全文获取类型
收费全文 | 2463篇 |
免费 | 95篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 45篇 |
综合类 | 5篇 |
化学工业 | 545篇 |
金属工艺 | 43篇 |
机械仪表 | 79篇 |
建筑科学 | 56篇 |
矿业工程 | 1篇 |
能源动力 | 89篇 |
轻工业 | 119篇 |
水利工程 | 8篇 |
石油天然气 | 3篇 |
无线电 | 467篇 |
一般工业技术 | 452篇 |
冶金工业 | 263篇 |
原子能技术 | 8篇 |
自动化技术 | 380篇 |
出版年
2023年 | 13篇 |
2022年 | 41篇 |
2021年 | 52篇 |
2020年 | 29篇 |
2019年 | 34篇 |
2018年 | 53篇 |
2017年 | 45篇 |
2016年 | 52篇 |
2015年 | 41篇 |
2014年 | 90篇 |
2013年 | 190篇 |
2012年 | 142篇 |
2011年 | 158篇 |
2010年 | 118篇 |
2009年 | 151篇 |
2008年 | 153篇 |
2007年 | 137篇 |
2006年 | 99篇 |
2005年 | 82篇 |
2004年 | 75篇 |
2003年 | 69篇 |
2002年 | 65篇 |
2001年 | 49篇 |
2000年 | 43篇 |
1999年 | 47篇 |
1998年 | 107篇 |
1997年 | 85篇 |
1996年 | 43篇 |
1995年 | 39篇 |
1994年 | 34篇 |
1993年 | 28篇 |
1992年 | 33篇 |
1991年 | 29篇 |
1990年 | 12篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1973年 | 6篇 |
1967年 | 3篇 |
排序方式: 共有2563条查询结果,搜索用时 0 毫秒
11.
Kiang S.-Z. Baker R.L. Sullivan G.J. Chiu C.-Y. 《IEEE transactions on image processing》1992,1(2):162-169
A pruning algorithm of P.A. Chou et al. (1989) for designing optimal tree structures identifies only those codebooks which lie on the convex hull of the original codebook's operational distortion rate function. The authors introduce a modified version of the original algorithm, which identifies a large number of codebooks having minimum average distortion, under the constraint that, in each step, only modes having no descendents are removed from the tree. All codebooks generated by the original algorithm are also generated by this algorithm. The new algorithm generates a much larger number of codebooks in the middle- and low-rate regions. The additional codebooks permit operation near the codebook's operational distortion rate function without time sharing by choosing from the increased number of available bit rates. Despite the statistical mismatch which occurs when coding data outside the training sequence, these pruned codebooks retain their performance advantage over full search vector quantizers (VQs) for a large range of rates. 相似文献
12.
Jui-Chieh Chiu Chieh-Pin Chang Mau-Phon Houng Yeong-Her Wang 《Microwave and Wireless Components Letters, IEEE》2006,16(1):19-21
A novel configuration of balanced frequency InGaAs pseudomorphic high electron mobility transistor (PHEMT) monolithic microwave integrated circuit (MMIC) tripler is proposed. A resonant LC filter is used to eliminate the fundamental frequency and a phase delay line is employed to suppress the second harmonic. The separation of the independent phase shifters makes the tripler more compact and flexible. The conversion loss of the tripler operating from 12 to 36GHz is less than 9.4dB at 9-dBm input power. As compared to the third-harmonic frequency, the fundamental frequency is suppressed more than 21.4dB while for the second harmonic is more than 22.3dB at 36GHz. 相似文献
13.
W.R. Jong T.H. Kuo S.W. Ho H.H. Chiu S.H. Peng 《International Communications in Heat and Mass Transfer》2007
Capillary phenomena was studied and discussed by the scholars about 200 years ago, but the progress was slow due to the limited equipment and manufacture precision of the microchannel. In recent years, because of the rapid development of MEMS and micromachining, many applications of the capillary flow is widely developing in some modern processes, such as underfilling of flip chip, flow in microfluidic chip or biochip, and a variety of other fields. 相似文献
14.
Energy function analysis of dynamic programming neural networks 总被引:2,自引:0,他引:2
All analytical examination of the energy function associated with a dynamic programming neural network is presented. The analysis is carried out in two steps. First, the locations and numbers of the minimum states for different components of the energy function are investigated in the extreme cases. A clearer insight into the energy function can be gained through the minimum states of different components. Secondly, the locations of the minimum states of the energy function using different parameter values are derived. It is shown that the minimum states can reside in regions which are regarded as valid solutions with certain conditions. Examples and simulation results are given to justify the validity of the theories developed. 相似文献
15.
16.
Bibliometric analysis of tsunami research 总被引:3,自引:0,他引:3
The use of the bibilometric analytical technique for examining tsunami research does not exist in the literature. The objective
of the study was to perform a bibliometric analysis of all tsunami-related publications in the Science Citation Index (SCI).
Analyzed parameters included document type, language of publication, publication output, authorship, publication patterns,
distribution of subject category, distribution of author keywords, country of publication, most-frequently cited article,
and document distribution after the Indonesia tsunami. The US and Japan produced 53% of the total output where the seven major
industrial countries accounted for the majority of the total production. English was the dominant language, comprising 95%
of articles. A simulation model was applied to describe the relationship between the number of authors and the number of articles,
the number of journals and the number of articles, and the percentage of total articles and the number of times a certain
keyword was used. Moreover the tsunami publication patterns in the first 8 months after the Indonesia tsunami occurred on
26 December 2004 indicated a high percentage of non-article publications and more documents being published in journals with
higher impact factors. 相似文献
17.
18.
19.
The behavior of a spatially smoothing adaptive array is examined. An expression for the weight vector is first derived. Using the array gain on the desired signal and the coherent interference is obtained. Then the expression for output signal-to-noise (SNR) is derived. It shows that the performance of the spatially smoothing array depends on the number of the subarrays, the angle separation, relative power and initial phase difference between the desired signal and the coherent interference. For good interference suppression it is found that the magnitude of the phase difference of the incident and interference signals must be greater than the beamwidths of both the subarray and the equivalent array. There is also a tradeoff between increasing the groups of subarrays and decreasing the number of elements in the subarrays. Computer simulation results are given that validate the analysis 相似文献
20.
The use of zero-valent iron for treating wastewaters containing RDX and perchlorate from an army ammunition plant (AAP) in the USA at elevated temperatures and moderately elevated temperature with chemical addition was evaluated through batch and column experiments. RDX in the wastewater was completely removed in an iron column after 6.4 minutes. Increasing the temperature to 75 degrees C decreased the required retention time to 2.1 minutes for complete RDX removal. Perchlorate in the wastewater was completely removed by iron at an elevated temperature of 150 degrees C in batch reactors in 6 hours without pH control. Significant reduction of perchlorate by zero-valent iron was also achieved at a more moderate temperature (75 degrees C) through use of a 0.2 M acetate buffer. Based on the evaluation results, we propose two innovative processes for treating RDX-containing and perchlorate-containing wastewaters: a temperature and pressure-controlled batch iron reactor and subsequent oxidation by existing industrial wastewater treatment plant; and reduction by consecutive iron columns with heating and acid addition capabilities and subsequent oxidation. 相似文献