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   5540篇
  免费   300篇
  国内免费   13篇
电工技术   113篇
综合类   4篇
化学工业   1478篇
金属工艺   116篇
机械仪表   175篇
建筑科学   190篇
矿业工程   29篇
能源动力   202篇
轻工业   671篇
水利工程   32篇
石油天然气   20篇
武器工业   1篇
无线电   397篇
一般工业技术   1266篇
冶金工业   203篇
原子能技术   42篇
自动化技术   914篇
  2023年   52篇
  2022年   132篇
  2021年   175篇
  2020年   137篇
  2019年   132篇
  2018年   204篇
  2017年   201篇
  2016年   233篇
  2015年   187篇
  2014年   265篇
  2013年   516篇
  2012年   356篇
  2011年   388篇
  2010年   306篇
  2009年   247篇
  2008年   263篇
  2007年   214篇
  2006年   182篇
  2005年   134篇
  2004年   89篇
  2003年   103篇
  2002年   86篇
  2001年   61篇
  2000年   63篇
  1999年   59篇
  1998年   65篇
  1997年   41篇
  1996年   48篇
  1995年   45篇
  1994年   54篇
  1993年   48篇
  1992年   37篇
  1991年   36篇
  1990年   30篇
  1989年   29篇
  1988年   23篇
  1987年   32篇
  1986年   24篇
  1985年   48篇
  1984年   47篇
  1983年   37篇
  1982年   42篇
  1981年   46篇
  1980年   41篇
  1979年   37篇
  1978年   31篇
  1977年   25篇
  1976年   28篇
  1973年   27篇
  1972年   22篇
排序方式: 共有5853条查询结果,搜索用时 0 毫秒
1.
Identification of anthocyanins in the wine made of the Croatian autochthonous grape variety of Babić (Vitis vinifera L.) was carried out and their profile was determined by means of high-performance liquid chromatography with diode array and mass spectrometric detection. Dependence of anthocyanins content and profile on maceration treatment conditions was investigated. Statistically significant differences of anthocyanins concentration in wines Babić produced by various maceration treatments were confirmed by the use of multivariate analysis of variances. The investigation results indicated that the maceration temperature exerts higher influence on anthocyanins concentration than the duration of maceration. In addition, on the basis of anthocyanin composition and using different multivariate statistical analyses, differentiation of wines Babić according to maceration treatments was procured.  相似文献   
2.
3.
A procedure has been proposed for the estimation of the terminal falling velocity of non-spherical particles moving in a Carreau model fluid in the transition flow region. The procedure is based on a modification of the relationship formerly developed for the fall of spherical particles including the particle dynamic shape factor. The suitability of the proposed procedure has been confirmed by good agreement between experimental and calculated terminal falling velocity data. In the experiments, the terminal falling velocity of short cylinders and rectangular prisms in polymer solutions of different measure of shear thinning and elasticity has been measured.  相似文献   
4.
This study evaluated relations among optimism, perceived stress management skills (PSMS), and positive mood in 46 men who had surgical treatment for localized prostate cancer. The authors found that optimism, PSMS, and positive mood scores were positively correlated. Positive mood was unrelated to demographic and disease-related control variables. In a hierarchical regression model controlling for PSMS, the relationship between optimism and positive mood became nonsignificant, whereas PSMS remained a correlate of positive mood. Results suggest that the relationship between optimism and positive mood may be mediated by belief in being able to use stress management techniques effectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
5.
6.
This article is focused on the phase structure development in immiscible polymer blends during melt mixing. Nonuniformity of the phase structure, i.e., the coexistence of areas containing particles with markedly different size distribution, was detected in quenched and compression molded samples of a number of various blends prepared by long and intensive mixing in the chamber of a Plasticorder. The same effect was found also for polystyrene/polyamide blends prepared in a twin‐screw extruder. It was shown that neglecting nonuniformity of the phase structure can lead to considerable error in evaluation of the effect of system parameters on the blend morphology. The reasons for the effect were discussed and it was found that inhomogeneous flow field in mixers is a plausible explanation of the nonuniform phase structure. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers  相似文献   
7.
ZnO-based varistor samples were prepared by the direct mixing of the constituent phases (DMCP) and sintering at 1100 °C for 2 h. The influence of the starting powder mixture's composition – the amounts of the pre-reacted varistor compounds and their composition – and its preparation, either with or without mechano-chemical activation (MCA), on the microstructure, phase composition and electrical characteristics of the varistor samples was studied. It showed that MCA improved the density and microstructural homogeneity of the varistor samples. MCA strongly affected the grain growth: it enhanced the nucleation of inversion boundaries (IBs) in the ZnO grains and the IBs-induced grain-growth mechanism resulted in uniform grain growth and hence a microstructure with smaller ZnO grains and a narrower grain size distribution. The final phase composition of the samples prepared by the DMCP method mainly depended on the presence of varistor dopants that can prevent the formation of the pyrochlore phase, especially Cr2O3, while MCA can affect it mostly by providing a homogeneous distribution of those dopants. The DMCP varistor samples prepared with MCA had much better current–voltage characteristics than the samples of the same composition prepared from unactivated powders.  相似文献   
8.
A concept of business intelligent system for financial prediction is considered in this paper. It provides data needed for fast, precise and good business decision support to all levels of management. The aim of the project is the development of a new online analytical processing oriented on case-based reasoning (CBR) where a previous experience for every new problem is taken into account. Methodological aspects have been tested in practice as a part of the management information system development project of “Novi Sad Fair”. A case study of an improved application of CBR in prediction of future payments is discussed in the paper. This paper is originally presented at The International Conference on Hybrid Information Technology 2006, at the special session on “Intelligent Information Systems for Financial Engineering”, November 2006 in Cheju Island, Korea.  相似文献   
9.
Iv?n Arce of Core Security Technologies looks at the current state of malware and introduces the articles he selected for this special issue.  相似文献   
10.
This work is an experimental study of the differential scanning calorimetry characterisation of polymer materials used in food packaging materials, such as polypropylene (0.03 mm), polyethylene (0.1 and 0.03 mm), poly(D-(-)-Β-hydroxybutyrate) (powder), two-layered polypropylene (0.064 mm), and two-layered polypropylene with poly-vinylidene-chloride (0.012/0.021). The polymer stability was checked by simulation of conditions during food preparation in microwave ovens, sterilisation or rapid freezing. The materials were tested in the temperature range from 40 to 200‡C at different scan rates from 2 to 30°C min−1 during heating or cooling. The enthalpies show a high correlation coefficient (0.964) with scan rate. All samples undergo phase change in the temperature range from 107 to 173°C during heating and enthalpies are in the range from 31.8 to 71.1Jg−1. Upon subsequent cooling from 200°C, the temperature range of phase changes is shifted to lower temperatures from 86 to 102°C with enthalpies ranging from 30.4 to 57.8 J g−1. Experiments with exposure of polymers to microwave radiation and freezing prove that the phase change considering the temperature range is very similar in all experiments.  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