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   3600篇
  免费   434篇
  国内免费   193篇
电工技术   199篇
综合类   468篇
化学工业   454篇
金属工艺   68篇
机械仪表   177篇
建筑科学   366篇
矿业工程   78篇
能源动力   131篇
轻工业   494篇
水利工程   135篇
石油天然气   130篇
武器工业   16篇
无线电   107篇
一般工业技术   900篇
冶金工业   76篇
原子能技术   12篇
自动化技术   416篇
  2024年   10篇
  2023年   54篇
  2022年   84篇
  2021年   123篇
  2020年   119篇
  2019年   128篇
  2018年   119篇
  2017年   161篇
  2016年   153篇
  2015年   142篇
  2014年   172篇
  2013年   255篇
  2012年   207篇
  2011年   210篇
  2010年   149篇
  2009年   198篇
  2008年   204篇
  2007年   217篇
  2006年   210篇
  2005年   185篇
  2004年   167篇
  2003年   143篇
  2002年   121篇
  2001年   95篇
  2000年   89篇
  1999年   71篇
  1998年   58篇
  1997年   56篇
  1996年   60篇
  1995年   29篇
  1994年   38篇
  1993年   27篇
  1992年   31篇
  1991年   20篇
  1990年   29篇
  1989年   15篇
  1988年   9篇
  1987年   12篇
  1986年   8篇
  1985年   12篇
  1984年   9篇
  1983年   8篇
  1982年   4篇
  1980年   4篇
  1965年   1篇
  1964年   1篇
  1961年   1篇
  1960年   1篇
  1959年   1篇
  1958年   1篇
排序方式: 共有4227条查询结果,搜索用时 31 毫秒
1.
2.
Characteristics of sheep milk are of great interest for the dairy industry, as almost the totality of production is intended for cheesemaking. However, the existing relationships between these variables are complex. This study assessed composition, hygienic quality, coagulation properties, and curd yield of 1,200 individual Manchega sheep milk samples. The aim was to compare the effect of composition and hygienic quality on coagulation and curdling, and to evaluate the relationship between curd yields and the coagulation process and the effect of other features by using path analysis methodologies. Outcomes proved path analysis to be a useful and effective tool to assess these relationships through direct and indirect paths within the same model. Results showed that the factors that had a direct influence on milk coagulation were lactose concentration, casein content, and initial pH of milk. Contrastingly, somatic cells did not seem to have any effect (direct or indirect) on the coagulation process. Factors that directly affected curd yield were fat content, lactose concentration, casein content, and curd moisture. However, technological parameters showed little effect over curd yield.  相似文献   
3.
We study the problem of source reconstruction for a linear elasticity problem applied to seismicity induced by mining. We assume the source is written as a variable separable function f(x)g(t). We first present a simple proof a local decay result for elasticity in the case of homogeneous media. We then extend the source time reversal method, originally developed for acoustic waves, to an elastic system of waves. Additionally, we present a fast reconstruction implementation for large data sets. This is especially useful in the elastic case, in which the numerical cost is higher than in fluid acoustics. We complement this work with several 2D and 3D numerical experiments and an analysis of the results.  相似文献   
4.
A comprehensive study of the macrobenthic communities in the Kodungallur–Azhikode Estuary (KAE) was conducted during 2009–2011 period. A total of 18,846 organisms were collected, with 60% being malacostracans, followed by polychaetes (20%), molluscs (9%) and ‘others’ group (11%). A total of 79 species in 71 genera belonging to 49 families were identified, with 33 spp. being polychaetes, 26 spp. being malacostracans, 11 spp. being molluscs and 9 spp. being in the ‘others’ group. A single species of opportunistic amphipod (Americorophium triaeonyx) comprised more than 62.05% of the total numerical abundance of macrobenthos. The other dominant species were Obelia bidentata, Arcuatula senhousia, Cirolana fluviatilis, Prionospio cirrifera and Capitella sp. Canonical correspondence analysis (CCA) results indicated environmental parameters such as water column salinity, turbidity, sediment Eh, substratum type, chlorophyll‐a concentration, depth and organic matter in sediment were the significant factors influencing the distribution of macrobenthic species in the KAE. The present study provides baseline information for future KAE benthic studies.  相似文献   
5.
Honey acceptability is mainly determined by its colour, crystallisation degree and aroma. In the present work, the sensory characteristics and physicochemical parameters of Argentinean honeys from different ecoregions were analysed. Moisture content, Pfund colour, diastase activity, hydroxymethylfurfural content, electrical conductivity, sugar profile and volatile compounds were analytically determined in honey samples, while sensory characteristics (crystal size, fluency score, sweetness, persistence, granularity, crystallisation, colour intensity and aroma) were evaluated by a trained panel. Significant correlations were found between honey crystallisation degree and hydroxymethylfurfural content and diastase activity ( 0.05). It could be confirmed that honey crystallisation interferes with the visual perception of colour. Floral, fresh fruit, ripe fruit, balsamic and wood aromas could be successfully linked to honey volatile profile ( 0.05). These results demonstrate that the parameters that could best guarantee the consumers’ preference can be successfully associated with the chemical composition of honey by multivariate statistical analysis.  相似文献   
6.
为研究行走弹性对工程车辆行走换挡过程的影响,建立了考虑驱动轮轮胎变形引起的车辆行走弹性影响的整车行走动力学模型,该模型适用于换挡过程分析。计算与分析了典型装载机动力换挡过程,将考虑或不考虑行走弹性时计算得到的整车加速度和瞬时冲击度的变化过程分别进行了对比,利用实车试验对单一换挡过程进行了验证;并将考虑行走弹性时升挡过程中变速箱输入输出转速变化过程、离合器滑摩功率特性的计算结果与不考虑行走弹性时换挡过程的计算结果进行了对比。研究结果表明:与不考虑行走弹性的情况相比,行走弹性变形使得换挡过程中整车加速度的变化更加平缓;换入挡离合器有两次滑摩过程,冲击度更小,换挡时间更长;离合器接合时的冲击度与其接入时间有关;滑摩功更小。  相似文献   
7.
8.
9.
Objective evaluation methods for the elasticity, smoothness, and softness of cooked udon noodles were established on the basis of texture analysis. Noodles with different diameters and amylose contents were prepared to verify the reliability of the proposed evaluation methods. Results revealed that the elasticity of udon noodles could be examined by using the method that involved rinsing cooked noodles with 10°C cold water for 30 s and stretching a single strand of cooked noodle at 3 mm/s with an A/KIE probe until broken. The stiffness of the sample at 3.5 mm could be determined to indicate the elasticity caused by the size of dried udon noodles. The softness and smoothness of cooked udon noodles could be examined when cooled and drained for 30 s by using an heavy duty platform/pasta firmness/stickiness rig probe. The elasticity of cooked udon noodles increased as their diameter increased, and their smoothness and softness significantly increased as the amylose content decreased (p < .05). Texture analysis could be used to quickly and accurately indicate the elasticity, softness, and smoothness of cooked udon noodles. The texture characteristics of udon noodles were related to their formulation, processing, and size. Establishing an adaptability evaluation method for the quality of udon noodles is a prerequisite for optimizing processing technologies and developing new products. Thus far, limited research has focused on objective methods for evaluating the texture of cooked udon noodles. This work developed valuable instrumental methods for examining the elasticity, softness, and smoothness of cooked udon noodles and provided noodle manufacturers a tool for selecting udon noodle formulations and processing technology based on texture analysis.  相似文献   
10.
针对实体产业对科技资源的服务需求,以服务效应作为资源文本分类标准,提出一种基于多元神经网络融合的分布式资源空间文本分类模型。设计了包含词嵌入层、卷积层、双向门控循环单元层、注意力机制层和softmax层的多元神经网络通路;在此基础上采用基于需求—效应—资源分类策略,完成了从定性科技资源需求到定量资源服务效应求解,再到定性科技资源输出的映射变换,重点解决了分布式科技资源局部和全局语义特征形式多样、文本长距离依赖特征显著、重要资源信息难以准确识别的问题,进而从分布式科技资源空间中快速准确地获取效应知识,提升实体产业产品研发效率和创新能力;通过万方专利科技资源数据集验证了所提方法的可行性和有效性,为更加全面地挖掘资源文本特征和按需服务实体产业提供了一种新的思路和手段。  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