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101.
Factor 420-dependent tyridine nucleotide-linked hydrogenase system of Methanobacterium ruminantium. 总被引:18,自引:7,他引:11
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Methanobacterium ruminantium was shown to possess a nicotinamide adenine dinucleotide phosphate (NADP)-linked factor 420 (F420)-dependent hydrogenase system. This system was also shown to be present in Methanobacterium strain MOH. The hydrogenase system of M. ruminantium also links directly to F420, flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN), methyl viologen, and Fe-3 plus. It has a pH optimum of about 8 and an apparent Km for F420 of about 5 x 10-6 M at pH 8 when NADP is the electron acceptor. The F420-NADP oxidoreductase activity is inactive toward nicotinamide adenine dinucleotide (nad) and no NADPH:NAD or FADH2(FMNH2):NAD transhydrogenase system was detected. Neither crude ferredoxin nor boiled crude extract of Clostridium pasteuranum could replace F420 in the NADP-linked hydrogenase reaction of M. ruminantium. Also, neitther F420 nor a curde "ferredoxin" fraction from M. ruminantium extracts could substitute for ferredoxin in the pyruvate-ferredoxin oxidoreductase reaction of C. pasteurianum. 相似文献
102.
Chu H. Tzeng Kathleen D. Thrasher John P. Montgomery Bruce K. Hamilton Daniel I. C. Wang 《Biotechnology and bioengineering》1975,17(1):143-152
A high productivity tank fermentation for gramicidin S synthetases has been developed to supply biocatalyst for a preparative-scale ATP-driven cell-free enzymatic synthesis employing the polypeptide antibiotic, gramicidin S, as a model product. A rich, complex medium supports rapid and dense growth of the enzyme-producing microorganism, Bacillus brevis ATCC 9999, accompanied by the appearance of excellentenzyme activities. Under conditions used, the two enzyme fractions of the gramicidin S synthesizing system, as well as the total enzymatic activity for synthesis of gramicidin S, all reach their maxima simultaneously at the point where growth enters the stationary phase. Successful batch enzyme fermentations have been performed at the bench (14 liter) and pilot (180 liter)scales. 相似文献
103.
The neurovirulent determinants of ts1, a paralytogenic mutant of Moloney murine leukemia virus TB, are localized in at least two functionally distinct regions of the genome. 总被引:12,自引:10,他引:2
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To better understand the molecular mechanism involved in retrovirus ts1-induced paralytic disease in mice, we constructed a panel of recombinant viruses between ts1 and the wild-type viruses Moloney murine leukemia virus (MoMuLV) and MoMuLV-TB, a strain of MoMuLV. These recombinant viruses were constructed in an attempt to identify the sequence(s) in the genome of ts1 which contains the critical mutation(s) responsible for the neurovirulence of ts1. Two functionally distinct sequences in the genome of ts1 were found to be responsible for its paralytogenic ability. One of these sequences, the 0.77-kilobase-pair XbaI-BamHI (nucleotides 5765 to 6537) fragment which encodes the 5' half of gp70 and 11 base pairs upstream of the env gene coding sequence, determines the inability of ts1 to process Pr80env. The other sequence, the 2.30-kilobase-pair BamHI-PstI (nucleotides 538 to 8264 and 1 to 567) fragment, which comprises nearly two-thirds of the env gene, the long terminal repeat, and the 5' noncoding sequence, determines the enhanced neurotropism of ts1. Replacement of any one of these two regions with the homologous region from either one of the two wild-type viruses resulted in recombinant viruses which either totally failed to induce paralysis or induced a greatly attenuated form of paresis in some of the infected mice. 相似文献
104.
Mu-Chin Tzeng Ming Jhy Hseu Jun Hai Yang Richard John Guillory 《Journal of Protein Chemistry》1986,5(3):221-228
Snake presynaptic toxins such as crotoxin, -bungarotoxin and taipoxin block neuromuscular transmission through inhibiting the release of acetylcholine by their phospholipase A2 activities. On the other hand, many other phospholipase A2s show little neurotoxicity. It is likely that the difference lies in whether high affinity binding to nerve cell membranes exists or not. To test this idea, crotoxin, -bungarotoxin and taipoxin were first radioactively labeled with Na(125I) without loss of their neurotoxicity. Using the radioactive toxins we have found that each of the three showed specific binding to synaptosomal membranes from guinea pig brain. In contrast, we could not detect specific binding of a non-neurotoxic pancreatic phospholipase A2. Crotoxin and taipoxin, but not -bungarotoxin, also bound specifically to membrane preparation from other tissues. The binding of each toxin was not greatly affected by the other two toxins. The photoaffinity labeling technique has been used to obtain further information about the components which bind crotoxin. For this purpose, (125I) crotoxin was derivatized with N-hydroxysuccinimidyl-4-azidobenzoate. Autoradiographic analysis of the membranes following photoirradiation in the presence of the modified crotoxin revealed that an 85K dalton component was preferentially covalently conjugated with the crotoxin analogue in a specific manner.On leave from Department of Biochemistry and Biophysics, University of Hawaii, School of Medicine, Honolulu, Hawaii. 相似文献
105.
106.
C H Tzeng M W Chuang S Y Wang R K Hsieh C J Liu S Fan P M Chen 《Proceedings of the National Science Council, Republic of China. Part B, Life sciences》1990,14(1):47-53
Lymphokine-activated killer (LAK) cells were generated successfully without mitogen from blood mononuclear cells obtained from 14 patients with varying malignancies and 2 normal donors. Cells from both groups showed a positive cytotoxicity by a 4-hour 51-Cr-release assay against a variety of target cells including natural killer (NK) sensitive K562 myeloid leukemia, NK-resistant Raji lymphoma cell lines, and fresh/cryopreserved leukemia cells from patients refractory to standard chemotherapy but not normal blood cells. Higher cytotoxic activity was obtained with a higher effector:target ratio at 100:1 greater than 50:1 greater than 25:1 (P less than 0.01) in each setting of different targets. Experiments involving cocultures of the LAK cells with either allogeneic (9) or autologous (3) bone marrow cells disclosed no detrimental effect on the committed hemopoietic stem cells by semisolid agar colony forming unit (CFU-GM) assay. The findings suggest that LAK cells may have a potential role for the in vitro purging of the residual leukemic cells from the marrow inoculum prepared for autologous bone marrow transplantation. 相似文献
107.
Tzu-Yi Pai Ren-Jie Chiou Chwen-Jeng Tzeng Tung-Sheng Lin Shan-Chun Yeh Pao-Jui Sung Chu-Hui Tseng Chia-Ho Tsai Yao-Sheng Tsai Wen-Jui Hsu Yuh-Ling Wei 《World journal of microbiology & biotechnology》2010,26(4):589-597
In this study, the variation of biomass, kinetic parameters, and stoichiometric parameters for ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in TNCU3 process were explored at different aerobic hydraulic retention time (AHRT). The results indicated that the growth rate constants of AOB were 0.92, 0.88, and 0.95 days?1, respectively, meanwhile, those of NOB were 2.58 1.41, and 1.40 days?1, respectively, when AHRT was 5, 6, and 7 h. The lysis rate constants for AOB and NOB were 0.13 and 0.17 days?1, respectively. When AHRT was 5, 6, and 7 h, the yield coefficients of AOB were 0.20, 0.23, and 0.28 g COD g?1 N, respectively, meanwhile those of NOB were 0.23, 0.19, and 0.22 g COD g?1 N, respectively. The average percentage of AOB was 0.44, 0.61, and 0.64%, respectively, while that of NOB was 0.46, 0.61, and 0.74%, respectively. The relation between the biomass percentage of AOB and AHRT was in a good agreement with first type hyperbolic curve. The relation between the biomass percentage of NOB and AHRT was in a good agreement with seven types of curve including simple exponential curve, power exponential curve, and first type hyperbolic curve etc. When the AHRT increased from 5 to 7 h, the removal efficiency of NH4 +–N increased from 80.2 to 94.8%, or by 14.6%. Meanwhile, the removal efficiency of total nitrogen increased from 63.6 to 70.9%, or by 7.3%. 相似文献
108.
M F Wempe W B Anderson H F Tzeng P G Board M W Anders 《Biochemical and biophysical research communications》1999,261(3):779-783
Glutathione transferase zeta (GSTZ) catalyzes the biotransformation of alpha-haloalkanoic acids. Treatment of rats or humans with dichloroacetic acid prolongs its elimination half-life, and preliminary studies in this laboratory show that fluorine-lacking, but not fluorine-containing dihaloacetic acids inactivate GSTZ. In the present study, the GSTZ-catalyzed biotransformation of unlabeled and deuterated dihaloacetic acids was investigated. With [(2)H]dichloroacetic acid and [(2)H]chlorofluoroacetic acid as substrates, the deuterium present in the [(2)H]dihaloacetic acid was retained in the [(2)H]glyoxylic acid formed. This finding indicates that the enol of the dihaloacetic acid does not serve as the substrate for the enzyme. The data afford an explanation of the failure of fluorine-containing dihaloacetic acids to inactivate GSTZ: dichloroacetic acid is converted to glyoxylic acid and inactivates GSTZ, whereas chlorofluoroacetic acid is biotransformed to glyoxylic acid, but produces negligible inactivation. Mechanisms are presented indicating that this difference may be attributed to the nucleofugicity of the leaving group. 相似文献
109.
Effects of CaCl2 on in vitro polymerization of keratin extracted from cornified cells of newborn rat were investigated by means of light-scattering and supramolecular structures. Elongation and parallel assembly of filaments occurred with addition of CaCl2 to dialyzed keratin solutions and was detected by an increase in light-scattering intensity. Nonfibrous aggregates which occurred in higher buffer concentrations and in lower pH were also recorded as intensity increased. MgCl2, ZnCl2, and GdCl3 demonstrated similar effects, but NaCl and KCl showed no effect. 相似文献
110.
Post-treatments with sodium arsenite during G2 enhance the frequency of chromosomal aberrations induced by S-dependent clastogens 总被引:1,自引:0,他引:1
Treatment with sodium arsenite during the G2 phase potentiated the chromatid breaks and chromatid exchanges induced by ultraviolet light or 4-nitroquinoline 1-oxide but not those induced by methyl methanesulfonate, ethyl methanesulfonate, mitomycin C or cisplatin in Chinese hamster ovary cells. A comparison was made between the effects of treatment during G2 with sodium arsenite, cytosine-β-
-arabinofuranoside, aphidicolin, hydroxyurea, caffeine, 3-aminobenzamide and novobiocin on the frequency of chromosomal aberrations induced by the above-mentioned S-dependent clastogens. It was found that the effects varied considerably, both quantitatively and qlalitatively. However, potentiation was more often observed in the chromosomal aberrations induced by ultraviolet light and 4-nitroquinoline 1-oxide than by other S-dependent clastogens, and the frequency of chromatid exchanges was potentiated only in cells pretreated with ultraviolet light or 4-nitroquinoline 1-oxide. Furthermore, for all of the S-dependent clastogens studied, treatment with cytosine-β-
-arabinofuranoside during the G2 phase potentiated the frequency of chromatid breaks but not the frequency of chromatid exchanges. 相似文献