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   74篇
  免费   3篇
电工技术   3篇
化学工业   12篇
机械仪表   2篇
建筑科学   7篇
能源动力   1篇
轻工业   10篇
无线电   3篇
一般工业技术   7篇
冶金工业   15篇
原子能技术   6篇
自动化技术   11篇
  2023年   1篇
  2021年   6篇
  2020年   4篇
  2017年   4篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   6篇
  2012年   3篇
  2011年   3篇
  2010年   3篇
  2009年   4篇
  2008年   4篇
  2007年   5篇
  2006年   2篇
  2005年   3篇
  2004年   1篇
  2003年   1篇
  2001年   2篇
  2000年   2篇
  1999年   1篇
  1998年   3篇
  1997年   5篇
  1996年   2篇
  1995年   1篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1979年   1篇
  1977年   1篇
排序方式: 共有77条查询结果,搜索用时 15 毫秒
1.
Software Quality Journal - Energy consumption of software has been becoming increasingly significant, since it can vary according to how the software has been developed. In recent years, developers...  相似文献   
2.
Databases are the core of Information Systems (IS). It is, therefore, necessary to ensure the quality of the databases in order to ensure the quality of the IS. Metrics are useful mechanisms for controlling database quality. This paper presents two metrics related to referential integrity, number of foreign keys (NFK) and depth of the referential tree (DRT) for controlling the quality of a relational database. However, to ascertain the practical utility of the metrics, experimental validation is necessary. This validation can be carried out through controlled experiments or through case studies. The controlled experiments must also be replicated in order to obtain firm conclusions. With this objective in mind, we have undertaken different empirical work with metrics for relational databases. As a part of this empirical work, we have conducted a case study with some metrics for relational databases and a controlled experiment with two metrics presented in this paper. The detailed experiment described in this paper is a replication of the later one. The experiment was replicated in order to confirm the results obtained from the first experiment.

As a result of all the experimental works, we can conclude that the NFK metric is a good indicator of relational database complexity. However, we cannot draw such firm conclusions regarding the DRT metric.  相似文献   

3.
4.
The role of plant polyphenols as defenses against insect herbivores is controversial. We combined correlative field studies across three geographic regions (Northern Mexico, Southern Mexico, and Costa Rica) with induction experiments under controlled conditions to search for candidate compounds that might play a defensive role in the foliage of the tropical oak, Quercus oleoides. We quantified leaf damage caused by four herbivore guilds (chewers, skeletonizers, leaf miners, and gall forming insects) and analyzed the content of 18 polyphenols (including hydrolyzable tannins, flavan-3-ols, and flavonol glycosides) in the same set of leaves using high performance liquid chromatography and mass spectrometry. Foliar damage ranged from two to eight percent per region, and nearly 90% of all the damage was caused by chewing herbivores. Damage due to chewing herbivores was positively correlated with acutissimin B, catechin, and catechin dimer, and damage by mining herbivores was positively correlated with mongolinin A. By contrast, gall presence was negatively correlated with vescalagin and acutissimin B. By using redundancy analysis, we searched for the combinations of polyphenols that were associated to natural herbivory: the combination of mongolinin A and acutissimin B had the highest association to herbivory. In a common garden experiment with oak saplings, artificial damage increased the content of acutissimin B, mongolinin A, and vescalagin, whereas the content of catechin decreased. Specific polyphenols, either individually or in combination, rather than total polyphenols, were associated with standing leaf damage in this tropical oak. Future studies aimed at understanding the ecological role of polyphenols can use similar correlative studies to identify candidate compounds that could be used individually and in biologically meaningful combinations in tests with herbivores and pathogens.  相似文献   
5.
The evaluated spectroscopic data are presented for 11 known nuclides of mass 211 (Hg, Tl, Pb, Bi, Po, At, Rn, Fr, Ra, Ac, Th). The 211Pa nuclide is included here but its identification remains uncertain. For 211Hg, 211Tl, 211Ac and 211Th nuclei, only the ground–state information is available. Their decay characteristics are mostly unknown. 211Fr is suggested to decay partially through ε decay mode, but its decay scheme remains poorly known. While high–spin excitations, including several isomers, are well studied in 211Pb, 211Bi, 211Po, 211At, 211Rn and 211Fr, the particle–transfer data are available for only 211Po and 211Bi.This evaluation was carried out as part of joint IAEA–ICTP workshop for Nuclear Structure and Decay Data, organized and hosted by the IAEA, Vienna and ICTP, Trieste, August 6–17, 2012. This work supersedes previous A=211 evaluation (2004Br45) published by E. Browne which covered literature before January 2003.  相似文献   
6.
Experimental structure and decay data for all nuclei with mass A=192 (Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, At) have been evaluated. This evaluation, covering data received by 15 June 2012, supersedes the 1998 evaluation by C. M. Baglin (Nuclear Data Sheets 84, 717 (1998), literature cutoff August 1998) and the subsequent inclusion in the ENSDF database of the new nuclide 192At (C. M. Baglin, literature cutoff 16 May 2006). It also incorporates the current evaluation of superdeformed-band information by B. Singh. Since the last publication, 192Ta, 192W and 192At have been observed, and an isomeric state has been identified in 192Re. The ε decay of 192Au has been studied using a multidetector array resulting in an extensively revised level scheme for 192Pt.  相似文献   
7.
8.
Three different types of ultraviolet lamps were tested for the advanced oxidation process application on pre-treated surface water in a pilot plant. The pilot setup consisted of three parallel reactors with either medium pressure, low pressure or dielectric barrier discharge UV lamps. Four model compounds (atrazine, bromacil, ibuprofen and N-nitroso-dimethylamine (NDMA)) and 0, 5 or 10 ppm hydrogen peroxide were dosed. Low pressure lamps were shown to have the lowest energy demand, calculated as electrical energy per order, followed by dielectric barrier discharge lamps and then medium pressure lamps. Medium pressure lamps gave the highest formation of genotoxic activity and nitrite formation, whereas no formation of genotoxic activity was observed for either of the other lamp types.  相似文献   
9.
The aim of this paper is to study the occupational segregation of immigrants in Spain. It analyzes whether age, educational level, gender, region of origin, and years of residence in Spain affect the distribution of immigrants across occupations. In addition, given the remarkable increase of immigrants in the last few years and the adjustments that have occurred in the Spanish labor market from the current economic crisis, the evolution of the occupational segregation of immigrants between 1996 and 2009 is addressed. For these purposes, several measures recently proposed in the literature are used.  相似文献   
10.
Leber hereditary optic neuropathy (LHON) is a maternally inherited disorder, associated with mutations in the mitochondrial DNA, which is notorious for its aspecific presentations. Two pedigrees are described with cases that are atypical for LHON with respect to sex, age of onset, interval between the eyes becoming affected, course of the disease, concomitant disorders, additional test results, final visual acuity, and/or results of mtDNA analysis. Moreover, the pedigrees themselves did not suggest maternal inheritance. We analysed the diagnostic and clinical genetic difficulties related to the atypical aspects of these pedigrees. We conclude that mtDNA analysis is justified in every case of optic nerve atrophy with no clear cause. Identification of one of the three LHON specifically associated mtDNA mutations is essential to confirm the diagnosis.  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