全文获取类型
收费全文 | 456533篇 |
免费 | 38332篇 |
国内免费 | 21867篇 |
专业分类
电工技术 | 29251篇 |
技术理论 | 74篇 |
综合类 | 54696篇 |
化学工业 | 53654篇 |
金属工艺 | 18680篇 |
机械仪表 | 24934篇 |
建筑科学 | 63066篇 |
矿业工程 | 25627篇 |
能源动力 | 15437篇 |
轻工业 | 29609篇 |
水利工程 | 22300篇 |
石油天然气 | 21842篇 |
武器工业 | 5298篇 |
无线电 | 30020篇 |
一般工业技术 | 34098篇 |
冶金工业 | 25269篇 |
原子能技术 | 4155篇 |
自动化技术 | 58722篇 |
出版年
2024年 | 1744篇 |
2023年 | 5194篇 |
2022年 | 9921篇 |
2021年 | 12469篇 |
2020年 | 12627篇 |
2019年 | 9898篇 |
2018年 | 9491篇 |
2017年 | 11825篇 |
2016年 | 14015篇 |
2015年 | 15365篇 |
2014年 | 28110篇 |
2013年 | 25236篇 |
2012年 | 31425篇 |
2011年 | 33963篇 |
2010年 | 26050篇 |
2009年 | 26789篇 |
2008年 | 24881篇 |
2007年 | 31465篇 |
2006年 | 29317篇 |
2005年 | 25680篇 |
2004年 | 21647篇 |
2003年 | 19249篇 |
2002年 | 15766篇 |
2001年 | 13228篇 |
2000年 | 11222篇 |
1999年 | 8979篇 |
1998年 | 6708篇 |
1997年 | 5875篇 |
1996年 | 5146篇 |
1995年 | 4356篇 |
1994年 | 3806篇 |
1993年 | 2829篇 |
1992年 | 2433篇 |
1991年 | 1775篇 |
1990年 | 1547篇 |
1989年 | 1387篇 |
1988年 | 1013篇 |
1987年 | 715篇 |
1986年 | 552篇 |
1985年 | 511篇 |
1984年 | 441篇 |
1983年 | 341篇 |
1982年 | 279篇 |
1981年 | 223篇 |
1980年 | 191篇 |
1979年 | 139篇 |
1978年 | 80篇 |
1977年 | 89篇 |
1976年 | 64篇 |
1975年 | 69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.
Yasoub Eghbali Mahmoud Ferdosizade Naeiny 《International Journal of Communication Systems》2020,33(14)
In this paper, an off‐grid direction of arrival (DoA) estimation method is proposed for wideband signals. This method is based on the sparse representation (SR) of the array covariance matrix. Similar to the time domain DoA estimation methods, the correlation function of the sources was assumed to be the same and known. A new measurement vector is obtained using the lower‐left triangular elements of the covariance matrix. The DoAs are estimated by quantizing the entire range of continuous angle space into discrete grid points. However, the exact DoAs may be located between two grid points; therefore, this estimation has errors. The accuracy of DoA estimation is improved by the minimization of the difference between the new measurement vector and its estimated values. Simulation results revealed that the proposed method can enhance the DoA estimation accuracy of wideband signals. 相似文献
3.
4.
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
5.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献
6.
7.
《低温学》2015
The development of a high cooling power and high efficiency 4.2 K two stage G-M cryocooler is critically important given its broad applications in low temperature superconductors, MRI, infrared detector and cryogenic electronics. A high efficiency 1.5 W/4.2 K pneumatic-drive G-M cryocooler has recently been designed and developed by ARS. The effect of expansion volume rate and operation conditions on the cooling performance has been experimentally investigated. A typical cooling performance of 1.5 W/4.2 K has been achieved, and the minimum temperature of the second stage is 2.46 K. The steady input power of the compressor at 60 Hz is 6.8 kW, while the operation speed of the rotary valve is 30 rpm. A maximum cooling power of 1.75 W/4.2 K has been obtained in test runs. 相似文献
8.
9.
10.
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