全文获取类型
收费全文 | 4889篇 |
免费 | 341篇 |
国内免费 | 169篇 |
专业分类
电工技术 | 194篇 |
综合类 | 252篇 |
化学工业 | 754篇 |
金属工艺 | 223篇 |
机械仪表 | 212篇 |
建筑科学 | 335篇 |
矿业工程 | 128篇 |
能源动力 | 113篇 |
轻工业 | 249篇 |
水利工程 | 86篇 |
石油天然气 | 149篇 |
武器工业 | 46篇 |
无线电 | 685篇 |
一般工业技术 | 705篇 |
冶金工业 | 615篇 |
原子能技术 | 51篇 |
自动化技术 | 602篇 |
出版年
2024年 | 20篇 |
2023年 | 73篇 |
2022年 | 146篇 |
2021年 | 199篇 |
2020年 | 111篇 |
2019年 | 123篇 |
2018年 | 143篇 |
2017年 | 148篇 |
2016年 | 117篇 |
2015年 | 180篇 |
2014年 | 183篇 |
2013年 | 228篇 |
2012年 | 242篇 |
2011年 | 294篇 |
2010年 | 258篇 |
2009年 | 246篇 |
2008年 | 289篇 |
2007年 | 220篇 |
2006年 | 199篇 |
2005年 | 155篇 |
2004年 | 105篇 |
2003年 | 105篇 |
2002年 | 99篇 |
2001年 | 111篇 |
2000年 | 123篇 |
1999年 | 136篇 |
1998年 | 234篇 |
1997年 | 157篇 |
1996年 | 111篇 |
1995年 | 72篇 |
1994年 | 68篇 |
1993年 | 65篇 |
1992年 | 34篇 |
1991年 | 29篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 28篇 |
1985年 | 14篇 |
1984年 | 27篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 34篇 |
1956年 | 8篇 |
排序方式: 共有5399条查询结果,搜索用时 15 毫秒
51.
Dora Szabo Zsolt Sarszegi Beata Polgar Eva Saghy Adam Nemeth Dora Reglodi Andras Makkos Aniko Gorbe Zsuzsanna Helyes Peter Ferdinandy Robert Herczeg Attila Gyenesei Attila Cziraki Andrea Tamas 《International journal of molecular sciences》2021,22(6)
Acute myocardial infarction (MI) is one of the most common causes of death worldwide. Pituitary adenylate cyclase activating polypeptide (PACAP) is a cardioprotective neuropeptide expressing its receptors in the cardiovascular system. The aim of our study was to examine tissue PACAP-38 in a translational porcine MI model and plasma PACAP-38 levels in patients with ST-segment elevation myocardial infarction (STEMI). Significantly lower PACAP-38 levels were detected in the non-ischemic region of the left ventricle (LV) in MI heart compared to the ischemic region of MI-LV and also to the Sham-operated LV in porcine MI model. In STEMI patients, plasma PACAP-38 level was significantly higher before percutaneous coronary intervention (PCI) compared to controls, and decreased after PCI. Significant negative correlation was found between plasma PACAP-38 and troponin levels. Furthermore, a significant effect was revealed between plasma PACAP-38, hypertension and HbA1c levels. This was the first study showing significant changes in cardiac tissue PACAP levels in a porcine MI model and plasma PACAP levels in STEMI patients. These results suggest that PACAP, due to its cardioprotective effects, may play a regulatory role in MI and could be a potential biomarker or drug target in MI. 相似文献
52.
危浪 《湖南工业职业技术学院学报》2021,21(6):98-101,127
职业教育进入提质培优新阶段,以深化产教融合助推职业教育高质量发展,是落实科教兴国战略和人才强国战略的必修课.基于对产教融合生态系统的内涵和困境分析,运用系统基模解构职业院校产教融合生态的运行机制,并提出相应的管理策略,对深化职业教育产教融合具有重要指导意义. 相似文献
53.
54.
L. H. Lang D. C. Kang S. H. Zhang Z. R. Wang S. J. Yuan K. B. Nielsen J. Dancket ) Department of Materials Engineering Harbin Institute of Technology Harbin China ) Aalberg University Denmark 《金属学报(英文版)》2000,13(2):476-480
1.~nonHydridapawhcdeepdrawing(HDD)belongstothefieldofsheetmetalfoeingandcanbeaPPliedinthefieldofautomotive,aerospace,drilitaryindustryetc.Ithasbeenrecognizedwidelyintheworld["'j.Fig.Ishowsitsprinciple:TheliqUidthatisfilledinthe~ngdiecavitywillbepressedwhenthepunchgoesdownsothattheeffectoffrictionkeepingandoverflowlubricatingcanbeformed,astherestilt,thefoeinglicitofsheetmetalwillbeimprovedareailvandthegualitVofthefinishedpartswillbeup~ed.BecauseofmanyadvantagesofHDDprocees,ithasbeenwidelys… 相似文献
55.
微量稀土和硼在铜及其合金中的作用 总被引:28,自引:6,他引:28
介绍了近年来微量稀土和硼在其合金中的应用,稀土在铜和铜合金中去除杂质,净化晶界,细化组织,消除柱状晶的作用,从而改善铜和铜合金的导电性,力学性能,冷热加工性能和耐磨性性能,硼在铜和铜合金中有比稀土更显著的细化晶粒作用。 相似文献
56.
57.
Mucsi Zoltan; Gaspari Zoltan; Orosz Gyorgy; Perczel Andras 《Protein engineering, design & selection : PEDS》2003,16(9):673-681
Three peptides modelling a highly potent, 35-residue chymotrypsininhibitor (Schistocerca gregaria chymotrypsin inhibitor) weredesigned and synthesized by convergent peptide synthesis. Foreach model peptide, the inhibitory constant (Ki) on chymotrypsinand the solution structure were determined. In addition, moleculardynamics calculations were performed for all of them. Two modelscontaining approximately half of the parent inhibitor (17 of35 residues) were designed and subsequently found to have nosubstantial inhibitory activity (Ki values in the mM range).The third model composed of 24 amino acid residues proved tobe an effective (Ki 107) inhibitor of bovine chymotrypsin.Both the solution structure properties determined by NMR spectroscopyand the dynamic behaviour of the latter model system are comparableto the native inhibitor. In contrast, the structure and dynamicsof the first two related model peptides show characteristicdifferences. We suggest that the conformation and flexibilityof the modelled protease inhibitor are crucial for its biologicalefficiency. Moreover, the structural and dynamic features ofthe binding loop (2833) and those of the rest of themolecule appear to be interdependent. Most importantly, thesestructural characteristics can be rationally modified, at leastpartially, by peptide design. Received March 7, 2003; revised August 25, 2003; accepted August 26, 2003. 相似文献
58.
59.
60.