全文获取类型
收费全文 | 3881篇 |
免费 | 36篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 299篇 |
金属工艺 | 49篇 |
机械仪表 | 62篇 |
建筑科学 | 63篇 |
矿业工程 | 5篇 |
能源动力 | 58篇 |
轻工业 | 128篇 |
水利工程 | 6篇 |
石油天然气 | 15篇 |
无线电 | 206篇 |
一般工业技术 | 314篇 |
冶金工业 | 2469篇 |
原子能技术 | 13篇 |
自动化技术 | 216篇 |
出版年
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 12篇 |
2019年 | 19篇 |
2017年 | 20篇 |
2016年 | 21篇 |
2015年 | 18篇 |
2014年 | 24篇 |
2013年 | 105篇 |
2012年 | 32篇 |
2011年 | 72篇 |
2010年 | 49篇 |
2009年 | 45篇 |
2008年 | 54篇 |
2007年 | 53篇 |
2006年 | 58篇 |
2005年 | 59篇 |
2004年 | 49篇 |
2003年 | 45篇 |
2002年 | 38篇 |
2001年 | 45篇 |
2000年 | 45篇 |
1999年 | 97篇 |
1998年 | 777篇 |
1997年 | 418篇 |
1996年 | 270篇 |
1995年 | 194篇 |
1994年 | 184篇 |
1993年 | 194篇 |
1992年 | 53篇 |
1991年 | 48篇 |
1990年 | 43篇 |
1989年 | 57篇 |
1988年 | 45篇 |
1987年 | 50篇 |
1986年 | 38篇 |
1985年 | 45篇 |
1984年 | 15篇 |
1983年 | 35篇 |
1982年 | 39篇 |
1981年 | 29篇 |
1980年 | 43篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 70篇 |
1976年 | 126篇 |
1975年 | 16篇 |
1974年 | 13篇 |
1973年 | 14篇 |
1972年 | 12篇 |
排序方式: 共有3920条查询结果,搜索用时 15 毫秒
1.
van Schoor G. van Wyk J.D. Shaw I.S. 《Industrial Electronics, IEEE Transactions on》2003,50(3):546-553
A hybrid power compensator (HPC) consisting of a static VAr compensator and a dynamic compensator needs to be optimally controlled during the compensation of nonlinear loads. The HPC must be controlled to meet minimum requirements in terms of power factor and harmonic distortion, while at the same time minimizing its total cost. An artificial neural network (ANN) is used to control the HPC amidst a very dynamic power system environment. The performance of a reference ANN is evaluated while controlling an HPC connected to a typical nonlinear industrial load. The training and performance of the ANN is then optimized in terms of training set size, training set packing and ANN topology and the performance compared to the reference ANN. This paper highlights the importance of optimising the mentioned ANN parameters to achieve optimum ANN training and modeling accuracy. The results obtained reveals that the application of an ANN in controlling an HPC is feasible given that the ANN parameters are chosen appropriately. 相似文献
2.
ABSTRACT: Shellac and wax-based citrus coatings were applied to Fallglo, Robinson, Sunburst, Dancy and Murcott tangerines, Nova and Orlando tangelos, and Temple oranges. Flavor volatiles were measured before and after storage. Concentrations of ethyl acetate, ethyl butyrate, isopentanol and 2-methyl-3-buten-2-ol increased markedly for fruit with shellac-based coatings, and were highly correlated with ethanol content, but at different ratios for the different varieties. The concentration increases were relatively less for fruit coated with the wax-based coatings, and suggest that high-gloss shellac and resin-based coatings are not appropriate for tangerines. 相似文献
3.
J Westhuyzen AD Cochrane PJ Tesar T Mau DB Cross MP Frenneaux FA Khafagi SJ Fleming 《Canadian Metallurgical Quarterly》1997,113(5):942-948
Augmentation of antioxidant defenses may help protect tissues against ischemia-reperfusion injury associated with operations involving cardiopulmonary bypass. In this study we examined the effect of pretreating patients with alpha-tocopherol (vitamin E) and ascorbic acid (vitamin C) or placebo on injury to the myocardium. Seventy-six subjects undergoing elective coronary artery bypass grafting participated in a prospective, double-blind, placebo-controlled randomized trial, receiving either placebo or both 750 IU dl-alpha-tocopherol per day for 7 to 10 days and 1 gm ascorbic acid 12 hours before the operation. Plasma alpha-tocopherol concentrations, raised fourfold by supplementation, fell by 70% after the operation in the supplemented group and to negligible levels in the placebo group. There were no significant differences between the groups with respect to release of creatine kinase MB isoenzyme over 72 hours, nor in the reduction of the myocardial perfusion defect determined by thallium 201 uptake. Electrocardiography provided no evidence of a benefit from antioxidant supplementation. Thus the supplementation regimen prevented the depletion of the primary lipid soluble antioxidant in plasma, but provided no measurable reduction in myocardial injury after the operation. 相似文献
4.
AD Santin PL Hermonat JC Hiserodt J Fruehauf V Schranz D Barclay S Pecorelli GP Parham 《Canadian Metallurgical Quarterly》1997,64(3):477-480
Tumor cells from eight freshly isolated cervical cancers (i.e., four adenocarcinomas and four squamous carcinomas) were analyzed for their production of the immune-inhibitory cytokine transforming growth factor-beta (TGF-beta) in vitro. All fresh adenocarcinomas secreted significant levels of TGF-beta (mean 397, range between 207 and 782 pg/ml/10(5) cells/48 hr). In contrast, no detectable TGF-beta was present in the supernatants from the four fresh squamous carcinoma cultures (P < 0.001). These data suggest that major differences in the secretion of the immunoinhibitory cytokine TGF-beta exist between squamous cell carcinomas and adenocarcinomas of the uterine cervix. Furthermore, these findings suggest that at least some of the differences in the natural biologic behavior, as well as in the response to radiation treatment, between these two histologic types of cervical cancer could be related to differences in secretion of this immune-inhibitory cytokine. 相似文献
5.
6.
In this study the authors have examined the effects of transluminal angioplasty on cerebral blood flow (CBF) in the management of intractable vasospasm following aneurysmal subarachnoid hemorrhage (SAH). Fourteen consecutively enrolled patients underwent attempted angioplasty with or without intraarterial infusion of papaverine. Twelve patients underwent pre- and postangioplasty xenon-enhanced computerized tomography (Xe-CT) scanning to measure regional CBF in 55 to 65 regions of interest (ROIs) per patient. Angioplasty was possible in 13 (93%) of 14 patients, with angiographically demonstrated improvement in all 13. Twelve (92%) of the 13 patients were neurologically improved following angioplasty; seven (58%) of the 12 patients who improved had a complete reversal of all delayed ischemic deficits. Angioplasty significantly decreased the mean number of ROIs at risk (11.4 ROIs pre- and 0.9 ROIs postangioplasty) (p < 0.00005, t-test). All patients had a reduction in the number of ROIs at risk after angioplasty; six (50%) of 12 no longer had any ROIs remaining at risk after angioplasty. Angioplasty significantly increased the mean CBF within at-risk ROIs (13 ml/100 g/minute pre- and 44 ml/100 g/minute postangioplasty) (p < 0.00005, t-test). All patients experienced an improvement in mean CBF in at-risk ROIs after angioplasty, with the mean CBF improving to above 20 ml/100 g/minute in all cases. No differences in the degree of improvement were found in patients who received intraarterial papaverine compared with those who did not. In the majority of patients with refractory vasospasm following SAH, angioplasty effectively dilated spastic arteries, reversed delayed neurological deficits, and significantly improved CBF in areas of brain at risk of infarction. 相似文献
7.
SC Langley GW Rickett A Hunt FJ Kelly AD Postle DA York 《Canadian Metallurgical Quarterly》1993,45(3):543-551
The biochemical maturation of the lung in late gestation and in the young animal is regulated by glucocorticoids. The present study was aimed at dissociating the different glucocorticoid receptor sites involved in these regulatory functions. The obese Zucker rat was selected as a model for this study as it exhibits hypersensitivity to glucocorticoid hormone action by virtue of its elevated receptor numbers and activity. Two synthetic steroid analogues were administered to obese animals; RU28362, a specific type II receptor agonist, and the type II antagonist RU486. RU28362 promoted a strong catabolic effect, which was associated with reduced food intake and the abolition of growth in the rats. The agonist, RU28362, attenuated developmental increases in antioxidant enzyme activities, and altered the growth of the tissue. At the age studied, development of the lung phosphatidylcholine (PC) system was almost complete, but RU28362 increased disaturated PC 16:0/16:0 concentrations by almost 2-fold, and altered the molecular composition of total pulmonary PC. RU486 attenuated the growth of the rats and reduced their food intake. Treatment with the type II antagonist attenuated lung growth and increased the activities of pulmonary copper zinc (Cu/Zn) and manganese (Mn) superoxide dismutases. RU486 had no effect on lung PC concentrations and molecular composition. The data suggest a role for type I glucocorticoid receptors in the regulation of the antioxidant enzyme system in the lung, as type II antagonism will channel endogenous glucocorticoid binding to the type I site. Type II receptor binding would appear to play a role in regulating the lung PC content. 相似文献
8.
9.
台北101层国际金融中心之结构施工技术与其设计考量概述 总被引:1,自引:0,他引:1
本文旨在简要说明目前正在施工中之超高层大楼—台北国际金融中心之结构系统、钢结构工程、钢筋混凝土工程基础与深开挖工程等特殊施工技术,并佐以相关之设计考量与施工规划概要,以供工程界做参考。 相似文献
10.
D. A. Morgan D. B. Shaw M. J. Sidebottom T. C. Soon R. S. Taylor 《Journal of the American Oil Chemists' Society》1985,62(2):292-299
The results presented in the literature, which attempt to elucidate the mechanisms by which triglyceride oils are bleached
by earths, are reviewed. The impact of this work and how the mechanistic proposals affect changes in oil properties are considered,
with particular emphasis on the needs of the palm oil processor. Important properties include color, metals and phosphorus
content and oxidative stability of the oil.
Investigations made in our own laboratories have been aimed at elucidating the effect of varying physical and chemical properties
of the bleaching earth on the quality of bleached and deodorized oils. Techniques used in this work are pore-size distribution,
surface area, scanning and transmission electron microscopy and a variety of chemical and X-ray analysis methods.
The ability to vary such parameters in montmorillonite clays by alteration of process conditions to give materials with specific
performance characteristics is demonstrated.
Comparisons are made between acid-activated montmorillonites and other clay types. 相似文献