全文获取类型
收费全文 | 122648篇 |
免费 | 12348篇 |
国内免费 | 6916篇 |
专业分类
电工技术 | 8652篇 |
技术理论 | 10篇 |
综合类 | 10807篇 |
化学工业 | 18753篇 |
金属工艺 | 7296篇 |
机械仪表 | 7920篇 |
建筑科学 | 9503篇 |
矿业工程 | 3473篇 |
能源动力 | 3423篇 |
轻工业 | 12083篇 |
水利工程 | 2569篇 |
石油天然气 | 5980篇 |
武器工业 | 1246篇 |
无线电 | 13538篇 |
一般工业技术 | 13004篇 |
冶金工业 | 4606篇 |
原子能技术 | 1401篇 |
自动化技术 | 17648篇 |
出版年
2024年 | 592篇 |
2023年 | 2065篇 |
2022年 | 4252篇 |
2021年 | 5657篇 |
2020年 | 4245篇 |
2019年 | 3280篇 |
2018年 | 3619篇 |
2017年 | 4209篇 |
2016年 | 3642篇 |
2015年 | 5387篇 |
2014年 | 6941篇 |
2013年 | 7823篇 |
2012年 | 9150篇 |
2011年 | 9907篇 |
2010年 | 8811篇 |
2009年 | 8267篇 |
2008年 | 8326篇 |
2007年 | 7729篇 |
2006年 | 7290篇 |
2005年 | 5803篇 |
2004年 | 4092篇 |
2003年 | 3375篇 |
2002年 | 3397篇 |
2001年 | 2860篇 |
2000年 | 2365篇 |
1999年 | 2018篇 |
1998年 | 1466篇 |
1997年 | 1113篇 |
1996年 | 989篇 |
1995年 | 763篇 |
1994年 | 634篇 |
1993年 | 442篇 |
1992年 | 356篇 |
1991年 | 262篇 |
1990年 | 176篇 |
1989年 | 150篇 |
1988年 | 93篇 |
1987年 | 88篇 |
1986年 | 60篇 |
1985年 | 30篇 |
1984年 | 20篇 |
1983年 | 27篇 |
1982年 | 24篇 |
1981年 | 24篇 |
1980年 | 41篇 |
1979年 | 12篇 |
1974年 | 3篇 |
1970年 | 3篇 |
1959年 | 12篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 631 毫秒
991.
992.
Ye Wan Wenhui Guo Jin Xiao Dazhou Yan Xiong Zhao Shuhu Guo Jianhua Liu Qifan Zhong Tao Yang Yu Zhao Xin Chang Xin Gao 《中国化学工程学报》2020,28(9):2248-2255
Ultra-high-purity silicon tetrachloride (SiCl4) is demanded as an electronic-grade chemical to meet the stringent requirements of the rapidly developing semiconductor industry. The high requirement for ultra-high-purity SiCl4 has created the need for a high-efficient process for reducing energy consumption as well as satisfying product quality. In this paper, a mass of production technology of ultra-high-purity SiCl4 was successfully developed through chlorination reaction in the ultraviolet (UV)-based photo microreactor coupled with the distillation process. The influences of key operational parameters, including temperature, pressure, UV wavelength and light intensity on the product quality, especially for hydrogen-containing impurities, were quantified by the infrared transmittance of Fourier transform infrared spectroscopy (FT-IR) at 2185 cm−1 and 2160 cm−1 indicating that characteristic vibrational modes of SiH bonds, as well as the operating conditions of distillation were also investigated as key factors for metal impurities removing. The advanced intensification of SiCl4 manufactured by the integration of photo microreactor and distillation achieves the products with superior specifications higher than the standard commercial products. 相似文献
993.
Methane oxidation in paddy soils was investigated under laboratory conditions. Paddy soils collected before early rice transplanting
could not oxidize atmospheric CH4 but could oxidize CH4 when the concentration exceeded 10 μl l-1. Initial CH4 oxidation rate increased with the increase of initial CH4 concentration. Soil with the maximum potential to produce CH4, also had the maximum CH4 oxidation activity and the maximum emission flux from paddy soil. High CH4 concentration stimulated the oxidation of CH4. After 10 days' incubation under atmosphere containing 1000 μl-1 or 104 μl l-1 CH4, the soil which could not oxidize atmospheric CH4 was able to oxidize it.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
994.
Lo KM Zhang J Sun Y Morelli B Lan Y Lauder S Brunkhorst B Webster G Hallakou-Bozec S Doaré L Gillies SD 《Protein engineering, design & selection : PEDS》2005,18(1):1-10
Leptin plays a central role in the homeostasis of body weight through its regulatory effects on appetite and energy expenditure, yet in trials as a therapeutic agent for the treatment of obesity in humans it has been disappointing. The poor clinical efficacy of leptin results from its short circulating half-life, low potency and poor solubility, necessitating large and frequent doses to obtain even modest clinical benefit. Engineered Fc-leptin immunofusins, consisting of the Fc fragment of an immunoglobulin gamma chain followed by leptin, exhibit improved pharmacological properties with very consistent and potent biological activities. Furthermore, in extending the circulating half-life of the protein in vivo from a few minutes for leptin to many hours for Fc-leptin, these proteins have the potential to reduce drastically the dosage and frequency of administration required to obtain clinical benefit. The results of this study show that the engineered leptin immunofusins described here have significantly enhanced pharmacological properties in comparison with the recombinant leptin that was used in clinical trials. As such, they could represent an important step towards a therapeutically superior form of leptin if the disappointing performance of leptin in early clinical trials was due to its poor pharmacological properties rather than any conceptual weakness in the strategy of using leptin for the treatment of obesity and its related disorders. 相似文献
995.
轻质油品氧化脱硫技术进展 总被引:9,自引:1,他引:9
介绍了国内外轻质油品氧化脱硫技术的研究进展情况,分析了选择性氧化脱硫、超声波氧化脱硫、光催化氧化脱硫、等离子体液相氧化脱硫等技术的优缺点,展望了氧化脱硫技术应用前景。 相似文献
996.
可交联树脂19E的开发及应用 总被引:1,自引:0,他引:1
分析可交联树脂19E的产品设计及操作设计,并就产品性能与国内餐同类产品进行了对比,进而指出,19E适宜于生产35KV以下可交联电缆料。 相似文献
997.
久效磷原药的液相色谱分析 总被引:2,自引:0,他引:2
本文采用液相色谱法,选择C18色谱柱,甲醇水为流动相,240纳米检测,外标法宣,标准偏差0.35,变异系数0.45%,回收率平均值99.87%。 相似文献
998.
以硫脲配位用原子吸收法测定矿石中银 总被引:1,自引:0,他引:1
本实验是在近中性介质中,以硫脲为配位剂测定岩矿中银的新方法。样品用盐酸、王水、氢氟酸、高氯酸溶解,蒸干后加硫脲配位剂,使用乙炔—空气火焰测定银。 相似文献
999.
A mathematical model is developed for an industrial acrylonitrile fluidized-bed reactor based on artificial neural networks.A new algorithm,which combines the characteristics of both genetic algorithm(GA) and generalized delta-rule(GDR) is used to train artificial neural network (ANN) in order to avoid search terminated at a local optimal solution.For searching the global optimum,a new algorithm called SM-GA,incorporating advantages of both simplex method (SM) and GA, is proposed and applied to optimize the operating conditions of an acrylonitrile fluidized-bed reactor in industry. 相似文献
1000.
受全球气候变暖的影响,“中华水塔”地区正面临着以“变暖变湿”为主的气候变化。受气候及下垫面条件的综合影响,区域水资源显著增加,各流域产流机理在空间上呈现出明显的地区差异特征。基于“中华水塔”区域1956—2020年水文气象资料,通过趋势、突变、距平等分析方法,分析其水文要素和产流规律的变化趋势、特征及相互之间影响关系。结果表明:近年来“中华水塔”区域气温显著升高,蒸发能力总体增强,区域进入丰水期,降水、径流显著增加,在同等降水径流尺度下,黄河源区产流能力有所降低,长江、澜沧江源区产流能力明显增强;气温升高、降水量持续偏丰以及流域前期影响雨量(蓄水量)增加、枯季径流比例提高、下垫面生态持水能力增强是引起区域产流规律变化、水资源量增加的主要原因。 相似文献