全文获取类型
收费全文 | 4552篇 |
免费 | 58篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 47篇 |
化学工业 | 395篇 |
金属工艺 | 70篇 |
机械仪表 | 57篇 |
建筑科学 | 124篇 |
矿业工程 | 15篇 |
能源动力 | 42篇 |
轻工业 | 294篇 |
水利工程 | 29篇 |
石油天然气 | 7篇 |
无线电 | 294篇 |
一般工业技术 | 451篇 |
冶金工业 | 2373篇 |
原子能技术 | 19篇 |
自动化技术 | 397篇 |
出版年
2021年 | 29篇 |
2019年 | 22篇 |
2018年 | 25篇 |
2017年 | 34篇 |
2016年 | 17篇 |
2015年 | 32篇 |
2014年 | 58篇 |
2013年 | 150篇 |
2012年 | 103篇 |
2011年 | 103篇 |
2010年 | 56篇 |
2009年 | 61篇 |
2008年 | 89篇 |
2007年 | 107篇 |
2006年 | 104篇 |
2005年 | 72篇 |
2004年 | 79篇 |
2003年 | 86篇 |
2002年 | 74篇 |
2001年 | 57篇 |
2000年 | 54篇 |
1999年 | 120篇 |
1998年 | 704篇 |
1997年 | 417篇 |
1996年 | 276篇 |
1995年 | 155篇 |
1994年 | 136篇 |
1993年 | 163篇 |
1992年 | 63篇 |
1991年 | 69篇 |
1990年 | 60篇 |
1989年 | 70篇 |
1988年 | 77篇 |
1987年 | 51篇 |
1986年 | 61篇 |
1985年 | 64篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 26篇 |
1981年 | 48篇 |
1980年 | 44篇 |
1979年 | 27篇 |
1978年 | 29篇 |
1977年 | 85篇 |
1976年 | 119篇 |
1975年 | 31篇 |
1974年 | 23篇 |
1973年 | 28篇 |
1972年 | 19篇 |
1971年 | 18篇 |
排序方式: 共有4614条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
JM Rumsey BC Donohue DR Brady K Nace JN Giedd P Andreason 《Canadian Metallurgical Quarterly》1997,54(12):1481-1489
The influence of ionic strength and composition on the binding and inhibition of human leukocyte elastase by glycosaminoglycans with variable degree and position of sulfation was investigated. The kinetic mechanism of inhibition had a hyperbolic, mixed-type character with a competitive component that was promoted by low ionic strength, reduced by phosphate ions, and which also depended on the substrate and glycosaminoglycan structure. Enzyme binding was a cooperative phenomenon that varied with ionic strength and composition. The inhibition patterns correlated with the cationic character of elastase and with the distribution of arginines on its molecular surface, most notably with residues located in the vicinity of the substrate binding region. The order of affinity for elastase binding was chondroitin 4-sulfate < chondroitin 6-sulfate < dermatan sulfate, iduronate-containing derivatives being superior with respect to the glucuronate-containing counterparts. Additional sulfation at both the 4- and 6- positions or at the N- and 4-positions of the N-acetylgalactosamine moiety decidedly improved the inhibitory efficiency. The results highlight a fundamental physiological role of enzyme-glycosaminoglycan interactions. In the azurophil granule of the human polymorphonuclear neutrophil, elastase and other enzymes are bound to a matrix of chondroitin 4-sulfate because this is the only glycosaminoglycan that simultaneously offers good binding for enzyme compartmentalization together with prompt release from the bound state at the onset of phagocytosis. 相似文献
5.
6.
WR Volger RS Weiner JO Moore GA Omura AA Bartolucci M Stagg 《Canadian Metallurgical Quarterly》1995,9(9):1456-1460
A phase III clinical trial was designed to determine if more intensive induction and consolidation therapy for acute myeloblastic leukemia increases the remission rate and prolongs survival. A minor objective was to determine if the use of non-cross resistant drugs was more effective than the same drugs used for induction. Patients with untreated leukemia between the ages of 15 and 50 were given daunorubicin 45 mg/m2 for the first 3 days of a 10-day continuous infusion of cytosine arabinoside, initially at a dose of 2000 mg/m2 but reduced to 100 mg/m2 because of toxicity. Those under 36 achieving a complete remission and with an histocompatible donor were assigned to a transplant arm. The rest were randomized to receive one of three consolidation arms: A, cytosine arabinoside, 200 mg/m2 daily for 7 days and daunorubicin 45 mg/m2 daily for 3 days for three courses; B, one course as in Arm A followed by amsacrine, 120 mg/m2 daily for 5 days followed by a 5-day continuous infusion of azacytidine, 150 mg/m2/day; C, thioguanine and cytosine arabinoside, 100 mg/m2 every 12 h and daunorubicin 10 mg/m2 daily for 5 days for three courses followed by four maintenance courses of cytosine arabinoside, 100 mg/m2 daily for 5 days and daunorubicin, 45 mg/m2 for 2 days every 13 weeks. From 1981 to 1986, 398 eligible patients were enrolled and 219 achieved a complete remission. The initial induction dose of cytosine arabinoside was reduced after five of 29 patients exhibited fatal gastrointestinal toxicity. Only 11 patients were assigned to the transplant arm. There were no significant differences in the consolidation arms. The 5 year disease-free survivals were 38, 31 and 27% in arms A, B, and C respectively. Intensive consolidation therapy with the same or different drugs used in induction was as effective as lower dose consolidation followed by maintenance therapy. 相似文献
7.
8.
Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples. 相似文献
9.
Knowledge elicitation is accepted as being one of the most problematic areas in the creation of a knowledge-based system.A large amount of research has already concentrated on finding more efficient and effective techniques for eliciting knowledge from an individual expert. However, little attention has been given to the involvement of more than one source of expertise in knowledge-based system development.This paper is based on the authors' practical experience gained when developing a knowledge-based system for the conceptual design of bridges. It shows that the use of more than one expert throughout the knowledge elicitation process can improve both the efficiency of the approach and the quality of the knowledge acquired. 相似文献
10.
JN Vauthey RJ Tomczak T Helmberger P Gertsch C Forsmark J Caridi A Reed MR Langham GY Lauwers P Goffette J Lerut 《Canadian Metallurgical Quarterly》1997,113(4):1390-1401
BACKGROUND & AIMS: Arterioportal fistulas (APFs) are rare vascular disorders of the mesenteric circulation. The aim of this study was to determine the etiology, anatomical location, and main symptom at presentation of APFs, and analyze the various modes of treatment. METHODS: The etiology, clinical presentation, radiographs, and treatment of 12 patients with APFs are reported in detail, and another 76 cases published since 1980 are reviewed. RESULTS: APFs result from trauma (n = 25, 28%), iatrogenic procedures (n = 14, 16%), congenital vascular malformations (n = 13, 15%), tumor (n = 13, 15%), aneurysm (n = 12, 14%), and other causes (n = 11, 12%). The origin of APFs is the hepatic artery in the majority of patients (n = 56, 65%). The main symptoms at presentation are lower or upper gastrointestinal bleeding (n = 29, 33%), ascites (n = 23, 26%), heart failure (n = 4.5%), or diarrhea (n = 4.5%). Radiological intervention provides definitive treatment in 42% (n = 33) of patients, whereas the remainder are treated by surgery alone (n = 27, 31%) or a combination of radiological intervention and surgery (n = 8, 9%). CONCLUSIONS: APFs result in a protean syndrome variously combining portal hypertension and other hemodynamic imbalances (heart failure, intestinal ischemia). Single or multiple interventional radiological procedures using arterial and/or venous approaches allow definitive treatment of most APFs. With increasing technological advances, it is anticipated that surgery will only be indicated in rare instances after failure of radiological intervention(s). 相似文献