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   8300篇
  免费   741篇
  国内免费   684篇
电工技术   452篇
综合类   811篇
化学工业   204篇
金属工艺   267篇
机械仪表   687篇
建筑科学   505篇
矿业工程   130篇
能源动力   85篇
轻工业   130篇
水利工程   222篇
石油天然气   112篇
武器工业   119篇
无线电   481篇
一般工业技术   529篇
冶金工业   392篇
原子能技术   18篇
自动化技术   4581篇
  2024年   42篇
  2023年   81篇
  2022年   147篇
  2021年   182篇
  2020年   173篇
  2019年   141篇
  2018年   140篇
  2017年   152篇
  2016年   227篇
  2015年   267篇
  2014年   462篇
  2013年   464篇
  2012年   512篇
  2011年   593篇
  2010年   514篇
  2009年   577篇
  2008年   579篇
  2007年   576篇
  2006年   619篇
  2005年   507篇
  2004年   446篇
  2003年   384篇
  2002年   326篇
  2001年   255篇
  2000年   208篇
  1999年   171篇
  1998年   163篇
  1997年   130篇
  1996年   110篇
  1995年   104篇
  1994年   99篇
  1993年   89篇
  1992年   65篇
  1991年   60篇
  1990年   36篇
  1989年   35篇
  1988年   21篇
  1987年   14篇
  1986年   8篇
  1985年   4篇
  1984年   4篇
  1982年   4篇
  1979年   3篇
  1965年   3篇
  1964年   2篇
  1962年   2篇
  1961年   3篇
  1959年   2篇
  1957年   3篇
  1955年   3篇
排序方式: 共有9725条查询结果,搜索用时 31 毫秒
11.
The effects of case libraries on problem solving   总被引:3,自引:0,他引:3  
Abstract The purpose of the study was to investigate the effects of providing access to a case library of related stories while undergraduates solved ill-structured problems. While solving complex food product development problems, the experimental group accessed experts' stories of similar, previously solved problems; the comparable group accessed fact sheets (expository representation of stories' content); and the control group accessed text selected at random from a textbook dealing with issues unrelated to the stories. On multiple-choice questions assessing processes related to problem solving (prediction, inferences, explanations, etc.), experimental students out-performed the comparable and control groups. Performance on short-answer questions also assessing problem-related skills was not significantly different, in part because of test fatigue. Analysis of interviews identified a number of factors that students used in deciding how to apply their study strategies, including causal factors, grounding phenomenon, grounding in context, and outcomes.  相似文献   
12.
Hemispheric involvement in reasoning abilities has been debated for some time, and it remains unclear whether the right hemisphere's involvement in problem solving is modality specific or dependent on the type of spatial reasoning required. In the current study, 2 types of nonverbal reasoning abilities were examined, spatial reasoning and proportional reasoning, in 109 patients with cerebrovascular disease that was confined to either the right or the left hemisphere or was diffuse in nature. Results indicated that no lateralizing effects were present based on type of spatial reasoning. Findings are consistent with the suggestion that higher order cognitive processes involved in nonverbal abstraction and problem solving are not strongly lateralized to the right hemisphere but rather are more generally distributed throughout the cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
13.
本文主要讨论现代箱包设计的风格定位及其流行趋势。  相似文献   
14.
言明正 《包装工程》1993,14(1):35-39
论述了平板玻璃包装技术改进对提高包装质量和企业经济效益的影响,介绍了平板玻璃包装箱(架)的性能,简述了计算机辅助设计及计算机辅助管理在玻璃包装结构设计及包装质量管理中的效用。  相似文献   
15.
16.
在进行各种电子实验、研制电子产品的过程中 ,信号源及各种测量仪表是必不可少的。DDS- 1型多功能电子实验箱即可满足这方面的需要。它自备 5路电源 ,能产生多种标准的模拟信号和数字信号 ;同时可方便地用来对各种信号的幅度、频率、工作状态等进行测量和显示 ;具有宽阔的实验操作平台、手提式机箱及组装式平面结构 ,使用、维护、携带均很方便。本文介绍该实验箱的功能、原理及设计特点。  相似文献   
17.
常减压蒸饱装置几起典型硫腐蚀事例分析   总被引:1,自引:1,他引:0  
随着高(含)硫原油加工量的增加,硫腐蚀事故也时有发生。通过对常减压装置硫腐蚀事例进行分析,指出合理的混炼比,加强“一脱三注”管理,材料升级和实施腐蚀监测是防止腐蚀事故发生的有效措施。  相似文献   
18.
19.
Recent psychological research has investigated how people assess the probability of an indicative conditional. Most people give the conditional probability of q given p as the probability of if p then q. Asking about the probability of an indicative conditional, one is in effect asking about its acceptability. But on what basis are deontic conditionals judged to be acceptable or unacceptable? Using a decision theoretic analysis, we argue that a deontic conditional, of the form if p then must q or if p then may q, will be judged acceptable to the extent that the p & q possibility is preferred to the p & not-q possibility. Two experiments are reported in which this prediction was upheld. There was also evidence that the pragmatic suitability of permission rules is partly determined by evaluations of the not-p & q possibility. Implications of these results for theories of deontic reasoning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
20.
This paper presents a method of solving planning problems that involve actions whose effects change according to the situations in which they are performed. The approach is an extension of the conventional planning methodology in which plans are constructed through an iterative process of scanning for goals that are not yet satisfied, inserting actions to achieve them, and introducing subgoals to these actions. This methodology was originally developed under the assumption that one would be dealing exclusively with actions that produce the same effects in every situation. The extension involves introducing additional subgoals to actions above and beyond the preconditions of execution normally introduced. These additional subgoals, called secondary preconditions, ensure that the actions are performed in contexts conducive to producing the effects we desire. This paper defines and analyzes secondary preconditions from a mathematically rigorous standpoint and demonstrates how they can be derived from regression operators.  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