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   307784篇
  免费   18360篇
  国内免费   9498篇
电工技术   13216篇
技术理论   24篇
综合类   16060篇
化学工业   49571篇
金属工艺   17622篇
机械仪表   17314篇
建筑科学   19667篇
矿业工程   8010篇
能源动力   7458篇
轻工业   16876篇
水利工程   4823篇
石油天然气   16921篇
武器工业   1649篇
无线电   33808篇
一般工业技术   42570篇
冶金工业   15317篇
原子能技术   2485篇
自动化技术   52251篇
  2024年   999篇
  2023年   3811篇
  2022年   6512篇
  2021年   9132篇
  2020年   7105篇
  2019年   6034篇
  2018年   20084篇
  2017年   19912篇
  2016年   15973篇
  2015年   9434篇
  2014年   11489篇
  2013年   13473篇
  2012年   17202篇
  2011年   24350篇
  2010年   21290篇
  2009年   17906篇
  2008年   18794篇
  2007年   19303篇
  2006年   12463篇
  2005年   11918篇
  2004年   8323篇
  2003年   7357篇
  2002年   5999篇
  2001年   4982篇
  2000年   5606篇
  1999年   6505篇
  1998年   5489篇
  1997年   4485篇
  1996年   4240篇
  1995年   3517篇
  1994年   2826篇
  1993年   1973篇
  1992年   1549篇
  1991年   1248篇
  1990年   934篇
  1989年   740篇
  1988年   546篇
  1987年   337篇
  1986年   278篇
  1985年   196篇
  1984年   139篇
  1983年   114篇
  1982年   124篇
  1981年   98篇
  1980年   70篇
  1968年   47篇
  1966年   43篇
  1965年   48篇
  1955年   64篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
研究了两种比活度的131Ⅰ-MIBG在正常及利血平抑制后在鼠体内的分布,结果表明:注射后4h,正常鼠心肌对3.22TBq/g的MIBG摄取为9.08%ID/g,明显高于对18.5GBq/g的摄取(4.87%ID/g)。计算表明,比活度主要影响了鼠心肌交感神经囊泡内摄取,而与囊泡外摄取无关.当MIBG用于心肌显像时,高比活度的MIBG有利于诊断。  相似文献   
12.
A distributed problem solving system can be characterized as a group of individual cooperating agents running to solve common problems. As dynamic application domains continue to grow in scale and complexity, it becomes more difficult to control the purposeful behavior of agents, especially when unexpected events may occur. This article presents an information and knowledge exchange framework to support distributed problem solving. From the application viewpoint the article concentrates on the stock trading domain; however, many presented solutions can be extended to other dynamic domains. It addresses two important issues: how individual agents should be interconnected so that their resources are efficiently used and their goals accomplished effectively; and how information and knowledge transfer should take place among the agents to allow them to respond successfully to user requests and unexpected external situations. The article introduces an architecture, the MASST system architecture, which supports dynamic information and knowledge exchange among the cooperating agents. The architecture uses a dynamic blackboard as an interagent communication paradigm to facilitate factual data, business rule, and command exchange between cooperating MASST agents. The critical components of the MASST architecture have been implemented and tested in the stock trading domain, and have proven to be a viable solution for distributed problem solving based on cooperating agents  相似文献   
13.
14.
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms.  相似文献   
15.
16.
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General Motors Corporation is reviewed.  相似文献   
17.
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated by using the proposed procedure.  相似文献   
18.
19.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry  相似文献   
20.
本文评价了塑料闪烁片用作软β核素探测器时的计数效率、β谱、本底谱和康普顿电子谱的特征。文中强调:采用胶合光导剂构成的系统是一种新型探测器(软β核素内部样品塑料闪烁探测器)。本文提出内部样品固体探测器、胶合光导剂和胶合闪烁光导剂的新概念。  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