全文获取类型
收费全文 | 897篇 |
免费 | 15篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 57篇 |
化学工业 | 150篇 |
金属工艺 | 69篇 |
机械仪表 | 22篇 |
建筑科学 | 21篇 |
能源动力 | 19篇 |
轻工业 | 74篇 |
水利工程 | 9篇 |
无线电 | 71篇 |
一般工业技术 | 125篇 |
冶金工业 | 204篇 |
原子能技术 | 23篇 |
自动化技术 | 71篇 |
出版年
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 14篇 |
2015年 | 5篇 |
2014年 | 18篇 |
2013年 | 47篇 |
2012年 | 41篇 |
2011年 | 46篇 |
2010年 | 22篇 |
2009年 | 31篇 |
2008年 | 46篇 |
2007年 | 38篇 |
2006年 | 38篇 |
2005年 | 21篇 |
2004年 | 30篇 |
2003年 | 24篇 |
2002年 | 16篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 17篇 |
1998年 | 83篇 |
1997年 | 46篇 |
1996年 | 37篇 |
1995年 | 28篇 |
1994年 | 23篇 |
1993年 | 20篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 11篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1971年 | 2篇 |
排序方式: 共有915条查询结果,搜索用时 10 毫秒
871.
872.
873.
874.
875.
We have identified the three genes pssCDE in Rhizobium leguminosarum bv. trifolii TA1. Even though they were almost identical to earlier identified pssCDE genes of R. leguminosarum, they differed in gene lengths and gene overlaps. The predicted gene products of pssCDE genes shared significant homology to prokaryotic glycosyl transferases involved in exopolysaccharide synthesis. The Tn5 insertion in pssD created the nonmucoid mutant that induced non-nitrogen-fixing nodules. The microscopic analysis of the nodules, induced on Trifolium pratense by the pssD133 mutant, showed abnormally enlarged infection threads densely packed with bacteria, which were released from the infection threads in an unusual way. The symbiosomes were observed very rarely and the nodule remained almost empty. Symbiotic phenotype of the pssD133 suggested a correlation between this mutation and defective endocytosis of bacteria into nodule cells. 相似文献
876.
877.
The tablets prepared by the direct compression of spray-dried particles of a drug and zein were evaluated in vitro. The release of drug from the tablets was retarded compared with drug powder alone and tablets prepared from the physical mixtures. Drug release from the tablets was controlled by changing drug content and tablet, weight. 相似文献
878.
879.
We isolated and characterized a new gene related to the control of cell division regulation in Escherichia coli. At 30 degrees C, the dnaAcos mutant causes over-replication of the chromosome, and colony formation is inhibited. We found that, at this temperature, the dnaAcos cells form filaments; therefore, septum formation is inhibited. This inhibition was independent of SfiA, an inhibitor of the septum-forming protein, FtsZ. To identify factors involved in this pathway of inhibition, we isolated seven multicopy suppressors for the cold-sensitive phenotype of the dnaAcos mutant. One of these proved to be a previously unknown gene, which we named cedA. This gene encoded a 12 kDa protein and resided at 38.9min on the E. coli genome map. A multicopy supply of the cedA gene to the dnaAcos cells did not repress over-replication of the chromosome but did stimulate cell division of the host, the result being growth of cells with an abnormally elevated chromosomal copy number. Therefore, the expression level of the cedA gene seems to be important for inhibiting cell division of the dnaAcos mutant at 30 degrees C. We propose that over-replication of the chromosome activates a pathway for inhibiting cell division and that the cedA gene modulates this division control. In the dnaA+ background, cedA also seems to affect cell division. 相似文献
880.
Studies have been carried out on the polymerization of vinyl phosphonate oligomer in a form of thin liquid layer induced by electron-beam irradiation under various reaction conditions. It was found that the dose-rate exponent on the rate of polymerization was 0.92, that the presence of remaining diluent below 10% did not disturb the polymerization, but that the presence of oxygen retarded the reaction when the film thickness was as thin as 20μm. Intermittent irradiation was effective to increase the conversion to the polymer. © 1995 John Wiley & Sons, Inc. 相似文献