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   24569篇
  免费   2718篇
  国内免费   1346篇
电工技术   1658篇
技术理论   2篇
综合类   1970篇
化学工业   4081篇
金属工艺   1216篇
机械仪表   1493篇
建筑科学   2004篇
矿业工程   658篇
能源动力   565篇
轻工业   2594篇
水利工程   544篇
石油天然气   1305篇
武器工业   223篇
无线电   2608篇
一般工业技术   2750篇
冶金工业   963篇
原子能技术   336篇
自动化技术   3663篇
  2024年   128篇
  2023年   499篇
  2022年   983篇
  2021年   1343篇
  2020年   976篇
  2019年   718篇
  2018年   808篇
  2017年   918篇
  2016年   824篇
  2015年   1234篇
  2014年   1408篇
  2013年   1656篇
  2012年   1824篇
  2011年   1880篇
  2010年   1654篇
  2009年   1504篇
  2008年   1497篇
  2007年   1318篇
  2006年   1322篇
  2005年   1116篇
  2004年   710篇
  2003年   645篇
  2002年   624篇
  2001年   548篇
  2000年   478篇
  1999年   439篇
  1998年   322篇
  1997年   279篇
  1996年   240篇
  1995年   169篇
  1994年   136篇
  1993年   94篇
  1992年   85篇
  1991年   48篇
  1990年   51篇
  1989年   38篇
  1988年   30篇
  1987年   22篇
  1986年   12篇
  1985年   9篇
  1984年   11篇
  1983年   3篇
  1982年   7篇
  1981年   5篇
  1980年   3篇
  1979年   3篇
  1978年   3篇
  1974年   3篇
  1959年   2篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP.  相似文献   
2.
Bulletin of Engineering Geology and the Environment - Bio-cementation is currently applied to solidify sandy soils, but only few studies use it to cement loess soil particles. In this study, the...  相似文献   
3.
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased.  相似文献   
4.
针对传统PET材料不具备抗菌、不耐洗等问题,以煎煮法为基础,以草珊瑚、艾叶和薄荷为原料,制备含植物活性成分的溶液,其具有抗菌、杀菌的作用;以溶胶-凝胶法为多孔材料制备方法,用十六烷基三甲基溴化铵、十二烷基苯磺酸钠表面活性剂为模板剂,正硅酸乙酯为有机硅源,氨水为催化剂,乙醇和乙醚为助溶剂,在水-乙醇-乙醚体系中合成多孔二氧化硅微球;然后,多孔二氧化硅微球与提取液混合制备含植物活性成分的多孔二氧化硅分子巢;最后以制备的多孔二氧化硅分子巢与普通的聚酯切片用熔融纺丝工艺进行造粒、纺丝,得到具有抗菌、杀菌和耐洗的多功能涤纶纤维.通过SEM微观观察和力学性能测试、抗菌试验、耐洗性测试,对上述制备的多功能涤纶纤维性能进行验证.结果表明:在模板剂总浓度为0.029 mol·L-1、V醇:V醚=20:20、两种表面活性剂比为4:1时,得到的多孔SiO2微球排列规整;当多孔二氧化硅分子巢掺量(质量分数)在0.5%~1%时,通过熔融共混纺丝得到的新型多功能涤纶纤维力学性能表现最优;当多孔二氧化硅分子巢掺量(质量分数)在1%时,得到的新型多功能涤纶纤维的抗菌性能达到87.9%.而二氧化硅分子巢掺量越高,纤维材料越耐洗.以上结果说明本试验制备涤纶纤维的方案可行.  相似文献   
5.
At present, the development and implementation of digital transformation are the keys to promoting high-quality industry development. The new digital fabrication method of robotic 3D printing is a research area being studied by many to tackle the issue of the declining productivity of traditional construction methods. Although many studies have been done, most of the current 3D printing projects are facing limitations in terms of scale. In order to bridge the gap, this article proposed a mass customization 3D printing framework system for large-scale projects. This article discusses how mass customization is made possible through the joint operation of the FUROBOT software and 3D printing hardware. By taking the east gate of Nanjing Happy Valley Plaza as a case study, the article demonstrates and studies the feasibility of the large-scale mass customization 3D printing framework system.  相似文献   
6.
Zhang  Miao  Chen  Luwang  Yao  Duoxi  Hou  Xiaowei  Zhang  Jie  Qin  Hao  Ren  Xingxing  Zheng  Xin 《Mine Water and the Environment》2022,41(3):775-789

Coal mining can dramatically change hydrogeological conditions and induce serious environmental problems. Fifty groundwater samples were collected from the main aquifers in the Yuaner coal mine (Anhui Province, China). The results show that the main hydrogeochemical processes in the mine include dissolution, precipitation, pyrite oxidation, desulfurization, and cation exchange. The Neogene porous aquifer is affected by groundwater flow conditions; its main hydrogeochemical processes are dissolution of carbonate minerals and gypsum, and cation exchange. The Permian coal measure’s fractured sandstone aquifer was confirmed to be controlled by the region’s geological structure; its main hydrogeochemical processes are desulfurization and cation exchange. The Carboniferous Taiyuan limestone aquifer was determined by both groundwater flow conditions and regional geological structure; its main hydrogeochemical processes are dissolution of carbonate minerals and gypsum, pyrite oxidation, and cation exchange. Additionally, hydrogeochemical inverse modeling of the groundwater flow path confirm the hydrochemistry results and principal component analysis.

  相似文献   
7.
李杉  林丹  张洁  曾海生  马秀梅 《广州化工》2022,50(5):62-64+76
优化桂枝总黄酮的提取工艺,建立桂枝的提取和含量测定方法。通过单因素试验,考察提取方法、提取溶剂浓度、提取体积、提取时间对药材总黄酮含量的影响,采用正交试验,优化提取工艺条件,筛选出桂枝总黄酮的最佳提取工艺。总黄酮最佳提取工艺为75%乙醇、料液比1:40、回流提取时间60 min。该方法能有效测定桂枝药材总黄酮的含量,为该药材的质量标准研究提供一定的科学依据。本方法重复性较好、方法稳定、可行。  相似文献   
8.
9.
高光谱激光雷达谱位合一的角度效应分析   总被引:1,自引:0,他引:1  
高光谱激光雷达以其谱位合一的技术优势为实现超三维精准遥感观测提供了可行途径,因此成为当前激光雷达与高光谱遥感领域共同大力推进的前沿发展方向。目前已有多型原型系统研发出来并得到了原理性验证,然而针对其数据处理核心环节问题的基础技术仍较为欠缺。典型问题之一是不同波段回波信号受激光入射角度的影响,该角度效应限制了高光谱激光雷达实现高性能遥感。以芬兰空间信息研究所高光谱激光雷达原型系统扫描桦树树干为例探讨了该角度效应,发现了不同激光波段对不同入射角度的回波强度响应模式,推导出了角度效应的基本规律及其精细尺度的统计规律,为后续该方向的系统研发、数据处理及信息提取等提供了可借鉴的底层机理与技术基础。  相似文献   
10.
Yogurt preserves and enhances nutritional value of milk. In this study, we have compared several strains to determine the physicochemical, sensory, rheological and aroma characteristics of different yogurts. We used Lactobacillus gasseri LGZ 1029 (LG), commercial probiotic L. rhamnosus (LGG) and traditional fermentation strains Streptococcus thermophilus and L. bulgaricus (SL). Results showed that the flavour and texture characteristics of mixed-strain yogurts were obviously better than in single-strain yogurts. Addition of LG increased pseudoplastic behaviour, as shown by Herschel–Bulkley model analysis of rheological behaviour. The LG + SL group also had both the highest viscosity consistency index and thickening ability. In addition, a total of 57 volatile compounds were detected in yogurts and the fermentation with the addition of LG was mainly affected by ketones. Our study suggested that a yogurt with new attributes can be produced by using LGZ 1029.  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