全文获取类型
收费全文 | 1583篇 |
免费 | 180篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 37篇 |
综合类 | 11篇 |
化学工业 | 454篇 |
金属工艺 | 51篇 |
机械仪表 | 22篇 |
建筑科学 | 98篇 |
矿业工程 | 9篇 |
能源动力 | 51篇 |
轻工业 | 108篇 |
水利工程 | 15篇 |
石油天然气 | 1篇 |
无线电 | 127篇 |
一般工业技术 | 343篇 |
冶金工业 | 80篇 |
原子能技术 | 6篇 |
自动化技术 | 352篇 |
出版年
2024年 | 4篇 |
2023年 | 52篇 |
2022年 | 65篇 |
2021年 | 91篇 |
2020年 | 74篇 |
2019年 | 80篇 |
2018年 | 86篇 |
2017年 | 92篇 |
2016年 | 88篇 |
2015年 | 86篇 |
2014年 | 100篇 |
2013年 | 114篇 |
2012年 | 135篇 |
2011年 | 133篇 |
2010年 | 84篇 |
2009年 | 84篇 |
2008年 | 75篇 |
2007年 | 79篇 |
2006年 | 46篇 |
2005年 | 38篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 21篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 5篇 |
1979年 | 1篇 |
1976年 | 4篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有1765条查询结果,搜索用时 15 毫秒
991.
Florian Hanusch Robert Kender Volker Engel Sebastian Rehfeldt Harald Klein 《American Institute of Chemical Engineers》2019,65(8):e16598
Liquid maldistribution is one of the main deficiencies in random packed column design. Therefore, the knowledge of liquid distribution and its model-based prediction is of great interest. This work aims to further develop and validate the TUM–WelChem Cell Model for random packed columns. First, cell dimension calculations and the determination of random packing element orientations are standardized. The original WelChem Cell Model applies a liquid distribution mechanism based on liquid spread factors derived by virtual 3D irrigation experiments. An extension of the model involves the implementation of liquid and gas load related distribution mechanisms, considering dispersion effects caused by liquid loading and the countercurrent gas flow. The wall flow is refined by an increase of packing porosity at the column wall. Liquid distribution profiles provided by the TUM–WelChem Cell Model are validated against experimental data and show good agreement for both uniform and point source initial liquid distribution. 相似文献
992.
993.
994.
995.
A novel, microwave-assisted, high-temperature UV digestion procedure was developed for the accelerated decomposition of interfering dissolved organic carbon (DOC) prior to trace element analysis of liquid samples such as, industrial/municipal wastewater, groundwater, and surface water, body fluids, infusions, beverages, and sewage. The technique is based on a closed, pressurized, microwave digestion device. UV irradiation is generated by immersed electrodeless Cd discharge lamps (228 nm) operated by the microwave field in the oven cavity. To enhance excitation efficiency an antenna was fixed on top of the microwave lamp. The established immersion system enables maximum reaction temperatures up to 250-280 degrees C, resulting in a tremendous increase of mineralization efficiency. Compared to open UV digestion devices, decomposition time is reduced by a factor of 5 and the maximum initial concentration of DOC can be raised by at least a factor of 50. The system's performance on a real-type sample was evaluated for the mineralization of skimmed milk (IRMM, CRM 151) and subsequent determination of trace elements using standard spectroscopic techniques. Recovery for Cd (109%), Cu (112%), Fe (99%), and Pb (96%) showed good agreement with the 95% confidence interval of the certified values. 相似文献
996.
Loudwig S Nicolet Y Masson P Fontecilla-Camps JC Bon S Nachon F Goeldner M 《Chembiochem : a European journal of chemical biology》2003,4(8):762-767
The photoregulation of the catalytic activity of butyrylcholinesterase (BChE) was investigated by treating the enzyme with a newly developed carbamylating reagent, N-methyl-N-(2-nitrophenyl)carbamoyl chloride, which has proved to be an efficient photoremovable alcohol-protecting group. BChE was efficiently inhibited in a time- and concentration-dependent manner, and the enzyme could be protected against inhibition by active-site-specific ligands (that is, tacrine). The inactivation kinetics showed a biphasic character, which can be analyzed as the result of the existence of two conformational states in solution. Pseudo-irreversible inactivation of BChE, which results from catalytic serine carbamylation, was suggested by recovery of the enzyme activity after dilution and was demonstrated by X-ray crystallography. Remarkably, the 3D structure of the carbamylated BChE conjugate showed a nonambiguous carbamylation of the catalytic serine residue as the only chemical modification on the protein. The photoreversibility of the enzyme inactivation was analyzed by irradiating the inactivated enzyme at 365 nm and was shown to reach completion in some conditions. The efficient and specific "caging" of BChE, together with the availability of carbamylated BChE crystals, will offer a unique possibility to study the catalytic properties of this enzyme by kinetic crystallography after cryophotolytic uncaging of the enzyme conjugate crystals. 相似文献
997.
Hirschberger Gilad; Florian Victor; Mikulincer Mario 《Canadian Metallurgical Quarterly》2005,50(3):246
Objective: To examine whether death anxiety underlies emotional reactions toward people with disabilities (PWDs). Study Design: In Study 1, participants were primed with thoughts of death, read a vignette describing a PWD, and completed a compassion scale. Study 2 replicated the design of Study 1 and also examined the impact of target ethnicity. Studies 3 and 4 assessed the impact of physical disability on death-related cognitions and on fear of personal death. Results: Men reacted to death primes by emotionally withdrawing from a PWD and reporting less compassion, whereas women exhibited more compassionate responses. These differences in compassion were reflected in the death-related cognitions and fears sparked by physical disability. Conclusions: The human need to manage the terror of death shapes emotional reactions toward PWDs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
998.
Large Grid systems not only provide massive aggregated computing power but also an unprecedented amount of distributed storage space. Unfortunately, the dynamic behavior of the Grid, caused by varying resource availability, unpredictable data updates, and the impact of local site policies makes it difficult to exploit the full capabilities of Data Grids.We present an analytical model for determining the optimal number of replica servers, catalog servers, and catalog sizes to guarantee a given overall reliability in the face of unreliable components. Our model captures the characteristics of peer-to-peer-like environments as well as that of Grid systems. Empirical simulations confirm the accuracy of our analytical model. 相似文献
999.
1000.
Dieter Schmalstieg Gerhard Schall Daniel Wagner István Barakonyi Gerhard Reitmayr Joseph Newman Florian Ledermann 《Computer Graphics and Applications, IEEE》2007,27(4):48-57
Mobile augmented reality requires georeferenced data to present world-registered overlays. To cover a wide area and all artifacts and activities, a database containing this information must be created, stored, maintained, delivered, and finally used by the client application. We present a data model and a family of techniques to address these needs. 相似文献