全文获取类型
收费全文 | 1110篇 |
免费 | 1篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 14篇 |
金属工艺 | 1篇 |
机械仪表 | 2篇 |
能源动力 | 4篇 |
轻工业 | 3篇 |
无线电 | 1篇 |
一般工业技术 | 1篇 |
冶金工业 | 1081篇 |
自动化技术 | 2篇 |
出版年
2016年 | 1篇 |
2014年 | 1篇 |
2013年 | 9篇 |
2012年 | 1篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2004年 | 1篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 27篇 |
1998年 | 333篇 |
1997年 | 151篇 |
1996年 | 124篇 |
1995年 | 67篇 |
1994年 | 60篇 |
1993年 | 72篇 |
1992年 | 9篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 24篇 |
1988年 | 14篇 |
1987年 | 18篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1978年 | 3篇 |
1977年 | 29篇 |
1976年 | 77篇 |
1975年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有1111条查询结果,搜索用时 390 毫秒
71.
72.
73.
74.
75.
76.
An analysis of simultaneous variation in protein structures 总被引:5,自引:0,他引:5
Chelvanayagam G; Eggenschwiler A; Knecht L; Gonnet GH; Benner SA 《Protein engineering, design & selection : PEDS》1997,10(4):307-316
The simultaneous substitution of pairs of buried amino acid side chains
during divergent evolution has been examined in a set of protein families
with known crystal structures. A weak signal is found that shows that amino
acid pairs near in space in the folded structure preferentially undergo
substitution in a compensatory way. Three different physicochemical types
of covariation 'signals' were then examined separately, with consideration
given to the evolutionary distance at which different types of compensation
occur. Where the compensatory covariation tends towards retaining the
combined residue volumes, the signal is significant only at very low
evolutionary distances. Where the covariation compensates for changes in
the hydrogen bonding, the signal is strongest at intermediate evolutionary
distances. Covariations that compensate for charge variations appeared with
equal strength at all the evolutionary distances examined. A recipe is
suggested for using the weak covariation signal to assemble the predicted
secondary structural elements, where the evolutionary distance, covariation
type and weighting are considered together with the tertiary structural
context (interior or surface) of the residues being examined.
相似文献
77.
78.
79.
80.
P Rainville GH Duncan DD Price B Carrier MC Bushnell 《Canadian Metallurgical Quarterly》1997,277(5328):968-971
Recent evidence demonstrating multiple regions of human cerebral cortex activated by pain has prompted speculation about their individual contributions to this complex experience. To differentiate cortical areas involved in pain affect, hypnotic suggestions were used to alter selectively the unpleasantness of noxious stimuli, without changing the perceived intensity. Positron emission tomography revealed significant changes in pain-evoked activity within anterior cingulate cortex, consistent with the encoding of perceived unpleasantness, whereas primary somatosensory cortex activation was unaltered. These findings provide direct experimental evidence in humans linking frontal-lobe limbic activity with pain affect, as originally suggested by early clinical lesion studies. 相似文献