全文获取类型
收费全文 | 6765篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 22篇 |
金属工艺 | 1篇 |
机械仪表 | 1篇 |
能源动力 | 1篇 |
轻工业 | 6篇 |
石油天然气 | 2篇 |
无线电 | 6篇 |
一般工业技术 | 12篇 |
冶金工业 | 6707篇 |
原子能技术 | 1篇 |
自动化技术 | 7篇 |
出版年
2014年 | 1篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 11篇 |
2002年 | 2篇 |
2000年 | 4篇 |
1999年 | 213篇 |
1998年 | 2301篇 |
1997年 | 1280篇 |
1996年 | 807篇 |
1995年 | 421篇 |
1994年 | 336篇 |
1993年 | 414篇 |
1992年 | 37篇 |
1991年 | 47篇 |
1990年 | 53篇 |
1989年 | 47篇 |
1988年 | 54篇 |
1987年 | 56篇 |
1986年 | 53篇 |
1985年 | 36篇 |
1984年 | 1篇 |
1983年 | 18篇 |
1982年 | 24篇 |
1981年 | 30篇 |
1980年 | 61篇 |
1979年 | 3篇 |
1978年 | 13篇 |
1977年 | 136篇 |
1976年 | 277篇 |
1975年 | 11篇 |
1973年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有6766条查询结果,搜索用时 45 毫秒
261.
262.
B Tse JM Balkovec CM Blazey MJ Hsu J Nielsen D Schmatz 《Canadian Metallurgical Quarterly》1998,8(16):2269-2272
Sordarin (1) was converted to 5 and 6, which showed potent antifungal activity against yeast. A series of C1-C9 alkyl side-chain derivatives was prepared, from which it was found that the optimal activity occurred with C5. A comparison of side chains with different unsaturation showed that the cis-alkene was the most active. This result suggested that the folding of the side chains might be crucial for the optimal activity. 相似文献
263.
LC Maroto Y Carrascal MJ López A Forteza A Pérez C Zavanella 《Canadian Metallurgical Quarterly》1998,66(6):2110-2111
An asymptomatic cardiac cyst located in the interventricular septum was diagnosed in a 3.5-year-old child by echocardiographic findings. Surgical ablation was done and histopathologic analysis confirmed a hydatid cyst. The patient was discharged without symptoms. 相似文献
264.
We combined histofluorescence with in situ hybridization to identify GABAergic neurons in the arcuate nucleus (ARC) following electrophysiological recordings, using GAD65 as a marker. Intracellular recordings were made in hypothalamic slices prepared from ovariectomized guinea pigs. Over 90% of ARC neurons tested with the GABA(B) receptor agonist baclofen responded with a membrane hyperpolarization or an outward current. The hyperpolarization was dose-dependent, and the GABA(B) receptor antagonist CGP 35,348 produced a rightward shift in the agonist dose-response curve. Agonist potency was lower, and the efficacy greater, in GAD-positive neurons. The use of this novel technique for identifying GABAergic neurons thus reveals differences in the pharmacodynamics of GABA(B) receptor activation GABAergic and non-GABAergic ARC neurons. 相似文献
265.
Cholinergic blockade and the mesenteric artery response to head-up tilt-induced central hypovolaemia
The methylation of phosphatidylethanolamine is an auxiliary pathway for phosphatidylcholine biosynthesis in liver. Two forms of the enzyme, phosphatidylethanolamine N-methyltransferase, which catalyses this reaction, are located on the endoplasmic reticulum and mitochondria-associated membranes. Both forms are encoded by a single murine gene, Pempt, located on chromosome 11. The expression of the gene begins at birth. An inverse relationship exists between the rate of liver growth and the expression of phosphatidylethanolamine N-methyltransferase. However, disruption of the Pempt gene does not alter liver growth in mice or cause any other obvious phenotype. 相似文献
266.
267.
Video-assisted thoracic surgery thymectomy was employed in the management of myasthenia gravis in a series of 20 patients. As the technique evolved, the authors preferred a right-sided approach, and the technical details of the process are discussed. At a mean follow-up of 30 months, clinical results are comparable to published series of other approaches. It is hoped that the superior cosmesis associated with this less-invasive approach leads to earlier thymectomy in management of this disease. 相似文献
268.
JL Bowtell GP Leese K Smith PW Watt A Nevill O Rooyackers AJ Wagenmakers MJ Rennie 《Canadian Metallurgical Quarterly》1998,85(5):1744-1752
The aim of this study was to investigate dietary protein-induced changes in whole body leucine turnover and oxidation and in skeletal muscle branched chain 2-oxo acid dehydrogenase (BCOADH) activity, at rest and during exercise. Postabsorptive subjects received a primed constant infusion of L-[1-13C,15N]leucine for 6 h, after previous consumption of a high- (HP; 1.8 g . kg-1 . day-1, n = 8) or a low-protein diet (LP; 0.7 g . kg-1 . day-1, n = 8) for 7 days. The subjects were studied at rest for 2 h, during 2-h exercise at 60% maximum oxygen consumption, then again for 2 h at rest. Exercise induced a doubling of both leucine oxidation from 20 micromol . kg-1 . h-1 and BCOADH percent activation from 7% in all subjects. Leucine oxidation was greater before (+46%) and during (+40%, P < 0.05) the first hour of exercise in subjects consuming the HP rather than the LP diet, but there was no additional change in muscle BCOADH activity. The results suggest that leucine oxidation was increased by previous ingestion of an HP diet, attributable to an increase in leucine availability rather than to a stimulation of the skeletal muscle BCOADH activity. 相似文献
269.
270.
OBJECTIVE: To reveal the relationship between fasting and 2-h postload plasma glucose and to examine the appropriate fasting glucose cutoff as the primary screening test for diabetes. RESEARCH DESIGN AND METHODS: We recruited 5,303 subjects from preventive services of the National Cheng Kung University Hospital. Exclusion criteria were age <20 years, pregnancy, known diabetes, and a history of recent surgery, trauma, or illness. All subjects received the 75-g oral glucose tolerance test. The relationship between fasting and 2-h glucose was examined. Sensitivities, specificities, efficiency, and predictive values were assessed at different cutoffs of fasting glucose for prediction of diabetes. RESULTS: The best fit model for the relationship between fasting and 2-h glucose was fasting glucose = 4.914-0.060 x (2-h glucose) + 0.0144 x (2-h glucose)2. From this model, the fasting glucose was 6.0 mmol/l when 2-h glucose was 11.1 mmol/l. A fasting glucose with 6.25 mmol/l gave the same diabetes prevalence as the World Health Organization 2-h glucose criterion. When 7.8 mmol/l was the fasting glucose cutoff, the sensitivity was 28.5%. Lowering the cutoff from 7.8 to 7.0 mmol/l increased the sensitivity by 11.2% and slightly reduced the specificity and positive predictive value. If the cutoffs were 6.25 and 6.0 mmol/l, the sensitivity increased and the specificity and the positive predictive value decreased accordingly. CONCLUSIONS: Our results suggest that fasting glucose as a screening criterion for diabetes could be revised downward to 7.0 mmol/l, because the slight reduction of positive predictive value was more than balanced by an apparent increase of sensitivity and insignificant change of specificity. 相似文献