全文获取类型
收费全文 | 912篇 |
免费 | 43篇 |
国内免费 | 1篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 21篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 27篇 |
2015年 | 27篇 |
2014年 | 41篇 |
2013年 | 60篇 |
2012年 | 81篇 |
2011年 | 67篇 |
2010年 | 44篇 |
2009年 | 36篇 |
2008年 | 47篇 |
2007年 | 57篇 |
2006年 | 47篇 |
2005年 | 44篇 |
2004年 | 43篇 |
2003年 | 41篇 |
2002年 | 28篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有956条查询结果,搜索用时 34 毫秒
11.
Manju Basu Shu-Ai Weng Hongyu Tang Farhat Khan Federica Rossi Subhash Basu 《Glycoconjugate journal》1996,13(3):423-432
The galactosyltransferase, GalT-4, which catalyses the biosynthesisin vitro of neolactotetraosylceramide, nLcOse4Cer (Gal1-4GleNAc1-3Gal1-4Glc-Cer) from lactotriaosylceramide, LcOse3Cer (GlcNAc1-3Gal1-4Glc-Cer), and UDP-galactose has been purified 107 500-fold from a mineral oil induced mouse T-lyphoma P-1798, using affinity columns. The purified enzyme is partially stabilized in the presence of phospholipid liposomes. Two closely migrating protein bands of apparent molecular weights 56 kDa and 63 kDa were observed after sodium dodecyl sulfate polyacrylamide gel electrophoresis of highly purified mouse GalT-4. These two protein bands, when subjected to limited proteolysis, resulted in three peptides with identical mobilities indicating amino acid sequence identity between the proteins. Both protein bands from P-1798 gave a positive immunostain when tested with polyclonal antibody against bovine lactose synthetase (UDP-Gal:Glc 4-galactosyltransferase) following Western blot analysis on nitrocellulose paper. The enzyme has a pH optimum between 6.5 and 7.0 and like all other galactosyltransferases, GalT-4 has absolute requirements for divalent cation (Mn2+). TheK
m values for the substrate LcOse3Cer and donor UDP-galactose are 110 and 250 µm, respectively. Substrate competition studies with LcOse3Cer and either asialo-agalacto-1-acid glycoprotein orN-acetylglucosamine revealed that these reactions might be catalysed by the same protein. The only other glycolipid which showed acceptor activity toward the purified GalT-4 was iLcOse5Cer (GlcNAc1-1-3Gal1-4Lc3), the precursor for polylactosamine antigens. However, competition studies with these two active substrates using the most purified enzyme fraction, revealed that these two reactions might be catalysed by two different proteins since the experimental values were closer to the theoretical values calculated for two enzymes. Interestingly however, it seems that the GalT-4 from P-1798 has an absolute requirement for anN-acetylglucosamine residue in the substrate since the lyso-derivative (GlcNH21-3Gal1-4Glc-sphingosine) of the acceptor glycolipid LcOse3Cer is completely inactive as substrate while theK
m andV
max of the reacetylated substrate (GlcNac1-3Gal1-4Glc-acetylsphingosine) was comparable with LcOse3Cer. Autoradiography of the radioactive product formed by purified P-1798 GalT-4 confirmed the presence of nLcOse4Cer, as the product cochromatographed with authentic glycolipid. The monoclonal antibody IB-2, specific for nLcOse4Cer, also produced a positive immunostained band on TLC as well as giving a positive ELISA when tested with radioactive product obtained using a highly purified enzyme from mouse P-1798 T-lymphoma.Abbreviations EDTA
ethylenediamine tetraacetate
- ME
-mercaptoethanol
- PEG
polyethylene glycol
- PBS
phosphate buffered saline
- Suc
sucrose
- Mn2+
manganese
- Gal
galactose
- GlcNAc
N-acetylglucosamine
- UDP-Gal
Uridine diphosphate galactose
- Ab
antibody
- SDS
sodium dodecyl sulphate
- PAGE
polyacrylamide gel electrophoresis
- ECB
embryonic chicken brain
- Cer
ceramide
- nLc4 or NlcOse4Cer
Gal1-4GleNac1-3Gal1-4Glc-Cer, neoLactotetraosylceramide
- Lc3 or LcOse3Cer
GlcNac1-3Gal1-4Glc-Cer, lactotriaosylceramide
- iLc5
iLcOse5Cer, GlcNAc1-3nLcOse4Cer
- nLc6
nLcOse6Cer, Gal1-4iLcOse5Cer
- SA–Gal–1AGP
asialo-agalacto1-acid glycoprotein
- TLC
thin layer chromatography 相似文献
12.
A hypercellulolytic mutant of Fusarium oxysporum 总被引:2,自引:2,他引:0
Multiple mutagenesis of Fusarium oxysporum DSM 841 resulted in enhanced yields of cellulases. The hypercellulolytic mutant (NTG-19) secretes high levels of extracellular cellulases on different cellulosic substrates. Addition of surfactant, Tween-80, further increased enzyme secretion by about 30%. The results on hydrolysis of wheat straw by parent strain, DSM 841 and mutant NTG-19 cellulases also revealed a significant improvement in the hydrolytic potential of the cellulolytic enzymes from the mutant NTG-19. 相似文献
13.
Inhibition by 2,4-D of somatic embryogenesis in carrot as explored by its reversal by difluoromethylornithine 总被引:1,自引:0,他引:1
The development of somatic embryos is, in many plants, inhibited by 2,4-dichlorophenoxyacetic acid (2,4-D) and other auxins. The finding that difluoromethylornithine (DFMO) can counteract this inhibition has been used to test some of the hypotheses for the mechanism of inhibition.
Inhibition of somatic embryogenesis in carrot ( Daucus carota L.) by exogenous ethylene (from ethephon), antioxidants (ascorbic acid and glutathione), ethanol/acetaldehyde and abscisic acid was not counteracted by DFMO, indicating that the inhibitory effect of 2,4-D is not manifest through the formation of these compounds. Embryogenesis was abolished by micromolar concentrations of the polar auxin transport inhibitors 2, 3, 5-triiodobenzoic acid (TIBA), N-1-naphthylphthalamic acid (NPA) and 9-hydroxyfluorene-9-carboxylic acid (HFCA). This inhibition was counteracted to a considerable extent by DFMO. Inhibition by relatively high concentrations of the antiauxin 2-( p -chlorophenoxy)-isobutyric acid (CPIB), which does not affect polar auxin transport, was in contrast not counteracted by DFMO. These findings indicate that exogenous auxins may inhibit embryogenesis by interfering with the ability of postglobular embryos to set up internal auxin gradients necessary for polarized growth. 相似文献
Inhibition of somatic embryogenesis in carrot ( Daucus carota L.) by exogenous ethylene (from ethephon), antioxidants (ascorbic acid and glutathione), ethanol/acetaldehyde and abscisic acid was not counteracted by DFMO, indicating that the inhibitory effect of 2,4-D is not manifest through the formation of these compounds. Embryogenesis was abolished by micromolar concentrations of the polar auxin transport inhibitors 2, 3, 5-triiodobenzoic acid (TIBA), N-1-naphthylphthalamic acid (NPA) and 9-hydroxyfluorene-9-carboxylic acid (HFCA). This inhibition was counteracted to a considerable extent by DFMO. Inhibition by relatively high concentrations of the antiauxin 2-( p -chlorophenoxy)-isobutyric acid (CPIB), which does not affect polar auxin transport, was in contrast not counteracted by DFMO. These findings indicate that exogenous auxins may inhibit embryogenesis by interfering with the ability of postglobular embryos to set up internal auxin gradients necessary for polarized growth. 相似文献
14.
Unnikrishnan Nair N. Silpa Subhash S. M. Sunoj 《Biometrical journal. Biometrische Zeitschrift》2023,65(3):2200008
In the present communication, we propose a quantile-based measure for the divergence between two survival functions. This can also be used in a dynamic way where the divergence between survival functions varies with time. Several new properties of the proposed measure are investigated with suitable examples. The behavior of the measure for various reliability models is also investigated. A real data analysis is employed to compare the relative efficacy of two treatment groups using the proposed divergence measure. 相似文献
15.
Sujoy Ghosh John W. Kyle Sara Dastgheib Francois Daussin Zhixiong Li Subhash Basu 《Glycoconjugate journal》1995,12(6):838-847
A 1-3 galactosyltransferase (GalT-3; UDP-Gal; GM2 1-3galactosyltransferase) was purified over 5100-fold from 19-day-old embryonic chicken brain homogenate employing detergent solubilization, -lactalbumin Sepharose, Q-Sepharose, UDP-hexanolamine Sepharose, and GalNAc1-4Gal-Synsorb column chromatography. The purified enzyme was resolved into two bands on reducing gels with apparent molecular weights of 62 kDa and 65 kDa, respectively. GalT-3 activity was also localized in the same regions by activity gel analysis and sucrose-density gradient centrifugation of a detergent-solubilized extract of 19-day-old embryonic chicken brain. Purified GalT-3 exhibited apparentK
mS of 33 µm, 22 µm and 14.4mM with respect to the substrates GM2, UDP-galactose, and MnCl2, respectively. Substrate specificity studies with the purified enzyme and a variety of glycosphingolipids, glycoproteins, and synthetic substrates revealed that the enzyme was highly specific only for the glycosphingolipid acceptors, GM2 and GgOse3Cer (asialo-GM2). Ovine-asialo-agalacto submaxillary mucin inhibited the transfer of galactose to GM2 but did not act as an acceptor in the range of concentrations tested. Polyclonal antibodies raised against purified GalT-3 inhibited GalT-3 activityin vitro and Western-immunoblot analysis of purified GalT-3 showed immunopositive bands at 62 and 65 kDa.Abbreviations CNS
central nervous system
- GM1
monosialotetraosylganglioside, Gal1-3GalNAc1-4(NeuAc2-3)Gal1-4Glc1-1Cer
- GM2
monosialotriaosylganglioside, GalNAc1-4(NeuAc2-3)Gal1-4Glc1-1Cer
- DSS
detergent solubilized supernatant
- ECB
embryonic chicken brain
- TBS
Tris-buffered saline 相似文献
16.
Mittal Chandra K. Harrell William B. Mehta Chander S. 《Molecular and cellular biochemistry》1995,149(1):263-265
This study was designed to evaluate thein vitro effects of transition heavy metal cations on activity of constitutive isoform of nitric oxide synthase (cNOS) in rat brain. NOS activity was determined in the cytosolic fractions of rat cerebral hemispheres by conversion of3H-L-arginine to3H-L-citrulline. Different concentrations of mercury (Hg2+), nickel (Ni2+), manganese (Mn2+), zinc (Zn2+), cadmium (Cd2+), lead (Pb2+) and calcium (Ca2+) were tested on NOS activity. While all the cations caused inhibition, there were differences in the apparent inhibition constants (Ki) among the cations. With the exception of calcium ion no other cation required preincubation with the enzyme preparation. These results indicate that while calcium ion modulate cNOS activity at regulatory site(s), inhibitory influence of toxic heavy metal cations may be exerted on the catalytic site(s) either by direct binding to it or by interfering with the electron transfer during catalysis. 相似文献
17.
Subhash C. Jamdar Linda J. Osborne Gary N. Wells 《Archives of biochemistry and biophysics》1984,233(2):370-377
The properties of Mg2+-dependent and Mg2+-independent phosphatidate phosphohydrolase activities were investigated in different subcellular fractions in rat adipose tissue. Phosphatidate phosphohydrolase activity was measured in the presence of aqueous dispersed phosphatidate as substrate, and the release of inorganic phosphate was taken as a measure of phosphatidate phosphohydrolase activity. The Mg2+-dependent phosphatidate phosphohydrolase was inhibited in the presence of N-methyl- or N-ethylmaleimide, whereas the Mg2+-independent activity was unaffected by these agents. The Mg2+-dependent phosphatidate phosphohydrolase was more sensitive to proteolysis and to high temperature (55 °C) compared to the Mg2+-independent enzyme. The Mg2+-dependent phosphatidate phosphohydrolase activity was reduced significantly during aging without any appreciable effects on the Mg2+-independent phosphatidate phosphohydrolase activity. These studies demonstrate that, in addition to Mg2+-dependency, these two forms of phosphatidate phosphohydrolases differ in several respects irrespective of their location in the adipose cell. 相似文献
18.
Thirty isolates of mungbean Rhizobium were tested for the presence of H2-recycling system. All the isolates were preliminary screened for detecting H2-recycling system in free culture using triphenyltetrazolium chloride reduction as screening procedure. The isolates which reduced the dye rapidly at early stages of growth were found to recycle hydrogen both in vivo as well as in vitro. Nitrogen fixing efficiency of hydrogenase positive, hydrogenase negative isolates and Hup– mutants was compared by green house experiments. There was 13–56% increase in dry matter and 21–46% increase in total nitrogen of the plants inoculated with H2-recycling isolates over the plants inoculated with non-recycling isolates. There was reduction in dry matter and total nitrogen content of the plants inoculated with Hup– mutants as compared to plants inoculated with wild type strain. The per cent decrease due to inoculation with Hup– mutants over wild type strain was 19–22 and 20–26 of dry weight and total nitrogen in plants, respectively.Abbreviations TTC
triphenyltetrazolium chloride 相似文献
19.
20.
Administration of picroliv, the active principle from Picrorhiza kurrooa, at a dose of 6 mg/kg, po for two weeks showed significant protection against changes in liver and brain glutathione metabolism of Plasmodium berghei infected Mastomys natalensis. The depletion of reduced glutathione level and inhibition of glutathione-S-transferase, glutathione reductase and glutathione peroxidase activities due to P. berghei infection were markedly recovered by picroliv. The increased levels of lipid peroxidation products in damaged tissues were also reduced along with the recovery of glutathione metabolism. 相似文献