全文获取类型
收费全文 | 182920篇 |
免费 | 18072篇 |
国内免费 | 11177篇 |
专业分类
电工技术 | 13206篇 |
技术理论 | 5篇 |
综合类 | 15758篇 |
化学工业 | 27215篇 |
金属工艺 | 10441篇 |
机械仪表 | 12315篇 |
建筑科学 | 14205篇 |
矿业工程 | 5362篇 |
能源动力 | 5094篇 |
轻工业 | 14656篇 |
水利工程 | 4279篇 |
石油天然气 | 8333篇 |
武器工业 | 1910篇 |
无线电 | 22668篇 |
一般工业技术 | 18990篇 |
冶金工业 | 7596篇 |
原子能技术 | 2463篇 |
自动化技术 | 27673篇 |
出版年
2024年 | 821篇 |
2023年 | 2779篇 |
2022年 | 5560篇 |
2021年 | 7704篇 |
2020年 | 5746篇 |
2019年 | 4665篇 |
2018年 | 4990篇 |
2017年 | 5822篇 |
2016年 | 5414篇 |
2015年 | 7859篇 |
2014年 | 10002篇 |
2013年 | 11856篇 |
2012年 | 13620篇 |
2011年 | 14532篇 |
2010年 | 13243篇 |
2009年 | 12831篇 |
2008年 | 12570篇 |
2007年 | 11746篇 |
2006年 | 10978篇 |
2005年 | 8931篇 |
2004年 | 6584篇 |
2003年 | 5405篇 |
2002年 | 5833篇 |
2001年 | 5022篇 |
2000年 | 3686篇 |
1999年 | 2897篇 |
1998年 | 2014篇 |
1997年 | 1657篇 |
1996年 | 1538篇 |
1995年 | 1353篇 |
1994年 | 1015篇 |
1993年 | 755篇 |
1992年 | 580篇 |
1991年 | 466篇 |
1990年 | 361篇 |
1989年 | 258篇 |
1988年 | 223篇 |
1987年 | 147篇 |
1986年 | 102篇 |
1985年 | 93篇 |
1984年 | 77篇 |
1983年 | 64篇 |
1982年 | 49篇 |
1981年 | 43篇 |
1980年 | 55篇 |
1979年 | 37篇 |
1977年 | 24篇 |
1976年 | 37篇 |
1959年 | 17篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
3‐Chlorothiophene (CT) was electrochemically polymerized in mixed electrolytes of a boron trifluoride diethyl etherate solution containing 0–20% (by volume) sulfuric acid. The oxidation potentials of the monomer in these media were measured to be only 1.06–1.31 V (vs Ag/AgCl). These values were much lower than that of CT in acetonitrile and 0.1 mol/L (Bu)4NBF4 (1.92 V vs Ag/AgCl). Poly(3‐chlorothiophene) (PCT) films with conductivities of 0.1–2 S cm?1 were obtained. The structure, morphology, and electrochemical behavior of the PCT films also were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 502–509, 2003 相似文献
73.
The empirical equation, 1/ti = AeEi/RT, which expresses the exponential dependence of the reciprocal of crystallization induction time, ti, has been analyzed and shown to be equivalent to the nucleation rate equations derived earlier in Part III (1). Consequently we have used the ti measurements obtained earlier by Krueger and Yeh to calculate not only the nucleation rate enhancements but also the melting point elevations, the relative crystal thickness changes and molecular coil extension ratios of shear-crystallization polyethylene. It is shown that polyethylene when crystallized between 129 and 131°C at shear rates between 1.56 and 9.70 sec?1 can have melting point increases of 4.2 to 7.2°C and crystal thickness decreases of 20 to 25 percent, when compared to those crystallized at 130°C in the quiescent state. The predicted “coil” extension in the melt just prior to shear-induced crystallization ranges between 21 and 36 percent. The results of these analyses as well as those on nucleation rates of polyethylene oxide are discussed in detail. 相似文献
74.
Partially observable Markov decision process (POMDP) is an ideal framework for sequential decision-making under uncertainty in stochastic domains. However, it is notoriously computationally intractable to solving POMDP in real-time system. In order to address this problem, this paper proposes a point-based online value iteration (PBOVI) algorithm which involves performing value backup at specific reachable belief points, rather than over the entire belief simplex, to speed up computation processes, exploits branch-and-bound pruning approach to prune the AND/OR tree of belief states online, and proposes a novel idea to reuse the belief states that have been searched to avoid repeated computation. The experiment and simulation results show that the proposed algorithm can simultaneously satisfy the requirement of low errors and high timeliness in real-time system. 相似文献
75.
Chunnuan Ji Rongjun Qu Cheng Bo Cao Huo Chen Qiang Xu Changmei Sun Chunhua Wang Huafang Yuan Jun Zhou 《应用聚合物科学杂志》2006,102(6):6054-6059
A novel chelating resin containing sulfoxide and diethylene glycol, poly{4‐vinylbenzyl‐[2‐2‐(hydroxyethyl)ethoxyl]sulfoxide} (PVESO) was synthesized using chloromethylated polystyrene (PS‐Cl) as material. Its structure was characterized by elemental analysis, infrared spectra, and scanning electron microscopy (SEM). The adsorption capacities of the resin for Hg2+, Ag+, Cu2+, Zn2+, and Pb2+ at various pH values were determined. The maximum adsorption capacities for Hg2+ and Ag+ were 1.56 and 0.75 mmol g?1 respectively. The resin had high selectivity for Hg2+ and Ag+ over the pH range 1.0–7.0. The adsorption capacities for Hg2+ and Ag+ under competitive condition were also determined by batch experiment method. In addition, the adsorption kinetics of the resin towards Hg2+ at different temperatures was also investigated. The results showed that the adsorption rate was governed by film diffusion at 20°C and 25°C, by particle diffusion at 30°C and 35°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6054–6059, 2006 相似文献
76.
77.
枸杞黑果病是枸杞产区的主要病害.发病后造成黑花、黑蕾和黑果,使枸杞产量降低,品质变劣。为探明四种杀菌剂对枸杞黑果病的防治效果及最佳剂量,2003年对下述四种杀菌剂进行了田间药效对比试验,调查防效结果如下:20%三苯基醋酸锡WP450~281g/hm^2(以有效成分计,下同),20%氟硅唑EC21.08g/hm^21.5%噻霉酮EW16、88~21.08g/hm^2、40%氟硅唑EC450g/hm^2和70%甲基托布津WP787.5g/hm^2对枸杞黑果病防效均在88.25%以上。经LSD检验各处理间防效无显著差异。 相似文献
78.
79.
80.
从节能、降低成本、优化工艺的角度,对无菌空气制备过程中,空气预处理流程的选择、空气净化设备、过滤介质以及设备的遴选进行探讨,以实现工艺和工程设计的优化结合。 相似文献