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   1532480篇
  免费   34263篇
  国内免费   10823篇
电工技术   39439篇
技术理论   2篇
综合类   12059篇
化学工业   278772篇
金属工艺   68127篇
机械仪表   45773篇
建筑科学   51692篇
矿业工程   13054篇
能源动力   52378篇
轻工业   113293篇
水利工程   16330篇
石油天然气   40907篇
武器工业   803篇
无线电   204645篇
一般工业技术   286137篇
冶金工业   141132篇
原子能技术   34673篇
自动化技术   178350篇
  2021年   18741篇
  2020年   14011篇
  2019年   16381篇
  2018年   16397篇
  2017年   16073篇
  2016年   22722篇
  2015年   20340篇
  2014年   32655篇
  2013年   92626篇
  2012年   39714篇
  2011年   51739篇
  2010年   46529篇
  2009年   55014篇
  2008年   47947篇
  2007年   44653篇
  2006年   48327篇
  2005年   41779篇
  2004年   43014篇
  2003年   42599篇
  2002年   41817篇
  2001年   38124篇
  2000年   36632篇
  1999年   35197篇
  1998年   37346篇
  1997年   35207篇
  1996年   33343篇
  1995年   29967篇
  1994年   28085篇
  1993年   27588篇
  1992年   26248篇
  1991年   23208篇
  1990年   23544篇
  1989年   22539篇
  1988年   21014篇
  1987年   19305篇
  1986年   18606篇
  1985年   21932篇
  1984年   22255篇
  1983年   20165篇
  1982年   19176篇
  1981年   19213篇
  1980年   17814篇
  1979年   18459篇
  1978年   17684篇
  1977年   17185篇
  1976年   17864篇
  1975年   15934篇
  1974年   15484篇
  1973年   15562篇
  1972年   13050篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
21.
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical...  相似文献   
22.
23.
This paper investigates PID control design for a class of planar nonlinear uncertain systems in the presence of actuator saturation. Based on the bounds on the growth rates of the nonlinear uncertain function in the system model, the system is placed in a linear differential inclusion. Each vertex system of the linear differential inclusion is a linear system subject to actuator saturation. By placing the saturated PID control into a convex hull formed by the PID controller and an auxiliary linear feedback law, we establish conditions under which an ellipsoid is contractively invariant and hence is an estimate of the domain of attraction of the equilibrium point of the closed-loop system. The equilibrium point corresponds to the desired set point for the system output. Thus, the location of the equilibrium point and the size of the domain of attraction determine, respectively, the set point that the output can achieve and the range of initial conditions from which this set point can be reached. Based on these conditions, the feasible set points can be determined and the design of the PID control law that stabilizes the nonlinear uncertain system at a feasible set point with a large domain of attraction can then be formulated and solved as a constrained optimization problem with constraints in the form of linear matrix inequalities (LMIs). Application of the proposed design to a magnetic suspension system illustrates the design process and the performance of the resulting PID control law.   相似文献   
24.
Multimedia Tools and Applications - Recently, many concepts in technology has been changed. According to the digital transformation trends, Internet of Things (IoT) represents an interested...  相似文献   
25.
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell.  相似文献   
26.
Zhao  Ziyu  Lin  Haitao  Ma  Pibo 《Applied Composite Materials》2022,29(4):1675-1694
Applied Composite Materials - In this paper, the low-velocity impact deformation behavior of biaxial warp-knitted flexible composite was investigated. A simplified finite element model (FEM) of the...  相似文献   
27.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...  相似文献   
28.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  相似文献   
29.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
30.

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.

  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