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   63292篇
  免费   6600篇
  国内免费   3853篇
电工技术   5923篇
技术理论   4篇
综合类   5589篇
化学工业   4848篇
金属工艺   2898篇
机械仪表   4783篇
建筑科学   12229篇
矿业工程   2421篇
能源动力   1994篇
轻工业   3529篇
水利工程   3350篇
石油天然气   4164篇
武器工业   1388篇
无线电   4630篇
一般工业技术   5578篇
冶金工业   2284篇
原子能技术   650篇
自动化技术   7483篇
  2024年   247篇
  2023年   793篇
  2022年   1694篇
  2021年   2008篇
  2020年   2272篇
  2019年   1767篇
  2018年   1687篇
  2017年   2230篇
  2016年   2424篇
  2015年   2626篇
  2014年   4062篇
  2013年   3797篇
  2012年   4880篇
  2011年   5040篇
  2010年   3810篇
  2009年   3817篇
  2008年   3451篇
  2007年   4132篇
  2006年   3734篇
  2005年   3288篇
  2004年   2712篇
  2003年   2241篇
  2002年   1927篇
  2001年   1650篇
  2000年   1342篇
  1999年   1107篇
  1998年   899篇
  1997年   692篇
  1996年   679篇
  1995年   559篇
  1994年   419篇
  1993年   296篇
  1992年   265篇
  1991年   170篇
  1990年   164篇
  1989年   127篇
  1988年   77篇
  1987年   54篇
  1986年   45篇
  1985年   26篇
  1984年   30篇
  1981年   25篇
  1980年   64篇
  1979年   47篇
  1965年   26篇
  1964年   35篇
  1959年   32篇
  1958年   23篇
  1956年   29篇
  1955年   34篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
11.
根据我院专用测试设备计量确认现状及需求,对开展试飞专用测试设备计量确认工作的要求,步骤、确认原则,以及编定计量确认方法进行了必要的讨论分析。  相似文献   
12.
This paper gives a tutorial overview of basic approaches for model validation and model structure determination.Work partially supported by the Swedish Research Council for Engineering Sciences under contract 98-654.  相似文献   
13.
文章探讨了GB 12437-2000标准规定的产品检验项目中,中包浸水试验的科学性问题和对批产品进行抽样时的样本代表性问题以及使用多段爆速仪测试爆速时应注意的样本量问题.  相似文献   
14.
Gomatofu (sesame tofu) is one of the traditional Japanese healthy foods and is representative of all shojin (vegetarian) dishes. Gomatofu, one of the mixed gels consisting of kudzu (arrowroot) starch and sesame, possesses an extremely unusual textural characteristic which is soft, smooth, and springy. The textural properties are greatly influenced by preparation, ingredients and roasting conditions of sesame seeds. Hence there are many kinds of sesame materials which can be used to prepare gomatofu such as white, black, huskless or not and roasted or unroasted sesame materials, in this study, the effects of these materials on the physical properties of gomatofu were studied. The sample of Ra-W prepared with unroasted huskless sesame seed had the least hardness, but mouthfeel of this sample were the highest. The samples of Ro-B and Ro-W prepared with roasted husk (black and white) sesame seed were evaluated to have the best palatability because of their superior springiness. It was clarified that different kinds of sesame materials affected the forming of structure and physical properties of gomatofu, because the chemical components were different from varieties of sesame materials.  相似文献   
15.
中兴宽带线路测试技术及功能介绍   总被引:1,自引:0,他引:1  
宽带线路测试是中兴通讯ZXDSL综合宽带运维系统的核心功能,在DSL业务提供过程中主要应用在开通前的预测试、线路测试、开通后的例测试以及故障时的在线测试。对其测试技术和功能作了介绍。  相似文献   
16.
Thin hard coatings fracture propagation during the impact test   总被引:2,自引:0,他引:2  
One of the most significant applications of the impact test is to investigate thin hard coatings fatigue properties. Herein the test conditions and duration up to the film damage initiation, are considered in order to determine the critical stresses associated with the coating fatigue strength. Moreover, the subsequent film damage propagation is a significant mechanism as well, since it refers to the ability of the coating to withstand loads after its fatigue damage initiation. In order to describe the film fracture propagation the failed area ratio was introduced and an algorithm to determine this magnitude developed, based on the analysis of imprint scanning electron microscopy graphs. The application of the coating failed area ratio will be demonstrated in various impact test film cases, also with superficial thin layers. The top layers do not affect, in general, the failure initiation of the basic coating. However, according to the obtained results, the superficial films influence the basic coating failure propagation rate during the impact test.  相似文献   
17.
方华 《天津冶金》2003,(6):20-22
通过对国内外大量石油套管螺纹参数的测量和全尺寸的模拟试验,以及对测量和试验数据的理论分析,找出了影响国产套管发生粘扣的原因,并在实际生产中实施验证。采取相应的措施改善了套管的抗粘结性能,同时套管的密封和抗滑脱性能并未下降。  相似文献   
18.
介绍了天铁炼钢厂中间包水模实验原理和过程,分析了斜、直、圆三种型式挡渣墙模拟结果,提出了合理的挡渣控流方案,在生产实践中使用效果良好。  相似文献   
19.
In this paper we design an experiment which can be depicted as a simple scenario, a very limited 'world'. In this world, there are an actor that can pursue a project and an observer that is keeping its eyes on the actor. We try to show in the experiment that the observer can to some degree understand the actor based on its knowledge and some metaphors, i.e. understand what the actor is doing and why. As the conclusion of this experiment, we try to show some features of 'understanding'. These are (1) that 'understanding' has to be based on some preliminary knowledge; (2) that 'understanding' is a process of incremental learning; (3) that, as for symbolic systems, some metaphors are necessary for mapping real entities into concepts in mind.  相似文献   
20.
The author tested the hypothesis that a history of drug-induced antagonism of alcohol impairment would enhance alcohol tolerance in humans. Groups of participants (N = 21) repeatedly performed a psychomotor task under different drug treatments: 0.65 g/kg alcohol, 4 mg/kg caffeine, or both drugs combined. Tolerance to a 0.65 g/kg alcohol dose challenge was then tested. Results showed that a history of combined alcohol and caffeine administrations increased alcohol tolerance compared with an exposure history to either drug alone. The findings contribute to the understanding of the complexities of polydrug use history and provide a useful model to examine how alcohol tolerance might be affected by a history of coadministration with other drugs (e.g., cocaine and nicotine). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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