全文获取类型
收费全文 | 12184篇 |
免费 | 1774篇 |
国内免费 | 862篇 |
专业分类
电工技术 | 410篇 |
综合类 | 761篇 |
化学工业 | 2422篇 |
金属工艺 | 827篇 |
机械仪表 | 188篇 |
建筑科学 | 887篇 |
矿业工程 | 2780篇 |
能源动力 | 403篇 |
轻工业 | 383篇 |
水利工程 | 169篇 |
石油天然气 | 327篇 |
武器工业 | 675篇 |
无线电 | 122篇 |
一般工业技术 | 1168篇 |
冶金工业 | 2474篇 |
原子能技术 | 561篇 |
自动化技术 | 263篇 |
出版年
2024年 | 65篇 |
2023年 | 196篇 |
2022年 | 501篇 |
2021年 | 481篇 |
2020年 | 421篇 |
2019年 | 363篇 |
2018年 | 326篇 |
2017年 | 499篇 |
2016年 | 549篇 |
2015年 | 491篇 |
2014年 | 797篇 |
2013年 | 822篇 |
2012年 | 924篇 |
2011年 | 963篇 |
2010年 | 764篇 |
2009年 | 693篇 |
2008年 | 587篇 |
2007年 | 723篇 |
2006年 | 660篇 |
2005年 | 570篇 |
2004年 | 465篇 |
2003年 | 467篇 |
2002年 | 362篇 |
2001年 | 329篇 |
2000年 | 275篇 |
1999年 | 278篇 |
1998年 | 212篇 |
1997年 | 155篇 |
1996年 | 131篇 |
1995年 | 115篇 |
1994年 | 97篇 |
1993年 | 106篇 |
1992年 | 71篇 |
1991年 | 79篇 |
1990年 | 59篇 |
1989年 | 57篇 |
1988年 | 39篇 |
1987年 | 44篇 |
1986年 | 31篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 12篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1974年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(94):40099-40115
In order to reveal the mechanism of water fog explosion suppression and research the combined effect of water fog and obstacle on hydrogen/air deflagration, multiple sets of experiments were set up. The results show that the instability of thermal diffusion under lean combustion conditions is the main influencing factor of hydrogen/air flame surface instability, and the existence of water fog will aggravate the hydrogen/air flame surface instability. When obstacle is not considered, 8 μm, 15 μm, 30 μm water fog can significantly reduce the flame velocity and explosion overpressure of hydrogen/air, 45 μm fine water fog plays the opposite role. When considering the relative position of the water fog release position and the obstacle, the 8 μm, 15 μm, 30 μm water fog has almost no suppression effect when released near the obstacle, but a significant suppression effect occur, when using the 45 μm water fog. In the field of theoretical research, the research results not only provide an experimental basis for the fine water fog to reduce the consequences of hydrogen explosion accidents, and the optimal diameter range used by the water fog, but also provide experimental reference for the numerical simulation of hydrogen/air explosion suppression in semi-open space, and promote the development of hydrogen explosion suppression theory. In terms of engineering applications, this study can provide a theoretical basis for the layout of fire fighting equipment in the engine room of nuclear power plants or hydrogen-powered ships. 相似文献
2.
《Ceramics International》2022,48(4):4401-4423
Nano-zirconia has been widely applied due to its excellent physical and chemical properties (e.g., high strength, corrosion resistance, oxygen ion conductivity). Existing preparation methods of nano-zirconia tend to require long reaction time, and the sizes of final particles are large with uneven distributions. Sub-/supercritical hydrothermal synthesis of nanoparticles is favored by researchers owing to controllable reaction process, uniform particle size distribution, good reproducibility, short reaction time, high conversion rate and harmlessness to environment. In this paper, the characteristics and mechanisms of dissolution, crystallization and growth of nano-zirconia during sub-/supercritical hydrothermal synthesis are systematically reviewed. The influences of process and material parameters on the size and purity of particles are analyzed. Then, the reaction mechanism and product phase transition mechanism during hydrothermal synthesis of zirconia are summarized to provide a theoretical reference for the oriented preparation. Finally, the improvement and commercialization of sub-/supercritical hydrothermal synthesis technology are evaluated, and the future research topics are proposed. 相似文献
3.
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
4.
5.
《Planning》2019,(6)
减少手术创伤始终是快速康复的决定性因素,这一点在目前的加速康复外科研究尤其是复杂手术,如妇科肿瘤手术中尚未得到充分重视。尊重学习曲线、全面规划手术方案、总结失利经验、开展前瞻性研究是解决此问题的主要方案。本文着重讨论妇科肿瘤手术创伤对术后加速康复的影响及可能的改进措施。 相似文献
6.
This paper discusses the compressive performance of perforated brick masonry after fire exposure. Compressive strength tests of the mortar, clay perforated brick, and perforated brick masonry specimens were performed in accordance with ISO834 fire tests of different durations. The temperature distribution of the masonry materials and specimens was simulated using the finite element software ABAQUS, with the thermal parameters of masonry materials recommended by European standard Eurocode 6 and related literature. The compressive strength reduction factors of mortar and clay perforated brick exposed to different fire durations were calculated via the layered method suggested by European standard Eurocode 1. In addition, the compressive strength reduction factors after cooldown were obtained from the experimental data of the masonry materials, and by considering further reductions in the compressive strength after cooling from high temperatures. Experimental data of the masonry specimens were compared with the numerical results obtained using the reduction factors proposed in this work. The comparison revealed an overall acceptable approximation. Thus, the method presented in this paper can be used to evaluate the residual capacity of masonry structures after fire. 相似文献
7.
8.
9.
对爆炸效应在淤泥软基工程中的应用问题进行了探讨,并首次提出了爆炸在淤泥软基中的分界应力特征以及排水固结及破坏分区的基本模式。为采用动力加速对淤泥软基工程的处理,提供了试验依据,具有实用价值和指导意义。 相似文献
10.
阴,阳离子聚合物地层内凝胶化改善水驱效果的研究 总被引:9,自引:1,他引:8
研究了一杆阴离子聚合物(Ac530)和一种阳离子聚合物(Mb581)在水溶液中形成凝胶的条件和过程、凝胶化学结构、形态、稳定性和力学性能。在模拟地层的二维微观模型内观测了两种聚合物驱替渗流、相逼、形成凝胶、凝胶封堵大孔道的机理。在亲水填砂模型内测定了阴、阳离子聚合物凝胶体系降低渗透率的能力。 相似文献