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   22216篇
  免费   2830篇
  国内免费   1291篇
电工技术   747篇
技术理论   5篇
综合类   2135篇
化学工业   981篇
金属工艺   705篇
机械仪表   754篇
建筑科学   8272篇
矿业工程   788篇
能源动力   302篇
轻工业   1201篇
水利工程   595篇
石油天然气   312篇
武器工业   110篇
无线电   1969篇
一般工业技术   2003篇
冶金工业   916篇
原子能技术   250篇
自动化技术   4292篇
  2024年   98篇
  2023年   561篇
  2022年   885篇
  2021年   958篇
  2020年   1072篇
  2019年   808篇
  2018年   551篇
  2017年   582篇
  2016年   572篇
  2015年   679篇
  2014年   1742篇
  2013年   1435篇
  2012年   1734篇
  2011年   1842篇
  2010年   1560篇
  2009年   1464篇
  2008年   1422篇
  2007年   1484篇
  2006年   1276篇
  2005年   1039篇
  2004年   915篇
  2003年   682篇
  2002年   615篇
  2001年   463篇
  2000年   346篇
  1999年   275篇
  1998年   210篇
  1997年   191篇
  1996年   166篇
  1995年   154篇
  1994年   92篇
  1993年   101篇
  1992年   60篇
  1991年   67篇
  1990年   48篇
  1989年   31篇
  1988年   33篇
  1987年   23篇
  1986年   12篇
  1985年   23篇
  1984年   24篇
  1983年   7篇
  1982年   6篇
  1981年   7篇
  1980年   6篇
  1979年   3篇
  1976年   3篇
  1975年   2篇
  1964年   2篇
  1956年   2篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
In the present investigation, systematic grinding experiments were conducted in a laboratory ball mill to determine the breakage properties of low-grade PGE bearing chromite ore. The population balance modeling technique was used to study the breakage parameters such as primary breakage distribution (Bi, j) and the specific rates of breakage (Si). The breakage and selection function values were determined for six feed sizes. The results stated that the breakage follows the first-order grinding kinetics for all the feed sizes. It was observed that the coarser feed sizes exhibit higher selection function values than the finer feed size. Further, an artificial neural network was used to predict breakage characteristics of low-grade PGE bearing chromite ore. The predicted results obtained from the neural network modeling were close to the experimental results with a correlation of determination R2 = 0.99 for both product size and selection function.  相似文献   
2.
赵勤  回璇 《包装工程》2021,42(10):323-333
目的 赣傩艺术元素内容丰富并保存完整,是研究我国古代赣傩地区文化与艺术的珍贵史料.研究赣傩艺术元素的提取及衍生图案的设计方法,在设计应用中表达赣傩傩面具、选取傩舞形和构筑傩庙魂,能给当代赣傩艺术元素的产品设计以指引.方法 通过直接引用、形意结合和局部强化的设计方法,增厚其丰富内涵、设计个性和主题意蕴.通过现代化审美中"绿色化、感性化、地域化"的要求,遵循"以退为进,化繁为简""多元并存,个性体现"的原则,强化赣傩艺术元素的独特风格.结论 用现代的手法,将特色的赣傩艺术元素植入到理性的产品设计中去,使赣傩艺术元素与现代设计思想有机结合.在继承传统文化与现代流行中找到契合点,深入挖掘赣傩艺术元素蕴含的文化精神、文化胸怀和文化自信,使中华传统文化在现代审美下进行创新再现.  相似文献   
3.
4.
Since their identification as genomic regulatory elements, Transposable Elements (TEs) were considered, at first, molecular parasites and later as an important source of genetic diversity and regulatory innovations. In vertebrates in particular, TEs have been recognized as playing an important role in major evolutionary transitions and biodiversity. Moreover, in the last decade, a significant number of papers has been published highlighting a correlation between TE activity and exposition to environmental stresses and dietary factors. In this review we present an overview of the impact of TEs in vertebrate genomes, report the silencing mechanisms adopted by host genomes to regulate TE activity, and finally we explore the effects of environmental and dietary factor exposures on TE activity in mammals, which is the most studied group among vertebrates. The studies here reported evidence that several factors can induce changes in the epigenetic status of TEs and silencing mechanisms leading to their activation with consequent effects on the host genome. The study of TE can represent a future challenge for research for developing effective markers able to detect precocious epigenetic changes and prevent human diseases.  相似文献   
5.
Understanding the mechanisms leading to the rise and dissemination of antimicrobial resistance (AMR) is crucially important for the preservation of power of antimicrobials and controlling infectious diseases. Measures to monitor and detect AMR, however, have been significantly delayed and introduced much later after the beginning of industrial production and consumption of antimicrobials. However, monitoring and detection of AMR is largely focused on bacterial pathogens, thus missing multiple key events which take place before the emergence and spread of AMR among the pathogens. In this regard, careful analysis of AMR development towards recently introduced antimicrobials may serve as a valuable example for the better understanding of mechanisms driving AMR evolution. Here, the example of evolution of tet(X), which confers resistance to the next-generation tetracyclines, is summarised and discussed. Initial mechanisms of resistance to these antimicrobials among pathogens were mostly via chromosomal mutations leading to the overexpression of efflux pumps. High-level resistance was achieved only after the acquisition of flavin-dependent monooxygenase-encoding genes from the environmental microbiota. These genes confer resistance to all tetracyclines, including the next-generation tetracyclines, and thus were termed tet(X). ISCR2 and IS26, as well as a variety of conjugative and mobilizable plasmids of different incompatibility groups, played an essential role in the acquisition of tet(X) genes from natural reservoirs and in further dissemination among bacterial commensals and pathogens. This process, which took place within the last decade, demonstrates how rapidly AMR evolution may progress, taking away some drugs of last resort from our arsenal.  相似文献   
6.
《Ceramics International》2022,48(2):1642-1658
The conditions for the preparation of the solid solutions of a binary system of barium-strontium titanates with the substitutions in the A-sublattice with the rare-earth elements (REE), including the solid-phase synthesis, mechanical activation and sintering of dispersed-crystalline products by the conventional ceramic technology, were optimized. The presence (absence) of the impurity phases was established depending on the size effect of the REE. The precision X-ray diffraction analysis revealed the features of the phase formation in the studied solid solutions and showed that the “behavior” of the structural characteristics of the solid solutions with the participation of the REE is determined by the limiting conditions of the isomorphism and anion excess of the media under study. An assumption is made about the nature of the formation of a fine-grained landscape of the modified solid solutions, associated with the multicluster structure of the crystallite structure and the formation of the ballast phases during their synthesis. The dependences of the dielectric properties of the solid-state solution on the external influences – temperature, frequency of an alternating electric field and strength of a constant field – have been established. The possibility of choosing on the basis of the obtained data, promising for practical applications of the compositions is shown.  相似文献   
7.
为了保障浓香菜籽油的产品质量安全,采用HACCP体系对浓香菜籽油生产全过程进行生物、物理、化学的危害分析,确定关键控制点,制定预防措施,并对生产环节进行有效监控,制定纠偏措施,做好记录管理,为浓香菜籽油的安全生产提供借鉴。  相似文献   
8.
在线学习已逐渐成为高职院校一种重要学习形式,该领域也成为当前研究热点之一。对在线学习进行介绍,同时对大数据技术在在线学习平台中的应用进行分析,重点对五年制高职护生在线学习行为要素进行研究分析,为更好地开展在线学习评价提供参考,促进高职院校更好地开展在线学习,提高在线学习质量。  相似文献   
9.
This paper presents a novel approach to the localization of moving targets in a complex environment based on the measurement of the perturbations induced by the target presence on an independently‐generated time‐varying electromagnetic field. Field perturbations are measured via a set of sensors deployed over the domain of interest and used to detect and track a possible target by resorting to a particle Bernoulli filter (PBF). To comply with real‐time operation, the PBF works along with an artificial neural network (ANN) model of the environment trained offline via finite elements (FEs). The performance of the proposed algorithm is assessed via simulation experiments.  相似文献   
10.
研究创新人才培养规律,探索和实践创新人才培养模式,是当前高校教育教学改革的一个重要方向。针对我校自动化专业立足国防、面向社会的人才培养特色,提出了以“创新意识、创新精神、创新技能”为核心的学生创新能力培养理念,通过构建创新能力培养“全链”模式、优化创新能力培养的“微生态”环境,取得了突出的成效。  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