全文获取类型
收费全文 | 73864篇 |
免费 | 6080篇 |
国内免费 | 4081篇 |
专业分类
电工技术 | 4408篇 |
技术理论 | 1篇 |
综合类 | 7002篇 |
化学工业 | 11219篇 |
金属工艺 | 3992篇 |
机械仪表 | 4520篇 |
建筑科学 | 5022篇 |
矿业工程 | 1674篇 |
能源动力 | 1919篇 |
轻工业 | 6482篇 |
水利工程 | 1472篇 |
石油天然气 | 4300篇 |
武器工业 | 547篇 |
无线电 | 8610篇 |
一般工业技术 | 7565篇 |
冶金工业 | 3344篇 |
原子能技术 | 982篇 |
自动化技术 | 10966篇 |
出版年
2024年 | 218篇 |
2023年 | 762篇 |
2022年 | 1456篇 |
2021年 | 2057篇 |
2020年 | 1625篇 |
2019年 | 1463篇 |
2018年 | 1564篇 |
2017年 | 1798篇 |
2016年 | 1788篇 |
2015年 | 2490篇 |
2014年 | 3380篇 |
2013年 | 4105篇 |
2012年 | 4900篇 |
2011年 | 5539篇 |
2010年 | 4987篇 |
2009年 | 4909篇 |
2008年 | 4915篇 |
2007年 | 4725篇 |
2006年 | 4675篇 |
2005年 | 3927篇 |
2004年 | 3528篇 |
2003年 | 3119篇 |
2002年 | 3721篇 |
2001年 | 3195篇 |
2000年 | 2172篇 |
1999年 | 1602篇 |
1998年 | 1023篇 |
1997年 | 843篇 |
1996年 | 742篇 |
1995年 | 641篇 |
1994年 | 477篇 |
1993年 | 358篇 |
1992年 | 295篇 |
1991年 | 212篇 |
1990年 | 180篇 |
1989年 | 116篇 |
1988年 | 112篇 |
1987年 | 80篇 |
1986年 | 33篇 |
1985年 | 52篇 |
1984年 | 43篇 |
1983年 | 32篇 |
1982年 | 19篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 17篇 |
1978年 | 9篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
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
44.
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
45.
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
46.
47.
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
48.
介绍了国产YL-100型自动加药装置功能及其在中国石化茂名石化乙烯工业公司乙烯循环水场的应用情况,结果表明其运行平稳,总磷测试数据可靠,可达到循环水自动加药控制的目的。 相似文献
49.
应红 《电脑编程技巧与维护》2014,(18):23-23
通过实例,详细讲解用Word的窗体工具建立表单,以解决行政部门制作电子文档的空白表格时,让填写的人员方便、快捷地填写内容,又不随意修改(破坏)原有格式和原文。 相似文献
50.
Three-dimensionally ordered long-range macroporous carbon structures were prepared using commercially available phenolic resin
by utilizing sacrificial colloidal silica crystalline arrays as templates that were subsequently removed by HF etching after
pyrolysis in an argon atmosphere. SEM, TEM, and BET were employed to characterize the morphology and the surface area of the
porous carbon structures. The pore size (150–1000 nm) and BET surface area, which reflect pore volume (298.6 m2/g (1.32 cm3/g) ∼ 93.7 m2/g (0.12 cm3/g)), of the macroporous carbon structures produced were approximately proportional to the size (150–1000 nm) of the sacrificial
silica sphere templates used (annealing temp. 550°C). The achieved 550 nm porous carbon structures were examined to function
as potential catalyst carriers and were successfully impregnated with Ag or Pt-Ru on their inner walls after borohydride reduction
at room temperature. In addition, porous carbon patterns were fabricated using the ‘micromolding in capillary’ technique,
which has potential applications in the microreaction technology. 相似文献