全文获取类型
收费全文 | 24416篇 |
免费 | 1068篇 |
国内免费 | 417篇 |
专业分类
电工技术 | 1955篇 |
技术理论 | 2篇 |
综合类 | 1821篇 |
化学工业 | 2639篇 |
金属工艺 | 838篇 |
机械仪表 | 1145篇 |
建筑科学 | 5282篇 |
矿业工程 | 1797篇 |
能源动力 | 967篇 |
轻工业 | 1062篇 |
水利工程 | 1507篇 |
石油天然气 | 1117篇 |
武器工业 | 58篇 |
无线电 | 593篇 |
一般工业技术 | 1122篇 |
冶金工业 | 2351篇 |
原子能技术 | 87篇 |
自动化技术 | 1558篇 |
出版年
2024年 | 42篇 |
2023年 | 127篇 |
2022年 | 383篇 |
2021年 | 456篇 |
2020年 | 524篇 |
2019年 | 294篇 |
2018年 | 301篇 |
2017年 | 334篇 |
2016年 | 502篇 |
2015年 | 583篇 |
2014年 | 2345篇 |
2013年 | 1446篇 |
2012年 | 2062篇 |
2011年 | 2258篇 |
2010年 | 1836篇 |
2009年 | 1652篇 |
2008年 | 1251篇 |
2007年 | 1575篇 |
2006年 | 1389篇 |
2005年 | 1205篇 |
2004年 | 1056篇 |
2003年 | 948篇 |
2002年 | 772篇 |
2001年 | 630篇 |
2000年 | 507篇 |
1999年 | 337篇 |
1998年 | 253篇 |
1997年 | 214篇 |
1996年 | 151篇 |
1995年 | 94篇 |
1994年 | 83篇 |
1993年 | 37篇 |
1992年 | 53篇 |
1991年 | 32篇 |
1990年 | 23篇 |
1989年 | 18篇 |
1988年 | 20篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1983年 | 6篇 |
1979年 | 7篇 |
1964年 | 6篇 |
1963年 | 4篇 |
1962年 | 4篇 |
1960年 | 5篇 |
1958年 | 6篇 |
1957年 | 5篇 |
1956年 | 4篇 |
1954年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
Chunsheng Wang Yishuang Wang Mingqiang Chen Defang Liang Zhonglian Yang Wen Cheng Zhiyuan Tang Jun Wang Han Zhang 《International Journal of Hydrogen Energy》2021,46(7):5852-5874
Given the continuing issues of environment and energy, methane dry reforming for syngas production have sparked interest among researchers, but struggled with the process immaturity owing to catalyst deactivation. This review summarizes the recent advances in the development of efficient and stable catalysts with strong resistance to coking and metal sintering, including the application of novel materials, the assessment of advanced characterizations and the compatibility to improved reaction system. One feasible option is the crystalline oxide catalysts (perovskite, pyrochlore, spinel and LDHs), which feature a fine metal dispersion and surface confinement effect via a metal exsolution strategy and exhibit superior reactivity and stability. Some new materials (h-BN, clays and MOFs) also extend the option because of their unique morphology and microstructure. It also is elaborated that progresses were achieved in advanced characterizations application, leading to success in the establishment of reaction mechanisms and attributions to the formed robust catalysts. In addition, the perspective described the upgrade of reaction system to a higher reaction efficiency and milder reaction conditions. The combination of efficient reaction systems and robust catalysts paves a way for a scaling-up application of the process. 相似文献
2.
《Ceramics International》2022,48(6):7593-7604
The ceramic core, produced by hot injection molding, is one of the critical components for manufacturing high-performance aircraft engine turbine blades. However, the injection molding process will cause defects such as burrs and flashes in the fine structure of the formed ceramic core. Manual trimming is necessary, but the trimming quality is poor, and the yield is low. In this paper, the online trimming method of ceramic cores is studied. Based on the orthogonal experiment method, the optimal laser parameters for processing the ceramic core's porous multi-scale particle structure material were obtained. Further, the problems of the match head and tail phenomenon and dimensional accuracy improvement in trimming ceramic cores have been studied. A path optimisation method is proposed to improve the quality and accuracy of the trimming profile effectively. Finally, the overall process flow of ceramic core trimming is elaborated, and experimental verification is given. The results show that the ceramic core online trimming method proposed in this paper has advantages of high precision and high yield compared with the manual method, which will have substantial potential application value in the aviation field. 相似文献
3.
文章通过对黑龙江省高效节水现状,存在问题的分析,结合黑龙江省高效节水发展的支撑能力,阐述黑龙江省节水增粮目标、任务及总体布局,为黑龙江省2012—2015年节水增粮实施提供依据。 相似文献
4.
5.
Typhoon Aere in 2004 induced severe sedimentation and loss of storage capacity of the Shihmen Reservoir in northern Taiwan. The resulting dramatic increase in the turbidity of the water seriously affected the water supply. To effectively maintain the stability of the water supply and maintain the reservoir’s storage capacity, the government of Taiwan began to plan and construct a series of improvement measures, such as a sediment flushing tunnel, the JhongJhuang Bank-Side Reservoir, and the Amuping Desilting Tunnel. However, previous studies only focused on the impact of the sediment flushing tunnel and the Amuping Desilting Tunnel on the downstream riverbed, and did not consider the possibility of increasing sediment discharge after the completion of the JhongJhuang Bank-Side Reservoir. In addition, climate change will cause the intensity of extreme rainfall to increase enormously in the future. That rainfall and extra sediment flushing will challenge the existing flood prevention facilities. Therefore, this study considered that the JhongJhuang Bank-Side Reservoir will increase sediment discharge of the Shihmen Reservoir, and used dynamical downscaling extreme typhoon data of climate change under the RCP 8.5 scenario to explore the flood prevention and riverbed migration of the main channels of the Dahan and Tamsui Rivers in the future. We used the rainfall–runoff model of Hydrologic Modeling System to simulate rainfall and runoff, and used the hydraulic and sediment transport model of CCHE1D to holistically simulate flood events and consequent river scouring and deposition behaviors. Our results showed that the projected peak discharge during the late 21st century (2075 to 2099) will be at least 50% higher than that during the baseline (1979 to 2003) period. In terms of flood prevention, the potential of overbank flooding will increase in the downstream area, and the trend of long-term change in the riverbed will be dominated by degradation (-0.489 ± 0.743 m) in the future. The improvement measures will have a limited impact on riverbed migration (0.011 ± 0.094 m) in the Dahan and Tamsui Rivers. After the operation of the JhongJhuang Bank-Side Reservoir, the Shihmen Reservoir is expected to increase the sediment discharge ratio by 70% during floods, and it will not cause excessive water turbidity that may affect downstream water supply. 相似文献
6.
7.
《Energy Policy》2015
In this paper we construct an indirect measure of the supply marginal cost function for the main generators from the observed bid data in the Italian electricity market in the period 2004–2007. We compute the residual demand function for each generator, taking explicitly into account the issue of transmission line congestion. This procedure allows recovering correct zonal Lerner index and the implied measure of the marginal cost function. We find evidence of a stable U-shaped marginal cost function for three main Italian generators, but a flat function for ENEL, the former national monopolist. The policy relevance of our approach lies in the possibility to offer some empirical knowledge of the marginal cost function of each generator to the regulator to design appropriate policy measures geared to the promotion of competitive market conditions. We propose a new market surveillance mechanism, which is based on the principle of sanctioning excessive deviations from the estimated measure of the marginal cost function presented in this work. 相似文献
8.
刘家山排土场为民采排弃形成,已经出现大规模滑坡。为了保证上下游生产生活设施的安全,依据现场实际情况,结合现场调查,提出了削坡处理的方案。经过治理后,刘家山排土场平稳地渡过了雨季,目前处于稳定状态,达到了治理目的。 相似文献
9.
Dujuan Li Wei Yan Ronghui Qi Li-Zhi Zhang 《International Journal of Hydrogen Energy》2021,46(14):9267-9279
PEM-based electrolytic air dehumidification is innovative in dehumidification that requires high precision and small space due to its high efficiency, compactness, and cleanness. However, the system dehumidification performance and durability are limited by using commercial Anatase-IrO2 catalysts. In this study, two types of structurally modified OER catalyst materials, ATO-IrO2 and ND-MnO2-IrO2, are developed to improve the performance of the system. System experiments showed that, compared to the commercial catalysts, the use of ATO-IrO2 and ND-MnO2-IrO2 as the anode catalyst can improve the dehumidification performance by 45% and 20%, respectively. Furthermore, in 50-h accelerated aging tests, the attenuation rates of the ATO-IrO2 and ND-MnO2-IrO2 systems are 3% and 8% respectively, which are far lower than the 35% attenuation of commercial catalyst. The results indicate that, as catalysts with a classic core-shell structure, ATO-IrO2 and ND-MnO2-IrO2 still have a significant impact on improving the performance of the electrolytic dehumidification systems. 相似文献
10.