全文获取类型
收费全文 | 833篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 7篇 |
石油天然气 | 2篇 |
无线电 | 1篇 |
一般工业技术 | 1篇 |
冶金工业 | 822篇 |
自动化技术 | 1篇 |
出版年
2015年 | 1篇 |
2011年 | 2篇 |
2005年 | 1篇 |
2003年 | 3篇 |
1999年 | 26篇 |
1998年 | 253篇 |
1997年 | 156篇 |
1996年 | 99篇 |
1995年 | 37篇 |
1994年 | 44篇 |
1993年 | 56篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 12篇 |
1978年 | 3篇 |
1977年 | 26篇 |
1976年 | 64篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1959年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有834条查询结果,搜索用时 12 毫秒
71.
72.
73.
LM Sayre RT Naismith MA Bada WS Li ME Klein MD Tennant 《Canadian Metallurgical Quarterly》1996,1296(2):250-256
Horseradish peroxidase (HRP) is well known for mediating the electron-transfer oxidation of electron-rich aromatic 'donors' such as phenols and anilines, but has not been described to oxidize aliphatic amines. We here confirm the inability of HRP to oxidize typical aliphatic amines, even those which would exist significantly as free bases at the operative pH. In contrast, trans-2-phenylcyclopropylamine (2-PCPA) is both a substrate (turnover product is cinnamaldehyde) and a time-dependent inactivator of HRP. These activities of 2-PCPA are consistent with either a concerted or rapid sequential one-electron-oxidation/ring-opening to give an intermediate capable of covalent binding to the enzyme. 2-PCPA is the first known example of a simple aliphatic amine which serves as a substrate for HRP under turnover conditions. 相似文献
74.
During the first 2 wk of postnatal life, the rodent uterus undergoes a period of marked growth and differentiation. To further examine the role of the estrogen receptor (ER) in the mediation of uterine development, we analyzed the ontogeny of ER mRNA expression in the postnatal rat uterus using in situ hybridization. ER mRNA was present in the uterine stroma on the day of birth and progressively increased in abundance during the first 2 wk of postnatal life. In contrast, ER mRNA was not detectable in the luminal epithelium at birth and did not become abundant in this region until postnatal day (P) 7. ER mRNA abundance increased in the luminal epithelium and in the invaginating and fully formed glandular epithelium during the second week of life. At P21 ER mRNA was more abundant in the glandular epithelium than in any other uterine cell type. These results are consistent with, and extend the findings of, previous studies using uterine homogenate binding assays and immunohistochemistry to define ER ontogeny in rodents. Delineation of the temporal and cell-type specific pattern of ER mRNA ontogeny in the postnatal rat uterus furthers our understanding of the molecular basis of both endogenous and exogenous estrogen effects on uterine growth and development. 相似文献
75.
M Packer WS Colucci JD Sackner-Bernstein CS Liang DA Goldscher I Freeman ML Kukin V Kinhal JE Udelson M Klapholz SS Gottlieb D Pearle RJ Cody JJ Gregory NE Kantrowitz TH LeJemtel ST Young MA Lukas NH Shusterman 《Canadian Metallurgical Quarterly》1996,94(11):2793-2799
BACKGROUND: Carvedilol has improved the symptomatic status of patients with moderate to severe heart failure in single-center studies, but its clinical effects have not been evaluated in large, multicenter trials. METHODS AND RESULTS: We enrolled 278 patients with moderate to severe heart failure (6-minute walk distance, 150 to 450 m) and a left ventricular ejection fraction < or = 0.35 at 31 centers. After an open-label, run-in period, each patient was randomly assigned (double-blind) to either placebo (n = 145) or carvedilol (n = 133; target dose, 25 to 50 mg BID) for 6 months, while background therapy with digoxin, diuretics, and an ACE inhibitor remained constant. Compared with placebo, patients in the carvedilol group had a greater frequency of symptomatic improvement and lower risk of clinical deterioration, as evaluated by changes in the NYHA functional class (P = .014) or by a global assessment of progress judged either by the patient (P = .002) or by the physician (P < .001). In addition, treatment with carvedilol was associated with a significant increase in ejection fraction (P < .001) and a significant decrease in the combined risk of morbidity and mortality (P = .029). In contrast, carvedilol therapy had little effect on indirect measures of patient benefit, including changes in exercise tolerance or quality-of-life scores. The effects of the drug were similar in patients with ischemic heart disease or idiopathic dilated cardiomyopathy as the cause of heart failure. CONCLUSIONS: These findings indicate that, in addition to its favorable effects on survival, carvedilol produces important clinical benefits in patients with moderate to severe heart failure treated with digoxin, diuretics, and an ACE inhibitor. 相似文献
76.
A Apffel JA Chakel WS Hancock C Souders T M'Timkulu E Pungor 《Canadian Metallurgical Quarterly》1996,732(1):27-42
The application of high-performance liquid chromatography (HPLC), electrospray ionization mass spectrometry (ESI-MS) and matrix-assisted laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and selective enzymatic deglycosylation treatments is demonstrated in the analysis of glycosylation patterns in recombinant Desmodus salivary plasminogen activator, a heterogeneous glycoprotein. The sample was initially digested with a proteolytic enzyme (endoproteinase Lys-C) and then further treated with either PNGase F to remove N-linked carbohydrates or a combination of neuraminidase and O-glycosidase to remove sialic acid and O-linked carbohydrates. By comparison of the LC-ESI-MS peptide maps for the fully glycosylated and deglycosylated samples, it was possible to unambiguously identify the sites of N-linked glycosylation as well a number of N-linked glycopeptides. The O-link glycopeptides, which are present at low level ( < 1%), were not detected prior to the deglycosylation, nor could changes in peptide elution in the map following deglycosylation be correlated with potential O-linked glycosylation sites. 相似文献
77.
BB Simpson EM Reynolds SH Kim WS Ferguson F Graeme-Cook DP Doody 《Canadian Metallurgical Quarterly》1996,31(11):1577-1580
A 7-week-old boy presented with a 6-week history of failure to thrive, acute intestinal obstruction, and an apparently irreducible intussusception (noted on contrast enema). He underwent abdominal exploration, during which a cecal mass was identified and resected. The mass proved to be a leiomyosarcoma. Histologically, it was an intermediate-grade malignancy with a predicted 5-year survival rate of 16% to 23% based on data from the adult experience. Three years after resection and without having received adjuvant therapy, he is healthy and free of disease. A review of the literature showed that in infants these tumors are predominantly colonic, compared with the predilection for small intestinal lesions found in the older pediatric and adult populations. Infantile intestinal leiomyosarcomata are rare malignancies that do well if complete surgical excision of the disease can be accomplished. The histological prognostic indicators proposed for intestinal leiomyosarcomas in the adult population cannot be extrapolated to infants because when they occur in infants, they appear to be less aggressive, and these patients do well without adjuvant therapy. 相似文献
78.
79.
PURPOSE: The aim of this study was to determine the concentration of interleukin-1 alpha in human embryo culture medium with or without oviductal cell coculture and to correlate the interleukin-1 alpha levels with pregnancy. METHODS: Culture media from 32 in vitro fertilization and embryo transfer cycles were assayed for interleukin-1 alpha by immunoassay technique. Human embryos were cultured in Earles' balanced salt solution supplemented with 15% preovulatory serum (sEBSS) in 16 of these cycles, while embryos in the rest of the cycles were cocultured with human oviductal cells in sEBSS. RESULTS: Both sEBSS and spent sEBSS after embryo culture contained low or undetectable levels of interleukin-1 alpha in the pregnant and nonpregnant cycles. On the other hand, oviductal cells significantly increased the amount of interleukin-1 alpha immunoreactivity in the conventional culture medium or coculture medium (P < 0.001, Mann-Whitney rank sum test). The concentrations of interleukin-1 alpha in the spent sEBSS after oviductal cell culture and after coculture with human embryos were 1.5 +/- 1.0 and 1.3 +/- 0.9 pg/ml, respectively. There was no difference in the interleukin-1 alpha concentration between the pregnant and the nonpregnant coculture cycles. CONCLUSIONS: These data showed that human oviductal cells produced interleukin-1 alpha immunoreactivity in a coculture system. However, this production could not be used as a marker for successful embryo implantation. 相似文献
80.