全文获取类型
收费全文 | 536600篇 |
免费 | 9713篇 |
国内免费 | 2305篇 |
专业分类
电工技术 | 9860篇 |
综合类 | 555篇 |
化学工业 | 79426篇 |
金属工艺 | 19516篇 |
机械仪表 | 16887篇 |
建筑科学 | 14194篇 |
矿业工程 | 1052篇 |
能源动力 | 15196篇 |
轻工业 | 51391篇 |
水利工程 | 3911篇 |
石油天然气 | 2468篇 |
武器工业 | 28篇 |
无线电 | 74749篇 |
一般工业技术 | 100701篇 |
冶金工业 | 101087篇 |
原子能技术 | 7026篇 |
自动化技术 | 50571篇 |
出版年
2022年 | 2616篇 |
2021年 | 4549篇 |
2020年 | 3154篇 |
2019年 | 3870篇 |
2018年 | 5885篇 |
2017年 | 5938篇 |
2016年 | 6499篇 |
2015年 | 5245篇 |
2014年 | 8604篇 |
2013年 | 25770篇 |
2012年 | 14755篇 |
2011年 | 20691篇 |
2010年 | 16018篇 |
2009年 | 18216篇 |
2008年 | 19018篇 |
2007年 | 18936篇 |
2006年 | 17108篇 |
2005年 | 15779篇 |
2004年 | 15166篇 |
2003年 | 14718篇 |
2002年 | 14087篇 |
2001年 | 14183篇 |
2000年 | 13075篇 |
1999年 | 13971篇 |
1998年 | 33513篇 |
1997年 | 23771篇 |
1996年 | 18723篇 |
1995年 | 14197篇 |
1994年 | 12557篇 |
1993年 | 12092篇 |
1992年 | 8697篇 |
1991年 | 8372篇 |
1990年 | 7850篇 |
1989年 | 7451篇 |
1988年 | 7015篇 |
1987年 | 5791篇 |
1986年 | 5758篇 |
1985年 | 6903篇 |
1984年 | 6369篇 |
1983年 | 5502篇 |
1982年 | 5169篇 |
1981年 | 5088篇 |
1980年 | 4748篇 |
1979年 | 4530篇 |
1978年 | 4176篇 |
1977年 | 5097篇 |
1976年 | 7063篇 |
1975年 | 3425篇 |
1974年 | 3283篇 |
1973年 | 3149篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Rajoo R. Lim S.S. Wong E.H. Hnin W.Y. Seah S.K.W. Tay A.A.O. Iyer M. Tummala R.R. 《Advanced Packaging, IEEE Transactions on》2008,31(2):377-385
A wafer level packaging technique has been developed with an inherent advantage of good solder joint co-planarity suitable for wafer level testing. A suitable weak metallization scheme has also been established for the detachment process. During the fabrication process, the compliancy of the solder joint is enhanced through stretching to achieve a small shape factor. Thermal cycling reliability of these hourglass-shaped, stretch solder interconnections has been found to be considerably better than that of the conventional spherical-shaped solder bumps. 相似文献
912.
Effect of Thickness of the p-AlGaN Electron Blocking Layer on the Improvement of ESD Characteristics in GaN-Based LEDs 总被引:1,自引:0,他引:1
Chung-Hsun Jang Sheu J.K. Tsai C.M. Shei S.C. Lai W.C. Chang S.J. 《Photonics Technology Letters, IEEE》2008,20(13):1142-1144
The following letter presents a study regarding GaN-based light-emitting diodes (LEDs) with p-type AlGaN electron blocking layers (EBLs) of different thicknesses. The study revealed that the LEDs could endure higher electrostatic discharge (ESD) levels as the thickness of the AlGaN EBL increased. The observed improvement in the ESD endurance ability could be attributed to the fact that the thickened p-AlGaN EBL may partly fill the dislocation-related pits that occur on the surface of the InGaN-GaN multiple-quantum well (MQW) and that are due to the strain and the low-temperature-growth process. If these dislocation-related pits are not partly suppressed, they will eventually result in numerous surface pits associated with threading dislocations that intersect the InGaN-GaN (MQW), thereby reducing the ESD endurance ability. The results of the experiment show that the ESD endurance voltages could increase from 1500 to 6000 V when the thickness of the p-AlGaN EBL in the GaN LEDs is increased from 32.5 to 130 nm, while the forward voltages and light output powers remained almost the same. 相似文献
913.
Sun-Jung Kim Pyeong-Seok Cho Jong-Heun Lee Chong-Yun Kang Jin-Sang Kim Seok-Jin Yoon 《Ceramics International》2008,34(4):827-831
Various compositions of gas sensing films were prepared by the combinatorial deposition of SnO2, ZnO, and WO3 sol solutions and their gas sensing behaviors were investigated. The film composition could be manipulated conveniently via the alternate dropping of different oxide sol solutions. From the correlation between film compositions and gas sensitivities, the selective detection of C2H5OH and CH3COCH3 in the presence of CO, C3H8, H2, and NO2 could be attained. In addition, the discrimination between C2H5OH and CH3COCH3, which is a challenging issue due to their similar chemical nature, becomes possible. This research demonstrates the precise design of the sensor-material composition for the selective gas detection via the combinatorial approach. 相似文献
914.
Heidi Bernas Arie J. Plomp Johannes H. Bitter Dmitry Yu. Murzin 《Catalysis Letters》2008,120(1-2):8-13
The density functional theory (DFT/B3LYP) calculations were applied to investigate the interaction of a Pt6 particle with the ZSM-5 zeolite framework. The electronic structure of the metal particle is strongly affected by the interaction with basic framework oxygens and acid sites of the zeolite support. Adsorption on basic sites (Eads = 6 kcal/mol) favors the formation of the electron enriched metal cluster. Interaction of the platinum cluster with the acid site characterized by stabilization energy of 47 kcal/mol results in oxidation of the metal particle and suppression of Brønsted acidity of the support. The hypothesis is put forward that the oxidized platinum particle can function as an active site for the alkane isomerisation on platinum supported high silica zeolites. 相似文献
915.
916.
In the fiber Bragg grating sensing using a superluminescent diode as the light source and an arrayed waveguide grating as the wavelength interrogator, the wavelength measurement error due to the spectral modulation of the superluminescent diode is theoretically formulated and quantitatively analyzed by computer simulation. It is shown that the wavelength measurement errors produced with the use of real superluminescent diodes are in very good agreement with the theoretical results. In order to reduce the wavelength measurement error due to the spectral modulation of superluminescent diode, two different types of remedies are proposed that utilize the temperature switching of superluminescent diode and that adjust the bandwidths of fiber Bragg grating and arrayed waveguide grating, and their efficacies are experimentally demonstrated together with good quantitative agreement with the theoretical calculation. 相似文献
917.
Rosenberg Florian Curbera Francisco Duftler Matthew J. Khalaf Rania 《Internet Computing, IEEE》2008,12(5):24-31
The use of RESTful Web services has gained momentum in the development of distributed applications based on traditional Web standards such as HTTP. In particular, these services can integrate easily into various applications, such as mashups. Composing RESTful services into Web-scale workflows requires a lightweight composition language that's capable of describing both the control and data flow that constitute a workflow. The authors address these issues with Bite, a lightweight and extensible composition language that enables the creation of Web-scale workflows and uses RESTful services as its main composable entities. 相似文献
918.
919.
Translating a typical business process modelling language to a web services ontology through lightweight mapping 总被引:1,自引:0,他引:1
G. Nadarajan Y.-H. Chen-Burger 《Software, IET》2007,1(1):1-17
Bridging the gap between enterprise modelling methods and Semantic Web services is an important yet challenging task. For organisations with business goals, the automation of business processes as Web services is increasingly important, especially with many business transactions taking place within the Web today. Taking one approach to address this problem, a lightweight mapping between Fundamental Business Process Modelling Language (FBPML) and the Web Services Ontology (OWL-S) is outlined. The framework entails a data model translation and a process model translation via the use of ontologies and mapping principles. Several working examples of the process model translations are presented together with the implementation of an automated translator. FBPML constructs and process models that could not be translated to OWL-S equivalents highlight the differences between the languages of the two domains. It also implies that evolving Semantic Web technologies, in particular OWL-S, are not adequate for all service modelling needs and could thus benefit from the more traditional and mature BPM methods. On a more interesting note, this is effectively the first step towards enabling a semantic-based business workflow system 相似文献
920.