全文获取类型
收费全文 | 584篇 |
免费 | 0篇 |
专业分类
化学工业 | 2篇 |
金属工艺 | 1篇 |
轻工业 | 1篇 |
无线电 | 3篇 |
一般工业技术 | 9篇 |
冶金工业 | 567篇 |
原子能技术 | 1篇 |
出版年
2015年 | 1篇 |
2012年 | 2篇 |
2011年 | 3篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2007年 | 1篇 |
2001年 | 1篇 |
1999年 | 19篇 |
1998年 | 185篇 |
1997年 | 92篇 |
1996年 | 55篇 |
1995年 | 26篇 |
1994年 | 24篇 |
1993年 | 32篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 26篇 |
1976年 | 53篇 |
1975年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有584条查询结果,搜索用时 0 毫秒
581.
582.
To delineate the complexity of the response of cells to nanoparticles we have performed a study on HT-29 human colon carcinoma cells exposed first to a fullerene derivative C(60)(OH)(20) and then to physiological copper ions. Our cell viability, proliferation, and intracellular reactive oxygen species (ROS) production assays clearly indicated that C(60)(OH)(20) suppressed cell damage as well as ROS production induced by copper, probably through neutralization of the metal ions by C(60)(OH)(20) in the extracellular space, as well as by adsorption and uptake of the nanoparticles surface-modified by the biomolecular species in the cell medium. This double-exposure study provides new data on the effects of nanoparticles on cell metabolism and may aid the treatment of oxidant-mediated diseases using nanomedicine. 相似文献
583.
D D'Antona PM Mamers PJ Lowe N Balazs NP Groome EM Wallace 《Canadian Metallurgical Quarterly》1998,13(8):2305-2307
Tubal pregnancy is now commonly managed by laparoscopic salpingostomy or systemic methotrexate. A disadvantage of such conservative management is the need for appropriate follow-up, with serial measurement of serum concentrations of human chorionic gonadotrophin (HCG), to exclude persistent ectopic pregnancy (PEP). Concentrations of inhibin A, also a placental product, are significantly increased during pregnancy and the half-life of inhibin A is significantly shorter than that of HCG. To assess the suitability of inhibin A as a marker of PEP, we studied 16 women who had undergone surgery for a tubal pregnancy, measuring HCG and inhibin during follow-up. The mean +/- SEM time taken to achieve non-pregnant concentrations of inhibin A was significantly shorter than for HCG (4.2 +/- 0.8 days versus 21.6 +/- 4.4 days respectively; P < 0.001 Wilcoxon signed rank test). However, in all women the inhibin A concentration increased rapidly after reaching a nadir, reflecting the return of ovarian function, complicating the interpretation of results. In four women inhibin A was almost undetectable preoperatively, while the corresponding HCG concentration was high. These data suggest that inhibin A will not be a useful marker for PEP but that it may provide a more accurate preoperative assessment of trophoblast viability than HCG, thereby improving management. 相似文献
584.
KS Hathcock NP Weng R Merica MK Jenkins R Hodes 《Canadian Metallurgical Quarterly》1998,160(12):5702-5706
Telomeres, structures on the ends of linear chromosomes, function to maintain chromosomal integrity. Telomere shortening occurs with cell division and provides a mechanism for limiting the replicative potential of normal human somatic cells. Telomerase, a ribonucleoprotein enzyme, synthesizes telomeric repeats on chromosomal termini, potentially extending the capacity for cell division. The present study demonstrates that resting T cells express little/no activity, and optimal Ag-specific induction of telomerase activity in vitro requires both TCR and CD28-B7 costimulatory signals. Regulation of telomerase in T cells during in vivo Ag-dependent activation was also assessed by adoptive transfer of TCR transgenic T cells and subsequent Ag challenge. Under these conditions, telomerase was induced in transgenic T cells coincident with a phase of extensive clonal expansion. These findings suggest that telomerase may represent an adoptive response that functions to preserve replicative potential in Ag-reactive lymphocytes. 相似文献