全文获取类型
收费全文 | 63805篇 |
免费 | 5601篇 |
国内免费 | 2877篇 |
专业分类
电工技术 | 3594篇 |
技术理论 | 2篇 |
综合类 | 4121篇 |
化学工业 | 10703篇 |
金属工艺 | 3722篇 |
机械仪表 | 4071篇 |
建筑科学 | 4701篇 |
矿业工程 | 2142篇 |
能源动力 | 1693篇 |
轻工业 | 3996篇 |
水利工程 | 1076篇 |
石油天然气 | 3930篇 |
武器工业 | 524篇 |
无线电 | 7696篇 |
一般工业技术 | 7765篇 |
冶金工业 | 3068篇 |
原子能技术 | 634篇 |
自动化技术 | 8845篇 |
出版年
2024年 | 353篇 |
2023年 | 1133篇 |
2022年 | 1834篇 |
2021年 | 2593篇 |
2020年 | 1976篇 |
2019年 | 1767篇 |
2018年 | 1926篇 |
2017年 | 2120篇 |
2016年 | 1923篇 |
2015年 | 2482篇 |
2014年 | 3024篇 |
2013年 | 3622篇 |
2012年 | 4058篇 |
2011年 | 4459篇 |
2010年 | 3681篇 |
2009年 | 3518篇 |
2008年 | 3394篇 |
2007年 | 3300篇 |
2006年 | 3663篇 |
2005年 | 3032篇 |
2004年 | 2123篇 |
2003年 | 1797篇 |
2002年 | 1591篇 |
2001年 | 1444篇 |
2000年 | 1558篇 |
1999年 | 1708篇 |
1998年 | 1514篇 |
1997年 | 1267篇 |
1996年 | 1146篇 |
1995年 | 954篇 |
1994年 | 834篇 |
1993年 | 571篇 |
1992年 | 428篇 |
1991年 | 367篇 |
1990年 | 263篇 |
1989年 | 212篇 |
1988年 | 185篇 |
1987年 | 122篇 |
1986年 | 98篇 |
1985年 | 59篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 28篇 |
1981年 | 16篇 |
1980年 | 21篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
51.
中国石化扬子石油化工股份有限公司烯烃厂1号乙烯装置两台乙烷炉运行周期一直偏低,辐射段炉管使用寿命较短,并影响急冷油减粘系统的稳定运行。应用结焦抑制剂N-360后,乙烷炉运行周期与辐射段炉管使用寿命大幅延长,并且能耗下降、产品收率提高。 相似文献
52.
53.
羟基烷基磺酸镀液电镀Sn—Pb合金的研究 总被引:2,自引:0,他引:2
我国自行研制生产的羟基烷基磺酸电镀Sn-Pb合金镀液已经在部分厂家投产使用.生产实践证明,该镀液能获得不同铅含量的、可焊性优良且镀层结晶细致而光亮的Sn-Pb合金镀层.本研究重点测定了该镀液的电化学性能,如阴极电流效率、分散能力及深镀能力.并对添加剂的作用进行了研究探讨. 相似文献
54.
55.
通过我国农药工业与国外的差距的分析,笔者认为我国农药企业要走集团化的道路,由仿制为主转向刨制,并调整产品结构。文中还介绍了有关农药的专利知识及国外新农药的创制情况。 相似文献
56.
Xiaoxiang Hu Changhua Hu Zhaoqiang Wang Huijun Gao 《International journal of systems science》2014,45(8):1740-1756
By utilising Takagi–Sugeno (T–S) fuzzy set approach, this paper addresses the robust H∞ dynamic output feedback control for the non-linear longitudinal model of flexible air-breathing hypersonic vehicles (FAHVs). The flight control of FAHVs is highly challenging due to the unique dynamic characteristics, and the intricate couplings between the engine and fight dynamics and external disturbance. Because of the dynamics’ enormous complexity, currently, only the longitudinal dynamics models of FAHVs have been used for controller design. In this work, T–S fuzzy modelling technique is utilised to approach the non-linear dynamics of FAHVs, then a fuzzy model is developed for the output tracking problem of FAHVs. The fuzzy model contains parameter uncertainties and disturbance, which can approach the non-linear dynamics of FAHVs more exactly. The flexible models of FAHVs are difficult to measure because of the complex dynamics and the strong couplings, thus a full-order dynamic output feedback controller is designed for the fuzzy model. A robust H∞ controller is designed for the obtained closed-loop system. By utilising the Lyapunov functional approach, sufficient solvability conditions for such controllers are established in terms of linear matrix inequalities. Finally, the effectiveness of the proposed T–S fuzzy dynamic output feedback control method is demonstrated by numerical simulations. 相似文献
57.
Bio-cryptography is an emerging security technology which combines cryptography with biometrics. A good bio-cryptosystem is required to protect the privacy of the relevant biometric data as well as achieving high recognition accuracy. Fingerprints have been widely used in bio-cryptosystem design. However, fingerprint uncertainty caused by distortion and rotation during the image capturing process makes it difficult to achieve a high recognition rate in most bio-cryptographic systems. Moreover, most existing bio-cryptosystems rely on the accurate detection of singular points for fingerprint image pre-alignment, which is very hard to achieve, and the image rotation transformation during the alignment process can cause significant singular point deviation and minutiae changes. In this paper, by taking full advantage of local Voronoi neighbor structures (VNSs), e.g. local structural stability and distortion insensitivity, we propose an alignment-free bio-cryptosystem based on fixed-length bit-string representations extracted from modified VNSs, which are rotation- and translation-invariant and distortion robust. The proposed alignment-free bio-cryptosystem is able to provide strong security while achieving good recognition performance. Experimental results in comparison with most existing alignment-free bio-cryptosystems using the publicly-available databases show the validity of the proposed scheme. 相似文献
58.
Liang Xu Xuhai Li Yihang Cui Zhiguo Li Qingyun Chen Chuanmin Meng Haibing Zhang Jianbo Hu Qiang Wu 《Ceramics International》2021,47(15):21008-21012
Ti3SiC2 is of interest due to its unique dual nature reminiscent of both brittle ceramics and ductile metals at ambient conditions. In this work, plate-impact experiments have been performed to study the dynamic behavior of Ti3SiC2 under shock compression up to 112 GPa by using laser velocity interferometer and electric pin techniques. Hugoniot elastic limits (HEL), spall strength, and Hugoniot equations of state have been obtained based on measured particle velocity profiles and shock wave velocities. The ratio of spall strength to HEL for Ti3SiC2 is larger than brittle ceramics but smaller than metals. This result indicates that the dual nature of Ti3SiC2 remains at least up to 10 GPa. On the other hand, the linearity of the Hugoniot equation of state, , suggests that the initial structure of Ti3SiC2 should be stable up to 112 GPa, in contrast to the result reported by Jordan et al. [J. Appl. Phys., 93 (2003) 9639]. 相似文献
59.
0 前言
湖南韶峰水泥集团有限公司规格为φ2.5 m×3.9 m的风扫式煤磨配套的MDC89-7袋式除尘器于1993年投用,经十多年的生产应用,其导流板及风道损坏达80%左右;外壳、主风道因烧袋和腐蚀,严重变形且花板变得很薄;反吹风道变形穿孔,提升阀密封不严,导致清灰时风量流失严重,运行阻力增加,系统产量降低,且系统中含氧量增加,带来安全隐患;除尘效率下降、污染严重,粉尘排放浓度高达1 g/m3;系统能耗高,且维修强度大(每个滤袋重50kg,每次换袋需12人)且费用高.为此,该公司于2004年4月对该煤磨除尘器进行技术改造,取得了明显的效果. 相似文献
60.
循环结构是C语言程序设计中的重难点,其掌握情况对于后续章节的学习效果尤为关键。本文以什么是循环、何时需要使用循环以及如何使用循环三个问题为主线,通过精心选择的教学案例和灵活有效的教学方法来进行解答,以激发学生兴趣,培养编程思想。 相似文献