全文获取类型
收费全文 | 34733篇 |
免费 | 3107篇 |
国内免费 | 1578篇 |
专业分类
电工技术 | 1088篇 |
技术理论 | 5篇 |
综合类 | 2076篇 |
化学工业 | 12928篇 |
金属工艺 | 1542篇 |
机械仪表 | 974篇 |
建筑科学 | 2985篇 |
矿业工程 | 951篇 |
能源动力 | 1091篇 |
轻工业 | 6058篇 |
水利工程 | 646篇 |
石油天然气 | 1462篇 |
武器工业 | 173篇 |
无线电 | 1620篇 |
一般工业技术 | 3373篇 |
冶金工业 | 1248篇 |
原子能技术 | 334篇 |
自动化技术 | 864篇 |
出版年
2024年 | 190篇 |
2023年 | 502篇 |
2022年 | 770篇 |
2021年 | 1039篇 |
2020年 | 1095篇 |
2019年 | 934篇 |
2018年 | 870篇 |
2017年 | 1029篇 |
2016年 | 1140篇 |
2015年 | 1188篇 |
2014年 | 2196篇 |
2013年 | 2169篇 |
2012年 | 2625篇 |
2011年 | 2574篇 |
2010年 | 1934篇 |
2009年 | 1937篇 |
2008年 | 1516篇 |
2007年 | 2164篇 |
2006年 | 1964篇 |
2005年 | 1737篇 |
2004年 | 1513篇 |
2003年 | 1398篇 |
2002年 | 1166篇 |
2001年 | 952篇 |
2000年 | 880篇 |
1999年 | 657篇 |
1998年 | 544篇 |
1997年 | 465篇 |
1996年 | 428篇 |
1995年 | 354篇 |
1994年 | 300篇 |
1993年 | 201篇 |
1992年 | 185篇 |
1991年 | 124篇 |
1990年 | 114篇 |
1989年 | 88篇 |
1988年 | 64篇 |
1987年 | 61篇 |
1986年 | 56篇 |
1985年 | 57篇 |
1984年 | 49篇 |
1983年 | 36篇 |
1982年 | 68篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1978年 | 5篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Textured surface is commonly used to enhance the efficiency of silicon solar cells by reducing the overall reflectance and improving the light scattering. In this study, a comparison between isotropic and anisotropic etching methods was investigated. The deep funnel shaped structures with high aspect ratio are proposed for better light trapping with low reflectance in crystalline silicon solar cells. The anisotropic metal assisted chemical etching (MACE) was used to form the funnel shaped structures with various aspect ratios. The funnel shaped structures showed an average reflectance of 14.75% while it was 15.77% for the pillar shaped structures. The average reflectance was further reduced to 9.49% using deep funnel shaped structures with an aspect ratio of 1:1.18. The deep funnel shaped structures with high aspect ratios can be employed for high performance of crystalline silicon solar cells. 相似文献
2.
G Garrote J
M Cruz H Domínguez J
C Paraj 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(4):392-398
Non‐isothermal processing of lignocellulosic materials in aqueous media (autohydrolysis reaction) under mild conditions leads to solutions containing valuable chemicals (oligosaccharides, sugars and acetic acid) and other, undesired, compounds (belonging to the extractive and acid‐soluble lignin fractions) which have to be removed in further purification treatments. Liquors obtained by non‐isothermal autohydrolysis of Eucalyptus globulus wood and corncobs under a variety of operational conditions were extracted with ethyl acetate in order to remove non‐saccharide components, and the suitability of the fraction dissolved in the organic phase was assayed for possible utilisation as an antioxidant. The yield and antioxidant activity of ethyl acetate extracts (measured by the α,α‐diphenyl‐β‐picrylhydrazyl (DPPH) radical scavenging capacity) showed a strong dependence on the autohydrolysis conditions. The antioxidant activity of extracts obtained under selected operational conditions compared well with synthetic antioxidants. © 2003 Society of Chemical Industry 相似文献
3.
试论循环水装置的经济性及其成本分析 总被引:2,自引:1,他引:1
通过对循环水装置的投资和成本分析,阐述了建设该装置的经济性和社会意义。 相似文献
4.
Preparation and properties of nano-sized SnO2 powder 总被引:2,自引:0,他引:2
1 INTRODUCTIONSnO2isoneofthemainmaterialsusedingassensor.Becauseofthehumidityandgassensingfunction,itattractsmoreandmoreattentions.Butthepresentproblemishowtoimprovethestabilityandsensibilityofgassensor.Researchershavetakenmanymeasurestoresolvethisproble… 相似文献
5.
超细Fe3O4粒子表面包覆酞菁钴性质研究 总被引:3,自引:1,他引:2
本文研究了合成载氧体的金属有机化学液相淀积法制造工艺,所得产物经TEM、XPS、Moss-bauer谱和B-H仪等手段,研究了它的结构和磁性能。实验表明,酞青钴以薄层形式包覆在Fe_3O_4的表面,封闭了Fe_3O_4的表面孔洞,稳定了Fe_3O_4的物相,增强了磁性能。 相似文献
6.
7.
8.
在KZON-50/120空分设备的安装调试和试运行过程中,对其机械和电器部分进行了多处改造,克服了原设计中存在的不足之处。改造后,机械和电器性能更加趋于合理,操作简单,便于维护,降低了制气费用,提高了制气纯度和经济效益,保证了空分设备更加安全可靠运行。 相似文献
9.
Ana MRB Xavier Ana Paula M Tavares Margarida SM Agapito Dmitry V Evtuguin 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(12):1602-1608
BACKGROUND: A sequential batch reactor (SBR) was used for eucalypt kraft pulp effluent treatment with Trametes versicolor. A 23 full factorial design and response surface methodology were applied to optimise the batch fermentation conditions. Effluent concentration, culture medium and inoculum age were the factors selected for this study in order to optimise the reduction of chemical oxygen demand (COD). RESULTS: The presence of Trametes Defined Medium (TDM) in the fermentation was required to obtain a significant COD reduction. Experiments in the batch reactor confirmed, in general, the predicted results of optimisation developed from Erlenmeyer batch assays. The T. versicolor culture remained active during 42 days of study in the SBR, providing approximately 80% of COD reduction. CONCLUSION: Trametes versicolor may be considered as very promising for the biological treatment of effluents from kraft pulp mills in an SBR system instead of the activated sludge mixed cultures traditionally used. Copyright © 2008 Society of Chemical Industry 相似文献
10.
This study describes a laboratory method for the estimation of emission from preservative-treated wood in the different situations where emissions could enter the environment for use classes 3 (not in contact with ground) and 4 and 5 (in contact with the ground, fresh water or sea water) according to OECD Guidelines. Samples of scotch pine sapwood (Pinus sylvestris L.) were treated with CCA (1% and 2%), ACQ-1900 (3% and 7%), ACQ-2200 (2%), Tanalith E 3491 (2% and 2.8%), and Wolmanit CX-8 (2%). 相似文献