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   1623239篇
  免费   41941篇
  国内免费   14404篇
电工技术   44584篇
技术理论   14篇
综合类   17266篇
化学工业   299199篇
金属工艺   72488篇
机械仪表   50992篇
建筑科学   60243篇
矿业工程   16157篇
能源动力   55200篇
轻工业   113898篇
水利工程   17581篇
石油天然气   47564篇
武器工业   1485篇
无线电   215179篇
一般工业技术   293308篇
冶金工业   148686篇
原子能技术   35615篇
自动化技术   190125篇
  2022年   15765篇
  2021年   23034篇
  2020年   17178篇
  2019年   19105篇
  2018年   19032篇
  2017年   19073篇
  2016年   25538篇
  2015年   24000篇
  2014年   37378篇
  2013年   98432篇
  2012年   44621篇
  2011年   56993篇
  2010年   51309篇
  2009年   59806篇
  2008年   51709篇
  2007年   47969篇
  2006年   52786篇
  2005年   45808篇
  2004年   45388篇
  2003年   44801篇
  2002年   43506篇
  2001年   39943篇
  2000年   38861篇
  1999年   38354篇
  1998年   42155篇
  1997年   38325篇
  1996年   35839篇
  1995年   31813篇
  1994年   29733篇
  1993年   29078篇
  1992年   26922篇
  1991年   23581篇
  1990年   23815篇
  1989年   22744篇
  1988年   21012篇
  1987年   19243篇
  1986年   18478篇
  1985年   21691篇
  1984年   22073篇
  1983年   20046篇
  1982年   19155篇
  1981年   19208篇
  1980年   17747篇
  1979年   18289篇
  1978年   17546篇
  1977年   16829篇
  1976年   17066篇
  1975年   15798篇
  1974年   15329篇
  1973年   15397篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Three kinds of ethylene-octene copolymers (POE) were melt-blended with high-density polyethylene (PE-HD) in different proportions. Detailed characterizations were conducted to analyze their structural differences of POE and its effects in toughening PE-HD. The higher molecular weight POE can improve the toughness of PE-HD. 60:40 PE-HD/POE is elongated to break up to 700% while impact strength is 84.7 kJ/m2 at −30°C, which is 21-fold of PE-HD. In the brittle to ductile transition (BDT) during impact, the fracture mechanism changes from the crazing mode to the shear yield-plastic deformation mode. The BDT temperature decreases as the POE molecular weight and its content increase. The interface strength in tension is estimated to access their effects. The Boltzmann-type models were successfully extended to describe the typical S-shaped curves in BDT of notched impact strength vs POE content or temperature. The supplementary decay model is suggested for the attenuation in toughening. Transition map in impact is proposed to select the use range of composition (c ) and temperature (T ) for high toughness. The curves are converted into 3D graph of T -c -impact strength for illustrating their coupling-separate effects, and further into the contour map of impact strength in T -c space for finding their partial equivalence.  相似文献   
992.
993.
994.
995.
996.
Consumer studies and market reports show an increase in consumption of ready‐to‐eat (RTE) foods. Although conventional processing technologies can in most cases produce safe products, they can also lead to the degradation of nutritional compounds and negatively affect quality characteristics. Consumers strongly prefer food that is minimally processed with the maximum amount of health‐promoting substances. Novel processing technologies as pre‐ or post‐treatment decontamination methods or as substitutes of conventional technologies have the potential to produce foods that are safe, rich in nutrient content and with superior organoleptic properties. Combining novel with conventional processes can eliminate potential drawbacks of novel technologies. This review examines available scientific information and critically evaluates the suitability and efficiency of various novel thermal and nonthermal technologies in terms of microbial safety, quality as well as nutrient content on the production of RTE meals, meats and pumpable products.  相似文献   
997.
Neural Computing and Applications - More and more enterprises hope to achieve cooperation and win–win. However, many companies often have problems such as insufficient partner credit, which...  相似文献   
998.
Pokutnyi  S. I.  Dzyuba  V. P.  Amosov  A. V. 《Semiconductors》2019,53(16):2045-2048
Semiconductors - The optical properties of dielectric nanostructures strongly depend on dielectric nanoparticles (NP) polarizability which can take the high values even interacting with...  相似文献   
999.
International Journal of Mechanics and Materials in Design - The resonant frequency of electromechanical energy harvester should be tuned to ambient frequency so as to maximize the harvester power....  相似文献   
1000.
Sanad  M. H.  Marzook  F.  Saleh  G. M.  Farag  A. B.  Talaat  H. M. 《Radiochemistry》2019,61(4):478-482
Radiochemistry - Azathioprine, an antitumor agent, was labeled with 99mTc using stannous chloride dihydrate as a reducing agent. Factors such as the amounts of the reducing agent and substrate, pH,...  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