全文获取类型
收费全文 | 790篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 57篇 |
金属工艺 | 7篇 |
机械仪表 | 14篇 |
建筑科学 | 17篇 |
矿业工程 | 4篇 |
能源动力 | 16篇 |
轻工业 | 31篇 |
水利工程 | 5篇 |
石油天然气 | 2篇 |
无线电 | 68篇 |
一般工业技术 | 89篇 |
冶金工业 | 435篇 |
原子能技术 | 8篇 |
自动化技术 | 37篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 17篇 |
2012年 | 13篇 |
2011年 | 12篇 |
2010年 | 14篇 |
2009年 | 15篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 12篇 |
2005年 | 20篇 |
2004年 | 9篇 |
2003年 | 8篇 |
2002年 | 16篇 |
2001年 | 8篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 84篇 |
1997年 | 49篇 |
1996年 | 42篇 |
1995年 | 31篇 |
1994年 | 37篇 |
1993年 | 32篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 20篇 |
1988年 | 33篇 |
1987年 | 28篇 |
1986年 | 19篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1975年 | 6篇 |
1974年 | 9篇 |
1972年 | 4篇 |
1968年 | 2篇 |
1933年 | 2篇 |
排序方式: 共有800条查询结果,搜索用时 15 毫秒
651.
Cherry juice from one cultivar was fermented for 0, 24, 48, and 72 h using Lactobacillus acidophilus, and its effects related to management of hyperglycemia, hypertension, inhibition of Helicobacter pylori, and proliferation of probiotic Bifidobacterium longum were evaluated using in vitro models. Cherry extract was fermented by initially adjusting the pH to 6.0 and at the natural acidic pH. Analysis was carried out by adjusting the pH and at fermented acidic pH at each time point from each of the two samples. Total soluble phenolics decreased over a period of 72 h for initial pH adjusted samples whereas it increased or remained constant for natural acidic pH samples. DPPH linked antioxidant activity and α-glucosidase inhibitory activity decreased for samples where final pH was adjusted whereas it increased for natural acidic pH samples. Fermentation led to a decrease in hypertension-relevant ACE inhibitory activity for all samples. Natural acidic pH samples had Helicobacter pylori inhibitory activity at 24, 48 and 72 h. Based on the rationale that simple phenolics in cherry could behave as proline analogs, the potential recovery of the pathogen from inhibition was evaluated with of addition of 0.5 mM proline in the medium. A proline induced growth recovery was observed indicating that the mechanism of inhibition is related to proline dehydrogenase based oxidative phosphorylation. Overall, no inhibition was observed when samples that had H. pylori inhibitory activity were further evaluated for their effect on probiotic Bifidobacterium longum. 相似文献
652.
Steven E. Naleway Rawley B. Greene Bernd Gludovatz Neil K. N. Dave Robert O. Ritchie Jamie J. Kruzic 《Metallurgical and Materials Transactions A》2013,44(13):5688-5693
The strength-normalized fatigue endurance strength of the bulk metallic glass (BMG) Zr52.5Cu17.9Ni14.6Al10Ti5 (Vitreloy 105) has been reported to be the highest for any BMG; however, to date, there has been no explanation of why this material is so much better than other Zr-based compositions. In this study, the fatigue-crack growth behavior of Zr52.5Cu17.9Ni14.6Al10Ti5 was compared in ambient air vs dry nitrogen environment. The excellent fatigue life behavior is attributed to a relatively high fatigue threshold (ΔK TH ≈ 2 MPa√m) and a lack of sensitivity to environmental effects on fatigue-crack growth in ambient air, as compared to other Zr-based BMGs. Fatigue life experiments conducted in ambient air confirmed the excellent fatigue life properties with a 107-cycle endurance strength of ~0.24 of the ultimate tensile strength; however, it was also found that casting porosity, even in limited amounts, could reduce this endurance strength by as much as ~60 pct. Overall, the BMG Zr52.5Cu17.9Ni14.6Al10Ti5 appears to have excellent strength and fatigue properties and should be considered as a prime candidate material for future applications where good mechanical fatigue resistance is required. 相似文献
653.
Charles H. Greene 《技术计量学》2013,55(4):875-876
Confidence intervals based on the maximum likelihood estimators are given for the location and scale parameters of the Double Exponential distribution. These intervals are obtained by determining the distribution of the pivotal quantities ( – θ)/ and /σ. Exact distributions are determined for n = 3 and n = .5, and approximate distributions are provided for larger n. The asymptotic distributions are also given and the accluacy of these approximations are investigated. The powers of the associated tests of hypotheses are given and tolerance limits for the population are also provided. Some possible applications are indicated. 相似文献
654.
Prochaska James O.; Velicer Wayne F.; Rossi Joseph S.; Redding Colleen A.; Greene Geoffrey W.; Rossi Susan R.; Sun Xiaowu; Fava Joseph L.; Laforge Robert; Plummer Brett A. 《Canadian Metallurgical Quarterly》2004,23(5):503
Three stage-based expert system interventions for smoking, high-fat diet, and unsafe sun exposure were evaluated in a sample of 2,460 parents of teenagers. Eighty-four percent of the eligible parents were enrolled in a 2-arm randomized control trial, with the treatment group receiving individualized feedback reports for each of their relevant behaviors at 0, 6, and 12 months as well as a multiple behavior manual. At 24 months, the expert system outperformed the comparison condition across all 3 risk behaviors, resulting in 22% of the participants in action or maintenance for smoking (vs. 16% for the comparison condition), 34% for diet (vs. 26%), and 30% for sun exposure (vs. 22%). Proactive, home-based, and stage-matched expert systems can produce significant multiple behavior changes in at-risk populations where the majority of participants are not prepared to change. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
655.
When Ss are required to recall lists containing both words and digits, memory span is higher when the digits precede the words than when the words precede the digits. In Exp 1, both forward and backward recall were tested; it was demonstrated that this category-order effect reflects the input position, and not the output position, of the items. Exp 2 revealed that this effect was not eliminated by a filled retention interval. Exp 3 showed that the effect was eliminated when lists were presented at a fast presentation rate. In Exp 4, the effect was eliminated when Ss engaged in articulatory suppression. A 5th experiment extended the findings of Exp 4 to the case in which lists are composed of semantically related or unrelated words. These results suggest that category-order effects reflect mnemonic activity that Ss engage in during list presentation and do not arise from structural characteristics of the memory system. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
656.
It is widely recognized that the distribution of technetium-99m-labeled d,l-hexamethylpropylene amine oxime (99mTc-HMPAO) in the brain is determined by the regional blood flow. However, other factors may affect this process including the metabolism of the brain tissue. To examine this possibility we studied the effects of metabolic alterations on 99mTc-HMPAO uptake in rat brain cortex slices, with concurrent measurement of oxygen consumption (QO2). 99mTc-HMPAO uptake was determined by incubating slices of rat cerebral cortex at 37 degrees C in Krebs-Ringer phosphate glucose medium containing 99mTc-HMPAO with and without test substances. Differential gradients for 99mTc activity between the tissue and the suspending medium (T/M ratio) were derived from the equation T/M[99mTc] = counts per gram of tissue/counts per milliliter of medium. The QO2 of the brain slices was measured using a biological oxygen monitor equipped with a polarographic oxygen probe. Inhibitors affecting oxidative phosphorylation caused parallel suppression of the T/M ratio and QO2. Agents that uncouple oxidation from phosphorylation increased the QO2 and decreased the T/M ratio. Incubation of slices at 22 degrees C depressed the T/M ratio and QO2. The presence of inhibitors of oxidative phosphorylation in the incubation medium increased the release of 99mTc activity from slices that had been prelabeled with 99mTc-HMPAO. These findings suggest that the altered metabolic status of the brain tissue modulates the kinetics and net accumulation of 99mTc-HMPAO at the cellular level by either depressing uptake, increasing back-diffusion, or both. 相似文献
657.
KC Allman MJ Stevens DM Wieland GD Hutchins ER Wolfe DA Greene M Schwaiger 《Canadian Metallurgical Quarterly》1993,22(5):1425-1432
OBJECTIVES: The purpose of this investigation was to evaluate the sympathetic nervous system of the heart by positron emission tomographic (PET) imaging in patients with diabetes mellitus with and without diabetic autonomic neuropathy. BACKGROUND: The clinical assessment of cardiac involvement in diabetic autonomic neuropathy has been limited to cardiovascular reflex testing. With the recent introduction of radiolabeled catecholamines such as carbon (C)-11 hydroxyephedrine, the sympathetic innervation of the heart can be specifically visualized with PET imaging. METHODS: Positron emission tomographic imaging was performed with C-11 hydroxyephedrine and rest myocardial blood flow imaging with nitrogen-13 ammonia. Three patient groups were studied, including healthy volunteers as control subjects, diabetic patients with normal autonomic function testing and diabetic patients with varying severity of autonomic neuropathy. Homogeneity of cardiac tracer retention as well as absolute tracer retention was determined by relating myocardial tracer retention to an arterial C-11 activity input function. RESULTS: Abnormal regional C-11 hydroxyephedrine retention was seen in seven of eight patients with autonomic neuropathy. Relative tracer retention was significantly reduced in apical, inferior and lateral segments. The extent of the abnormality correlated with the severity of conventional markers of autonomic dysfunction. Absolute myocardial tracer retention index measurements showed a 45 +/- 21% decrease in distal compared with proximal myocardial segments in autonomic neuropathy (0.069 +/- 0.037 min-1 vs. 0.13 +/- 0.052 min-1, p = 0.02). CONCLUSIONS: This study demonstrates a heterogeneous pattern of neuronal abnormalities in patients with diabetic cardiac neuropathy. The extent of this abnormality correlated with the severity of neuropathy assessed by conventional tests. Future studies in larger groups of patients are required to define the relative sensitivity of this imaging approach in detecting cardiac neuropathy and to determine the clinical significance of these scintigraphic findings in comparison with conventional markers of autonomic innervation. 相似文献
658.
J Barrette R Bellwied P Braun-Munzinger WE Cleland TM Cormier G David J Dee GE Diebold O Dietzsch JV Germani S Gilbert SV Greene JR Hall TK Hemmick N Herrmann B Hong K Jayananda D Kraus BS Kumar R Lacasse D Lissauer WJ Llope TW Ludlam S McCorkle R Majka SK Mark JT Mitchell M Muthuswamy E O'Brien C Pruneau MN Rao F Rotondo NC daSilva U Sonnadara J Stachel H Takai EM Takagui TG Throwe C Winter G Wang D Wolfe CL Woody N Xu Y Zhang Z Zhang C Zou 《Canadian Metallurgical Quarterly》1994,50(6):3047-3059
659.
In the recent past, compliance with 21CFR11 has become a major buzzword within the pharmaceutical and biotechnology industries. While commercial solutions exist, implementation and validation are expensive and cumbersome. Frequent implementation of new features via point releases further complicates purchasing decisions by making it difficult to weigh the risk of non-compliance against the costs of too frequent upgrades. This presentation discusses a low-cost interim solution to the problem. While this solution does not address 100% of the issues raised by 21CFR11, it does implement and validate: (1) computer system security; (2) backup and restore ability on the electronic records store; and (3) an automated audit trail mechanism that captures the date, time and user identification whenever electronic records are created, modified or deleted. When coupled with enhanced procedural controls, this solution provides an acceptable level of compliance at extremely low cost. 相似文献
660.
Krusius J.P. Seraphim D.P. Greene R.G. Skinner D.S. Yost B. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2002,90(4):559-580
Ultralarge active-matrix liquid-crystal displays (AMLCD) and plasma display panels (PDP) are both being developed as flat-panel display (FPD) competitors to the bulky cathode-ray tube for color video and monitor applications. The visual requirements for ultralarge FPDs are defined and their limits quantitatively delineated Tiling, with or without seams, has been shown to provide the only path to ultralarge FPD sizes not accessible today with monolithic construction. The design, manufacturing, and characteristics of tiled AMLDs is described in detail. The 37.5-in tiled color-video AMLCD recently demonstrated by Rainbow Displays Inc. is used as the primary illustration. The limits of tiling will also be delineated. Finally, the relative strengths of the PDP and the AMLCD in ultralarge FPD applications will be assessed 相似文献