全文获取类型
收费全文 | 2394篇 |
免费 | 290篇 |
国内免费 | 148篇 |
专业分类
电工技术 | 134篇 |
综合类 | 176篇 |
化学工业 | 259篇 |
金属工艺 | 61篇 |
机械仪表 | 89篇 |
建筑科学 | 490篇 |
矿业工程 | 126篇 |
能源动力 | 66篇 |
轻工业 | 194篇 |
水利工程 | 84篇 |
石油天然气 | 143篇 |
武器工业 | 13篇 |
无线电 | 117篇 |
一般工业技术 | 246篇 |
冶金工业 | 189篇 |
原子能技术 | 10篇 |
自动化技术 | 435篇 |
出版年
2024年 | 7篇 |
2023年 | 29篇 |
2022年 | 78篇 |
2021年 | 96篇 |
2020年 | 88篇 |
2019年 | 84篇 |
2018年 | 62篇 |
2017年 | 71篇 |
2016年 | 87篇 |
2015年 | 86篇 |
2014年 | 192篇 |
2013年 | 190篇 |
2012年 | 229篇 |
2011年 | 234篇 |
2010年 | 143篇 |
2009年 | 163篇 |
2008年 | 140篇 |
2007年 | 132篇 |
2006年 | 124篇 |
2005年 | 84篇 |
2004年 | 90篇 |
2003年 | 81篇 |
2002年 | 67篇 |
2001年 | 53篇 |
2000年 | 38篇 |
1999年 | 37篇 |
1998年 | 31篇 |
1997年 | 19篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有2832条查询结果,搜索用时 203 毫秒
91.
To improve the watermark benchmarks database, a new BRA (Block Replacement Attack) method is introduced in this paper. Unlike the typical BRA which exploits the self similarity among blocks in image, the scheme utilizes the self similarity in various scale and orientation bands in the wavelet domain of the image. They search the replacement blocks from the blocks of the smaller sub image at the next lower resolution. The most important advantage of this scheme is that the pyramid sub band decomposition acts as an automatic block classifier, with the result of simplifying the block search and block matching procedures and thus making the block replacement more effective. Furthermore, an improved algorithm based on Fuzzy set theory is introduced in which the number of blocks chosen for combination are modified adaptively to obtain the candidate replacement blocks. It simplifies the procedure for searching the candidate replacement blocks. These advantages are confirmed by the experimental results, which show that the performance of the scheme is superior to typical BRA methods. 相似文献
92.
Steganography is a technique to hide the secret data into digital media without getting any unexpected notices. The traditional steganographic method, namely least significant bit (LSB) replacement, is a simple but insecure scheme. To overcome the traditional drawbacks, this paper proposes a steganographic scheme, which is called double-layer hiding method. The experimental results confirm that the proposed scheme achieves better hiding capacity with high ability of resisting security analysis. 相似文献
93.
A series of bimetallic Pt–Au thin films with different Pt/Au ratios were fabricated on glassy carbon (GC) substrates through galvanic replacement reactions between hierarchical Co thin films prepared by cyclic voltammetric deposition and mixed solutions of HAuCl4 and H2PtCl6. The morphologies of the as-prepared Pt–Au thin films resemble those of the sacrificial Co templates, and the Pt/Au ratios in the films are dependent on the HAuCl4/H2PtCl6 molar ratios in the mixed solutions. Because of good stability and excellent synergistic effect of Au and Pt, the bimetallic films with novel structures display unexpected high catalytic activity for the oxidation of formic acid. The as-prepared hierarchical Pt–Au micro/nanostructures are expected to find applications as catalysts in direct formic acid fuel cells (DFAFCs). 相似文献
94.
95.
96.
In the current study, electrodeposition-redox replacement was applied to a hydrometallurgical solution with the main elements of Ca (13.8?g L?1), Al (4.7?g L?1), Cu (2.5?g L?1), Zn (1.2?g L?1), Fe (1.2?g L?1), S (1?g L?1), Mg (0.8?g L?1), P (0.5?g L?1) and Ag (3.5?ppm). The solution originated from the leaching experiment of incinerator plant bottom ash, which was dissolved into 2 M HCl media at T?=?30?°C. The resulting deposit on the electrode surface was analysed with SEM-EDS and the observed Ag/(Cu?+?Zn) ratio (0.3) indicated remarkable enrichment of silver on the surface, when compared to the ratio of these elements (Ag/(Cu?+?Zn)) in the solution (6.8?×?10?5). The enrichment of Ag vs. (Cu?+?Zn) could be demonstrated to increase ca. 4500 fold compared to the ratio of the elements in solution. 相似文献
97.
98.
煤对气体的吸附有强弱之分,多元气体之间存在竞争吸附和置换解吸。他们之间会不会因为气体进入的先后顺序不同而产生差异呢?为此进行了煤对CH4-CO2混合气体的竞争吸附和CO2置换煤中CH4的置换吸附对比实验。实验表明,煤对CH4-CO2二元气体的竞争吸附与置换解吸结果是一致的,理论分析表明煤对气体的吸附解吸与气体进入煤体先后顺序和过程无关,只与吸附前后的状态有关。气体置换煤中CH4的规律为:混合气体中强吸附性气体含量越大,置换效率越高;置换压力越大置换效率越高。最后对煤层注气措施提出了建议:应先将煤层瓦斯压力降到安全范围再实施注气措施。 相似文献
99.
A typical solid‐state drive contains several independent channels that can be operated in parallel. To exploit this channel‐level parallelism, a variety of works proposed to split consecutive write sequences into small segments and schedule them to different channels. This scheme exploits the parallelism but breaks the spatial locality of write traffic; thus, it is able to significantly degrade the efficiency of garbage collection. This paper proposes a channel‐aware write reordering (CAWR) mechanism to schedule write requests to different channels more intelligently. The novel mechanism encapsulates correlated pages into a cluster beforehand. All pages belonging to a cluster are scheduled to the same channels to exploit spatial locality, while different clusters are scheduled to different channels to exploit the parallelism. As CAWR covers both garbage collection and I/O performance, it outperforms existing schemes significantly. Trace‐driven simulation results demonstrate that the CAWR mechanism reduces the average response time by 26% on average and decreases the valid page copies by 10% on average, while achieving a similar hit ratio to that of existing mechanisms. 相似文献
100.