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   268359篇
  免费   27527篇
  国内免费   16004篇
电工技术   21060篇
技术理论   13篇
综合类   23205篇
化学工业   38886篇
金属工艺   16097篇
机械仪表   17873篇
建筑科学   22095篇
矿业工程   8388篇
能源动力   7808篇
轻工业   23160篇
水利工程   6282篇
石油天然气   13279篇
武器工业   2980篇
无线电   31146篇
一般工业技术   27137篇
冶金工业   10449篇
原子能技术   2987篇
自动化技术   39045篇
  2024年   1315篇
  2023年   4386篇
  2022年   8826篇
  2021年   11794篇
  2020年   8938篇
  2019年   6901篇
  2018年   7661篇
  2017年   9094篇
  2016年   7900篇
  2015年   11782篇
  2014年   14972篇
  2013年   17522篇
  2012年   20487篇
  2011年   21742篇
  2010年   19991篇
  2009年   18806篇
  2008年   18660篇
  2007年   17612篇
  2006年   16264篇
  2005年   12795篇
  2004年   8976篇
  2003年   7592篇
  2002年   7433篇
  2001年   6441篇
  2000年   5235篇
  1999年   4306篇
  1998年   2905篇
  1997年   2306篇
  1996年   2099篇
  1995年   1701篇
  1994年   1384篇
  1993年   904篇
  1992年   750篇
  1991年   549篇
  1990年   403篇
  1989年   352篇
  1988年   232篇
  1987年   172篇
  1986年   149篇
  1985年   69篇
  1984年   55篇
  1983年   48篇
  1982年   55篇
  1981年   65篇
  1980年   72篇
  1979年   32篇
  1978年   11篇
  1976年   12篇
  1959年   18篇
  1951年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels.  相似文献   
52.
53.
54.
Dy3+, Eu3+: NaLa(WO4)2 phosphors are successfully synthesized through the solid-state reaction technique. The phase-structure and morphology are measured via X-ray diffraction and energy dispersive spectrometry. The concentrations of Dy3+, Eu3+, La3+, and W6+ are measured via ICP. The absorption and excited spectra are presented, which indicate that a blue band ranging from 430 to 480 nm is suitable for excitation. Using a commercial blue LED with a wavelength of 450 nm as the excitation light source, emission spectra for samples with varying dopant concentration ratios of Dy3+ to Eu3+ are obtained, which show good tunable yellow and red emission. For the purpose of investigating white LED performance, CIE spectra and a white light photo are also presented. The results reveal that varying the dopant concentration ratio of Dy3+ to Eu3+ plays a key role in the warm-white performance. With increasing concentration of Eu3+, the correlated color temperature decreases from 4069 to 3172 K, which indicates good warm-white performance.  相似文献   
55.
The fracture behaviour and morphologies of high-strength boron steel were investigated at different temperatures at a constant strain rate of 0.1 s-1 based on isothermal tensile tests. Fracture mechanisms were also analyzed based on the relationship between microstructure transformation and continuous cooling transformation(CCT) curves. It is found that 1) fractures of the investigated steel at high temperatures are dimple fractures; 2) the deformation of high-strength boron steel at high temperatures accelerates diffusion transformations; thus, to obtain full martensite, a higher cooling rate is needed; and 3) the investigated steel has the best plasticity when the deformation temperature is 750 °C.  相似文献   
56.
A contact layer element for large deformations   总被引:1,自引:0,他引:1  
  相似文献   
57.
  Qing  Xu  Bin  Yu  Yang  Zhan  Wei  Zhao  Yu  Zheng  Jun  Ji  Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability...  相似文献   
58.
59.
Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%.  相似文献   
60.
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