全文获取类型
收费全文 | 72篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
化学 | 26篇 |
力学 | 10篇 |
数学 | 23篇 |
物理学 | 15篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1965年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有74条查询结果,搜索用时 15 毫秒
41.
The world runs on networks over which signals communicate sequences of symbols, e.g. numerals. Examining both engineered and natural communications networks reveals an unsuspected order that depends on contact with an unpredictable entity. This order has three roots. The first is a proof within quantum theory that no evidence can ever determine its explanation, so that an agent choosing an explanation must do so unpredictably. The second root is the showing that clocks that step computers do not “tell time” but serve as self-adjusting symbol-handling agents that regulate “logically synchronized” motion in response to unpredictable disturbances. Such a clock-agent has a certain independence as well as the capacity to communicate via unpredictable symbols with other clock-agents and to adjust its own tick rate in response to that communication. The third root is the noticing of unpredictable symbol exchange in natural systems, including the transmission of symbols found in molecular biology. We introduce a symbol-handling agent as a role played in some cases by a person, for example a physicist who chooses an explanation of given experimental outcomes, and in other cases by some other biological entity, and in still other cases by an inanimate device, such as a computer-based detector used in physical measurements. While we forbear to try to explain the propensity of agents at all levels from cells to civilizations to form and operate networks of logically synchronized symbol-handling agents, we point to this propensity as an overlooked cosmic order, an order structured by the unpredictability ensuing from the proof. Appreciating the cosmic order leads to a conception of agency that replaces volition by unpredictability and reconceives the notion of objectivity in a way that makes a place for agency in the world as described by physics. Some specific implications for physics are outlined. 相似文献
42.
Madjid Hadioui Patrick Sharrock Mohamed-Oimar Mecherri Véronique Brumas Marina Fiallo 《Chemical Papers》2008,62(5):516-521
In the effort to improve the performance of hydroxylapatite (HA) in removing lead ions from aqueous solutions, millimeter-sized
granules with 50 % porosity were synthesized. Such HA particles, after drying at 100°C, or heating at 800°C or 1100°C, exhibited
the specific surface areas of 50 m2 g−1, 25 m2 g−1, and 5 m2 g−1, respectively. It was found that heavy metal sorption capacity of HAs can be related to their surface area. Non-calcined
granules were difficult to handle and easy to crush. Hardened granules showed heavy metal absorption on their outer surfaces.
Absorption capacity of sintered HA particles towards lead was lower but adsorbed lead ions were spread inside the porous structure
of HA granules more evenly. Under flow conditions, lead ions were captured by HA at a rate of 0.5 mg g−1 min−1. Small lead phosphate aggregates were released from the HA sorbent together with calcium ions. Size of the aggregates depended
on the lead concentration and ranged from 1–50 μm in diameter; the aggregates could be removed by ultrafiltration. Results
show that porous hardened HA granules can be used as an efficient phosphate source for the immobilization of lead ions from
aqueous media. Organic ligands tend to interfere with the water purification procedure. 相似文献
43.
Gustavo E. Imoberdorf Fariborz Taghipour Madjid Mohseni 《Journal of photochemistry and photobiology. A, Chemistry》2008,198(2-3):169-178
For modeling and optimization of photoreactors, knowing radiation distribution inside the reactor is essential because the kinetics of photochemical and photocatalytic reactions are strongly dependent on the local incident radiation. In this work, a Monte Carlo multi-lamp radiation model is proposed. The model takes into account the reflection on the surface of the lamps, the refraction in the quartz lamp envelope, as well as the adsorption and the isotropic re-emission of radiation in the mercury vapor of the lamp. To quantify the shadowing effect among the lamps, the effective transmittance through a UV-lamp turned on, a lamp turned off, and a lamp quartz envelope have been measured. For validation purposes, experimental measurements have been performed using one, two, and three lamps. The model predictions show good agreement with the experimental results. Finally, in order to simplify the numerical solution of the model, the validity of assuming the lamps 100% opaque and 100% transparent have been analyzed. 相似文献
44.
The Ugi-Smiles reaction of S-benzyl thiouracil have been exploited in several three-step sequences for the preparation of aminopyrimidine libraries with high diversity. After the 4-component coupling, oxidation of the thioether to sulfone is followed by displacement of the latter by various carbon-centered nucleophiles (cyanide, malonate, boronic acids) or amines. The efficiency of the whole sequence was further demonstrated with one-pot procedures. 相似文献
45.
46.
47.
Madjid Eshaghi Gordji Norouz Ghobadipour Ali Ebadian 《Rendiconti del Circolo Matematico di Palermo》1936,60(1-2):125-137
In this paper, we will apply a fixed point method for proving the generalized Hyers–Ulam–Rassias stability of the partial derivations for Jensen type n-variable functional equations. 相似文献
48.
The d2-law validity during n-decane droplet vaporization in microgravity environment is examined experimentally. Two sets of experiments are performed, under normal and microgravity, in stagnant hot atmospheric environment. The environment temperature is varied in the range up to 967 K. The droplet is suspended onto the cross point of two micro-fibers of 14 μm in diameter. This technique enables to greatly minimize the effect of fiber on droplet heat and mass transfer. The results show that, for ambient temperatures below approximately 950 K, departure from the d2-law is observed during droplet vaporization in microgravity environment. In addition, the droplet lifetime is longer in microgravity than in normal gravity under the same ambient test conditions. However, for temperatures exceeding approximately 950 K, the experimental results demonstrate that the d2-law holds throughout the entire droplet lifetime, and the mass transfer rate is identical in both microgravity and normal gravity environments. 相似文献
49.
A taxonomy and review of the fuzzy data envelopment analysis literature: Two decades in the making 总被引:1,自引:0,他引:1
Data envelopment analysis (DEA) is a methodology for measuring the relative efficiencies of a set of decision making units (DMUs) that use multiple inputs to produce multiple outputs. Crisp input and output data are fundamentally indispensable in conventional DEA. However, the observed values of the input and output data in real-world problems are sometimes imprecise or vague. Many researchers have proposed various fuzzy methods for dealing with the imprecise and ambiguous data in DEA. In this study, we provide a taxonomy and review of the fuzzy DEA methods. We present a classification scheme with four primary categories, namely, the tolerance approach, the α-level based approach, the fuzzy ranking approach and the possibility approach. We discuss each classification scheme and group the fuzzy DEA papers published in the literature over the past 20 years. To the best of our knowledge, this paper appears to be the only review and complete source of references on fuzzy DEA. 相似文献
50.
This paper reports an experimental study on the effect of the fuel nozzle orifice geometry on the stability of turbulent non-premixed methane flame. Different internal geometries (orifice equivalent diameter, length to diameter ratio and contraction angle) of a circular and a rectangular nozzle with an aspect ratio of 2 were examined. The strength of the co-airflow was also varied to assess its impact on the jet flame stability. The experimental data revealed that the level of turbulence in the jet near-field is, in general, higher for the rectangular nozzle in comparison with the circular nozzle. This high level of turbulence was found to accelerate the liftoff transition of the attached flame. The results revealed also that there is a clear interplay between the flame liftoff height and the jet flow characteristics. That is, a rectangular jet, which spreads faster along the minor axis and generates higher near-field turbulence, results in a flame base sitting closer to the nozzle exit in comparison with that of its circular nozzle counterpart. Finally, the presence of a moderate co-airflow resulted in a higher flame liftoff velocity and height. It also led to the appearance of a hysteresis phenomenon in the low jet velocity range regardless of the exit orifice shape of the fuel nozzle. 相似文献