全文获取类型
收费全文 | 645116篇 |
免费 | 67289篇 |
国内免费 | 320篇 |
出版年
2018年 | 6601篇 |
2017年 | 6260篇 |
2016年 | 8684篇 |
2015年 | 10824篇 |
2014年 | 12940篇 |
2013年 | 18365篇 |
2012年 | 21251篇 |
2011年 | 21978篇 |
2010年 | 14977篇 |
2009年 | 13401篇 |
2008年 | 19371篇 |
2007年 | 20129篇 |
2006年 | 18592篇 |
2005年 | 17965篇 |
2004年 | 17854篇 |
2003年 | 17030篇 |
2002年 | 16579篇 |
2001年 | 28994篇 |
2000年 | 28871篇 |
1999年 | 22893篇 |
1998年 | 7950篇 |
1997年 | 7981篇 |
1996年 | 7710篇 |
1995年 | 7013篇 |
1994年 | 7019篇 |
1993年 | 6822篇 |
1992年 | 18263篇 |
1991年 | 17813篇 |
1990年 | 17505篇 |
1989年 | 17342篇 |
1988年 | 15767篇 |
1987年 | 15047篇 |
1986年 | 13786篇 |
1985年 | 13810篇 |
1984年 | 11441篇 |
1983年 | 9771篇 |
1982年 | 7294篇 |
1981年 | 6544篇 |
1980年 | 6194篇 |
1979年 | 10698篇 |
1978年 | 8251篇 |
1977年 | 7581篇 |
1976年 | 7186篇 |
1975年 | 7972篇 |
1974年 | 8678篇 |
1973年 | 8506篇 |
1972年 | 7647篇 |
1971年 | 7127篇 |
1970年 | 5971篇 |
1969年 | 5826篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
901.
Inhibitors of DNA synthesis (aphidicolin and araC/HU) prevent the recovery of RNA synthesis after UV-irradiation 总被引:4,自引:0,他引:4
L V Mayne 《Mutation research》1984,131(5-6):187-191
UV-irradiation causes an immediate depression in the rate of RNA synthesis in human skin fibroblasts. RNA synthesis rates recover to greater than or equal to 90% of unirradiated levels within 90 min in normal cells. This recovery can be prevented by incubating the cells after irradiation with araC/HU or aphidicolin, potent inhibitors of DNA replication and excision repair. The effect of these inhibitors on the recovery of RNA synthesis can also be observed in non-dividing cells; it is thus independent of their effects on DNA replication. 相似文献
902.
Ethanol elimination from the blood of rats with different psychophysiological features was studied using gas chromatographic head-space analysis in the general complex of tests aimed at determination of ethanol consumption. The selection of animals with different levels of the initial alcohol motivation was performed according to modified Porsolt's method. It was shown that the initial level of predisposition to depression-like states is in a dose-dependent correlation with the high rate of ethanol elimination. This is suggested to be one of the genetic indications which promotes the formation of the initial alcohol motivation and the development of experimental alcoholism. 相似文献
903.
The non-recombining nature of the Y-chromosome determines the non-independence of alleles between loci. The evolution of short tandem repeat (STR) loci in the Y-chromosome is the result of different factors such as differential mutation rates, mutation modes, gene conversion, selection and demographic processes. The degree of correlation between loci is dependent on the magnitude of these processes. The simulation of data is a routine tool used for testing hypotheses in population and evolutionary studies. The most basic parameters hitherto used in lineage haplotype simulations are the allele frequency distributions and mutation rates, assuming either full independence or linkage between loci. In this study we introduce use of the Spearman correlation coefficient to estimate the degree of dependence between non-recombining loci. Then, both the interdependence between loci and the allele frequency distributions at multi-allelic loci are incorporated in an algorithm for simulating haplotypes. We illustrate the method using published and unpublished Y-chromosome STR data. 相似文献
904.
At pH greater than 7 the absorption and magnetic circular dichroic spectra of cobalt carboxypeptidase A are insensitive to anions [Latt, S. A., & Vallee, B. L. (1971) Biochemistry 10, 4263-4270], but at pH less than 6 chloride and other anions perturb them in a manner specific for each anion. Lowering of the pH apparently facilitates the entry of an anion into the metal coordination sphere, suggesting that an acidic group normally stabilizes a metal-coordinated water molecule against displacement. The lack of sensitivity to anions at pHs between 7 and 9--when the enzyme is maximally active--and its evident abolition upon protonation of an active-site group are consistent with this interpretation. Selective modification of cobalt carboxypeptidase at Glu-270 using a carbodiimide affinity reagent generates sensitivity to anions at pH 7 very similar to that of the unmodified enzyme at pH approximately 5. This suggests that the group stabilizing the metal-coordinated water is the catalytically essential carboxylate of Glu-270. These and related results provide evidence for a mechanistically important interaction of Glu-270 with a metal-bound water molecule. 相似文献
905.
DNA was efficiently and quantitatively isolated from extremely small quantities of mycelia (0.1–10 mg) of different phytopathogenic
moulds by grinding freeze-dried mycelia with glass beads and then using a commercial DNA extraction kit. The efficiency of
disruption of the mycelia and the quantitative DNA extraction was proved by microscopy and the quantification of isolated
DNA by real time PCR.
Presented at the 27th Mykotoxin-Workshop, Dortmund, Germany, June 13–15, 2005
Financial support: German Research Foundation (DFG grant Pr 708/2). J.M. thanks the Cusanuswerk for a doctoral scholarship 相似文献
906.
907.
908.
909.
Observations on the staining of bacillus megaterium with triphenyltetrazolium 总被引:3,自引:0,他引:3 下载免费PDF全文
WEIBULL C 《Journal of bacteriology》1953,66(2):137-139
910.