全文获取类型
收费全文 | 1159篇 |
免费 | 204篇 |
出版年
2018年 | 11篇 |
2016年 | 25篇 |
2015年 | 33篇 |
2014年 | 18篇 |
2013年 | 37篇 |
2012年 | 40篇 |
2011年 | 53篇 |
2010年 | 38篇 |
2009年 | 47篇 |
2008年 | 43篇 |
2007年 | 56篇 |
2006年 | 56篇 |
2005年 | 52篇 |
2004年 | 43篇 |
2003年 | 43篇 |
2002年 | 52篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 34篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 11篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 24篇 |
1988年 | 19篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 21篇 |
1981年 | 17篇 |
1980年 | 22篇 |
1979年 | 14篇 |
1978年 | 21篇 |
1977年 | 20篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1974年 | 16篇 |
1973年 | 22篇 |
1972年 | 17篇 |
1971年 | 16篇 |
1970年 | 12篇 |
1966年 | 10篇 |
1965年 | 11篇 |
排序方式: 共有1363条查询结果,搜索用时 31 毫秒
1.
Effects of atropine on respiratory heat loss in asthma 总被引:4,自引:0,他引:4
Breslin F. J.; McFadden E. R. Jr; Ingram R. H. Jr; Deal E. C. Jr 《Journal of applied physiology》1980,48(4):619-623
2.
3.
4.
5.
Efficient ethanol production from glucose, lactose, and xylose by recombinant Escherichia coli 总被引:4,自引:0,他引:4
Lactose and all of the major sugars (glucose, xylose, arabinose, galactose, and mannose) present in cellulose and hemicellulose were converted to ethanol by recombinant Escherichia coli containing plasmid-borne genes encoding the enzymes for the ethanol pathway from Zymomonas mobilis. Environmental tolerances, plasmid stability, expression of Z. mobilis pyruvate decarboxylase, substrate range, and ethanol production (from glucose, lactose, and xylose) were compared among eight American Type Culture Collection strains. E. coli ATCC 9637(pLO1297), ATCC 11303(pLO1297), and ATCC 15224(pLO1297) were selected for further development on the basis of environmental hardiness and ethanol production. Volumetric ethanol productivities per hour in batch culture were 1.4 g/liter for glucose (12%), 1.3 g/liter for lactose (12%), and 0.64 g/liter for xylose (8%). Ethanol productivities per hour ranged from 2.1 g/g of cell dry weight with 12% glucose to 1.3 g/g of cell dry weight with 8% xylose. The ethanol yield per gram of xylose was higher for recombinant E. coli than commonly reported for Saccharomyces cerevisiae with glucose. Glucose (12%), lactose (12%), and xylose (8%) were converted to (by volume) 7.2% ethanol, 6.5% ethanol, and 5.2% ethanol, respectively. 相似文献
6.
Three casein kinase activities have been resolved by column chromatography of HeLa cell nuclear extracts. In addition to casein kinases NI and NII, which have been described in other cell types, HeLa nuclei contain a third casein kinase activity which we have named NIII. NIII is a cyclic nucleotide-independent casein kinase which uses either Mg2+ or Mn2+ as a divalent cation, but is inhibited by increasing NaCl concentrations in the presence of Mg2+ and has optimal activity at 50 mM NaCl in the presence of Mn2+. In Mg2+, NIII uses only ATP as a phosphate donor, but in Mn2+ NIII transfers phosphate from either ATP or GTP. NIII phosphorylates the serine and threonine residues of casein, but does not phosphorylate phosvitin or calf thymus histones. 相似文献
7.
8.
Expression of Different Levels of Ethanologenic Enzymes from Zymomonas mobilis in Recombinant Strains of Escherichia coli 总被引:11,自引:4,他引:7 下载免费PDF全文
The expression of Zymomonas mobilis genes encoding pyruvate decarboxylase and alcohol dehydrogenase II in Escherichia coli converted this organism from the production of organic acids to the production of ethanol. Ethanol was produced during both anaerobic and aerobic growth. The extent to which these ethanologenic enzymes were expressed correlated with the extent of ethanol production. The replacement of organic acids with ethanol as a metabolic product during aerobic and anaerobic growth resulted in dramatic increases in final cell density, indicating that these acids (and the associated decline in pH) are more damaging than the production of ethanol. Of the plasmids examined, the best plasmid for growth and ethanol production expressed pyruvate decarboxylase and alcohol dehydrogenase II at levels of 6.5 and 2.5 IU/mg of total cell protein, respectively. 相似文献
9.
Determination of the intracellular concentration of ethanol in Saccharomyces cerevisiae during fermentation. 总被引:10,自引:8,他引:2 下载免费PDF全文
Considerable controversy exists concerning the intracellular concentration of ethanol in Saccharomyces cerevisiae during fermentation. This controversy results from problems in the measurement of the intracellular concentration of compounds like ethanol, which are being produced rapidly by metabolism and potentially diffuse rapidly from the cell. We used a new method for the determination of intracellular ethanol based on the exclusion of [14C]sorbitol to estimate the aqueous cell volume. This method avoided many of the technical problems in previous reports. Our results indicate that the extracellular concentrations of ethanol in fermenting suspensions of S. cerevisiae are less than or equal to those in the intracellular environment and do not increase to the high levels previously reported even during the most active stages of batch fermentation. 相似文献
10.
Expiratory flow-volume curves with periodic interruption of flow showed flow transients exceeding maximal flow (Vmax) measured on the maximum expiratory flow-volume (MEFV) curve in a mechanical lung model and in five tracheotomized, vagotomized, open-chest, anesthetized dogs. Direct measurement of flow from the collapsing model airway showed that the volume of the flow transients in excess of the MEFV envelope was greater than that from the collapsing airway. Determination of wave-speed flows from local airway transmural pressure-area curves (J. Appl. Physiol. 52: 357-369, 1982) and photography of the airway led to the following conclusions. Flow transients exceeding Vmax are wave-speed flows determined by an initial and unstable configuration of the flow-limiting segment (FLS) with maximum compression in the midportion. The drop in flow from the peak to the following plateau is due to development of a more stable airway configuration with maximum compression at the mouthward end with a smaller area and a smaller maximal flow. When FLS jumps to a more peripheral position, the more distal airways may pass through similar configurational changes that are responsible for the sudden decrease of flow (the "knee") seen on most MEFV curves from dogs. 相似文献