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   788篇
  免费   10篇
  国内免费   7篇
电工技术   44篇
综合类   3篇
化学工业   227篇
金属工艺   24篇
机械仪表   13篇
建筑科学   13篇
能源动力   28篇
轻工业   61篇
石油天然气   2篇
无线电   82篇
一般工业技术   120篇
冶金工业   51篇
原子能技术   30篇
自动化技术   107篇
  2022年   6篇
  2021年   5篇
  2020年   3篇
  2019年   3篇
  2018年   6篇
  2017年   5篇
  2016年   4篇
  2015年   5篇
  2014年   12篇
  2013年   39篇
  2012年   21篇
  2011年   33篇
  2010年   15篇
  2009年   35篇
  2008年   38篇
  2007年   28篇
  2006年   37篇
  2005年   28篇
  2004年   28篇
  2003年   43篇
  2002年   37篇
  2001年   16篇
  2000年   11篇
  1999年   17篇
  1998年   35篇
  1997年   22篇
  1996年   29篇
  1995年   24篇
  1994年   17篇
  1993年   19篇
  1992年   15篇
  1991年   19篇
  1990年   14篇
  1989年   12篇
  1988年   8篇
  1987年   19篇
  1986年   14篇
  1985年   15篇
  1984年   6篇
  1983年   3篇
  1982年   8篇
  1981年   4篇
  1980年   10篇
  1979年   4篇
  1978年   5篇
  1977年   10篇
  1976年   6篇
  1975年   3篇
  1974年   2篇
  1973年   2篇
排序方式: 共有805条查询结果,搜索用时 31 毫秒
711.
As the background of our study, we requested that practitioners use muscle hardness testers to conduct a digital assessment of muscle hardness layers that they can feel by palpation. We developed muscle hardness testers to assess muscle hardness digitally from the reaction force and the depth in pushing a finger-shaped indenter, thereby simulating palpation. To assess muscle hardness digitally, we proposed this means using the reaction force and depth that are measured when the indenter is pushed, along with the elastic constant, and the differential elastic modulus. The tester is designed to be useful to ascertain effects of, or follow the course of, muscle layer treatment applied for shoulder stiffness and other conditions. As described herein, we confirmed the effectiveness of digital assessment using foam rubber consisting of an upper layer and a lower layer, respectively simulating the cortical and muscle layers of a human body. Additionally, monitoring six subjects, we digitally assessed the change of hardness of the trapezius muscle by changing the position of the upper extremity. Next, we were able to measure the change of hardness before and after treatment for 21 subjects with shoulder stiffness.  相似文献   
712.
713.
The microstructure of ZrO2-Y2O3 alloys prepared by arc-melting was examined mainly by electron microscopy. It was found that the microstructure changed markedly with yttria content between 0 and 8·7 mol%. Pure zirconia was a single monoclinic phase, while ZrO2-8·7 mol% Y2O3 alloy was single cubic phase as expected from ZrO2-Y2O3 phase diagram. Tetragonal phase was found in alloys with 1 to 6 mol% Y2O3 together with monoclinic or cubic phase. The tetragonal phase found in present alloys normally had a lenticular shape with a length 1 to 5m and a width 0.1 to 0.3m, which is much larger than that formed by annealing. The phase with a herring-bone appearance was found in alloys with Y2O3 between 2 and 3 mol%, which was recognized to be a metastable rhombohedral phase. The structure of the present alloys is likely to be formed by martensitic or bainitic transformation during fairly rapid cooling from the melt temperature. The change in hardness and toughness with yttria content of the alloys is discussed on the basis of microstructural observations.  相似文献   
714.
This paper addresses the flexible job shop scheduling problem (fJSP) with three objectives: min makespan, min maximal machine workload and min total workload. We developed a hybrid genetic algorithm (GA) for the problem. The GA uses two vectors to represent solutions. Advanced crossover and mutation operators are used to adapt to the special chromosome structure and the characteristics of the problem. In order to strengthen the search ability, individuals of GA are first improved by a variable neighborhood descent (VND), which involves two local search procedures: local search of moving one operation and local search of moving two operations. Moving an operation is to delete the operation, find an assignable time interval for it, and allocate it in the assignable interval. We developed an efficient method to find assignable time intervals for the deleted operations based on the concept of earliest and latest event time. The local optima of moving one operation are further improved by moving two operations simultaneously. An extensive computational study on 181 benchmark problems shows the performance of our approach.  相似文献   
715.
The vehicle routing problem with simultaneous pick-up and deliveries, which considers simultaneous distribution and collection of goods to/from customers, is an extension of the capacitated vehicle routing problem. There are various real cases, where fleet of vehicles originated in a depot serves customers with pick-up and deliveries from/to their locations. Increasing importance of reverse logistics activities make it necessary to determine efficient and effective vehicle routes for simultaneous pick-up and delivery activities. The vehicle routing problem with simultaneous pick-up and deliveries is also NP-hard as a capacitated vehicle routing problem and this study proposes a genetic algorithm based approach to this problem. Computational example is presented with parameter settings in order to illustrate the proposed approach. Moreover, performance of the proposed approach is evaluated by solving several test problems.  相似文献   
716.
With the rapid development of container transport industry, container terminal systems have become more and more busy. Some measures and facilities are taken to improve the container throughput, such as Mega Ship, Mega Crane, Deep water Port, Automatic Container Terminal, Mobile Port, Dock Type Berth and Floating Berth. This paper deals with the transshipment transport problem in a container terminal arising from the usage of Mega Ship. We introduce the Berth Allocation Planning problem considering transshipment of ship to ship and formulate a mathematical model with different number of Quay Cranes in berth. A hybrid multistage operation-based Genetic Algorithm (h-moGA) with a priority-based encoding method is proposed. To demonstrate the effectiveness of the proposed h-moGA approach, numerical experiments are carried out and the best solution to the problem is obtained.  相似文献   
717.
A new concept of smart processing is proposed that can produce advanced materials and components by finely controlling processing energy and engineering structures. New functional components of 3D photonic crystals and fractals are demonstrated, which are constructed of dielectric ceramics and a polymer using a CAD/CAM stereolithography system. By modifying the structure of diamond-like photonic crystals using free-form fabrication, electromagnetic waves can be controlled, opening the way for new applications in communication and sensing technology. The photonic fractal, a new material that can strongly localize electromagnetic waves without reflection and transmission, will also lead to new applications in the energy and medical fields.  相似文献   
718.
Thermal dissociation of blocked aliphatic isocyanates was investigated. It was found that the degree of dissociation is much affected by the structure of the isocyanates and blocking agents. These results were able to be related to the electron densities and to the thermal dissociation calculated by computer simulation.  相似文献   
719.
An investigation was undertaken on the adsorption and desorption properties of the expanded poly (tetrafluoroethylene) (ePTFE) films grafted with 2‐(dimethylamino)ethyl methacrylate (DMAEMA) to anionic dye anions with one to three sulfonic groups in response to temperature changes. The amount of adsorbed metanil yellow (MY) anions increased with the grafted amount and most of the dimethylamino groups appended to the grafted PDMAEMA chains worked as an adsorption site to MY anions for the DMAEMA‐grafted ePTFE (ePTFE‐g‐PDMAEMA) films with the grafted amounts of higher than 1.1 mmol/g. When the dye‐anion‐adsorbed ePTFE‐g‐PDMAEMA films were alternately immersed in water at two different temperatures, dye anions were desorbed from the ePTFE‐g‐PDMAEMA films at higher temperatures without any chemical agents. The amount of desorbed dye anions increased with an increase in the temperature of water from 40 to 80°C. Desorption of dye anions is caused by either deprotonation of dimethylamino groups appended to the grafted PDMAEMA chains or thermosensitive contraction of the grafted PDMAEMA chains. These results indicate that the ePTFE‐g‐PDMAEMA films can be applied as a regenerative ion‐exchange membrane for adsorption and desorption processes of anionic compounds in response to the temperature change. The thermally regenerative ion‐exchange properties of the ePTFE‐g‐PDMAEMA films was superior to that of the PE‐g‐PDMAEMA films reported in our previous article in the fact that the total degree of desorption was higher for the ePTFE‐g‐PDMAEMA films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007  相似文献   
720.
Summary Trimethylsilyl iodide in conjunction with zinc iodide (Me3SiI/ZnI2) as an initiating system led to living cationic polymerization of isobutyl vinyl ether in toluene at 0 or –40°C or in methylene chloride at –40°C (ZnI2 was dissolved in acetone). The number-average molecular weight of the polymers was directly proportional to monomer conversion and in excellent agreement with the calculated value assuming that one polymer chain forms per unit trimethylsilyl iodide. At room temperature (+25°C), however, the polymerization failed to give perfectly living polymers; the polymer molecular weight was smaller than the calculated value. On addition of a fresh feed of monomer at the end of the polymerization at –40°C, the added feed was smoothly polymerized at nearly the same rate as in the first stage, and the polymer molecular weight continued to increase in direct proportion to monomer conversion. Throughout the reaction, the molecular weight distribution of the polymers stayed very narrow (Mw/Mn< 1.1).Living cationic polymerization of vinyl ethers by electrophile/Lewis acid initiating systems, part 2. For part 1 see ref. 2  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