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   413篇
  免费   9篇
电工技术   4篇
化学工业   75篇
金属工艺   5篇
机械仪表   4篇
建筑科学   13篇
矿业工程   1篇
能源动力   9篇
轻工业   26篇
水利工程   4篇
石油天然气   1篇
无线电   37篇
一般工业技术   71篇
冶金工业   124篇
原子能技术   3篇
自动化技术   45篇
  2023年   4篇
  2022年   3篇
  2021年   2篇
  2020年   3篇
  2019年   2篇
  2018年   4篇
  2017年   7篇
  2016年   4篇
  2015年   5篇
  2014年   5篇
  2013年   14篇
  2012年   13篇
  2011年   17篇
  2010年   14篇
  2009年   6篇
  2008年   14篇
  2007年   15篇
  2006年   13篇
  2005年   8篇
  2004年   13篇
  2003年   10篇
  2002年   10篇
  2001年   15篇
  2000年   11篇
  1999年   15篇
  1998年   50篇
  1997年   16篇
  1996年   12篇
  1995年   10篇
  1994年   11篇
  1993年   9篇
  1992年   7篇
  1991年   6篇
  1990年   5篇
  1989年   9篇
  1988年   4篇
  1987年   6篇
  1986年   7篇
  1985年   5篇
  1984年   5篇
  1983年   2篇
  1982年   2篇
  1979年   2篇
  1978年   4篇
  1977年   3篇
  1976年   5篇
  1971年   2篇
  1966年   2篇
  1959年   1篇
  1956年   2篇
排序方式: 共有422条查询结果,搜索用时 369 毫秒
11.
Attention deficit/hyperactivity disorder (ADHD) and conduct disorder (CD) are both disorders of childhood and adolescence that all too frequently extend into adulthood. But just what is the relationship between these two disorders? This study explores the overlap between these two disorders as they relate to juvenile delinquency; both are significant risk factors for the development of antisocial behavior. But there is more significance to the presence or absence of ADHD or CD in later antisocial behavior. Higher levels of defiant and/or aggressive behavior lead to antisocial acts as compared with lower levels of defiance and antisocial acts. Boys diagnosed with ADHD have higher felony rates than normal control boys, yet ADHD is not nearly as strong a predictor of offending behavior as is CD in study subjects. The presence of both CD and ADHD contributes to illegal behavior, and it is likely that early intervention in both disorders will reduce the prevalence of antisocial behavior.  相似文献   
12.
Directly linking air quality and watershed models could provide an effective method for estimating spatially-explicit inputs of atmospheric contaminants to watershed biogeochemical models. However, to adequately link air and watershed models for wet deposition estimates, each model’s temporal and spatial representation of precipitation needs to be consistent. We explore how precipitation implemented within the Community Multi-Scale Air Quality Model (CMAQ) model algorithms, and multiple spatially-explicit precipitation datasets that could be used to improve the CMAQ model deposition estimates, links with the standard precipitation sources used to calibrate watershed models (i.e., rain gage data) via modeled water fluxes. Simulations are run using a grid-based watershed mercury model (GBMM) in two watersheds. Modeled monthly runoff suggests that multiple resolution Parameter-elevations Regressions on Independent Slopes Model (PRISM) and National Multi-sensor Precipitation Analysis Stage IV (NPA) data generate similar monthly runoff estimates, with comparable or greater accuracy when evaluated against stream gage data than that produced by the base rain gage data. However, across longer time periods, simulated water balances using 36 km Pennsylvania State University/National Center for Atmospheric Research mesoscale model (MM5) data are similar to that of base data. The investigation also examines the implications our results, providing suggestions for linking air quality and watershed fate and transport models.  相似文献   
13.
14.
15.
人在长时间运动后的疲劳和体内存储的肌糖原的消耗密切相关,因此运动后糖原合成的速度是短时间内运动恢复的关键因素。接下来的实验有效地研究了运动后补充的营养成分对于再次运动时耐力表现的影响。  相似文献   
16.
The potential benefits of a synergistic light-water reactor (LWR) and gas-cooled fast reactor (GFR) fuel cycle were evaluated for its impact on the front-end and back-end of the fuel cycle. Comparisons were made with conventional once-through cycle (OTC) and MOX fuel cycle. Variations in the synergistic LWR/GFR fuel cycles were based on the degree of recycle in the LWR including both plutonium and reprocessed uranium with concomitant impact on used LWR fuel inventory. This provided a wide range in composition of GFR feed from low to high plutonium content with impact on transmutation/incineration within the GFR fuel cycle. Self-recycle of all actinides was modeled for the GFR with analyses demonstrating that the GFR can be sustained on and consequently accept a wide range of feed materials. Analyses were done using Monteburns along with MCNP and Origen2.2 to model a 60-year period corresponding to the anticipated lifetime of supposed contemporary LWRs and GFRs. All cycles were evaluated based on actinide total mass and isotopic inventory, radiotoxicity, heatload, and resource requirements including natural uranium and SWU. For comparison, all fuel cycles were normalized based on 1 TWHe output. Improvements in fuel cycle performance are dictated by the production and incineration of minor actinides in the GFR and their continued recycle may not be feasible due to the buildup of troublesome isotopes such as 244Cm and 252Cf. But where uranium and plutonium continue to be recycled beyond the 60-year period, the LWR/GFR cycles demonstrated order of magnitude reductions in used fuel inventories, heatload, and radiotoxicity on a per TWHe basis over LWR only cycles. The full details of the advanced fuel cycle methodology and results are presented.  相似文献   
17.
18.
This work, using an adult anthropomorphic phantom, aimed to establish an optimised technique for ladies of child-bearing age undergoing antero-posterior (AP) pelvis and AP and lateral lumbar spine examinations. Phase one of the work involved introducing the following dose-reducing measures individually: increased kVp, increased focus-film distances, a carbon fibre cassette, a faster film/screen combination. The second phase established an optimised technique based on a combination of the parameters listed above. Radiation dose was measured using thermoluminescent dosimeters and image quality was evaluated using anatomical criteria. All dose-reducing methods were compared with a standard technique, currently being used in a Dublin hospital. The results demonstrated that the optimised procedure reduced effective dose by 77, 62 and 66% for AP pelvis and AP and lateral lumbar spine respectively (p < 0.05) compared with the standard technique, with no significant changes in image quality. Dose-reducing measures used in combination offer substantial potential for optimisation of radiological procedures.  相似文献   
19.
The Pool Project     
This article reviews the early days of an Australian public broadcaster's open studio Web project. It raises important issues for software developers and Web media makers about the need for software and collaborative structures that can facilitate community building in an open and responsive way. This project could be of interest to software developers working in Drupal.  相似文献   
20.
Provisions for citizen involvement in the assessment of potential environmental effects of certain plans, programmes and projects are present in current legislation. An international survey revealed that public participation is common practice in European and some other countries worldwide. However, a number of issues are observed to affect public involvement in EIA/SEA processes and expert opinion differs when evaluating the effectiveness of existing participative methods.Results suggest that technology-aided methods can improve traditional participation processes. In particular, GIS has the potential to increase community knowledge and enhance involvement by communicating information more effectively. Variable accessibility to technology and data quality remain issues. Combining technology with more conventional ways of gathering, evaluating and presenting data are seen as offering a solution to the need to promote the integration of public perceptions in environmental assessment procedures. Recommendations to improve current public participation methods and measures for making GIS available to the general public are provided.  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