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   1929篇
  免费   52篇
  国内免费   4篇
电工技术   75篇
化学工业   437篇
金属工艺   23篇
机械仪表   50篇
建筑科学   19篇
能源动力   60篇
轻工业   179篇
水利工程   2篇
石油天然气   3篇
无线电   201篇
一般工业技术   269篇
冶金工业   498篇
原子能技术   60篇
自动化技术   109篇
  2023年   5篇
  2022年   10篇
  2021年   37篇
  2020年   11篇
  2019年   20篇
  2018年   21篇
  2017年   22篇
  2016年   35篇
  2015年   26篇
  2014年   48篇
  2013年   103篇
  2012年   58篇
  2011年   91篇
  2010年   56篇
  2009年   80篇
  2008年   72篇
  2007年   53篇
  2006年   53篇
  2005年   49篇
  2004年   47篇
  2003年   62篇
  2002年   57篇
  2001年   47篇
  2000年   28篇
  1999年   49篇
  1998年   188篇
  1997年   114篇
  1996年   90篇
  1995年   63篇
  1994年   44篇
  1993年   51篇
  1992年   26篇
  1991年   7篇
  1990年   13篇
  1989年   27篇
  1988年   13篇
  1987年   12篇
  1986年   19篇
  1985年   16篇
  1984年   16篇
  1983年   15篇
  1982年   12篇
  1981年   11篇
  1980年   15篇
  1978年   10篇
  1977年   19篇
  1976年   22篇
  1974年   8篇
  1973年   5篇
  1970年   4篇
排序方式: 共有1985条查询结果,搜索用时 156 毫秒
1.
2.
Presently, many wind turbine generators (WTGs) are connected to the power grid. While the penetration of wind power to the power system is increasing, FIT price is decreasing. Therefore, wind generation companies want to increase the electric power output from wind farms (WFs). In this article, we propose a control technique to reduce the influence of the wake by changing a power coefficient of each WTG in a WF for the purpose of improving electric power output of WFs. We showed the optimization technique of a power coefficient of each WTG and the effect of reducing the influence of the wake using measurement data from WFs. In addition, we formulated the wake effect as a function of distance between WTGs. We verified 1% improvement of generated energy in a year compared to the conventional control method by simulation. Furthermore, we quantified the improvement of generated energy output, using the distance between WTGs and the occurrence rate of the direction of the wind as a variable.  相似文献   
3.
4.
5.
6.
7.
Journal of Superconductivity and Novel Magnetism - We theoretically study the superconductivity in hole-doped cuprate superconductors by employing a model composed of surface and bulk CuO $$_2$$...  相似文献   
8.
本文从形态学的角度通过对哈尔滨近代建筑顶部形态(屋顶突出物和女儿墙)的细部构成的归纳、抽象,概括出其母题的基本类型;并根据统计结果,得出具有普遍性的形态母题。通过对整体关系的抽象,概括出其模式的基本类型;并根据统计结果,得出具有普遍性的关系模式;在上述定量分析的基础上,结合美学原理,对其所蕴含的美学意匠作了分析。  相似文献   
9.
Although nitrate is recognized as the most common groundwater contaminant due to growing anthropogenic sources, such as agriculture in particular, its adverse effects on human and animal health are debatable. The current issue, however, is to control and reduce nitrate contamination with regards to the long residence time of groundwater within aquifers. Denitrification has recently been recognized for its ability to reduce high nitrate concentrations in groundwater. The Kakamigahara groundwater basin, Gifu prefecture, Japan, witnessed rising levels of nitrate (>12 mg/l NO(3)-N) originating from agricultural sources. Chemical analyses for the determination of major constituents of groundwater and delta(15)N of residual nitrate were performed on representative groundwater samples in order to fulfill two main objectives. One is to investigate the current situation of nitrate groundwater pollution. The second objective is to determine whether the denitrification is a potential natural mechanism, which eliminates nitrate pollution in the Kakamigahara aquifer. Agricultural nitrate contamination of groundwater was obvious from characteristically high concentrations of Ca(2+), Mg(2+), NO(3)(-) and SO(4)(2-). High nitrate concentrations were found on the eastern side of the basin in association with vegetable cultivation fields, and decreased gradually towards the west of the basin along the direction of groundwater flow. The decrease of nitrate concentration was conveniently coupled with increase of HCO(3)(-) (the heterotrophic denitrification product), pH and delta(15)N of residual nitrate (due to isotopic fractionation) from east to west. Therefore, denitrification in situ is continuously removing nitrate from the Kakamigahara groundwater system.  相似文献   
10.
Terpendole E is first natural product found to inhibit mitotic kinesin Eg5, but its inhibitory mechanism remains to be revealed. Here, we report the effects of terpendole E and 11ketopaspaline (a new natural terpendole E analogue) on the Eg5–microtubule interaction and in several Eg5 mutants. 11‐Ketopaspaline is a shunt product from terpendole E, and it shows potent inhibitory activity against the microtubule‐stimulated ATPase activity of Eg5. Unlike other Eg5 inhibitors, such as S‐trityl‐L ‐cysteine (STLC) and GSK‐1, both terpendole E and 11‐ketopaspaline only partially inhibited Eg5–microtubule interaction. Furthermore, terpendole E and 11‐ketopaspaline inhibited several Eg5 mutants that are resistant to STLC (Eg5D130A, Eg5L214A) or GSK‐1 (Eg5I299F, Eg5A356T), but with the same extent of inhibition against wild‐type Eg5. Because Eg5D130A and Eg5L214A show cross‐resistance to most known Eg5 inhibitors, which bind the L5 loop, these results suggest that terpendole E and its analogues have a different binding site and/or inhibitory mechanism to those for L5 loop‐binding type Eg5 inhibitors.  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