全文获取类型
收费全文 | 16901篇 |
免费 | 1960篇 |
国内免费 | 812篇 |
专业分类
电工技术 | 162篇 |
综合类 | 588篇 |
化学工业 | 7255篇 |
金属工艺 | 801篇 |
机械仪表 | 221篇 |
建筑科学 | 403篇 |
矿业工程 | 98篇 |
能源动力 | 334篇 |
轻工业 | 4968篇 |
水利工程 | 33篇 |
石油天然气 | 781篇 |
武器工业 | 510篇 |
无线电 | 656篇 |
一般工业技术 | 2164篇 |
冶金工业 | 342篇 |
原子能技术 | 162篇 |
自动化技术 | 195篇 |
出版年
2024年 | 151篇 |
2023年 | 444篇 |
2022年 | 587篇 |
2021年 | 773篇 |
2020年 | 744篇 |
2019年 | 769篇 |
2018年 | 714篇 |
2017年 | 855篇 |
2016年 | 847篇 |
2015年 | 743篇 |
2014年 | 923篇 |
2013年 | 1232篇 |
2012年 | 1179篇 |
2011年 | 1365篇 |
2010年 | 887篇 |
2009年 | 986篇 |
2008年 | 886篇 |
2007年 | 853篇 |
2006年 | 753篇 |
2005年 | 549篇 |
2004年 | 496篇 |
2003年 | 481篇 |
2002年 | 433篇 |
2001年 | 272篇 |
2000年 | 243篇 |
1999年 | 181篇 |
1998年 | 217篇 |
1997年 | 171篇 |
1996年 | 125篇 |
1995年 | 115篇 |
1994年 | 92篇 |
1993年 | 82篇 |
1992年 | 70篇 |
1991年 | 76篇 |
1990年 | 62篇 |
1989年 | 36篇 |
1988年 | 30篇 |
1987年 | 28篇 |
1986年 | 18篇 |
1985年 | 28篇 |
1984年 | 44篇 |
1983年 | 19篇 |
1982年 | 37篇 |
1980年 | 23篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1975年 | 10篇 |
1974年 | 5篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Use of the Retarded Solution-Reprecipitation Process to Attain a Higher Initial Permeability in MnZn Ferrites 总被引:1,自引:0,他引:1
Miha Drofenik rej nidari Darko Makovec 《Journal of the American Ceramic Society》2003,86(9):1601-1604
We investigated the effect of various amounts of liquid phase on microstructure development during sintering and the resulting magnetic permeability of MnZn ferrite (MZF) samples. Our results revealed that the microstructure and the final magnetic permeability depend on the thickness of the liquid-phase film during sintering. The solution-reprecipitation (S-R) process, which is associated with an intensive microstructure development in MZF, starts when a continuous liquid-phase film of critical thickness δo , which wets the MZF grains, is formed. The solid-state sintering that takes place before the formation of the continuous liquid-phase film is essential for the final microstructure of MZF. 相似文献
2.
本文运用一典型的人工神经网络模型─“反向传播”模型,对高氧化态(Ⅱ─Ⅳ)三核金属簇合物的构型分布进行了分析,得到了较好的分类、预报结果为化合物结构分析提供了新的工具。 相似文献
3.
ABSTRACT: The traditional small-scale production of boucané, a cured smoked pork-belly product from Réunion, involves several unit operations that are performed in a single step. The aim of this study was to highligh the impact of 4 unit operations (salting, drying, cooking, and smoking) on stability, color, and flavor development in processed pork. These characateristics are the 3 main criteria of boucané's quality. Mass transfer, color, and volatile compounds were measured, analyzed, and compared in 4 products. Results indicated that a major quantity of volatile compounds detected in the processed meat were derived from the smoking process. Color variations were mainly explained by muscle pigment modification due to the cooking process, and by the input of volatile compounds of smoke. 相似文献
4.
LiFePO4 is a potential candidate for the cathode material of the lithium secondary batteries. A co-precipitation method was adopted to prepare LiFePO4 because it is simple and cheap. Nitrogen gas was needed to prevent oxidation of Fe2+ in the aqueous solution. The co-precipitated precursor shows the high reactivity with the reductive gas, and the single phase of LiFePO4 is successfully synthesized with the aid of carbon under less reductive conditions. LiFePO4 fine powder prepared by co-precipitation method shows high rate capability, impressive specific capacity and cycle property. 相似文献
5.
P. M. Solozhenkin E. A. Deliyanni V. N. Bakoyannakis A. I. Zouboulis K. A. Matis 《Journal of Mining Science》2003,39(3):287-296
The original method is developed for producing the new inorganic sorption material of akaganeite bgr-FeO(OH). The material in question is characterized relative to arsenic contained in aqua. The possibility is established for removing arsenate ions from water by contemporary physicochemical methods. 相似文献
6.
7.
Jean‐Marc Aldric Philippe Thonart 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1401-1408
BACKGROUND: In the framework of biological processes used for waste gas treatment, the impact of the inoculum size on the start‐up performance needs to be better evaluated. Moreover, only a few studies have investigated the behaviour of elimination capacity and biomass viability in a two‐phase partitioning bioreactor (TPPB) used for waste gas treatment. Lastly, the impact of ethanol as a co‐substrate remains misunderstood. RESULTS: Firstly, no benefit of inoculation with a high cellular density (>1.5 g L?1) was observed in terms of start‐up performance. Secondly, the TPPB was monitored for 38 days to characterise its behaviour under several operational conditions. The removal efficiency remained above 63% for an inlet concentration of 7 g isopropylbenzene (IPB) m?3 and at some time points reached 92% during an intermittent loading phase (10 h day?1), corresponding to a mean elimination capacity of 4 × 10?3 g L?1 min?1 (240 g m?3 h?1) for a mean IPB inlet load of 6.19 × 10?3 g L?1 min?1 (390 g m?3 h?1). Under continuous IPB loading, the performance of the TPPB declined, but the period of biomass acclimatisation to this operational condition was shorter than 5 days. The biomass grew to approximately 10 g L?1 but the cellular viability changed greatly during the experiment, suggesting an endorespiration phenomenon in the bioreactor. It was also shown that simultaneous degradation of IPB and ethanol occurred, suggesting that ethanol improves the biodegradation process without causing oxygen depletion. CONCLUSION: A water/silicone oil TPPB with ethanol as co‐substrate allowed the removal of a high inlet load of IPB during an experiment lasting 38 days. Copyright © 2008 Society of Chemical Industry 相似文献
8.
镁钴铝类水滑石催化合成安息香甲醚 总被引:1,自引:0,他引:1
采用共沉淀法制备了镁钴铝类水滑石化合物(MgCoAl-HTLcs),并用 X 射线衍射、扫描电子显微镜、NH_3程序升温脱附等方法对 MgCoAl-HTLcs 进行了表征,并以 MgCoAl-HTLcs 为催化剂催化苯甲醛与甲醇反应合成安息香甲醚,研究了n(Mg):n(Co):n(Al)、催化剂用量、原料配比、反应温度、反应时间对合成反应的影响。表征结果显示,MgCoAl-HTLcs 的晶相完整,表面主要为弱酸、弱碱性。催化合成安息香甲醚的适宜条件为:MgCoAl-HTLcs 催化剂用量0.10 g(约为原料总质量的0.23%),n(Mg):n(Co):n(Al)=0.4:1.6:1.0,V(苯甲醛):V(甲醇)=3:50,反应温度50℃,反应时间150 min。在此条件下,苯甲醛的平衡转化率达77.49%,安息香甲醚选择性接近100%。为洁净合成安息香甲醚开辟了一条新的途径。 相似文献
9.
《Particulate Science and Technology》2007,25(1):77-89
The removal of particulate contamination is a critical issue for many manufacturing processes. It is particularly critical to the electronics industry in which small pieces of microscopic debris remaining after chemical mechanical planarization (cmp) using submicron polishing particles can cause device failure. One way to enhance particle removal following the cmp process is to utilize surfactants. Recent research has shown ways to model the effect of surfactants on enhanced particle removal. However, previous research has not demonstrated the effect of ionic strength on enhanced particle removal associated with surfactant use. Past research has also not shown the combined effects of ionic strength and surfactant concentration on enhanced particle removal using surfactants. This article summarizes the parameters affecting particle removal, and it provides data and analysis on the effect of ionic strength as well as the combined effects of ionic strength and surfactant concentration on particle removal following cmp processing. 相似文献
10.
Mg-Si基热电化合物的研究现状 总被引:1,自引:0,他引:1
重点综述了Mg-Si基热电化合物的基本特性,该体系热电材料的制备方法与掺杂改性的研究进展,并提出了要重点解决的问题。 相似文献