全文获取类型
收费全文 | 96403篇 |
免费 | 9279篇 |
国内免费 | 5438篇 |
专业分类
电工技术 | 7084篇 |
技术理论 | 4篇 |
综合类 | 7113篇 |
化学工业 | 14683篇 |
金属工艺 | 5208篇 |
机械仪表 | 6204篇 |
建筑科学 | 8304篇 |
矿业工程 | 2914篇 |
能源动力 | 2805篇 |
轻工业 | 6659篇 |
水利工程 | 2079篇 |
石油天然气 | 4939篇 |
武器工业 | 1198篇 |
无线电 | 11749篇 |
一般工业技术 | 10293篇 |
冶金工业 | 4453篇 |
原子能技术 | 1296篇 |
自动化技术 | 14135篇 |
出版年
2024年 | 503篇 |
2023年 | 1570篇 |
2022年 | 3172篇 |
2021年 | 4376篇 |
2020年 | 3213篇 |
2019年 | 2523篇 |
2018年 | 2804篇 |
2017年 | 3218篇 |
2016年 | 2876篇 |
2015年 | 4132篇 |
2014年 | 5091篇 |
2013年 | 6141篇 |
2012年 | 7080篇 |
2011年 | 7445篇 |
2010年 | 6595篇 |
2009年 | 6386篇 |
2008年 | 6220篇 |
2007年 | 5701篇 |
2006年 | 5478篇 |
2005年 | 4745篇 |
2004年 | 3162篇 |
2003年 | 2356篇 |
2002年 | 2254篇 |
2001年 | 1930篇 |
2000年 | 1922篇 |
1999年 | 1792篇 |
1998年 | 1447篇 |
1997年 | 1208篇 |
1996年 | 1181篇 |
1995年 | 994篇 |
1994年 | 743篇 |
1993年 | 648篇 |
1992年 | 487篇 |
1991年 | 336篇 |
1990年 | 328篇 |
1989年 | 225篇 |
1988年 | 191篇 |
1987年 | 130篇 |
1986年 | 113篇 |
1985年 | 70篇 |
1984年 | 59篇 |
1983年 | 42篇 |
1982年 | 43篇 |
1981年 | 34篇 |
1980年 | 35篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 15篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
The electron spin resonance (ESR) spectra of end‐group spin labelled poly(ethylene oxide) (SLPEO) using 2,2,6,6‐tetramethyl‐piperdine‐1‐oxyl nitroxide and its blends with poly(styrene‐co‐4‐vinylphenol) (STVPhs) of different hydroxyl contents were recorded over a wide temperature range. For a blend of SLPEO and pure polystyrene (PS), the ESR spectrum was composed of a single motion component, indicating that PS was immiscible with PEO. For blends composed of SLPEO and different‐hydroxyl‐content STVPhs, two spectral components with different motion rates were observed over a certain temperature range. The difference between the motion rates should be attributed to micro‐heterogeneity in the blends, with the faster rate corresponding to a nitroxide radical motion trapped in the PEO‐rich domain and the slower rate corresponding to a nitroxide radical motion trapped in the STVPh‐rich domain. Variations in the values of a number of the ESR parameters (Ta, Td and T50G) and the apparent activation energy (Ea) with hydroxyl content in the blends indicated that the miscibility of the blends increased with increasing hydrogen‐bonding density due to specific interactions between the hydroxyl groups in STVPh and the ether oxygens in PEO. Copyright © 2004 Society of Chemical Industry 相似文献
42.
小麦胚的营养价值及应用开发 总被引:1,自引:0,他引:1
小麦胚是小麦籽粒的精华,本文论述了小麦胚蛋白和小麦胚芽油的营养价值、制取及其开发利用,并分析了小麦胚资源开发利用存在的问题及其途径。 相似文献
43.
The long‐term thermal‐oxidative aging behavior of polyamide 6 (PA6) was studied by comparison with the stabilized sample in this work. The variation of mechanical properties of the pure and the stabilized samples of PA6 with aging time at 110°C, 130°C, and 150°C were investigated, respectively. The aging mechanism of PA6 under heat and oxygen was studied in terms of the reduced viscosity, crystallization behavior, dynamic mechanical behavior, and chemical composition through the methods of polarized light microscopy (PLM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X‐ray photoelectron energy spectrum (XPS), and so on. The results indicated that at the initial stage of aging, the molecular crosslinking reaction of PA6 dominated resulting in the increase of the mechanical strength, reduced viscosity, and the glass transition temperature of the sample. And the molecular degradation dominated in the subsequent aging process resulting in the decrease of the melting temperature, the increase of the crystallinity, and the formation of the oxides and peroxides products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
44.
Biphenol monoacrylate (AL) was combined with a traditional hindered phenolic‐based binary antioxidant system to form a ternary stabilization system for the purpose of further improving the thermal–oxidative stability of polyamide 6 (PA6). The thermal stabilization effect of the antioxidant AL on PA6 was studied in terms of the reduced viscosity, the chemical structure, the yellow index, and the mechanical properties. The results showed that the antioxidant AL, with the proper chemical structure, could improve the thermal stability of PA6 effectively through a unique bifunctional stabilizing mechanism. The interaction of the molecules of PA6 with the antioxidant AL was investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
45.
Yanhan Shen Rongrong Qi Qiaochu Liu Yanling Wang Yapeng Mao Juan Yu 《应用聚合物科学杂志》2008,110(4):2261-2266
The grafting of a polymer can lead to the improvement and modification of the polymer and thus expand its applications. Grafting methods include solution grafting in organic solvents, melt grafting at high temperatures, and light grafting with radioactive sources. These methods have their advantages and disadvantages. The disadvantages include waste treatment, consumption of energy, and so on. In this study, a hydrothermal process which is called the green approach, was developed to prepare graft copolymers. The effect of various factors on the grafting degree was investigated in detail. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
46.
Novel calix[4]arene‐poly(ethylene glycol) crosslinked polymer (CCP) has been synthesized by the polycondensation reaction between a p‐tert‐butylcalix[4]arene derivative and dihydroxyl capped poly(ethylene glycol) (DHPEG, Mn = 1000) catalyzed by neodymium tosylate. The hydrogel, consisted of 66.9% water and 33.1% CCP, can selectively extract aromatic organic molecules from aqueous solution according to the diameter of the guest molecules, which infers that the diameter of the calix[4]arene cavity is about 5.4 Å and the conformation of calix[4]arene units altered from cone conformation to 1,3‐alternate conformation during the polycondensation reaction. Furthermore, CCP can also adsorb naphthalene from gas phase, showing much higher capacity than active carbon does, which may have some potential applications in the field of separation and environment protection. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
47.
48.
ROI-based Watermarking Scheme for JPEG 2000 总被引:1,自引:0,他引:1
Yu-Cheng Fan Arvin Chiang Jan-Hung Shen 《Circuits, Systems, and Signal Processing》2008,27(5):763-774
A new region of interest (ROI)-based watermarking method for JPEG 2000 is presented. The watermark is embedded into the host
image based on the characteristics of the ROI to protect rights to the images. This scheme integrates the watermarking process
with JPEG 2000 compression procedures. Experimental results have demonstrated that the proposed watermark technique successfully
survives JPEG 2000 compression, progressive transmission, and principal attacks. 相似文献
49.
50.
沈国金 《武汉理工大学学报(信息与管理工程版)》2006,28(8):139-142
针对目前大学生职业规划效果不佳的现状,分析了导致大学生职业规划效果不佳的原因,提出了增强大学生职业规划效果的宏观对策。 相似文献