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   500篇
  免费   38篇
电工技术   1篇
综合类   7篇
化学工业   135篇
金属工艺   6篇
机械仪表   9篇
建筑科学   38篇
矿业工程   5篇
能源动力   17篇
轻工业   63篇
水利工程   3篇
石油天然气   3篇
无线电   21篇
一般工业技术   88篇
冶金工业   70篇
原子能技术   2篇
自动化技术   70篇
  2024年   2篇
  2023年   11篇
  2022年   16篇
  2021年   29篇
  2020年   15篇
  2019年   17篇
  2018年   18篇
  2017年   13篇
  2016年   24篇
  2015年   14篇
  2014年   17篇
  2013年   38篇
  2012年   32篇
  2011年   30篇
  2010年   15篇
  2009年   24篇
  2008年   25篇
  2007年   19篇
  2006年   18篇
  2005年   6篇
  2004年   19篇
  2003年   9篇
  2002年   16篇
  2001年   5篇
  2000年   4篇
  1999年   7篇
  1998年   8篇
  1997年   13篇
  1996年   9篇
  1995年   5篇
  1994年   6篇
  1993年   5篇
  1992年   2篇
  1991年   4篇
  1990年   5篇
  1989年   3篇
  1988年   4篇
  1987年   4篇
  1986年   4篇
  1985年   3篇
  1981年   2篇
  1980年   3篇
  1979年   3篇
  1977年   2篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1970年   1篇
  1969年   1篇
  1954年   1篇
排序方式: 共有538条查询结果,搜索用时 15 毫秒
1.
The epilepsies are a group of disorders characterised by recurrent seizures caused by episodes of abnormal neuronal hyperexcitability involving the brain. Up to 60 million people are affected worldwide and genetic factors may contribute to the aetiology in up to 40% of patients. The most common human genetic epilepsies display a complex pattern of inheritance. These are categorised as idiopathic in the absence of detectable structural or metabolic abnormalities. Juvenile myoclonic epilepsy (JME) is a distinctive and common variety of familial idiopathic generalised epilepsy (IGE) with a prevalence of 0.5-1.0 per 1000 and a ratio of sibling risk to population prevalence (lambda(s)) of 42. The molecular genetic basis of these familial idiopathic epilepsies is entirely unknown, but a mutation in the gene CHRNA4, encoding the alpha4 subunit of the neuronal nicotinic acetylcholine receptor (nAChR), was recently identified in a rare Mendelian variety of idiopathic epilepsy. Chromosomal regions harbouring genes for nAChR subunits were therefore tested for linkage to the JME trait in 34 pedigrees. Significant evidence for linkage with heterogeneity was found to polymorphic loci encompassing the region in which the gene encoding the alpha7 subunit of nAChR (CHRNA7) maps on chromosome 15q14 (HLOD = 4.4 at alpha = 0.65; Z(all) = 2.94, P = 0.0005). This major locus contributes to genetic susceptibility to JME in a majority of the families studied.  相似文献   
2.
The purpose of this study is to evaluate the effect of one abrasive cleaner, one non-abrasive cleaner and one non-abrasive alcohol-based cleaner on the lens parameter stability of the NOVALENS. Twenty-four lenses, all NOVALENS material of identical design, were cleaned 100 times each. Eight lenses were cleaned with MiraFlow (CIBA Vision), eight lenses with Optic-Free Daily Cleaner and eight lenses with the Gas Permeable Daily Cleaner (PBH). The base curve radius, center thickness and power were verified immediately before, immediately after and (per manufacturer's recommendation) 4 hours after cleaning at baseline, 25, 50, 75 and 100 cleanings. Lens toricity of approximately 0.50D was found with all three cleaners after 100 cleanings. No change in lens power or center thickness was found. It was concluded that extreme care must be taken in handling the NOVALENS due to the potential of induced warpage.  相似文献   
3.
4.
5.
In this paper, denoted a continuous function from [0,1]2 into [0,1] by f, we consider the iterative process:
  相似文献   
6.
7.
In this study some analytical methods, which have been used in oil crop breeding, are compared from the point of view of plant breeding. For oil content determination a gravimetric method, NMR and NIR have been used. Protein content has been determined by the classical Kjeldahl technique, by the Biuret method and by NIR. The results indicate that the NIR spectroscopy is specially useful in screening breeding materials. This method enables the breeder to select for several quality characters simultaneously at a high speed and at a low cost. Since NIR spectroscopy is nondestructive, the same seed lot can be used for analysis and planting. Thus it is possible to select on a large scale for single plants.  相似文献   
8.
Natural rubber vulcanizates of two formulations, with sulfur/N-cyclohexyl-2-benzothiazolesulfenamide (CBS) and tetramethylthiuram disulfide (TMTD), respectively, were analyzed by pyrolysis gas chromatography. A sulfur-selective flame-photometric detector was utilized. The main pyrolysis products were identified as CS2 and some thiophenes. The yields of the pyrolysis products from the two types of rubber were very different. The yields also varied with the curing time of the rubbers.  相似文献   
9.

Definition of the problem

The role of stories is well established in the traditions of narrative ethics and casuistry. However, from a methodological point of view, the inclusion of fictional works in moral deliberation remains yet unanswered. The paper explains the potential of dystopias for bioethics by means of selected examples and a critical reconstruction and expansion of existing approaches.

Arguments

By means of literary theories, it is proposed to include moral beliefs that motivate dystopias in coherent reflection and reasoning procedures. Furthermore, dystopia’s potential through socioculturally dense scenarios, a contemporary-historical context, and a sensitization to the moral relevance of language for bioethical research are systematically presented.

Conclusion

The methodological considerations provide, on the one hand, practical points of reference for didactic approaches and, on the other hand, for public deliberation. However, the analysis also shows that dystopias introduce their own moral positions beyond a mere illustration or warning.
  相似文献   
10.
In this focused issue on the theme of “Leveraging Values in Global Organizations”, we highlight several prevalent themes on national, organizational and individual values in the literature. We argue that many premises in the literature have been accepted as fact; yet there are still many avenues open to exploration. We present several paradoxes that are often overlooked or lead to inconsistencies in the literature on values. The five articles in this focused issue address these premises and paradoxes, presenting new challenges and opportunities, providing progress and paving the way for future research on leveraging values in global organizations. The selected articles explore values with respect to international alliances and subsidiaries of multinational organizations at the organizational level, among global managers at the group level, and among employees and inpatriates at the individual level of analysis. We trust that readers of this issue will agree that the articles provide novel insights into key issues in the established, yet dynamic, field of research on values in the context of global organizations.  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