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   32957篇
  免费   3523篇
  国内免费   2146篇
电工技术   2673篇
技术理论   1篇
综合类   3035篇
化学工业   4888篇
金属工艺   1712篇
机械仪表   1995篇
建筑科学   2927篇
矿业工程   975篇
能源动力   958篇
轻工业   3051篇
水利工程   806篇
石油天然气   1274篇
武器工业   357篇
无线电   3510篇
一般工业技术   3570篇
冶金工业   1425篇
原子能技术   387篇
自动化技术   5082篇
  2024年   118篇
  2023年   487篇
  2022年   930篇
  2021年   1316篇
  2020年   1070篇
  2019年   895篇
  2018年   941篇
  2017年   1070篇
  2016年   928篇
  2015年   1375篇
  2014年   1810篇
  2013年   2035篇
  2012年   2282篇
  2011年   2427篇
  2010年   2254篇
  2009年   2124篇
  2008年   2302篇
  2007年   2128篇
  2006年   2023篇
  2005年   1507篇
  2004年   1272篇
  2003年   1231篇
  2002年   1534篇
  2001年   1333篇
  2000年   847篇
  1999年   583篇
  1998年   359篇
  1997年   325篇
  1996年   273篇
  1995年   217篇
  1994年   153篇
  1993年   89篇
  1992年   94篇
  1991年   64篇
  1990年   43篇
  1989年   41篇
  1988年   30篇
  1987年   21篇
  1986年   15篇
  1985年   6篇
  1984年   6篇
  1983年   4篇
  1982年   5篇
  1981年   9篇
  1980年   26篇
  1979年   4篇
  1978年   3篇
  1977年   3篇
  1976年   3篇
  1974年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
The esophagus is a tubular-shaped muscular organ where swallowed fluids and muscular contractions constitute a highly dynamic environment. The turbulent, coordinated processes that occur through the oropharyngeal conduit can often compromise targeted administration of therapeutic drugs to a lesion, significantly reducing therapeutic efficacy. Here, magnetically guidable drug vehicles capable of strongly adhering to target sites using a bioengineered mussel adhesive protein (MAP) to achieve localized delivery of therapeutic drugs against the hydrodynamic physiological conditions are proposed. A suite of highly uniform microparticles embedded with iron oxide (IO) nanoparticles (MAP@IO MPs) is microfluidically fabricated using the genipin-mediated covalent cross-linking of bioengineered MAP. The MAP@IO MPs are successfully targeted to a specific region and prolongedly retained in the tubular-structured passageway. In particular, orally administered MAP@IO MPs are effectively captured in the esophagus in vivo in a magnetically guidable manner. Moreover, doxorubicin (DOX)-loaded MAP@IO MPs exhibit a sustainable DOX release profile, effective anticancer therapeutic activity, and excellent biocompatibility. Thus, the magnetically guidable locomotion and robust underwater adhesive properties of the proteinaceous soft microbots can provide an intelligent modular approach for targeted locoregional therapeutics delivery to a specific lesion site in dynamic fluid-associated tubular organs such as the esophagus.  相似文献   
4.
李涛  叶青  曹国庆 《暖通空调》2020,50(1):31-36
对比分析了国内外标准有关高等级生物安全实验室通风空调系统冗余设计的要求。结合我国已有高等级生物安全实验室,重点分析了送风机、排风机、排风高效过滤器冗余设计的具体实施形式和存在的问题,给出了冗余设计原则建议。  相似文献   
5.
Yang  Xi  Gao  Ling  Guo  Qing  Li  Yongjiang  Ma  Yue  Yang  Ju  Gong  Changyang  Yi  Cheng 《Nano Research》2020,13(10):2579-2594

Over the past decade, numerous studies have attempted to enhance the effectiveness of radiotherapy (external beam radiotherapy and internal radioisotope therapy) for cancer treatment. However, the low radiation absorption coefficient and radiation resistance of tumors remain major critical challenges for radiotherapy in the clinic. With the development of nanomedicine, nanomaterials in combination with radiotherapy offer the possibility to improve the efficiency of radiotherapy in tumors. Nanomaterials act not only as radiosensitizers to enhance radiation energy, but also as nanocarriers to deliver therapeutic units in combating radiation resistance. In this review, we discuss opportunities for a synergistic cancer therapy by combining radiotherapy based on nanomaterials designed for chemotherapy, photodynamic therapy, photothermal therapy, gas therapy, genetic therapy, and immunotherapy. We highlight how nanomaterials can be utilized to amplify antitumor radiation responses and describe cooperative enhancement interactions among these synergistic therapies. Moreover, the potential challenges and future prospects of radio-based nanomedicine to maximize their synergistic efficiency for cancer treatment are identified.

  相似文献   
6.
  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   
7.
8.
Chen  Yaqi  Wu  Xiaoren  Liu  Qing  He  Maoshuai  Bai  Hongcun 《Catalysis Letters》2022,152(9):2738-2744

This work proposed a new path to synthesize Ni-phyllosilicate through the reaction of nickel hydroxide and silica sol on the surface of Ni-foam to form the monolithic Ni-phyllosilicate/Ni-foam catalyst. Ni-phyllosilicate could reprint the morphology of nickel hydroxid and firmly anchor on the framework of Ni-foam, which obtained fine Ni particles of 2.8 nm after reduction in H2 at 650 °C, resulting in high catalytic activity for CO2 methanation. In addition, the Ni-phyllosilicate/Ni-foam catalyst showed high long-term stability in a 100 h-lifetime test owing to the combined effects of surface confinement of Ni-phyllosilicate, firm anchoring between Ni-phyllosilicate and Ni-foam, as well as the high heat transfer property of Ni-foam.

Graphical Abstract
  相似文献   
9.
Based on theoretical analysis and numerical simulation, the impact of steel fibres on the stress intensity factor (SIF) at the crack tip for cementitious composite was studied. The enhanced toughness of steel fibre reinforced cementitious composite (SFRC) in resisting cracks was explained by the decrement of SIF caused by steel fibre inclusions at the crack tip of the composite. The equivalent initial fracture toughness was used to characterize the crack initiation of SFRC. A simplified method for determining the of SFRC was proposed based on a linear regression method. Fracture tests were conducted on three‐point bending notched beams with different steel fibre volume fractions and specimen sizes to study the crack initiation behaviour of aligned steel fibre reinforced cementitious composite (ASFRC). of ASFRC was calculated, and the size effect of was analysed. The results showed that slightly increased with the steel fibre volume fraction and gradually became stable. For the tested specimens, whose heights varied between 40 and 100 mm, the specimen size had little impact on the .  相似文献   
10.
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