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   694篇
  免费   35篇
  国内免费   2篇
电工技术   2篇
综合类   24篇
化学工业   68篇
金属工艺   2篇
机械仪表   5篇
建筑科学   15篇
矿业工程   2篇
能源动力   6篇
轻工业   254篇
水利工程   20篇
无线电   8篇
一般工业技术   11篇
冶金工业   260篇
原子能技术   1篇
自动化技术   53篇
  2024年   2篇
  2023年   14篇
  2022年   21篇
  2021年   25篇
  2020年   17篇
  2019年   23篇
  2018年   10篇
  2017年   30篇
  2016年   15篇
  2015年   17篇
  2014年   24篇
  2013年   25篇
  2012年   37篇
  2011年   51篇
  2010年   48篇
  2009年   37篇
  2008年   31篇
  2007年   38篇
  2006年   38篇
  2005年   31篇
  2004年   41篇
  2003年   27篇
  2002年   24篇
  2001年   15篇
  1999年   5篇
  1998年   4篇
  1997年   3篇
  1996年   3篇
  1995年   8篇
  1993年   3篇
  1992年   4篇
  1990年   2篇
  1989年   2篇
  1987年   1篇
  1986年   2篇
  1985年   2篇
  1982年   5篇
  1980年   1篇
  1966年   4篇
  1965年   1篇
  1964年   7篇
  1963年   3篇
  1962年   3篇
  1961年   4篇
  1960年   6篇
  1958年   2篇
  1957年   2篇
  1956年   1篇
  1955年   6篇
  1954年   4篇
排序方式: 共有731条查询结果,搜索用时 15 毫秒
21.
Growth hormone (GH) has been considered as a candidate gene for growth traits in fish. In this study, polymorphisms of the GH gene were evaluated for associations with growth traits in 282 Siniperca chuatsi individuals. Using directly sequencing, four single nucleotide polymorphisms (SNPs) were identified in GH gene, with two mutations in intron 4 (g.4940A>C, g.4948A>T), one mutation in exon 5 (g.5045T>C) and one in intron 5 (g.5234T>G). Notably, three of them were significantly associated with growth performance, particularly for g.4940A>C which was highly correlated with all the four growth traits. In conclusion, our results demonstrated that these SNPs in GH gene could influence growth performance of S.chuatsi and could be used for marker-assisted selection (MAS) in this species.  相似文献   
22.
Sorghum (Sorghum bicolor) is known as a major feedstock for biofuel production. To improve its biomass yield through genetic research, manually measuring yield component traits (e.g. plant height, stem diameter, leaf angle, leaf area, leaf number, and panicle size) in the field is the current best practice. However, such laborious and time‐consuming tasks have become a bottleneck limiting experiment scale and data acquisition frequency. This paper presents a high‐throughput field‐based robotic phenotyping system which performed side‐view stereo imaging for dense sorghum plants with a wide range of plant heights throughout the growing season. Our study demonstrated the suitability of stereo vision for field‐based three‐dimensional plant phenotyping when recent advances in stereo matching algorithms were incorporated. A robust data processing pipeline was developed to quantify the variations or morphological traits in plant architecture, which included plot‐based plant height, plot‐based plant width, convex hull volume, plant surface area, and stem diameter (semiautomated). These image‐derived measurements were highly repeatable and showed high correlations with the in‐field manual measurements. Meanwhile, manually collecting the same traits required a large amount of manpower and time compared to the robotic system. The results demonstrated that the proposed system could be a promising tool for large‐scale field‐based high‐throughput plant phenotyping of bioenergy crops.  相似文献   
23.
The objective of this study was to evaluate the effect of Spirulina and Thyme supplementation on rabbit meat during retail display. At weaning 294 rabbits were allocated to 7 different treatments (42 rabbits/treatment). Rabbits of the control group (C) received a diet without any supplementation throughout the experiment (5–11 weeks of age). The other groups were fed diets containing 5% Spirulina (S), 3% Thyme (T) or both supplements (ST) for the whole trial (5–11 weeks; treatments S, T and ST), or for a part of the growing period (8–11 weeks; treatments C–S, C–T and C–ST). Colour parameters, pH, water holding capacity and drip loss were determined on fresh and stored Longissimus dorsi muscle of 5 rabbits/treatment. Spirulina- and Thyme-supplemented diets had a significant effect on redness and yellowness of Longissimus dorsi. Drip loss was significantly reduced in C–T and T groups that also showed the highest content of α-tocopherol and n − 3 fatty acids content and the lower lipid oxidation.  相似文献   
24.
This study focuses on an emerging media multitasking phenomenon called second screening or dual screening. Employing two-wave panel-data from 19 countries, we test whether the Big Five personality traits help explain the use of an additional screen or device while watching political content on TV to discuss the program with others or to look up for additional information. Results show that extraversion positively predicts political second screening. In contrast, agreeableness and openness to new experience are negatively related to political second screening. Moreover, multilevel analysis is performed to test whether the between-country variation is related to economic, political and cultural indicators.  相似文献   
25.
26.
The aim of this article was to characterise and compare the level of environmental intelligence among university students from selected countries of Central and Eastern Europe. This was done using empirical data collected by the author in 2015. In the introduction and theoretical part of this text, the term ‘environmental intelligence’ is defined, and issues raised by modern sociologists such as M. Maffesoli and M. Archer are presented. Two hypotheses stating that respondents from Poland, Slovakia and Czech Republic have higher levels of environmental intelligence than university students from the Ukraine, and those studying natural sciences have higher levels of environmental intelligence than students of the humanities or social sciences were verified. The statistical analysis conducted in the second part of the text revealed a higher level of environmental intelligence among students from the European Union countries compared to respondents from the Ukraine. However, there were no significant differences between the level of environmental intelligence and respondents’ faculty of studies. This indicates that studying natural sciences did not contribute to a more dynamic development of environmental intelligence in students. This revelation may be disturbing, as the state of the environment cannot improve if young people cannot use and care for it responsibly.  相似文献   
27.
Status updates represent a new form of one-to-many communication which is widely used among members of social networking sites (SNS). The present study investigated the question of who in particular uses the self-presentational opportunities of this feature and which users engage in riskier self-disclosures than others. Combining questionnaire and content analysis, we related self-reports on users’ personality traits (extraversion, narcissism, self-efficacy, need to belong, need for popularity) to the actual use of Facebook status updates. Results showed that higher degrees of narcissism led to deeper self-disclosures and more self-promotional content within these messages. Users with higher need to belong disclosed more intimate information in status updates, while perceived efficacy of self-presentation was negatively related to the mass suitability of postings. Findings extend prior research on personality and SNS usage with regard to dynamic features and content differences in online self-presentation.  相似文献   
28.
The current study identified and examined perceived self-traits and behavioral traits as antecedents of online empathic experiences and prosocial behavior. Our findings suggest that perceived self-traits (i.e., self-efficacy in online relationship and self-disclosure) are strongly associated with both empathic experiences and prosocial behavior. Findings for the behavioral trait, interaction pattern of an individual, indicate that patterns of an individual's networking produce mixed results in regard to association with prosocial behavior. Bonding networking was found to positively predict prosocial behavior, while bridging networking showed a negative association with the same dependent measure. Identity discrepancy and writing activities were also found to positively affect prosocial behavior. Overall, the finding of this study indicates that perceived self-traits tend to display stronger explanatory power over both empathy and prosocial behavior than do behavioral traits.  相似文献   
29.
砚滴,历史悠远,居文房用具第七位。其材质繁多,形制各异。其中,陶瓷砚滴极其工巧,它既诠释着中国陶瓷业的发展历史,也传承了几千年的中华文明。本文首先把陶瓷砚滴的发展大致划分为四个阶段,然后分别探讨其历史背景、形制与特征。  相似文献   
30.
为了明确活化磷肥、活化钾肥在水稻田中的应用效果,于2014年在湖北省应城市进行水稻田间试验,并对水稻的农艺性状、产量、分蘖动态以及株高动态进行了分析。结果表明,将活化磷肥和活化钾肥作磷肥和钾肥施用,其田间效果与传统磷肥和钾肥相当,提高了肥料利用率,实现了矿产资源的最大化利用。该试验为活化磷肥和活化钾肥在水稻田间的应用提供了依据,对资源的可持续发展具有重要意义。  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