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   3747篇
  免费   72篇
  国内免费   10篇
电工技术   161篇
综合类   2篇
化学工业   979篇
金属工艺   127篇
机械仪表   87篇
建筑科学   62篇
矿业工程   3篇
能源动力   132篇
轻工业   306篇
水利工程   12篇
石油天然气   4篇
无线电   291篇
一般工业技术   707篇
冶金工业   562篇
原子能技术   93篇
自动化技术   301篇
  2023年   16篇
  2022年   44篇
  2021年   64篇
  2020年   36篇
  2019年   58篇
  2018年   54篇
  2017年   43篇
  2016年   62篇
  2015年   55篇
  2014年   92篇
  2013年   170篇
  2012年   150篇
  2011年   166篇
  2010年   146篇
  2009年   184篇
  2008年   173篇
  2007年   162篇
  2006年   131篇
  2005年   123篇
  2004年   132篇
  2003年   114篇
  2002年   94篇
  2001年   82篇
  2000年   72篇
  1999年   89篇
  1998年   254篇
  1997年   152篇
  1996年   111篇
  1995年   78篇
  1994年   65篇
  1993年   62篇
  1992年   49篇
  1991年   56篇
  1990年   47篇
  1989年   43篇
  1988年   28篇
  1987年   43篇
  1986年   39篇
  1985年   32篇
  1984年   27篇
  1983年   20篇
  1982年   29篇
  1981年   21篇
  1980年   28篇
  1979年   28篇
  1978年   18篇
  1977年   24篇
  1976年   29篇
  1975年   7篇
  1974年   5篇
排序方式: 共有3829条查询结果,搜索用时 15 毫秒
1.
2.
3.
In right middle cerebral territory infarction a new sign, excessive closure of the right eye ipsilateral to the lesion and mild closure of the left eye on command, was noted. The excessive ipsilateral eye closure was not observed on spontaneous eye closure.  相似文献   
4.
The recent increase in the demand for power in urban areas has caused changes in the way power is supplied. Underground distribution systems have been introduced for convenience in urban areas and to prevent injuries in case of a crisis. As a result, many new types of power cables are being used. One type, XPLE cables (also called CV cables) have been rapidly taking the place of conventional cables such as OF or SL cables since the 1960s because of their relatively easy installation and maintainability. However, distribution cables used under severe environmental conditions deteriorate rapidly (due mainly to water treeing), and some cables experience insulation breakdown. Therefore, many diagnostic methods have been developed, though they have not been very effective. By combining methods, a high reliability can be achieved in comparison to the use of a single method. However, processing the data is difficult for on-site personnel, so many experts are required. But there is a lack of qualified experts, hence we have turned to the development of expert systems.  相似文献   
5.
Segregation in sputtered Co-Cr films   总被引:1,自引:0,他引:1  
The segregation growth process in sputtered Co-Cr films is investigated by examining the effect of substrate temperature on the segregated microstructure and magnetic properties. In sputtered Co-25at%Cr films, segregation occurs below 560°C, and both the saturation magnetization and the perpendicular anisotropy constant show a maximum around a substrate temperature of 300°C, where a specific microstructure, called a CP (chrysanthemum-like pattern) structure, is observed. The results suggest that the CP structure becomes observable in the highly segregated state and generates high perpendicular anisotropy. A new segregation growth model is derived from the results of the CP structure observations. Using this model, it is possible to explain the continuous transition of the magnetization mode between the continuous and the particulate modes.  相似文献   
6.
7.
Design of active vehicle suspension has tradeoffs between three main performance metrics (passenger comfort, suspension deflection and road holding ability). It has been known that each performance can be achieved by H controller and they can be gathered by LPV (Linear Parameter Varying) method. However, because the suspension deflection limit was not explicitly considered, this limit may be exceeded. In this paper, the authors propose a “reference shaping“ based method in order to improve the control performance. In this approach, a “virtual reference” signal is imposed to the system such that the suspension deflection is kept small. The effectiveness of the approach is examined by numerical simulations. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008  相似文献   
8.
9.
Bioactive glass-ceramics toughened by tetragonal zirconia polycrystal (TZP) were prepared by hot-pressing mixed powders of the MgO-CaO-P2O5-SiO2 glass and TZP containing 20 to 80% alumina. The bending strength and the fracture toughness of the composite materials were improved compared with those of the material without TZP. These composites showed high bending strengths (400 to 500MPa) and high fracture toughness ( 2.8MPa m1/2). The existence of a crack deflection mechanism was observed by scanning electron microscopy. After soaking in simulated physiological solution at 100 °C, no phase transformation from tetragonal to monoclinic of TZP in the composites and no degradation in bending strength occurred.  相似文献   
10.
Long chain N-acylglutamic acid was prepared in a high yield by a reaction of glutamic acid with fatty acid chloride in a mixed solvent of water and a water miscible organic solvent such as acetone, methyl ethyl ketone, dioxane, tetrahydrofuran,t-butyl alcohol or cyclohexanone. In this reaction the composition of the mixed solvent influenced the yield of N-acylated glutamic acid and the best yield was obtained when the reaction was carried out in the mixed solvent comprising 30–60% v/v of the organic solvent. Long chain N-acylaspartic acid was also obtained in a high yield by the same method. As the other method to obtain N-lauroyl-D L-glutamic acid, it was examined that N-acyl-α-aminoglutarodinitrile which was obtained by a reaction of α-aminoglutarodinitrile with fatty acid chloride was hydrolyzed with an aqueous alkaline solution. The salts of long chain N-acylglutamic acid are known as the surface active agents that react mildly on the human skin.  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