全文获取类型
收费全文 | 92666篇 |
免费 | 7947篇 |
国内免费 | 4250篇 |
专业分类
电工技术 | 5631篇 |
技术理论 | 9篇 |
综合类 | 5720篇 |
化学工业 | 13468篇 |
金属工艺 | 5205篇 |
机械仪表 | 5811篇 |
建筑科学 | 6594篇 |
矿业工程 | 2954篇 |
能源动力 | 2380篇 |
轻工业 | 5627篇 |
水利工程 | 1621篇 |
石油天然气 | 5154篇 |
武器工业 | 838篇 |
无线电 | 9799篇 |
一般工业技术 | 9333篇 |
冶金工业 | 3832篇 |
原子能技术 | 974篇 |
自动化技术 | 19913篇 |
出版年
2024年 | 438篇 |
2023年 | 1513篇 |
2022年 | 2786篇 |
2021年 | 3647篇 |
2020年 | 2877篇 |
2019年 | 2303篇 |
2018年 | 2643篇 |
2017年 | 2950篇 |
2016年 | 2655篇 |
2015年 | 3867篇 |
2014年 | 4830篇 |
2013年 | 5560篇 |
2012年 | 6452篇 |
2011年 | 9245篇 |
2010年 | 6399篇 |
2009年 | 5892篇 |
2008年 | 5525篇 |
2007年 | 5026篇 |
2006年 | 4822篇 |
2005年 | 4287篇 |
2004年 | 3099篇 |
2003年 | 2693篇 |
2002年 | 2150篇 |
2001年 | 1874篇 |
2000年 | 1835篇 |
1999年 | 1783篇 |
1998年 | 1438篇 |
1997年 | 1161篇 |
1996年 | 1038篇 |
1995年 | 940篇 |
1994年 | 758篇 |
1993年 | 552篇 |
1992年 | 435篇 |
1991年 | 308篇 |
1990年 | 260篇 |
1989年 | 220篇 |
1988年 | 161篇 |
1987年 | 105篇 |
1986年 | 77篇 |
1985年 | 46篇 |
1984年 | 56篇 |
1983年 | 46篇 |
1982年 | 33篇 |
1981年 | 27篇 |
1980年 | 24篇 |
1979年 | 9篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1959年 | 5篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
21.
22.
Colour remains one of the key factors in presenting an object and, consequently, has been widely applied in retrieval of images based on their visual contents. However, a colour appearance changes with the change of viewing surroundings, the phenomenon that has not been paid attention yet while performing colour‐based image retrieval. To comprehend this effect, in this article, a chromatic contrast model, CAMcc, is developed for the application of retrieval of colour intensive images, cementing the gap that most of existing colour models lack to fill by taking simultaneous colour contrast into account. Subsequently, the model is applied to the retrieval task on a collection of museum wallpapers of colour‐rich images. In comparison with current popular colour models including CIECAM02, HSI and RGB, with respect to both foreground and background colours, CAMcc appears to outperform the others with retrieved results being closer to query images. In addition, CAMcc focuses more on foreground colours, especially by maintaining the balance between both foreground and background colours, while the rest of existing models take on dominant colours that are perceived the most, usually background tones. Significantly, the contribution of the investigation lies in not only the improvement of the accuracy of colour‐based image retrieval but also the development of colour contrast model that warrants an important place in colour and computer vision theory, leading to deciphering the insight of this age‐old topic of chromatic contrast in colour science. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 361–373, 2015 相似文献
23.
24.
双检合并技术在海底电缆地震资料处理中被广泛应用,可衰减电缆鬼波的影响。传统方式以水、陆检记录的波场记录相同为假设,电缆鬼波压制效果差,合并效果并不理想。在分析交叉鬼波化双检合并技术基本原理的基础上,综合利用水检资料与陆检鬼波褶积的结果和陆检资料与水检鬼波褶积的结果求取刻度算子,同时在地震资料处理中利用陆检资料标定水检资料,从而优化了交叉鬼波化双检合并技术。实际资料处理结果表明,改进后的技术可有效衰减电缆鬼波,分离出上行波场,大幅度拓宽地震资料频带,提高地震资料分辨率,从而提供更丰富的构造细节信息。 相似文献
25.
Weikang Dong Ruishi Qi Tiansheng Liu Yi Li Ning Li Ze Hua Zirui Gao Shuyuan Zhang Kaihui Liu Jiandong Guo Peng Gao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2002014
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer. 相似文献
26.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献
27.
28.
Bin Zhang Xuesong Jiang Fei Shen Xueming He Yong Fang Qiuhui Hu 《International Journal of Food Science & Technology》2021,56(6):2588-2595
This work intends to develop an online experimental system for screening of deoxynivalenol (DON) contamination in whole wheat meals by visible/near-infrared (Vis/NIR) spectroscopy and computer vision coupling technology. Spectral and image information of samples with various DON levels was collected at speed of 0.15 m s−1 on a conveyor belt. The two-type data were then integrated and subjected to chemometric analysis. Discriminant analysis showed that samples could be classified by setting 1000 μg kg−1 as the cut-off value. The best correct classified rate obtained in prediction was 93.55% based on fusion of spectral and image features, with reduced prediction uncertainty as compared to single feature. However, quantification of DON by quantitative analysis was not successful due to poor model performance. These results indicate that, although not accurate enough to provide conclusive result, this coupling technology could be adopted for rapid screening of DON contamination in cereals and feeds during processing. 相似文献
29.