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1.
Ramakrishna A. Bangaru Yatish K. Bansal A. R. M. Rao T. P. Gandhi 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2000,739(2)
A rapid, simple and sensitive reversed-phase high-performance liquid chromatographic (HPLC) method has been developed for the measurement of acyclovir concentrations in human plasma and its use in bioavailability studies is evaluated. Unchanged acyclovir has been quantified without the introduction of an internal standard using the present method. Human plasma proteins were selectively precipitated by the addition of 7% perchloric acid to spiked plasma samples or to the plasma samples obtained after acyclovir administration to human volunteers and the mixture was spun at 1000 g for 10 min. The supernatant was directly injected into a Novaflex C18 column and detected at 254 nm. The mobile phase consisted of octane sulfonic acid buffer (pH 2.5) and methanol (92:08). The limit of quantitation for acyclovir in plasma was 20 ng/ml, which enabled the determination of the area under the curve (AUC) more precisely, that is, it is much closer to its extrapolated value. The present method has been successfully applied to samples from bioavailability studies. 相似文献
2.
R M Dixon B T Golding S Mwesigye-Kibende D N Ramakrishna Rao 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1985,311(1152):531-544
The vitamin B12 coenzyme adenosylcobalamin assists the enzymic catalysis of molecular rearrangements of the type (formula; see text) in which the migrating group X can be OH, NH2 or a suitable substituted carbon atom such as C(=CH2)CO2H. This paper discusses evidence for the participation of organic radicals as intermediates in these reactions. Theoretical and model studies supporting the intermediacy of radicals in the reactions catalysed by the enzymes diol dehydratase and alpha-methyleneglutarate mutase are described. For the model studies, alkyl radicals, alkylcobaloximes (alkyl represents, for example, ethoxycarbonyl substituted, but-3-enyl and cyclopropylmethyl) and also dihydroxyalkylcobalamins have been investigated. The Co-C alpha-C beta angle of 125 degrees in adenosylcobalamin is shown to be an 'especial' angle by analysis of the crystal structures of R- and S-2,3-dihydroxypropylcobalamin. 相似文献
3.
It is shown for the first time that the content of ubiquinone of liver increases (2.5 fold) on dietary administration of the
widely-used industrial Plasticizer diethylhexyl Phthalate to the rat. The increase is localized almost entirely in mitochondria
in which the concentration of the quinone Per mg Protein is 1.7 times the control. IncorPoration of the radioactive Precursor
(acetate) reveals that the biosynthesis of ubiquinone is increased in the livers of Plasticizer-administered animals. The
rate of degradation is not altered. 相似文献
4.
S. Y. Ahmed B. K. Lonsane N. P. Ghildyal S. V. Ramakrishna 《Biotechnology Techniques》1987,1(2):97-102
Summary A large scale solid state fermentor of 150 tray capacity is designed with appropriate control system. It gave better productivity even at higher scale of operation as compared to lab and large scale units of similar type and largely overcomes some operational problems. 相似文献
5.
B. Seshadri Sekhar C. K. Ramakrishna Kurup T. Ramasarma 《Molecular and cellular biochemistry》1990,95(1):61-70
A membrane protein recognized by monoclonal antibody SQM1 was identified in human squamous carcinomas, including those originating in the head and neck (SqCHN), lung and cervix. Cell lines derived from SqCHN of previously untreated patients expressed high amounts of this protein. In contrast, many cell lines established from SqCHN of patients previously treated with chemotherapy and/or radiation showed diminished amounts of this SQM1 protein. The expression of SQM1 antigen was determined in several SgCHN cell lines made resistant by exposure to methotrexate (MTX) in vitro. The parent cell lines all exhibited strong binding to SQM1 antibody. The MTX-resistant sublines showed much lower membrane binding of SQM1. The lowest SQM1 reactivity was found in cell lines with high resistance to MTX and with diminished rate of MTX transport. Some highly MTX-resistant cell lines which had high levels of dihydrofolate reductase, but which retained a high rate of MTX transport, also retained high levels of SQM1 binding. Reduced SQM1 protein was also found in SgCHN cells which developed resistance to the alkylating drug cis-platinum (CDDP) and which showed reduced membrane transport of CDDP. Cell growth kinetics and non-specific antigenic shifts were not responsible for the differences in SQM1 binding between the parent cell lines and their drug-resistant sublines. The finding of a novel protein which is reduced in cells resistant to MTX and CDDP could contribute to our understanding of the basic mechanisms of drug resistance. By detecting SQM1 protein in clinical specimens, it may be possible to monitor the development of drug resistance in tumors.Abbreviations SqCHN
Squamous Carcinoma of the Head and Neck
- MTX
Methotrexate
- CDDP
Cis-Platinum
- DHFR
Dihydrofolate Reductase 相似文献
6.
7.
N. Saswathi R. Sheela R. Jamuna S. V. Ramakrishna 《Bioprocess and biosystems engineering》1995,12(6):283-286
The cells of Bacillus circulans (ATCC 21783) immobilized in sodium alginate gel matrix were able to synthesize the extracellular enzyme, Cyclodextrin glycosyl transferase (CGTase, E.C. 2.4.1.19) which is industrially employed for the preparation of cyclodextrins. Optimization for the maximum production of enzyme was carried out by varying the cell density (3.3–53.5 kg/m3) in the gel and the incubation temperature (30°–42°C). The CGTase activity was found to be the highest (45 units/cm3) with maximum cell loading at 37°C. The reusability of immobilized cells was ascertained by repeated batch experiments. The enzyme activity exhibited was in the range of 50 to 55 units/cm3 in each batch. The continuous synthesis of CGTase by immobilized cells has been demonstrated by operating a fluidized bed reactor at a dilution rate 1.1 · 10–4 sec–1 for a period of 15 days. The enzyme activity has decreased to 42.5 units/cm3 from an initial value of 61 units/cm3 during continuous operation.The authors are grateful to Dr. A.D. Damodaran, Director, Regional Research Laboratory, Trivandrum for his keen interest and encouragement and to Department of Biotechnology, Government of India, New Delhi for financial support. 相似文献
8.
Direct and indirect competitive enzyme-linked immunosorbent assays were optimized for the determination of aflatoxin B1 in groundnut utilizing a specific monoclonal antibody developed at the University of Strathclyde, UK. The monoclonal antibody was conjugated to horseradish peroxidase (HRP) for direct competitive assay, while a commercially available goat-antimouse IgG-HRP conjugate was employed for indirect competitive ELISA. Both ELISAs detected aflatoxin B1 as low as 20 pg/well. Methanol-water-KCl (70 + 30 v/v, 0.5 %) extracts of groundnut were assayed by ELISA after diluting 1: 10 with PBS-Tween buffer or subjected to simple cleanup for 5:1 concentration prior to assay. The mean recoveries from groundnut spiked with 10 to 200/ig/kg of pure aflatoxin B1 were >90% in either ELISA, but the toxin recoveries at concentrations of 1–5μg/kg were only 65–67 % when subjected to cleanup and concentration before assay. The mean within-assay, inter-assay, and sub-sample coefficients of variation by ELISA of aflatoxin B1 in naturally contaminated groundnuts were, respectively, 8.9%, 11.1%, and 7.9% for direct competitive assay and 4.6%, 11.2%, and 8% for indirect competitive assay. Both ELISA methods are useful for routine analysis of aflatoxin B1 in groundnuts. 相似文献
9.
J. G. Sastry W. Ramakrishna S. Sivaramakrishnan R. P. Thakur V. S. Gupta P. K. Ranjekar 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(6-7):856-861
Genetic variability in six host genotype-specific pathotypes of pearl millet downy mildew pathogen S. graminicola was studied at the molecular level using mini- and micro-satellites. Our results indicated that microsatellites (GAA)6, (GACA)4, and especially (GATA)4 were quite informative and showed high levels of polymorphism among the pathotypes. The six pathotypes could be classified into five groups based on the cluster analysis of their genetic similarities, thereby confirming the existence of distinct host genotype-specific virulence in S. graminicola pathotypes. We demonstrate, for the first time, the use of DNA fingerprinting to detect genetic variation in downy mildew fungus of pearl millet. 相似文献
10.
Using the rotifer Brachionus calyciflorus and the cladocerans Ceriodaphnia rigaudi, Moina macrocopa and Daphnia carinata as prey (food) species, the capture success (CS), frequency of feeding and total daily food intake of rohu ( Labeo rohita ) and singhi ( Heteropneustes fossilis ) larvae were determined. The CS in both rohu and singhi was a direct function of their age as well as hunger level, but at any given age it was inversely related to prey size. The larvae fed more or less continuously, even during the night hours. Gut evacuation rates were slower in singhi than in rohu. The daily food consumption rates in rohu and singhi larvae were 13.3% and 17.7% at age 6 days, and 8.0 and 10.1% of the dry body weight at age 12 days, respectively. Although as adults rohu and singhi have distinct food niches, they did not differ significantly in the larval stages in the parameters studied. The implications of these findings for larval rearing in the aquaculture of rohu and singhi are discussed. 相似文献