全文获取类型
收费全文 | 6153篇 |
免费 | 573篇 |
国内免费 | 2篇 |
出版年
2022年 | 35篇 |
2021年 | 72篇 |
2020年 | 39篇 |
2019年 | 71篇 |
2018年 | 70篇 |
2017年 | 95篇 |
2016年 | 116篇 |
2015年 | 225篇 |
2014年 | 221篇 |
2013年 | 274篇 |
2012年 | 345篇 |
2011年 | 373篇 |
2010年 | 209篇 |
2009年 | 188篇 |
2008年 | 267篇 |
2007年 | 292篇 |
2006年 | 271篇 |
2005年 | 276篇 |
2004年 | 261篇 |
2003年 | 270篇 |
2002年 | 231篇 |
2001年 | 201篇 |
2000年 | 165篇 |
1999年 | 156篇 |
1998年 | 71篇 |
1997年 | 93篇 |
1996年 | 79篇 |
1995年 | 79篇 |
1994年 | 74篇 |
1993年 | 91篇 |
1992年 | 109篇 |
1991年 | 112篇 |
1990年 | 72篇 |
1989年 | 92篇 |
1988年 | 89篇 |
1987年 | 77篇 |
1986年 | 55篇 |
1985年 | 73篇 |
1984年 | 54篇 |
1983年 | 60篇 |
1982年 | 60篇 |
1981年 | 55篇 |
1980年 | 43篇 |
1979年 | 60篇 |
1978年 | 63篇 |
1977年 | 38篇 |
1975年 | 33篇 |
1974年 | 49篇 |
1973年 | 37篇 |
1971年 | 35篇 |
排序方式: 共有6728条查询结果,搜索用时 0 毫秒
81.
A series of novel compounds in which a 9-acridinyl nucleus is linked to a psoralen nucleus in the 5- or 8-position via polyamines was prepared and examined. Their reversible binding to DNA and their irreversible binding to DNA and DNA cross-linking upon irradiation with UV-A light were examined. It was found that they were all less efficiently photoreactive than 8-methoxypsoralen (8-MOP), both in cross-linking and photobinding to DNA, whereas the ratio between their photobinding and cross-linking was 40-400 times that of 8-MOP. Compounds in which the linker was attached to the 5-position in psoralen showed smaller cross-linking and photobinding efficiencies and larger ratios between photobinding and cross-linking than those of psoralens attached in the 8-position. This strongly indicates that the 9-substituents of the acridines are oriented toward the minor groove. Flow linear dichroism studies showed that the compounds were DNA intercalating with the acridine moiety, whereas the psoralen moiety in no case was clearly intercalating. This conclusion was further supported by viscometry which also strongly indicated monointercalation. 相似文献
82.
Hybridization of deoxyribonucleic acid (DNA) from Lactobacillus bulgaricus (ATCC 11842) with DNA of L. lactis (ATCC 12315), L. helveticus (ATCC 15009), and L. jugurt (ATCC 521) showed 86.0% reassociation with L. lactis, 4.8% with L. helveticus, and none with L. jugurt. 相似文献
83.
84.
The free-living hermaphroditic nematode, Caenorhabditis briggsae, enters a dauer stage under certain conditions in axenic culture. Dauer larvae differ from directly-developing third-stage larvae in internal structure, size at time of second molt, morphology of second and third cuticles, separation zone of cuticular caps, and survival at 4 C and 37 C, temperatures fatal to other stages. Males, which occur rarely in liquid medium, may mature under conditions which cause most of the hermaphrodites to go into the dauer stage, resulting in a culture with increased male-to-hermaphrodite ratio. 相似文献
85.
86.
87.
The submicrosomal distribution of hepatic uridine diphosphate glucuronyltransferases in the rabbit 总被引:6,自引:3,他引:3 下载免费PDF全文
1. Rabbit liver microsomes were subfractionated into rough- and smooth-surfaced types, and glucuronyltransferase activity in each microsomal subfraction was determined with p-nitrophenol, o-aminophenol and phenolphthalein as substrates. The glucuronyltransferase activity measured with p-nitrophenol and o-aminophenol as substrates was localized predominantly in rough-surfaced microsomes. Glucuronyltransferase measured with phenolphthalein as substrate was equally present in rough- and smooth-surfaced microsomes. 2. Phenobarbital pretreatment of rabbits did not stimulate any of the glucuronyltransferase activities measured in either rough- or smooth-surfaced microsomes. 3. Preincubation of rabbit liver microsomes for 30-60min. at 37 degrees under oxygen did not cause any loss of glucuronyltransferase activity. Such preincubation caused either no change or increased enzyme activity in both submicrosomal fractions. The relative distribution of transferase activity in rough- and smooth-surfaced microsomes was not affected by preincubation. 相似文献
88.
B Mondovì G Rotilio M T Costa A Finazzi-Agrò E Chiancone R E Hansen H Beinert 《The Journal of biological chemistry》1967,242(6):1160-1167
89.