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   32361篇
  免费   4042篇
  国内免费   2079篇
电工技术   8419篇
技术理论   1篇
综合类   4042篇
化学工业   1096篇
金属工艺   696篇
机械仪表   2290篇
建筑科学   6563篇
矿业工程   1356篇
能源动力   1710篇
轻工业   395篇
水利工程   1851篇
石油天然气   992篇
武器工业   310篇
无线电   1432篇
一般工业技术   2319篇
冶金工业   926篇
原子能技术   139篇
自动化技术   3945篇
  2024年   185篇
  2023年   459篇
  2022年   906篇
  2021年   986篇
  2020年   1099篇
  2019年   884篇
  2018年   892篇
  2017年   1133篇
  2016年   1197篇
  2015年   1355篇
  2014年   2168篇
  2013年   1769篇
  2012年   2481篇
  2011年   2728篇
  2010年   2010篇
  2009年   2140篇
  2008年   2046篇
  2007年   2396篇
  2006年   2142篇
  2005年   1744篇
  2004年   1395篇
  2003年   1220篇
  2002年   963篇
  2001年   842篇
  2000年   677篇
  1999年   578篇
  1998年   358篇
  1997年   342篇
  1996年   313篇
  1995年   238篇
  1994年   197篇
  1993年   132篇
  1992年   90篇
  1991年   74篇
  1990年   78篇
  1989年   68篇
  1988年   64篇
  1987年   32篇
  1986年   19篇
  1985年   14篇
  1984年   15篇
  1983年   14篇
  1982年   15篇
  1981年   6篇
  1980年   6篇
  1979年   4篇
  1961年   1篇
  1957年   1篇
  1955年   1篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
针对电力系统经济负荷分配问题,提出一种有效的差分蜂群算法.受差分进化算法的启发,该算法基于差分进化操作改进了雇佣蜂的搜索方式,提高了探索能力和收敛速度.此外,提出一种有效的修复机制以保证新个体的可行性.该算法在带有阀点效应和多燃料特征的典型电力系统经济负荷分配问题上进行了测试.仿真结果验证了所提算法的有效性.  相似文献   
32.
In this note, we prove that both problems studied by Cheng et al. [Cheng, T. C. E., Hsu, C.-J., & Yang, D.-L. (2011). Unrelated parallel-machine scheduling with deteriorating maintenance activities. Computers and Industrial Engineering, 60, 602–605] can be solved in O(nm+3) time no matter what the processing time of a job after a maintenance activity is greater or less than its processing time before the maintenance activity, where m is the number of machines and n is the number of jobs.  相似文献   
33.
《Ergonomics》2012,55(2):151-162
The paper attempts to list the most important fields in which research on human factors in road transport is required.

The importance of improving the efficiency of road transport is emphasized, and the figures for road casualties are quoted to demonstrate the need to study the behaviour of cyclists, motor-cyclists and pedestrians as well as motorists.

The problems on which research is required are grouped under the six headings of perception, communication of information, control of the vehicle, comfort, protection of occupants, and behaviour of drivers. Subjects regarded as of particular interest are (1) the communication of information to the driver, (2) the design of the vehicle to improve control by the driver, (3) crash injury protection for the motorist and for the motor-cyclist, and (4) the study of the driving task.  相似文献   
34.
通过两阶段最小二乘法估测了我国玉米供需曲线,并预测未来两年均衡价格和净进口量.研究发现影响我国玉米供给的因素有玉米价格、大豆价格、技术进步和成灾率,影响我国玉米需求的因素有玉米价格、小麦价格、人均国内生产总值和总人口;预测未来两年我国玉米价格和净进口量都将呈上升趋势,我国将成为玉米净进口国.  相似文献   
35.
《Ergonomics》2012,55(2):293-305
Abstract

The literature on terminal control tasks and continuous tracking tasks suggests a possible model for tasks where the subject must guide a vehicle at his own speed along a course defined by a tolerance band. The model predicts a linear relationship between the average velocity and the width of the tolerance band. Throe experiments are described which simulate vehicle guidance by pencil-and-paper experiments for courses consisting of straight lines and circles. The predictions of the model were confirmed, suggesting that a general measure for the ease of control of a vehicle (or other controlled system) is possible using this technique.  相似文献   
36.
《Ergonomics》2012,55(10):1515-1529
The study investigated the effects of using a lower body prototype exoskeleton (EXO) on static limits of stability and postural sway. Measurements were taken with participants, 10 US Army enlisted men, standing on a force platform. The men were tested with and without the EXO (15 kg) while carrying military loads of 20, 40 and 55 kg. Body lean to the left and right was significantly less and postural sway excursions and maximal range of movement were significantly reduced when the EXO was used. Hurst values indicated that body sway was less random over short-term time intervals and more random over long-term intervals with the EXO than without it. Feedback to the user's balance control mechanisms most likely was changed with the EXO. The reduced sway and relatively small changes in sway with increasing load weights suggest that the EXO structure may have functioned to provide a bracing effect on the body.  相似文献   
37.
Financial institutions operate a supply chain where only one product is moved across the network. Although the cash is kept in several nodes to service the demand of final customers, availability causes opportunity cost related with its investment options. When planning the inventory of cash that should be maintained across the network, transportation decisions are also expected to be made. Cash transportation has a high cost, associated with the high risk of theft. Increasing the inventory can reduce the need for transportation, but the opportunity cost can be very high. Moreover, the inventory is also related with the service level perceived for final customers; therefore because of low inventory some people are not able to make some transactions. The aim of this work is to find optimal decisions related with cash inventory and transportation across the network, trying to balance the cost of the service and the quality perceived for final users.  相似文献   
38.
利用炉膛断面温度场可视化监测系统、节能环保车、炉内三维数值模拟等先进的技术和设备对大机组调峰稳定性和运行方式优化进行试验和理论研究。  相似文献   
39.
组合式空调系统设计中机组选型方法探讨   总被引:1,自引:0,他引:1  
对目前组合式空调机组在选型设计及使用中出现的问题进行了分析,运用空气处理设备选型的有关理论和计算方法,对舒适性空调系统中机组选型的一些问题和数据进行了简化和近似处理,提出了能够满足工程设计的要求的简便实用的选型方法。  相似文献   
40.
为了提高企业决策自动化管理水平,运用先进的数据仓库和数据挖掘技术,采用请求响应方式以及规范化的接口结构,提出一个企业信息分析及决策系统的设计和解决方案。根据完善的智能化分析手段,有效的保证决策者的经验与决策支持系统的分析和预测能力相结合,并对企业管理者提供科学准确的分析预测和决策支持。系统可实时地为用户提供有效详细的分析数据,从而大大加快决策进程并有效提高准确性。  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