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   164729篇
  免费   18631篇
  国内免费   8507篇
电工技术   52093篇
技术理论   6篇
综合类   14337篇
化学工业   7320篇
金属工艺   3858篇
机械仪表   6717篇
建筑科学   15179篇
矿业工程   4229篇
能源动力   9052篇
轻工业   15170篇
水利工程   6125篇
石油天然气   3137篇
武器工业   1035篇
无线电   17374篇
一般工业技术   6794篇
冶金工业   5371篇
原子能技术   2363篇
自动化技术   21707篇
  2024年   899篇
  2023年   2527篇
  2022年   4462篇
  2021年   5412篇
  2020年   5817篇
  2019年   4725篇
  2018年   4322篇
  2017年   5620篇
  2016年   5910篇
  2015年   6598篇
  2014年   11963篇
  2013年   9655篇
  2012年   12748篇
  2011年   13698篇
  2010年   10265篇
  2009年   10486篇
  2008年   10042篇
  2007年   11818篇
  2006年   10467篇
  2005年   8394篇
  2004年   7040篇
  2003年   5958篇
  2002年   4896篇
  2001年   3891篇
  2000年   3248篇
  1999年   2454篇
  1998年   1624篇
  1997年   1288篇
  1996年   1208篇
  1995年   954篇
  1994年   796篇
  1993年   518篇
  1992年   447篇
  1991年   293篇
  1990年   231篇
  1989年   213篇
  1988年   153篇
  1987年   129篇
  1986年   84篇
  1985年   87篇
  1984年   101篇
  1983年   87篇
  1982年   78篇
  1981年   46篇
  1980年   42篇
  1979年   24篇
  1978年   26篇
  1977年   20篇
  1975年   8篇
  1959年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
For monitoring online manufacturing processes, the proportion of weights imposed on each type of product’s defects (nonconformities or demerits) has a profoundly effective impact on control charts’ performance. Apparently, the demerit-chart approach is superior than the widely-used c-chart scheme, because it allows us to place relative precise weights (real numbers) on defects according to their distinctly inferior degrees affecting the product quality so that the abnormal variations of processes can be literally exposed. However, in many applications, the seriousness of defects is evaluated partially or entirely by the inspectors’ perceptive judgement or knowledge, so with the precise-weight assignment, the demerit rating mechanism is considered to be somewhat constrained and subjective which inevitably leads to the targeted manufacturing process with limited and possibly biased information for online surveillance. To cope with the drawback, a demerit-fuzzy rating system and monitoring scheme is proposed in this paper. We first incorporate fuzzy weights (fuzzy numbers) to properly reflect the severity measures of defects which are categorized linguistically. Then, based on properties of fuzzy set theory and proposed approaches for fuzzy-number ranking, we develop the demerit-fuzzy charting scheme which is capable of discriminating process conditions into multi-intermittent statuses between in-control and out-of-control. This approach improves the traditional process control techniques with the binary-classification restraint for the process conditions. Finally, the proposed demerit-fuzzy rating system, monitoring scheme, and classification is elucidated by an application in garment industry to monitor textile-stitching nonconformities conditions.  相似文献   
982.
Association rule mining is a data mining technique for discovering useful and novel patterns or relationships from databases. These rules are simple to infer and intuitive and can be easily used for classification in any domain that requires explanation for and investigation into how the classification works. Examples of such areas are medicine, agriculture, education, etc. For such a system to find wide adoptability, it should give output that is correct and comprehensible. The amount of data has been growing very fast and so has the search space of these problems. So we need to change traditional methods. This paper discusses a rule mining classifier called DA-AC (dynamic adaptive-associative classifier) which is based on a Dynamic Particle Swarm Optimizer. Due to its seeding method, exemplar selection, adaptive parameters, dynamic reconstruction of regions and velocity update, it avoids premature convergence and provides a better value in every dimension. Quality evaluation is done both for individual rules as well as entire rulesets. Experiments were conducted over fifteen benchmark datasets to evaluate performance of proposed algorithm in comparison with six other state-of-the-art non associative classifiers and eight associative classifiers. Results demonstrate competitive performance of proposed DA-AC while considering predictive accuracy and number of mined patterns as parameters. The method was then applied to predict life expectancy of post operative thoracic surgery patients.  相似文献   
983.
Research has been carried out to ascertai the effects of different processing systems on olive oil quality. Tests were performed in industrial oil mills that were equipped with both pressure and centrifugation systems. Results show that oils extracted from good-quality olives do not differ in free fatty acids, peroxide value, ultraviolet absorption and organoleptic properties. Polyphenols ando-diphenols contents and induction times are higher in oils obtained from good-quality olives by the pressure system because it does not require addition of water to the olive paste. The centrifugation system requires the addition of warm water to the olive paste and helps to obtain oils with a lower content of natural antioxidants. Oils obtained from poorquality or from ripe olives in continuous centrifugal plants are lower in free fatty acids than those obtained by the pressure system. Dr. Mario Solinas is deceased—May 23, 1993.  相似文献   
984.
介绍南京水泥工业设计研究院用预分解生产技术对山东水泥厂Φ4×60m预热器窑烧成系统进行的成功技术改造。技改设计指标为:熟料产量保证指标1500t/d,争取指标1700t/d,熟料热耗<3762kJ/kg,熟料28d抗压强度>60MPa。整个工程停产施工耗时仅用48d,烧成系统技改共耗资约3000万元。技改后一次点火投料成功,且点火当月即实现72h达标考核,所有设计指标均达标。  相似文献   
985.
986.
The concentrations of 102 chemical compounds (saturated and unsaturated hydrocarbons, palmitates, total and free acids, total hydroxyacids, total and free alcohols, acidic monoesters and monoesterified 1,2,3‐propanetriols) have been determined by GC/FID on white and yellow comb beeswax of Apis mellifera from different regions of Spain. Guide‐value ranges are proposed for its characterization and to discriminate adulterated foundation beeswax sheets. The concentrations of many compounds resulted to be statistically different for white and yellow beeswaxes, while the observation of concentrations out of normal in some marketed foundation beeswax sheets suggested their adulteration. However, the measurement of anomalous concentrations in foundation beeswax sheets did not imply necessarily their rejection by the bees.  相似文献   
987.
预焙阳极的质量已严重制约铝电解技术的发展,必须予以足够的重视.国外在提高阳极质量方面的有效措施,可以供国内阳极工厂技术改造及科研攻关借鉴.  相似文献   
988.
纳米材料在涂料中的应用   总被引:1,自引:0,他引:1  
简述了纳米微粒的基本性质,介绍了几种典型的功能纳米材料在涂料中的应用.并探究其对涂料的改性原理.对应用中存在的问题进行了剖析。  相似文献   
989.
成绍鑫 《腐植酸》2007,(1):1-11
我国土壤污染形势严峻,已成为农产品安全和农业可持续发展的一大障碍."十一五"期间已将防治土壤污染列入重要议事日程,"全国土壤污染状况调查和防治项目"业已启动,2006年11月<农产品质量安全法>也开始实施.腐植酸学术界及行业又面临新的机遇和挑战.介绍了我国土壤污染的现状及其治理技术,阐述了腐植酸类物质(HS)修复污染土壤的研究进展、存在问题及应用的可行性,并对今后的研究开发及应用方向提出若干建议.  相似文献   
990.
介绍了海绵钛的主要特点、用途、质量及生产方法。  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