全文获取类型
收费全文 | 36563篇 |
免费 | 3943篇 |
国内免费 | 1611篇 |
专业分类
电工技术 | 8055篇 |
综合类 | 3099篇 |
化学工业 | 6185篇 |
金属工艺 | 878篇 |
机械仪表 | 1555篇 |
建筑科学 | 1844篇 |
矿业工程 | 1378篇 |
能源动力 | 1764篇 |
轻工业 | 1780篇 |
水利工程 | 329篇 |
石油天然气 | 883篇 |
武器工业 | 226篇 |
无线电 | 6860篇 |
一般工业技术 | 1632篇 |
冶金工业 | 1974篇 |
原子能技术 | 913篇 |
自动化技术 | 2762篇 |
出版年
2024年 | 155篇 |
2023年 | 459篇 |
2022年 | 872篇 |
2021年 | 1098篇 |
2020年 | 1068篇 |
2019年 | 836篇 |
2018年 | 807篇 |
2017年 | 1034篇 |
2016年 | 1258篇 |
2015年 | 1291篇 |
2014年 | 2340篇 |
2013年 | 2163篇 |
2012年 | 2756篇 |
2011年 | 2797篇 |
2010年 | 2116篇 |
2009年 | 2152篇 |
2008年 | 1962篇 |
2007年 | 2613篇 |
2006年 | 2260篇 |
2005年 | 1858篇 |
2004年 | 1733篇 |
2003年 | 1544篇 |
2002年 | 1247篇 |
2001年 | 1105篇 |
2000年 | 951篇 |
1999年 | 712篇 |
1998年 | 481篇 |
1997年 | 434篇 |
1996年 | 383篇 |
1995年 | 320篇 |
1994年 | 300篇 |
1993年 | 210篇 |
1992年 | 204篇 |
1991年 | 136篇 |
1990年 | 96篇 |
1989年 | 100篇 |
1988年 | 86篇 |
1987年 | 35篇 |
1986年 | 23篇 |
1985年 | 29篇 |
1984年 | 25篇 |
1983年 | 18篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1962年 | 2篇 |
1955年 | 3篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
一种高并行度的H.264帧内预测器的VLSI设计 总被引:3,自引:2,他引:1
分析了帧内预测的17种模式,对于每个4×4大小块的16个像素点的不同模式的预测公式之间的相同运算,采用数字强度缩减的方法去除计算的冗余,提出了一种高并行度的帧内预测器,可以每个时钟周期处理16个像素点的预测值。基于SMIC0.18μm工艺,用verilog对该设计进行了VLSI实现,综合后的电路的关键路径最大时延为10ns,电路规模不超过1.4万门,数据吞吐率可以达到1600Msamples/s。从实现结果来看,与采用可重构方法的设计相比,该设计在相同的并行度下减小了电路面积,简化了控制逻辑。 相似文献
172.
为解决某型航空断路器的耐振问题,利用MSC Adams/Vibration仿真工具对其建模与仿真. 找出影响耐振性能的主要原因,从而提高产品质量. 相似文献
173.
174.
集成电路的现状及其发展趋势 总被引:5,自引:0,他引:5
集成电路是信息社会经济发展的基石。通过对集成电路发展规律的分析,从集成电路的设计、制造、新产品研发和市场动态等方面,描述了集成电路的最新动态;探讨了集成电路的发展趋势;指出集成电路与其它学科、技术的结合,不断形成新的研究方向;新材料、新结构、新器件不断涌现,特征尺寸继续缩小,摩尔定律仍然起作用。 相似文献
175.
176.
Zhi‐Long Ye Min Lu Yan Zheng Ya‐Hong Li Wei‐Min Cai 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(11):1541-1550
BACKGROUND: Food waste generally has a high starch content and is rich in nutritional compounds, including lipids and proteins. It therefore represents a potential renewable resource. In this study, dining‐hall food waste was used as a substrate for lactic acid production, and response surface methodology was employed to optimise the fermentation conditions. RESULTS: Lactic acid biosynthesis was significantly affected by the interaction of protease and temperature. Protease, temperature and CaCO3 had significant linear effects on lactic acid production, while α‐amylase and yeast extract had insignificant effects. The optimal conditions were found to be an α‐amylase activity of 13.86 U g?1 dried food waste, a protease activity of 2.12 U g?1 dried food waste, a temperature of 29.31 °C and a CaCO3 concentration of 62.67 g L?1, which resulted in a maximum lactic acid concentration of 98.51 g L?1 (88.75% yield). An increase in inoculum size would be appropriate for accelerating the depletion of initial soluble carbohydrate to enhance the efficiency of α‐amylase in dining‐hall food waste fermentation. CONCLUSION: A suitable regression model for lactic acid production was developed based on the experimental results. Dining‐hall food waste was found to be a good substrate for lactic acid fermentation with high product yield and without nutrient supplementation. Copyright © 2008 Society of Chemical Industry 相似文献
177.
We present the fabrication and short circuit test results of a 14 kV single-phase resistive superconducting fault current limiter (SFCL) based on YBa2Cu3O7 (YBCO) films. Individual components were processed using the 4″ YBCO films and have the rated voltage and current of 600 V and 35 A at 77 K, respectively. Twenty four components, eight components in series and three lines in parallel, make a module having the rated voltage and current of 4.8 kV and 105 A, respectively. Three modules were assembled in series to produce the SFCL working at 77 K, a 14 kV single-phase machine for the 22.9 kV Y-Y grid. short circuit tests were successfully conducted in an accredited test facility with the maximum fault currents up to 14.1 kAP. All components quenched together upon faults and shared the rated voltage evenly without any supplementary device between the modules. This proves that the SFCL based on YBCO films may not only work reliably at 22.9 kV, but also provide technical feasibility for higher voltage application including the transmission grids. 相似文献
178.
虚拟绝对式光电编码器的设计和通信方式 总被引:1,自引:0,他引:1
介绍了虚拟绝对式光电编码器的位置检测原理以及通过外部倍频电路进一步提高其分辨力的方法,并给出了一种实用的编码器与伺服驱动器之间的串行通信协议设计。 相似文献
179.
180.
Use of zeolite-rich rocks and waste materials for the production of structural lightweight concretes
R. de Gennaro A. Langella M. D'Amore M. Dondi A. Colella P. Cappelletti M. de' Gennaro 《Applied Clay Science》2008,41(1-2):61-72
This paper aims at testing the use of mixtures constituted by natural zeolitized products and SiC-bearing industrial wastes (sludge deriving from polishing of porcelain stoneware tiles, hereafter DPM) for the production of lightweight expanded aggregates as constituents of structural and/or thermo-insulating lightweight concretes. Two commercial products have been used as zeolite natural source: Cab70 (Yellow facies of Campanian Ignimbrite) and IZclino (Turkish clinoptilolite-rich epiclastite). Different amounts of a calcareous material (Pozzano limestones — hereafter CP) from the Sorrento peninsula (Naples — Italy) were also added to a Cab70–DPM mixture. All raw materials were characterized by means of mineralogical (XRPD) and chemical (XRF) analyses. All the products and mixtures were tested from a technological point of view by means of fusibility and firing tests in order to evaluate the expanding properties. It was evidenced that the expansion of the mixture was deeply depending on the occurrence of SiC in the industrial waste. The addition of CP (10 wt.%) to the mixtures accounts for an even increased expansion, though this is accompanied by a worsening of the mechanical features of the material.These results along with literature data allowed to select 3 mixtures (70% Cab70–30% DPM, 70% IZclino–30% DPM, 60% Cab70–30% DPM–10% CP) and each of them was used for the preparation of 5 l of lightweight aggregates afterward employed for the manufacture of lightweight concretes. It was remarked that natural zeolitized materials mixed with DPM (30 wt.%) can provide lightweight aggregates with densities ranging between 0.8 and 1.0 g/cm3 suitable for the preparation of structural lightweight concretes. The addition to the mixture of CP (10 wt.%) produces less dense aggregates (0.6–0.7 g/cm3) potentially useful for the manufacture of thermo insulating lightweight concretes. 相似文献