全文获取类型
收费全文 | 274篇 |
免费 | 39篇 |
出版年
2021年 | 5篇 |
2020年 | 4篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 15篇 |
2012年 | 11篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 15篇 |
2003年 | 19篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1996年 | 3篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有313条查询结果,搜索用时 15 毫秒
141.
Resumé Les auteurs ont étudié la composition chimique (N, substances humiques, lignine) de copeaux de bois blanc exposés à l'air libre depuis 2 à 10 ans, ainsi que leur type de peuplement fongique. En l'absence de lignivore, le pH, les taux de lignine et d'N s'élèvent et il se forme des quantités modérées d'humus à forte capacité d'échange. Dans le cas contraire, on voit apparaître, en abondance, des substances humiques peu condensées et la matière organique subit une évolution rappelant celle du mor.Avec la collaboration technique de Melle. M. Clet.Kononova, dans sa monographie5, signale de Troussov (1916) une étude que nous n'avons pas eu en mains. 相似文献
142.
Drosophila cells were treated in vitro with N-phosphonacetyl-
-aspartate (PALA) which is a specific inhibitor of aspartate transcarbamylase, the second enzyme of the pyrimidine biosynthetic pathway. By stepwise selection using increasing amounts of this inhibitor, PALA-resistant (PALAr) stable clones have been isolated. Enzymatic activities of aspartate transcarbamylase, carbamyl phosphate synthetase and dihydro-orotase, borne by the same multifunctional protein, CAD, are increased 6–12-fold in these resistant clones compared with parental cells. The aspartate transcarbamylase in PALAr cells is shown by physical, kinetic and immunological criteria to be normal. The data from immunotitration and immunoblotting experiments indicate that the increased enzyme activities result from the overproduction of CAD. 相似文献
143.
Drosophila cells were treated in vitro with N-phosphonacetyl-L-aspartate (PALA) which is a specific inhibitor of aspartate transcarbamylase, the second enzyme of the pyrimidine biosynthetic pathway. By stepwise selection using increasing amounts of this inhibitor, PALA-resistant (PALAr) stable clones have been isolated. Enzymatic activities of aspartate transcarbamylase, carbamyl phosphate synthetase and dihydro-orotase, borne by the same multifunctional protein, CAD, are increased 6-12-fold in these resistant clones compared with parental cells. The aspartate transcarbamylase in PALAr cells is shown by physical, kinetic and immunological criteria to be normal. The data from immunotitration and immunoblotting experiments indicate that the increased enzyme activities result from the overproduction of CAD. 相似文献
144.
Larval fat body-specific gene expression in D. melanogaster 总被引:2,自引:0,他引:2
J Deutsch M Laval J A Lepesant F Maschat F Pourrain L Rat 《Developmental genetics》1989,10(3):220-231
145.
146.
Repair of methylated bases in mammalian cells during adaptive response to alkylating agents 总被引:2,自引:0,他引:2
F Laval 《Biochimie》1985,67(3-4):361-364
Pretreatment of H4 (rat hepatoma) cells for 48 h with non toxic doses of alkylating agents methylmethane sulfonate, (MMS), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) renders the cells more resistant to the toxic and mutagenic effects of these compounds. This adaptive response seems to reflect improved repair of methylated lesions in cellular DNA. Therefore, we measured the activity of the DNA-glycosylase for N-methylated purines (7-MeGua and 3-MeAd) and the activity of the O6-methylguanine-DNA methyltransferase in control and adapted cells. We show that the adaptive response does not significantly increase the DNA-glycosylase activity but involves the induction of methyltransferase molecules. 相似文献
147.
Ultraviolet irradiation alters the template properties of poly(dC) when replicated by Escherichia coli DNA polymerase I. These effects are due to base modifications. Some of them are identified as apurinic/apyrimidinic sites (AP-sites) by their sensitivity to AP-endonuclease B purified from Micrococcus luteus, and their template properties. The rate of formation of AP-sites in poly(dC) is estimated at 3 X 10(-7) site per nucleotide per J.m-2. Exposure of supercoiled or relaxed pBR322 DNA to UV light results also in the formation of sites sensitive to AP-endonuclease B. In this case, the rate of formation of AP-sites is the same in relaxed or supercoiled DNA: 0.3 X 10(-7) site per nucleotide per J.m-2. The apyrimidinic sites are generated through the processing of an ultraviolet induced primary lesion. We suggest that this lesion is cytosine hydrate by its rate of decay and preferential formation in single stranded DNA. Our results suggest that AP-sites might be a minor pathway leading to UV-induced mutagenesis. 相似文献
148.
149.
150.