全文获取类型
收费全文 | 1702871篇 |
免费 | 169343篇 |
国内免费 | 1656篇 |
出版年
2021年 | 18304篇 |
2019年 | 16283篇 |
2018年 | 18692篇 |
2017年 | 17450篇 |
2016年 | 29004篇 |
2015年 | 43440篇 |
2014年 | 51646篇 |
2013年 | 77877篇 |
2012年 | 48801篇 |
2011年 | 39567篇 |
2010年 | 47048篇 |
2009年 | 47440篇 |
2008年 | 37251篇 |
2007年 | 35871篇 |
2006年 | 39095篇 |
2005年 | 39586篇 |
2004年 | 38851篇 |
2003年 | 36347篇 |
2002年 | 34224篇 |
2001年 | 53759篇 |
2000年 | 51670篇 |
1999年 | 46007篇 |
1998年 | 28045篇 |
1997年 | 28062篇 |
1996年 | 27172篇 |
1995年 | 25295篇 |
1994年 | 25029篇 |
1993年 | 24463篇 |
1992年 | 39491篇 |
1991年 | 37904篇 |
1990年 | 36565篇 |
1989年 | 36833篇 |
1988年 | 33785篇 |
1987年 | 32760篇 |
1986年 | 30593篇 |
1985年 | 32180篇 |
1984年 | 29728篇 |
1983年 | 26140篇 |
1982年 | 24490篇 |
1981年 | 23115篇 |
1980年 | 21649篇 |
1979年 | 26553篇 |
1978年 | 23285篇 |
1977年 | 22071篇 |
1976年 | 20955篇 |
1975年 | 21278篇 |
1974年 | 22483篇 |
1973年 | 22555篇 |
1972年 | 19549篇 |
1971年 | 18132篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
Scott M. Montgomery 《CMAJ》2010,182(11):1157-1158
202.
203.
204.
Nonintegrative transformation in the filamentous fungus Podospora anserina: stabilization of a linear vector by the chromosomal ends of Tetrahymena thermophila. 总被引:3,自引:0,他引:3 下载免费PDF全文
The effect of the chromosomal ends of Tetrahymena thermophila on the stability of linear transforming molecules in the filamentous fungus Podospora anserina was tested. A derivative of an integrative vector for this fungus has been constructed, so that after linearization, the ends of the plasmid are the telomeric sequences of T. thermophila. After transformation, this linear molecule was maintained as an extrachromosomal plasmid with no integrated copies in about 50% of the transformants. Under selective conditions, there was approximately one linear molecule per 5 to 10 nuclei, and these extrachromosomal molecules were rapidly lost under nonselective conditions. The circular plasmid carrying an inverted repeat of T. thermophila telomeres could be linearized and processed in vivo. 相似文献
205.
206.
Protein metal-binding sites. 总被引:2,自引:0,他引:2
Metal ions have a role in a variety of important functions in proteins including protein folding, assembly, stability, conformational change, and catalysis. The presence or absence of a given metal ion is crucial to the conformation or activity of over one third of all proteins. Recent developments have been made in the understanding and design of metal-binding sites in proteins, an important and rapidly advancing area of protein engineering. 相似文献
207.
V K Khugaeva E D Klimenko P N Aleksandrov G F Leskova M I Reutov 《Biulleten' eksperimental'no? biologii i meditsiny》1985,100(7):15-19
Experiments were made on rabbit fed an atherogenic diet (0.5 g/kg cholesterol) singly for 15 and 24 h and repeatedly for 3, 9 and 30 days. At early stages of lipid metabolism distress the interrelationship was established between blood rheological disorders and microcirculatory abnormalities. The dependence of the initial reaction of some rheological characteristics on their initial level was marked. 相似文献
208.
Vernon Shattuck Frank R. Katterman 《Biochemical and biophysical research communications》1982,109(3):1017-1025
When cotyledonary tissue of cotton are treated with the mutagen ethyl methanesulfonate and then germinated, an enhanced, unscheduled DNA synthesis response is observed, along with a concomitant increase in the thymidine triphosphate precursor pool size. The implications of these results are discussed in this paper. 相似文献
209.
210.