全文获取类型
收费全文 | 10506篇 |
免费 | 1015篇 |
国内免费 | 19篇 |
出版年
2022年 | 78篇 |
2021年 | 198篇 |
2020年 | 88篇 |
2019年 | 112篇 |
2018年 | 153篇 |
2017年 | 111篇 |
2016年 | 229篇 |
2015年 | 495篇 |
2014年 | 516篇 |
2013年 | 659篇 |
2012年 | 829篇 |
2011年 | 786篇 |
2010年 | 473篇 |
2009年 | 371篇 |
2008年 | 593篇 |
2007年 | 592篇 |
2006年 | 542篇 |
2005年 | 462篇 |
2004年 | 461篇 |
2003年 | 409篇 |
2002年 | 393篇 |
2001年 | 197篇 |
2000年 | 143篇 |
1999年 | 114篇 |
1998年 | 127篇 |
1997年 | 89篇 |
1996年 | 92篇 |
1995年 | 65篇 |
1994年 | 94篇 |
1993年 | 74篇 |
1992年 | 102篇 |
1991年 | 81篇 |
1990年 | 100篇 |
1989年 | 96篇 |
1988年 | 71篇 |
1987年 | 71篇 |
1986年 | 61篇 |
1985年 | 83篇 |
1984年 | 75篇 |
1983年 | 73篇 |
1982年 | 90篇 |
1981年 | 58篇 |
1980年 | 53篇 |
1979年 | 65篇 |
1978年 | 52篇 |
1977年 | 58篇 |
1976年 | 66篇 |
1975年 | 69篇 |
1974年 | 64篇 |
1973年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Immobilization of lipoxygenase in an alginate-silicate solgel matrix: formation of fatty acid hydroperoxides 总被引:3,自引:0,他引:3
A method for the immobilization of lipoxygenase (LOX) in an alginate-silicate gel matrix was developed. In this method, a mixture of calcium alginate beads and LOX in borate buffer are dispersed into a hexane solution of tetramethoxy-ortho-silicate (TMOS). Hydrolysis of the TMOS gives products that permeate and co-polymerize with the alginate gel to form a colloid within the beads that entraps the LOX. Optimum reaction conditions for sol-gel entrapment of LOX are at pH 9.0 in 0.2M borate buffer. The composite gel, after isolation and vacuum drying, had excellent protein retention that has good enzyme activity and stability at room temperature. The activity of the entrapped LOX was less than the activity of the free enzyme. However, the activity of the immobilized LOX can be restored by the addition of borate buffer and glycerol, or borate buffer saturated with an organic solvent. In contrast to the free enzyme in solution, which loses its activity in less than one day, sol-gel entrapped LOX retains its activity at ambient temperature for at least 25 days and can be recycled. This report demonstrates that the sol-gel entrapment method for immobilizing LOX can be useful in developing a process for the oxidation of polyunsaturated fatty acids. 相似文献
24.
D A Keire P Anton K F Faull E Ruth J H Walsh P Chew D Quisimoro M Territo J R Reeve 《The Journal of biological chemistry》2001,276(52):48847-48853
The structure of a small-molecule, non-peptide chemotactic factor has been determined from activity purified to apparent homogeneity from Helicobacter pylori supernatants. H. pylori was grown in brucella broth media until one liter of solution had 0.9 absorbance units. The culture was centrifuged, and the bacteria re-suspended in physiological saline and incubated at 37 degrees C for 4 h. A monocyte migration bioassay revealed the presence of a single active chemotactic factor in the supernatant from this incubation. The chemotactic factor was concentrated by solid phase chromatography and purified by reverse phase high pressure liquid chromatography. The factor was shown to be indistinguishable from diethyl phthalate (DEP) on the basis of multiple criteria including nuclear magnetic resonance spectroscopy, electron impact mass spectroscopy, UV visible absorption spectrometry, GC and high pressure liquid chromatography retention times, and chemotactic activity toward monocytes. Control experiments with incubated culture media without detectable bacteria did not yield detectable DEP, suggesting it is bacterially derived. It is not known if the bacteria produce diethyl phthalate de novo or if it is a metabolic product of a precursor molecule present in culture media. DEP produced by H. pylori in addition to DEP present in man-made products may contribute to the high levels of DEP metabolites observed in human urine. DEP represents a new class of chemotactic factor. 相似文献
25.
Paola A Gilardoni Stefan Schuck Ruth Jüngling Björn Rotter Ian T Baldwin Gustavo Bonaventure 《BMC plant biology》2010,10(1):66
Background
Plants trigger and tailor defense responses after perception of the oral secretions (OS) of attacking specialist lepidopteran larvae. Fatty acid-amino acid conjugates (FACs) in the OS of the Manduca sexta larvae are necessary and sufficient to elicit the herbivory-specific responses in Nicotiana attenuata, an annual wild tobacco species. How FACs are perceived and activate signal transduction mechanisms is unknown. 相似文献26.
Reinhold Benesch Samuel Waxman Ruth Benesch Charles Baugh 《Biochemical and biophysical research communications》1982,106(4):1359-1363
Pteroyl polyglutamates bind to hemoglobin with an affinity which leaves only a minor fraction of red cell folate in the free state. This could serve as a regulating mechanism for protein synthesis in the differentiating erythroblast. 相似文献
27.
A convenient method for enzyme kinetic studies is introduced. The method includes identification of reaction mechanism and estimation of the associated kinetic constants with a minimum number of experiments. The application of the method is illustrated by using literature data. Factors limiting the application of this method are also discussed. 相似文献
28.
29.
30.