首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   323篇
  免费   17篇
  国内免费   1篇
电工技术   4篇
综合类   1篇
化学工业   117篇
金属工艺   17篇
建筑科学   16篇
矿业工程   1篇
能源动力   7篇
轻工业   34篇
水利工程   2篇
无线电   11篇
一般工业技术   52篇
冶金工业   33篇
原子能技术   1篇
自动化技术   45篇
  2023年   6篇
  2022年   20篇
  2021年   30篇
  2020年   16篇
  2019年   17篇
  2018年   9篇
  2017年   19篇
  2016年   23篇
  2015年   7篇
  2014年   17篇
  2013年   21篇
  2012年   26篇
  2011年   12篇
  2010年   14篇
  2009年   13篇
  2008年   10篇
  2007年   17篇
  2006年   10篇
  2005年   10篇
  2004年   7篇
  2003年   6篇
  2002年   5篇
  2001年   4篇
  2000年   5篇
  1999年   4篇
  1998年   1篇
  1997年   2篇
  1996年   8篇
  1978年   1篇
  1977年   1篇
排序方式: 共有341条查询结果,搜索用时 15 毫秒
91.
92.
In recent years, there has been a growing interest in purely organic materials showing ultralong room-temperature phosphorescence with lifetimes in the range of seconds. Still, the longest known phosphorescence lifetimes are only achieved with crystalline systems so far. Here, a rational design of a completely new family of halogen-free organic luminescent derivatives in amorphous matrices, displaying both conventional fluorescence and phosphorescence is reported. Hydrogen bonding between the newly developed emitters and an ethylene-vinyl alcohol copolymer (Exceval) matrix, which efficiently suppresses vibrational dissipation, enables bright long-lived phosphorescence with lifetimes up to 2.6 s at around 480 nm. The importance of the chosen matrix is shown as well as the implementation in an organic programmable luminescent tag.  相似文献   
93.
In practice, checks on dangerous goods transports often detect leaks of powdered dangerous goods from valved bags. In this work, the influence factors of a sudden release of powdery substances from the valves of valved bags were investigated. Drop tests were performed on paper bags of UN design type 5M2 with internal sleeve valve using 2 different powdery substances (Esplas H130 and zinc oxide “Rotsiegel”). The internal sleeve valves of all test samples were not sift‐proof with respect to both filling substances. For almost all test samples, the Esplas H130 powder already leaked out of pasted joints during manual filling. This is a contradiction to the requirement in UN 6.1.4.18.1, according to which closures and joints of paper bags 5M2 should be sift‐proof. In the drop tests, longer valve lengths had a greater sealing effect for both filling substances (for filling degrees of at least 95% and for test samples which had already been mechanically loaded). As an extreme example, at the drop height of 1.20 m and a filling degree of 100%, the released amount of zinc oxide powder from a 10‐cm‐long valve was about 16 times higher than from a valve length of 12.5 cm. The valve length is therefore a safety‐relevant parameter and should be specified by the manufacturer. To ensure that only filling goods with similar physical properties in comparison with the test substance are used for valved bags, the user must be informed of the particle size of the test substance.  相似文献   
94.
The heat shock response is a primordial defense mechanism against cell stress and protein misfolding. It proceeds with the minimum number of mechanisms that any regulatory network must include, a stress-induced activation and a feedback regulation, and can thus be regarded as the archetype for a cellular regulatory process. We propose here a simple mechanistic model for the eukaryotic heat shock response, including its mathematical validation. Based on numerical predictions of the model and on its sensitivity analysis, we minimize the model by identifying the reactions with marginal contribution to the heat shock response. As the heat shock response is a very basic and conserved regulatory network, our analysis of the network provides a useful foundation for modeling strategies of more complex cellular processes.  相似文献   
95.
Optimization of inelastic cylindrical shells with internal supports   总被引:1,自引:1,他引:0  
A non-linear programming method is developed for optimization of inelastic cylindrical shells with internal ring supports. The shells under consideration are subjected to internal pressure loading and axial tension. The material of shells is a composite which is considered as an anisotropic inelastic material obeying the yield condition suggested by Lance and Robinson. Taking geometrical non/linearity of the structure into account optimal locations of internal ring supports are determined so that the cost function attains its minimum value. A particular problem of minimization of the mean deflection of the shell with weakened singular cross sections is treated in a greater detail.  相似文献   
96.
Automation, in terms of systems such as adaptive/active cruise control (ACC) or collision warning systems, is increasingly becoming a part of everyday driving. These systems are not perfect though, and the driver has to be prepared to reclaim control in situations very similar to those the system easily handles by itself. This paper uses a questionnaire answered by 130 ACC users to discuss future research needs in the area of driver assistance systems. Results show that the longer drivers use their systems, the more aware of its limitations they become. Moreover, the drivers report that ACC forces them to take control intermittently. According to theory, this might actually be better than a more perfect system, as it provides preparation for unexpected situations requiring the driver to reclaim control.  相似文献   
97.
Two macaques (Macaca nemestrina) were trained to perform 3 self-directed behaviors on signal and to repeat behaviors after a 'repeat' signal. The cognitive processes underlying the monkeys' repeat performance were evaluated via multiple repetitions of the repeat signal, extended delay periods between target behavior and repeat signal, and by transferring the repeat signal to novel behaviors. The monkeys seemed to use representations of their own past behaviors as a basis for repetition performance, but they mostly failed to correctly repeat target behaviors after extended delays and during transfer tasks. Implications for episodic memory abilities are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
98.
The perception of texture has been correlated to the microstructure of particulate whey protein gels. A full, two-level, factorial experimental design was used in which the processing conditions, pH, heating rate and addition of salt were used as design factors. The texture of the gels was analysed by a sensory panel, and the microstructure was analysed by light and electron microscopy. The microstructure was quantified by using different types of image analysis.

In this study of particulate whey protein gels, the test principles of analysing texture were divided into two groups: destructive tests and non-destructive tests. The microstructural parameters can also be divided into two groups: overall network dimensions (pore size and particle size) and strand characteristics. The texture as measured with destructive methods was sensitive to overall network dimensions, whereas texture as measured with non-destructive methods was sensitive to the strand characteristics of particulate protein gels.  相似文献   

99.
The empirical part of this study is based on a survey of 600 Swedish households and a number of interviews where questions about residential energy behaviour and possible policy instruments for change were raised. The study provides insight into current behavioural patterns and gives a bottom-up perspective on the realistic perspective potentials for change and ways to achieve them. Residential energy use accounts for a fifth of the total in Northern nations and patterns of behaviour may influence levels of energy use to the same extent as choice of appliances. The study revealed those behavioural patterns that are efficient and those that need to be improved for energy conservation. Several policy instruments for change were identified in the study and they include combinations of information, economic measures, administrative measures and more user friendly technology as well as equipment with sufficient esthetic quality. Policy instruments that have fostered energy efficient behaviour in Sweden include the massive information campaigns during the oil crises in the 1970s as well as energy labelling of appliances. Still, many households are “energy-unaware” and several energy efficient behaviours are motivated not by energy conservation concern but of a perceived lack of time. This shows that it is important to have a broad perspective in energy conservation, to evaluate trends and to use policy instruments timely to support or discourage them.  相似文献   
100.
Platinum oxidation and sulphur deactivation in NO x storage catalysts   总被引:1,自引:0,他引:1  
A review covering some of the key catalytic transformations of the major monoterpene feedstocks. Monoterpenes are key ingredients in the flavor and fragrance industry, with α- and β-pinene (obtained from turpentine) being some of the most important. The review focuses on the hydrocarbons; pinene, limonene, carene, and the interconversion of the monooxygenates; geraniol/nerol, citronellol, citral, and citronellal. The major areas covered are catalytic hydrogenation/hydrogenolysis, dehydrogenation, rearrangement/isomerization/aromatization, reactions with carbon monoxide, epoxidation, and the addition of alcohols and acids.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号