全文获取类型
收费全文 | 137篇 |
免费 | 7篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 18篇 |
2011年 | 9篇 |
2010年 | 2篇 |
2009年 | 2篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 7篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有144条查询结果,搜索用时 15 毫秒
51.
The rhizome dynamics of Typha angustifolia in relation to water depth were investigated. Observations were made in two different stands, namely Akigase from April 2002
to December 2003, and Teganuma from April 2003 to December 2004. The mean rhizome length in the two stands was not significantly
different but the mean rhizome diameter and biomass showed a significant difference. The larger rhizome diameter in Teganuma
is seemingly an important adaptation to maintain effective aeration of the rhizome by reducing the internal resistance; while
larger biomass helps survival under anoxia for longer periods of time, it also provides strong anchorage to the substrate. 相似文献
52.
Summary A total of 8 yeast and microbial cultures have been grown in the extract derived from the tubers of Jerusalem artichoke (Helianthus tuberosus) and screened according to the following optimization criteria: rates and yields of ethanol production, rates and yields of biomass production, and % of original sugars utilized during fermentation. Batch growth kinetic parameters were also determined for the cultures studied. 相似文献
53.
After preliminary screening, Mortierella alpina and Mortierella elongata were compared with respect to arachidonic acid content. M. alpina ATCC 16266 produced 2.1 g of arachidonic acid per liter in media containing 10% glucose while the highest percentage of arachidonic acid in lipid (43.3%) was observed at a glucose concentration of 2%. Arachidonic acid content in lipids increased to 66% during storage. 相似文献
54.
In the present study the most efficient R-factor controlling the ars operon was selected after screening of 39 Escherichia coli isolates by minimum inhibitory concentration test (MIC) studies from water samples of different geographical locations of India. Among all, strain isolated from Hooghly River (West Bengal) was found to have maximum tolerance towards arsenic and was further used for the development of bioreporter bacteria. Cloning of the ars regulatory element along with operator-promotor and luxCDABE from Photobacteria into expression vector has been accomplished by following recombinant DNA protocols. The bioreporter sensor system developed in this study can measure the estimated range of 0.74–60 μg of As/L and is both specific and selective for sensing bioavailable As. The constructed bacterial biosensor was further used for the determination of arsenic ion concentration in different environmental samples of India. 相似文献
55.
Rita Sikdar Uma Ganguly Pratima Pal Barsanjit Mazumder Parimal C. Sen 《Molecular and cellular biochemistry》1991,103(2):121-130
The goat spermatozoa membranes isolated after treatment with octa (ethylene glycol) mono n-dodecyl ether (C12E8) followed by discontinuous sucrose density gradient centrifugation have been found to contain an ATPase that is stimulated by externally added Ca2+ only. The membrane fraction has also found to contain Mg2+-dependent Ca2+-ATPase activity, however the former activity is about 2 fold higher than the latter. The molecular weight of the enzyme is found to be about 97,000 on SDS-polyacrylamide gel. The optimum concentration of Ca2+ required for maximum activity is 3 mM for both Mg2+-dependent and Mg2+-independent Ca2+-ATPase. Histidine and imidazole buffers are found to be the most suitable for dependent and independent enzyme activities respectively. ATP with an optimum concentration of 4 mM is observed to be the best substrate than any other nucleotides. The inhibitors like trifluoperazine and vanadate and group specific probes e.g. DTNB and TNBS inhibit these two enzymes but at different rates. Ca2+-uptake study shows that the uptake in the presence of Ca2+ and ATP is higher than in the presence of Mg2+, Ca2+ and ATP. The findings lead us to believe that the Mg2+-independent Ca2+-ATPase has some role in Ca2+ transport like Mg2+-dependent enzyme.Abbreviations Tris
Tris (hydroxymethyl) amino ethane
- Hepes-N
2-hydroxy ethyl piperizine-N1-2-ethane sulfonic acid
- Pipes-Piperizine-N
N1-bis(2-ethane sulfonic acid)
- EGTA
Ethylene Glycol-bis (-amino ethyl ether)
- N, N, N1, N1
Tetraacetic Acid, sodium salt
- TFP
Trifluoperazine
- DTNB
5,51 Dithiobis (2 nitrobenzoic acid)
- TNBS
2, 4, 6-Trinitrobenzene Sulfonate
- C12E8
Octa (ethylene glycol) mono n-dodecyl ether
- PMSF
Phenylmethyl Sulfonyl Fluoride
- PAGE
Polyacrylamide Gel Electrophoresis
- PME
-Mercapto Ethanol 相似文献
56.
The kinetics of ethanol inhibition on cell growth and ethanol production by Kluyveromyces marxianus UCD (FST) 55-82 were studied during batch growth. The liquid medium contained 10% (wt/vol) inulin-type sugars derived from an extract of Jerusalem artichoke (Helianthus tuberosus) tubers, supplemented with small amounts of Tween 80, oleic acid, and corn steep liquor. Initial ethanol concentrations ranging from 0 to 80 g/liter in the liquid medium were used to study the inhibitory effect of ethanol on the following parameters: maximum specific growth rate (μmax), cell and ethanol yields, and sugar utilization. It was found that as the initial ethanol concentration increased from 0 to 80 g/liter, and maximum specific growth rate of K. marxianus cells decreased from 0.42 to 0.09 h−1, whereas the ethanol and cell yields and sugar utilization remained almost constant. A simple kinetic model was used to correlate the μmax results and the rates of cell and ethanol production, and the appropriate constants were evaluated. 相似文献
57.
Summary Kinetics of ethanol fermentation at varying sugar concentrations of Jerusalem artichoke tuber extract has been studied using Kluyveromyces marxianus cells immobilized in calcium alginate gel beads. A maximum ethanol concentration of 111 g/l was achieved at an initial sugar concentration of 260 g/l in 20 hours, when the immobilized cell concentration in the calcium alginate beads was 53.3 g dry wt./l bead volume. Ethanol yield remained almost unaffected by initial sugar concentration up to 250 g/l and was found to be about 88% of the theoretical. Maximum rate of ethanol production decreased from 22.5 g ethanol/l/h to 10.5 g ethanol/l/h while the maximum rate of total sugars utilization decreased from 74.9 g sugars/l/h to 28.5 g sugars/l/h as the initial substrate concentration was increased from 100 to 300 g/l. The concentration of free cells in the fermentation broth was low. 相似文献
58.
Summary Two mutants of Saccharomyces cerevisiae lacking pyruvate kinase (EC.2.7.1.40) are described. The mutations are recessive, segregate 2+:2- in tetrads and do not complement each other. Single-step spontaneous revertants, isolated on glucose plates, get back pyruvate kinase activity. The enzymes from various revertants display a wide spectrum of specific activity, thermolability and altered affinity for ligands such as P-enol pyruvate, ADP and fructose 1,6-diphosphate. The mutants produce materials crossreacting to the rabbit antibody raised against purified pyruvate kinase from the wild type yeast. These mutations thus define the structural gene of pyruvate kinase.The mutations map on the leaft arm of chromosome I and form a single complementation group with five other pyruvate kinase mutations in the pyk1 gene that was earlier suggested to be a regulatory locus controlling the synthesis of this enzyme. A comparative study of these mutants has been made with the structural mutants described here. 相似文献
59.
Eukaryotic cells duplicate their genome once and only once per cell cycle. Our earlier studies with the protozoan parasite, Entamoeba histolytica, have shown that genome reduplication may occur several times without nuclear or cellular division. The Mcm2-7 protein complex is required for licensing of DNA replication. In an effort to understand whether genome reduplication occurs due to absence or failure of the DNA replication licensing system, we analysed the function of Mcm2-3-5 proteins in E. histolytica. In this study, we have cloned E. histolytica (Eh) MCM2 and Eh MCM5 genes, while Eh MCM3 was cloned earlier. The sequence of Eh MCM2-3-5 genes is well conserved with other eukaryotic homologues. We have shown that Eh Mcm2,3 proteins are functional in Saccharomyces cerevisiae. Our studies in E. histolytica showed that Eh Mcm2-3-5 proteins are associated with chromatin constitutively in cycling cells and during arrest of DNA synthesis induced by serum starvation. Alternation of genome duplication with mitosis is regulated by association-dissociation of Mcm2-7 proteins with chromatin in other eukaryotes. Our results suggest that constitutive association of Mcm proteins with chromatin could be one of the reasons why genome reduplication occurs in E. histolytica. 相似文献
60.