全文获取类型
收费全文 | 5588篇 |
免费 | 992篇 |
国内免费 | 199篇 |
专业分类
电工技术 | 192篇 |
综合类 | 207篇 |
化学工业 | 2288篇 |
金属工艺 | 157篇 |
机械仪表 | 169篇 |
建筑科学 | 123篇 |
矿业工程 | 83篇 |
能源动力 | 136篇 |
轻工业 | 201篇 |
水利工程 | 21篇 |
石油天然气 | 35篇 |
武器工业 | 12篇 |
无线电 | 780篇 |
一般工业技术 | 705篇 |
冶金工业 | 180篇 |
原子能技术 | 32篇 |
自动化技术 | 1458篇 |
出版年
2024年 | 13篇 |
2023年 | 151篇 |
2022年 | 109篇 |
2021年 | 412篇 |
2020年 | 302篇 |
2019年 | 223篇 |
2018年 | 309篇 |
2017年 | 266篇 |
2016年 | 312篇 |
2015年 | 305篇 |
2014年 | 489篇 |
2013年 | 387篇 |
2012年 | 297篇 |
2011年 | 406篇 |
2010年 | 303篇 |
2009年 | 292篇 |
2008年 | 256篇 |
2007年 | 294篇 |
2006年 | 261篇 |
2005年 | 176篇 |
2004年 | 161篇 |
2003年 | 157篇 |
2002年 | 130篇 |
2001年 | 105篇 |
2000年 | 84篇 |
1999年 | 79篇 |
1998年 | 70篇 |
1997年 | 66篇 |
1996年 | 39篇 |
1995年 | 24篇 |
1994年 | 48篇 |
1993年 | 35篇 |
1992年 | 32篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 16篇 |
1988年 | 18篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 25篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有6779条查询结果,搜索用时 187 毫秒
61.
62.
63.
Karuppaiah Geetha Veerasamy Anitha Mohamed Elhoseny Shankar Kathiresan Pourya Shamsolmoali Mahmoud M. Selim 《Expert Systems》2021,38(1)
Recently, medical image compression becomes essential to effectively handle large amounts of medical data for storage and communication purposes. Vector quantization (VQ) is a popular image compression technique, and the commonly used VQ model is Linde–Buzo–Gray (LBG) that constructs a local optimal codebook to compress images. The codebook construction was considered as an optimization problem, and a bioinspired algorithm was employed to solve it. This article proposed a VQ codebook construction approach called the L2‐LBG method utilizing the Lion optimization algorithm (LOA) and Lempel Ziv Markov chain Algorithm (LZMA). Once LOA constructed the codebook, LZMA was applied to compress the index table and further increase the compression performance of the LOA. A set of experimentation has been carried out using the benchmark medical images, and a comparative analysis was conducted with Cuckoo Search‐based LBG (CS‐LBG), Firefly‐based LBG (FF‐LBG) and JPEG2000. The compression efficiency of the presented model was validated in terms of compression ratio (CR), compression factor (CF), bit rate, and peak signal to noise ratio (PSNR). The proposed L2‐LBG method obtained a higher CR of 0.3425375 and PSNR value of 52.62459 compared to CS‐LBG, FA‐LBG, and JPEG2000 methods. The experimental values revealed that the L2‐LBG process yielded effective compression performance with a better‐quality reconstructed image. 相似文献
64.
65.
Stephen O. Dean 《Journal of Fusion Energy》1988,7(1):25-47
Fusion is an essentially inexhaustible source of energy that has the potential for economically attractive commercial applications with excellent safety and environmental characteristics. The primary focus for the fusion-energy development program is the generation of centralstation electricity. Fusion has the potential, however, for many other applications. The fact that a large fraction of the energy released in a DT fusion reaction is carried by high-energy neutrons suggests potentially unique applications. These include breeding of fissile fuels, production of hydrogen and other chemical products, transmutation or burning of various nuclear or chemical wastes, radiation processing of materials, production of radioisotopes, food preservation, medical diagnosis and medical treatment, and space power and space propulsion. In addition, fusion R&D will lead to new products and new markets.Each fusion application must meet certain standards of economic and safety and environmental attractiveness. For this reason, economics on the one hand, and safety and environment and licensing on the other hand, are the two primary criteria for setting long-range commercial fusion objectives. A major function of systems analysis is to evaluate the potential of fusion against these objectives and to help guide the fusion R&D program toward practical applications. The transfer of fusion technology and skills from the national laboratories and universities to industry is the key to achieving the long-range objective of commercial fusion applications. 相似文献
66.
赵彦香 《计算机光盘软件与应用》2012,(3):123+125
当今科技日新月异,经济发展迅猛,也带动了网络技术的不断高速发展,并广泛的应用于各大领域(军事、经济和政治等)。在计算机网络技术的广泛应用形势下,它的安全性问题也就逐渐的突显出来,引起了行业内人士的广泛关注。因此对网络应用中的安全性问题进行分析与探究是迫在眉睫的任务。本文首先论述了其应用中最常见的几大安全性问题,以及说明了对其安全问题所需要防护的相关策略。 相似文献
67.
林芳 《计算机光盘软件与应用》2012,(2):57-58
任何人在使用SQL Server数据库系统的时候,都希望自己能让SQL数据库发挥出他最佳的性能,但提供它性能的方法就是对其系统进行优化。本文主要通过笔者在日常工作生活中的经历和经验来简单讲述下SQL Server数据库在运用中的一些技巧。 相似文献
68.
纳米气泡是直径在1μm以下的气泡,已被证明可以在固液界面、体相中长期稳定存在。基于跨越气液界面的拉普拉斯压强定理,气泡无法保持热力学稳定,将在微秒的尺度上消失。然而,大量试验报道,体相纳米气泡可以长时间稳定存在。目前,关于纳米气泡的产生技术、表征手段和相关的稳定机制已被世界各国的课题组竞相报道。该综述对现有纳米气泡的研究成果,尤其是体相纳米气泡的研究进行总结概述。首先,总结了体相纳米气泡产生和表征的主要方法;其次,介绍了体相纳米气泡的稳定机制;再次,概括了体相纳米气泡的试验应用情况;最后,对体相纳米气泡的进一步研究和应用作出展望。 相似文献
69.
Thermal sprayed aluminum and zinc provide long-term (> 20 years to first maintenance) corrosion control coatings. However,
this application is usually more expensive than painting or galvanizing if thermal spraying (metallizing) is not integrated
into the design and fabrication phases of new construction and repair projects. Aluminum and zinc metallized coatings are
tough enough to withstand fabrication, transportation, and assembly operations. The improved capabilities and productivity
of metallizing equipment for aluminum and zinc spraying are a major factor in their current cost competitiveness. The net
result is that the cost difference between metallizing, paint, and galvanizing is getting closer every day. Even though the
initial application cost of metallizing may be higher, the life cycle cost (LCC) and average equivalent annual costs (AEAC)
are lower than paint coating systems. Metallizing LCCs, when properly engineered into the construction schedule, are equal
to or less than paint coating LCCs. This article summarizes some metallizing considerations for installing improved corrosion
control coating systems in new construction and in maintenance and repair of infrastructure.
Editor’s Note: The following constants have been used to convert between English and Metric dimensions: 1ft2-0.0929 m2; 1lb/ft2-4.89 kg/m2; 1 mil=0.025mm.
Presented at the 5th National Thermal Spray Conference (NTSC-93), Infrastructure Maintenance and Repair Session, 10 June 1993,
Anaheim, CA. 相似文献
70.
Alfarooq O.Basheer Marlia M.Hanafiah Mohammed Abdulhakim Alsaadi Y.Al-Douri Abbas A.Al-Raad 《中国化学工程学报》2021,32(4):472-484
Date palm fiber (DPF) derived from agrowaste was utilized as a new precursor for the optimized synthesis of a cost-effective, nanostructured, powder-activated carbon (nPAC) for aluminum (Al3+) removal from aqueous solutions using carbonization, KOH activation, response surface methodology (RSM) and central composite design (CCD). The optimum synthesis condition, activation temperature, time and impregna-tion ratio were found to be 650 ℃, 1.09 hour and 1:1, respectively. Furthermore, the optimum conditions for removal were 99.5%and 9.958 mg·g-1 in regard to uptake capacity. The optimum conditions of nPAC was analyzed and characterized using XRD, FTIR, FESEM, BET, TGA and Zeta potential. Moreover, the adsorption of the Al3+ conditions was optimized with an integrated RSM-CCD experimental design. Regression results revealed that the adsorption kinetics data was well fitted by the pseudo-second order model, whereas the adsorption isotherm data was best represented by the Freundlich isotherm model. Optimum activated carbon indicated that DPF can serve as a cost-effective precursor adsorbent for Al3+removal. 相似文献