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   4395篇
  免费   136篇
  国内免费   10篇
电工技术   67篇
综合类   29篇
化学工业   1337篇
金属工艺   108篇
机械仪表   84篇
建筑科学   265篇
矿业工程   8篇
能源动力   73篇
轻工业   348篇
水利工程   25篇
石油天然气   1篇
无线电   257篇
一般工业技术   817篇
冶金工业   584篇
原子能技术   38篇
自动化技术   500篇
  2022年   48篇
  2021年   56篇
  2020年   46篇
  2019年   57篇
  2018年   65篇
  2017年   55篇
  2016年   94篇
  2015年   82篇
  2014年   112篇
  2013年   206篇
  2012年   170篇
  2011年   254篇
  2010年   185篇
  2009年   165篇
  2008年   194篇
  2007年   187篇
  2006年   132篇
  2005年   159篇
  2004年   132篇
  2003年   104篇
  2002年   85篇
  2001年   83篇
  2000年   85篇
  1999年   88篇
  1998年   106篇
  1997年   91篇
  1996年   72篇
  1995年   76篇
  1994年   70篇
  1993年   74篇
  1992年   70篇
  1991年   49篇
  1990年   74篇
  1989年   47篇
  1988年   45篇
  1987年   55篇
  1986年   42篇
  1985年   60篇
  1984年   54篇
  1983年   47篇
  1982年   51篇
  1981年   44篇
  1979年   44篇
  1978年   44篇
  1977年   65篇
  1976年   43篇
  1975年   42篇
  1974年   56篇
  1972年   41篇
  1970年   40篇
排序方式: 共有4541条查询结果,搜索用时 15 毫秒
101.
Objective: As emotion regulation is widely considered to be a primary motive in the misuse of alcohol, our aim in the study was to investigate whether deficits in adaptive emotion-regulation skills maintain alcohol dependence (AD). Method: A prospective study investigated whether emotion-regulation skills were associated with AD and whether these skills predicted alcohol use during and after treatment for AD. Participants were 116 individuals treated for AD with cognitive–behavioral therapy. Emotion regulation and severity of AD symptoms were assessed by self-report. Alcohol use during treatment was assessed by Breathalyzer and urine analysis for ethyl glucuronide; alcohol use during the 3-month follow-up interval was assessed by self-report. Results: Pretreatment emotion-regulation skills predicted alcohol use during treatment, and posttreatment emotion-regulation skills predicted alcohol use at follow-up, even when controlling for other predictors potentially related to emotion regulation. Among a broad range of specific emotion-regulation skills, the ability to tolerate negative emotions was the only skill that negatively predicted subsequent alcohol consumption when controlling for the other skills. Individuals in the AD sample reported significantly larger deficits in emotion-regulation skills than did those in a nonclinical control sample but significantly less than did those in a sample of individuals exclusively meeting criteria for major depressive disorder. Conclusions: Enhancement of general emotion-regulation skills, especially the ability to tolerate negative emotions, appears to be an important target in the treatment of AD. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
102.
103.
104.
This article describes laboratory experiments aimed at investigations of flow structures and related transport processes in the continuous-casting mold under the influence of an external direct current (DC) magnetic field. The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution. The experimental results presented here were obtained using a physical model operating with the room-temperature alloy GaInSn. According to the concept of the electromagnetic brake, the impact of a DC magnetic field on the outlet flow from the submerged entry nozzle (SEN) has been studied up to Hartmann numbers of approximately 400. The effect of the magnetic field on the flow structure turned out to be complex. The flow measurements do not manifest a general braking effect, which would be expected as an overall damping of the flow velocity and the related fluctuations all over the mold volume. Variations of the wall conductivity showed a striking impact on the resulting flow structures. The experiments provide a substantial database for the validation of respective numerical simulations.  相似文献   
105.
The synthesis of alternating copolymers of tetraalkylindenofluorene with bithiophene and terthiophene using Suzuki polycondensation route is reported. We report on the optical and electrochemical properties of these copolymers. AFM analysis of the microscopic morphology of thin deposits showed that the copolymer with terthiophene units produced the more ordered films, with well-defined fibrillar structures, resulting from highly-regular dense packing due to strong π–π interchain interactions, in contrast to the amorphous bithiophene copolymer. Upon testing these materials in FETs the terthienyl copolymers displayed the higher charge mobilities among the studied compounds, with values of over 10?4 cm2 V?1 s?1 being obtained.  相似文献   
106.
This paper explores the influence of two types of bath variants (Tenifer Classic and Tenifer Low Porosity) for the liquid nitrocarburising treatment technology on different types of steel (34CrAINi7, 42CrMoS4, 40CrMnNiMo, X8CrNiS18–9, EN-GJS-600 and especially 16MnCrS5, two 16MnCrS5-type steels and EN-GJS-400) with special focus on their tribological behaviour under dry conditions. A cylinder-on-plate test rig (Optimol SRV4) was employed to investigate the wear resistance of the treated materials. As one result it could be shown, that better wear resistivity under dry conditions not subsequently means harder and denser white layer.  相似文献   
107.
For a tool steel AISI D2 (1.2379) and a case hardening steel (1.7131) the opportunity of reduction processing time and improvements of final properties and dimensional stability using deep cold treatments were investigated. Hardened blocks were subjected to various combinations of single and multiple tempering steps (520 °C and 540 °C for 1.2379 and 180 °C for 1.7131 respectively) and short- as well as long-time deep cold treatments (-90 °C, -120 °C and -150 °C). The greatest dimensional stability was achieved by deep cold treatments at the lowest temperature (-150 °C) and was independent of the deep cold treatment time.  相似文献   
108.
This article provides a comprehensive overview of oxygen (17O) magnetic resonance spectroscopy and imaging, including the advantages and challenges offered by the different methods developed thus far. The physiological role and relevance of oxygen, and its participation in aerobic metabolism, are addressed to emphasize the importance of the investigations and the efforts related to these developments. Furthermore, a number of methods employed in the determination of the cerebral metabolic rate of oxygen in neural cells will be presented, focusing primarily on methodologies enabling absolute quantification.  相似文献   
109.
110.
与大多数欧洲城市相比,德国的城镇体系属于均衡发展的典范。地区的高度自治、联邦体制以及强有力的州政府使德国在两千多年的城市发展历程中,逐渐形成了大中小城市遍布全国的空间形态。这些城市都具有相似的生活质量、便捷的交通和便利的服务。基于对中小城镇的概括定义,本文将首先简要介绍城市均衡发展的历史渊源及小城镇在德国的重要作用,并举例分析一些进行中的都市化过程,随后将选取纽伦堡城市区域作为中小城镇的成功案例重点介绍,最后简要说明支持城镇发展的联邦政策规划。  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