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   335篇
  免费   26篇
电工技术   3篇
化学工业   69篇
金属工艺   16篇
机械仪表   23篇
建筑科学   15篇
能源动力   13篇
轻工业   42篇
水利工程   7篇
石油天然气   5篇
无线电   29篇
一般工业技术   49篇
冶金工业   24篇
原子能技术   2篇
自动化技术   64篇
  2023年   5篇
  2022年   8篇
  2021年   22篇
  2020年   16篇
  2019年   13篇
  2018年   30篇
  2017年   21篇
  2016年   29篇
  2015年   10篇
  2014年   25篇
  2013年   25篇
  2012年   19篇
  2011年   17篇
  2010年   18篇
  2009年   8篇
  2008年   9篇
  2007年   6篇
  2006年   5篇
  2005年   7篇
  2004年   3篇
  2003年   7篇
  2002年   9篇
  1999年   6篇
  1998年   6篇
  1997年   4篇
  1996年   5篇
  1995年   3篇
  1994年   3篇
  1993年   2篇
  1992年   2篇
  1991年   4篇
  1990年   2篇
  1988年   2篇
  1987年   4篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
排序方式: 共有361条查询结果,搜索用时 31 毫秒
91.
In this paper, for one-dimensional stochastic linear fractional systems in terms of the Riemann–Liouville fractional derivative, the optimal control is derived. It is assumed that the state is completely observable and all the information regarding this is available. The formulation leads to a set of stochastic fractional forward and backward equation in the Riemann–Liouville sense. The proposed method has been checked via some numerical simulations which show the effectiveness of the fractional stochastic optimal algorithm.  相似文献   
92.
Assembly sequences planning for simultaneous engineering applications   总被引:1,自引:2,他引:1  
This paper describes a Generative Assembly Process Planner (GAPP) used to generate and evaluate assembly sequence alternatives which can be used in simultaneous engineering applications. Given a graph model of the product to be assembled, optimal assembly sequences are automatically generated and evaluated in a single process. Geometric feasibility and accessibility constraints on assembly operations which help prune the search space are presented. Assembly-related criteria which guide the search to an optimal solution are described. These include: number of reorientations, concurrent execution of assembly tasks, grouping of similar tasks and stability criteria. The relative weights of various criteria can be varied interactively resulting in different optimal assembly sequences. The ability of GAPP to generate and evaluate assembly alternatives when various criteria are enabled or disabled or their relative importance is changed makes it an effective tool for simultaneous engineering/manufacturing applications. Examples are included to demonstrate GAPP's use and potential for assessing assembly, disassembly, repair and maintenance procedures.  相似文献   
93.
Tungstated zirconia (WO3/ZrO2 with WO3 loadings of 9.9 (WZ9.9), 15.5 (WZ15.5), and 15.7 wt% (WZ15.7)) and Amberlyst (15, 35, 36, 39 and 45) catalysts were employed to upgrade pyrolysis bio-oil of acacia sawdust through an esterification reaction using methanol at atmospheric pressure and room temperature or 80 °C. The upgrading efficiency was evaluated by measuring the total acid number (TAN) and viscosity. The viscosity and TAN of the resulting upgraded bio-oil were found to be dependent on the calcination temperature of the WO3/ZrO2 catalysts. At room temperature, the largest decrease in viscosity and TAN of the bio-oil and methanol mixture was obtained using WZ9.9 tungstated zirconia calcined at 900 °C. An increase in reaction temperature to 80 °C improved the flowability and TAN of the methanol-added bio-oil using WZ9.9 activated at 900 °C. The product distribution of the bio-oil upgraded using methanol revealed esterification to be the dominant reaction pathway under the reaction conditions of this study. When the ether extracted bio-oil was upgraded at 80 °C using methanol over catalysts, the Amberlyst catalysts were found more effective than tungstated zirconia catalysts in enhancing the esterification reaction and reducing TAN.  相似文献   
94.
95.
NAD(P)H quinone oxidoreductase-1 (NQO1) is a homodimeric protein that acts as a detoxifying enzyme or as a chaperone protein. Dicourmarol interacts with NQO1 at the NAD(P)H binding site and can both inhibit enzyme activity and modulate the interaction of NQO1 with other proteins. We show that the binding of dicoumarol and related compounds to NQO1 generates negative cooperativity between the monomers. This does not occur in the presence of the reducing cofactor, NAD(P)H, alone. Alteration of Gly150 (but not Gly149 or Gly174) abolished the dicoumarol-induced negative cooperativity. Analysis of the dynamics of NQO1 with the Gaussian network model indicates a high degree of collective motion by monomers and domains within NQO1. Ligand binding is predicted to alter NQO1 dynamics both proximal to the ligand binding site and remotely, close to the second binding site. Thus, drug-induced modulation of protein motion might contribute to the biological effects of putative inhibitors of NQO1.  相似文献   
96.
A low cost alkaline catalyst of dolomite (CaMg(CO3)2) was used to stabilize acacia sawdust bio-oil mixed with methanol. The upgrading efficiency was evaluated in terms of the total acid number (TAN) and viscosity. A change in the dolomite calcination temperature from 700 to 900 °C led to a significant change in the TAN and viscosity of the methanol-added bio-oil. Dolomite activated at higher temperatures had larger amounts of active CaO and MgO species due to the enhanced decarboxylation of calcium and magnesium carbonates. An increase in the dolomite content (1-5 wt%) decreased the TAN value of bio-oil remarkably. A thermal aging test of the methanol-added bio-oil upgraded using dolomite (calcined at 900 °C) at 50 °C for 24 h was carried out by storing the bio-oil at 80 °C for one week. Although the TAN value increased after the aging process, it was still lower than the TAN of raw bio-oil. In addition, increasing the methanol content (10-30 wt%) decreased the TAN and viscosity of the bio-oil significantly.  相似文献   
97.
In this work, astaxanthin nanodispersions were prepared using selected three component stabilizer system through a solvent-diffusion technique, with the particle size of 98.3 nm. The stability of produced nanodispersions against pH, salts, and heating were then evaluated. The produced nanodispersions exhibited good physical stability under wide ranges of pH (except around isoelectric point), sodium ion concentrations, and relatively high-temperature treatments (up to 60°C). However, formation of large particles was observed in either presence of calcium ions or higher thermal treatments (more than 60°C).  相似文献   
98.
99.
This paper considers a sample of successful wine bloggers, and clusters them into four distinct segments that could be targeted by wine marketers in different ways. Using text that they wrote in response to being named to a survey of 100 top wine blogs, we employ an advanced textual analysis tool (LIWC) to categorize the writings according to the following characteristics: analytical thinking, clout, authenticity, and emotional tone. This data is then used in a clustering procedure that distinguishes four distinct groups of bloggers: the Analysts, the Agnostics, the Authentic Pessimists, and the Confident Optimists.  相似文献   
100.
The aim of inspection planning tasks is to ensure the generation of efficient operation for coordinate measurement machines (CMMs). This paper presents a methodology to automatically define the accessibility domain of measurement points and then group them into a set of clusters. The methodology uses the computer-aided design (CAD) model of the workpiece and tolerance information as input to an algorithm for defining points accessibility. For each measurement point, the algorithm determines all feasible inspection probe orientations, as a subset of the total set of available orientations for a given CMM probe. A heuristic algorithm then groups the measurement points into a set of clusters which provide the maximum number of probe orientations. This methodology was applied to three examples which contain solid model and free-form surface representations.  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