全文获取类型
收费全文 | 3568篇 |
免费 | 263篇 |
国内免费 | 129篇 |
专业分类
电工技术 | 181篇 |
综合类 | 164篇 |
化学工业 | 716篇 |
金属工艺 | 191篇 |
机械仪表 | 170篇 |
建筑科学 | 470篇 |
矿业工程 | 51篇 |
能源动力 | 90篇 |
轻工业 | 169篇 |
水利工程 | 63篇 |
石油天然气 | 140篇 |
武器工业 | 25篇 |
无线电 | 368篇 |
一般工业技术 | 407篇 |
冶金工业 | 308篇 |
原子能技术 | 121篇 |
自动化技术 | 326篇 |
出版年
2023年 | 18篇 |
2022年 | 54篇 |
2021年 | 80篇 |
2020年 | 77篇 |
2019年 | 79篇 |
2018年 | 64篇 |
2017年 | 89篇 |
2016年 | 124篇 |
2015年 | 131篇 |
2014年 | 190篇 |
2013年 | 271篇 |
2012年 | 231篇 |
2011年 | 242篇 |
2010年 | 171篇 |
2009年 | 167篇 |
2008年 | 152篇 |
2007年 | 189篇 |
2006年 | 165篇 |
2005年 | 160篇 |
2004年 | 155篇 |
2003年 | 211篇 |
2002年 | 119篇 |
2001年 | 124篇 |
2000年 | 74篇 |
1999年 | 70篇 |
1998年 | 50篇 |
1997年 | 47篇 |
1996年 | 60篇 |
1995年 | 36篇 |
1994年 | 36篇 |
1993年 | 25篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 12篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 16篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 9篇 |
1981年 | 22篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 25篇 |
1975年 | 10篇 |
1974年 | 6篇 |
排序方式: 共有3960条查询结果,搜索用时 359 毫秒
1.
Zhijiang Li Yingping Zheng Liqin Cao Lei Jiao Yanfei Zhong Caiyi Zhang 《Color research and application》2020,45(4):656-670
Image color clustering is a basic technique in image processing and computer vision, which is often applied in image segmentation, color transfer, contrast enhancement, object detection, skin color capture, and so forth. Various clustering algorithms have been employed for image color clustering in recent years. However, most of the algorithms require a large amount of memory or a predetermined number of clusters. In addition, some of the existing algorithms are sensitive to the parameter configurations. In order to tackle the above problems, we propose an image color clustering method named Student's t-based density peaks clustering with superpixel segmentation (tDPCSS), which can automatically obtain clustering results, without requiring a large amount of memory, and is not dependent on the parameters of the algorithm or the number of clusters. In tDPCSS, superpixels are obtained based on automatic and constrained simple non-iterative clustering, to automatically decrease the image data volume. A Student's t kernel function and a cluster center selection method are adopted to eliminate the dependence of the density peak clustering on parameters and the number of clusters, respectively. The experiments undertaken in this study confirmed that the proposed approach outperforms k-means, fuzzy c-means, mean-shift clustering, and density peak clustering with superpixel segmentation in the accuracy of the cluster centers and the validity of the clustering results. 相似文献
2.
3.
Md. Abdur Rahim Shamim Mahbub Md. Kamrul Islam Sk. Md. Ali Ahsan Shahed Rana Malik Abdul Rub Anish Khan Md. Anamul Hoque 《Journal of surfactants and detergents》2020,23(2):457-470
Conductometric and cloud point (CP) measurement studies have been performed to investigate the interaction of tetradecyltrimethylammonium bromide (TTAB) and Triton® X-100 (TX-100) with ciprofloxacin hydrochloride (CFH) in different solvents over the temperature range of 295.15–315.15 K. CFH is used for the treatment of various bacterial infections. The observed critical micelle concentration (CMC) values of TTAB were found to be reduced in the presence of electrolytes (Na2SO4/Na3PO4), and this reduction proceeds with the elevation of salt concentration. The order of the CMC of TTAB follows the trend: > >. The observed CMC values of TTAB were found to increase with increasing temperature and decrease with increasing concentration of CFH in aqueous medium. The values of Gibbs free energy of micellization () for the TTAB/TTAB + CFH mixture were found to be negative, implying spontaneous micellization. The estimated CP of TX-100 decreases with increasing concentration of TX-100 in aqueous medium. The CP values first decrease with increasing concentration of CFH and then increase at higher concentration of CFH almost in all cases investigated. The values of free energy of clouding were found to be positive in all cases studied implying that phase separation of TX-100 was nonspontaneous. The other thermodynamic parameters associated with the micellization of TTAB and the phase separation of TX-100 were estimated and explained. 相似文献
4.
介绍用已知年龄和烧结温度的古陶片穆斯堡尔超精细参数与年龄和烧结温度的实验关系曲线作基础,应用计算机模拟程序,自动求出未知陶片的年龄和最高烧结温度的方法。 相似文献
5.
Daniela M. Nevskaia Maria Luisa Rojas Cervantes Antonio Guerrero Ruíz Juan de Dios Lpez Gonzlez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):249-256
Adsorption of Triton X-100 on various silica substrates has been investigated. A number of solids, including a natural quartz, this quartz washed with HCl acid and subsequently heated at 1273 K; two aerosils and one Kieselgel silicas were studied. These solids exhibit surface areas in the range of 5 to 430 m2 g?1. All the Triton adsorption isotherms display an S-shape at the adsorption temperatures studied (298 and 308 K). It has been found that the pretreatments of natural quartz (by water washing, impurities removed by acid and/or high temperature calcination) affect considerably the amounts of TX-100 adsorbed. Measurements of surface composition have been made by X-ray photoelectron spectroscopy (XPS) with particular emphasis on the presence of impurities and on the number of OH groups at the surface of the samples. The nature of the surface hydroxyl has also been studied by infrared spectroscopy. Furthermore, the specific number of hydroxyl groups on the surface of the silica samples has been determined by thermogravimetric analysis. Finally an attempt to correlate solid surface characteristics with adsorption isotherms has been developed. 相似文献
6.
堇青石基玻璃陶瓷的制备与展望 总被引:2,自引:0,他引:2
介绍了制备堇青石基玻璃陶瓷的三种方法:熔融法、烧结法和溶胶-凝胶法,综述了玻璃组成、添加剂和成核剂对堇青石基玻璃陶瓷的烧结及性能的影响,并对其未来的发展进行了展望。 相似文献
7.
Masami Ikeda Susumu Fukumoto Hiroshi Takao Shinya Ohtsuka Eiichi Haginomori Masayuki Hikita 《Electrical Engineering in Japan》2002,141(4):16-24
This paper describes the dielectric breakdown characteristics of oil and oil‐impregnated paper for very fast transient (VFT) voltages. Blumlein circuits generate VFT voltages of 60 and 300 ns in a pulse width that simulates disconnecting switching surges in gas‐insulated switch gears. We measured the breakdown voltages of needle‐to‐plane, plane‐to‐plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V‐t characteristics and Weibull probability distributions. The inclination n of V‐t characteristics of insulating paper is 150, which is less than n = 13.7 of the plane‐to‐plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 16–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10043 相似文献
8.
9.
针对定径机换辊后定径钢管所出现的质量问题,提出了成品机架的轧辊孔型不分配变形量和适当增大孔型直径的改进措施。 相似文献
10.
用电话网实现远程监控自动化 总被引:1,自引:0,他引:1
彭启候 《水电自动化与大坝监测》2002,26(4):70-73
分析了偏僻高山上通信机房和电气房要进行监控的内容和特点等,探讨 了用经济、可靠的电话交换网实现远程监控自动化的方案和实施办法。该设计根据监控对象 的特点,利用现有的电话网络和程控交换机实现远程监控,不需要专用通信传输通道,不需 要增加硬件和软件,成本低,技术成熟,容易实现。 相似文献