全文获取类型
收费全文 | 49350篇 |
免费 | 3947篇 |
国内免费 | 2028篇 |
专业分类
电工技术 | 2603篇 |
技术理论 | 8篇 |
综合类 | 3044篇 |
化学工业 | 8653篇 |
金属工艺 | 2727篇 |
机械仪表 | 3232篇 |
建筑科学 | 3724篇 |
矿业工程 | 1715篇 |
能源动力 | 1432篇 |
轻工业 | 2771篇 |
水利工程 | 786篇 |
石油天然气 | 3864篇 |
武器工业 | 446篇 |
无线电 | 5332篇 |
一般工业技术 | 5930篇 |
冶金工业 | 2491篇 |
原子能技术 | 493篇 |
自动化技术 | 6074篇 |
出版年
2024年 | 245篇 |
2023年 | 916篇 |
2022年 | 1497篇 |
2021年 | 2029篇 |
2020年 | 1578篇 |
2019年 | 1331篇 |
2018年 | 1499篇 |
2017年 | 1651篇 |
2016年 | 1461篇 |
2015年 | 1945篇 |
2014年 | 2378篇 |
2013年 | 2903篇 |
2012年 | 2939篇 |
2011年 | 3320篇 |
2010年 | 2781篇 |
2009年 | 2687篇 |
2008年 | 2772篇 |
2007年 | 2523篇 |
2006年 | 2603篇 |
2005年 | 2292篇 |
2004年 | 1439篇 |
2003年 | 1351篇 |
2002年 | 1224篇 |
2001年 | 1098篇 |
2000年 | 1212篇 |
1999年 | 1426篇 |
1998年 | 1128篇 |
1997年 | 947篇 |
1996年 | 848篇 |
1995年 | 766篇 |
1994年 | 634篇 |
1993年 | 471篇 |
1992年 | 360篇 |
1991年 | 263篇 |
1990年 | 220篇 |
1989年 | 152篇 |
1988年 | 136篇 |
1987年 | 87篇 |
1986年 | 63篇 |
1985年 | 35篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 24篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 4篇 |
1978年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
Fine Granularity Scalability (FGS) video coding has been adopted by the MPEG-4 standard for video streaming applications. In this paper, we propose a novel FGS coding scheme, which applied adaptive leaky factors for the enhancement layer prediction to further improve the coding efficiency of FGS. A flexible method that can dynamically determine the leaky factors according to the network conditions is also presented. With the proposed method, a better trade-off between the coding efficiency and drifting reduction can be achieved, and the coding performance is further improved compared with using a fixed leaky factor. Experimental results show that the proposed method can further improve the coding efficiency over a wide range of bitrate and packet loss ratio, and still keep the original characteristics, such as fine granularity, and bandwidth adaptation. 相似文献
104.
介绍了“新合纤”研究开发的历史过程以及“新合纤”的特征及其加工方法,讨论了“新合纤”研究开发的现状及其未来。 相似文献
105.
岩性圈闭储层描述技术及应用 总被引:4,自引:1,他引:3
本文以高分辨率地震资料为基础,应用测井、钻井等资料,从沉积微相分析入手,建立了以河道砂体、河口坝砂体为主的地质及地震响应模型,并根据地震反射波组特征、地震反演的阻抗值及其他地震属性参数,确定了研究区的砂体变化及其分布规律,总结出一套针对薄互层特点的岩性圈闭识别技术。本文方法在大庆长垣以西古龙和他拉哈西地区的实际应用中取得了明显的效果。 相似文献
106.
107.
在过去几年里,小型PCB诸如硅芯片级以及便携式移动电话的生产者和设计者们已经发现:如果要保持自己的竞争力并具备生产高密度封装板能力,就必须采用微孔技术。微孔技术的出现要求针对微孔缺陷的有效检测手段对工艺进行过程控制。本文对激光微孔的自动光学检测进行了详细介绍。 相似文献
108.
Xinru Xu Jingyi Yang Ying Jiang Jinsheng Gao 《Petroleum Science and Technology》2006,24(11):1307-1321
The efficiency of desalting for six crude oils was studied with a SY-1 dynamic simulation experimental installation. The demulsifier DC2 was examined for 1#, 2#, and 4# crude oil and DC4 was used for 3#, 5#, and 6# crude oil. The effects of temperature, electric field gradient, dosage of demulsifier, and washing water on the desalting efficiency of six crude oils were investigated. The results showed that at the optimization process condition after desalting, the desalting efficiency and the salt content of 1# crude oil reached 89.17% and 1.92 mg/L; that of 2# crude oil reached 85.08% and 1.04 mg/L; that of 3# crude oil reached 91.06% and 1.35 mg/L; that of 4# crude oil reached 81.67% and 1.51 mg/L; that of 5# crude oil reached 81.03% and 2.32 mg/L; and that of 6# crude oil reached 86.64% and 2.67 mg/L. Different crude oils have different metal contents. Three assistants, ammonium nitrate (TJ1), nitric acid (TJ3), and polyamine carboxylate (TJ4), were used to improve the efficiencies of desalting and demetalization of six crude oils. TJ4 was more efficient in removing calcium and iron for 1# and 2# crude oil. TJ1 was more efficient in desalting and demetalizing 5# crude oil. The efficiencies for removal of calcium, iron, nickel, and vanadium respectively reached 99.89%, 98.33%, 20.58%, and 43.02%. TJ3 has better efficiency desalting and demetalizing for 6# crude oil. With the concentration of TJ3 increasing from 0 to 80 mg/L, the desalting efficiency increases from 31.22% to 73.54%, and the iron removal efficiency increases from 56.0% to 74.05%. 相似文献
109.
A novel mixed‐mode expanded bed adsorbent with anion‐exchange properties was explored with benzylamine as the functional ligand. The cellulose composite matrix, densified with stainless steel powder, was prepared with the method of water‐in‐oil suspension thermal regeneration. High activation levels of the cellulose matrix were obtained with allyl bromide because of the relative inertness of the allyl group under the conditions of the activation reaction. After the formation of the bromohydrin with N‐bromosuccinimide and coupling with benzylamine, the activated matrix was derived to function as a mixed‐mode adsorbent containing both hydrophobic and ionic groups. The protein adsorption capacity was investigated with bovine serum albumin as a model protein. The results indicated that the prepared adsorbent could bind bovine serum albumin with a high adsorption capacity, and it showed salt tolerance. Effective desorption was achieved by a pH adjustment across the isoelectric point of the protein. The interactions between the cell and adsorbent were studied, and the bioadhesion was shielded by the adjustment of the salt concentration above 0.1M. Stable fluidization in the expanded bed was obtained even in a 2% (dry weight) yeast suspension. The direct capture of target proteins from a biomass‐containing feedstock without extra dilution steps could be expected with the mixed‐mode adsorbent prepared in this work, and this would be especially appropriate for expanded bed adsorption applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
110.