全文获取类型
收费全文 | 2399篇 |
免费 | 0篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 5篇 |
建筑科学 | 1篇 |
轻工业 | 1篇 |
石油天然气 | 2篇 |
无线电 | 4篇 |
一般工业技术 | 6篇 |
冶金工业 | 2377篇 |
自动化技术 | 1篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 75篇 |
1998年 | 696篇 |
1997年 | 407篇 |
1996年 | 250篇 |
1995年 | 142篇 |
1994年 | 146篇 |
1993年 | 149篇 |
1992年 | 30篇 |
1991年 | 32篇 |
1990年 | 40篇 |
1989年 | 66篇 |
1988年 | 39篇 |
1987年 | 36篇 |
1986年 | 26篇 |
1985年 | 23篇 |
1983年 | 3篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 54篇 |
1976年 | 113篇 |
1975年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有2399条查询结果,搜索用时 0 毫秒
61.
EA Geiser DC Wilson DX Wang DA Conetta JD Murphy AD Hutson 《Canadian Metallurgical Quarterly》1998,11(4):338-348
An autonomous endocardial and epicardial boundary detection (ABD) method is reported. One hundred ten cycles from 55 clinical studies were selected retrospectively. Image sequences were digitized at 512 x 480 pixel resolution. The point-by-point boundary positions of the ABD and the areas enclosed were compared with positions and enclosed areas drawn by three independent observers. Correlation coefficients for epicardial end-diastolic (ED) and end-systolic (ES) areas, endocardial ED and ES areas, muscle area, and fractional area change were 0.970, 0.976, 0.951, 0.985, 0.887, and 0.878, respectively. Bland-Altman analysis showed negligible biases with standard deviations comparable to those of the observers. The mean difference between the ABD border and the consensus observer border positions in 64 directions falls within the mean range of interobserver border positions, suggesting that shape is also well defined by the ABD. 相似文献
62.
Upper gastrointestinal hemorrhage secondary to splenic vein thrombosis is a curable form of localized portal hypertension when treated with splenectomy. A high index of suspicion is necessary in order to promptly diagnose and treat this underrecognized condition that is most commonly caused by inflammation or neoplasm of the pancreas. The triad of isolated gastric varices, splenomegaly, and normal hepatic function is classic; it is not uncommon, however, for patients to have only some or even none of these conditions. Mesenteric angiography with venous phase imaging is the gold standard of diagnosis. Ultrasound and CT may identify splenic vein thrombosis, but are most helpful in delineating concomitant upper abdominal pathology. Early recognition and intervention allow associated underlying conditions to be treated under the same anesthetic with minimal morbidity and mortality. 相似文献
63.
DC Underwood S Bochnowicz RR Osborn CJ Kotzer MA Luttmann DW Hay PD Gorycki SB Christensen TJ Torphy 《Canadian Metallurgical Quarterly》1998,287(3):988-995
We evaluated the airway activity of the novel phosphodiesterase type 4 inhibitor SB 207499 [Ariflo; c-4-cyano-4-(3-cyclopentyloxy-4-methoxyp henyl-r-1-cyclohexane carboxylic acid)], in the guinea pig. Ovalbumin (OA)-induced contractions of guinea pig isolated tracheal strips were inhibited by SB 207499 with an EC50 of 1 microM but had little or no effect on exogenous agonist-induced contraction, which suggests that its effect on OA-induced contraction in vitro is primarily due to inhibition of mediator release from mast cells. In anesthetized guinea pigs, SB 207499 inhibited OA-induced bronchoconstriction with i.v. and p.o. ID50 values of 1.7 and 17 mg/kg, respectively. At 1, 3 and 6 hr after SB 207499 (30 mg/kg p.o.), OA-induced bronchospasm was inhibited by 92%, 70% and 58%, respectively, corresponding to elevated plasma concentrations of 1.62 +/- 0.19, 1.65 +/- 0.29 and 0. 93 +/- 0.24 microg/ml, respectively, of SB 207499. SB 207499 also inhibited house dust mite-induced bronchoconstriction (ID50 = 0.9 mg/kg i.v. and 8.9 mg/kg p.o.). In contrast to its lack of bronchorelaxant activity in vitro, SB 207499 inhibited bronchospasm induced by i.v. leukotriene D4 (LTD4) [ID50 = 3 mg/kg i.v.]. The bronchorelaxant effect of i.v.-administered SB 207499 was at least additive with that of salbutamol in reversing infused histamine-enhanced airway tone, but it did not alter base line or enhance salbutamol-induced cardiovascular effects. In conscious guinea pigs, SB 207499 (10 or 30 mg/kg p.o.), 1 hr before antigen or LTD4 challenge, markedly reduced bronchospasm and subsequent eosinophil influx as measured by bronchoalveolar lavage 24 hr after provocation. SB 207499 administered after OA or LTD4 challenge also reduced airway eosinophilia measured at 24 hr after OA challenge or 96 hr after LTD4 challenge. These results, coupled with the broad anti-inflammatory activity of SB 207499 previously described (Barnett et al., 1998), suggest that SB 207499 will be useful in the treatment of asthma and other inflammatory disorders. 相似文献
64.
65.
DL Kraitchman AA Young DC Bloomgarden ZA Fayad L Dougherty VA Ferrari RC Boston L Axel 《Canadian Metallurgical Quarterly》1998,40(2):311-326
A single integrated examination using regional measurements of perfusion from contrast-enhanced MRI and three-dimensional (3D) strain from tissue-tagged MRI was developed to differentiate infarcted myocardium from adjacent tissue with functional abnormalities. Ten dogs were studied at baseline and 10 days after a 2-hour occlusion of the left anterior descending coronary artery (LAD). Strain was determined using a 3D finite element model. Two-dimensional measurements of hypoenhancing regions were highly correlated with myocardial viability (r = 0.96). Signal intensity versus time curves obtained from contrast-enhanced MRI were used for quantitative perfusion analysis. The remote and adjacent noninfarcted tissue of the dogs with LAD occlusion, as well as the infarcted tissue, exhibited abnormal deformation patterns as compared to normal dogs (positive predictive value (PPV) of strain determination of infarction = 66%). Integration of contrast-enhanced MRI results with 3D strain analysis enabled the delineation of the myocardial infarction (PPV = 100%) from functionally compromised myocardium. This integrated cardiac examination shows promise for noninvasive serial assessment of potentially jeopardized noninfarcted myocardium to study the process of infarct remodeling and expansion. 相似文献
66.
67.
68.
DC McAvoy CP Grady J Blok TC Feijtel TW Federle RJ Larson 《Canadian Metallurgical Quarterly》1998,36(10):2291-2304
Various mathematical relationships have been used to assess exposure concentrations of organic chemicals when emissions occur via wastewater treatment. These relationships range from a simple removal factor calculation to more sophisticated approaches using kinetic based mathematical models. While these existing approaches have been used by decision makers to screen new chemicals for exposure assessments, they all have limitations in the predictive capabilities. Thus, a simplified modeling approach grounded in sound scientific fundamentals that utilizes relatively easy to obtain input parameters is needed. In this paper a simplified modeling approach that utilizes microbial growth kinetics was developed for predicting effluent concentrations in secondary biological wastewater treatment systems. Receiving water predicted exposure concentrations (PEC) are assessed by using a dilution factor. One advantage of this approach is that it allows for wastewater treatment plant effluent concentrations, and therefore receiving water exposure levels, to be predicted with a minimum amount of experimental data. It also provides quantitative data that can be used to assess the relative biodegradability of different chemicals for use in regulatory and risk assessment activities. 相似文献
69.
70.