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   129801篇
  免费   13109篇
  国内免费   7496篇
电工技术   10284篇
技术理论   7篇
综合类   10077篇
化学工业   18827篇
金属工艺   8209篇
机械仪表   8445篇
建筑科学   10508篇
矿业工程   3701篇
能源动力   4013篇
轻工业   8545篇
水利工程   2922篇
石油天然气   6523篇
武器工业   1506篇
无线电   15730篇
一般工业技术   14435篇
冶金工业   5824篇
原子能技术   1656篇
自动化技术   19194篇
  2024年   566篇
  2023年   1910篇
  2022年   3546篇
  2021年   5158篇
  2020年   3806篇
  2019年   3050篇
  2018年   3416篇
  2017年   4054篇
  2016年   3745篇
  2015年   5230篇
  2014年   6583篇
  2013年   7790篇
  2012年   9287篇
  2011年   9803篇
  2010年   9133篇
  2009年   8673篇
  2008年   8708篇
  2007年   8254篇
  2006年   7872篇
  2005年   6549篇
  2004年   4889篇
  2003年   4456篇
  2002年   4706篇
  2001年   4129篇
  2000年   2962篇
  1999年   2617篇
  1998年   1721篇
  1997年   1512篇
  1996年   1404篇
  1995年   1121篇
  1994年   904篇
  1993年   650篇
  1992年   552篇
  1991年   416篇
  1990年   296篇
  1989年   242篇
  1988年   196篇
  1987年   135篇
  1986年   90篇
  1985年   63篇
  1984年   46篇
  1983年   34篇
  1982年   42篇
  1981年   27篇
  1980年   25篇
  1979年   13篇
  1978年   4篇
  1975年   3篇
  1959年   7篇
  1951年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Zhang  Miao  Chen  Luwang  Yao  Duoxi  Hou  Xiaowei  Zhang  Jie  Qin  Hao  Ren  Xingxing  Zheng  Xin 《Mine Water and the Environment》2022,41(3):775-789

Coal mining can dramatically change hydrogeological conditions and induce serious environmental problems. Fifty groundwater samples were collected from the main aquifers in the Yuaner coal mine (Anhui Province, China). The results show that the main hydrogeochemical processes in the mine include dissolution, precipitation, pyrite oxidation, desulfurization, and cation exchange. The Neogene porous aquifer is affected by groundwater flow conditions; its main hydrogeochemical processes are dissolution of carbonate minerals and gypsum, and cation exchange. The Permian coal measure’s fractured sandstone aquifer was confirmed to be controlled by the region’s geological structure; its main hydrogeochemical processes are desulfurization and cation exchange. The Carboniferous Taiyuan limestone aquifer was determined by both groundwater flow conditions and regional geological structure; its main hydrogeochemical processes are dissolution of carbonate minerals and gypsum, pyrite oxidation, and cation exchange. Additionally, hydrogeochemical inverse modeling of the groundwater flow path confirm the hydrochemistry results and principal component analysis.

  相似文献   
23.
Li  Yuru  Wang  Fei  Zheng  Zhaowen 《Neural Processing Letters》2022,54(4):3141-3156
Neural Processing Letters - This paper presents an approach to identify the unknown parameters of genetic regulatory network (GRN) in finite-time. The adaptive synchronization-based method is used...  相似文献   
24.
25.
Illumination is essential for modern life as colorful world is perceived by human visionary system. Display technology has been developing rapidly in recent decades, and the basic principle is related to the way that the image is illuminated and light is emanated. Traditional illumination is provided by different types of light sources, and the display image is visible in large viewing space until the emanating light decays to zero. This work proposes and demonstrates a novel illumination scheme for a display in which the displaying images are visible only in specific spatial regions. The directional backlight ensures the image propagating to specific direction while imaging visibility can be controlled to terminate abruptly at certain distance from the display screen while exerting no influence to nearby regions. The working principle for such an illumination scheme is the use of the modulated coherent directional backlight through an axicon lens. It is shown that the illumination scheme can robustly deliver carried image information to the designated viewing region. This new illumination scheme has many advantages over conventional illumination, including its usage for personal display, very lower energy consumption, as well as minimizing light hazard pollution.  相似文献   
26.
27.
Yan  Jing  Zhu  Rongying  Wu  Fan  Zhao  Ziyin  Ye  Huan  Hou  Mengying  Liu  Yong  Yin  Lichen 《Nano Research》2020,13(10):2706-2715
Nano Research - Insufficient intratumoral penetration greatly hurdles the anticancer performance of nanomedicine. To realize highly efficient tumor penetration in a precisely and spatiotemporally...  相似文献   
28.
29.
30.
Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong built-in electric field(BEF) in strained wurtzite Zn O/Mg0:25Zn0:75O quantum dots(QDs), the optical properties of ionized donor-bound excitons(D+, X)are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of(D+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of(D+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth.  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