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   1488287篇
  免费   41274篇
  国内免费   10748篇
电工技术   38415篇
技术理论   1篇
综合类   13075篇
化学工业   280676篇
金属工艺   66677篇
机械仪表   43994篇
建筑科学   49106篇
矿业工程   12779篇
能源动力   52545篇
轻工业   108694篇
水利工程   15422篇
石油天然气   39589篇
武器工业   671篇
无线电   205119篇
一般工业技术   279788篇
冶金工业   120745篇
原子能技术   34685篇
自动化技术   178328篇
  2021年   17512篇
  2020年   14217篇
  2019年   17952篇
  2018年   17187篇
  2017年   16766篇
  2016年   24216篇
  2015年   21721篇
  2014年   33992篇
  2013年   94579篇
  2012年   39129篇
  2011年   50003篇
  2010年   46668篇
  2009年   55501篇
  2008年   47088篇
  2007年   43215篇
  2006年   47805篇
  2005年   41052篇
  2004年   43074篇
  2003年   42767篇
  2002年   42763篇
  2001年   38435篇
  2000年   36428篇
  1999年   33913篇
  1998年   31138篇
  1997年   31154篇
  1996年   30234篇
  1995年   27899篇
  1994年   26514篇
  1993年   26330篇
  1992年   25528篇
  1991年   22367篇
  1990年   22815篇
  1989年   21359篇
  1988年   19780篇
  1987年   18218篇
  1986年   17547篇
  1985年   20921篇
  1984年   21518篇
  1983年   19464篇
  1982年   18649篇
  1981年   18689篇
  1980年   17293篇
  1979年   17920篇
  1978年   17192篇
  1977年   16305篇
  1976年   16186篇
  1975年   15539篇
  1974年   15112篇
  1973年   15170篇
  1972年   12725篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
971.
The {100} facet of single-crystalline TiO2(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO2(B) nanobelts from H2Ti3O7 with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO2 formula with specific capacity up to 335 mAh g−1, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g−1 after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures.  相似文献   
972.
CAR (Chimeric Antigen Receptor) T cells have demonstrated clinical success for the treatment of multiple lymphomas and leukaemias, but not for various solid tumours, despite promising data from murine models. Lower effective CAR T-cell delivery rates to human solid tumours compared to haematological malignancies in humans and solid tumours in mice might partially explain these divergent outcomes. We used anatomical and physiological data for human and rodent circulatory systems to calculate the typical perfusion of healthy and tumour tissues, and estimated the upper limits of immune cell delivery rates across different organs, tumour types and species. Estimated maximum delivery rates were up to 10 000-fold greater in mice than humans yet reported CAR T-cell doses are typically only 10–100-fold lower in mice, suggesting that the effective delivery rates of CAR T cells into tumours in clinical trials are far lower than in corresponding mouse models. Estimated delivery rates were found to be consistent with published positron emission tomography data. Results suggest that higher effective human doses may be needed to drive efficacy comparable to mouse solid tumour models, and that lower doses should be tested in mice. We posit that quantitation of species and organ-specific delivery and homing of engineered T cells will be key to unlocking their potential for solid tumours.  相似文献   
973.
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   
974.
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   
975.
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   
976.
Nochovnaya  N. A.  Shiryaev  A. A. 《Metallurgist》2019,63(7-8):742-750
Metallurgist - A forming operations for the pseudo-α titanium alloys OT4-1, OT4-1V, OT4V that are used traditionally in aviation and aerospace transport structures, and a new advanced...  相似文献   
977.
Azab  A. A.  Esmail  S. A.  Abdelamksoud  M. K. 《SILICON》2019,11(1):165-174
Silicon - Nano-crystalline powders of Zn1−xCoxO with $\left (0.0\le x\le 0.07 \right )$ have been synthesized by sol-gel method. X-ray diffraction patterns of the prepared samples confirm the...  相似文献   
978.
Journal of Mechanical Science and Technology - Skidding is a phenomenon that frequently occurs in ball–raceway contact areas of bearings and often leads to their early failure. This paper...  相似文献   
979.
980.
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