全文获取类型
收费全文 | 187篇 |
免费 | 20篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 6篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 2篇 |
2009年 | 10篇 |
2008年 | 7篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 5篇 |
1965年 | 2篇 |
1942年 | 2篇 |
1941年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有207条查询结果,搜索用时 15 毫秒
1.
UDP-glucose 4-epimerase from Saccharomyces fragilis. Presence of an essential arginine residue at the substrate-binding site of the enzyme 总被引:1,自引:0,他引:1
UDP-glucose 4-epimerase from Saccharomyces fragilis was inactivated by the arginine-specific reagents phenylglyoxal, 1,2-cyclohexanedione, and 2,3-butanedione following pseudo first order reaction kinetics. The reaction order with respect to phenylglyoxal was 1.8 and that with respect to the other two diones was close to unity. Protection afforded by substrate and competitive inhibitors against inactivation by phenylglyoxal and the reduced interaction of 1-anilinonaphthalene 8-sulfonic acid, a fluorescent probe for the substrate-binding region after phenylglyoxal modification, suggested the presence of an essential arginine residue at the substrate-binding region. Experiments with [7-14C]phenylglyoxal in the presence of UMP, a ligand known to interact at the substrate-binding region, showed that only the arginine residue at the active site could be modified by phenylglyoxal. The characteristic coenzyme fluorescence of the yeast enzyme was found to be enhanced three times in phenylglyoxal-inactivated enzyme suggesting the incorporation of the phenyl ring near the pyridine moiety of NAD. 相似文献
2.
Dr. A. Shome Dr. P. N. Bhaduri 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1982,61(2):135-139
Summary The response of rice (Oryza sativa L.) embryos to X-rays (M1 to M3) was studied. By means of irradiating excised embryos, both chlorophyll and macromutation were successfully induced in three genotypes of rice. However, differential responses in terms of mutation frequency, mutation spectrum and optimal levels of X-rays required for induction of mutation (chlorophyll as well as morphological) were found to exist between cultivars. In Satika and Ashkhata, LD50 values and maximum induced seed sterility are concomitant to optimum level of radiation required for triggering chlorophyll mutation. However, optimum dose for induction of macromutation in Satika and Kerangserang is independent of either LD50 and/or induced seed sterility.Chances of obtaining both dominant and locus specific recessive mutations in the immediate X-ray treated generation (M1) are large. This indicates the very high degree of effectiveness of the excised embryo irradiation technique with rice. 相似文献
3.
Simultaneous reconstitution of Escherichia coli membrane vesicles with D-lactate and D-amino acid dehydrogenases 总被引:2,自引:0,他引:2
K Haldar P J Olsiewski C Walsh G J Kaczorowski A Bhaduri H R Kaback 《Biochemistry》1982,21(19):4590-4596
Purified preparations of D-amino acid dehydrogenase [Olsiewski, P.J., Kaczorowski, G. J., & Walsh, C. T. (1980) J. Biol. Chem. 225, 4487] and D-lactate dehydrogenase [Kohn, L.D., & Kaback, H.R. (1973) J. Biol. Chem. 248, 7012] bind independently to right-side-out and inverted Escherichia coli vesicles and to phosphatidylcholine liposomes without detectable competition. The reconstituted vesicles catalyze D-lactate- and D-alanine-dependent respiration (O2 uptake), proton translocation, and proton/lactose symport. The enzymes do not share common sites of association on either face of the E. coli membrane, and binding of both enzymes to the bilayer appears to be due to nonspecific affinity for the surface rather than specific binding to proteinaceous receptors. Each enzyme, however, appears to reduce a common proton translocating step in the membrane-bound respiratory chain, and substrate-derived electrons are transferred through a common rate-determining redox component that precedes the site of proton translocation. The results suggest that although binding is nonspecific, there is a common site for proton translocation in the membrane between the flavin-linked dehydrogenases and the cytochromes and that this site is accessible by distinct routes of electron transfer from primary dehydrogenases on either surface of the membrane. 相似文献
4.
A high affinity Ca2(+)-ATPase on the surface membrane of Leishmania donovani promastigote 总被引:2,自引:0,他引:2
A Ca2(+)-dependent ATP-hydrolytic activity was detected in the crude membrane ghost of the promastigote or vector form of the protozoal parasite Leishmania donovani, the pathogen responsible for kala azar. The Ca2(+)-ATPase was purified to apparent homogeneity after solubilization with deoxycholate. The enzyme consists of two subunits of Mr = 51,000 and 57,000 and has an apparent molecular weight of 215,000 +/- 12,000. The enzyme activity is exclusively dependent on Ca2+, and the pure enzyme can hydrolyze 1.6 mumol of ATP/min/mg of protein. The apparent Km for Ca2+ is 35 nM, which is further reduced to 12 nM in the presence of heterologous calmodulin. The enzyme is sensitive to vanadate, but is insensitive to oligomycin and ouabain. The enzyme is strongly associated with the plasma membrane and has its catalytic site oriented toward the cytoplasmic face. The enzyme spans across the plasma membrane as surface labeling with radioiodine shows considerable radioactivity in the completely purified enzyme. The localization and orientation of this high affinity, calmodulin-sensitive Ca2(+)-ATPase suggest some role of this enzyme in Ca2+ movement in the life cycle of this protozoal parasite. 相似文献
5.
The efficiency of strict reverse isolation and antimicrobial decontamination in remission induction therapy of acute leukemia was studied retrospectively in 47 patients who were treated with a standardized aggressive chemotherapy of daunorubicin and cytosine arabinoside. Twenty-two patients were treated in strict reverse isolation with antimicrobial decontamination and 25 patients in the open ward without any measures against infections. In the patients in isolation the incidence of new infections per patient was 0.77 compared to 1.42 in the control group. The rate of complete remissions was 77% in the patients in isolation vs. 56% in the control patients. 相似文献
6.
Chander P. Puri S.A. Rahman A.K. Jain R. Bhaduri C.M. Singh V. Hingorani Kesho R. Laumas 《Prostaglandins & other lipid mediators》1976,11(5):905-923
The serum levels of estradiol-17β, progesterone and HPL have been estimated by specific radioimmunoassay in thirty women undergoing abortion with 15-methyl-PGF2α given by intra-amniotic, extra-amniotic or intra-muscular route. A significant decline in the levels of these hormones was observed in 27 cases in which the pregnancy was terminated. However, in the remaining three cases, 15-methyl-PGF2α was found to be unsuccesful, and no significant change in the hormone levels was evident. The decline in these hormones was more marked by intra-muscular route, than that observed by the other routes. The pattern of estradiol-17β decline was more consistent when compared with progesterone and HPL. The levels of progesterone and HPL, in a few cases, rather showed an increase in the initial hours of 15-methyl-PGF2α administration before the decline began and this pattern was more prominent on extra-amniotic administration. In general, the decline in the hormone levels was slower in cases which took longer time for abortion than cases with shorter induction-abortion time (IAT).The decline in estradiol-17β levels was about 65 percent at six hour of intra-muscular administration of 15-methyl-PGF2α, whereas the corresponding fall with intra-amniotic and extra-amniotic routes was 29 and 22 percent, respectively. However, the net drop in its levels during IAT was not significantly different (range 70 to 80 percent) by the three routes. About 38 percent fall in progesterone levels was observed at six hour of intra-muscular administration whereas, by intra-amniotic the fall was 19 percent. The net decline in progesterone levels, during IAT, was in the range of 46 to 60 percent by the three routes. Similarly, intra-muscular 15-methyl-PGF2α evoked a sharper decline in HPL levels as compared with other routes. The total decline during IAT was 58 to 66 percent. The results, thus indicated that the abortion with 15-methyl-PGF2α was associated with a fall in the serum hormone levels, which could be resultant effect of alterations in the hormone production by the foeto-placental unit. This along with the uterine contractions may play a significant role in the abortifacient action of 15-methyl-PGF2α. 相似文献
7.
A new enzyme, galactose-6-phosphate dehydrogenase has been purified about 50-fold from goat liver. The enzyme can be distinguished from the nonspecific hexose-6-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase by its high substrate specificity and absolute pyridine nucleotide requirement. In contrast to the hexose-6-phosphate dehydrogenase, this enzyme is located exclusively in the cytoplasmic fraction of the cell. The enzyme is a metalloprotein and is highly sensitive to mercurials. The product of the reaction is possibly a ketoaldose, phosphorylated at the primary alcoholic group. 相似文献
8.
Chakkiyath Madayi Roshith Ranjan Kumar Manna Vettath Raghavan Suresh Srikanta Samanta Raju Baitha Satish K. Koushlesh Sibina Mol Salim Lohith Kumar Shravan Kumar Sharma Ashis Roychowdhury Muttanahalli Eregowda Vijayakumar Rakesh Pal Basanta Kumar Das 《Zeitschrift fur angewandte Ichthyologie》2021,37(5):795-798
The present study estimated length–weight relationships (LWRs) for six indigenous fish species (Barilius gatensis, Salmostoma acinaces, S. boopis, Puntius amphibius, Hemibagrus punctatus and Ambassis miops) based on specimens collected from River Cauvery (including estuary) during July 2017–January 2020. The sampling surveys were carried out in three distinct sampling seasons, viz., the pre-monsoon (March–May), the monsoon (July–October) and the post-monsoon (November–February). Majority of the fish specimens dealt in the study were collected from multi-meshed monofilament gill nets (mesh sizes 18, 30, 45, 60, 90, 110, 120 and 150 mm) operated by local fishers. For those sites situated in the protected areas, sampling was carried out by cast nets with prior permission from the local administration and the collected fishes were released back into river after length–weight measurements. The length measurements were noted as total length (TL) measured to the nearest 0.1 cm by using a digital Vernier caliper. A digital balance was used for weight measurements with an accuracy of 0.01 g. The study recorded a new maximum length of 48 cm for H. punctatus. The LWR data generated from the present study are significant for proper assessment of the stock status and their management, if collected together with other essential biological and physical parameters. 相似文献
9.
María G. Perotti María D. Basanta Mónica M. Steciow J. V. Sandoval‐Sierra Javier Diéguez‐Uribeondo 《Austral ecology》2013,38(6):672-679
Here, we studied the ecological significance of Saprolegnia infections (‘saprolegniasis’) on the survival and development of two populations of the endemic Patagonian anuran Pleurodema thaul (Anura, Leiuperidae). We found that four different Saprolegnia species infected eggs and embryos of P. thaul, indicating that the infection by these ‘zoosporic fungi’ was different in each anuran population and among different cohorts. Late anuran cohorts generally showed a higher incidence of infection than early cohorts, but we observed no clear overall pattern between populations. In addition, in laboratory experiments, we determined that some of the Saprolegnia species induce early hatching, and that hatching timing was variable between populations. In summary, we found that early breeding (by underlying priority effects) could improve the survival of the earliest cohorts of P. thaul by allowing them to survive the stress imposed by epidemic events of Saprolegnia. 相似文献
10.
Dominic Frigon Basanta Kumar Biswal Alberto Mazza Luke Masson Ronald Gehr 《Applied and environmental microbiology》2013,79(3):835-844
Effluents discharged from wastewater treatment plants are possible sources of pathogenic bacteria, including Escherichia coli, in the freshwater environment, and determining the possible selection of pathogens is important. This study evaluated the impact of activated sludge and physicochemical wastewater treatment processes on the prevalence of potentially virulent E. coli. A total of 719 E. coli isolates collected from four municipal plants in Québec before and after treatment were characterized by using a customized DNA microarray to determine the impact of treatment processes on the frequency of specific pathotypes and virulence genes. The percentages of potentially pathogenic E. coli isolates in the plant influents varied between 26 and 51%, and in the effluents, the percentages were 14 to 31%, for a reduction observed at all plants ranging between 14 and 45%. Pathotypes associated with extraintestinal pathogenic E. coli (ExPEC) were the most abundant at three of the four plants and represented 24% of all isolates, while intestinal pathogenic E. coli pathotypes (IPEC) represented 10% of the isolates. At the plant where ExPEC isolates were not the most abundant, a large number of isolates were classified as both ExPEC and IPEC; overall, 6% of the isolates were classified in both groups, with the majority being from the same plant. The reduction of the proportion of pathogenic E. coli could not be explained by the preferential loss of one virulence gene or one type of virulence factor; however, the quinolone resistance gene (qnrS) appears to enhance the loss of virulence genes, suggesting a mechanism involving the loss of pathogenicity islands. 相似文献