全文获取类型
收费全文 | 193471篇 |
免费 | 17005篇 |
国内免费 | 9707篇 |
专业分类
电工技术 | 12954篇 |
技术理论 | 11篇 |
综合类 | 14261篇 |
化学工业 | 31136篇 |
金属工艺 | 10990篇 |
机械仪表 | 12053篇 |
建筑科学 | 15611篇 |
矿业工程 | 5672篇 |
能源动力 | 5486篇 |
轻工业 | 15717篇 |
水利工程 | 4020篇 |
石油天然气 | 10674篇 |
武器工业 | 1745篇 |
无线电 | 21632篇 |
一般工业技术 | 21569篇 |
冶金工业 | 8422篇 |
原子能技术 | 2114篇 |
自动化技术 | 26116篇 |
出版年
2024年 | 923篇 |
2023年 | 3190篇 |
2022年 | 5926篇 |
2021年 | 8004篇 |
2020年 | 6136篇 |
2019年 | 5009篇 |
2018年 | 5507篇 |
2017年 | 6296篇 |
2016年 | 5476篇 |
2015年 | 7957篇 |
2014年 | 9729篇 |
2013年 | 11469篇 |
2012年 | 13106篇 |
2011年 | 14030篇 |
2010年 | 12514篇 |
2009年 | 11919篇 |
2008年 | 11902篇 |
2007年 | 11073篇 |
2006年 | 10793篇 |
2005年 | 9075篇 |
2004年 | 6441篇 |
2003年 | 5818篇 |
2002年 | 5863篇 |
2001年 | 5192篇 |
2000年 | 4448篇 |
1999年 | 4212篇 |
1998年 | 3305篇 |
1997年 | 2816篇 |
1996年 | 2500篇 |
1995年 | 2204篇 |
1994年 | 1766篇 |
1993年 | 1268篇 |
1992年 | 1017篇 |
1991年 | 815篇 |
1990年 | 589篇 |
1989年 | 495篇 |
1988年 | 408篇 |
1987年 | 274篇 |
1986年 | 204篇 |
1985年 | 117篇 |
1984年 | 82篇 |
1983年 | 60篇 |
1982年 | 70篇 |
1981年 | 52篇 |
1980年 | 65篇 |
1979年 | 22篇 |
1976年 | 5篇 |
1972年 | 4篇 |
1959年 | 13篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
101.
102.
Soap‐free emulsion copolymerization of perfluoroalkyl acrylate (FA)/methyl methacrylate (MMA)/n‐butyl acrylate (n‐BA) was carried out in the presence of sodium 2‐acrylamide‐2‐methyl propanesulfonate (AMPSNa) as a reactive surfactant and potassium persulfate (KPS) as an initiator. An analysis of the effects of concentration of AMPSNa, KPS, FA as well as polymerization temperature on the kinetic features (rate of polymerization) and colloidal characteristics (mean particle diameter, particle disperse index, particle numbers, and surface charge density) was followed. NMR, FTIR, AFM, and fluorine‐selective electrode analysis were used to characterize the composition and morphology of the FA copolymers. Both AFM analysis and contact angle measurements strongly implied that the fluorinated segments migrated to the outmost surface and created films with lower surface energy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2438–2444, 2007 相似文献
103.
Hao Liang Zhiqiang Zheng Zengchang Li Jie Xu Biao Chen Hui Zhao Qijin Zhang Hai Ming 《应用聚合物科学杂志》2004,93(2):681-685
A step‐index polymer optical fiber (SI POF) containing Rhodamine B in poly(methyl methacrylate) (PMMA) has been fabricated by a preform technique. Fluorescence of different fiber lengths were observed and discussed. A high gain (23 dB) for a SI POF with 60‐cm length, 400‐μm diameter was obtained. The Rhodamine B content of the doped SI POF is 5 ppm‐wt. The signal wavelength providing the highest gain for a 60 cm SI POF is around 630 nm, and the optimum fiber length is about 60 cm at 10 kW launched pump power. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 681–685, 2004 相似文献
104.
The autoclave products of reduced steel-slag of an electronic furnace mainly containing C3MS2 phase were detected. The hydrothermal products of this slag included calcio-chondrodite, brucite, and hydrogarnet phases. When suitable (CaO + MgO)/SiO2 molar ratios were chosen, C3MS2 can react with SiO2 to produce calcium silicate hydrates tobermorite, xonotlite, gyrolite, and truscottite phases with different saturated water vapor pressures. The phase brucite was present along with tobermorite, whereas phases Mg-xonotlite, Mg-gyrolite, and Mg-truscottite can rarely coexist with brucite. Hydrogarnet phase disappeared when Mg-truscottite was formed. 相似文献
105.
106.
阐述了塑料结构壁管的基本情况和国内外现状.重点就扬子石油化工股份有限公司研究院研制的聚丙烯结构壁管专用料的情况进行了介绍。 相似文献
107.
采用Nova-Pak C18不锈钢色谱柱进行反相液相色谱分析,以甲醇:水=65:35(V/V)为注动相,以邻苯二甲醇二乙酯为内标物,用内标法测定田草灵除草剂中苄嘧黄隆和异丙甲草胺的含量,结果表明,各有效成分与内标物色谱峰分离完全,杂质无干扰,测定结果,苄嘧黄隆和异丙甲草胺的变异系数分别为0.74%和1.07%,回收率分别为99.4% ̄100.8%和99.1% ̄101.3%。 相似文献
108.
Multi-label core vector machine (Rank-CVM) is an efficient and effective algorithm for multi-label classification. But there still exist two aspects to be improved: reducing training and testing computational costs further, and detecting relevant labels effectively. In this paper, we extend Rank-CVM via adding a zero label to construct its variant with a zero label, i.e., Rank-CVMz, which is formulated as the same quadratic programming form with a unit simplex constraint and non-negative ones as Rank-CVM, and then is solved by Frank–Wolfe method efficiently. Attractively, our Rank-CVMz has fewer variables to be solved than Rank-CVM, which speeds up training procedure dramatically. Further, the relevant labels are effectively detected by the zero label. Experimental results on 12 benchmark data sets demonstrate that our method achieves a competitive performance, compared with six existing multi-label algorithms according to six indicative instance-based measures. Moreover, on the average, our Rank-CVMz runs 83 times faster and has slightly fewer support vectors than its origin Rank-CVM. 相似文献
109.
110.
Decolorisation and mineralisation of CI Reactive Black 8 by the Fenton and ultrasound/Fenton methods
The effects of pH, ferrous ion and hydrogen peroxide dosage on the decolorisation and mineralisation of CI Reactive Black 8 by the Fenton process with/without ultrasonic irradiation were investigated. It was verified that the presence of ultrasonic irradiation did not enhance the decolorisation of CI Reactive Black 8 significantly by Fenton's reagents, but it enhanced the chemical oxygen demand removal efficiency. The enhancement was more pronounced for lower (<0.89 mm) or higher (>1.78 mm) ferrous ion dosage. The optimal pH for chemical oxygen demand removal was 3.0. Chemical oxygen demand removal efficiency increased with the increasing H2 O2 dosage and reached the highest level at 5.88 mm, but further increase in H2 O2 dosage would not increase removal efficiency significantly. 相似文献