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   235篇
  免费   20篇
电工技术   1篇
化学工业   98篇
机械仪表   1篇
建筑科学   1篇
能源动力   3篇
轻工业   63篇
水利工程   2篇
无线电   6篇
一般工业技术   25篇
冶金工业   5篇
自动化技术   50篇
  2023年   5篇
  2022年   29篇
  2021年   10篇
  2020年   6篇
  2019年   9篇
  2018年   7篇
  2017年   12篇
  2016年   12篇
  2015年   11篇
  2014年   9篇
  2013年   11篇
  2012年   14篇
  2011年   15篇
  2010年   12篇
  2009年   17篇
  2008年   15篇
  2007年   14篇
  2006年   5篇
  2005年   8篇
  2004年   3篇
  2003年   6篇
  2002年   3篇
  2001年   3篇
  2000年   4篇
  1999年   3篇
  1998年   4篇
  1997年   1篇
  1995年   1篇
  1994年   4篇
  1990年   1篇
  1986年   1篇
排序方式: 共有255条查询结果,搜索用时 15 毫秒
101.
Agricultural wastes derived from olive oil production were used in wastewater engineering as lead, cadmium, and nickel ions sorbents. Experiments were carried out in distilled water (Troom) by the use of packed bed columns filled with grains (1–3?mm) which were eluted with single and multimetal solutions in the 3–10?mg/L concentration range. Operations were performed with different sorbent dosage (4–8?g) at flow rates ranging 0.3–0.7?L/h until exhaustion. Best retention capacities were 8.15, 3.5, and 2.9?mg/gsorbent respectively for Pb+2, Cd+2, and Ni+2 in the case of the multimetal system (0.3?L/h, 8?g of sorbent, and 10?mg/L influent solution). EDX analysis carried out on the sorbent surface showed that the wt % ratios between the sorbed metals were similar to the ratios between the column overall capacities. Inter-diffusion of the ions in the Nernst stationary liquid film around the particle was identified as the step which controls the kinetics of the process. Exhausted wastes were successively recycled in cement mortars together with another aggregate as exhausted porous glass in order to obtain a lightweight composite with good consistency and interesting mechanical resistances.  相似文献   
102.
Abnormal Grain Growth in Alumina: Synergistic Effects of Yttria and Silica   总被引:4,自引:0,他引:4  
Abnormal grain growth without strong anisotropy or faceting of the grains has been observed in high-purity yttria-doped alumina specimens, often starting at the surface and spreading right through the bulk at higher sintering temperatures. This appears to occur because of an interaction between Si contamination from sintering and the yttria doping; no such effect is seen for undoped samples. Similar microstructures were observed after deliberate Y/Si codoping. Analytical STEM showed that some grain boundaries bordering on large grains contained more Si than Y. HRTEM and diffuse dark-field imaging revealed thin (0.5–0.9 nm) disordered layers at some boundaries bordering large grains. It appears that Si impurities are accumulating at some boundaries and together with the Y inducing a grain boundary structural transformation that accounts for the dramatically increased mobility of these boundaries.  相似文献   
103.
The problem consists in finding a transshipment facilities location that maximizes the total net utility when the handling utilities at the facilities are stochastic variables, under supply, demand, and lower and upper capacity constraints. The total net utility is given by the expected total shipping utility minus the total fixed cost of the located facilities. Shipping utilities are given by a deterministic utility for shipping freight from origins to destinations via transshipment facilities plus a stochastic handling utility at the facilities, whose probability distribution is unknown. After giving the stochastic model, by means of some results of the extreme values theory, the probability distribution of the maximum stochastic utilities is derived and the expected value of the optimum of the stochastic model is found. An efficient heuristics for solving real‐life instances is also given. Computational results show a very good performance of the proposed methods both in terms of accuracy and efficiency.  相似文献   
104.
The vault of the Arles City Hall, or H?tel de Ville, represents the architect’s revenge on the corporations of masons. Completed in 1676, the relationship of span to rise of the vault make it the boldest work of masonry in Europe, and while this complex vault appears to be a unitary structure, two vaults actually share the work, leaning against each other on the big arch. Bibliographic and archival research showed that surveys of the vault were missing; the only ancient survey was lost in the 1970s. A recent survey campaign made an analysis possible, leading to a hypothesis about the architect Mansart’s choices, based on hypothetical solutions to resolve the formal construction issues of the vault. A connoisseur of geometry and optics, Mansart knew that the human eye was unable to perceive the exact geometry of a surface. Knowing that he couldn’t control the intersections of vault portions and then the joints of the rows in the space, he introduced a solution that involved drawing the intersections in plan and then projecting them on the vault to obtain the spatial intersections. No further constructions of the bold type followed the vaulted space in the H?tel de ville, because the spatial research that linked the new discipline (stereotomy) to the quality of architectural space had by then come to an end.
La vo?te de l’H?tel de ville d’Arles est le chef d’oeuvre de la stéréotomie fran?aise [Perouse de Montclos 1983: 123-126]  相似文献   
105.
The notion of Multi-Agent System environment is currently considered as a mediating entity, functioning as enabler but possibly also as a manager and constrainer of agent actions, perceptions, and interactions. In this paper, we analyze how the environment could be a first class abstraction to support the building, the development and the management of Agreements in decentralized and open systems between autonomous agents. To this aim we analyze the synergies between the environment and the foundational dimensions of agreement technologies such as semantics, norms, organizations, argumentation & negotiation, trust.  相似文献   
106.
Among the requirements for all life forms is the ability to self-replicate. In eukaryotic cellular systems, this division is achieved through cytokinesis, and is facilitated by the (re)arrangement and interaction of cytoskeletal proteins with lipids and other proteins localized to the plasma membrane. A fascinating challenge of modern synthetic biology is the bottom-up reconstitution of such processes for the generation of an artificial cell. One crucial step towards this goal is the functional reconstitution of the protein-anchoring machinery to facilitate cytokinesis into lipid vesicles. True to the ideal of a minimal cell-like system, we here describe the formation of an actin-based cytoskeleton within giant unilamellar vesicles (GUVs) made from porcine brain lipid extracts. We demonstrate that the actin filaments are localised and anchored to the interior walls of the GUVs through the spectrin/ankyrin proteins, and produce tightly packed actin bundles. These studies allow for the examination of cytoskeletal rearrangements within a cell-like model membrane system and represent important first steps in reconstituting the minimal machinery required for the division of an artificial cell. In addition, the study of such minimal systems can shed light on protein functions that are commonly unobservable or hidden within the overwhelming complexity of cells.  相似文献   
107.
108.
This first issue of Language Resources and Evaluation is dedicated to the memory of Antonio Zampolli, whom few would dispute is the one person who has led the way in promoting and establishing the development of language resources (LR) of all kinds for the past four decades. In this inaugural issue, we have attempted to bring together articles by major figures in the field in order to provide an overview of the history, state of the art, and the future of the creation, annotation, exploitation, evaluation, and distribution of LR. Hopefully, this collection of articles will serve not only as a tribute to Antonio, but also as a framework out of which this journal – which almost certainly would not have existed were it not for him – can grow.  相似文献   
109.
The probability of pressurized flow conditions occurring in existing bridges is forecast to increase due to possible changes in extreme precipitation, storm surges, and flooding predicted under climate change scenarios. The presence of a pressure flow is generally associated with scouring processes in proximity to the bridge. Scouring can also occur around bridge piers, possibly causing infrastructure failure. Although there is a vast literature on bridge pier scour and pressure flow scour, only a few studies have investigated their combined effect. This study will provide a new overview of the main features of bridge pier scour under pressurized flow conditions, based on laboratory experiences. Special focus is placed on the analysis of the flow features under pressure and free surface conditions and to the temporal evolution of the scour. A comparison with existing literature data is also conducted. The results highlight the nonlinear nature of scour processes and the need to consider pressurized flow conditions during structural design, as the interaction between pressure flow and the bridge pier strongly influences scour features and leads to scour depths much greater than the sum of the individual scours created only by pressure flow or pier presence.  相似文献   
110.
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