全文获取类型
收费全文 | 6481篇 |
免费 | 375篇 |
国内免费 | 1篇 |
出版年
2022年 | 23篇 |
2021年 | 68篇 |
2020年 | 42篇 |
2019年 | 54篇 |
2018年 | 76篇 |
2017年 | 63篇 |
2016年 | 104篇 |
2015年 | 175篇 |
2014年 | 202篇 |
2013年 | 471篇 |
2012年 | 295篇 |
2011年 | 313篇 |
2010年 | 194篇 |
2009年 | 182篇 |
2008年 | 271篇 |
2007年 | 289篇 |
2006年 | 279篇 |
2005年 | 287篇 |
2004年 | 277篇 |
2003年 | 257篇 |
2002年 | 268篇 |
2001年 | 232篇 |
2000年 | 238篇 |
1999年 | 189篇 |
1998年 | 79篇 |
1997年 | 71篇 |
1996年 | 65篇 |
1995年 | 71篇 |
1994年 | 73篇 |
1993年 | 75篇 |
1992年 | 145篇 |
1991年 | 118篇 |
1990年 | 124篇 |
1989年 | 129篇 |
1988年 | 97篇 |
1987年 | 110篇 |
1986年 | 92篇 |
1985年 | 87篇 |
1984年 | 72篇 |
1983年 | 69篇 |
1982年 | 38篇 |
1981年 | 48篇 |
1980年 | 29篇 |
1979年 | 62篇 |
1978年 | 29篇 |
1977年 | 46篇 |
1976年 | 31篇 |
1975年 | 30篇 |
1974年 | 39篇 |
1973年 | 33篇 |
排序方式: 共有6857条查询结果,搜索用时 312 毫秒
961.
962.
963.
964.
Four fractions with ribonuclease activity have been isolated from tea leaves by DEAE-cellulose column chromatography and designated as RNase Tf-1, RNase Tf-2, RNase Tf-3 and RNase Tf-4. The bigger fractions of both RNase Tf-3 and RNase Tf-4 have been partially purified by Sephadex G-100 column chromatography.RNase Tf-3 and RNase Tf-4 were respectively found to have their optimum pH at 4.75 and 4.9 and molecular weights of approximately 13,000 and 16,000, as determined by gel filtration. Both enzymes were inhibited by Cu2+ and Hg2+, and inactivated by heating at over 50°C. By addition of yeast RNA to the two enzymes, however, their thermostabilities increased. The activities of the enzymes were stable in a pH range of 4.5 to 6.5. Like other plant RNases, RNase Tf-3 and RNase Tf-4 appeared to have no preference for base in RNA. 相似文献
965.
966.
967.
968.
K Hirano M Fukuta T Adachi K Hayashi M Sugiura Y Mori K Toyoshi 《Biochemical and biophysical research communications》1985,129(1):89-94
The syntheses of copper, zinc-superoxide dismutase (Cu,Zn-SOD) and manganese-superoxide dismutase (Mn-SOD) in vitro were studied. Both Cu,Zn-SOD and Mn-SOD were preferentially synthesized by free polysomes. Mn-SOD was synthesized as a large precursor (26,000 daltons), which was processed to the mature size (22,500 daltons) by in vitro incubation with a rat liver mitochondrial fraction. On the other hand, Cu,Zn-SOD was synthesized as the mature size product. It was shown that Cu,Zn-SOD and Mn-SOD synthesized in vitro represented 0.018% and 0.016% of the total translation products of free polysomes, respectively. 相似文献
969.
970.