全文获取类型
收费全文 | 17615篇 |
免费 | 2273篇 |
国内免费 | 1286篇 |
专业分类
电工技术 | 455篇 |
综合类 | 1588篇 |
化学工业 | 2428篇 |
金属工艺 | 1950篇 |
机械仪表 | 787篇 |
建筑科学 | 2618篇 |
矿业工程 | 432篇 |
能源动力 | 595篇 |
轻工业 | 454篇 |
水利工程 | 267篇 |
石油天然气 | 284篇 |
武器工业 | 204篇 |
无线电 | 2803篇 |
一般工业技术 | 2698篇 |
冶金工业 | 602篇 |
原子能技术 | 69篇 |
自动化技术 | 2940篇 |
出版年
2024年 | 78篇 |
2023年 | 269篇 |
2022年 | 480篇 |
2021年 | 601篇 |
2020年 | 628篇 |
2019年 | 534篇 |
2018年 | 528篇 |
2017年 | 632篇 |
2016年 | 680篇 |
2015年 | 685篇 |
2014年 | 1039篇 |
2013年 | 1178篇 |
2012年 | 1166篇 |
2011年 | 1293篇 |
2010年 | 1011篇 |
2009年 | 1001篇 |
2008年 | 1081篇 |
2007年 | 1322篇 |
2006年 | 1205篇 |
2005年 | 989篇 |
2004年 | 850篇 |
2003年 | 653篇 |
2002年 | 578篇 |
2001年 | 500篇 |
2000年 | 418篇 |
1999年 | 341篇 |
1998年 | 292篇 |
1997年 | 245篇 |
1996年 | 192篇 |
1995年 | 151篇 |
1994年 | 116篇 |
1993年 | 81篇 |
1992年 | 69篇 |
1991年 | 65篇 |
1990年 | 41篇 |
1989年 | 44篇 |
1988年 | 33篇 |
1987年 | 22篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
ABSTRACTIn recent times, the applications of multimedia are rising in a greedy mode and hence the amount of video transactions is also increasing exponentially. This has shouted great demands on effective models on video encoding and also for reducing the transmission channel congestion. This research work introduces a managing technique termed weighted encoding for High-Efficiency Video Coding (HEVC). HEVC, also termed as MPEG-H Part 2 and H.265 is a video compression standard that is widely utilized AVC (H.264 or MPEG-4 Part 10). When compared to AVC, HEVC grants double the ratio of data compression at a similar level of quality of the video or considerably enhanced video quality at a similar bit rate. This work intends to optimize the weight that adopted in HEVC for encoding. For this, this paper proposes a new Iterative based propagation update in the water wave Optimization Algorithm (IPU-WWO), which is the improved form of Water wave Optimization (WWO). The performance of proposed IPU-WWO is compared over other conventional methods like Artificial Bee Colony (ABC), Firefly (FF), Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) with respect to Peak Signal to Noise Ratio (PSNR). By doing the encoding process, it minimizes the video size with perceptually better quality video or PSNR. 相似文献
3.
4.
WCDMA作为第三代移动通信系统的主流标准,能够提供多种类型的多媒体服务。为了实现各种用户平面数据的传输,系统会提前通过控制平面对所需的无线资源进行分配。由于配置过程是通过接口之间发送控制平面应用协议消息来实现的,因此能否正确有效地对信令消息进行编解码成为保证系统稳定工作的关键因素。3GPP标准中,ASN.1语言被用来描述接口信令消息。首先简要介绍了WCDMA系统结构以及主要接口协议,重点描述了ASN.1存在的意义及其编解码规则,最后给出了基于ASN.1的开发环境下应用层网络协议的开发流程。 相似文献
5.
6.
The bonding of β'-Al2O3 and pyrex glass to Al matrix composites by anodic bonding process is achieved. The microstructure of the bonded interface and the joining mechanisms are analyzed with scanning electron microscope (SEM), energy dispersive X-ray fluorescence spectrometer (EDX). It is observed that the bonding region across the interface consists of the metal layer, oxide transitional layer and the ceramic layer, with the transitional layer composed of surface region and sub-surface region. The bonding process can mainly be categorized into anodic bonding process and solid state diffusing process. The pile-up of the ions and its drift in the interface area are the main reasons for anode oxidation and joining of the interface. The temperature, voltage and the drift ions in the ceramic or glass during the bonding process are the essential conditions to solid state diffusing and oxide bonding at the interface. The voltages, temperature, pressure as well as the surface state are the main factors that influence the anodic bonding. 相似文献
7.
Wang Xuegang Yan Fengjie Yan Qian Li Xingeng 《Frontiers of Materials Science in China》2007,1(2):225-227
An iron-based amorphous foil (FeNiCrSiB) was used as an interlayer for the amorphous diffusion bonding of low carbon steel
pipes under argon flux. The microstructure and mechanical properties of the joint were analyzed using an electron probe micro-analyzer
(EPMA), tensile test, bending test and impact test. The results show that the joint microstructure resembles that of the base
metal and no precipitates form at the joint. Melting point depressants (B, Si) diffuse far away from the joint and the base
metal element is homogenous across the joint. The joint impact toughness is greater than the base metal toughness and the
mechanical properties of the joint are similar around the pipe. 相似文献
8.
The structural properties and hydrogen bonding of undoped and phosphorous doped polycrystalline silicon produced by step-by-step laser dehydrogenation and crystallization technique were investigated using Raman spectroscopy and hydrogen effusion measurements. At low laser fluences, EL, a two-layer system is created. This is accompanied by the change in hydrogen bonding. The intensity of the Si–H vibration mode at 2000 decreases faster than the one at 2100 cm−1. This is even more pronounced in phosphorous-doped specimens. The laser crystallization results in an increase of the hydrogen binding energy by approximately 0.2–0.3 eV compared to the amorphous starting materials. 相似文献
9.
介绍了一个计算机远程控制系统的设计与实现,该系统采用客户机/服务器模式,实现远程屏幕的实时传输,采用LZW压缩算法对图像进行压缩传输,在接受方进行解码并且实现了远程文件创建和删除、显示被控制端的主机信息、发送实时消息等功能。采用鼠标,键盘的模拟方式对计算机进行实时控制。 相似文献
10.
对称配筋小偏心受压构件的截面设计 总被引:4,自引:1,他引:3
对小偏心受压构件在对称配筋情况下的截面配筋计算,提出用最佳一次逼近多项式简化基本公式,直接按二次方程求解ξ的近似方法,具有精度高,相对误差小,计算方便等优点,可供工程设计人员参考。 相似文献