全文获取类型
收费全文 | 3928篇 |
免费 | 2篇 |
专业分类
化学工业 | 11篇 |
建筑科学 | 1篇 |
轻工业 | 2篇 |
石油天然气 | 4篇 |
一般工业技术 | 9篇 |
冶金工业 | 3900篇 |
自动化技术 | 3篇 |
出版年
2017年 | 1篇 |
2016年 | 1篇 |
2012年 | 1篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 6篇 |
1999年 | 106篇 |
1998年 | 1181篇 |
1997年 | 650篇 |
1996年 | 461篇 |
1995年 | 218篇 |
1994年 | 205篇 |
1993年 | 222篇 |
1992年 | 25篇 |
1991年 | 67篇 |
1990年 | 62篇 |
1989年 | 57篇 |
1988年 | 52篇 |
1987年 | 56篇 |
1986年 | 41篇 |
1985年 | 44篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 22篇 |
1980年 | 31篇 |
1979年 | 2篇 |
1978年 | 10篇 |
1977年 | 101篇 |
1976年 | 258篇 |
1975年 | 5篇 |
1972年 | 1篇 |
1964年 | 1篇 |
1955年 | 7篇 |
排序方式: 共有3930条查询结果,搜索用时 46 毫秒
81.
82.
83.
In this case report we describe the coincidental finding of polyps in the gallbladder by ultrasound investigation in a six-year-old girl, known to have metachromatic leukodystrophy. The investigation was carried out because of suspicion of abdominal trauma after falling down the stairs and finding elevated serum amylase. 相似文献
84.
VF Ferrario C Sforza A Puleo CE Poggio JH Schmitz 《Canadian Metallurgical Quarterly》1996,11(4):329-338
Analysis of genomic sequences is necessarily an ongoing process. Initial gene assignments tend (wisely) to be on the conservative side (Venter, 1996). The analysis of the genome then grows in an iterative fashion as additional data and more sophisticated algorithms are brought to bear on the data. The present report is an emendation of the original gene list of Methanococcus jannaschii (Bult et al., 1996). By using a somewhat more updated database and more relaxed (and operator-intensive) pattern matching methods, we were able to add significantly to, and in a few cases amend, the gene identification table originally published by Bult et al. (1996). 相似文献
85.
86.
87.
88.
It has recently been suggested that mitochondrial DNA (mtDNA) mutations are important contributors to human ageing and degenerative diseases. Using PCR techniques, we demonstrated three types of mtDNA length mutations, a 4977 bp deletion, a 7436 bp deletion and tandem duplications, in normal human skin tissues. We found that these mutations started to appear in the third decade of life, and the age at which the mutations could be detected in sun-exposed skin was usually younger than in non-exposed skin. Moreover, the incidences of these deletions and tandem duplications of mtDNA in sun-exposed skin were all significantly higher than those in non-exposed skin (P < 0.05). The 4977 bp deletion was the most prevalant mtDNA mutation in human skin, and the 7436 bp deletion was the least frequent among the three types of mtDNA mutations examined. We first demonstrated the existence of tandem duplications with sizes of about 260 bp, 200 bp and 150 bp in the D-loop region of mtDNA in the skin of elderly individuals. Among the three tandem duplications, the 200-bp duplication was found to occur most frequently in ageing skin. The tandem duplications were found to coexist with either or both of the deletions in some elderly individuals. The frequency of occurrence of mtDNA deletions and tandem duplications in skin was found to increase in an age-dependent manner. However, the incidence of tandem duplications was not well correlated with the age of the subject.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
89.
The glucose analog streptozotocin (STZ) has long been used as a tool for creating experimental diabetes because of its relatively specific beta-cell cytotoxic effect, but the mechanism by which systemic injection of STZ causes beta-cell destruction is not well understood. In the current study, we have used insulinoma (RIN) and AtT-20ins cell lines engineered for overexpression of GLUT2 or GLUT1 to investigate the role of glucose transporter isoforms in mediating STZ cytotoxicity. The in vivo effects of STZ were evaluated by implantation of RIN cells expressing or lacking GLUT2 into athymic nude rats. The drug had a potent cytotoxic effect on RIN cells expressing GLUT2, but had no effect on cells lacking GLUT2 expression, as indicated by histological analysis and measurement of the blood glucose levels of treated animals. The preferential cytotoxic effect of STZ on GLUT2-expressing cell lines was confirmed by in vitro analysis of GLUT2-expressing and untransfected RIN cells, as well as GLUT2- and GLUT1-overexpressing AtT-20ins cells. Consistent with these data, only GLUT2-expressing RIN or AtT-20ins cells transported STZ efficiently. We conclude that expression of GLUT2 is required for efficient killing of neuroendocrine cells by STZ, and this effect is related to specific recognition of the drug as a transported substrate by GLUT2 but not GLUT1. 相似文献
90.
JH Meurman 《Canadian Metallurgical Quarterly》1995,111(14):1328-1329