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   32030篇
  免费   1411篇
  国内免费   35篇
电工技术   336篇
综合类   56篇
化学工业   6966篇
金属工艺   597篇
机械仪表   576篇
建筑科学   1883篇
矿业工程   77篇
能源动力   873篇
轻工业   2687篇
水利工程   295篇
石油天然气   165篇
武器工业   3篇
无线电   2286篇
一般工业技术   5913篇
冶金工业   5203篇
原子能技术   205篇
自动化技术   5355篇
  2023年   276篇
  2022年   447篇
  2021年   696篇
  2020年   504篇
  2019年   591篇
  2018年   721篇
  2017年   691篇
  2016年   907篇
  2015年   813篇
  2014年   1028篇
  2013年   1919篇
  2012年   1669篇
  2011年   2121篇
  2010年   1509篇
  2009年   1463篇
  2008年   1761篇
  2007年   1645篇
  2006年   1441篇
  2005年   1228篇
  2004年   1093篇
  2003年   945篇
  2002年   912篇
  2001年   542篇
  2000年   523篇
  1999年   532篇
  1998年   488篇
  1997年   446篇
  1996年   459篇
  1995年   439篇
  1994年   425篇
  1993年   428篇
  1992年   384篇
  1991年   229篇
  1990年   319篇
  1989年   321篇
  1988年   271篇
  1987年   296篇
  1986年   286篇
  1985年   306篇
  1984年   267篇
  1983年   256篇
  1982年   239篇
  1981年   209篇
  1980年   175篇
  1979年   182篇
  1978年   165篇
  1977年   135篇
  1976年   122篇
  1975年   134篇
  1974年   109篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
One of the fundamental questions discussed in the course of the development towards Industry 4.0 is that of responsibility for machines. The inner-juridical discussion of this issue suffers from the unclear concept of artificial intelligence and the fascination about the creation of very high technical performance while lightning-fast access to a huge amount of information or the determination of previously undiscovered correlations between individual phenomena is no indication of the appearance of the superhuman. Technicians, on the other hand, are confused about the differentiations by which lawyers approach the question of responsibility. This article aims at bridging the gap in order to strengthen the interdisciplinary dialogue.  相似文献   
992.
Synthesis of Benzo[b]thioxanthenes Benzo[b]thioxanthenes, heterocyclic compounds related to tetracenes and tetracyclines can be obtained by the reaction of 2H-benzo[b]thiete ( 1 ) and 1,4-naphthoquinones ( 3a–g ). The primary cycloadducts 4a–g undergo an autoxidation process leading to the quinones 6a–g . The dihydroxy compound 4e shows an additional isomerization by a tetrafold H transfer ( 4e → 5e ′). Another preparative route to benzo[b]thioxanthenes makes use of the cycloadditon reaction of 1 and 1,4-epoxynaphthalenes ( 7a–d ). The primary adducts can be transformed to the title compounds by catalytic dehydration processes ( 8a–d → 9a-d ). An alternate regioselective opening of the oxygen bridge can be performed by the action of trimethyliodosilane ( 8a → 10a ). Methylation of 9a furnishes the sulfonium salt 14a which rearranges in a strongly alkaline medium to 16a ; in the presence of oxygen ketone 17a is generated.  相似文献   
993.
综述了能促进消费者健康和社会安宁的纺织品的最新的技术发展.介绍了种种创新的纺织品.社会的变革和发展趋势愈来愈强调生活环境、休闲娱乐、通信以及交通等的健康与安宁的重要性.最近的技术发展增加了使纺织品获得新性能的可能性,并直接关系到使用者的健康和生活环境.纺织品作为一种柔性材料,具有悬垂性好、弹性好、易变形、强度较高、较好的染色吸附性以及其他后处理特性,可以由多种原料制成,并具有多种功能.  相似文献   
994.
995.
996.
An improved synthetic access for the construction of 4,6,7-trimethylbenzofurans ( B1–B8 ) through the one-electron oxidation of mesityl-substituted enols ( E1–E8 ) is presented. The transformation can be accomplished in good to excellent yields by using various oxidants; i.e. tris(1,10-phenanthroline)iron(III) hexafluorophosphate, FeCl3, Ce(NH4)2(NO3)6, Cu(OTf)2/Cu2O or anodic oxidation.  相似文献   
997.
998.
Maternal obesity increases the risk of health complications in offspring, but whether these effects are exacerbated by offspring exposure to unhealthy diets warrants further investigation. Female Sprague-Dawley rats were fed either standard chow (n = 15) or ‘cafeteria’ (Caf, n = 21) diets across pre-pregnancy, gestation, and lactation. Male and female offspring were weaned onto chow or Caf diet (2–3/sex/litter), forming four groups; behavioural and metabolic parameters were assessed. At weaning, offspring from Caf dams were smaller and lighter, but had more retroperitoneal (RP) fat, with a larger effect in males. Maternal Caf diet significantly increased relative expression of ACACA and Fasn in male and female weanling liver, but not CPT-1, SREBP and PGC1; PPARα was increased in males from Caf dams. Maternal obesity enhanced the impact of postweaning Caf exposure on adult body weight, RP fat, liver mass, and plasma leptin in males but not females. Offspring from Caf dams appeared to exhibit reduced anxiety-like behaviour on the elevated plus maze. Hepatic CPT-1 expression was reduced only in adult males from Caf fed dams. Post weaning Caf diet consumption did not alter liver gene expression in the adult offspring. Maternal obesity exacerbated the obesogenic phenotype produced by postweaning Caf diet in male, but not female offspring. Thus, the impact of maternal obesity on adiposity and liver gene expression appeared more marked in males. Our data underline the sex-specific detrimental effects of maternal obesity on offspring.  相似文献   
999.
Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, is overexpressed and activated in many cancer types. FAK regulates diverse cellular processes, including growth factor signaling, cell cycle progression, cell survival, cell motility, angiogenesis, and the establishment of immunosuppressive tumor microenvironments through kinase-dependent and kinase-independent scaffolding functions in the cytoplasm and nucleus. Mounting evidence has indicated that targeting FAK, either alone or in combination with other agents, may represent a promising therapeutic strategy for various cancers. In this review, we summarize the mechanisms underlying FAK-mediated signaling networks during tumor development. We also summarize the recent progress of FAK-targeted small-molecule compounds for anticancer activity from preclinical and clinical evidence.  相似文献   
1000.
随着大型彩色或黑白LCD显示屏的发展,LED技术也不断进步,可用更低的功率产生更强的光,多用作便携式或交流线路供电系统照明源。现在,白色LED能够提供与普通白炽灯泡几乎一样或更多的光源。  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