A. The optimal conformation is not unique, however, there being at least two other conformations of low-energy (-222 and -220 kcal/mol), which resemble the experimental one (root mean square deviations of 0.66 and 0.64 A, respectively). These three conformations are located in different positions in phi, psi space, i.e., with a total deviation of 81 degrees, 100 degrees and 55 degrees from each other (with a root mean square deviation of several degrees per dihedral angle from each other). The nonbonded energies of the backbones, calculated along lines in phi, psi space connecting these three conformations, are all negative, without any intervening energy barriers (on an energy contour map in the phi, psi plane). Side chains were attached at several representative positions in this plane, and the total energy was minimized by varying the kappa's. The energies were of approximately the same magnitude as the previous ones, indicating that the conformation of low energy is flexible to some extent in a restricted region of phi, psi space. Interestingly, the difference delta phi i+1 in phi i+1 for the (i + 1)th residue from one conformation to another is approximately the same as -delta psi i for the ith residue; i.e., the plane of the peptide group between the ith and (i + 1)th residues re-orient without significant changes in the positions of the other atoms. The flexibility of the orientations of the planes of the peptide groups is probably coupled in a cooperative manner to the flexibility of the positions of the backbone and side-chain atoms. 相似文献
19.
Non-polymerizable tropomyosin was prepared by the digestion of several C-terminal residues of tropomyosin with carboxypeptidase A [EC 3.4.12.2]. The intrinsic viscosity and molecular weight of the non-polymerizable tropomyosin were almost the same as those of untreated tropomyosin. Like untreated tropomyosin, the non-polymerizable tropomyosin in combination with troponin repressed the superprecipitation of actomyosin in the absence of calcium, while this repression was released by addition of calcium. However, the curve representing the superprecipitation rate as a function of pCa was less steep than that found with actomyosin containing untreated tropomyosin: in the former case, the rate increased to a plateau over about 2 pCa units, while in the latter case, it did so over about 1 pCa unit. These experimental results provide evidence that the "co-operation" in the regulation mechanism of skeletal muscle contraction, which is indicated by the steep curve of the contraction versus pCa relation, is mediated by tropomyosin-tropomyosin interaction along the thin filament. 相似文献
20.