全文获取类型
收费全文 | 760775篇 |
免费 | 9287篇 |
国内免费 | 1854篇 |
专业分类
电工技术 | 13257篇 |
综合类 | 2869篇 |
化学工业 | 117196篇 |
金属工艺 | 32904篇 |
机械仪表 | 24683篇 |
建筑科学 | 17258篇 |
矿业工程 | 5874篇 |
能源动力 | 18537篇 |
轻工业 | 57143篇 |
水利工程 | 9692篇 |
石油天然气 | 18245篇 |
武器工业 | 52篇 |
无线电 | 81638篇 |
一般工业技术 | 155412篇 |
冶金工业 | 120214篇 |
原子能技术 | 17556篇 |
自动化技术 | 79386篇 |
出版年
2021年 | 6514篇 |
2019年 | 6203篇 |
2018年 | 24156篇 |
2017年 | 23285篇 |
2016年 | 20802篇 |
2015年 | 7708篇 |
2014年 | 12272篇 |
2013年 | 31298篇 |
2012年 | 21510篇 |
2011年 | 33601篇 |
2010年 | 27535篇 |
2009年 | 27511篇 |
2008年 | 28968篇 |
2007年 | 29449篇 |
2006年 | 19536篇 |
2005年 | 18724篇 |
2004年 | 17752篇 |
2003年 | 17419篇 |
2002年 | 16246篇 |
2001年 | 15540篇 |
2000年 | 14958篇 |
1999年 | 14659篇 |
1998年 | 34854篇 |
1997年 | 25008篇 |
1996年 | 19468篇 |
1995年 | 14824篇 |
1994年 | 13331篇 |
1993年 | 13165篇 |
1992年 | 10154篇 |
1991年 | 9871篇 |
1990年 | 9633篇 |
1989年 | 9364篇 |
1988年 | 9117篇 |
1987年 | 8146篇 |
1986年 | 7998篇 |
1985年 | 9067篇 |
1984年 | 8217篇 |
1983年 | 7904篇 |
1982年 | 7119篇 |
1981年 | 7168篇 |
1980年 | 6960篇 |
1979年 | 7082篇 |
1978年 | 6959篇 |
1977年 | 7650篇 |
1976年 | 9433篇 |
1975年 | 6252篇 |
1974年 | 5987篇 |
1973年 | 6122篇 |
1972年 | 5309篇 |
1971年 | 4952篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Zakharov A. V. Rozenko S. A. 《Journal of Communications Technology and Electronics》2019,64(4):430-438
Journal of Communications Technology and Electronics - Microstrip band-pass filters (BPFs) containing quarter-wavelength resonators and a Π-shaped half-wavelength resonator placed next to each... 相似文献
82.
Geetha R. Madhusudhan V. Padmavathy T. Lallithasree A. 《Wireless Personal Communications》2019,108(3):1957-1976
Wireless Personal Communications - The majority of security systems for wireless sensor networks are based on symmetric encryption. The main open issue for these approaches concerns the... 相似文献
83.
Journal of Computer and Systems Sciences International - The problem of constructing a guaranteeing anticipating control for a shock isolator that protects an object on a movable base from impacts... 相似文献
84.
Dreissenid mussel veligers compose a substantial component of pelagic biomass in the Great Lakes, yet their dynamics are poorly understood. To evaluate seasonal, spatial, and inter-annual variation in veliger density, we used a 64-μm mesh plankton net (2008, 2013–2016) and a 153-μm mesh plankton net (2007–2016) to collect dreissenid veligers at nearshore (15–25?m depth), transitional (45?m) and offshore (93–110?m) sites in southeast Lake Michigan during March–December. We also evaluated trends in density of recently settled mussels relative to veliger abundance and the density of the standing stock of adult mussels. Veliger density peaked during both summer and fall at all sites, but peak densities in summer were generally higher nearshore, whereas peak densities in the fall were generally higher offshore. The density of veligers in the 153-μm net was overall 28% of that in the 64-μm net, but there was high variability in this comparison among months. Smaller veligers were much more abundant in the 64-μm net, but there was little difference in the size distribution and abundance between nets for the 210–300?μm size classes. Thus, the 153-μm net could still be a useful tool for assessing density trends of larger veligers just prior to their settlement. Newly settled mussels (≤2?mm) were most abundant in summer or fall at the nearshore and offshore sites but were nearly absent at the transitional site despite the high density of veligers there. Factors other than veliger density must play an important role in mussel recruitment. 相似文献
85.
Byakova O. V. Stepanov G. V. Vlasov A. O. Danylyuk V. E. Semenov N. V. Berezovs’kyi O. M. Gnyloskurenko S. V. 《Strength of Materials》2019,51(5):726-734
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to... 相似文献
86.
Measurement Techniques - The article is devoted to the issues of conceptual development of a new generation of electrocardiogram imitators. A mathematical model is proposed for simulating ECG... 相似文献
87.
88.
89.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
90.