全文获取类型
收费全文 | 576182篇 |
免费 | 51734篇 |
国内免费 | 26828篇 |
专业分类
电工技术 | 35057篇 |
技术理论 | 90篇 |
综合类 | 63589篇 |
化学工业 | 75529篇 |
金属工艺 | 26412篇 |
机械仪表 | 30865篇 |
建筑科学 | 76529篇 |
矿业工程 | 33272篇 |
能源动力 | 19040篇 |
轻工业 | 42355篇 |
水利工程 | 25930篇 |
石油天然气 | 30759篇 |
武器工业 | 6116篇 |
无线电 | 37314篇 |
一般工业技术 | 44247篇 |
冶金工业 | 35083篇 |
原子能技术 | 5187篇 |
自动化技术 | 67370篇 |
出版年
2024年 | 2345篇 |
2023年 | 7178篇 |
2022年 | 15304篇 |
2021年 | 18316篇 |
2020年 | 16836篇 |
2019年 | 13226篇 |
2018年 | 12867篇 |
2017年 | 16029篇 |
2016年 | 19512篇 |
2015年 | 21362篇 |
2014年 | 36390篇 |
2013年 | 32729篇 |
2012年 | 38914篇 |
2011年 | 41430篇 |
2010年 | 32318篇 |
2009年 | 32866篇 |
2008年 | 30135篇 |
2007年 | 38793篇 |
2006年 | 36671篇 |
2005年 | 32023篇 |
2004年 | 26748篇 |
2003年 | 23914篇 |
2002年 | 19403篇 |
2001年 | 16271篇 |
2000年 | 13769篇 |
1999年 | 10822篇 |
1998年 | 8013篇 |
1997年 | 6920篇 |
1996年 | 6038篇 |
1995年 | 5043篇 |
1994年 | 4417篇 |
1993年 | 3212篇 |
1992年 | 2778篇 |
1991年 | 2026篇 |
1990年 | 1807篇 |
1989年 | 1581篇 |
1988年 | 1163篇 |
1987年 | 822篇 |
1986年 | 650篇 |
1985年 | 602篇 |
1984年 | 542篇 |
1983年 | 397篇 |
1982年 | 325篇 |
1981年 | 271篇 |
1980年 | 260篇 |
1979年 | 163篇 |
1977年 | 102篇 |
1964年 | 97篇 |
1962年 | 109篇 |
1959年 | 106篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
2.
3.
本文以云杉八齿小蠹Ips typographus Linnaeus为例,经标本选取,观察虫体整体形态,绘制整体结构草图,电子显微镜观察局部、得到局部数字图像,分别建立虫体每一部分的高精度细节。把模型每部分拼装在一起组成整体模型,构建出了云杉八齿小蠹三维虚拟昆虫数字化模型。 相似文献
4.
In architectural design, surface shapes are commonly subject to geometric constraints imposed by material, fabrication or assembly. Rationalization algorithms can convert a freeform design into a form feasible for production, but often require design modifications that might not comply with the design intent. In addition, they only offer limited support for exploring alternative feasible shapes, due to the high complexity of the optimization algorithm.We address these shortcomings and present a computational framework for interactive shape exploration of discrete geometric structures in the context of freeform architectural design. Our method is formulated as a mesh optimization subject to shape constraints. Our formulation can enforce soft constraints and hard constraints at the same time, and handles equality constraints and inequality constraints in a unified way. We propose a novel numerical solver that splits the optimization into a sequence of simple subproblems that can be solved efficiently and accurately.Based on this algorithm, we develop a system that allows the user to explore designs satisfying geometric constraints. Our system offers full control over the exploration process, by providing direct access to the specification of the design space. At the same time, the complexity of the underlying optimization is hidden from the user, who communicates with the system through intuitive interfaces. 相似文献
5.
6.
7.
The heat transfer and flow characteristics of MWCNT-R141b nanorefrigerant with different mass fractions have been studied through experiments. Experimental results were compared with existing correlations. A two-step method was used to prepare the nanorefrigerants. Span-80 was used as surfactant with an average particle diameter of 20 nm. Transmittance method was used to evaluate the stability of nanorefrigerants. Results showed that the stability of MWCNT-R141b nanorefrigerant, which is the added dispersant, was good during the experiments. The 0.3 wt% MWCNT-R141b nanorefrigerants had optimal heat transfer enhancement effects compared with pure refrigerants. The maximum Nusselt number increased by 40%. The specific pressure drop of nanorefrigerant increased as the Reynolds number (Re) increased, and the specific pressure drop of the pure refrigerant was minimum, which is similar to R141b. 相似文献
8.
9.
A small handful of recent studies have addressed a phenomenon known as “phantom vibration syndrome”. This refers to when phone users perceive their device to vibrate, indicating that a call or text is incoming, when in fact the phone did not vibrate at all. Though these studies show that most users do not find phantom vibration hallucinations to be very bothersome, they also find that a large majority of users experience this phenomenon. This paper explores what the striking prevalence of phantom vibration syndrome means for our contemporary relationships with technology. I begin with a review of the theories purporting to explain these data, which largely rely on particular understandings of the brain. Next I develop an alternative theory of phantom vibration syndrome based on insights from the philosophical tradition of phenomenology. This account considers the ways users develop bodily and perceptual habits regarding how the phone is understood and used. By critically contrasting these different theories, we can refine our questions about what the high prevalence of phantom vibration syndrome implies about our contemporary technological situation. 相似文献
10.
《Food Control》2015
The aim of the study was to investigate annual and regional differences in the level of aflatoxin B1 (AFB1) in grains and dairy cattle feed. Maize (n = 972), wheat (n = 201), barley (n = 147), oat (n = 136), grain mixtures (n = 168), and dairy cattle feed (n = 325) were sampled from 2009 to 2013 on different farms and in different farm factories situated in four Croatian regions. The samples were analysed for AFB1 using the validated ELISA immunoassay. AFB1 was determined in 16.4% of all investigated samples, among which maize was proven to be the most contaminated, with 21.7% of the samples recovered during 2013 harbouring AFB1 in concentrations over the permissible ones. Levels higher than permitted were observed in 17.9% and 12.3% of grain mixtures and dairy cattle feed, respectively, whereas concentrations of AFB1 determined in other crops throughout the investigated period met the stipulated requirements. The results revealed the AFB1 occurrence to be significantly (p < 0.05) dependent on the cultivation region, with the highest levels generally found in maize harvested in 2013 and consequently in grain mixtures and cattle feed that can most likely be associated with climatic conditions as the most critical factor for mould formation, and thus also AFB1 production. 相似文献