全文获取类型
收费全文 | 658篇 |
免费 | 48篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 20篇 |
2013年 | 40篇 |
2012年 | 36篇 |
2011年 | 34篇 |
2010年 | 33篇 |
2009年 | 27篇 |
2008年 | 29篇 |
2007年 | 43篇 |
2006年 | 37篇 |
2005年 | 28篇 |
2004年 | 29篇 |
2003年 | 19篇 |
2002年 | 34篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 23篇 |
1998年 | 12篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1987年 | 6篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1968年 | 2篇 |
1967年 | 6篇 |
排序方式: 共有706条查询结果,搜索用时 15 毫秒
651.
Provitamin D2 (ergosterol), vitamins D2 and D3 reduced the calcium-mediated peroxidase secretion in three types of sugarbeet cells in suspension cultures. Vitamin D2 was the most effective in habituated non-organogenic cells which were the less sensitive to calcium; provitamin D2 was the most effective in habituated organogenic cells, while normal non-organogenic cells were equally sensitive to the three types of vitamin D. The calcium ionophore A23187 slightly restricted peroxidase release in all cases, except in the habituated organogenic cells in the presence of calcium where it exerted a promotive effect. The inhibiting effect of vitamin D2 was not counteracted by the ionophore except in this habituated organogenic cell line. 相似文献
652.
653.
654.
655.
Callus formation by fragments of cauliflower hypocotyls was favoured by raising culture medium osmolarity above ?0.38 MPa. Increase in sucrose concentration while diminishing macronutrients inhibited callus initiation and growth. Root formation by the same material required a low medium osmolarity (?0.19 MPa). Reducing sucrose concentration in the classical Murashige and Skoog rooting culture medium favoured root formation. Adventitious bud formation was also depending upon medium osmolarity besides the need for a cytokinin. Reducing too much the osmotic potential of the medium had an unfavourable effect on bud neoformation. The importance of sucrose in all these processes is pointed out. 相似文献
656.
Integrative Food-Grade Expression System Based on the Lactose Regulon of Lactobacillus casei 总被引:3,自引:0,他引:3
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
María Jos Gosalbes Carlos David Esteban Jos Luis Galn Gaspar Prez-Martínez 《Applied microbiology》2000,66(11):4822-4828
The lactose operon from Lactobacillus casei is regulated by very tight glucose repression and substrate induction mechanisms, which made it a tempting candidate system for the expression of foreign genes or metabolic engineering. An integrative vector was constructed, allowing stable gene insertion in the chromosomal lactose operon of L. casei. This vector was based on the nonreplicative plasmid pRV300 and contained two DNA fragments corresponding to the 3′ end of lacG and the complete lacF gene. Four unique restriction sites were created, as well as a ribosome binding site that would allow the cloning and expression of new genes between these two fragments. Then, integration of the cloned genes into the lactose operon of L. casei could be achieved via homologous recombination in a process that involved two selection steps, which yielded highly stable food-grade mutants. This procedure has been successfully used for the expression of the E. coli gusA gene and the L. lactis ilvBN genes in L. casei. Following the same expression pattern as that for the lactose genes, β-glucuronidase activity and diacetyl production were repressed by glucose and induced by lactose. This integrative vector represents a useful tool for strain improvement in L. casei that could be applied to engineering fermentation processes or used for expression of genes for clinical and veterinary uses. 相似文献
657.
Sugarbeet cells from normal and habituated callus released peroxidases in liquid cultures, in proportion to their endogenous level. Calcium promoted this release more in the normal than in the habituated line. Treatment of the cells with sodium azide, sodium hydrogenarsenate or phenothiazine inhibited the calcium effect, which indicated a dependence on metabolic energy and on calmodulin regulation. The Ca ionophore Ro (bromolasalocid ethanolate) restricted peroxidase release.Research partly supported by the Belgian FRFC grant 2.9009 to T.G. and by the Swiss FNSR grant 3.624-0.80 to C.P. and H.G. 相似文献
658.
Among different populations of monogerm sugarbeet fruits, those characterized by the lowest percentages of germination exhibited
the lowest percentages of mechanical deoperculation (removal of the fruit cap under the sole imbitition pressure). X-ray radiography
of dry fruits allowed a classification based on the space occupied by seeds inside the fruit cavity and further established
a correlation between the fruit type (filled, semi-filled, empty), passive deoperculation and germination. The degree of correlation
depended on the amount of bedding water which further conditioned the fruit surrounding water film.
Part IV. 相似文献
Part IV. 相似文献
659.
C Heynen G Luisetto M Cecchettin J A Kanis A Brassine S Gaspar P Franchimont 《Comptes rendus des séances de la Société de biologie et de ses filiales》1977,171(3):690-695
In spite of an important metabolic role of the liver in the synthesis and degradation of hormonal peptides and seco-stero?ds, the clinical occurrence of disturbed regulation of calcium and phosphorus metabolism is rare in hepatic disorders. 23 patients suffering from alcoholic cirrhosis were studied. All had normal plasma calcium and phosphorus concentration as well as immunoreactive parathyroid hormone levels. 25 hydroxyvitamin D3 levels were decreased. Immunoreactive calcitonin were increased in relation to the increase in plasma alkaline phosphatase activity. The causes and consequences of these endocrine disturbances are discussed. 相似文献
660.
G Heynen S Gaspar P Gysen G Plomteux P Franchimont 《Comptes rendus des séances de la Société de biologie et de ses filiales》1981,175(4):533-537
We have studied the immunoreactivity of human sera and synovial fluids in a radioimmunoassay which utilizes an anti-bovine procollagen type III antiserum and the bovine type III procollagen peptide as standard and tracer. We have noticed a complete cross reaction between bovine col 1-3 and human synovial fluid, which thus contains substance (s) having the same antigenic determinant (s) as col 1-3. On the contrary, we have demonstrated non parallelism between col 1-3 and human serum, whether the serum was obtained from normal subjects or patients suffering from various diseases. These results suggest that immunoreactive substances related to col 1-3 and detected in sera are at least partially different from those detected in synovial fluids. 相似文献