全文获取类型
收费全文 | 9083篇 |
免费 | 1336篇 |
国内免费 | 749篇 |
专业分类
电工技术 | 448篇 |
综合类 | 1042篇 |
化学工业 | 97篇 |
金属工艺 | 71篇 |
机械仪表 | 486篇 |
建筑科学 | 105篇 |
矿业工程 | 117篇 |
能源动力 | 30篇 |
轻工业 | 92篇 |
水利工程 | 109篇 |
石油天然气 | 67篇 |
武器工业 | 65篇 |
无线电 | 3891篇 |
一般工业技术 | 375篇 |
冶金工业 | 122篇 |
原子能技术 | 22篇 |
自动化技术 | 4029篇 |
出版年
2024年 | 8篇 |
2023年 | 56篇 |
2022年 | 118篇 |
2021年 | 145篇 |
2020年 | 178篇 |
2019年 | 145篇 |
2018年 | 156篇 |
2017年 | 233篇 |
2016年 | 289篇 |
2015年 | 380篇 |
2014年 | 566篇 |
2013年 | 549篇 |
2012年 | 715篇 |
2011年 | 772篇 |
2010年 | 666篇 |
2009年 | 624篇 |
2008年 | 701篇 |
2007年 | 700篇 |
2006年 | 688篇 |
2005年 | 606篇 |
2004年 | 490篇 |
2003年 | 436篇 |
2002年 | 413篇 |
2001年 | 303篇 |
2000年 | 250篇 |
1999年 | 199篇 |
1998年 | 170篇 |
1997年 | 160篇 |
1996年 | 87篇 |
1995年 | 108篇 |
1994年 | 54篇 |
1993年 | 53篇 |
1992年 | 28篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 16篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1965年 | 2篇 |
1963年 | 3篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Noise feedback coding(NFC) has attracted renewed interest with the recent standardization of backward-compatible enhancements for ITU-T G.711 and G.722.It has also been revisited with the emergence of proprietary speech codecs,such as BV16,BV32,and SILK,that have structures different from CELP coding.In this article,we review NFC and describe a novel coding technique that optimally shapes coding noise in embedded pulse-code modulation(PCM) and embedded adaptive differential PCM(ADPCM).We describe how this new technique was incorporated into the recent ITU-T G.711.1,G.711 App.III,and G.722 Annex B(G.722B) speech-coding standards. 相似文献
82.
83.
Visual domain adaptation has attracted much attention and has made great achievement in recent years. It deals with the problem of distribution divergence between source and target domains. Current methods mostly focus on transforming images from different domains into a common space to minimize the distribution divergence. However, there are many irrelevant source samples for target domain even after the transformation. In order to eliminate the irrelevant samples, we develop a sample selection algorithm using sparse coding theory. We do the sample selection in a common subspace of source and target data to find as many as relevant source samples. In the common subspace, data characteristics are preserved by using graph regularization. Therefore, we can select the most relevant samples for our target image classification task. Moreover, in order to build a discriminative classifier for the target domain, we use not only the common part of source and target domains learned in the common subspace but also the specific part of target domain. The algorithm can be extended to handle samples from multiple source domains. Experimental results show that our visual domain adaptation method on the image classification tasks can be very effective for the state-of-the-art datasets. 相似文献
84.
The three-dimensional discrete cosine transform (3D-DCT) has been researched as an alternative to existing dominant video standards based on motion estimation and compensation. Since it does not need to search macro block for inter/intra prediction, 3D-DCT has great advantages for complexity. However, it has not been developed well because of poor video quality while video standards such as H.263(+) and HEVC have been blooming. In this paper, we propose a new 3D-DCT video coding as a new video solution for low power mobile technologies such as Internet of Things (IoT) and Drone. We focus on overcoming drawbacks reported in previous research. We build a complete 3D-DCT video coding system by adopting existing advanced techniques and devising new coding algorithms to improve overall performance of 3D-DCT. Experimental results show proposed 3D-DCT outperforms H.264 low power profiles while offering less complexity. From GBD-PSNR, proposed 3D-DCT provides better performance by average 4.6 dB. 相似文献
85.
针对H.264视频压缩编码标准中去块效应滤波器部分提出了一种基于YHFT Matrix DSP的并行设计及向量实现方法。重点对H.264协议中去块效应滤波器进行理论分析,并利用向量数据访问单元、向量处理单元、高效的混洗单元和灵活的矩阵对其进行并行算法设计。将去块滤波算法分别映射到YHFT Matrix和TI的TMS320C6415中,通过统计两者性能,表明YHFT Matrix的性能优于TMS320C6415。 相似文献
86.
《Planning》2014,(5)
本文设计了一种多用途串口转换器,主要实现了以下功能:USB-RS232-TTL自动切换功能、RS232的收发自动切换功能及其热插拔功能、TTL的RXD-TXD收发自动切换功能及供电电源的正负极自动切换功能。该转换器实现了这三种常用接口的自动切换,为调试电路提供了方便。 相似文献
87.
《Drug development and industrial pharmacy》2013,39(12):1503-1510
Background: Oral absorption of low-molecular-weight heparin (LMWH) is limited by its molecular size and negative charge. It has been shown previously that orally administered polymeric nano- or microparticles containing encapsulated LMWH have led to gastrointestinal absorption of heparin in rabbits. Method: Based on these investigations, pellets containing two LMWHs, enoxaparin (MW 4500 Da) or bemiparin (MW 3600 Da), and Eudragit®RS30D (ERS), were prepared using extrusion/ spheronization technique. Uncoated or coated (ERS) pellets were evaluated in vitro and in vivo on rabbits. Results: Enoxaparin pellets showed fast in vitro release in phosphate buffer (pH 7.4) and prolonged in vivo drug absorption after a single oral dose of 600 anti-Xa IU/ kg of body weight, leading to relative bioavailabilities ranging from 9.7 ± 1.9% to 12.8 ± 2.7% and anti-Xa activity over the curative dose. Bemiparin included in matrix pellets of ERS and coated with ERS exhibited in vitro prolonged release up to 4 hours and in vivo anti-Xa activity below the therapeutic minimum value of 0.1 IU/mL. Conclusion: This study presents LMWH in a pellet dosage form, which compared to nano- or microparticles, may offer a more convenient and industrializable way of manufacture leading to an easier scale-up process. 相似文献
88.
《Drug development and industrial pharmacy》2013,39(2):179-189
The objective of this work was to formulate new oral insulin-loaded nanoparticules using the response surface methodology. The insulin nanoparticles were prepared by a water-in-oil-in-water emulsification and evaporation method. The polymers used for the encapsulation were blends of biodegradable poly-epsilon-caprolactone (PCL) and of positively-charged, nonbiodegradable polymer (Eudragis RS®). A central composite design has been built to investigate the effects of three controlled variables: ratio of polymers (PCL/RS ratio), volume, and pH of the aqueous solution of polyvinyl alcohol. The nanoparticles were characterized by measuring the amount of entrapped insulin, the particle size, the polydispersity of the obtained particles, the zeta potential, and the amount of insulin released after 7 hours. A second-order model was evaluated by multiple regression and was statistically tested for each of the studied controlled variable. The obtained polynomials proved efficient to localize an optimal operating area highlighted by the use of three-dimensional response surfaces and their corresponding isoresponse curves. An interesting formulation given by the models was selected, prepared, and evaluated. The corresponding quantity of entrapped insulin was 25 IU per 100 mg of polymer, and the particle size was 350 nm with a polydispersity of 0.21. The quantity of released insulin was 4.8 IU per 100 mg of polymer after 7 hours and the zeta potential was + 44 mV. All these collected values were in perfect accordance with values estimated by the models. Finally, the results suggested that PCL/RS 50/50 nanoparticles might represent a promising formulation for oral delivery of insulin. 相似文献
89.
90.
交织器是Turbo信道编码的重要组成部分,交织器的扩展因子通常是衡量一个交织器好坏的量度。阐述了基于整数环的QPP(quadraticpermutationpolynomials)交织器可以产生最大扩展因子,从代数几何视角研究了交织器的修正了的非线性度性质,提出了一种交织器的新的量度,这个量度是扩展因子和非线性度的函数。通过计算机仿真表明,由这种新的量度选择的交织器在误码率上表现出较优性能。 相似文献