全文获取类型
收费全文 | 22205篇 |
免费 | 1657篇 |
国内免费 | 945篇 |
专业分类
电工技术 | 1770篇 |
技术理论 | 1篇 |
综合类 | 2156篇 |
化学工业 | 2519篇 |
金属工艺 | 1586篇 |
机械仪表 | 1140篇 |
建筑科学 | 3964篇 |
矿业工程 | 504篇 |
能源动力 | 2562篇 |
轻工业 | 1423篇 |
水利工程 | 352篇 |
石油天然气 | 831篇 |
武器工业 | 176篇 |
无线电 | 802篇 |
一般工业技术 | 1801篇 |
冶金工业 | 1787篇 |
原子能技术 | 486篇 |
自动化技术 | 947篇 |
出版年
2024年 | 84篇 |
2023年 | 275篇 |
2022年 | 513篇 |
2021年 | 606篇 |
2020年 | 660篇 |
2019年 | 500篇 |
2018年 | 479篇 |
2017年 | 595篇 |
2016年 | 655篇 |
2015年 | 722篇 |
2014年 | 1307篇 |
2013年 | 1320篇 |
2012年 | 1443篇 |
2011年 | 1604篇 |
2010年 | 1243篇 |
2009年 | 1193篇 |
2008年 | 1030篇 |
2007年 | 1368篇 |
2006年 | 1298篇 |
2005年 | 1188篇 |
2004年 | 1018篇 |
2003年 | 936篇 |
2002年 | 883篇 |
2001年 | 755篇 |
2000年 | 574篇 |
1999年 | 486篇 |
1998年 | 371篇 |
1997年 | 334篇 |
1996年 | 254篇 |
1995年 | 221篇 |
1994年 | 139篇 |
1993年 | 141篇 |
1992年 | 126篇 |
1991年 | 104篇 |
1990年 | 86篇 |
1989年 | 52篇 |
1988年 | 43篇 |
1987年 | 37篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1984年 | 23篇 |
1983年 | 22篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1959年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
通过各种试验手段,研究了20Mn2SiVB钢不同奥氏体化温度及不同冷却方式处理后其显微组织及其强度和塑性的变化,确定了最佳的热处理工艺。结果表明:900℃奥氏体化后风冷时钢的强塑性最好;在强塑性最佳时的微观组织是铁素体+粒状贝氏体。 相似文献
22.
In shape memory materials,that have been trained to have a two way shape memory effect(TWSM),themartensitic variants are classified into two groups,i.e.,preferentially oriented variants and self-accommodatingvariants.Applied stress may promote or constrain the transition of preferentially oriented variants and so changetransformation temperatures but has no essential effect on self-accommodating variants.According to the pointof view mentioned above,some experimental phenomena during thermocycling of a TWSM device may be ex-plained,such as the absence of synchronization between the plot of resistance change.temperature and the plotof memory strain vs.temperature. 相似文献
23.
Chuanming Tian Bin Li Yichuan Rui Hao Xiong Yu Zhao Xuefei Han Xinliang Zhou Yu Qiu Wei An Kerui Li Chengyi Hou Yaogang Li Hongzhi Wang Qinghong Zhang 《Advanced functional materials》2023,33(41):2302270
Despite the outstanding power conversion efficiency (PCE) of perovskite solar cells (PSCs) achieved over the years, unsatisfactory stability and lead toxicity remain obstacles that limit their competitiveness and large-scale practical deployment. In this study, in situ polymerizing internal encapsulation (IPIE) is developed as a holistic approach to overcome these challenges. The uniform polymer internal package layer constructed by thermally triggered cross-linkable monomers not only solidifies the ionic perovskite crystalline by strong electron-withdrawing/donating chemical sites, but also acts as a water penetration and ion migration barrier to prolong shelf life under harsh environments. The optimized MAPbI3 and FAPbI3 devices with IPIE treatment yield impressive efficiencies of 22.29% and 24.12%, respectively, accompanied by remarkably enhanced environmental and mechanical stabilities. In addition, toxic water-soluble lead leakage is minimized by the synergetic effect of the physical encapsulation wall and chemical chelation conferred by the IPIE. Hence, this strategy provides a feasible route for preparing efficient, stable, and eco-friendly PSCs. 相似文献
24.
This article proposes an approach for reconstructing physical parameters of a sample in a rectangular resonator during microwave radiation, knowing a priori, its electric field distribution. The inverse problem was solved using two global optimization algorithms and the peak signal-to-noise ratio (PSNR) criterion. First, the Self-regulated Fretwidth Harmony Search algorithm (SFHS) identified suitable resonant frequencies for a given configuration. Next, the unified Particle Swarm Optimization (UPSO) optimized said configuration. Together, they became a maximization strategy of the PSNR through a dual optimization process. Results showed the ability of the approach for estimating the height of each sample block and the resonating frequency of the cavity. This process takes longer to finish as a higher PSNR is demanded (mainly due to the aforementioned dual optimization). Even so, it allows for more similar electric field distributions between both, the direct and inverse problems. 相似文献
25.
26.
27.
介绍了将已停用但仍完好的内燃式热风炉炉体经过改造,增加上料、出料及必要的烧制设备等,利用高炉富余的煤气,改造成煤气烧。实践证明,改造后的石灰窑经济效益显著。 相似文献
28.
吴建国 《冶金标准化与质量》2006,44(4):28-29
介绍了唐山钢铁集团有限公司建的国内第一条感应加热高强度包装钢带生产线主要设备及技术工艺特点。 相似文献
29.
基于模糊神经网络的感应加热电源温度控制 总被引:1,自引:0,他引:1
通过对原有感应加热电源温度控制方法的分析,提出了一种适合于非线性系统基于模糊神经网络的温度控制方法,并介绍了该系统的组成及实现方法。 相似文献
30.
Despite anecdotal evidence suggesting that air travel is personally demanding, little research has examined air travel stress. To address these issues, the author developed and evaluated the 1st known measure of air travel stress--the Air Travel Stress Scale--in 3 studies. Exploratory and confirmatory factor analysis indicated 3 components: (a) anxious reactions to adverse air travel events, (b) angry reactions to other passengers as well as an antecedent of air travel stress, and (c) the lack of trust that the airlines/airports will ensure one's comfort and safety. Each component had good internal reliability and test-retest reliability over a 6- to 7-week interval. Each component showed evidence for discriminant and convergent validity. Implications for research into understanding and intervening on air travel stress are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献