全文获取类型
收费全文 | 1316篇 |
免费 | 64篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 305篇 |
金属工艺 | 15篇 |
机械仪表 | 33篇 |
建筑科学 | 98篇 |
矿业工程 | 2篇 |
能源动力 | 24篇 |
轻工业 | 205篇 |
水利工程 | 11篇 |
石油天然气 | 1篇 |
无线电 | 69篇 |
一般工业技术 | 213篇 |
冶金工业 | 169篇 |
原子能技术 | 3篇 |
自动化技术 | 220篇 |
出版年
2023年 | 14篇 |
2022年 | 20篇 |
2021年 | 32篇 |
2020年 | 19篇 |
2019年 | 35篇 |
2018年 | 30篇 |
2017年 | 35篇 |
2016年 | 41篇 |
2015年 | 36篇 |
2014年 | 44篇 |
2013年 | 73篇 |
2012年 | 61篇 |
2011年 | 62篇 |
2010年 | 54篇 |
2009年 | 49篇 |
2008年 | 67篇 |
2007年 | 61篇 |
2006年 | 37篇 |
2005年 | 41篇 |
2004年 | 41篇 |
2003年 | 27篇 |
2002年 | 35篇 |
2001年 | 23篇 |
2000年 | 31篇 |
1999年 | 26篇 |
1998年 | 78篇 |
1997年 | 46篇 |
1996年 | 26篇 |
1995年 | 19篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1986年 | 8篇 |
1984年 | 5篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1973年 | 8篇 |
1971年 | 10篇 |
1969年 | 8篇 |
1968年 | 5篇 |
排序方式: 共有1382条查询结果,搜索用时 246 毫秒
101.
Michael Arndt Sebastian Wille Luiza de Souza Vítor Fortes Rey Norbert Wehn Karsten Berns 《Robotics and Autonomous Systems》2013,61(11):1173-1185
Mobile robots and smart environments are two areas of research that can easily profit from each other. Smart environments, which are spaces unobtrusively equipped with sensors and actuators, providing ambient services to the people living within. Mobile robots inside those smart environments can use the existing infrastructure to increase their performance while decreasing the cost of local sensor systems. On the other side, evaluation of ambient services is often a laborious task. This work presents an approach that simplifies the evaluation by making use of two frameworks from robotics to perform tests in simulated smart environments. A method based on the language as action principle is used to extract realistic behavior of people living in real-world smart environments. Using this data, many different scenarios with varying configurations (different floor layouts, numbers and types of sensors, different number of people and pets) can easily be simulated and the performance of the ambient services evaluated. 相似文献
102.
103.
A model has been developed that describes the dependence of the moisture diffusion coefficient on the water fraction. Until the end of shrinkage has been achieved, the moisture diffusion coefficient is proportional to the second power of the water fraction. Due to shrinkage, the relevant capillary spaces available for water transport become smaller. Consequently, the moisture diffusion coefficient decreases continually. After the end of shrinkage, the flow resistance to the water moving toward the surface increases sharply due to penetrating air. This leads to a steep drop of the moisture diffusion coefficient by several powers of ten. Measurements were carried out with specimens of defined geometry to determine the moisture diffusion coefficient. On the basis of a specified limiting value, the model is capable of calculating the moisture diffusion for all initially specified raw materials moistures. The moisture can also be determined if the degree of drying shrinkage is known. Using the determined moisture diffusion coefficient, the first and the second drying section can be located. Drying tests were carried out in a laboratory dryer and the experimental results obtained were compared to the simulation results. The simulation results are in good agreement with the experimental results. 相似文献
104.
v. Berg v. Braunschweig Griesche Nüsslein Rieck und Stahl 《Zeitschrift für Jagdwissenschaft》1973,19(1):57-64
Ohne Zusammenfassung 相似文献
105.
106.
Elisabeth Altmaier Gabi Kastenmüller Werner Römisch‐Margl Barbara Thorand Klaus M. Weinberger Jerzy Adamski Thomas Illig Angela Döring Karsten Suhre 《Molecular nutrition & food research》2009,53(11):1357-1365
The effect of coffee consumption on human health is still discussed controversially. Here, we report results from a metabolomics study of coffee consumption, where we measured 363 metabolites in blood serum of 284 male participants of the Cooperative Health Research in the Region of Augsburg study population, aged between 55 and 79 years. A statistical analysis of the association of metabolite concentrations and the number of cups of coffee consumed per day showed that coffee intake is positively associated with two classes of sphingomyelins, one containing a hydroxy‐group (SM(OH)) and the other having an additional carboxy‐group (SM(OH,COOH)). In contrast, long‐ and medium‐chain acylcarnitines were found to decrease with increasing coffee consumption. It is noteworthy that the concentration of total cholesterol also rises with an increased coffee intake in this study group. The association observed here between these hydroxylated and carboxylated sphingolipid species and coffee intake may be induced by changes in the cholesterol levels. Alternatively, these molecules may act as scavengers of oxidative species, which decrease with higher coffee intake. In summary, we demonstrate strong positive associations between coffee consumption and two classes of sphingomyelins and a negative association between coffee consumption and long‐ and medium‐chain acylcarnitines. 相似文献
107.
The total energy influx for a typical radiofrequency process plasma has been measured by means of a simple thermal probe. The procedure is based on the measurement of temporal slope of the substrate temperature during the plasma process. A substrate dummy which is thermally isolated and inserted into the plasma at substrate position served as thermal probe. It can be moved in vertical and horizontal directions in order to measure the different energy influxes and their topology in the reactor vessel. The knowledge of the spatial distribution is important for coating or sputtering processes.Different contributions to the total energy influx can be identified by different orientation of the thermal probe. If the thermal probe is orientated to the rf-electrode (“down”) the energy influx is much higher than in the opposite direction. This difference can be explained by an additional influx due to the secondary electron emission from the powered rf-electrode. 相似文献
108.
A set of 32 different codons were introduced in a lacZ expression vector (pPTK400) immediately 3' from the AUG initiation codon. Expression of the lacZ gene was determined in Saccharomyces cerevisiae by measuring the amount of beta-galactosidase fusion protein using immuno-gel electrophoresis. A 5.3-fold difference in expression was found among the various constructs. It was found that there was no preference for a certain nucleotide in any position of the second codon and there was no distinct correlation between the level of tRNA corresponding to any particular second codon and expression. No correlation could be found between the local secondary structure and expression. When the overall codon usage in yeast and the codon usage in the second position of the mRNA is compared, there is no obvious significant difference in preference. This indicates that in yeast, in contrast to Escherichia coli, the codon choice at the beginning of the mRNA does not deviate from the one further downstream and is determined by the requirements for optimal translation elongation. Important determinants of the optimal context for an initiation codon in yeast therefore must be located mainly 5' from this codon. 相似文献
109.
Analysis of high-molecular-weight oligosaccharides from human milk by liquid chromatography and MALDI-MS. 总被引:4,自引:0,他引:4
B Finke B Stahl A Pfenninger M Karas H Daniel G Sawatzki 《Analytical chemistry》1999,71(17):3755-3762
Pooled human milk oligosaccharides were fractionated by anion-exchange chromatography on AG 1-X2 and by an improved gel filtration procedure that allowed the separation of large oligosaccharides on Toyopearl HW 40 (S) and Bio-Gel P-6 columns, respectively. The analysis of the resulting nonderivatizated fractions by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) revealed several neutral and acidic high-molecular-weight oligosaccharides. So far unknown acidic oligosaccharides containing up to 20 monomers were detected in a molecular mass range of 2094-3626 Da. Furthermore, neutral structures containing up to 35 monosaccharides were identified after fractionation on Toyopearl HW 40 (S) and subsequent P-6 fractionation, demonstrating the suitability of the applied method for the preparation of oligosaccharides in this high-molecular-mass range. The composition of the detected oligosaccharides was found to be the same as those previously identified in oligosaccharides of lower masses. However, an enormous structural heterogeneity was observed when acidic and neutral fractions were characterized by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). From our analysis we may conclude that each molecular mass identified by MALDI-MS corresponds to a variety of isomeric structures. The total number of oligosaccharides occurring in human milk may consequently be much higher than estimated before. 相似文献
110.
Karsten Neumann 《Datenschutz und Datensicherheit - DuD》2008,32(10):644-644
Ohne Zusammenfassung 相似文献