全文获取类型
收费全文 | 12727篇 |
免费 | 1801篇 |
国内免费 | 1058篇 |
专业分类
电工技术 | 537篇 |
技术理论 | 2篇 |
综合类 | 1163篇 |
化学工业 | 1300篇 |
金属工艺 | 863篇 |
机械仪表 | 506篇 |
建筑科学 | 1253篇 |
矿业工程 | 779篇 |
能源动力 | 314篇 |
轻工业 | 787篇 |
水利工程 | 412篇 |
石油天然气 | 250篇 |
武器工业 | 80篇 |
无线电 | 1785篇 |
一般工业技术 | 1244篇 |
冶金工业 | 770篇 |
原子能技术 | 101篇 |
自动化技术 | 3440篇 |
出版年
2024年 | 30篇 |
2023年 | 244篇 |
2022年 | 373篇 |
2021年 | 424篇 |
2020年 | 518篇 |
2019年 | 382篇 |
2018年 | 364篇 |
2017年 | 383篇 |
2016年 | 432篇 |
2015年 | 511篇 |
2014年 | 911篇 |
2013年 | 1025篇 |
2012年 | 1024篇 |
2011年 | 1100篇 |
2010年 | 859篇 |
2009年 | 847篇 |
2008年 | 802篇 |
2007年 | 928篇 |
2006年 | 825篇 |
2005年 | 672篇 |
2004年 | 591篇 |
2003年 | 423篇 |
2002年 | 374篇 |
2001年 | 268篇 |
2000年 | 216篇 |
1999年 | 194篇 |
1998年 | 154篇 |
1997年 | 107篇 |
1996年 | 91篇 |
1995年 | 79篇 |
1994年 | 53篇 |
1993年 | 59篇 |
1992年 | 58篇 |
1991年 | 48篇 |
1990年 | 48篇 |
1989年 | 31篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 33篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 7篇 |
1964年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
本文针对乘用车内部凸出物的法规要求对车载空调控制器的旋钮按键溃缩进行了研究和设计,描述了这种新型旋钮按键溃缩设计相对于目前常用的方案在成本、空间、可靠性等方面的优势。根据实际设计结果表明,本文所应用的新型旋钮按键溃缩设计能在成本与空间有限的情况下可靠的满足法规对乘用车内部凸出物的要求,为乘用车内部凸出物溃缩方案提供了新方向,值得我们推广应用。 相似文献
42.
43.
Private information retrieval(PIR) is an important privacy protection issue of secure multi-party computation, but the PIR protocols based on classical cryptography are vulnerable because of new technologies,such as quantum computing and cloud computing. The quantum private queries(QPQ) protocols available, however, has a high complexity and is inefficient in the face of large database. This paper, based on the QKD technology which is mature now, proposes a novel QPQ protocol utilizing the key dilution and auxiliary parameter. Only N quits are required to be sent in the quantum channel to generate the raw key, then the straight k bits in the raw key are added bitwise to dilute the raw key, and a final key is consequently obtained to encrypt the database. By flexible adjusting of auxiliary parameters θ and k, privacy is secured and the query success ratio is improved. Feasibility and performance analyses indicate that the protocol has a high success ratio in first-trial query and is easy to implement, and that the communication complexity of O(N) is achieved. 相似文献
44.
Dry sliding wear tests were performed for Ti–6Al–4V alloy on a pin-on-disc wear tester. The wear behavior of Ti–6Al–4V alloy at sliding velocities of 0.5–4 m/s was studied and the tribo-oxides and their function were explored. Ti–6Al–4V alloy presented a marked variation of wear rate as a function of velocity. With the rise and fall of wear rate, Ti–6Al–4V alloy underwent the transitions of wear mechanisms from the combination of delamination wear and oxidative wear at lower speeds to delamination wear at 2.68 m/s, and then to oxidative wear at 4 m/s. These phenomena were attributed to the appearance and disappearance of tribo-oxides. In spite of trace or a small amount, tribo-oxides would change the wear behavior, and even wear mechanism. 相似文献
45.
46.
蔬菜是人们餐桌上必不可少的食物,重金属在受污染的自然环境中又无处不在,而蔬菜中的重金属含量尤其令人担忧。本文使用原子吸收分光光度法(石墨炉)和原子荧光分光光度法检测了广州市郊某垃圾填埋场附近所种植蔬菜中重金属含量。结果:抽样由2013年10月至2014年9月共持续一年,共抽样检测12次,按平均每个月一次的频率,检测结果并未发现有蔬菜超出国家规定的限量值。 相似文献
47.
48.
This investigation examined various kinetic and equilibrium models for gold (Au) and silver (Ag) adsorption from cyanide leach solution, onto surface of granular activated carbon (GAC) with 10, 35, 70 and 100% activities. Results indicated that the initial rate for Au and Ag adsorption is similar and increases by increasing the GAC activities. Outcomes showed that the adsorption for low activity GAC is proportional to the number of adsorption sites while the rate-limiting can be chemisorption for GAC with high activity. Thus, even low amount of contaminations on the fresh GAC can significantly decrease the capacity of precious metals adsorption. 相似文献
49.
《中国有色金属学会会刊》2020,30(7):1943-1955
Physicochemical properties of arsenic sulfide sludge (ASS) from copper smelter (ASS-I) and lead−zinc smelter (ASS-II) were examined by XRD, Raman spectroscopy, SEM−EDS, TG−DTA, XPS and chemical phase analysis method. The toxicity characteristic leaching procedure (TCLP), Chinese standard leaching tests (CSLT), three-stage sequential extraction procedure (BCR) and batch leaching experiments (BLE) were used to investigate the environmental stability. The ASSs from different smelters had obviously different physicochemical and environmental properties. The phase composition and micrograph analysis indicate that ASS-I mainly consists of super refined flocculent particles including amorphous arsenic sulfide adhered with amorphous sulfur and that ASS-II mainly consists of amorphous arsenic sulfide. The valence state of arsenic in both sludges is trivalent, but the valence composition of sulfur is quite different. The ASSs have thermal instability properties. The results of TCLP and CSLT indicate that the concentrations of As and Pd in the leaching solution exceed the standard limits. More than 5% and 90% of arsenic are in the form of acid soluble and oxidizable fractions, respectively, which explains the high arsenic leaching toxicity and environmental activity of ASS. This research provides comprehensive information for the disposal of ASS from copper and lead−zinc smelter. 相似文献
50.
《中国有色金属学会会刊》2020,30(9):2293-2310
Understanding the nature of liquid structures and properties has always been a hot field in condensed matter physics and metallic materials science. The liquid is not homogeneous and the local structures inside change discontinuously with temperature, pressure, etc. The liquid will experience liquid−liquid structure transition under a certain condition. Liquid−liquid structure transition widely exists in many metals and alloys and plays an important role in the final microstructure and the properties of the solid alloys. This work provides a comprehensive review on this unique structure transition in the metallic liquid together with the recent progress of its impact on the following microstructure and properties after solidification. These effects are discussed by integrating them into different experimental results and theoretical considerations. The application of liquid−liquid structure transition as a strategy to tailor the properties of metals and alloys is proven to be practical and efficient. 相似文献