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   161507篇
  免费   15704篇
  国内免费   8811篇
电工技术   10925篇
技术理论   10篇
综合类   14953篇
化学工业   25570篇
金属工艺   9068篇
机械仪表   9935篇
建筑科学   12542篇
矿业工程   4257篇
能源动力   4181篇
轻工业   17942篇
水利工程   3349篇
石油天然气   7303篇
武器工业   1596篇
无线电   17318篇
一般工业技术   16688篇
冶金工业   5948篇
原子能技术   1682篇
自动化技术   22755篇
  2024年   728篇
  2023年   2616篇
  2022年   5380篇
  2021年   6892篇
  2020年   5309篇
  2019年   4179篇
  2018年   4482篇
  2017年   5229篇
  2016年   4657篇
  2015年   6825篇
  2014年   8894篇
  2013年   10115篇
  2012年   11849篇
  2011年   12982篇
  2010年   11787篇
  2009年   11177篇
  2008年   11235篇
  2007年   10447篇
  2006年   9866篇
  2005年   7880篇
  2004年   5622篇
  2003年   4659篇
  2002年   4753篇
  2001年   3977篇
  2000年   3261篇
  1999年   2630篇
  1998年   1844篇
  1997年   1406篇
  1996年   1276篇
  1995年   989篇
  1994年   752篇
  1993年   529篇
  1992年   438篇
  1991年   339篇
  1990年   228篇
  1989年   201篇
  1988年   143篇
  1987年   99篇
  1986年   76篇
  1985年   42篇
  1984年   27篇
  1983年   31篇
  1982年   31篇
  1981年   24篇
  1980年   48篇
  1979年   19篇
  1978年   4篇
  1976年   6篇
  1959年   12篇
  1951年   11篇
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
31.
Yuan  Zhongchen  Yan  Li  Ma  Zongmin 《Requirements Engineering》2020,25(2):213-229
Requirements Engineering - In software reuse, the reuse of UML class diagram produced in design phase has received more attention due to the important influence on the following developing process....  相似文献   
32.
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   
33.
34.
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   
35.
HPL500B2型弹簧机构支架(BA)螺栓断裂可能导致开关分合闸失败,对其原因进行分析,发现BA螺栓由于预紧固力矩过大,接近其扭断力矩,使得作用在BA螺栓上的力偏高,BA螺栓安全系数仅为12%,安全系数较低。列出BA螺栓更换步骤及注意事项,并详细介绍分闸、合闸弹簧调整步骤,为类似事件的处理提供参考。  相似文献   
36.
37.
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   
38.
39.
40.
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